Total syntheses of platensimycin and related natural products and total syntheses and structural revision of alpha- and beta-diversonolic esters and total synthesis of diversonol

Platensimycin is the representative member of a new class of naturally occurring antibiotics with promising antibacterial properties against drug resistant bacteria. The total syntheses of (+/-)-platensimycin and (--)-platensimycin are described. For the asymmetric synthesis of platensimycin, a rhodium-catalyzed enantioselective cycloisomerization of terminal alkynes has been developed. The synthetic strategies and methods developed have been successfully applied to the total syntheses of the natural congeners of platensimycin, platensimycins B1 and B3, platensic acid, methyl platensinoate, platensimide A, homoplatensimide A, and homoplatensimide A methyl ester.;A general and convergent approach toward the total syntheses of diversonol and the proposed structures of alpha- and beta-diversonolic esters has been described. An unexpected acid induced cyclization process has been discovered, based on which the structures of alpha- and beta-diversonolic have been revised and confirmed by total synthesis. The chemistry developed provides the access to the more complex members of this class of xanthone natural products.