Studies on terpenoids and steroids. Part 10. Structures of four new natural phenol is D:A-friedo-24-noroleanane triterpenoids

Abstract

The three new phenolic nortriterpenes, demethylzeylasteral, zeylasteral, and demethylzeylasterone, isolated from Kokoona zeylanica(Celastraceae), have been shown to be 2,3-dihydroxy-6,23-dioxo-D:A-friedo-24-noroleana-1,3,5(10),7-tetraen-29-oic acid (5), its methyl ester (6), and 2,3-dihydroxy-6-oxo-D:A-friedo-24-noroleana-1,3,5(10),7-tetraene-23,29-dioic acid (7), respectively. The structure of the new phenolic (9 → 8)-D:A-friedo-24-noroleanane triterpene obtained from ‘kokum soap’ has been established as 23-oxoisopristimerin III (11) on the basis of spectroscopic evidence. The biosynthetic significance of 23-oxoisopristimerin III is discussed.