Expedient synthesis of aminooxylated-carbohydrates for chemoselective access of glycoconjugates

Herein, we describe an efficient preparation of various biologically important 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 involves the coupling of fluoro-activated protected sugar and N-hydroxyphthalimide in the presence of BF3·Et2O. Final deprotection and cleavage of the phthalimide moiety with methylhydrazine afforded new Glc-β-ONH2 3, GalNAc-β-ONH2 9, Glc-α-ONH2 14, Gal-α-ONH2 17 and Man-α-ONH2 20 derivatives with good yields. Compared to the literature results, the preparation of Gal-β-ONH2 6, GalNAc-α-ONH2 11 and Lac-β-ONH2 23 proved to be more efficient.