Stereoselective glycosylation of d-galactals by diethyl phosphorochloridite- and AlCl3-assisted Ferrier rearrangement

α-2,3-Unsaturated galactosides were synthesized in good to excellent yields by the initial activation of d-galactals with diethyl phosphorochloridite and the subsequent glycosyl addition via Ferrier rearrangement with various O-nucleophiles in the presence of AlCl3. The two-step reactions were carried out in one-pot and finished within 60 min in 81-95% yield to give the glycoside products with excellent α-stereoselectivity.