First examples of tetracyclic triterpenoids with a D:B-friedobaccharane skeleton.A tentative biosynthetic route

摘要

Baruol (1) and Leonal (2),first examples of tetracyclic triterpenes possessing a D:B-friedobaccharane skeleton,were isolated from Maytenus blepharodes and M.chiapensis,respectively.Their structures were established by spectroscopic analysis,molecular modeling studies and biogenetic background.The implication of theD:B-friedobaccharenyl cation in the biosynthetic route of baccharane and shionane skeletons is discussed.Baruol exhibited beta-glucuronidase inhibitory activity,a target in the search for hepatoprotective agents.