Development of Fluorescently Labeled SSEA-3, SSEA-4, and Globo-H Glycosphingolipids for Elucidating Molecular Interactions in the Cell Membrane.

Glycosphingolipids (GSLs), such as the globo-series GSLs stage-specific embryonic antigen 3 (SSEA-3), SSEA-4, and Globo-H, are specifically expressed on pluripotent stem cells and cancer cells, and are known to be associated with various biological processes such as cell recognition, cell adhesion, and signal transduction. However, the behavior and biological roles of these GSLs are still unclear. In our previous study, we observed the interactions between the lipid raft and GSLs in real-time using single-molecule imaging, where we successfully synthesized various fluorescent analogs of GSLs (e.

p- tert-Butyl Groups Improve the Utility of Aromatic Protecting Groups in Carbohydrate Synthesis.

Aromatic protective groups are widely used in carbohydrate synthesis owing to their numerous merits. However, they unpredictably make certain compounds insoluble in organic solvents owing to their π-stacking abilities. It was found that introducing a tert-butyl group onto the aryl moiety improves the solubility of highly insoluble carbohydrate derivatives, such as those of N-acetylglucosamine.

Constrained sialic acid donors enable selective synthesis of α-glycosides.

Sialic acid is a sugar residue present in many biologically significant glycans of mammals, commonly as a terminal α-glycoside. The chemical structure of sialic acid, which features an anomeric center with carboxyl and methylene substituents, poses a challenge for synthesis of the α-glycoside, thus impeding biological and therapeutic studies on sialic acid-containing glycans. We present a robust method for the selective α-glycosidation of sialic acid using macrobicyclized sialic acid donors as synthetic equivalents of structurally constrained oxocarbenium ions to impart stereoselectivity.