A concise synthesis of (±)-7--galloyltricetiflavan.

(±)-7--galloyltricetiflavan (1a) was synthesized successfully in five steps from the commercially available trihydroxyacetophenone (2) and trimethoxybenzoyl chloride (3). The flavone 4a was prepared in a one-pot reaction and it gave hex--methylflavan 6 followed by acylation and reduction. However, the demethylation of flavan 6, 5--acetylflavan 10 and 5--phenylacetylflavan 11 by BBr gave all the hydrolyzed fragments 7 and 8 as the major products. By contrast, in the same condition, hept--methylflavan 9 could provide the desired product (±)-7--galloyltricetiflavan (1a) in 91% yield. The additional 5--B-Br complex may stabilize the ester bond during the demethylation process.