The first total synthesis of 7-O-β-D-glucopyranosyl-4′-O-α-L-rhamnopyranosyl apigenin via a hexanoyl ester-based protection strategy

The first total synthesis of 7-O-beta-D-glucopyranosyl-4 '-O-alpha-L-rhamnopyranosyI apigenin 1, which exhibits good anti-hepatitis B virus and anti-stroke activities, was accomplished in six steps and 20% overall yield from apigenin. Another synthetic route, in which the target was obtained in seven steps, was also developed to prove the utility of a hexanoyl ester-based orthogonal protection strategy. The hexanoyl protection strategy provided all the flavonoid intermediates with good solubility and reactivity, enabled efficient selective protection and glycosylation, and provided a practical and effective synthetic strategy for flavonoids, starting from commercially available flavone. (C) 2008 Elsevier Ltd. All rights reserved.