Catalytic Asymmetric Synthesis of Both syn- and anti-3,5-Dihydroxy Esters:  Application to 1,3-Polyol/α-Pyrone Natural Product Synthesis

We describe a catalytic asymmetric synthesis of both syn- and anti-3,5-dihydroxy esters. The method relies upon catalytic asymmetric epoxidation of α,β-unsaturated imidazolides and amides, using lanthanide-BINOL complexes, and diastereoselective reduction of ketones. The method was applied to the enantioselective syntheses of 1,3-polyol/α-pyrone natural products 9a, 9b, and strictifolione (10). The absolute stereochemistry of 9a and 9b was also determined.