Desymmetrizing Asymmetric Epoxidations of Bis(cis-configured) Divinyl­carbinols: Unusual syn-Selectivity Combined with ee-Enhancement through Kinetic Resolution

Bis(cis-1-alkenyl)methanols 2a and b were monoepoxidized by a 1:1:1 mixture of RtertOOH, an optically active tartaric acid derivative, and a Zr(IV) alkoxide. This provided epoxy alcohols syn-1a,b with perfect diastereoselectivity. These compounds are the minor products of analogous Ti(IV)-mediated epoxidations. The ee of epoxy alcohol syn-1a was increased up to 99% when less enantioenriched material was overoxidized under the reaction conditions ((right arrow) up to 66% bisepoxy alcohol syn,syn-5).