Synthesis of Azido-Functionalized Carbohydrates for the Design of Glycoconjugates

As carbohydrates play a major role in numerous biological processes through their interactions with lectins and also appear as one of the most crucial post-translational modifications of proteins, chemists have developed several approaches for the design of glycoconjugates based on a series of conjugation methodologies. The recent development of copper(I)-catalyzed azide-alkyne cycloaddition (CuACC) paved the way to a novel conjugation strategy in which azido-functionalized carbohydrate derivatives can be readily connected to alkyne-functionalized (bio)molecules. This so-called “click chemistry” methodology has now found numerous applications both in chemistry and biology. The azido moiety can be introduced either directly at the anomeric carbon of the carbohydrate derivative, or attached to a spacer arm. We describe here the syntheses of 2,3,4,6-tetra-
O
-acetyl-β-
d-glucopyranosyl azide as well as 1-azido-3,6-dioxaoct-8-yl 2,3,4,6-tetra-
O
-acetyl-β-
d-galactopyranoside and 1-azido-3,6-dioxaoct-8-yl 2,3,6,2′,3′,4′,6′-hepta-
O
-acetyl-β-
d-lactoside. These molecules can then be used in the construction of glycoconjugates to find applications in chemical biology.