To a hazy suspension of Dess Martin periodinane (1 g, 2.295 mmol) in dry methylene chloride (10 mL) was added a solution of trans 3-flavanol 6 (0.8 g, 1.53 mmol) in methylene chloride (10 mL) at room temperature. The resulting purple solution was stirred at room temperature for 4 h, after which it was poured into a saturated solution of sodium bicarbonate (60 mL) containing 7 equivalents of sodium thiosulfate (16.06 mmol, 3.98 g) and stirred for 10 minutes. The resulting brown solution was extracted with methylene chloride and the organic layer washed with water and brine, and dried (MgSO4). The filtered solution was then evaporated to afford the crude 3-flavanone 7, which was purified by flash chromatography, using hexanes: ethyl acetate (95:5 to 8:2) to afford 0.432 g (53%) of pure product as a thick, colorless oil. TLC: hexanes: methylene chloride: ethyl acetate (3:1:1): Rf=0.39; 1H NMR (300 MHz, CDCl3): δ 3.60 (dd, 2H, 4-Hα and β), 3.79 (s, 6H, OCH3), 3.82 (s, 3H, OCH3), 5.02 (s, 2H, OCH2Ph), 5.04 (s, 2H, OCH2Ph), 5.29 (s, 1H, 2-H), 6.32 and 6.41 (2d, 2H, 6, 8-Ar—H), 6.58 (s, 2H, 2′,6′-Ar—H), 7.37–7.40 (m, 10H, Ar—H).
