O-GLYCOSIDE SYNTHESIS WITH GLYCOSYL IODIDES UNDER NEUTRAL CONDITIONS IN 1 M LICLO4 IN CH2CL2

Glycosyl phosphates, imidates, trifluoroacetates, chlorides, and bromi des are converted into the respective glycosyl iodides by treatment wi th LiI or NaI in 1 M solutions of LiClO4 in CH2Cl2. Under these neutra l conditions the reactive glycosyl iodides are activated, and react wi th different glycosyl acceptors to give O-glycosides in moderate yield s, with the alpha-anomers predominating. The glycosylation reactions m ost probably proceed by the initial formation of beta-configured glyco syl iodides from the alpha-configured precursors, and subsequent attac k of the glycosyl acceptor on the equatorial iodide from the axial dir ection.