Salimabromide, a unique and scarce marine tetracyclic polyketide, was synthesized in both racemic and optically active forms. A novel carboxylic acid-directed method for tandem oxidative difunctionalization of olefins was developed, whereby the formation of bridged butyrolactone and enone moieties occurs concurrently. Density functional theory (DFT) calculations indicate that this reaction follows a [3+2] process rather than the [2+2] process. In the meantime, the distinctive benzo-fused [4.3.1] carbon skeleton and highly hin-dered vicinal quaternary stereocentres were simultaneously constructed through a challenging intramolecular Giese-Baran radical cyclization. Furthermore, deuterium kinetic isotopic effects were utilized to enhance the efficacy of this pivotal step. This represents a new illustration of the application of kinetic isotope effects in natural product synthesis. Then, short asymmetric syntheses of (+)-salimabromide (13 or 15 steps) was accomplished by combing this method with rhodium-catalyzed enantioselective hydrogena-tion of a cycloheptenone derivative (97% ee) or conjugate addition of an aryl boronic acid with 2-cyclohepten-1-one (> 99% ee).

The first catalytic asymmetric total synthesis of (+)-propolisbenzofuran B, enabled by a highly enantioselective rhodium-catalyzed hy-drogenation of a tetrasubstituted olefin, was described. Other noteworthy aspects include the construction of the central hydrodiben-zo[b,d]furan core through a sequence of Zn(II)-mediated regioselective benzofuran formation and Dieckmann condensation, as well as C-H oxidations, involving a visible light-induced Fe(III)-catalyzed benzylic C(sp3)-H oxidation. Additionally, the absolute configuration was confirmed by X-ray analysis of a carbonate intermediate.