Isolation and synthesis of a new bioactive ellagic acid derivative from Combretum yunnanensis.

A new ellagic acid derivative (1) was isolated from the branches of Combretum yunnanensis, and its structure was assigned as 4-(4' '-O-acetyl-alpha-rhamnopyranosyl)ellagic acid by analysis of its spectral data. Total synthesis of 1 was achieved by the glycosylation of 3,3'-di-O-benzylellagic acid (5) with 4-O-acetyl-2,3-di-O-benzyl-l-rhamnose (4) as a key reaction, and the absolute configuration of 1 was determined. Compound 1 showed weak inhibitory activity against the growth of various tumor cells and inhibited HIV-1 protease.