Papers - Higashibayashi, Shuhei

Development of Catalytic Reactions Using Bis(pinacolato)diboron and Their Applications to Syntheses of Pharmaceuticals and Luminescent Dyes

Shuhei Higashibayashi

Journal of Synthetic Organic Chemistry 82 ( 11 ) 1052 - 1062 2024.11

Research paper (scientific journal), Single Work, Lead author, Corresponding author, Accepted,  ISSN  00379980

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We have developed three catalytic reactions involving borylation and C—C bond formation using bis(pinacolato)diboron (B2pin2), and have extended their use to the synthesis of pharmaceuticals and luminescent dyes. In addition, we have also elucidated the photophysical properties of those dyes. The first reaction is a Cu—catalyzed stereoselective borylation of glycosyl bromide to β—glycosyl trifluoroborates, which has been further expanded to synthesize aryl β—C—glycosides via Pd—catalyzed stereospecific cross—coupling with aryl bromides. These methods were applied to the stereospecific synthesis of the SGLT2 inhibitor, canagliflozin. The second reaction involves the copper—catalyzed borylation of acyl chlorides to form acyl trifluoroborates, which have further been applied to the synthesis of fluorescent C,N—chelated 2,2—difluoro—1,4—diazaboroles via condensation with various amino—heterocycles. The third reaction is an organocatalytic pinacol coupling of aryl aldehydes using B2pin2 as a reductant and a substituted pyridine catalyst. The resulting diols were converted to various substituted benzils, revealing the luminescent properties such as phosphorescence, fluorescence, and self—recovering phosphorescence—to—phosphorescence mechanochromism. These studies demonstrated the usefulness of the developed methods for producing pharmaceuticals, pharmaceutical candidates and novel materials, as well as making possible the investigation of the products physical properties.

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Synthesis and property of 2,2-difluoro-1,4-diazaborole

Nakahara M., Wada Y., Kawano M., Hanaya K., Sugai T., Higashibayashi S.

Chemistry Letters (Chemistry Letters)  53 ( 5 ) upae069 2024.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  03667022

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The synthesis of 2,2-difluoro-1,4-diazaboroles was achieved through the condensation of aliphatic acyltrifluoroborates and amino-N-heteroarenes under acidic conditions. Various N-heteroarenes, including pyridine, pyrimidine, pyridazine, thiazole, and isoquinoline, were successfully employed in the reaction. Among the synthesized 2,2-difluoro-1,4-diazaboroles, the one with an isoquinoline structure exhibited the most intense light blue emission.

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Utilization of Lipase-Catalyzed Acetylation and Deacetylation in the Synthesis of a Natural Product with a Hydroquinone Skeleton

Sugai T., Honda K., Hashimoto R., Hanaya K., Higashibayashi S.

Asian Journal of Organic Chemistry    e202400303 2024

Research paper (scientific journal), Joint Work, Accepted

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Elaborated conditions for lipase-catalyzed preferential monoacetylation enabled the large-scale preparation of hydroquinone monoacetate. This product was then applied to the synthesis of tournefolin B, a highly oxygenated prenylated hydroquinone of plant origin (Tournefortia sarmentosa Lam.). During the course of the synthetic transformations, lipase-catalyzed deacetylation under mild conditions was demonstrated.

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Unified short syntheses of oxygenated tricyclic aromatic diterpenes by radical cyclization with a photoredox catalyst

Hashimoto R., Hanaya K., Sugai T., Higashibayashi S.

Communications Chemistry (Communications Chemistry)  6 ( 1 )  2023.12

Research paper (scientific journal), Accepted

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The biomimetic two-phase strategy employing polyene cyclization and subsequent oxidation/substitution is an effective approach for divergent syntheses of [6-6-6]-tricyclic diterpenes. However, this strategy requires lengthy sequences for syntheses of oxygenated tricyclic aromatic abietane/podocarpane diterpenes owing to the many linear oxidation/substitution steps after cyclization. Here, we present a new synthetic route based on a convergent reverse two-phase strategy employing a reverse radical cyclization approach, which enabled the unified short syntheses of four aromatic abietane/podocarpane diterpenes and the divergent short syntheses of other related diterpenes. Oxygenated and substituted precursors for cyclization were convergently prepared through Friedel-Crafts acylation and rhodium-catalyzed site-selective iodination. Radical redox cyclization using an iridium photoredox catalyst involving neophyl rearrangement furnished the thermodynamically favored 6-membered ring preferentially. (±)-5,6-Dehydrosugiol, salvinolone, crossogumerin A, and Δ5-nimbidiol were synthesized in only 8 steps. An oxygenated cyclized intermediate was also useful for divergent derivatization to sugiol, ferruginol, saprorthoquinone, cryptomeriololide, and salvinolone.

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Synthesis and luminescence properties of substituted benzils

Yasui M., Fujihara T., Ohtsu H., Wada Y., Shimada T., Zhu Y., Kawano M., Hanaya K., Sugai T., Higashibayashi S.

Communications Chemistry (Communications Chemistry)  6 ( 1 )  2023.12

Research paper (scientific journal), Accepted

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Photophysical properties of benzil (1,2-diphenylethane-1,2-dione) and its derivatives in the crystal state have recently attracted much attention. However, the study of substituted benzils has mostly been limited to para-substituted derivatives, which did not induce a significant effect on the emission wavelength compared to pristine benzil. The effects of ortho- and meta-substituents on the photophysical properties in the crystal state have not been investigated so far. Our recently developed organocatalytic pinacol coupling of substituted benzaldehydes allowed us to prepare various ortho-, meta-, and para-substituted benzil derivatives and to investigate their luminescence properties. Ortho- and meta-substituents affected the electronic states of benzils in the crystal state, resulting in differences in their luminescence properties. The luminescence wavelength and type, i.e., phosphorescence or fluorescence, were altered by these substituents. Fast self-recovering phosphorescence-to-phosphorescence mechanochromism by the para-CF3 substituent at room temperature was also discovered.

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Selective modification of tryptophan in polypeptides via C-N coupling with azoles using in situ-generated iodine-based oxidants in aqueous media

Watanabe S., Wada Y., Kawano M., Higashibayashi S., Sugai T., Hanaya K.

Chemical Communications (Chemical Communications)  59 ( 87 ) 13026 - 13029 2023.10

Research paper (scientific journal), Accepted,  ISSN  13597345

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This study demonstrates the C-N coupling of tryptophan with azoles, promoted by an in situ-generated iodine-based oxidant. The protocol was successfully applied to the selective modification of tryptophan in nonprotected polypeptide bearing oxidatively sensitive residues in acidic aqueous media. The present method allows the attachment of reactive handles to polypeptides and the peptide stapling.

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Inversion of Diaza[5]Helicenes Through an N−N Bond Breaking Pathway

Kobayashi T., Ishiwari F., Fukushima T., Nojima Y., Hasegawa M., Mazaki Y., Hanaya K., Sugai T., Higashibayashi S.

Chemistry - A European Journal (Chemistry - A European Journal)  29 ( 43 )  2023.08

Research paper (scientific journal), Accepted,  ISSN  09476539

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1,1’,10,10’-Biphenothiazine and its S,S,S’,S’-tetroxide are diaza[5]helicenes with N−N linkages. Kinetic experiments on racemization together with DFT calculations revealed that they undergo inversion through the N−N bond breaking pathway rather than the general conformational pathway. In these diaza[5]helicenes with this inversion mechanism, the reduction of electronic repulsion in the N−N bond by modification of S to SO2 at the outer position of the helix led to a significantly higher inversion barrier, 35.3 kcal/mol, compared to [5]helicene. 1,1’,10,10’-Biphenothiazine S,S,S’,S’-tetroxide was highly resistant to acid-mediated N−N bond breaking and racemization under acidic conditions.

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Transition-Metal-Free β-Selective C-Glycosylation of β-Glycosyl Boronates via Stereoretentive 1,2-Migration

Yasutomi H., Takeda D., Yoritate M., Higashibayashi S., Sugai T., Hirai G.

Synlett (Synlett)  34 ( 4 ) 347 - 352 2023.03

Research paper (scientific journal), Accepted,  ISSN  09365214

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C-Glycoside analogues of native glycans are useful molecular tools for medicinal chemistry and chemical biology due to their resistance to cellular glycoside hydrolases. We previously reported an α-selective direct C-glycosylation of 2-deoxy-β-glycosyl boronate through a Ni/photoredox-catalyzed stereoinvertive cross-coupling reaction. Here we report a complementary stereoretentive synthetic method for the preparation of β-C-glycosides from a similar boronate precursor through the addition of a C(sp2) anion followed by 1,2-migration of the glycosyl donor.

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Intramolecular cyclization of m-homoprenylphenols through oxidative nucleophilic aromatic substitution

Deguchi H., Hanaya K., Sugai T., Higashibayashi S.

Chemical Communications (Chemical Communications)  59 ( 6 ) 748 - 751 2023

Research paper (scientific journal), Accepted,  ISSN  13597345

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We developed an intramolecular cyclization of m-homoprenylphenols and related m-prenylphenols to bicyclic skeletons by hypervalent iodine reagents through an oxidative nucleophilic aromatic substitution using the prenyl group as a carbon nucleophile. The reaction was applicable for the syntheses of 5/6-, 6/6-, and 7/6-fused ring systems.

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A double-helical S,C-bridged tetraphenyl-para-phenylenediamine and its persistent radical cation

Harada K., Hasegawa C., Matsumoto T., Sugishita H., Kitamura C., Higashibayashi S., Hasegawa M., Suzuki S., Kato S.I.

Chemical Communications (Chemical Communications)  59 ( 10 ) 1301 - 1304 2023

Research paper (scientific journal), Accepted,  ISSN  13597345

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A structurally constrained, double-helical S,C-bridged tetraphenyl-para-phenylenediamine (TPPD) has been synthesized. The stable radical cation of the S,C-bridged TPPD was generated by chemical oxidation, and the electron spin was found to be delocalized over the entire π-conjugated framework. The excellent conformational stability of the neutral molecule facilitated the separation of its enantiomers.

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Single-Step N-Terminal Modification of Proteins via a Bio-Inspired Copper(II)-Mediated Aldol Reaction

Hanaya K., Yamoto K., Taguchi K., Matsumoto K., Higashibayashi S., Sugai T.

Chemistry - A European Journal (Chemistry - A European Journal)  28 ( 47 )  2022.08

Research paper (scientific journal), Accepted,  ISSN  09476539

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The chemical modification of proteins is an effective technique for manipulating the properties and functions of proteins, and for creating protein-based materials. The N-terminus is a promising target for single-site modification that provides modified proteins with uniform structures and properties. In this paper, a copper(II)-mediated aldol reaction with 2-pyridinecarboxaldehyde (2-PC) derivatives is proposed as an operationally simple method to selectively modify the N-terminus of peptides and proteins at room temperature and physiological pH. The copper(II) ion activates the N-terminal amino acids by complexation with an imine of the N-terminal amino acid and 2-PCs, realizing the selective formation of the nucleophilic intermediate at the N-terminus. This results in a stable carbon-carbon bond between the 2-PCs and the α-carbon of various N-terminal amino acids. The reaction is applied to four different proteins, including biopharmaceuticals such as filgrastim and trastuzumab. The modified trastuzumab retains the human epidermal growth factor receptor 2 recognition activity.

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One-Step Synthesis of Acylborons from Acyl Chlorides through Copper-Catalyzed Borylation with Polystyrene-Supported PPh<inf>3</inf>Ligand

Nakahara M., Kurahayashi K., Hanaya K., Sugai T., Higashibayashi S.

Organic Letters (Organic Letters)  24 ( 30 ) 5596 - 5601 2022.08

Research paper (scientific journal), Accepted,  ISSN  15237060

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We developed a one-step synthesis of acylborons from both readily available acyl chlorides and bis(pinacolato)diboron through copper(I)-catalyzed borylation. Under the reaction conditions using tBuOLi, polystyrene-supported triphenylphosphine as a copper ligand was found to promote the borylation of acyl chlorides while suppressing alcoholysis. This method enables the facile synthesis of potassium acyltrifluoroborates.

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Synthesis of 1H-2-Benzopyran-5,8-dione Skeleton through a Cascade Reaction between Benzoquinone and β-Ketoester

Nakahara M., Ohtsu H., Kawano M., Hanaya K., Sugai T., Higashibayashi S.

Chemistry Letters (Chemistry Letters)  51 ( 4 ) 356 - 359 2022.04

Research paper (scientific journal), Accepted,  ISSN  03667022

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The 1H-2-benzopyran-5,8-dione structure was synthesized by a cascade reaction through Michael addition, elimination of HBr, and O-alkylation between a dibromobenzoquinone derivative and β-ketoesters under basic conditions. The reaction using potassium carbonate and 18-crown-6 in THF was the best condition, giving 1H-2-benzopyran-5,8-dione derivatives in good yields. The UV-vis absorption spectrum and cyclic voltammogram of the synthesized 1H-2-benzopyran-5,8-dione derivative were measured, clarifying the photophysical and redox properties.

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1,2-Rearrangement from o-Quinols to Multisubstituted Catechols via Retro Diels-Alder Reaction of o-Quinol Dimers

Hashimoto R., Hanaya K., Sugai T., Higashibayashi S.

Bulletin of the Chemical Society of Japan (Bulletin of the Chemical Society of Japan)  95 ( 4 ) 663 - 672 2022

Research paper (scientific journal), Accepted,  ISSN  00092673

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The 1,2-rearrangement of o-quinols has been a long-standing unsolved problem since 1958. Although the rearrangement is expected to be useful for syntheses of catechol derivatives, it is hampered by many competing reactions and has not been developed as a useful methodology. Here, we succeeded in settling this problem by a first systematic thorough investigation, establishing the 1,2-rearrangement as a cascade reaction with a retro Diels-Alder reaction from o-quinol dimers. This is a useful strategy for syntheses of substituted catechols used as synthetic building blocks for bioactive compounds and material molecules. o-Quinol dimers were synthesized by improved oxidative hydroxylation of substituted phenols followed by spontaneous Diels-Alder reaction. The dimers then underwent the retro Diels-Alder reaction to regenerate the o-quinols followed by 1,2-rearrangement under neutral heating conditions at an appropriate temperature depending on the migratory substituent, furnishing substituted catechols in good yields. The competing reactions such as an elimination of a substituent or α-ketol rearrangement were minimized by controlling the reaction temperature.

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Copper-Catalyzed Stereoselective Borylation and Palladium-Catalyzed Stereospecific Cross-Coupling to Give Aryl C-Glycosides

Kurahayashi K., Hanaya K., Sugai T., Hirai G., Higashibayashi S.

Chemistry - A European Journal (Chemistry - A European Journal)  29 ( 6 )  2022

Research paper (scientific journal), Accepted,  ISSN  09476539

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Metabolically stable C-glycosides are an essential family of compounds in bioactive natural products, therapeutic agents, and biological probes. For their application, development of synthetic methods by connecting glycosides and aglycons with strict stereocontrol at the anomeric carbon, as well as with high functional-group compatibility and environmental compatibility is a pivotal issue. Although Suzuki–Miyaura-type C(sp3)−C(sp2) cross-coupling using glycosyl boronates is a potential candidate for the construction of C-glycosides, neither the cross-coupling itself nor the facile synthesis of the coupling precursor, glycosyl boronates, have been achieved to date. Herein, it was succeeded to develop a copper-catalyzed stereoselective one-step borylation of glycosyl bromides to glycosyl boronates and palladium-catalyzed stereospecific cross-coupling of β-glycosyl borates with aryl bromides to give aryl β-C-glycosides, in which the β-configuration of the anomeric carbon of the glycosyl trifluoroborates is stereoretentively transferred to that of the resulting aryl C-glycosides.

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Chemoselectivity-independent Cu-mediated coupling to construct the hydroquinoline skeleton of symbioimine

Fujita R., Hanaya K., Sugai T., Higashibayashi S.

Scientific Reports (Scientific Reports)  11 ( 1 )  2021.12

Research paper (scientific journal), Accepted

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Construction of the hydroquinoline skeleton of symbioimine by Cu-mediated N-alkenylation or O-alkenylation of an allyl aminoalcohol, in which either chemoselectivity could lead to the target compound, was investigated. O-alkenylation followed by Claisen rearrangement was favored with high selectivity under a ligand-free condition. Subsequent intramolecular condensation furnished the hydroquinoline skeleton of symbioimine.

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Metal-free thermal organocatalytic pinacol coupling of arylaldehydes using an isonicotinate catalyst with bis(pinacolato)diboron

Yasui M., Hanaya K., Sugai T., Higashibayashi S.

RSC Advances (RSC Advances)  11 ( 40 ) 24652 - 24655 2021.07

Research paper (scientific journal), Accepted

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The metal-free thermal organocatalytic pinacol coupling of arylaldehydes has been developed. The intermolecular coupling of arylaldehydes catalyzed byt-butyl isonicotinate with bis(pinacolato)diboron as the co-reducing agent afforded 1,2-diphenylethane-1,2-diols. This reaction was also applicable to the intramolecular coupling of 1,1′-biphenyl-2,2′-dicarbaldehydes to afford 9,10-dihydrophenanthrene-9,10-diols. Various functional groups were tolerated under this coupling condition.

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Single-molecule electric switching induced by acid-base reaction

Yoshihara Y., Fujii S., Higashibayashi S., Kiguchi M., Nishino T.

Chemistry Letters (Chemistry Letters)  50 ( 6 ) 1271 - 1273 2021.06

Research paper (scientific journal), Accepted,  ISSN  03667022

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Electric switches are one of the most fundamental electric circuitries. Recent developments in single-molecule techniques allow us to study various electric-switching phenomena on the single-molecule scale. In this study, the switch of the current through a single molecule of a biphenothiazine derivative was investigated using the break junction technique. The biphenothiazine derivative undergoes acid-base reaction-induced electronic modulation due to the reversible structural transformation between a closed shell and an open shell, resulting in a change in the electronic gap and effective tunneling barrier height. We succeeded in controlling the single-molecule electric conductivity of the biphenothiazine derivative wired to two Au electrodes by allowing the reaction to proceed reversibly on the electrode.

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Chemoenzymatic semisynthesis of caffeic acid β-phenethyl ester, an antioxidative component in propolis, from raw coffee bean extract

Hashimoto R., Iai H., Fujita R., Hanaya K., Higashibayashi S., Inoue H., Sugai T.

Bioscience, biotechnology, and biochemistry 85 ( 3 ) 476 - 480 2021.02

Research paper (scientific journal), Joint Work, Accepted

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© The Author(s) 2020. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry. Caffeic acid β-phenethyl ester (CAPE), an antioxidative bioactive catechol isolated from propolis, was semisynthesized from chlorogenic acid and related compounds in an extract of raw (unroasted) Robusta coffee (Coffea canephora) beans in 5 steps and a total yield of 31%. Oxidative degradation of the intermediates and target molecule was prevented by alkaline hydrolysis of the chlorogenic acids in the presence of sodium dithionite (Na2S2O4) and deprotection of the catecholic diacetate precursor by Candida antarctica lipase B-mediated transesterification as the final step.

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Analysis of Interconversion between Atropisomers of Chiral Substituted 9,9’-Bicarbazole

Kobayashi T., Ishiwari F., Fukushima T., Hanaya K., Sugai T., Higashibayashi S.

European Journal of Organic Chemistry 2021 ( 3 ) 449 - 451 2021.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1434193X

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© 2020 Wiley-VCH GmbH Interconversion of atropisomers of chiral 3,3’-di-tert-butyl-9,9’-bicarbazole linked by a single N−N bond was analyzed by DFT calculations and experiments. The calculations revealed that the trans transition state has a lower energy for the interconversion than the cis transition state. The lowest transition state of interconversion between natural dixiamycins A and B containing a 9,9’-bicarbazole structure was found to be the trans transition state. The calculations also indicated that degradation through N−N bond cleavage was faster than racemization. Atropisomeric enantiomers of 3,3’-di-tert-butyl-9,9’-bicarbazole were resolved by chiral HPLC for the first time, and then racemization and N−N bond cleavage were investigated by heating experiments, showing that racemization did not take place below the degradation temperature.

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Semisynthesis of prunetin, a bioactive O-methylated isoflavone from naringenin, by the sequential deacetylation of chalcone intermediates and oxidative rearrangement

Sugai T., Hanaya K., Higashibayashi S.

Bioscience, biotechnology, and biochemistry 85 ( 1 ) 143 - 147 2021.01

Research paper (scientific journal), Joint Work, Accepted

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© The Author(s) 2021. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry. Prunetin (4',5-dihydroxy-7-methoxyisoflavone) was semisynthesized in 8 steps from readily available naringenin in 26% total yield. The key reaction was chemoenzymatic sequential deacetylation to 6'-acetoxy-2',4″-dihydroxy-4'-methoxychalcone, the in situ-formed precursor for thallium(III) nitrate-mediated oxidative rearrangement.

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A Concise Total Synthesis of Dehydroantofine and Its Antimalarial Activity against Chloroquine-Resistant Plasmodium falciparum

Yamasaki N., Iwasaki I., Sakumi K., Hokari R., Ishiyama A., Iwatsuki M., Nakahara M., Higashibayashi S., Sugai T., Imagawa H., Kubo M., Fukuyama Y., Ōmura S., Yamamoto H.

Chemistry - A European Journal 27   5555 - 5563 2021

Research paper (scientific journal), Joint Work, Accepted,  ISSN  09476539

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© 2021 Wiley-VCH GmbH The total synthesis of dehydroantofine was achieved by employing a novel, regioselective, azahetero Diels–Alder reaction of easily accessible 3,5-dichloro-2H-1,4-oxazin-2-one with 14 a as a key step. Furthermore, it is demonstrated that dehydroantofine is a promising candidate as a new antimalarial agent in a biological assay with chloroquine-resistant Plasmodium falciparum.

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Nickel(II)-Mediated C−S Cross-Coupling Between Thiols and ortho-Substituted Arylboronic Acid

Hanaya K., Ohtsu H., Kawano M., Higashibayashi S., Sugai T.

Asian Journal of Organic Chemistry 10 ( 3 ) 582 - 587 2021

Research paper (scientific journal), Joint Work, Accepted,  ISSN  21935807

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© 2020 Wiley-VCH GmbH Herein, we report a C−S cross-coupling reaction between alkyl thiols or aryl thiols and ortho-substituted arylboronic acids that proceeds in the presence of an inexpensive and ligand-free NiCl2 ⋅ 6H2O salt and N-methylmorpholine, a weak base, at 25 °C in air. The presence of coordinating and electron-withdrawing groups at the ortho-position of the arylboronic acids played a crucial role in determining the efficiency of the reaction. X-ray crystallographic analysis revealed that the [NiCl2(DMF)2(H2O)2] complex was formed in-situ. The complex is an excellent precursor of the active nickel species. The reaction offers an extremely mild and operationally convenient method to access a wide variety of alkyl aryl sulfides and diaryl sulfides without using expensive transition metals, such as palladium, gold, and rhodium, and specialized and expensive ligands.

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Theoretical Analysis of the Heterocyclic [4+2] Cycloaddition Between Pyridinium Ion and Enol Ether

Nakahara M., Hanaya K., Sugai T., Higashibayashi S.

ChemistryOpen  2021

Research paper (scientific journal), Joint Work, Accepted

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© 2021 The Authors. Published by Wiley-VCH GmbH Dearomative heterocyclic [4+2] cycloaddition between the N-(2,4-dinitrophenyl)pyridinium ion of nicotinamide and an enol ether was analyzed by Density Functional Theory (DFT) calculations. The calculation revealed that the reaction undergoes stepwise bond formation rather than occurring in a concerted manner. The experimental products were found to be both kinetically and thermodynamically favored. The calculated transition states and intermediate suggested that the high diastereoselectivity is derived from the electrostatic interaction between the 2-nitro group of the pyridinium ion and the hydrogen of the enol ether.

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Improved preparation of vitexin from hot water extract of Basella alba, the commercially available vegetable Malabar spinach (“Tsurumurasaki” in Japanese) and the application to semisynthesis of chafuroside B

Kurahayashi K., Hanaya K., Higashibayashi S., Sugai T.

Bioscience, Biotechnology and Biochemistry 84 ( 8 ) 1554 - 1559 2020.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  09168451

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© 2020, © 2020 Japan Society for Bioscience, Biotechnology, and Agrochemistry. Hot water extraction of D-arabinofuranosylvitexin from the raw leaves of commercially available Basella alba “Tsurumurasaki” and subsequent acidic hydrolysis was improved to be a procedure using a high-pressure steam sterilizer to afford vitexin. The amount was estimated to be 14.1 mg from 1 g of dry weight of the raw leaves, whose recovery was calculated to be 95% based on the estimated content of D-arabinofuranosylvitexin in B. alba raw leaves. The product was dehydratively cyclized between hydroxy groups on the carbohydrate and flavone skeletons under modified Mitsunobu reaction conditions in N,N-dimethylformamide to give chafuroside B, which is known to be a bioactive Oolong tea polyphenol. Through these transformations, 10.2 mg of chafuroside B could be semisynthesized from 1 g of dry weight of the raw leaves, and the efficiency was improved compared to that from the extraction from Oolong tea (3.4 μg from 1 g of dry weight).

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Comprehensive semisyntheses of catathelasmols C, D, and E from D-glutamic acid, utilizing lipase-catalyzed site-selective reactions on intermediates

Hashiba R., Hashimoto R., Nishiguchi M., Kobayashi T., Hanaya K., Higashibayashi S., Sugai T.

Bioscience, Biotechnology and Biochemistry 84 ( 7 ) 1339 - 1344 2020.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  09168451

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© 2020, © 2020 Japan Society for Bioscience, Biotechnology, and Agrochemistry. Catathelasmols C, D, and E, which had been isolated from Catathelasma imperiale as inhibitors for 11-hydroxysteroid dehydrogenases, were comprehensively semisynthesized from commercially available D-glutamic acid. The key synthetic intermediate, (R)-pentane-1,2,5-triol, was site-selectively acetylated by treatment with vinyl acetate and Candida antarctica lipase B (Novozym 435) in tetrahydrofuran (THF) at 25°C to furnish 1,5-diacetate (catathelasmol E, quantitative). The acetylation occurred site-selectively on the primary alcohols at the C-1 and C-5 positions over the secondary alcohol at the C-2 position. Dichromic acid oxidation provided 2-oxopentane-1,5-diyl diacetate (catathelasmol C, 78%). Burkholderia cepacia lipase-catalyzed transesterification with methanol in THF at–5°C proceeded preferentially on the acetate at C-1 located adjacent to the C-2 carbonyl group over the other terminal acetate at the C-5 position. 5-Hydroxy-4-oxopentyl acetate (catathelasmol D) was obtained in 53% yield.

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Stepwise approach for sterically hindered Csp3-Csp3 bond formation by dehydrogenative: O -alkylation and Lewis acid-catalyzed [1,3]-rearrangement towards the arylalkylcyclopentane skeleton of sesquiterpenes

Fujitani B., Hanaya K., Sugai T., Higashibayashi S.

Chemical Communications 56 ( 25 ) 3621 - 3624 2020.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  13597345

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This journal is © The Royal Society of Chemistry. A stepwise dehydrogenative cross-coupling method was developed for the formation of sterically hindered Csp3-Csp3 bonds. Intramolecular dehydrogenative O-alkylation of a β-ketoester by 2,3-dichloro-5,6-dicyano-p-benzoquinone to form an oxolane followed by Lewis acid-catalyzed [1,3]-rearrangement furnished the sesquiterpene arylmethylcyclopentane skeleton. The formal syntheses of herbertane-type β-herbertenol, cuparane-type enokipodins A and B were also achieved.

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Syntheses of indirubins by aldol condensation of isatins with indoxyl anion generated in situ by lipase-catalyzed deacetylation of indoxyl acetate

Sugai T., Hanaya K., Higashibayashi S.

Heterocycles 100 ( 1 ) 129 - 136 2020

Research paper (scientific journal), Joint Work, Accepted,  ISSN  03855414

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© 2020 The Japan Institute of Heterocyclic Chemistry. The syntheses of indirubin (76% yield), 6-bromoindirubin (82% yield), and 6-bromoindirubin-3′-oxime (78% yield in two steps) were achieved via the lipase-triggered aldol condensation between isatins and an indoxyl anion in tetrahydrofuran under anhydrous and anaerobic conditions as the key step. The aldol donor was generated in situ by Burkholderia cepacia lipase (Amano PS-IM)-catalyzed deacetylation of commercially available and stable indoxyl acetate in the presence of triethylamine and with 2-propanol as the transesterification reagent. The scale-up of the presently developed reactions is easier than that in the previously reported chemical aldol condensations, because of the simplicity of the isolation procedure and suppression of the oxidative byproduct formation from indoxyl acetate.

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Synthesis of 5-Hydroxy-3′,4′,7-trimethoxyflavone and Related Compounds and Elucidation of Their Reversal Effects on BCRP/ABCG2-Mediated Anticancer Drug Resistance

Tsunekawa R., Katayama K., Hanaya K., Higashibayashi S., Sugimoto Y., Sugai T.

ChemBioChem 20 ( 2 ) 210 - 220 2019.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  14394227

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© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 3′,4′,7-Trimethoxyflavone (TMF) has been reported to show a potent reversal effect on drug resistance mediated by breast cancer resistance protein (BCRP)/ATP-binding cassette subfamily G member 2 (ABCG2). In this study, we designed and synthesized five derivatives with either a hydroxy group or a fluorine atom at C-5 and several kinds of capping moiety at the C-7 hydroxy group, on the same 3′,4′-dimethoxy-substituted flavone skeleton. We subsequently evaluated the efficacies of these compounds against BCRP-expressing human leukaemia K562/BCRP cells. Reversal of drug resistance was expressed as the concentration of compound causing a twofold reduction in drug sensitivity (RI 50 ). Of the synthesized compounds, the reversal effect of 5-hydroxy-3′,4′,7-trimethoxyflavone (HTMF, RI 50 7.2 nm) towards 7-ethyl-10-hydroxycamptothecin (SN-38) was stronger than that of TMF (RI 50 18 nm). Fluoro-substituted 5-fluoro-3′,4′,7-trimethoxyflavone (FTMF, RI 50 25 nm) and monoglycosylated 7-(β-glucosyloxy)-5-hydroxy-3′,4′-dimethoxyflavone (GOHDMF, 91 nm) also exhibited reversal effects, whereas the di- and triglycoside derivatives did not. TMF, HTMF and FTMF at 0.01–10 μm upregulated the K562/BCRP cellular accumulation of Hoechst 33342 nuclear staining dye. In addition, western blotting revealed that treatment of K562/BCRP cells with 0.1 μm TMF, HTMF or FTMT suppressed the expression of BCRP. HTMF showed the strongest inhibition of BCRP-mediated efflux and suppression of BCRP expression of the three effective synthesized flavones.

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Site-selective synthesis of acacetin and genkwanin through lipase-catalyzed deacetylation of apigenin 5,7-diacetate and subsequent methylation

Fujita R., Mandal S., Hanaya K., Shoji M., Higashibayashi S., Sugai T.

Heterocycles 99 ( 1 ) 638 - 648 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  03855414

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© 2019 The Japan Institute of Heterocyclic Chemistry. Candida antarctica lipase B-catalyzed deacetylation proceeded with high site-selectivity on the C-4′ acetyl group in apigenin triacetate to give apigenin 5,7-diacetate. Methylation of the liberated hydroxy group with the combination of trimethyloxonium tetrafluoroborate (Meerwein reagent) and 1,8-bis(dimethylamino)naphthalene (proton sponge) in CH2Cl2 proceeded in a quantitative manner to give the product methylated at the C-4′ hydroxy group (acacetin 5,7-diacetate). Even with the same precursor, a different methylation product at the C-7 hydroxy group (genkwanin 4′,5-diacetate) was obtained in 86% yield by applying iodomethane and Cs2CO3 in dimethyl sulfoxide (DMSO). The methylated products were deprotected to form acacetin and genkwanin. We inferred that the latter unexpected methylation was ascribable to the intermolecular migration of an acetyl group from C-7 to C-4′. DFT calculations indicated that the C-7 phenoxide ion was 12.6 kJ/mol more stable than the initially formed C-4′ phenoxide ion.

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Lipase-catalyzed site-selective deacetylation of sterically hindered naphthohydroquinone diacetate and its application to the synthesis of a heterocyclic natural product

Hashimoto R., Sakakura A., Hanaya K., Higashibayashi S., Sugai T.

Heterocycles (Heterocycles)  99 ( 1 ) 625 - 632 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  03855414

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© 2019 The Japan Institute of Heterocyclic Chemistry. Lipase-catalyzed site-selective deacetylation of 2,5-dimethylnaphthalene-l,4-diol diacetate was examined. With Candida antarctica lipase B, the suppressing effect of a methyl substituent at the peri-position of the a-naphthyl ester over that at the ortho-position was significant. This site-selectivity was in contrast to that of chemical hydrolysis reported to date. From the resulting monoacetate, mansonone F, a physiologically active heterocyclic orthoquinone, was synthesized in 38% yield in as few as three steps.

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Chemoenzymatic synthesis of hydroxytyrosol monoesters and their suppression effect on nitric oxide production stimulated by lipopolysaccharides

Sakakura A., Pauze M., Namiki A., Funakoshi-Tago M., Tamura H., Hanaya K., Higashibayashi S., Sugai T.

Bioscience, Biotechnology and Biochemistry 83 ( 2 ) 185 - 191 2019

Research paper (scientific journal), Joint Work, Accepted,  ISSN  09168451

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© 2018 Japan Society for Bioscience, Biotechnology, and Agrochemistry. Fatty acid monoesters of hydroxytyrosol [2-(3,4-dihydroxyphenyl)ethanol] were synthesized in two steps from tyrosol (4-hydroxyphenylethanol) by successive Candida antarctica lipase B-catalyzed chemoselective acylation on the primary aliphatic hydroxy group over phenolic hydroxy group in tyrosol, and 2-iodoxybenzoic acid (IBX)-mediated hydroxylation adjacent to the remaining free phenolic hydroxy group. Examination of their suppression effects on nitric oxide production stimulated by lipopolysaccharides in RAW264.7 cells showed that hydroxytyrosol butyrate exhibited the highest inhibition (IC 50 7.0 μM) among the tested compounds.

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Dearomative Oxidative Rearrangement of [3]Cyclo-1,8-carbazolylene

Yasui, Masamichi, Ohtsu, Hiroyoshi, Kawano, Masaki, Hanaya, Kengo, Sugai, Takeshi, Higashibayashi, Shuhei

CHEMISTRY LETTERS 47 ( 11 ) 1357 - 1359 2018.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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© 2018 The Chemical Society of Japan. [3]Cyclo-1,8-carbazolylene was found to undergo oxidative rearrangement by oxidation with 2,3-dichloro-5,6-dicyano-pbenzoquinone, giving a 9a-substituted carbazol-1-one derivative. This is the first example of a dearomative oxidative rearrangement of a carbazole or aniline derivative. The geometrical and electronic structures were elucidated by X-ray analysis, UV-vis absorption spectroscopy, and DFT calculations.

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Synthesis and Properties of Hydrazine-Embedded Biphenothiazines and Application of Hydrazine-Embedded Heterocyclic Compounds to Fluorescence Cell Imaging

Shindo, Yuri, Nomura, Shogo, Saikawa, Yoko, Nakata, Masaya, Tanaka, Katsunori, Hanaya, Kengo, Sugai, Takeshi, Higashibayashi, Shuhei

ASIAN JOURNAL OF ORGANIC CHEMISTRY 7 ( 9 ) 1797 - 1801 2018.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2193-5807

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© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Hydrazine-embedded unsubstituted butterfly-shaped biphenothiazine and its sulfoxides were synthesized by dimerization of 1,9-dibromophenothiazine, which was prepared by realizing selective debromination at the 3,7-positions of 1,3,7,9-tetrabromophenothiazine. cis/trans-Biphenothiazine sulfoxide was selectively prepared by changing the oxidation temperature to control the inversion rate of the butterfly shape of the intermediate. Their butterfly-shapes, conformations, photophysical properties (UV-vis absorption, fluorescence), and redox properties were elucidated by X-ray analysis, DFT calculations, spectral and electrochemical measurements. Fluorescent hydrazine-embedded biphenothiazine sulfoxides and bicarbazoles were applied to cell imaging of HeLa cells. The bicarbazoles exhibited high fluorescence signals in the cells with low toxicity.

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Molecular Arrangements of Corannulene and Sumanene in Single-Walled Carbon Nanotubes

Iizumi, Yoko, Liu, Zheng, Suenaga, Kazu, Okada, Susumu, Higashibayashi, Shuhei, Sakurai, Hidehiro, Okazaki, Toshiya

CHEMNANOMAT 4 ( 6 ) 557 - 561 2018.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2199-692X

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© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Molecular arrangements of bowl-shaped molecules, corannulene and sumanene, in single-walled carbon nanotubes (SWCNTs) were investigated using high-resolution transmission microscopy and near-infrared photoluminescence spectroscopy. The results indicated that corannulenes are nested in SWCNTs with a random orientation, whereas sumanenes form stacked structures. The trends are consistent with the molecular orientations of corannulene and sumanene in single crystals.

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Triazasumanene: An Isoelectronic Heteroanalogue of Sumanene

Tan, Qitao, Kaewmati, Patcharin, Higashibayashi, Shuhei, Kawano, Masaki, Yakiyama, Yumi, Sakurai, Hidehiro

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 91 ( 4 ) 531 - 537 2018.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0009-2673

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© 2018 The Chemical Society of Japan. Buckybowls, which are represented by sumanene and corannulene, have attracted considerable attention for their unique bowl structures and interesting physicochemical properties. However, still few heteroatom-doped buckybowls have been reported to date. Here we show the successful synthesis of triazasumanene, an isoelectronic heteroanalogue of sumanene, which possesses a deeper bowl with stable bowl chirality and unique helical columnar packing in the crystal as an enantiopure form. In contrast, the crystal packing of the racemate shows a unidirectional columnar structure, which resembles that of the pristine sumanene. Doping of nitrogen atoms into the periphery of the sumanene framework also leads to perturbations of the electronic structure as shown by a significant decrease of the lowest unoccupied molecular orbital (LUMO) level and the optical band gap in comparison to all-carbon sumanene. The pyridine ring of triazasumanene shows unusual susceptibility towards acidic hydrolysis due to the highly strained curved structure.

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Formal total synthesis of (−)-hamigeran B from a chemo-enzymatically prepared building block with quaternary chiral center

Kuwata K., Fujita R., Hanaya K., Higashibayashi S., Sugai T.

TETRAHEDRON 74 ( 7 ) 740 - 745 2018.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00404020

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© 2017 Elsevier Ltd A formal total synthesis of (−)-hamigeran B was achieved in 17 steps from commercially available ethyl 2-oxocyclopentanecarboxylate. Carbonyl reductase-catalyzed asymmetric reduction and the subsequent chemical transformations furnished an enantiomerically pure synthetic intermediate, (R)-5-formyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate. Suzuki-Miyaura coupling with Gao's arylboronate [2-(2-formyl-3-methoxy-5-methylphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane], under PdCl2(dppf)•CH2Cl2 catalysis, and the subsequent cyclization by way of intramolecular reductive SmI2-mediated 1,2-diol formation provided a tricyclic skeleton with a tetrasubstituted double bond between C-1 and C-9b. Upon hydrogenation of this double bond, the proper stereochemistry of the remaining chiral centers was established. Exclusive addition of the hydrogen atom from the β-face occurred, owing to the shielding of the α-face with a bulky TBS protective group on the C-4 alcohol. The hydrogenation products were transformed into Clive's synthetic precursor for (−)-hamigeran B.

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Chemoenzymatic approaches to the synthesis of the (1S,2R)-isomer of benzyl 2-hydroxycyclohexanecarboxylate

Ryuji Tsunekawa, Kengo Hanaya, Shuhei Higashibayashi, Mitsuru Shoji, Takeshi Sugai

MOLECULAR CATALYSIS 444   84 - 89 2018.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2468-8231

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© 2017 Elsevier B.V. We examined ten strains of cultured whole-cell yeasts for the asymmetric reduction of commercially available ethyl 2-oxocyclohexanecarboxylate, and found that the (1S,2S)-stereoisomer of ethyl 2-hydroxycyclohexanecarboxylate was the major stereoisomer produced by Williopsis californica JCM 3600. The ethyl group of the ester was then substituted with a benzyl group with low volatility and increased hydrophobicity to facilitate the isolation of the expected product. Incubation with W. californica furnished benzyl (1S,2S)-2-hydroxycyclohexanecarboxylate (>99.9% ee) in 51.0% yield together with its (1R,2S)-isomer (>99.9% ee) in 35.4% yield. Upon treatment of the same substrate bearing the benzyl ester with a screening kit of purified overexpressed carbonyl reductases (Daicel Chiralscreen® OH), two enzymes (E031, E078) furnished the (1R,2S)-isomer as the major product. With another enzyme (E007), the (1S,2R)-isomer was obtained, but its ee was very low (25.6%). The highly enantiomerically enriched (1S,2S)-isomer obtained by W. californica was transformed to the (1S,2R)-isomer (>99.9% ee), whose availability until now has been low, in 43.3% yield over two steps involving tosylation and subsequent inversive attack with tetrabutylammonium nitrite.

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Application of Hydrazine-Embedded Heterocyclic Compounds to High Voltage Rechargeable Lithium Organic Batteries

Takeshi Shimizu, Koji Yamamoto, Palash Pandit, Hirofumi Yoshikawa, Shuhei Higashibayashi

SCIENTIFIC REPORTS 8 ( 1 ) 6417 - 6422 2018.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2045-2322

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© 2018 The Author(s). Hydrazine-embedded heterocyclic compounds with dimeric dimethylacridine (1b), carbazole (2b), and phenothiazine (3b) skeletons were applied to cathode active materials of rechargeable lithium organic batteries, and the performance of the batteries was evaluated. The charge/discharge curves exhibited clear plateaus in the high voltage range of 3.3-3.7 V. The capacities of the plateau regions were comparable to the calculated capacities corresponding to the one-electron redox of the molecules. The amount of the active compound 3b could be increased up to 30 wt% in the electrode composite, and fast charge/discharge performance was also observed.

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Synthesis of trilobatin from naringin via prunin as the key intermediate: acidic hydrolysis of the -rhamnosidic linkage in naringin under improved conditions

Kurahayashi, Kazuki, Hanaya, Kengo, Higashibayashi, Shuhei, Sugai, Takeshi

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 82 ( 9 ) 1463 - 1467 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0916-8451

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© 2018 Japan Society for Bioscience, Biotechnology, and Agrochemistry Trilobatin [4-(β-D-glucopyranosyloxy)-2,4”,6-trihydroxydihydrochalcone] was synthesized from commercially available naringin in three steps with an overall yield of 30%. The key step was the acid-catalyzed site-selective hydrolysis of terminal α-rhamnopyranosidic linkage in neohesperidose involved in naringin under controlled conditions, by applying a high-pressure steam sterilizer.

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Synthesis of flake-shaped [3]cyclo-4,6-benzofuranylene

Shuhei Higashibayashi

CHEMISTRY LETTERS 47 ( 1 ) 95 - 96 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  03667022

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© 2018 The Chemical Society of Japan. The cyclic trimer of dibenzofuran linked at the 4,6-positions, named [3]cyclo-4,6-dibenzofuranylene, was synthesized by Ni(0)-mediated reductive coupling of 4,6-dibromodibenzofuran. DFT calculation indicated that the flake-shaped C2 symmetric structure is the most stable conformer and the propeller-shaped D3 symmetric structure is the minor conformer with a higher energy (+19.1 kcal mol-1). The calculated inversion energy of the C2 conformer through a Cs symmetric transition state was +4.1 kcal mol-1, showing rapid fluctuation, which is consistent with the observation of only one set of 1HNMR signals of dibenzofuran of [3]cyclo-4,6-dibenzofuranylene.

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Tris(2-hydroxyphenyl)triazasumanene: bowlshaped excited-state intramolecular proton transfer (ESIPT) fluorophore coupled with aggregation-induced enhanced emission (AIEE)

Patcharin Kaewmati, Yumi Yakiyama, Hiroyoshi Ohtsu, Masaki Kawano, Setsiri Haesuwannakij, Shuhei Higashibayashi, Hidehiro Sakurai

MATERIALS CHEMISTRY FRONTIERS 2 ( 3 ) 514 - 519 2018

Research paper (scientific journal), Joint Work, Accepted

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© 2018 Royal Society of Chemistry. All rights reserved. Tris(2-hydroxyphenyl)triazasumanene ((A)-(+)-1), a bowl-shaped molecule, which possesses 2-(20-hydroxyphenyl)pyridine moieties, was successfully synthesised. (A)-(+)-1 showed a single peak emission in CH2Cl2, which overlapped with the emission of the triazasumanene skeleton and diminished at a high concentration, corresponding to the formation of the excited enol form. In contrast, single crystals of (A)-(+)-1 exhibited a dual emission with a large Stokes shift, indicating the presence of the excited keto form by the excited state intramolecular proton transfer (ESIPT) process. In the solution of (A)-(+)-1 containing a mixture of a large amount of a poor solvent (hexane or MeOH) and a small amount of CH2Cl2, colloidal aggregates emerged with the continuous increment of emission intensity by further addition of the poor solvent, demonstrating aggregation-induced enhanced emission (AIEE). The analysis of the morphology and the structure of the aggregates using a scanning electron microscope (SEM) and powder X-ray diffraction (PXRD) revealed the well-ordered structure of the aggregates, which possessed a molecular packing pattern similar to that of an (A)-(+)-1 single crystal.

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Synthesis of fisetin and 2,4,6-trihydroxydihyrochalcone 4-O--neohesperidoside based on site-selective deacetylation and deoxygenation

Tsunekawa, Ryuji, Hanaya, Kengo, Higashibayashi, Shuhei, Sugai, Takeshi

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 82 ( 8 ) 1316 - 1322 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0916-8451

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© 2018 Japan society for Bioscience, Biotechnology, and Agrochemistry. Fisetin and 2′,4′,6′-trihydroxydihyrochalcone 4′-O-β-neohesperidoside were synthesized from commercially available quercetin and naringin in five steps. The key steps are site-selective deacetylation and subsequent deoxygenation. The target molecules were obtained in 37% and 23% yields from the starting materials, respectively.

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Synthesis of oroxylin A starting from naturally abundant baicalin

Fujita, Rie, Hanaya, Kengo, Higashibayashi, Shuhei, Sugai, Takeshi

HETEROCYCLES 97 ( 2 ) 1165 - 1174 2018

Research paper (scientific journal), Joint Work, Accepted,  ISSN  03855414

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© 2018 The Japan Institute of Heterocyclic Chemistry – A new approach to oroxylin A, a monomethylated trihydroxyflavone, is described. The starting material was baicalin, a representative naturally abundant flavonoid glucuronide. First, conditions for the cleavage of the glycosidic bond were established, using a mixture of water and conc. sulfuric acid (5:2) at 121 °C for 40 min. The hydrolysis was performed in a high-pressure steam sterilizer so that the temperature and reaction time were precisely controlled. Subsequent acetylation of the crude material furnished baicalein 6,7-diacetate on a preparative scale and in a reproducible manner. Next, the C-7 position was protected site-selectively with a methoxymethyl (MOM) group, taking advantage of an unexpected sequential migration of the two acetyl groups among the C-5, C-6, and C-7 positions under basic conditions. The removal of the two remaining acetyl groups followed by site-selective methylation of the C-6 position furnished 5-hydroxy-6-methoxy-7-methoxymethoxyflavone (oroxylin A C-7 MOM ether). Finally, by the deprotection of the MOM ether, oroxylin A was obtained in 6 total steps and 62% overall yield from baicalin.

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Synthesis of 3β-tert-Butyldimethylsiloxy-22-phenylthio-23,24-bisnorchola-5,9(11)-diene and Reductive Nucleophilic Attack on a Branched Aliphatic Aldehyde

Nagai T., Hanaya K., Higashibayashi S., Shoji M., Sugai T.

Chemical and Pharmaceutical Bulletin 66 ( 3 ) 334 - 338 2018

Research paper (scientific journal), Accepted,  ISSN  00092363

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3β-tert-Butyldimethylsiloxy-22-phenylthio-23,24-bisnorchola-5,9(11)-diene, which has a double bond between C-9 and C-11 and a phenylsulfenyl group on the terminus of the side chain, is a potential synthetic intermediate for steroids with 9,11-unsaturation or 9,11-seco skeletons. We describe here the synthesis of the title compound from 17-ethylenedioxy-3-acetoxyandrosta-3,5-dien-11-one. The introduction of an ethylene unit to 3β-tert-butyldimethylsiloxyandrosta-5,9(11)-dien-17-one by the action of ethyltriphenylphosphonium bromide under basic conditions resulted in an inseparable mixture of two stereoisomeric products (5 : 1). However, in the subsequent step, only the (Z)-isomer was susceptible to the Lewis acid-catalyzed ene reaction with formaldehyde, giving a stereochemically pure product with the desired configuration. Within three steps, the ene-product was derivatized to the title compound, with a total yield of 53% over seven steps. Reductive terminal anion formation by treatment with lithium di-tert-butylbiphenyl (LiDBB) and subsequent nucleophilic attack on a branched aliphatic aldehyde was demonstrated, with an eye toward the introduction of side chains, especially for steroids with oxygen functionality at C-23.

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Construction of 2,6,9,11-tetraoxatricyclo[6.2.1.0(3,8)]undecane containing 4-keto-D-glucose skeleton

Ban Fujitani, Kengo Hanaya, Shuhei Higashibayash, Mitsuru Shoji, Takeshi Sugai

TETRAHEDRON 73 ( 51 ) 7217 - 7222 2017.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4020

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Non-Planar [n]Cyclo-1,8-carbazolylenes (n=3,4,6) and [3]Cyclo-1,8-carbazolylenyl B, P, PO, SiPh Complexes

Koji Yamamoto, Palash Pandit, Shuhei Higashibayashi

CHEMISTRY-A EUROPEAN JOURNAL 23 ( 56 ) 14011 - 14016 2017.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0947-6539

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Synthesis of the 1,2-seco fusicoccane diterpene skeleton by Stille coupling reaction between the highly functionalized A and C ring segments of cotylenin A

Kazuaki Kuwata, Kengo Hanaya, Shuhei Higashibayashi, Takeshi Sugai, Mitsuru Shoji

TETRAHEDRON 73 ( 41 ) 6039 - 6045 2017.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4020

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Synthesis of a C70 fragment buckybowl C28H14 from a C60 fragment sumanene

Shota Hishikawa, Yuki Okabe, Ryoji Tsuruoka, Shuhei Higashibayashi, Hiroyoshi Ohtsu, Masaki Kawano, Yumi Yakiyama, Hidehiro Sakurai

CHEMISTRY LETTERS 46   1556 - 1559 2017.07

Research paper (scientific journal), Joint Work, Accepted

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Synthesis of Triaryltriazasumanenes

Patcharin Kaewmati, Qitao Tan, Shuhei Higashibayashi, Yumi Yakiyama, Hidehiro Sakurai

CHEMISTRY LETTERS 46 ( 1 ) 146 - 148 2017.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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Electronic and vibrational structures in the S-0 and S-1 states of coronene

Sachi Kunishige, Ayumi Kanaoka, Toshihar Katori, Megumi Kawabata, Masaki Baba, Takaya Yamanaka, Shuhei Higashibayashi, Hidehiro Sakurai

JOURNAL OF CHEMICAL PHYSICS 146 ( 4 ) 14011 - 14016 2017.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0021-9606

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Sumanene derivatives functionalized at the internal carbon

Niti Ngamsomprasert, Jing-Shuang Dang, Shuhei Higashibayashi, Yumi Yakiyama, Hidehiro Sakurai

CHEMICAL COMMUNICATIONS 53 ( 4 ) 697 - 700 2017.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1359-7345

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Elucidation of the fluorine substitution position on the phenyl ring of synthetic cannabinoids by electron ionization-triple quadrupole mass spectrometry

Takaya Murakami, Yoshiaki Iwamuro, Reiko Ishimaru, Satoshi Chinaka, Ippei Noda, Shuhei Higashibayashi, Nariaki Takayama

JAPANESE JOURNAL OF FORENSIC SCIENCE AND TECHNOLOGY 22   133 - 143 2017

Research paper (scientific journal), Joint Work, Accepted

Synthesis of Hydroxysumanene and Substituent Effect of Hydroxy Group on Bowl Inversion Dynamics and Electronic Structure

Niti Ngamsomprasert, Gautam Panda, Shuhei Higashibayashi, Hidehiro Sakurai

JOURNAL OF ORGANIC CHEMISTRY 81 ( 23 ) 11978 - 11981 2016.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0022-3263

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Bowl Inversion and Electronic Switching of Buckybowls on Gold

Shintaro Fujii, Maxim Ziatdinov, Shuhei Higashibayashi, Hidehiro Sakurai, Manabu Kiguchi

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 138 ( 37 ) 12142 - 12149 2016.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0002-7863

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Redox-Dependent Transformation of a Hydrazinobuckybowl between Curved and Planar Geometries

Shuhei Higashibayashi, Palash Pandit, Rie Haruki, Shin-ichi Adachi, Reiji Kumai

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 55 ( 36 ) 10830 - 10834 2016.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1433-7851

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Thermal stability, solubility, and fluorescence property of poly(arylene vinylene ketone)s bearing 1,1 '-binaphthylene units

Tadashi Tsukamoto, Katsuya Maeyama,　Shuhei Higashibayashi, Hidehiro Sakurai

REACTIVE & FUNCTIONAL POLYMERS 100   123 - 129 2016.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1381-5148

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Synthesis of Three-Dimensional Butterfly Slit-Cyclobisazaanthracenes and Hydrazinobisanthenes through One-Step Cyclodimerization and Their Properties

Koji Yamamoto, Shuhei Higashibayashi

CHEMISTRY-A EUROPEAN JOURNAL 22 ( 2 ) 663 - 671 2016.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0947-6539

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Synthesis and Characterization of Poly(arylene vinylene ketone)s Bearing 1,1 '-Binaphthylene Units through Mizoroki-Heck Coupling Polymerization

Tadashi Tsukamoto, Katsuya Maeyama,　Shuhei Higashibayashi, Hidehiro Sakurai

CHEMISTRY LETTERS 44 ( 12 ) 1780 - 1782 2015.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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Synthesis of organosoluble and fluorescent aromatic polyketones bearing 1,1'-binaphthyl units through Suzuki-Miyaura coupling polymerization

Katsuya Maeyama,　Tadashi Tsukamoto, Hiroaki Kumagai, Shuhei Higashibayashi, Hidehiro Sakurai

POLYMER BULLETIN 72 ( 11 ) 2903 - 2916 2015.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0170-0839

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Intra- and Intermolecular Reactivity of Triplet Sumanenetrione

Kousei Kanahara, MD Mizanur Rahman Badal, Sayaka Hatano, Manabu Abe, Shuhei Higashibayashi, Naoto Takashina, Hidehiro Sakurai

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 88 ( 11 ) 1612 - 1617 2015.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0009-2673

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Synthesis and Acid-responsive Electron-transfer Disproportionation of Non- and Tetramesityl-substituted 1,1 ',9,9 '-Bicarbazole

Palash Pandit, Toshikazu Nakamura, Shuhei Higashibayashi

CHEMISTRY LETTERS 44 ( 10 ) 1336 - 1338 2015.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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Acid-regulated Electron-transfer Disproportionation of a Nonsubstituted Tetramethyl-biacridine Derivative

Koji Yamamoto, Toshikazu Nakamura, Shuhei Higashibayashi

CHEMISTRY LETTERS 44 ( 9 ) 1229 - 1231 2015.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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Comments on "Characterization of four new designer drugs, 5-chloro-NNEI, NNEI indazole analog, alpha-PHPP and alpha-POP, with 11 newly distributed designer drugs in illegal products"

Kenji Tsujikawa, Mika Inoue, Shuhei Higashibayashi, Hiroyuki Inoue

FORENSIC SCIENCE INTERNATIONAL 251   E15 - E17 2015.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0379-0738

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Investigation of the Dynamic Behavior of Bisumanenyl

Binod Babu Shrestha, Sangita Karanjit, Shuhei Higashibayashi, Toru Amaya, Toshikazu Hirao, Hidehiro Sakurai

ASIAN JOURNAL OF ORGANIC CHEMISTRY 4 ( 1 ) 62 - 68 2015.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2193-5807

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Acid/base-regulated reversible electron transfer disproportionation of N-N linked bicarbazole and biacridine derivatives

Palash Pandit, Koji Yamamoto, Toshikazu Nakamura, Katsuyuki Nishimura, Yuki Kurashige, Takeshi Yanai, Go Nakamura, Shigeyuki Masaoka, Ko Furukawa, Yumi Yakiyama, Masaki Kawano, Shuhei Higashibayashi

CHEMICAL SCIENCE 6 ( 7 ) 4160 - 4173 2015

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2041-6520

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Sumanenetrione Anions Generated by Electrochemical and Chemical Reduction

Shuhei Higashibayashi, Binod Babu Shrestha, Yuki Morita, Masahiro Ehara, Kei Ohkubo, Shunichi Fukuzumi, Hidehiro Sakurai

CHEMISTRY LETTERS 43 ( 8 ) 1297 - 1299 2014.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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Eclipsed Columnar Packing in Crystal Structure of Sumanenetrione

Binod Babu Shrestha, Yuki Morita, Tatsuhiro Kojima, Masaki, Kawano, Shuhei Higashibayashi, Hidehiro Sakurai

CHEMISTRY LETTERS 43 ( 8 ) 1294 - 1296 2014.08

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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DFT Studies of Mechanism and Origin of Stereoselectivity of Palladium-Catalyzed Cyclotrimerization Reactions Affording syn-Tris(norborneno)benzenes

Masahiro Yamanaka, Masumi, Morishima, Yukihiro Shibata, Shuhei Higashibayashi, Hidehiro Sakurai

ORGANOMETALLICS 33 ( 12 ) 3060 - 3068 2014.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0276-7333

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Synthesis of thermally stable, wholly aromatic polyketones with 2,2 '-dimethoxy-1,1 '-binaphthyl-6,6 '-diyl units through nanosized-palladium-cluster-catalyzed Suzuki-Miyaura coupling polymerization

Katsuya Maeyama, Masanori Suzuki, Tadashi Tsukamoto, Shuhei Higashibayashi, Hidehiro Sakurai

REACTIVE & FUNCTIONAL POLYMERS 79   24 - 28 2014.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1381-5148

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Correlation between bowl-inversion energy and bowl depth in substituted sumanenes

Binod Babu Shrestha, Sangita Karanjit, Shuhei Higashibayashi, Hidehiro Sakurai

PURE AND APPLIED CHEMISTRY 86 ( 5 ) 747 - 753 2014.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0033-4545

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Columnar/herringbone dual crystal packing of pyrenylsumanene and its photophysical properties

Binod Babu Shrestha, Shuhei Higashibayashi, Hidehiro Sakurai

BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY 10   841 - 847 2014.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1860-5397

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Beam-induced graphitic carbon cage transformation from sumanene aggregates

Jun-ichi Fujita, Masashi Tachi, Katsuhisa Murakami, Hidehiro Sakurai, Yuki Morita, Shuhei Higashibayashi, Masaki Takeguchi

APPLIED PHYSICS LETTERS 104 ( 4 ) 457 - 460 2014.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0003-6951

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Fluorinated and Trifluoromethylated Corannulenes

Bernd M. Schmidt, Berit Topolinski, Mihoko Yamada, Shuhei Higashibayashi, Mitsuhiko Shionoya, Hidehiro Sakurai, Dieter Lentz

CHEMISTRY-A EUROPEAN JOURNAL 19 ( 41 ) 13872 - 13880 2013.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0947-6539

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Stereoelectronic Effect of Curved Aromatic Structures: Favoring the Unexpected endo Conformation of Benzylic-Substituted Sumanene

Shuhei Higashibayashi, Satoru Onogi, Hemant Kumar Srivastava, G. Narahari Sastry, Yao-Ting Wu, Hidehiro Sakurai

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 52 ( 28 ) 7314 - 7316 2013.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1433-7851

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Jet spectroscopy of buckybowl: Electronic and vibrational structures in the S-0 and S-1 states of triphenylene and sumanene

Sachi Kunishige, Megumi Kawabata, Masaki Baba, Takaya Yamanaka, Yuki Morita, Shuhei Higashibayashi, Hidehiro Sakurai

JOURNAL OF CHEMICAL PHYSICS 139 ( 4 ) 13809 - 13812 2013.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0021-9606

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Nanosized palladium-catalyzed Suzuki-Miyaura coupling polymerization: synthesis of soluble aromatic poly(ether ketone)s

Katsuya Maeyama, Tadashi Tsukamoto, Masanori Suzuki, Shuhei Higashibayashi, Hidehiro Sakurai

POLYMER JOURNAL 45 ( 4 ) 401 - 405 2013.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0032-3896

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Synthesis of Substituted Sumanenes by Aromatic Electrophilic Substitution Reactions

Binod Babu Shrestha, Sangita Karanjit, Gautam Panda, Shuhei Higashibayashi, Hidehiro Sakurai

CHEMISTRY LETTERS 42 ( 4 ) 386 - 388 2013.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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The Synthesis of Hexafluorosumanene and Its Congeners

Bernd M. Schmidt, Berit Topolinski, Shuhei Higashibayashi, Tatsuhiro Kojima, Masaki Kawano, Dieter Lentz, Hidehiro Sakurai

CHEMISTRY-A EUROPEAN JOURNAL 19 ( 10 ) 3282 - 3286 2013.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0947-6539

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Magnetic circular dichroism spectroscopy and electronic structures of C-3 symmetry buckybowls

John Mack, Yuki Morita, Shuhei Higashibayashi, Hidehiro Sakurai, Nagao Kobayashi

CHEMICAL PHYSICS LETTERS 556   188 - 194 2013.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0009-2614

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Sumanenylferrocenes and their solid state self-assembly

Berit Topolinski, Bernd M. Schmidt, Shuhei Higashibayashi, Hidehiro Sakurai, Dieter Lentz

DALTON TRANSACTIONS 42 ( 38 ) 13809 - 13812 2013

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1477-9226

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Microwave-assisted synthesis of methyl (1S,2R,4S,5S)-7-aza-5-hydroxybicyclo[2.2.1]heptane-2-carboxylate through unexpected stereoselective substitution reaction

Satoru Onogi, Shuhei Higashibayashi, Hidehiro Sakurai

TETRAHEDRON LETTERS 53 ( 29 ) 3710 - 3712 2012.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4039

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Enantioselective synthesis of a chiral nitrogen-doped buckybowl

Qitao Tan, Shuhei Higashibayashi, Sangita Karanjit, Hidehiro Sakurai

NATURE COMMUNICATIONS 3   581 - 588 2012.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2041-1723

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Palladium-Catalyzed Arylation of Methylene-Bridged Polyarenes: Synthesis and Structures of 9-Arylfluorene Derivatives

Jheng-Jhih Chen, Satoru Onogi, Ya-Chu Hsieh, Chien-Chi Hsiao, Shuhei Higashibayashi, Hidehiro Sakurai, Yao-Ting Wu

ADVANCED SYNTHESIS & CATALYSIS 354 ( 8 ) 1551 - 1558 2012.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1615-4150

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Trimethylsumanene: Enantioselective Synthesis, Substituent Effect on Bowl Structure, Inversion Energy, and Electron Conductivity

Shuhei Higashibayashi, Ryoji Tsuruoka, Yarasi Soujanaya, Uppula Purushotham, G. Narahari Sastry, Shu Seki, Takeharu Ishikawa, Shinji Toyota, Hidehiro Sakurai

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 85 ( 4 ) 450 - 467 2012.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0009-2673

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Chiral phenylazomethine cage

Ryo Shomura, Shuhei Higashibayashi, Hidehiro Sakurai, Yoshitaka Matsushita, Akira Sato, Masayoshi Higuchi

TETRAHEDRON LETTERS 53 ( 7 ) 783 - 785 2012.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4039

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Selective Synthesis of C-3 Symmetric Functionalized Sumanenes

Shuhei Higashibayashi, Nasir Baig R. B., Yuki Morita, Hidehiro Sakurai

CHEMISTRY LETTERS 41 ( 1 ) 84 - 86 2012.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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Experimental electron density of sumanene, a bowl-shaped fullerene fragment; comparison with the related corannulene hydrocarbon

Stefan Mebs, Manuela Weber, Peter Luger, Bernd M. Schmidt, Hidehiro Sakurai, Shuhei Higashibayashi, Satoru Onogi, Dieter Lentz

ORGANIC & BIOMOLECULAR CHEMISTRY 10 ( 11 ) 2218 - 2222 2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1477-0520

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Emission amplification by sumanene nanocrystals in an onigiri-type organic-organic assembly

Yuki Morita, Satoru Nakao, Setsiri Haesuwanakij, Shuhei Higashibayashi, Hidehiro Sakurai

CHEMICAL COMMUNICATIONS 48 ( 72 ) 9050 - 9052 2012

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1359-7345

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Synthesis of Aromatic Polyketones Bearing 1,1 '-Binaphthyl-2,2 '-dioxy Units through Suzuki-Miyaura Coupling Polymerization

Katsuya Maeyama, Tadashi Tsukamoto, Masanori Suzuki, Shuhei Higashibayashi, Hidehiro Sakurai

CHEMISTRY LETTERS 40 ( 12 ) 1445 - 1446 2011.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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Stereoselective Cyclotrimerization of Enantiopure Iodonorbornenes Catalyzed by Pd Nanoclusters for C-3 or C-3v Symmetric syn-Tris(norborneno)benzenes

Shuhei Higashibayashi, A. F. G. Masud Reza, Hidehiro Sakurai

JOURNAL OF ORGANIC CHEMISTRY 75 ( 13 ) 4626 - 4628 2010.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0022-3263

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Optical Resolution of Chiral Buckybowls by Chiral HPLC

Ryoji Tsuruoka, Shuhei Higashibayashi, Takeharu Ishikawa, Shinji Toyota, Hidehiro Sakurai

CHEMISTRY LETTERS 39 ( 6 ) 646 - 647 2010.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

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Preparation of C-3-Symmetric Homochiral syn-Trisnorbornabenzenes through Regioselective Cyclotrimerization of Enantiopure Iodonorbornenes

A. F. G. Masud Reza, Shuhei Higashibayashi, Hidehiro Sakurai

CHEMISTRY-AN ASIAN JOURNAL 4 ( 8 ) 1329 - 1337 2009

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1861-4728

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Asymmetric synthesis of a chiral buckybowl, trimethylsumanene

Shuhei Higashibayashi, Hidehiro Sakurai

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 ( 27 ) 8592 - + 2008.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0002-7863

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Total synthesis of siomycin A: Completion of the total synthesis

Tomonori Mori, Shuhei Higashibayashi, Taiji Goto, Mitsunori Kohno, Yukiko Satouchi, Kazuyuki Shinko, Kengo Suzuki, Shunya Suzuki, Hiraku Tohmiya, Kimiko Hashimoto, Masaya Nakata

CHEMISTRY-AN ASIAN JOURNAL 3 ( 6 ) 1013 - 1025 2008

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1861-4728

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Total synthesis of siomycin A: Construction of synthetic segments

Tomonori Mori, Shuhei Higashibayashi, Taiji Goto, Mitsunori Kohno, Yukiko Satouchi, Kazuyuki Shinko, Kengo Suzuki, Shunya Suzuki, Hiraku Tohmiya, Kimiko Hashimoto, Masaya Nakata

CHEMISTRY-AN ASIAN JOURNAL 3 ( 6 ) 984 - 1012 2008

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1861-4728

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Total synthesis of siomycin A

Tomonori Mori, Shuhei Higashibayashi, Taiji Goto, Mitsunori Kohno, Yukiko Satouchi, Kazuyuki Shinko, Kengo Suzuki, Shunya Suzuki, Hiraku Tohmiya, Kimiko Hashimoto, Masaya Nakata

TETRAHEDRON LETTERS 48 ( 8 ) 1331 - 1335 2007.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4039

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Synthesis of an enantiopure syn-benzocyclotrimer through regio-selective cyclotrimerization of a halonorbornene derivative under palladium nanocluster conditions

Shuhei Higashibayashi, Hidehiro Sakurai

CHEMISTRY LETTERS 36 ( 1 ) 18 - 19 2007.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0366-7022

Synthetic studies on thiostrepton family of peptide antibiotics: synthesis of the dihydroquinoline portion of thiostrepton, the siomycins, and the thiopeptins

Tomonori Mori, Yukiko Satouchi, Hiraku Tohmiya, Shuhei Higashibayashi, Kimiko Hashimoto, Masaya Nakata

TETRAHEDRON LETTERS 46 ( 38 ) 6417 - 6422 2005.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4039

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Synthetic studies on thiostrepton family of peptide antibiotics: synthesis of the cyclic core portion containing the dehydropiperidine, dihydroquinoline, L-valine, and masked dehydroalanine segments

Tomonori Mori, Hiraku Tohmiya, Yukiko Satouchi, Shuhei Higashibayashi, Kimiko Hashimoto, Masaya Nakata

TETRAHEDRON LETTERS 46 ( 38 ) 6423 - 6427 2005.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4039

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Assignment of the relative and absolute configurations of acyclic secondary 1,2-diols

Shuhei, Higashibayashi, Yoshito, Kishi

TETRAHEDRON 60 ( 51 ) 11977 - 11982 2004.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4020

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Synthetic studies on thiostrepton family of peptide antibiotics: synthesis of the pentapeptide segment containing dihydroxyisoleucine, thiazoline and dehydroamino acid

Shuhei Higashibayashi, Mitsunori Kohno, Taiji Goto, Kengo Suzuki, Tomonori Mori, Kimiko Hashimoto, Masaya Nakata

TETRAHEDRON LETTERS 45 ( 19 ) 3707 - 3712 2004.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4039

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Synthesis of sulfinimines by direct condensation of sulfinamides with aldehydes using Cs2CO3 as an activating and dehydrating reagent

Shuhei Higashibayashi, Hiraku Tohmiya, Tomonori Mori, Kimiko Hashimoto, Masaya Nakata

SYNLETT  ( 3 ) 457 - 460 2004.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0936-5214

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Universal NMR databases for contiguous polyols

Shuhei Higashibayashi, Yoshihisa Kobayashi, Werngard Czechtizky, Yoshito Kishi

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125 ( 47 ) 14379 - 14393 2003.11

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0002-7863

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Synthetic studies on the thiostrepton family of peptide antibiotics: synthesis of the tetrasubstituted dehydropiperidine and piperidine cores

Syuhei Higashibayashi, Kimiko Hashimoto, Masaya Nakata

TETRAHEDRON LETTERS 43 ( 1 ) 105 - 110 2002.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0040-4039

Synthetic studies on thiostrepton family of peptide antibiotics: Synthesis of the tetrasubstituted dihydroquinoline portion of siomycin D-1

Syuhei Higashibayashi, Tomonori Mori, Kazuyuki Shinko, Kimiko Hashimoto, Masaya Nakata

HETEROCYCLES 57 ( 1 ) 111 - 122 2002.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0385-5414

Selective deprotection of t-butyldiphenylsilyl ethers in the presence of t-butyldimethylsilyl ethers by tetrabutylammonium fluoride, acetic acid, and water

Syuhei Higashibayashi, Kazuyuki Shinko, Takehiro Ishizu, Kimiko Hashimoto, Haruhisa Shirahama, Masaya Nakata

SYNLETT  ( 9 ) 1306 - 1308 2000.09

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0936-5214

Synthesis of (2(S)under-bar*,4(R)under-bar*,5(S)under-bar*)-piperidinetricarboxylic acid, a non-proteinogenic amino acid isolated from Clitocybe acromelalga

Kimiko Hashimoto, Shuhei Higashibayashi, Haruhisa Shirahama

HETEROCYCLES 46   581 - 588 1997.12

Research paper (scientific journal), Joint Work, Accepted,  ISSN  0385-5414