Studies on terpenoids and steroids. Part 1. Structures of six novel 27-hydroxy and 6β-hydroxy di- and tri-oxygenated D : A-friedo-oleanane triterpenes from Kokoona zeylanica
The benzene extract of the inner stem bark of Kokoona zeylanica Thwaites (Celastraceae) contains twelve D : A-friedo-oleananes of which nine are new. The new triterpenes have been classified under three series; kokoonol (3,27-dioxy and 3,21,27-trioxy), zeylanol (3,6-dioxy and 3,6,21-trioxy), and kokzeylanol (3,6,27-trioxy and 3,6,21,27-tetraoxy). Six of these triterpenes belonging to the kokoonol and zeylanol series have been identified as 27-hydroxy-D : A-friedo-oleanan-3-one (4)(kokoonol), 27-hydroxy-D : A-friedo-oleanane-3,21-dione (5)(kokoononol), 21α,27-dihydroxy-D : A-friedo-oleanan-3-one (6)(kokoondiol), 6β-hydroxy-D : A-friedo-oleanan-3-one (21)(zeylanol), 6β-hydroxy-D : A-friedo-oleanane-3,21-dione (22)(zeylanonol) and 6β,21β-dihydroxy-D : A-friedo-oleanan-3-one (23)(zeylandiol), by spectroscopic methods and chemical interconversions. The biosynthetic significance of 6-hydroxy-D : A-friedo-oleananes is discussed.