[Au]/[Ag]-Catalyzed Glycosidation of Ethynylcyclohexyl Glycosyl Carbonates Enables Direct Stereoselective Synthesis of 2-Azido-2-deoxy-β-mannopyranosides.

We describe the [Au]/[Ag]-catalyzed activation of ethynylcyclohexyl 2-azido-4,6--benzylidene mannosyl carbonates for β-mannosamine linkage preparation in high yield and selectivity in a temperature- and concentration-dependent manner. VT-NMR studies reveal an anomeric triflate intermediate generated in the absence of an acceptor alcohol that is stable up to -10 °C. The generality of the protocol was illustrated by successful application to a series of acceptors and by synthesis of a fully protected type 19F capsular trisaccharide.

Entropy-enthalpy compensation in the methyl 5-thio-α-d-galactopyranoside-Jacalin interaction.

Methyl 5-thio-α-d-galactopyranoside was synthesized and found to have a more favorable enthalpy of binding to Jacalin than methyl α-d-galactopyranoside, which is attributed to the greater magnitude of sulfur-π over oxygen-π interactions. This increase in enthalpy, however, was offset by a less favorable entropy of binding, arising from the need to constrain the more flexible thiosugar, thereby highlighting the complexities inherent in the design of effective sugar mimetics.

Synthesis and evaluation of 1,5-dithialaminaribiose and -triose tetravalent constructs.

We report the synthesis of novel tetravalent glucoclusters containing 1,5-dithia mimetics of laminaribiose and triose. The new constructs were evaluated for their ability to inhibit anti-CR3 fluorescent staining of human neutrophils, for which they showed moderate affinity. Evaluation of the synthesized glycoclusters for their ability to inhibit anti-Dectin-1 fluorescent staining of mouse macrophages revealed little to no affinity for Dectin-1.