Total synthesis of cystothiazoles A and B.

[structure: see text] Convergent enantioselective syntheses of the antifungal agents cystothiazoles A and B are described. The routes feature an asymmetric crotylation using a propargylic dicobalt hexacarbonyl complex, which provided enhanced diastereoselectivity over the uncomplexed propargylic acetal. The bisthiazole fragment was united with the side chain through a Stille cross-coupling of a terminal (E)-vinylstannane with a 4-trifloyl-substituted thiazole.