For the purpose of the scrutiny of multi-functions of oligosaccharides at the molecular level, the practical method for the chemical construction is essential. In 1989, we have established the practical method for α-selective sialylation that utilizes nitrile solvent effect to fashion thermodynamically-disfavored equatorial glycoside. Due to the powerful method, we have succeeded in many first syntheses of sialyl oligosaccharide complexes such as sialyl Lewis X, GQ 1 b.
Recently, we have developed highly reactive
N-Troc-protected sialyl donor and 1, 5-lactamized sialyl acceptor.
N-Troc sialyl donor enabled us to perform high-yielding sialylation, and obtained sialoside could be pivotally derived into various homologues containing Neu 5 Gc, NeuNH
2 and 8-
O-sulfo-Neu 5 Ac. Further, the synergic coupling with 1, 5-lactamized acceptor produced α(2-4) -and α(2-8) -linked disialic acid sequences in high yields, thereby resulting in the first synthesis of glycan portions of gangliosides HLG-2 and Hp-s 6.
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