A Short Olefin Metathesis-Based Route to Enantiomerically Pure Arylated Dihydropyrans and α,β-Unsaturated δ-Valero Lactones

The synthesis of arylated dihydropyrans and unsaturated lactones starting from enantiomerically pure alpha-hydroxy ketones (prepared by an enzyme-catalyzed benzoin condensation) is described. The key steps are a highly diastereoselective addition of vinyl metal compounds under chelate control and a ruthenium-catalyzed ring-closing olefin metathesis reaction. Elucidation of the relative configuration of the final products was achieved by NOE experiments.