Takefumi Momose

A new asymmetric entry to 2-substituted piperidines. A concise synthesis of (+)-coniine, (−)-pelletierine, (+)-δ-coniceine, and (+)-epidihydropinidine

Abstract A new asymmetric route to 2-substituted piperidines involving the Sharpless asymmetric dihydroxylation (AD) of 5-hexenylazide 1 and an intramolecular aminocyclization as crucial steps and its application to the asymmetric synthesis of four piperidine alkaloids, (+)-coniine 2 , (−)-pelletierine 3 , (+)-δ-coniceine 4 , and (+)-epidihydropinidine 5 is presented.

An efficient synthesis of (-)-bulgecinine

Abstract A highly stereoselective synthesis of (-)-bulgecinine ( 1 ) via the pyrrolido[1,2- c ]oxazolidin-3-one system ( 2 ) has been achieved by starting with the asymmetric epoxidation of the twin allyl alcohol system ( 6 ). The transformation of note includes the palladium-catalyzed N →π cyclization leading exclusively to a trans -2,5-disubstituted pyrrolidine.

Indium-Mediated Reaction of 3-Bromo-3,3-difluoropropene and Bromodifluoromethylacetylene Derivatives with Aldehydes

Abstract Aldehydes reacted with 3-bromo-3,3-difluoropropene at the α-position in the presence of indium to afford 1-substituted-2,2-difluorobut-3-en-1-ols. Ketones and other electrophiles are inert under the examined conditions. The reaction of bromodifluoromethylacetylene derivatives with an aldehyde in the presence of indium provided difluorohomopropargylic alcohols. These reactions efficiently proceeded in polar solvents (water, DMF) under mild conditions.

New synthesis of all the four stereoisomers of indolizidine 209D and their affinity for nicotinic acetylcholine receptor

Abstract Both enantiomers of a 2-(4-pentenyl)pyrrolidine derivative 4 (65–90% ee ), prepared via the asymmetric dihydroxylation (AD) of terminal olefin 2 , underwent a second AD to provide all of the four stereoisomers of indolizidine 209D 1 with enantiomeric enhancement (92–98% ee ). The affinity of 1 for nicotinic acetylcholine receptor was evaluated.

Enantio- and diastereodivergent synthesis of all four diastereomers of the 2,6-disubstituted 3-piperidinol chiral building block

Abstract Enantio- and diastereodivergent synthesis of all four diastereomers of 2,6-disubstituted 3-piperidinol has been achieved. The versatility of these compounds as the chiral building block for alkaloid synthesis has been demonstrated both by total synthesis of iso-6-cassine and by formal synthesis of prosopinine, cassine, and spectaline.

New entry to chiral butenolide synthons. Application to expeditious syntheses of (+)-nephrosteranic acid, (+)-trans-whisky lactone, and (+)-trans-cognac lactone

A new entry to chiral butenolide synthons starting with iodolactonization of the readily available, homochiral N-benzyl-N-methyl-3-hydroxy-4-pentenamide (1) and its application to the syntheses of (+)-nephrosteranic acid (5), (+)-trans-whisky lactone (6), and (+)-trans-cognac lactone (7) are described.

A general asymmetric route to trans- or cis-2,6-disubstituted piperidine. First total synthesis of (+)-9-epi-6-epipinidinol and (−)-pinidinol

Abstract Starting from 1,6-heptadiene, two AD reactions in a stepwise manner lead to the anti-1,5-diol and syn-1,5-diol stereodivergently, which have been converted by aminocyclization into trans- and cis-2,6-disubstituted piperidines (trans- and cis-12), respectively. The first total synthesis of (+)-9-epi-6-epipinidinol (2) and (−)-pinidinol (3) has been achieved from trans- and cis-12.

Efficient fragmentation of the tertiary cyclopropanol system: Oxidation of 1-(trimethylsiloxy)bicyclo[n.1.0]alkanes and analogues by using phenyliodine(III) diacetate

Abstract Oxidation of 1-(trimethylsiloxy)bicyclo[n.1.0]alkanes and analogues with phenyliodine(III) diacetate (PIDA) in acetic acid caused fragmentation to give alkenoic acids in high yields.

An efficient route to chiral trans-2,5-dialkylpyrrolidines via stereoselective intramolecular amidomercuration

Abstract An intramolecular amidomercuration of α-butylated 4-pentenylcarbamate 5 predominantly provided trans -2,5-disubstituted pyrrolidine 6 , which was elaborated to chiral trans -5-butyl-2-alkylpyrrolidines 10 and 13 , constituents of ant venoms.

A short, practical synthesis of the ant venom alkaloid, three (3R,5S,8aS)-3-alkyl-5-methylindolizidines

Abstract A short, practical and diastereoselective method for preparing the ant venom alkaloid, three (3R,5S,8aS)-3-alkyl-5-methylindolizidines (1–3), has been developed. The stereoselective intramolecular amidomercuration of the N-alkenylurethane 4 followed by oxidative demercuration provides the piperidine alcohol cis-6 as a major product. Thereafter, oxidation of cis-6 followed by the Horner-Emmons elongation of the ring appendages affords the enones 8, 10, and 11, which are stereoselectively converted into 1, 2, and 3, respectively, by catalytic hydrogenation.