Tamotsu Fujisawa

Enantiospecific synthesis of optically pure (3s)-hydroxy esters by the stereocontrolled yeast reduction of α-sulfenyl-β-ketoesters

Abstract Stereocontrol in Bakers yeast reduction of β-ketoesters was successfully achieved by introducing the sulfenyl group at α-position of the esters to afford optically pure (S) -β-hydroxy esters.

Switchover of diastereofacial selectivity in the condensation reaction of optically active N-sulfinimine with ester enolate

Both diastereomers of β-aminoester can be obtained diastereoselectively in the reaction of optically active N-sulfinimine possessing 2-methyl-1,3-dioxolanyl group with ester enolate simply by changing the enolate metal species, additives, and solvents. The β-aminoester can be converted into the corresponding 3-unsubstituted β-lactam.

Optically pure (s)-3-phenylthio-1,2-propanediol: synthesis by the yeast reduction and use as a precursor of both enantiomers of secondary alcohols

Abstract Optically pure (S)-3-phenylthio-1,2-propanediol was obtained by the enantioselective reduction of 1-hydroxy-3-phenylthio-2-propanone with the Bakers yeast, and was found to be a convenient precursor for both enantiomers of secondary alcohols, which was demonstrated in the synthesis of both enantiomeric forms of 5-hexadecanolide via phenyl (S)-glycidyl sulfide as the key intermediate.

Asymmetric reduction of α,β-unsaturated ketones with chiral hydride reagents prepared from lithium aluminum hydride and (S)-4-anilino- and (S)-4-(2,6-xylidino)-3-methylamino-1-butanol

Abstract The asymmetric reduction of prochiral α,β-unsaturated ketones with chiral hydride reagents derived from lithium aluminum hydride and (S)-4-anilino- and (S)-4-(2,6-xylidino)-3-methylamino-1-butanol gives (S)- and (R)-allylic alcohols in high chemical and optical yields, respectively.

Selective synthesis of optically active 3-haloazetidin-2-ones or aziridines by the condensation of various metal enolates of α-haloacetate with a chiral imine

Reaction products and their diastereofacial selectivity in the condensation of the ester enolates of α-haloacetate with a chiral imine possessing 1,3-dioxolane ring derived from (2S,3S)-1,4-dimethoxy-2,3-butanediol as a chiral auxiliary can be fully controlled by the metal enolate used; i.e., (3R,4R)-3-haloazetidine-2-one is obtained stereoselectively by the use of the triisopropoxytitanium enolates, while condensation with the lithium or zinc enolates provides (2R,3S)- or (2S,3R)-aziridine, respectively.

Stereocontrol by introduction of a sulfur functional group in the asymmetric reduction of β-ketoesters with baker's yeast: preparation of optically pure 3S-hydroxydithioesters as a new chiral synthon of natural product synthesis

Abstract Asymmetric reduction of β-ketothioester derivatives with bakers yeast produced the corresponding optically pure 3S-hydroxyethioesters, which are useful chiral building blocks in organic synthesis. The utility of the present method was demonstrated in the stereoselective synthesis of sex attractant of pine saw-fly, (2S,3S,7S)-5,7-dimethylpentadec-2-yl acetate from the SS-hydroxy esters.

Stereocontrol in the reduction of 1,2-diimine with an oxazaborolidine catalyst. Highly stereoselective preparation of (R,R)-1,2-diphenylethylenediamine

Abstract Highly enantioselective reduction of 1,2-bis( p -methoxyphenylimino)-1,2-diphenylethane was conducted even with 0.5 mol% of new oxazaborolidine derived form L-threonine and a stoichiometric amount of BH 3 ·THF to give 1,2-diphenylethylenediamine derivative in excellent enantiomeric purity. The subsequent deprotection of nitrogen atoms afforded ( R,R )-1,2-diphenylethylenediamine in enantiomerically pure form.

A stereocontrolled total synthesis of optically active (R,R)-phytol

A stereospecific synthesis of (R,R)-phytol uith highly stereochemioal purity in both absolute and geometrical aonfigurations uas achieved by utilizing the SNZ type ring-opening reaction of (R)-β-methyl-β-propiolactone, and the SNZ′ type ring-opening reaction of isopropenyl oxirane, from (R)-pulegone as a starting material.

A novel synthetic method for optically active terpenes by the ring-opening reaction of (R)-(+)-β-methyl-β-propiolactone

Abstract Optically active terpene such as ( R )-(+)-citronellol, ( R )-(+)-pulegone or ( S )-ar-turmerone is prepared in high enantiomeric excess from an intermediate, ( R )-(+)-citronellic acid or ( S )-(+)-3-p-tolylbutyric acid, which is easily prepared by the S n 2 type of ring opening reaction of ( R )-(+)-β-methyl-β-propiolactone with homoprenylmagnesium bromide in the presence of a copper(I) salt or di-p-tolylcuprate.

Direct and chemoselective conversion of carboxylic acids into aldehydes

Abstract A new method for the direct conversion of carboxylic acids to aldehydes using N,N-dimethylchloromethyleniminium chloride and lithium tri-t-butoxyaluminum hydride was established. This method provides a convenient way for the chemoselective reduction of carboxylic acids even with such a functional group as halide, ester, nitrile, olefin, and ketone.