Synthesis and Self-Assembly of Glycal-Based Bolaforms

Glycal-based bolaforms serve as synthetically flexible components of molecular self-assembly. The compounds are prepared in good yield by a Ferrier reaction between triacetylglucal or -galactal or diacetylxylal and a long chain α,ω-diol, followed by deacetylation under Zemplén conditions. The reactions are stereoselective and preferentially afford the α-diastereomer. The bolaforms undergo self-assembly in water or water/dioxane solution to give a variety of nanostructures. In solution, bolaforms with C8 or C10 chains between glucal headgroups form nanoscale vesicles. In contrast, bolaforms with C12 chains exhibit lower solubility and a dynamic self-assembly, forming several different nanoscale structures. However, the solid-state structures of C12 bolaform isomers adopt shapes very similar to those of bolaforms possessing more extensive hydrogen-bonding networks, indicating that multiple hydrogen bonds in solution are important to formation of stable, discrete nanostructures but that only a few key intermolecular interactions between bolaform headgroups are necessary to determine the structure in the solid state. The diversity and differentiation of the functional groups present in glycal-based bolaforms suggest that they could be useful probes of the various noncovalent forces controlling the structure of new nanomaterials.

基于糖醛的球状体作为分子自组装的合成柔性元件。这些化合物通过三乙酰葡萄糖或其半乳糖或二乙酰木糖与长链α,ω-二醇之间的费里耶反应制备，产率良好，随后在Zemplen条件下进行脱乙酰化。这些反应具有立体选择性，优先提供α-非对映异构体。球状体在水或水/二氧六烷溶液中发生自组装，形成各种纳米结构。在溶液中，具有C8或C10链的球状体在葡萄糖头基之间形成纳米级囊泡。相比之下，具有C12链的球状体表现出较低的溶解度，并具有动态自组装特性，形成多种不同的纳米级结构。然而，C12球状体异构体的固态结构呈现出与具有更广泛氢键网络的球状体非常相似的形状，这表明溶液中存在的多个氢键对于形成稳定、离散的纳米结构至关重要，但只有球状体头基之间的一小部分关键分子间相互作用对于确定固态结构是必要的。存在于糖醛基球状体中的官能团的多样性和差异化表明，它们可以作为探究控制新型纳米材料结构的各种非共价力的有用探针。