An enantioselective method for the synthesis of 1,2-anti diols has been developed. A cyclometallated chiral-at-Ru complex catalyzes the asymmetric ring opening/cross metathesis of di–oxygenated cyclobutenes, resulting in functionally rich synthetic building blocks. Syntheses of the insect pheromone (+)-endo brevicomin and monosaccharide ribose demonstrate the synthetic utility of the 1,2-anti diol fragments generated in the title reaction.