Enantiospecific synthesis of (+)- and (–)-trachelanthic acids via asymmetric dihydroxylation and their conversion to the pyrrolizidine alkaloids indicine and intermedine

Abstract

Asymmetric dihydroxylation of (E)-ethyl 2-isopropylbut-2-enoate with AD-mix-α and AD-mix-β, followed by saponification, gives (–)- and (+)-trachelanthic acids, respectively, which are each coupled via their acetonides with (+)-retronecine to yield the pyrrolizidine alkaloids indicine and intermedine.