Precision Molecular Architecture of Sugar Balls

糖取代的α-氨基酸N-羧基氰尿酸（glycoNCAs），即，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 NCA（2b）成功地将单糖肽单元引入到树状大分子的每个末端伯氨基上。明确定义的基于树枝状聚合物的人工糖缀合物，O-（β-D-吡喃葡萄糖基）-L-丝氨酸-全取代聚（酰胺基胺）（PAMAM）树枝状聚合物（3a）和0-将PAMAM树状大分子分别与2a和2b进行聚合反应，合成了（2-乙酰氨基-2-去氧-β-D-吡喃葡萄糖基）-L-丝氨酸全取代PAMAM树状大分子（3b），合成了含糖两亲性表面嵌段聚酰胺-胺（PAMAM）树状大分子。苄氧基羰基（z）保护的乙二胺用作部分保护的引发剂核。通过重复迈克尔加成和酰胺形成反应进行第一发散步骤，得到半代甲基酯封端的半球形嵌段。通过过量的正己基胺与半生成的树枝状嵌段反应，得到疏水半球状嵌段。在除去核心-Z基团后，以与第一过程类似的方式进行第二发散PAMAM构建。通过使用glycoNCA 2b成功地实现了糖残基的引入。将糖部分脱乙酰化后，得到含糖的表面封闭树枝状大分子，用小麦胚芽凝集素（WGA）凝集素进行血凝抑制试验，研究了糖球和半糖球的分子识别能力。定性地证明了树状大分子表面糖残基的有序排列对分子的有效识别能力。

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.