Usaramine, a new pyrrolizidine alkaloid from Crotalaria usaarmoensis E. G. Baker

Abstract

The major alkaloid, usaramine, of the seed of C. usaramoensis E. G. Baker, is shown to be the geometric isomer of retrorsine; i.e. an ester of retronecine with retronecic acid. Other alkaloids in the seed are integerrimine, traces of senecionine and retrorsine, and two unidentified non-ester bases. The previously reported usaramoensine¹ was not detected and is considered to be a mixture.