New phenolic triterpenes from Maytenus blepharodes.: Semisynthesis of 6-deoxoblepharodol from pristimerin

Four new phenolic triterpenes with a 24-nor-D:A-friedoleane skeleton, isoblepharodol, 7-oxoblepharodol, blepharotriol and 6-deoxoblepharodol, were isolated from Maytenus blepharodes. Their structures were elucidated on the basis of spectroscopic analysis, including homo and heteronuclear correlation NMR experiments (COSY, ROESY, HSQC, and HMBC). The semisynthesis of 6-deoxoblepharodol and its epimer at C-8 was achieved by catalytic reduction of pristimerin, a quinone-methide triterpene present in the plant. The biosynthetic formation of the phenolic triterpenes isolated from this species is also discussed. The compounds were assayed for antimicrobial and cytotoxic activities. (C) 2005 Elsevier Ltd. All fights reserved.