Improved synthesis of gastrodin, a bioactive component of a traditional chinese medicine

Abstract

Highly practical, four-step synthesis of gastrodin was developed using penta- O-acetyl-β-D-glucopyranose and p-cresol as glycosyl donor and glycosyl acceptor, respectively, in 58.1% overall yield. As the initial step, the penta-O-acetyl-β-D-glucopyranose was treated with p-cresol in the presence of BF3 •Et2O as catalyst to generate 4-methylphenyl 2,3,4,6-tetra-O-acetyl-β-D- -glucopyranoside in 76.3% yield. Further, this product was subjected to radical bromination with N-bromosuccinimide (NBS) to provide 4-(bromomethyl)phenyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside in 91% yield. Subsequently, reaction of 4-(bromomethyl)phenyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside with a solution of acetone and saturated aqueous sodium bicarbonate led to 4-(hydroxymethyl)phenyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside in 93% yield. Finally, global deprotection of 4-(hydroxymethyl)phenyl 2,3,4,6-tetra-O- -acetyl-β- D-glucopyranoside under Zemplen conditions furnished gastrodin in 90% yield. Compared to the previously reported methods, this protocol has the advantages of operational simplicity, chromatography-free separation, high overall yield, inexpensive and common reagents as well as less waste pollutants, rendering it an alternative suitable for industrial production.