Stereoselective Synthesis of α-3-Deoxy-D-manno-oct-2-ulosonic Acid (α-Kdo) Glycosides Using 5,7-O-Di-tert-butylsilylene-Protected Kdo Ethyl Thioglycoside Donors.

An efficient methodology for the synthesis of α-Kdo glycosidic bonds has been developed with 5,7-O-di-tert-butylsilylene (DTBS) protected Kdo ethyl thioglycosides as glycosyl donors. The approach permits a wide scope of acceptors to be used, thus affording biologically significant Kdo glycosides in good to excellent chemical yields with complete α-selectivity. The synthetic utility of an orthogonally protected Kdo donor has been demonstrated by concise preparation of two α-Kdo-containing oligosaccharides.