The pyrrolizidine alkaloids of Senecio triangularis

Abstract

Methanolic extracts of Senecio triangularis Hook. (Compositae) gave a substantial amount of senecionine* (1) and small amounts of six other pyrrolizidine alkaloids, integerrimine* (2), platy-phylline* (3), rosmarinine* (12), retrorsine* (ll), and two new alkaloids, triangularine* (5) and neotriangularine* (6). The structures of the new alkaloids were determined by carbon and proton nuclear magnetic resonance and electron imoact and chemical ionization mass spectrometry. Triangularine is 7-[(Z)-2-methylbut-2-enoyl]-9-[(Z)-2-hydroxymethylbut-2-enoyl]retronecine aid neotriangularine is 7-[(Z)-2-methylbut-2-enoyl]-9-[(E)-2-hydroxymethylbut-2-enoyl]retronecine.