Instituto de Química Médica (CSIC), Juan de la Cierva 3, E-28006 Madrid, Spain.
J Org Chem. 2010 Mar 19;75(6):1974-81. doi: 10.1021/jo902677s.
Despite the well-established importance of intermolecular cation-pi interactions in molecular recognition, intramolecular cation-pi interactions have been less studied. Here we describe how the simultaneous presence of an aromatic ring at the 5'-position of an inosine derivative and a positively charged imidazolium ring in the purine base drive the conformation of the nucleoside toward a very major conformer in solution that is stabilized by an intramolecular cation-pi interaction. Therefore, the cation-pi interaction between imidazolium ions and aromatic rings can also be proposed in the design of small molecules where this type of interaction is desirable. The imidazolium ion can be obtained by a simple acidification of the pH of the media. So a simple change in pH can shift the conformational equilibrium from a random to a restricted conformation stabilized by an intramolecular cation-pi interaction. Thus the here described nucleosides can be considered as a new class of pH-dependent conformationally switchable molecules.
尽管分子间阳离子-π 相互作用在分子识别中具有重要地位,但分子内阳离子-π 相互作用的研究较少。在这里,我们描述了在肌苷衍生物的 5'-位上存在芳环和嘌呤碱基中的正电荷咪唑鎓环如何使核苷的构象向溶液中的非常主要构象驱动,该构象通过分子内阳离子-π 相互作用稳定。因此,阳离子-π 相互作用也可以在小分子的设计中提出,在这种相互作用是理想的情况下。咪唑鎓离子可以通过简单地酸化介质的 pH 值获得。因此,pH 值的简单变化可以使构象平衡从随机构象转变为受分子内阳离子-π 相互作用稳定的受限构象。因此,这里描述的核苷可以被认为是一类新的 pH 依赖性构象开关分子。