Asymmetric construction of quaternary carbons from chiral malonates: selective and versatile total syntheses of the enantiomers of .alpha.- and .beta.-cuparenones from a common optically active precursor.

Abstract

From a single chiron (R)-4, available with high enantiomeric purity (96%) by simple enzymatic hydrolysis (PLE) of a prochiral malonate, were prepared convenient precursors of the two enantiomers of α- and β-cuparenones (1a,b and 2a,b). This versatile method also allows preparations of the enantiomer (S)-4 and dimethyl 2-methyl-2-p-tolylsuccinate ((S)-9a), as well as the new butyrolactones (R)-15, (R)-23, and (S)-25, the new but-3-enolide (S)-32, and cyclopentenones (S)-22 and (S)-30, all these compounds bearing an asymmetric quaternary carbon