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Free keywords:
glycosides; glycosylations; glycosyl iodides; glycosyl phosphates; LiClO4; solvent mixtures;
Abstract:
Glycosyl phosphates, imidates, trifluoroacetates, chlorides, and bromides are converted into the respective glycosyl iodides by treatment with LiI or NaI in 1 M solutions of LiClO4 in CH2Cl2. Under these neutral conditions the reactive glycosyl iodides are activated, and react with different glycosyl acceptors to give O-glycosides in moderate yields, with the alpha-anomers predominating. The glycosylation reactions most probably proceed by the initial formation of beta-configured glycosyl iodides from the alpha-configured precursors, and subsequent attack of the glycosyl acceptor on the equatorial iodide from the axial direction.
