First and efficient synthesis of 4-(3,4-dihydroxybenzoyl-oxymethyl)-phenyl-O-β-D-glucopyranoside, an antioxidant from Origanum vulgare

Abstract

4-(3,4-Dihydroxybenzoyloxymethyl)phenyl-O-β-D-glucopyranoside (DBPG, 1 ), a polyphenolic glycoside previously isolated from Oregano (Origanum vulgare L.) in 0.08 % isolated yield, was synthesized in five chemical steps with 41.4 % overall yield. First, 4-(hydroxymethylphenyl)-2,3,4,6-tetra-O-acetyl-b-D-glucopyranoside 4 was obtained in 53.2 % yield by selective glycosylation of 4-hydroxybenzyl alcohol 3 with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide 2 in a mixture of chlorobenzene and aqueous CsOH using triethylbenzylammonium chloride (TEBAC) as a phase transfer catalyst. Then, this product was esterified with 3,4-diacetoxylbenzoyl chloride 7 to generate 4-(3,4-diacetoxybenzoyloxy-methyl)phenyl-2,3,4,6-tetra-O-acetyl-b-D-glucopyranoside 8 in 95 % yield. Finally, selectively global deacetylation of 8 was performed in a mixture of dibutyltin oxide and methanol under reflux to afford 1 in 94.8 % yield