Montmorillonite K10 was found to catalyze, under microwave irradiation, rapid O-glycosidation of 3,4,6-tri-O-acetyl-D-galactal to afford exclusively the alkyl and aryl 2,3-dideoxy-D-threo-hex-2-enopyranosides with very high α-selectivity and without the formation of the 2-deoxy-D-lyxo-hexopyranosides. Under these conditions, 3,4,6-tri-O-acetyl-D-glucal as usual also underwent the Ferrier rearrangement. © 2002 Elsevier Science Ltd. All rights reserved.