Synthesis of immunostimulatory alpha-C-galactosylceramide glycolipids via Sonogashira coupling, asymmetric epoxidation, and trichloroacetimidate-mediated epoxide opening

Stereocontrolled syntheses of alpha-C-GalCer (2) and its alpha-C-acetylenic analogue 6 were accomplished in high efficiency by a convergent construction strategy from 1-hexadecene and d-galactose. The key transformations include Sonogashira coupling, Sharpless asymmetric epoxidation, and Et(2)AlCl-catalyzed cyclization of an epoxytrichloroacetimidate to generate protected dihydrooxazine 21.