Antineoplastic agents 463. Synthesis of combretastatin A-3 diphosphate prodrugs.

A new and more efficient synthesis of combretastatin A-3 (2a) was completed (8.4% overall yield) starting from methyl gallate and isovanillin with aldehyde 5 and phosphonium salt 8 as key intermediates. Conversion of combretastatin A-3 (2a) to a series of diphosphate prodrugs (10a-l) was readily achieved. Both the diphosphate sodium (10a) and potassium salts (10c) displayed aqueous solubility in excess of 220 mg/ml at room temperature and good cancer cell line inhibitory activity.