Precision Molecular Architecture of Sugar Balls

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Sugar-substituted α-amino acid N-carboxyanhydrides (glycoNCAs), i.e., O-(tetra-O-acetyl-β-D-glucopyranosyl)-L-serine NCA (2a) and O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl)-L-serine NCA (2b), were successfully used for introduction of a monoglycopeptide unit to each terminal primary amino group of a dendrimer. Well-defined dendrimer-based artificial glycoconjugates, O-(β-D-glucopyranosyl)-L-serine-persubstituted poly(amido amine) (PAMAM) dendrimer (3a) and O-(2-acetamido-2-depxy-β-D-glucopyranosyl)-L-serine-persubstituted PAMAM dendrimer (3b), were synthesized by polymer reaction of PAMAM dendrimer with 2a and 2b respectively, followed by deacetylation with hydrazine monohydrate.Sugar-containing amphiphilic surface-block poly (amido amine) (PAMAM) dendrimer was synthesized as follows. Benzyloxycarbonyl (z)-protected ethylenediamine was used as a partial-protected initiator core. The 1st divergent step was carried out by repeating Michael addition and amide formation reaction to afford half-generational methyl ester-ended hemispherical block. A hydrophobic hemispherical block was obtained by the reaction of an excess amount of n-hexylamine with the half-generated dendritic block. After removal of the core-Z group, the 2nd divergent PAMAM construction was conducted in a similar manner to the 1st process. Introduction of sugar residues was successfully achieved by using the glycoNCA 2b. After deacetylation of the sugar moiety, a sugar-containing surface-block dendrimer was isolated.Molecular recognition ability of the sugar balls and the half-sugar ball was investigated by a hemagglutination inhibition test using wheat germ agglutinin (WGA) lectin. Effective molecular recognition ability of the arranged sugar residues on the surface of dendrimers was qualitatively demonstrated.