The complete relative and absolute stereochemistries have been elucidated for the ansamycin antibiotics (+)-trienomycins A, B, and C and their potent antifungal congeners, the (+)-mycotrienins I and II. A new species, (+)-trienomycin F, has also been isolated and characterized. In addition, an end-game synthetic strategy for the trienomycins and mycotrienins has been developed.