Precision Molecular Architecture of Sugar Balls

用糖基取代的N-羧酸酐(O-(tetra-O-acetyl-β-D-glucopyranosyl)-L-serine-NCA(2a)和O-(2-acetamido-3，4，6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl)-L-serine-α(2b))成功地在树枝状大分子的每个末端伯氨基上引入了单糖肽单元。O-(β-D-glucopyranosyl)-L-serine-persubstituted聚酰胺胺(PAMAM)树枝状大分子分别与2a和2b发生聚合反应，再与一水合肼进行脱乙酰化反应，合成了基于树枝状大分子的人工糖结合物O-(2-acetamido-2-depxy-β-D-glucopyranosyl)-L-serine-persubstituted聚酰胺胺(PAMAM)(3a)和PAMAM树枝状大分子(3b)。以苯氧甲酰基(Z)保护的乙二胺作为部分保护的引发剂核。第一步发散反应重复Michael加成和酰胺生成反应，得到半代甲酯封端的半球形嵌段。过量的正己胺与半生成的树枝状嵌段反应，得到疏水半球形嵌段。在去除CORE-Z基团后，以与第一过程类似的方式进行第二分歧PAMAM构建。利用糖基Nca 2b成功地实现了糖残基的导入。糖段脱乙酰化后，分离得到一种含糖表面封闭型树枝状大分子，用小麦胚芽凝集素(WGA)凝集素进行血凝抑制试验，考察糖球和半糖球的分子识别能力。定性地证明了树枝状大分子表面糖残基的有效分子识别能力。

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.