Carbohydrates are diverse bio-macromolecules with highly complex structures that are involved in numerous biological processes. Well-defined carbohydrates obtained by chemical synthesis are essential to the understanding of their functions. However, synthesis of carbohydrates is greatly hampered by its insufficient efficiency. So far, assembly of long carbohydrate chains remains one of the most challenging tasks for synthetic chemists. Here we describe a highly efficient assembly of a 92-mer polysaccharide by the preactivation-based one-pot glycosylation protocol. Several linear and branched oligosaccharide/polysaccharide fragments ranging from 5-mer to 31-mer in length have been rapidly constructed in one-pot manner, which enables the first total synthesis of a biologically important mycobacterial arabinogalactan through a highly convergent [31+31+30] coupling reaction. Our results show that the preactivation-based one-pot glycosylation protocol may provide access to the construction of long and complicated carbohydrate chains.

Cancer is still one of the most serious threats to human worldwide. Aberrant patterns of glycosylation on the surface of cancer cells, which are correlated with various cancer development stages, can differentiate the abnormal tissues from the healthy ones. Therefore, tumor-associated carbohydrate antigens (TACAs) represent the desired targets for cancer immunotherapy. However, these carbohydrate antigens may not able to evoke powerful immune response to combat with cancer for their poor immunogenicity and immunotolerance. Different approaches have been developed to address these problems. In this review, we want to summarize the latest advances in TACAs based anticancer vaccines.

of main observation and conclusionThe N-glycans attached to some chloroviruses comprise a hyperbranched core structure without precedent. We are interested in the chemical synthesis of the hexasaccharide attached to ATCV-1 (Acanthocystis turfacea Chlorella virus 1) for its distinct structure. After exploring four routes, the target hexasaccharide 2 was successfully synthesized for the first time in overall 10% yield over 8 steps from thioglycoside building blocks. This synthetic protocol is characterized by the three-component one-pot glycosylation and the regioselective glycosylation reactions. The disclosed synthetic approach to this new type of N-glycans will facilitate the in-depth understanding of their biological functions. Scheme 1 Structures of N-glycans(a) Typical core motif of N-glycans. (b) Typical N-glycan structures from mammals, plants and yeast. (c) The new type core motif of N-glycan from chloroviruses. (d) New type N-glycan structures from PBCV-1 (Paramecium bursaria chlorella virus 1) and ATCV-1 (Acanthocystis turfacea Chlorella virus 1) Scheme 2 Chemical structures of N-glycans from ATCV-1 Chin.

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