Asymmetric synthesis of functionalized pyrrolizidines by an organocatalytic and poteconomy strategy

摘要

An efficient method has been developed for the enantioselective synthesis of tetrahydro-1H-pyrrolizin-3(2H)-ones starting from alpha, beta-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.