Regio- and stereospecific synthesis of mono-beta-d-glucuronic acid derivatives of combretastatin A-1

Synthetic routes have been established for the preparation of regio- and stereoisomerically pure samples of the mono-beta-d-glucuronic acid derivatives of combretastatin A-1, referred to as CA1G1 (5a) and CA1G2 (6a). Judicious choice of protecting groups for the catechol ring was required for the regiospecific introduction of the glucuronic acid moiety. The tosyl group proved advantageous in this regard. The two monoglucuronic acid analogues demonstrate low cytotoxicity (compared to CA1, 2) against selected human Cancer cell lines, with CA1G1 being slightly more potent than CA1G2.