Six Natural Phenylethanoid Glycosides: Total Synthesis, Antioxidant and Tyrosinase Inhibitory Activities

Abstract

Total synthesis of six natural phenylethanoid glycosides (PhEGs) has been accomplished. Key steps in the divergent synthesis strategy involved glycosylation based on trichloroacetimidate donors, and one‐pot removal of benzyl and 4,6‐O‐benzylidene acetal groups by hydrogenation over Pd/C. Among them, four natural PhEGs, scroside D (2), rebouoside B (3), ginkgoside C (4), and ginkgoside D (5) were synthesized for the first time. In the subsequent antioxidant and tyrosinase inhibitory activities evaluation, all compounds showed strong DPPH radical scavenging activities, and compounds 1–2, 5–6 exhibited obvious inhibitory activities against mushroom tyrosinase.

Concise Synthesis of Eutigoside C

“…However, the development of PhGs has been severely limited by the fact that most of them can only be isolated in small amounts from natural sources. 6,7 Besides, there are also some difficulties associated with total synthesis of PhGs because of the incompatibility of common hydroxyl protecting groups with the phenylpropenic ester group. 8 For example, the removal of benzyl ether protecting groups by hydrogenolysis or acetyl protecting groups by hydrolysis would result in reduction or migration of the cinnamoyl moieties, respectively.…”

“…The residue was purified by silica gel column chromatography to obtain 3 (4.25 g, 60%) as a white solid. (7). To a solution of glucopyranoside 6 (0.76 g, 1.13 mmol) in THF (15 mL), TBAF•3H2O (1.07 g, 3.40 mmol) was added.…”