Strategies and tactics for the synthesis of oxygenated natural products.

The total synthesis of the ansa antibiotic macbecin I [1] is described exploiting an approach that features the oxidative transformation of furans into hydropyrans that then serve as conformationally biased templates for stereoselective refunctionalization and elaboration. A novel variant of the Mitsunobu reaction was developed that may be applied to the inversion of hindered secondary alcohols. In work directed toward the total synthesis of the antifungal antibiotic ambruticin [3], new and general methods have been invented for the asymmetric synthesis of functionalized cyclopropanes by intramolecular cyclopropanations of omega-unsaturated diazoacetates and the convergent stereoselective synthesis of trisubstituted alkenes.