The Cardiac Glycosides of Gomphocarpus fruticosus R.Br. II. Gomphoside

Abstract

Gomphoside is the second glycoside which has been isolated from Gomphocarpus fruticosus R.Br. grown in Australia. This compound analyses for the formula C₂₉H₄₄O₈ and contains neither methoxyl nor acetyl groups, but forms a diacetate, C₃₃H₄₈O₁₀, which is unstable to chromium trioxide in acetic acid. Although gomphoside gives a negative Keller-Kiliani reaction, a quantitative oxidation by periodic acid indicates the presence of two free adjacent hydroxyl groups in the molecule. Hydrolysis of gomphoside gives gomphogenin, C₂₃H₃₄O₅, which does not give a colour reaction with tetranitromethane. The acetylation of gomphogenin yields acetylgomphogenin, C₂₅H₃₆O₆, which is unstable to chromium trioxide in acetic acid. Gomphoside and its derivatives have ultraviolet and infra-red absorption spectra typical of those of the normal digitaloid compounds. The reactions which have been carried out on these substances indicate the presence of an hydroxyl group in gomphogenin, besides the normal hydroxyl groups at C₃ and C₁₄, which is resistant to acetylation, but which can be oxidized by chromium trioxide in acetic acid. The nature of the carbohydrate is as yet unknown.