Details of a Researcher - OISHI Takeshi

Papers - OISHI Takeshi

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Total Synthesis and Anti-inflammatory Activity of Stemoamide-Type Alkaloids Including Totally Substituted Butenolides and Pyrroles

Soda Y., Sugiyama Y., Sato S., Shibuya K., Saegusa J., Matagawa T., Kawano S., Yoritate M., Fukaya K., Urabe D., Oishi T., Mori K., Simizu S., Chida N., Sato T.

Synthesis (Germany) (Synthesis (Germany)) 2022

ISSN 00397881

The totally substituted butenolide including two tetrasubstituted olefins is a distinct structural motif seen in Stemona alkaloids, but efficient methods for its synthesis are not well developed. As an ongoing program aimed at the collective total synthesis of the stemoamide group, we report a stereodivergent method to give either (E)-or (Z)-totally substituted butenolide from the same intermediate. While the AgOTf-mediated elimination via the E1-type mechanism results in the formation of the kinetic (Z)-tetrasubstituted olefin, the subsequent TfOH-mediated isomerization gives the thermodynamic (E)-tetrasubstituted olefin. The pyrrole ring is another important structure found in Stemona alkaloids. The direct oxidation of pyrrolidine rings with MnO2 and careful purification give the pyrrole groups without isomerization of the stereocenter in the lactone group. These two methods enable us to synthesize a series of stemoamide-type alkaloids including tricyclic, tetracyclic and pentacyclic frameworks. The anti-inflammatory activities by inhibition of iNOS expression in macrophage cell line RAW264.7 indicate that the most potent anti-inflammatory compounds without cytotoxicity are protostemonines, which consist of pentacyclic frameworks including the totally substituted butenolide.

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Lactam Strategy Using Amide-Selective Nucleophilic Addition for Quick Access to Complex Amines: Unified Total Synthesis of Stemoamide-Type Alkaloids

Sugiyama Yasukazu, Soda Yasuki, Yoritate Makoto, Tajima Hayato, Takahashi Yoshito, Shibuya Kana, Ogihara Chisato, Yokoyama Takashi, Oishi Takeshi, Sato Takaaki, Chida Noritaka

Bulletin of the Chemical Society of Japan (The Chemical Society of Japan) 95 ( 2 ) 278 - 287 2022

ISSN 00092673

Our research group has been exploring a lactam strategy for the concise total synthesis of complex alkaloids. In this article, we report full details of the unified total synthesis of stemoamide-type alkaloids by chemoselective assembly of five-membered rings based on the lactam strategy. First, the concise and gram-scale synthesis of tricyclic stemoamide was achieved by vinylogous Michael addition-reduction sequence of an unsaturated γ-lactam with an unsaturated γ-lactone, followed by N-alkylation to form the seven-membered ring. From stemoamide as a common intermediate, chemoselective nucleophilic addition of unsaturated lactone derivatives provides tetracyclic natural products. While stemonine is obtained by an Ir-catalyzed lactam-selective reductive Mannich reaction, saxorumamide and isosaxorumamide are produced through the lactone-selective nucleophilic addition of the lithiated 2-silyl furan. The developed conditions for the lactam-selective nucleophilic reactions are highly general, and were found to be applicable to the total synthesis of pentacyclic stemocochinin and isostemocochinin. The strategy enables the concise and unified total synthesis of tricyclic, tetracyclic and pentacyclic stemoamide-type alkaloids within 12 steps from a commercially available compound.

Crystal structure of (+)-(1S,5S,6S,7S,10S,11S,16S)-16-hy droxy-7-(meth oxy meth oxy)-11,15,18,18-tetra methyl-3,13-dioxo-2,4-dioxa tetra cyclo[12.3.1.01,5.06,11]octa dec-14-en-10-yl benzoate

Oishi T., Fukaya K., Sato T., Chida N.

Acta Crystallographica Section E: Crystallographic Communications (Acta Crystallographica Section E: Crystallographic Communications) 77 1234 - 1238 2021.12

ISSN 2056-9890

In the fused tetra cyclic system of the title compound, C29H36O9, the five-membered dioxolane ring adopts a twist conformation; the two adjacent C atoms deviate alternately from the mean plane of the other three atoms by -0.252 (6) and 0.340 (6) Å. The cyclo hexane, cyclo hexene and central cyclo octane rings show chair, half-chair and boat-chair forms, respectively. There are three intra molecular C - H⋯O inter actions supporting the mol ecular conformation, with one S(6) and two S(7) graph-set motifs. In the crystal, inter molecular O - H⋯O hydrogen bonds connect the mol ecules into a helical chain running along the c-axis direction, generating a C(7) graph-set motif. The chains are further linked by inter molecular C - H⋯O inter actions to construct a three-dimensional network. There is no valid C - H⋯π inter action.

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Total Synthesis of Paclitaxel

Iiyama S., Fukaya K., Yamaguchi Y., Watanabe A., Yamamoto H., Mochizuki S., Saio R., Noguchi T., Oishi T., Sato T., Chida N.

Organic Letters (Organic Letters) 24 ( 1 ) 202 - 206 2021

ISSN 15237060

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Unified Total Synthesis of Pentacyclic Stemoamide-type Alkaloids

Soda Y., Sugiyama Y., Yoritate M., Tajima H., Shibuya K., Ogihara C., Oishi T., Sato T., Chida N.

Organic Letters (Organic Letters) 22 ( 19 ) 7502 - 7507 2020.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 15237060

The collective synthesis of pentacyclic stemoamide-type alkaloids is recognized as a daunting task despite high demand for a comprehensive biological profiling of these natural products. In this Letter, we report a unified synthesis of seven pentacyclic alkaloids and two unnatural derivatives. The keys to success are (1) the chemoselective assembly of four five-membered building blocks, (2) the direct oxidation of pyrrolidine natural products to pyrrole derivatives, and (3) the stereodivergent construction of totally E- or Z-substituted butenolides.

Asymmetric Total Synthesis of Fasicularin by Chiral N-Alkoxyamide Strategy

S. Yamamoto, Y. Komiya, A. Kobayashi, R. Minamikawa, T. Oishi, T. Sato, N. Chida

Organic Letters (American Chemical Society) 21 ( 6 ) 1868 - 1871 2019.02

Research paper (scientific journal), Joint Work, Accepted, ISSN 15237060

© 2019 American Chemical Society. The asymmetric total synthesis of fasicularin is reported. The key to success is the use of a chiral N-alkoxyamide to control both reactivity and stereoselectivity. This functional group enables the aza-spirocyclization and the reductive Strecker reaction, which cannot be realized with an ordinary amide. In addition, use of the chiral alkoxy group establishes two consecutive stereocenters in the aza-spirocyclization through remote stereocontrol.

Total synthesis of (–)-zephyranthine

Ishii K., Seki-Yoritate Y., Ishibashi M., Liaw M., T. Oishi, T. Sato, N. Chida

Heterocycles (Heterocycles) 99 ( 1 ) 111 - 117 2018.10

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

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Crystal structure of (–)-(R,E)-3-(1,3-benzodioxol-5-yl)-5-[(4S,5R)-5-hydroxymethyl-2,2-dimethyl-1,3-dioxolan-4-yl]-N,N-dimethylpent-4-enamide

T. Oishi, K. Ishii, M. Ishibashi, T. Sato, N. Chida

Acta Crystallographica (International Union of Cristallographica) E74 ( 7 ) 825 - 828 2018.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 2056-9890

© 2018 International Union of Crystallography. All rights reserved. In the title compound, C 20 H 27 NO 6 , the amide moiety is essentially planar, with a maximum deviation of 0.073(3)Å, and one of the N-methyl groups shows rotational disorder. The five-membered 1,3-dioxolane ring adopts an envelope form, with the C atom bonded to the olefin side chain as the flap, which deviates from the mean plane through the other four atoms by 0.564(7)Å. The 1,3-dioxole ring fused to the benzene ring adopts a flattened envelope form, with the C atom between the two O atoms as the flap, which deviates from the mean plane through the other four atoms by 0.215(7)Å. The C-C=C-C olefin moiety is essentially planar and makes a dihedral angle of 87.1(3)° with the benzene ring. An intramolecular O-H O hydrogen bond supports the molecular conformation, enclosing an S(11) graph-set motif. In the crystal, intermolecular C-H O hydrogen bonding links the molecules into a tape running along the b axis. Furthermore, other weak C-H;O hydrogen bonds and a C-Hπ interaction connect the tapes into a sheet structure parallel to (100).

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Crystal structure of (–)-(5R,7R,8S,9R,10S)-8-methyl-7-[(5R)-3-methyl-2-oxooxolan-3-en-5-yl]-1-aza-6-oxatricyclo[8.3.0.0^5,9]tridecan-13-one monohydrate

T. Oishi, M. Yoritate, T. Sato and N. Chida

Acta Crystallographica (International Union of Crystallography) E74 ( 4 ) 555 - 558 2018.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 2056-9890

© 2018 Oishi et al. The title compound, C17 H23 NO4 ·H2 O, is an epimer of the natural tetracyclic alkaloid isosaxorumamide which consists of a fused 5-7-5 tricyclic core and a dihydrofuranone substituent. The terminal dihydrofuran ring is essentially planar with a maximum deviation of 0.0273(14)Å from the mean plane and oxolane, azepane and pyrrolidine rings in the tricyclic ring system adopt twist, twist-chair and envelope forms, respectively. In the crystal, the amide and water molecules are linked by O - H...O hydrogen bonds, forming a tape structure running along the b-axis direction. The tapes are further connected by C - H...O interactions into a three-dimensional architecture.

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Synthesis of Kaitocephalin Facilitated by Three Stereoselective Allylic Transposition Reactions

T. Sugai, Y. Okuyama, J. Shin, S. Usui, S. Hisada, R. Osanai, T. Oishi, T. Sato, N. Chida

Chemistry Letters (Chemical Society of Japan) 47 ( 4 ) 454 - 457 2018.01

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

© 2018 The Chemical Society of Japan. A stereoselective synthesis of kaitocephalin is described. The central strategy is based on chirality transfer reactions of three secondary alcohols derived from L-arabinose. The Overman rearrangement of an α,β-unsaturated ester, and intramolecular anti-type S N 2¤ reaction constructed a β-hydroxy-α,α-disubstituted amino acid moiety. The third chirality transfer reaction is the Ichikawa rearrangement. These stereoselective reactions successfully established the three contiguous stereocenters embedded in kaitocephalin.

Synthesis of α-Hydroxy-α,α-disubstituted Amino Acids through the Orthoamide-Type Overman Rearrangement of an α,β-Unsaturated Ester and Stereodivergent Intramolecular S_N2’ Reaction: Development and Application to the Total Synthesis of Sphingofungin F

T. Sugai, S. Usui, S. Tsuzaki, H. Oishi, D. Yasushima, S. Hisada, T. Fukuyasu, T. Oishi, T. Sato, N Chida

Bulletin of the Chemical Society of Japan (Chemical Society of Japan) 91 ( 4 ) 594 - 607 2018.01

Research paper (scientific journal), Accepted, ISSN 1348-0634

© 2018 The Chemical Society of Japan. The development of a two-step synthesis for β-hydroxy-α,α- disubstituted amino acid derivatives from cyclic orthoamide is reported. The first step is the orthoamide-type Overman rearrangement of an α,β-unsaturated ester to give a sterically hindered α,α-disubstituted amidoester. The α,β-unsaturated ester is known to be a challenging substrate in the conventional Overman rearrangement due to the competitive aza-Michael reaction. However, suppression of the aza-Michael reaction is realized by two factors; 1) the high reaction temperature, and 2) an alkyl substituent at the α-position. The second step is stereodivergent intramolecular SN2′ reaction for the installation of a hydroxy group at the β-position. Either syn- or anti-type SN2′ reaction is possible by simply changing the reaction conditions. The developed method can provide all four possible stereoisomers of the β-hydroxy-α,α-disubstituted amino acid, and is successfully applied to the total synthesis of sphingofungin F.

2.　Stereodivergent Synthesis of β-Hydroxy-α,α-Disubstituted Amino Acids: Development and Application to the Syntheses of Natural Products.

Sugai Tomoya, Fukuyasu Takahiro, Oishi Takeshi, Sato Takaaki, Chida Noritaka, Okuyama Yuya, Usui Shunme, Tsuzaki Syun, Shin Jaehyun, Oishi Hiroki, Yasushima Daichi, Osanai Ryosuke, Hisada Shoko

Symposium on the Chemistry of Natural Products, symposium papers (Symposium on the Chemistry of Natural Products Steering Committee) 60 ( 0 ) 7 - 12 2018

【研究背景】β-ヒドロキシ-α,α-二置換アミノ酸（1）は、スフィンゴファンジンF（2）や(–)-カイトセファリン（3）など生物活性天然物に広く見られる重要な構造モチーフである（Figure 1A）。これまで1の立体選択的な合成法は精力的に開発されてきたが、4種すべての立体異性体を作り分ける合成法は、数例しか報告されていなかった1)。そこで、私達は次のような基本合成戦略を立てた（Figure 1B）。不飽和エステルを有するオルトアミド4のOverman転位によって、1,4-アミドアルコール5を合成する。続いて、分子内SN2'反応を用いてオキサゾリン6または7を立体選択的に合成すれば、β-ヒドロキシ-α,α-二置換アミノ酸の立体選択的な作り分けが実現できると考えた。本発表では不飽和エステルのOverman転位と立体選択的SN2'反応によるβ-ヒドロキシ-α,α-二置換アミノ酸の合成法の開発と、これを用いたスフィンゴファンジンF（2）および(–)-カイトセファリン（3）の不斉合成を報告する。【不飽和エステルのOverman転位】2,3）Overman転位は立体選択的に、窒素原子を導入する手法として広く利用されているシグマトロピー転位の1つである。Overman転位が不飽和エステル8に対して適用できれば、アミノ酸構造を一挙に構築できる有用な手法となる（8→9→11）。しかし、イミデート9を加熱するとaza-Michael反応（9→10）が進行するため、Overman転位は利用できないと報告されていた4)。そのため、既存の手法では保護体12へと

Unified Total Synthesis of Stemoamide-Type Alkaloids by Chemoselective Assembly of Five-Membered Building Blocks

M. Yoritate, Y. Takahashi, H. Tajima, C. Ogihara, T. Yokohama, Y. Soda, T. Oishi, T. Sato, N. Chida

Journal of the American Chemical Society (ACS) 139 ( 50 ) 18386 - 18391 2017.11

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

A unified total synthesis of stemoamide-type alkaloids is reported. Our synthetic approach features the chemoselective convergent assembly of five-membered building blocks via stemoamide as the common precursor to tetracyclic natural products. The synthesis consists of two successive coupling reactions of the three five-membered building blocks. The first coupling reaction is the vinylogous Michael addition/reduction sequence, which enables the gram-scale synthesis of stemoamide. The second coupling reaction is a chemoselective nucleophilic addition to stemoamide. While the lactone-selective nucleophilic addition to stemoamide affords saxorumamide and isosaxorumamide, the lactam-selective reductive nucleophilic addition leads to the formation of stemonine. Both chemoselective nucleophilic additions enable direct modification of stemoamide, resulting in highly concise and efficient total syntheses of the stemoamide-type alkaloids.

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Crystal structure of (–)-methyl (R,E)-4-[(2R,4R)-2-amino-2-trichloromethyl-1,3-dioxolan-4-yl]-4-hydroxy-2-methylbut-2-enoate

T. Oishi, M. Kidena, T. Sugai, T. Sato, N. Chida

Acta Crystallographica (International Union of Crystallography) E73 ( 7 ) 983 - 986 2017.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 2056-9890

In the title compound, C10H14Cl3NO5, the five-membered dioxolane ring adopts an envelope conformation with the C atom bonded to the butenoate side chain as the flap. It deviates from the mean plane of the other atoms in the ring by 0.446 (6) Å. In the crystal, molecules are connected by O—H⋯O hydrogen bonds into helical chains running along the b-axis direction. The chains are linked into a sheet structure parallel to (001) by an N—H⋯O hydrogen bond. These classical hydrogen bonds enclose an R44(24) graph-set motif in the sheet structure. Furthermore, a weak intermolecular C—H⋯Cl interaction expands the sheet structures into a three-dimensional network.

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Crystal structure of (+)-N-[(1R,5S,6S,9S)-5-hydroxymethyl-3,3,9-trimethyl-8-oxo-2,4,7-trioxabicyclo[4.3.0]nonan-9-yl]acetamide

T. Oishi, S. Tsuzaki, T. Sugai, T. Sato, N. Chida

Acta Crystallographica (International Union of Crystallography) E72 ( 5 ) 756 - 759 2016.04

Research paper (scientific journal), Joint Work, Accepted, ISSN 2056-9890

In the title compound, C12H19NO6, the six-membered 1,3-dioxane ring adopts a chair-like conformation. The seat of this chair, containing two O atoms, is essentially planar, with a maximum deviation of 0.0021(12)A. The five-membered oxolane ring cis-fused to the 1,3-dioxane ring adopts an envelope form. The bridgehead C atom at the flap, which is bonded to the tetrasubstituted C atom of the oxolane ring, deviates from the mean plane of other ring atoms by 0.539(4)A. In the crystal, classical O - H⋯O and N - H⋯O hydrogen bonds link the molecules into a sheet structure enclosing an R 4 4(24) graph-set motif. Weak intermolecular C - H⋯O interactions support the sheet formation.

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Crystal structure of (+)-methyl (E)-3-[(2S,4S,5R)-2-amino-5-hydroxymethyl-2-trichloromethyl-1,3-dioxolan-4-yl]-2-methylprop-2-enoate

T. Oishi, D. Yasushima, K. Yuasa, T. Sato and N. Chida

Acta Crystallographica (International Union of Crystallography) E72 ( 3 ) 343 - 346 2016.02

Research paper (scientific journal), Joint Work, Accepted, ISSN 2056-9890

In the title compound, C10H14Cl3NO5, the five-membered dioxolane ring adopts an envelope conformation. The C atom at the flap, which is bonded to the hydroxymethyl substituent, deviates from the mean plane of other ring atoms by 0.357 (5) Å. There are two intramolecular hydrogen bonds (O—H⋯N and N—H⋯O) between the hydroxy and amino groups, so that O- and N-bound H atoms involved in these hydrogen bonds are each disordered with equal occupancies of 0.50. The methyl 2-methylprop-2-enoate substituent also shows a disordered structure over two sets of sites with refined occupancies of 0.482 (5) and 0.518 (5). In the crystal, molecules are connected into a dimer by an O—H⋯O hydrogen bond. The dimers are further linked by N—H⋯O, C—H⋯N and C—H⋯O interactions, extending a sheet structure parallel to (-101).

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Crystal structure of (+–)-(5SR,6SR)-6-ethenyl-1-[(RS)-1-phenylethoxy]-1-azaspiro[4.5]decan-2-one

T Oishi, S. Yamamoto, T. Yokoyama, A. Kobayashi, T. Sato and N. Chida

Acta Crystallographica (International Union of Crystallography) E71 ( 12 ) 1528 - 1530 2015.11

Research paper (scientific journal), Joint Work, Accepted, ISSN 2056-9890

In the title compound, C19H25NO2, the pyrrolidine ring adopts an envelope form, with the spiro C atom as the flap, while the cyclohexane ring shows a chair form. A weak intramolecular C—H⋯O interaction supports the molecular conformation, generating an S(6) ring motif. In the crystal, pairs of C—H⋯O interactions connect the molecules into inversion dimers with an R22(16) ring motif. The dimers are linked by a second pair of C—H⋯O interactions, enclosing an R42(12) ring motif, into a tape structure along the b axis.

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Crystal structure of (+–)-(7RS,8SR)-7-methyl-1,4-dioxaspiro[4.5]decane-7,8-diol

T. Oishi, H. Yamamoto, T. Sugai, K. Fukaya, Y. Yamaguchi, A. Watanabe, T. Sato and N. Chida

Acta Crystallographica (International Union of Crystallography) E71 ( 10 ) 1181 - 1184 2015.09

Research paper (scientific journal), Joint Work, Accepted, ISSN 2056-9890

In the title compound, C9H16O4, the five-membered dioxolane ring adopts a twist conformation; two adjacent C atoms deviate alternately from the mean plane of other atoms by −0.297 (4) and 0.288 (4) Å. The spiro-fused cyclohexane ring shows a chair form. The hydroxy group substituted in an axial position makes an intramolecular O—H⋯O hydrogen bond with one of the O atoms in the cyclic ether, forming an S(6) ring motif. In the crystal, the O—H⋯O hydrogen bond involving the equatorial hydroxy group connects the molecules into a zigzag chain with a C(5) motif running along the c axis.

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Synthesis of Paclitaxel. 2. Construction of the ABCD Ring and Formal Synthesis

K. Fukaya, K. Kodama, Y. Tanaka, H. Yamazaki, T. Sugai, Y. Yamaguchi, A. Watanabe, T. Oishi, T. Sato, N. Chida

Organic Letters (American Chemical Society) 17 ( 11 ) 2574 - 2577 2015.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 1523-7060

A formal synthesis of the antitumor diterpenoid paclitaxel (Taxol) is described. The ABC ring of paclitaxel, synthesized starting from 1,3-cyclohexanedione and tri-O-acetyl-d-glucal by SmI2-mediated cyclization as the key transformation, was successfully converted to Takahashi’s tetracyclic oxetane intermediate. A double Chugaev reaction was employed for introduction of the strained bridgehead olefin, and stereoselective formation of the oxetane ring afforded the known synthetic intermediate, completing the formal synthesis of paclitaxel.

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Synthesis of Paclitaxel. 1. Synthesis of the ABC Ring of Paclitaxel by SmI₂-Mediated Cyclization

K. Fukaya, Y. Tanaka, A. C. Sato, K. Kodama, H. Yamazaki, T. Ishimoto, Y. Nozaki, Y. M. Iwaki, Y. Yuki, K. Umei, T. Sugai, Y. Yamaguchi, A. Watanabe, T. Oishi, T. Sato, N. Chida

Organic Letters (American Chemical Society) 17 ( 11 ) 2570 - 2573 2015.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 1523-7060

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