Masatoshi Asami

A Novel Highly Effective Chiral Lithium Amide for Catalytic Enantioselective Deprotonation of meso-Epoxides

Abstract A highly enantioselective deprotonation of meso -epoxides was achieved by a catalytic amount of a new chiral lithium amide, derived from (2 S ,3a S ,7a S )-2-(pyrrolidin-1-ylmethyl)octahydroindole, in the presence of excess lithium diisopropylamide to afford the corresponding allylic alcohol derivatives up to 94% ee.

Catalytic enantioselective deprotonation of meso-epoxides by the use of chiral lithium amide

Abstract Catalytic enantioselective deprotonation of meso-compound is achieved for the first time by the combined use of a catalytic amount of chiral lithium amide, lithium (S)-2-(pyrrolidin-1-ylmethyl)pyrrolidide, and excess lithium diisopropylamide in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene.

An asymmetric synthesis of cis-4-t-butyldimethylsiloxy-2-cyclopenten-1-ol and cis-4-tetrahydropyranyloxy-2-cyclopenten-1-ol, versatile chiral synthetic intermediate for prostanoids

cis-4-t-Butyldimethylsiloxy-2-cyclopenten-1-ol and cis-4-tetrahydropyranyloxy-2-cyclopenten-1-ol were obtained with high enantiomeric excesses (ee) by the reaction of cis-3,4-epoxycyclopentan-1-ol derivatives with chiral lithium amide. An application to the syntheses of both (S)- and (R)-4-hydroxy-2-cyclopentenone was demonstrated.

An asymmetric synthesis of (-)-carbovir

Abstract Enantioselective deprotonation of trans -4- t -butyldimethylsiloxymethyl-1,2-epoxycyclopentane ( trans - 4 ) by a chiral lithium amide, lithium ( S )-2-(pyrrolidin-1-ylmethyl)pyrrolidide ( 1 ), afforded (1 S ,4 S )- trans -4- t -butyldimethylsiloxymethyl-2-cyclopenten-1-ol ( trans - 7 ) in 83 %ee. Alcohol trans - 7 was easily transformed to (−)-carbovir, an anti-HIV carbocyclic nucleoside.

Enantioselective addition of dialkylzinc to aldehydes catalyzed by (S)-2-(N,N-disubstituted aminomethyl)indoline

Abstract Chiral di- or triamines, ( S )-2-( N , N -disubstituted aminomethyl)indoline 1a – d , derived from ( S )-indoline-2-carboxylic acid were efficient chiral catalysts for the enantioselective addition of dialkylzincs to aldehydes. The best results were obtained by employing 15 mol% of ( S )-2-(4-methylpiperazin-1-ylmethyl)indoline 1c , and chiral secondary alcohols were obtained in up to 97% ee.

Catalytic asymmetric borane reduction of prochiral ketones by the use of diazaborolidine catalysts prepared from chiral β-diamines

Abstract The catalytic asymmetric borane reduction of prochiral ketones was examined in the presence of chiral diazaborolidine catalysts prepared in situ from chiral β-diamines and borane. Chiral secondary alcohols were obtained with modest to high enantiomeric excesses (up to 92% ee) using ( S )-2-[(4-trifluoromethyl)anilinomethyl]indoline 2f .

RECONFIRMATION OF HIGH ENANTIOMERIC EXCESSES IN THE ENANTIOSELECTIVE TRANSFORMATION OF MESO-EPOXIDES

Abstract Our previous results on the transformation of maso -epoxide 4- t -butyldimethylsiloxy-1,2-epoxycyclopentane by chiral lithium amide, lithium ( S )-2-(pyrrolidin-1-ylmethyl)pyrrolidide, were fully reconfirmed to be highly enantioselective.

A CONCISE ASYMMETRIC SYNTHESIS OF (-)-UNTENONE A

Abstract Untenone A, a new cyclopentenone derivative isolated from an Okinawan marine sponge Plakortis sp., was synthesized in the optically active form applying the enantioselective deprotonation of meso-epoxide in the key step.

Catalytic enantioselective rearrangement of meso-epoxides mediated by chiral lithium amides in the presence of excess cross-linked polymer-bound lithium amides

Insoluble polymer-bound achiral lithium dialkylamides were prepared from the corresponding cross-linked polymer-bound amines and butyllithium. The polymer-bound achiral reagent was applied to a catalytic enantioselective rearrangement of meso-epoxides as an in situ regenerating agent of a chiral lithium amide. The efficiency of the catalytic system was improved, and chiral allylic alcohol derivatives were obtained in high enantiomeric excesses by using excess polymer-bound reagents and a sub-stoichiometric amount of chiral lithium amide, prepared from (2S,3aS,7aS)-2-(pyrrolidin-1-ylmethyl)octahydroindole. The reaction was successfully applied in the synthesis of (1S,4R)-4-benzoylamino-2-cyclopentenol, a useful chiral synthetic intermediate for carbocyclic nucleosides, in 97% ee.

A kinetic resolution of racemic epoxides by a chiral lithium amide

Abstract A kinetic resolution of cis -disubstituted epoxides was effectively achieved by a chiral lithium amide, prepared from ( S )-2-(pyrrolidin-1-yl)-methylpyrrolidine.