Expedient synthesis of aminooxylated-carbohydrates for chemoselective access of glycoconjugates

Herein, we describe an efficient preparation of various biologically import ant carbohydrate motifs bearing an aminooxy group at the anomeric position. These nucleophilic sugar analogues represent useful intermediates for the chemoselective preparation of glycoconjugates. The key glycosylation step i nvolves the coupling of fluoro-activated protected sugar and N-hydroxyphtha limide in the presence of BF3. Et2O. Final deprotection and cleavage of the phthalimide moiety with methylhydrazine afforded new Glc-beta -ONH2 3, Gal NAc-beta -ONH2 9, Glc-alpha -ONH2 14, Gal-alpha -ONH2 17 and Man-alpha -ONH 2 20 derivatives with good yields. Compared to the literature results, the preparation of Gal-beta -ONH2 6, GalNAc-alpha -ONH2 11 and Lac-beta -ONH2 2 3 proved to be more efficient. (C) 2001 Elsevier Science Ltd. All rights re served.