Practical and Green Synthesisof Combretastatin A-4 and Its Prodrug CA4P Using Renewable Biomass-BasedStarting Materials

A practical and green protocol for the synthesis of vasculardisrupting agent combretastatin A-4 (CA4) and its water soluble prodrugCA4P is described. Starting from the biomass-based compound anethole,which is abundantly and sustainably available from Chinese staranise ( ILLICIUM VERUM Hook. f.), thekey intermediate 3-hydroxy-4-methoxyphenylacetic acid can be obtainedwithin five steps. Perkin condensation between this acid and anothernaturally derived compound 3,4,5-trimethoxybenzaldehyde, followedby decarboxylation gives combretastatin A-4 in good overall yield.The phosphate produrg CA4P can be prepared under simple and mild conditionsin a sequential one-pot two-step reaction.