Group B streptococcus (GBS) is a Gram positive bacterium, which causes neonatal invasive diseases as well as severe infections in the elderly and immune compromised patients.  On the basis of the capsular polysaccharide (CPS) structure, ten serotypes of GBS have been identified (Ia, Ib, II through IX).  Among these, type II GBS is one of the predominant GBS serotypes and responsible for 13% of early onset diseases.  Although the structure of GBS II was elucidated in 1983,  only one synthesis has been reported in literature.  The repeating unit of GBS type II is composed of α-Neu5Ac (2-3)-β-D-Gal-(1-4)-β-D-GlcNAc-(1-3)-[-β-D-Gal-(1-6)]-β-D Gal-(1-4)- β-D-Gal-(1-3)-β-D-Glc (Figure1).
In the present communication, we show our results of an novel approach to the synthesis of this heptasaccharide, based on the subcomponents highlighted in Figure 1. Suitably protected lactosamine C and lactose derivatives B are pivotal building blocks in our synthesis.  The synthetic GBS II fragments will be used for glycan array and structural studies and immunochemical characterization with specific monoclonal antibodies.
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- This project has received funding from the H2020-MSCA-ITN-2015 “Glycovax’’ under grant agreement No 675671.