A streamlined and efficient approach to the key epoxide intermediate for the asymmetric synthesis of triazole antifungal agents is presented. This synthesis highlights a P(NMe2)3-mediated nonylidic olefination of α-keto ester, ensuring the exclusive formation of the requisite (Z)-alkene, followed by a highly enantioselective Jacobsen epoxidation to establish the two vicinal stereocenters in a single step. The versatility of this strategy is exemplified through the efficient synthesis of efinaconazole and ravuconazole.