Synthesis of Cell-Recognizable Sugar-Peptide Conjugates by Living Ring-Opening Polymerization

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Well-defined glycopeptide-containing block copolymers were synthesized by ring-opening polymerization of a sugar-substituted alpha-amino acid N-carboxyanhydride (NCA), i.e., O-(tetra-O-acetyl-beta-D-gluco-pyranosyl)-L-serine NCA (1), initiated with omega-amine-terminated poly (2-methyl-2-oxazoline) and poly (2-phenyl-2-oxazoline) macroinitiators in dichloromethane at 27ﾟC.DPs of peptide segments of the resulting poly (2-methyl-2-oxazoline)-block-poly [O-(tetra-O-acetyl-beta-D-glucopyranosyl)-L-serine](2a) and poly (2-phenyl-2-oxazoline)-block-poly [O-(tetra-O-acetyl-beta-D-glucopyranosyl)-L-serine](2b) were close to monomer/macroinitiator feed molar ratios. Glycopeptide-bearing block copolymers, poly (2-methyl-2-oxazoline)-block-poly [O-(beta-D-glucopyranosyl)-L-serine] and poly (2-phenyl-2-oxazoline)-block-poly [O-(beta-D-glucopyranosyl)-L-serine], were derived from 2a and 2b, respectively, by deacetylation with hydrazine monohydrate.First synthesis of well-defined glycopeptide macromonomers with an alpha-styryl group was performed by living ring-opening polymerization of sugar-substituted NCAs, i.e., 1 and O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl)-L-serine NCA,followed by deacetylation with hydrazine monohydrate in methanol at 0ﾟC.Water-soluble copolymer between the macromonomer and acrylamide was obtained by the radical copolymerization with 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPD) as an initiator in water at 55ﾟC.