Chemical and enzymatic synthesis of buprestin A and B—bitter acylglucosides from Australian jewel beetles (Coleoptera: Buprestidae)

A chemical and enzymatic synthesis was developed for buprestin A and B originally isolated from Australian jewel beetles (Coleoptera: Buprestidae). The common motif of both acylglucosides is a β-d-glucopyranose-1,2-bis(pyrrole-2-carboxylate). Starting from 1,3,4,6-tetra-O-acetyl-α-d-glucose, the first pyrrole-2-carboxylate was introduced by DCC–DMAP mediated esterification. After conversion to a trichloroacetimidate the anomeric pyrrole-2-carboxylate was installed. Selective removal of the acetates was accomplished using immobilized Candida antarctica lipase. The resulting triol was converted to Buprestin A or B via a Mitsunobu reaction.