A stereoselective totalsynthesis of topsentolide B2, a selective cytotoxic oxylipin against SK-OV-3 and SK-MEL-2 cancer cell lines has been achieved based on asymmetric dihydroxylation, Roush allylation, and ring closing metathesis (RCM) reactions. The synthesis is completed in 11 steps and 2.1% overall yield.