New corynanthé alkaloids from Strychnos angustiflora

Abstract

Three alkaloids isolated from Strychnos angustiflora, angustoline, angustine, and angustidine, have, respectively, the corynanthé structures (1) and (2), and the 21-norcorynanthé structure (5). They differ in the nature and position of side-chains on a fused pyridine ring. 1H N.m.r. long-range coupling data have been used in arriving at the structures. The biogenetic relationship between the alkaloids is discussed.