A general asymmetric route for the synthesis of the alexine and australine family of pyrrolizidine alkaloids. The first asymmetric synthesis of 1,2- diepi-alexine and 1,2,7- triepi-australine

Abstract

The first asymmetric synthesis of 1,2- diepi-alexine and 1,2,7- triepi-australine (both are unknown at present) is described, which utilized the regioselective asymmetric aminohydroxylation (RAA) reaction of the achiral olefin VI , the cross metathesis (CM) reaction of the terminal olefin 8 , and the formation and subsequent intramolecular double cyclization (DC) reactions of the epoxides 10 and 11 . The C1 stereocenter was diastereoselectively introduced by the reaction of the aldehyde 7 with vinylmagnesium bromide.