Diastereoselective synthesis of butenolides

Abstract

The approaches for the construction of chiral 4-substituted butenolide and butanolide were developed by exploitation of the stereo-differentiating reactions as the following three main reaction types: 1) Enantiomer-differentiating reaction The strategy, based on kinetic controlled reaction, was purposed that one of the enantiomers of chiral epoxide could be differentiated during a Reformasky reaction with an optically active a-bromoacetate ester or reaction with an optically active enolate anion of malonate ester, leaving the other enantiomer of the epoxide, thus producing only one of the optically active adducts. 2) Double-stereodifferentaiting reaction Condensations of chiral ketone with either achiral or chiral alkynoate anion to synthesize an optically active 4-substituted butenolide were studied; the inherent diastereoface preferences of the two reactants may reinforce one another (consonant double stereodifferentiation) or oppose one another (dissonant double stereodifferentiation). 3) Diastereoface-differentiationreaction The strategy, based on collaboration of chirality of a-ketoester together with the roles of trimethylsiloxyfuran and catalyst toward diastereofacedifferentiation in the synthesis of chiral butenolide. The retrosynthesis analysis of the synthetic approach is outlined in Scheme A.