Syntheses of two trimannose analogs each containing C-mannosyl or 5-thio-C-mannosyl residue: their affinities to concanavalin A

C-Mannosyl residue-containing trimannose ManCα(1,6){Manα(1,3)Man} (2) and 5-thio-C-mannosyl residue-containing trimannose 5SManCα(1,6){Manα(1,3)Man} (3) were synthesized via a glycosyl radical addition to enone derivative of mannose (6). Dissociation constants for the binding of these trisaccharides to concanavalin A (ConA) were determined by a fluorescence anisotropy inhibition assay: Kd = 198 and 31 μM, respectively. The unexpectedly large Kd value for the compound 2 compared with the compound 3 and the natural trimannose 1 demonstrates a characteristic of C-glycoside.