Takehisa Inoue

Reductive desulfurization using the raney nickel — Sodium hypophosphite combination system without racemization of a secondary alcohol

Abstract Thioethers bearing an optically active secondary alcohol were desulfurized with Raney nickel — sodium hypophosphite — acetate buffer system to give optically active alcohols without racemization in high yields. This Raney nickel combination system exhibited a unique desulfurization of benzylthio or phenylthio group in the presence of benzyl ether.

Total asymmetric syntheses of (+)-blastmycinone and related γ-lactones

Abstract The freeze of the conformer was realized by the introduction of an alkyl substituent at α-position of tetronic acid using a readily available none C2 chiral auxiliary (SMP or RMP), and conducted the desired asymmetric γ-methylation. Its application to expeditious total syntheses of (+)-blastmycinone (1) and (−)-3-epi-blastmycinone (2), and to the first total synthesis of (+)-(3R,4R,5R)-4-acetoxy-5-methyl-3-tetradecyltetrahydro-2(5H)-furanone (3) was described.

Enantioselective reduction of σ-Symmetric bicyclo[3.3.0]octane-2,8-diones with baker's yeast

Abstract σ-Symmetric bicyclic diketones 8a-c were enantioselectively reduced with bakers yeast to give the chiral hydroxy ketones 7a-c in 74–;100% ee. The reduction product (+)-7a and (−)-7′c were shown to be the chiral intermediates for the total synthesis of cantabrenonic acids derivatives 3 and hirsutene (4), respectively. The subsequent transformation of (+)-7a gave the intermediate (+)-5 for the total synthesis of capnellenols (1, 2).

Exo selective Diels–Alder reaction of nitroolefins with Danishefsky's diene

Diels–Alder reaction of nitroolefins with Danishefskys diene exhibit abnormal exo selectivity based on electrostatic repulsion between the nitro group and the silyloxy group of diene.

An improved asymmetric nitroolefination of α-alkyl-γ- and δ-lactones with modified nitroenamines

Abstract New chiral nitroenamines 4a,b were found to be very effective for asymmetric nitroolefination of α-alkyl-γ- and δ-lactones. The enantiomeric excess of the product ran up to 99 %. A possible chelation model for the transition state of the asymmetric nitroolefination was discussed.

An Asymmetric Nitroolefination of α-Alkyl-γ-and δ-Lactones with Modified Nitroenamines

Abstract New chiral nitroenamines 4a,b having ( S )-2- t -butyldimethylsiloxymethylpyrrolidine as an auxiliary were found to be very effective for asymmetric nitroolefination of α-alkyl-γ- and δ-lactones. The enantiomeric excess of the product increased remarkably in the reaction with γ-lactones compared with previous nitroenamines 1a,b . A possible chelation model for the transition state of the asymmetric nitroolefination is discussed.

An asymmetric synthesis of C2-symmetric dimethyl 3,7-dioxo-cis-bicyclo[3.3.0]octane-2,6-dicarboxylate by lipase-catalyzed demethoxycarbonylation

Both enantiomers of C2-symmetric dimethyl 3,7-dioxo-cis-bicyclo[3.3.0]-octane-2,6-dicarboxylate (3) were prepared in enantiomerically pure form by the lipase-catalyzed demethoxycarbonylation, respectively. An expeditious formal total synthesis of (+)-carbacyclin using this hybrid process was done.

Lipase-catalyzed asymmetric demethoxycarbonylation: Formal syntheses of (+)-carbacyclin, (−)-ajmalicine, and (−)-tetrahydroalstonine

Abstract Both enantiomers of C 2 -symmetric dimethyl 3,7-dihydroxybicyclo[3.3.0]-octa-2,6-diene-2,6-dicarboxylate 3 were prepared in enantiomerically pure form from symmetric tetraester 1 by the lipase-catalyzed demethoxycarbonylation, respectively. Double asymmetric differentiation with lipase in the above demethoxycarbonylation was observed. Their applications to formal total syntheses of (+)-carbacyclin and (−)-ajmalicine including (−)-tetrahydroalstonine are also described.