Total Syntheses of Roseochelins A and B Using an Oxidative Decarboxylation Strategy

Roseochelins A and B are produced by Phaeobacter inhibens and proposed to arise from algal sinapic acid through combined enzymatic and nonenzymatic steps. We report concise, biomimetic total syntheses mirroring a revised biosynthetic pathway differing from earlier proposals in key oxidative and decarboxylative intermediates. Roseochelin A arises via spontaneous 4 + 2 dimerization of sinapic acid to thomasidioic acid, followed by metal-catalyzed oxidative decarboxylation. Roseochelin B is accessed by regioselective catechol formation, ortho-quinone-mediated thiomethylation, and late-stage metal- or photocatalyzed oxidative decarboxylation.