Asymmetric synthesis of functionalized pyrrolizidines by an organocatalytic and pot-economy strategy

Abstract

An efficient method has been developed for the enantioselective synthesis of tetrahydro-1H-pyrrolizin-3(2H)-ones starting from α,β-unsaturated aldehydes via a sequence of asymmetric Michael–oxidative esterification–Michal–reduction–reductive amination–lactamization reactions with high enantioselectivities (93–97% ee). The six-step reaction sequence can be conducted with the pot-economy synthetic strategy with only a one-step purification. The structure and absolute stereochemistry of the intermediates and products were confirmed by X-ray analyses of appropriate products.