Studies on terpenoids and steroids. Part 19. Structures of three novel 19(10→9)abeo-8α,9β,10α-euphane triterpenoids from Reissantia indica(Celastraceae)

The three novel 19(10→9)abeo-8α,9β,10α-euphane (reissantane) triterpenoids isolated from Reissantia indica(Celastraceae) and related to reissantioloxide (reissantenol oxide)(1) have been shown to be 24-oxoreissant-5-ene-3β,25-diol (2), 3-oxoreissant-5-ene-24β,25-diol (3), and reissant-5-ene-3β,24β,25-triol (4). A possible biosynthetic relationship for reissantane, D : B-friedo-oleanane, D : A-friedo-oleanane, and quinone-methide triterpenoids which occur in R. indica is presented.