Synthesis and immunochemical studies of linear oligoglucosides structurally related to the cyclic β-(1→2)-D-glucan of Brucella.

Cyclic β-(1→2)-D-glucan (CβG) is a unique carbohydrate derivative produced by pathogenic bacteria of the genus Brucella. Controversial opinions regarding the use of CβG in brucellosis diagnosis have been published. Herein we report the first synthesis of spacered oligo-β-(1→2)-D-glucosides related to the fragments of CβG and containing up to 5 glucose units. Although the desired di- and trisaccharides could be obtained using standard methods, the synthesis of tetra- and pentasaccharides required substantial effort. The obtained oligosaccharides exhibited complex dependencies of their NMR spectral data on the chain length, explained by a tendency to form helical structures. Despite high production of the CβG by Brucella, antibodies to β-(1→2)-D-glucosides detected in human sera are not related to the brucellosis. However, the antibodies to CβG were raised after immunization by BSA-conjugate of penta-β-(1→2)-D-glucoside and allowed detection of CβG, which opens a way towards the development of the new brucellosis diagnostic kit.