NEW CASSANE DITERPENES FROM CAESALPINIA BONDUC (FABACEAE)

New cassane diterpenes, neocaesalpins A and B, were isolated from the seeds of Caesalpinia bonduc (Fabaceae) and their structures were deduc ed on the basis of the spectroscopic evidence. These compounds are cha racterized as having an alpha,beta-butenolide moiety whereas caesalpin s, a group of diterpenes previously known from the same plant and rela ted species, possess the furan ring. The possible biogenetic scheme fo r formation of an alpha,beta-butenolide was postulated as the furan ri ng undergoing peroxidation followed by isomerization to give rise to t he hemiketal lactone.