Anomeric selectivity and influenza A virus inhibition study on methoxylated analogues of Pentagalloylglucose

Anomeric selectivity in galloylation of D-glucose and D-mannose with carboxylic acid was explored under steglich conditions. Base catalyst 4-dimethylaminopyridine favored the formation of alpha-anomers, while adding an acid and carbodiimide favored the formation of beta-anomers. Steric hindrance between α,β-unsaturated acid and C-2 OH stereochemistry (adjacent carbon to anomeric) influenced anomeric selectivity for both D-glucose and D-mannose. The influenza A virus inhibition activities of the synthesized compounds were evaluated in Madin-Darby canine kidney cell line using the cytopathic effect inhibition assay. All the synthetic methoxylated analogues showed more considerable activity against influenza A virus than their corresponding acids, which indicated the sugar core as key functionality for anti-viral activity. The activities of trimethoxy-cinnamic acid Pentagalloylglucose analogues, 3α, 3β, 4α, and 4β (IC50, 109.1 μM, 134.4 μM, 119.5 μM, 111.1 μM, respectively) were better than those of trimethoxy-benzoic acid Pentagalloylglucose analogues, 1-αβ and 2α, 2β (IC50, 209.8 μM, 132.9 μM, 161.2 μM, respectively), which suggested that the double bond in cinnamic acid Pentagalloylglucose analogues makes the major contribution for influenza A virus inhibitory activity. Notably, several anomeric mixtures showed better activities than pure alpha or beta anomer and were almost two times more effective than Ribavirin, a clinically used anti-viral drug.