Methylation of 1 Followed by Methanolysis. To a solution of 1 (2 mg) in dry acetone (1 mL) were added Me2SO4 (10 µL) and K2CO3 (10 mg), and the mixture was stirred overnight at room temperature and then refluxed for 2 h. After centrifugation, the supernatant was evaporated and the reac- tion mixture was directly methanolyzed in 2% NaOMe in MeOH (1 mL) at room temperature for 8 h. After acidification with acetic acid and removal of the solvent, the residue was further treated with CH2N2 in Et2O (1 mL) for 2 h and the solvent was evaporated. The residue was redissolved in MeOH and analyzed by reversed-phase HPLC (solvent D), which showed the production of methyl tri-O-methylgallate (9) and trimethyl octa-O-methylvaloneate (10).
Partial Hydrolysis of 1. An aqueous solution (1 mL) of 1 (1 mg) was heated in a boiling water bath for 1 h. The reaction mixture was analyzed by normal- and reversed-phase HPLC (solvent B) to show the peaks due to 2,3,6-tri-O-galloyl-D- glucose (14) and rugosin A (15).