Facile Synthesis of Sulfated Sialoglycopolypeptides with a γ-Polyglutamic Acid Backbone as Hemagglutinin Inhibitors against Influenza Virus

抄録

The artificial sulfated sialoglycopolypeptides (5 and 6) carrying the Neu5Acα2,3Galβ1,4(6-sulfo)GlcNAc and Neu5Acα2,6Galβ1,4(6-sulfo)GlcNAc residues in the side chain were designed as hemagglutinin inhibitors against influenza viruses. 5-Trifluoroacetamidopentyl β-6-O-sulfo-N-acetylglucosaminide (5-TFAP-β-6SGN, 1) was first produced by β-N-acetylhexosaminidase-mediated transglycosylation using β-D-6-O-sulfo-GlcNAc-O-pNP (6SGN-β-pNP) as the donor and 5-trifluoroacetamido-1-pentanol as the acceptor. Galactosylation with glycosyltransferese was carried out to afford the key disaccharide, 6-O-sulfated N-acetyllactosaminide derivative 2. After detrifluoroacetylation of 2, 6-O-sulfated N-acetyllactosaminide 3 with the 5-aminopentyl group at the reducing end was obtained in three steps in 62% yield. 6-O-Sulfated disaccharide 3 was then coupled with the carboxyl groups of γ-polyglutamic acid (γ-PGA) by a conventional BOP/HOBt chemistry, giving glycopolypeptide 4. Trans-sialylation of glycopolypeptide 4 with α2,3-sialyltransferase or α2,6-sialyltransferase gave the corresponding sulfated sialoglycopolypeptides 5 and 6, respectively. The binding affinity of sulfated sialoglycopolypeptides (5 and 6) to influenza virus hemagglutinin was examined using a hemagglutination inhibition assay. The sulfated α2,6-sialoglycopolypeptide (6) selectively inhibited hemagglutination mediated by human virus A/Aichi/2/68 (H3N2) and had a relative binding affinity for hemagglutinin of ca. 4.9×10²-fold higher than that of the naturally occurring fetuin control. The sulfated α2,3-sialoglycopolypeptide (5) selectively inhibited hemagglutination mediated by avian virus A/Duck/HongKong/313/4/78 (H5N3) and displayed an approximately 1.2×10³-fold higher affinity over fetuin. In addition, the binding affinity of 5 was slightly higher than that of the non-sulfated α2,3 sialoglycopolypeptide (7).