Unsaturated E-ring triterpenes from Rubus pinfaensis

Two new isomeric unsaturated E-ring pentacyclic tritelpenoids have been isolated from the roots of Rubus pinfaensis. These triterpenes, glucosides of 2 alpha,3 beta,23-trihydroxyurs-12-en-28-oic acids with additional Delta(18) or Delta(19) unsaturation, were hydrolysed to the previously unreported pinfaenoic and isopinfaenoic acids, which, on acetylation and methylation, were converted into methyl triacetoxy-esters (methyl 2 alpha,3 beta,23-triacetoxyursa-12,18-or -12,19-dien-28-oates), allowing purification and characterization by C-13 and H-1 NMR techniques. The possibility of these triterpenoids arising as artefacts of the isolation process has been addressed.