Masayuki Kirihara

A novel biogenetic type synthesis of (+)-hydantocidin

Abstract The title synthesis was accomplished by featuring the proposed biosynthetic pathway. The synthesis commenced with the D-psicose derivative readily obtainable from D-fructose and employed intramolecular N, O-spiroketal formation of the open-chain N-acylurea derivative as a key step.

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.

Efficient synthesis of (R)- and (S)-1-amino-2,2-difluorocyclopropanecarboxylic acid via lipase-catalyzed desymmetrization of prochiral precursors

The asymmetric syntheses of (+)-(R)-1-amino-2,2-difluorocyclopropane-1-carboxylic acid and its enantiomer have been accomplished. Key reactions in the synthetic design are lipase-catalyzed desymmetrization of a prochiral diol and a prochiral diacetate.

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.

α,α-difluoroallyl carbanion: Indium-mediation in its facile coupling with aldehydes

Indium-mediated coupling of aldehydes with 3-bromo-3,3-difluoropropene gives 1-substituted-2,2-difluorobut-3-en-1-ols in high yields at room temperature. The coupling takes place at the gem-difluorocarbon selectively. Ketones are inert under the conditions examined.

Hypervalent λn-iodane-mediated fragmentation of tertiary cyclopropanol systems

Abstract The oxidation of tertiary cyclopropyl silyl ethers with hypervalent λn-iodanes caused fragmentation which produced alkenoic acids or esters.

Novel synthesis of (+)-hydantocidin based on the plausible biosynthetic pathway

Abstract The title synthesis was examined by employing two synthetic schemes which feature N,O-spiroketal formation as a key step. Although the stepwise synthesis starting with D-fructose and proceeding through the D-psicose derivatives successfully produced a mixture of (+)-hydantocidin (1) and its C5-epimer [(−)-5-epihydantocidin (2)] the one-step synthesis utilizing D-isoascorbic acid and urea as starting materials was found to give 2 more selectively than 1. Studies on the key N,O-spiroketal formation and epimerization between 1 and 2 were also carried out to explore some novel aspects of the obtained results.

Efficient synthesis of an enantiomeric pair pinpinidine: An illustration of organochemical carving on the rigid bridged system as the stereochemical tactics

Abstract Asymmetric synthesis of (−)-pinidine and its enantiomer was accomplished by starting from norgranatar one via the asymmetric enolization, stereoselective cyclopropanation, and oxidative ring cleavage of the resulting cyclopropanol system with a hypervalent iodoid as key steps.

Hypervalent λn-iodane-mediated fragmentation of tertiary cyclopropanol systems II: Application to asymmetric syntheses of piperidine and indolizidine alkaloids

Abstract The asymmetric synthesis of (−)-pinidine and its enantiomer was accomplished by starting from norgranatanone via the asymmetric enolization, stereoselective cyclopropanation, and oxidative ring cleavage of the resulting cyclopropanol system with a hypervalent λ n -iodane as key steps. Formal asymmetric synthesis of (+)-indolizidine 223AB was also performed via the asymmetric enolization and oxidative ring cleavage of the resulting cyclopropanol system as key steps.

Aerobic oxidation of α-hydroxycarbonyls catalysed by trichlorooxyvanadium: efficient synthesis of α-dicarbonyl compounds

α-Hydroxycarbonyls were efficiently oxidized into α-dicarbonyls using a catalytic amount of trichlorooxyvanadium under an oxygen atmosphere.