Papers - OISHI Takeshi

Crystal structure of (+–)-(1SR,5SR,6SR,7SR,10SR,11SR,13SR)-13-benzyloxy-7-methoxymethoxy-11,15,18,18-tetramethyl-3-oxo-2,4-dioxatetracyclo [12.3.1.0^1,5.0^6,11]octadeca-14,16-dien-10-yl benzoate

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

Acta Crystallographica (International Union of Crystallography)  E71 ( 5 ) 490 - 493 2015.04

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

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In the title compound, C36H42O8, the dioxolane ring adopts a twist conformation; the two adjacent C atoms deviate alternately from the mean plane of other atoms by −0.287 (5) and 0.174 (5) Å. The cyclo­hexane, cyclo­hexa­diene and central cyclo­octane rings show chair, half-chair and boat–chair forms, respectively. As a result of the strained ring system, the tetra­subsituted olefin in the cyclo­hexa­diene is skewed from an ideal planar structure. In the crystal, C—H⋯O hydrogen bonds connect the mol­ecules into a sheet parallel to (100). The sheets are further linked by other weak C—H⋯O and C—H⋯π inter­actions, forming a three-dimensional network.

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Crystal structures of (+–)-(1SR,5SR,6SR,7SR,10SR,11SR,13RS,14SR)-13-hydroxy-7-methoxymethoxy-11,15,18,18-tetramethyl-3-oxo-2,4-dioxatetracyclo[12.3.1.0^1,5.0^6,11]octadec-15-en-10-yl benzoate, its 13-epimer and 13-one derivative

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

Acta Crystallographica (International Union Crystallography)  E71 ( 5 ) 466 - 472 2015.04

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

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The title compounds, C29H38O8·0.25C5H12, (A), C29H38O8, (B), and C29H36O8, (C), are tetra­cyclic benzoates possessing a taxane skeleton with a fused dioxolane ring as the core structure. In the asymmetric unit of (A), there are two independent benzoate mol­ecules (A and A′) and a half mol­ecule of solvent pentane disordered about an inversion center. The mol­ecular conformations of (A), (B) and (C) are similar except for the flexible meth­oxy­meth­oxy group. The cyclo­hexane, cyclo­hexene and central cyclo­octane rings adopt chair, half-chair and chair–chair (extended crown) forms, respectively. The dioxolane rings are essentially planar, while the dioxolane ring of A′ is slightly twisted from the mean plane. In the crystal of (A), inter­molecular O—H⋯O, C—H⋯O and C—H⋯π inter­actions link the independent benzoates alternately, forming a chain structure. In the crystals of (B) and (C), mol­ecules are linked through O—H⋯O and C—H⋯π inter­actions, and C—H⋯O hydrogen bonds, respectively, into similar chains. Further, weak inter­molecular C—H⋯O inter­actions connect the chains into a three-dimensional network in (A) and a sheet in (B), whereas no other interactions are observed for (C).

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Total Synthesis of Sphingofungin F by Orthoamide-Type Overman Rearrangement of an Unsaturated Ester

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

Organic Letters 17 ( 7 ) 1704 - 1707 2015.03

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

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The total synthesis of sphingofungin F through the Overman rearrangement of an unsaturated ester, which is known to be an unsuitable substrate under standard conditions due to the competitive aza-Michael reaction, is described. The developed conditions enabled the ester to be compatible with the original Overman rearrangement, providing quick access to α,α-disubstituted amino acids by minimizing extra protecting group manipulations and redox reactions.

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Crystal structure of (+–)-(4RS,5RS,7SR)-4-[(1RS,2RS,3RS,6RS)-3-benzoyloxy-2-(2-hydroxyethyl)-6-methoxymethoxy-2-methylcyclohex yl]-8,10,10-trimethyl-2-oxo-1,3-dioxaspiro[4.5]dec-8-en-7-yl benzoate benzene monosolvate

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

Acta Crystallographica (International Union of Crystallography)  E71 ( 1 ) 8 - 11 2015.01

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1600-5368

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In the title compound, C36H44O10·C6H6, the dioxolane ring adopts an envelope conformation with the C atom bonded to the H atom as the flap, while the cyclo­hexene and cyclo­hexane rings are in half-chair and chair conformations, respectively. In the crystal, a pair of O—H⋯O hydrogen bonds with an R22(26) graph-set motif connect the benzoate mol­ecules into an inversion dimer. The dimers are linked by a weak C—H⋯O inter­action into a tape structure along [01-1]. The benzene mol­ecule links the tapes through C—H⋯O and C—H⋯π inter­actions, forming a sheet parallel to (100).

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(5R*)-5-[(2S*,5S*)-1-Methoxy-5-phenylpyrrolidin-2-yl]-3-methylfuran-2(5H)-one

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

Acta Crystallographica (International Union of Crystallography)  E70 ( 8 ) o839 2014.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1600-5368

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In the title compound, C16H19NO3, the pyrrolidine ring is in a twist conformation. The dihedral angle between the di­hydro­furan ring [maximum deviation = 0.0016 (11) Å] and the phenyl ring is 47.22 (8)°. In the crystal, mol­ecules are linked by weak C—H⋯O hydrogen bonds, forming helical chains along the b-axis direction. The chains are further linked by C—H⋯π inter­actions to constitute a three-dimensional architecture.

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(+)-(1S,5R,6R)-6-[(S)-1-Hydroxy-2-(methoxymethyloxy)ethyl]-1-methyl-3-trichloromethyl-2-aza-4,7-dioxabicyclo[3.3.0]oct-2-en-8-one

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

Acta Crystallographica (International Union of Crystallography)  E68 ( 11 ) o3185 2012.10

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1600-5368

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In the title compound, C11H14Cl3NO6, the fused five-membered oxazoline and tetra­hydro­furan rings are essentially planar with maximum deviations of 0.069 (1) and 0.031 (1) Å, respectively, and make a dihedral angle of 64.23 (11)° with each other. In the crystal, mol­ecules are linked by O—H⋯O and C—H⋯O hydrogen bonds, forming chains along the b-axis direction. Further C—H⋯O hydrogen bonds are observed between the chains.

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Concise synthesis of α-trisubstituted amines from ketones using N-methoxyamines

Y. Kurosaki, K. Shirokane, T. Oishi, T. Sato, N. Chida

Organic Letters (American Chemical Society)  14 ( 8 ) 2098 - 2101 2012.04

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

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Three-component allylation and cyanation utilizing a ketone and an N-methoxyamine are reported. The high nucleophilicity of the N-methoxyamine and high electrophilicity of the corresponding iminium ion enable the concise synthesis of α-trisubstituted amines in a single step.

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Concise synthesis of <i>gamma</i>-trisubstituted amines from ketones using <i>N</i>-methoxyamines

Y. Kurosaki, K. Shirokane, T. Oishi, T. Sato, N. Chida

<i>Organic Letters</i> (American Chemical Society)  14 ( 8 ) 2098-2101 2012

Accepted

Total synthesis of mycestericin A and its 14-epimer

H. Yamanaka, K. Sato, H. Sato, M. Iida, T. Oishi, N. Chida

Tetrahedron (Elsevier)  65 ( 45 ) 9188 - 9201 2009.09

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

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The total synthesis of mycestericin A (1) and its 14-epimer 34 is described herein. The Overman rearrangement of an allylic trichloroacetimidate derived from l-tartrate generated a tetra-substituted carbon with nitrogen and subsequent stereoselective transformations afforded the highly functionalized left-half segment, vinyl iodide. Cross-coupling of the vinyl iodide with a chiral organometallic species synthesized from d-tartrate under the Negishi or Suzuki–Miyaura coupling conditions, followed by deprotection, completed the total synthesis of 1. The 14-epimer of mycestericin A was also synthesized, and a comparison of [α]D values of peracetyl γ-lactone derivatives of mycestericin A and its 14-epimer as well as degradation studies of 1 and 34 fully confirmed the proposed absolute structure of mycestericin A.

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Photochemical reduction of flavone with NaBH₄ in batch and micro-channel reactors using excimer lasers

A. Ouchi, H. Sakai, T. Oishi, M. Kaneda, T. Suzuki, A. Saruwatari, T. Obata

J. Photochemistry and Photobiology A: Chem. (Elsevier)  199 ( 2-3 ) 261 - 266 2008.06

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1010-6030

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Photochemical reduction of a stable enone, flavone (1), was accomplished by excimer laser photolysis using NaBH4 in ethanol, which formed flavanone (2) as a primary product in contrast to the formation of dimers that predominate in conventional photolysis. Flavanone (2) underwent successive thermal reduction with NaBH4 leading to flavanol (3) and photolysis to ethyl salicylate (4), in which the formation of 4 was completely suppressed when a single laser shot was used for the photolysis. The photolysis was conducted using quartz batch reactors having different optical paths and a quartz micro-channel reactor, in combination with KrF and XeCl excimer laser irradiation. This showed a considerable acceleration of the reaction with the micro-channel reactor, and the selectivity of the photoproducts 2, 3, and 4 depended on the optical path of the reactors, the laser wavelengths, the concentration of NaBH4, and the laser repetition rate. An optimal irradiation condition - application of sufficient time interval between the XeCl laser pulses, a low concentration of 1, and high concentration of NaBH4 - showed a considerable increase in the selectivity of 3 by eliminating the formation of 2 and 4.

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Total synthesis of mycestericin A

H. Sato, K. Sato, M. Iida, H. Yamanaka, T. Oishi, N. Chida

Tetrahedron Letters (Elsevier)  49 ( 12 ) 1943 - 1947 2008.01

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

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The first total synthesis of mycestericin A (1) starting from tartrates is described. The Overman rearrangement of an allylic trichloroacetimidate generated a tetra-substituted carbon with nitrogen, and subsequent stereoselective transformations afforded the highly functionalized vinyl iodide. The cross-coupling of the vinyl iodide with a chiral organozinc species under Negishi conditions, followed by deprotection, completed the total synthesis of 1.

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Amaryllidaceae alkaloids, (+)-Vittatine and (+)-Haemanthamine, starting from D-glucose

M. Bohno, K. Sugie, H. Imase, Y. B. Yusof, T. Oishi, N. Chida

Tetrahedron (Elsevier)  63 ( 30 ) 6977 - 6989 2007.05

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

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The stereoselective total synthesis of (+)-vittatine 1 and (+)-haemanthamine 2 starting from d-glucose is described. The cyclohexene ring in 1 was prepared in an optically active form from d-glucose using Ferrier's carbocyclization reaction, and the critical quaternary carbon was stereoselectively generated via chirality transfer by the Claisen rearrangement of cyclohexenol 6. The hexahydroindole skeleton was effectively constructed by the intramolecular aminomercuration–demercuration of 14, followed by Chugaev reaction to provide 16. Finally, Pictet–Spengler reaction completed the first chiral synthesis of (+)-vittatine 1. On the other hand, the α-hydroxylation of the ester 5 stereoselectively proceeded to give α-hydroxy ester 19, to which was introduced an amino function to provide 4. A similar transformation of 4, as employed in the synthesis of vittatine, furnished (+)-haemanthamine 2.

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Reductive total chlorine free photochemical bleaching of cellulosic fabrics, an energy conserving proces

A. Ouchi, T. Obata, T. Oishi, H. Sakai, T. Hayashi, W. Ando, J. Ito

Green Chemistry (Royal Society of Chemistry)  6 ( 4 ) 198 - 205 2004.03

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1463-9262

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Water-insoluble natural colored compounds adsorbed or chemically bound on cellulosic fabrics were bleached effectively at room temperature by a selective photolysis of the colored compounds using various excimer lasers (ArF, KrF, XeCl, XeF), a low-pressure mercury lamp, and a black-light fluorescent lamp in the presence of aqueous solutions of various reducing reagents. Sodium borohydride gave the best efficiency on the bleaching when KrF, XeCl, XeF excimer lasers or a low-pressure mercury lamp were used as light sources and the efficiency of the bleaching was found to be comparable to that of the conventional thermal bleaching processes.

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Total syntheses of natural products containing <i>alpha</i>-substituted <i>alpha</i>-amino acid structures from aldohexoses using Overman rearrangement as the key reaction

H. Sato, T. Oishi, N. Chida

<i>Journal of Synthetic Organic Chemistry Japan</i> (The Society of Synthetic Organic Chemistry, Japan)  62 ( 7 ) 693-704 2004

Accepted

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Oxidative total chlorine free photochemical bleaching of cellulosic fabrics

A. Ouchi, H. Sakai, T. Oishi, T. Hayashi, W. Ando, J. Ito

Green Chemistry (Royal Society of Chemistry)  5 ( 5 ) 516 - 523 2003.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  1463-9262

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Water-insoluble natural colored compounds adsorbed or chemically bound on cellulosic fabrics were bleached effectively by a selective photolysis of the colored compounds using various excimer lasers (KrF, XeCl, XeF), a low-pressure mercury lamp, and a black-light fluorescent lamp in the presence of sodium peroxocarbonate or mixtures of sodium carbonate and hydrogen peroxide aqueous solutions at room temperature. The efficiency of the photochemical bleaching was found to be comparable to that of the commercial thermal bleaching processes when a XeF excimer laser or a black-light fluorescent lamp were used as light sources.

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Total synthesis of sphingofungin E from D-glucose

T, Oishi, K. Ando, K. Inomiya, H. Sato, M. Iida, N. Chida

Organic Letters (American Chemical Society)  4 ( 1 ) 151 - 154 2002.12

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

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Total synthesis of sphingofungin E (1) is described. Overman rearrangement of an allylic trichloroacetimidate derived from diacetone-d-glucose generated tetra-substituted carbon with nitrogen, and subsequent Wittig olefination afforded the highly functionalized part in sphingofungin E (4) stereoselectively. Coupling reaction of 4 with the C12 hydrophobic part, followed by further manipulation, completed the total synthesis.

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Total synthesis of (+)-myriocin and (–)-sphingofungin E from aldohexoses using Overman rearrangement as the key reaction

T. Oishi, K. Ando, K. Inomiya, H. Sato, M. Iida, N. Chida

Bulletin of the Chemical Society of Japan (CSJ)  75 ( 9 ) 1927 - 1947 2002.09

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

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Total synthesis starting from aldohexoses of naturally occurring α-substituted α-amino acids, (+)-myriocin (1) and (−)-sphingofungin E (2), is described. Overman rearrangement of allylic trichloroacetimidate 6E derived from D-mannose effectively generated the tetrasubstituted carbon with nitrogen, and subsequent Wittig olefination afforded the highly functionalized moiety 3 of myriocin stereoselectively. Sulfone-mediated coupling reaction of the allyl bromide 3 with C12 hydrophobic part 4 successfully constructed the carbon framework possessing E-olefin 28. Removal of the sulfone and protecting groups completed the chiral and stereoselective total synthesis of (+)-myriocin (1). A similar transformation starting from D-glucose also accomplished the total synthesis of (−)-sphingofungin E (2).

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Stereoselective total synthesis of (+)-myriocin from D-mannose

T. Oishi, K. Ando, N. Chida

Chemical Communications (Royal Society of Chemistry)     1932 - 1933 2001.09

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

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The stereoselective total synthesis of myriocin 1 from D-mannose is described; the carbon framework with three contiguous chiral centers including a tetra-substituted carbon with nitrogen was effectively constructed using Overman rearrangement as the key reaction.

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(2S,3R,4S,5R,6S)-6-Benzyloxymethyl-4-(methoxymethyloxy)-9-oxo-8-oxa-1- azabicyclo[4.3.0]nonane-2,3,5-triyl triacetate

Y. Kani, S. Ohba, T. Oishi, K. Ando, K. Inomiya, N. Chida

Acta Crystallographica (International Union of Crystallography)  C56   e223 2000.05

Research paper (scientific journal), Joint Work, Accepted,  ISSN  2053-2296

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