Extractives of Australian Timbers. II. Emmolic Acid, a new triterpene acid from Emmenospermum alphitonioides F. Muell

Abstract

Extraction of the wood of Emmenospermum alphitonioides F. Muell. yields a saponin, an essential oil, and a free triterpene acid, C₃₀H₄₆O₅, for which the name emmolic acid is proposed. Emmolic acid contains two hindered carboxyl groups, one double bond, and a secondary hydroxyl group which is located in a 5-membered ring in a β-position to one of the carboxyl groups. Chemical and spectroscopic evidence indicates that the double bond, which is easily reducible, is present in an isopropenyl group. Lactone formation involving interaction of a methoxycarbonyl group with the double bond occurs with dimethyl acetylemmolate and dimethyl emmonate. It is concluded that emmolic acid is probably pentacyclic with a carbon skeleton different from that of any of the naturally occurring triterpenes.