International Symposium of Glycosciences
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Highly Alpha-Selective Sialyl Phosphate Donors for Efficient Preparation of
Natural Sialosides
Che-Hsiung Hsua,b, Kuo-Ching Chua, Yih-Shyan Lina, Chung-Yi Wua, and Chi-Huey Wonga
a
b
The Genomics Research Center, Academia Sinica, Taipei 115, Taiwan
Chemical Biology and Molecular Biophysics, Taiwan International Graduate Program, Academia
Sinica, Taipei 115, Taiwan
e-mail: che0430@gate.sinica.edu.tw
Abstract. N-Acetyl neuraminic acid (Neu5Ac) is most frequently found at the terminal end of
glycoconjugates on the cell surface. This terminally exposed position allows Neu5Ac-containing
conjugates to be exploited as receptors for viruses and bacteria, in addition to governing a wide variety
of biological processes, such as tumor metastasis, cell differentiation, and cell–cell interaction.
Chemical sialylation has long been a major challenge in carbohydrate chemistry. Here, we present
new sialylation reagents which combine N-acetyl-5-N,4-O-carbonyl or 5-N,4-O-carbonyl protections
and anomeric dibutyl phosphate as a leaving group for the facile preparation of natural sialosides. The
glycosylation results of several different C5-modified sialyl phosphate donors showed that
N-acetyl-5-N,4-O-carbonyl protection presented the highest -selectivity. In addition, compared to
N-acetyl-5-N,4-O-carbonyl protected thiosialosides, conversion of sulfide leaving group at the
anomeric position to dibutyl phosphate showed elevated -selectivity.
Several strategies were developed by using N-acetyl-5-N,4-O-carbonyl and 5-N,4-O-carbonyl
protected sialyl phosphate donors to synthesize natural sialosides, including (a) regioselective
preparation of sialylated thioglycoside building blocks with five different natural linkages; (b) to
calculate the relative reactivity values (RRvs) of sialylated disaccharides and its application toward
reativity-based programmable one-pot glycosylation; (c) high-yielding synthesis of sialosides via
orthogonal one-pot glycosylation; (d) -only blockwise synthesis of polysialic acid tetramer.
[1] C.-H. Hsu, K.-C. Chu, Y.-S. Lin, J.-L. Han, Y.-S. Peng, C.-T. Ren, C.-Y. Wu, and C.-H. Wong,
Chem. Eur. J., 16, 1754 (2010)