Preparation of azide biosynthetic surrogates of myo-Inositol

As a prelude to biomolecular incorporation studies, practical routes to a series of four regioisomeric azido-deoxy derivatives of inositol that mimic the natural myo-stereochemistry are described. Starting from commercially available myo-inositol, the regioselective and stereoselective introduction of azide functionality was achieved at the C-2, C-3, C-4 and C-5 positions via azide displacement of the corresponding O-sulfonates of suitably protected scyllo-, chiro-, epi- and neo-inositols, respectively. Notably, a final one-pot acetolysis method conveniently allowed for rapid access to pentaacetate azido-deoxy inositols. Investigations on the metabolic incorporation of these myo-inositol azide surrogates in both acetate and free alcohol forms are in progress

Synthetic Studies of Azido-Inositols and Inositol-based Glycans

Ph.DDOCTOR OF PHILOSOPH

[Au]/[Ag]-catalysed expedient synthesis of branched heneicosafuranosyl arabinogalactan motif of Mycobacterium tuberculosis cell wall

Emergence of multidrug-resistant and extreme-drug-resistant strains of Mycobacterium tuberculosis (MTb) can cause serious socioeconomic burdens. Arabinogalactan present on the cellular envelope of MTb is unique and is required for its survival; access to arabinogalactan is essential for understanding the biosynthetic machinery that assembles it. Isolation from Nature is a herculean task and, as a result, chemical synthesis is the most sought after technique. Here we report a convergent synthesis of branched heneicosafuranosyl arabinogalactan (HAG) of MTb. Key furanosylations are performed using [Au]/[Ag] catalysts. The synthesis of HAG is achieved by the repetitive use of three reactions namely 1,2-trans furanoside synthesis by propargyl 1,2-orthoester donors, unmasking of silyl ether, and conversion of n-pentenyl furanosides into 1,2-orthoesters. Synthesis of HAG is achieved in 47 steps (with an overall yield of 0.09%) of which 21 are installation of furanosidic linkages in a stereoselective manner

Microbe-focused glycan array screening platform

International audienceInteractions between glycans and glycan binding proteins are essential for numerous processes in all kingdoms of life. Glycan microarrays are an excellent tool to examine protein-glycan interactions. Here, we present a microbe-focused glycan microarray platform based on oligosaccharides obtained by chemical synthesis. Glycans were generated by combining different carbohydrate synthesis approaches including automated glycan assembly, solution-phase synthesis, and chemoenzymatic methods. The current library of more than 300 glycans is as diverse as the mammalian glycan array from the Consortium for Functional Glycomics and, due to its microbial focus, highly complementary. This glycan platform is essential for the characterization of various classes of glycan binding proteins. Applications of this glycan array platform are highlighted by the characterization of innate immune receptors and bacterial virulence factors as well as the analysis of human humoral immunity to pathogenic glycans