Reaction of 18beta,19beta-epoxylupan-21-one derivatives with acids: a way to 21,22-disubstituted lup-18-ene triterpenoids

Abstrakt

Reaction of 18beta,19beta-epoxylupan-21-one derivatives with acids: a way to 21,22-disubstituted lup-18-ene triterpenoids. Depending on the conditions and the acid employed, the title compounds on treatment with acid gave three types of products: a) 28-nr derivatives, b) lupa-12,18-dien-21-ones and c) 22beta-substituted derivatives of 18-lupen-21-one.

The formation of the last type of compounds probably proceeds in the enol form of epoxyketone: opening of the epoxide ring with shift of the double bond o position 19(21) and attack by nucleophilic species at C-22 followed by elimination of water andá data