Lascano Santiago, Zhang Kang-Da, Wehlauch Robin, Gademann Karl, Sakai Naomi, Matile Stefan
National Centre of Competence in Research (NCCR) , Molecular Systems Engineering (MSE) , Switzerland . http://www.nccr-mse.ch.
Department of Organic Chemistry , University of Geneva , Geneva , Switzerland . Email:
Chem Sci. 2016 Jul 1;7(7):4720-4724. doi: 10.1039/c6sc01133k. Epub 2016 Apr 20.
Orthogonal dynamic covalent bonds are of interest for the construction of functional systems. The orthogonality of disulfide and hydrazone exchange under basic and acidic conditions, respectively, is well established. However, the integration of boronate esters as the third bond has failed so far because they exchanged too easily, especially under hydrazone exchange conditions. In this report, a collection of bioinspired catechols derived from adhesive natural products from cyanobacteria is screened with phenylboronic acids with proximal alcohols (benzoboroxoles), amines and fluorines to identify the least labile boronate esters. Moreover, Kool's 2-aminophenol catalysts are introduced to selectively accelerate hydrazone exchange without disturbing sufficiently inert boronate esters. Based on these results, we identified three different conditions to selectively exchange disulfides, hydrazones and boronate esters, that is to demonstrate the existence of three orthogonal dynamic covalent bonds. Moreover, their compatibility with functional systems is confirmed by successful hydrazone exchange in multicomponent surface architectures in the presence of intact boronate esters and disulfides.
正交动态共价键对于功能体系的构建具有重要意义。二硫键和腙键分别在碱性和酸性条件下的正交性已得到充分证实。然而，硼酸酯作为第三种键的整合至今尚未成功，因为它们交换过于容易，尤其是在腙键交换条件下。在本报告中，我们用带有近端醇（苯并硼氧六环）、胺和氟的苯基硼酸对一系列源自蓝藻粘附性天然产物的仿生儿茶酚进行筛选，以确定最稳定的硼酸酯。此外，引入库尔的2-氨基酚催化剂以选择性加速腙键交换，同时不干扰足够惰性的硼酸酯。基于这些结果，我们确定了三种不同条件来选择性交换二硫键、腙键和硼酸酯，即证明了三种正交动态共价键的存在。此外，在完整的硼酸酯和二硫键存在下，通过多组分表面结构中的成功腙键交换，证实了它们与功能体系的兼容性。
