Rhodium-Catalyzed Enantioselective Synthesis of Oxazinones via an Asymmetric Ring Opening-Lactonization Cascade of Oxabicyclic Alkenes

The rhodium-catalyzed asymmetric ring opening reaction of oxabicyclic alkenes is shown to be an efficient method for synthesizing chiral heterocycles. We demonstrate that the pairwise combination of chiral catalyst with chiral amino-acid-derived pronucleophiles results in a stereodivergent synthesis of diastereomeric hydroxyesters. A favorable conformational preference induces the subsequent lactonization of one diastereomer leading to the highly enantioselective synthesis of oxazinones.