Organocatalytic asymmetric oxy-Michael addition to a gamma-hydroxy-alpha,beta-unsaturated thioester via hemiacetal intermediates

We report an asymmetric oxy-Michael addition to a gamma-hydroxya, alpha,beta-unsaturated thioester via hemiacetal intermediates in the presence of Cinchona-alkaloid-thiourea-based bifunctional organo-catalysts. This method provides a novel enantioselective route to beta-hydroxy carboxyl compounds, which in turn can be used to synthesize valuable chiral building blocks.