Expeditious Synthesis of the Marine Natural Products Prepolycitrin A and Polycitrins A and B through Heck Arylations

New, efficient protocols for the syntheses of the marine natural products prepolycitrin A as well as polycitrins A and B were developed by employing the Heck-Matsuda arylation of maleic anhydride or dimethyl fumarate with aryldiazonium tetrafluoroborates. Both symmetrical and unsymmetrical 3,4-diarylmaleic anhydrides were easily and effectively prepared. Efficient bromination reactions that employed tribromoisocyanuric acid provided access to the polycitrin family of compounds. Under microwave irradiation in the presence of tyramine, the corresponding maleimides were obtained in high yields from the brominated 3,4-diarylmaleic anhydrides. This methodology provided for the concise synthesis of prepolycitrin A and the total syntheses of the marine alkaloids polycitrins A and B in overall yields of 37 and 47% from maleic anhydride and dimethyl fumarate, respectively.