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

(±)-7- O -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- O -methylflavan 6 followed by acylation and reduction. However, the demethylation of flavan 6, 5- O -acetylflavan 10 and 5- O -phenylacetylflavan 11 by BBr 3 gave all the hydrolyzed fragments 7 and 8 as the major products. By contrast, in the same condition, hept- O -methylflavan 9 could provide the desired product (±)-7- O -galloyltricetiflavan (1a) in 91% yield. The additional 5- O -B-Br 2 complex may stabilize the ester bond during the demethylation process.