Makuc Damjan, Lenarcic Martina, Bates Gareth W, Gale Philip A, Plavec Janez
Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
Org Biomol Chem. 2009 Sep 7;7(17):3505-11. doi: 10.1039/b908947k. Epub 2009 Jul 9.
The conformational preorganization and anion-induced conformational changes of indole-based receptors functionalized with an amide group at the 2-position and a variety of amide, urea and thiourea moieties at the 7-position have been studied by the means of NMR spectroscopy. NOE experiments showed that anti-anti orientation across C2-C2alpha and C7-N7alpha bonds is preferred for receptors 1-4 in acetone solution in the absence of anions. Anion-receptor interactions have been evaluated through (1)H and (15)N chemical shift changes. In 2,7-bis-carboxamido functionalized indoles the interaction with chloride and bromide anions primarily occurs at the indole H1 proton. The introduction of urea and thiourea moieties increases the number of hydrogen bond donor sites which manifests itself in a distribution of halide-receptor interactions among the H1, H7alpha and H7gamma protons. Acetate anions also interact strongly with indole and urea NH donor groups, whereas nitrate anions interact solely with H7alpha and H7gamma urea/thiourea protons. NOE enhancements in the presence of anions revealed that anion-receptor complexes favour the syn-syn conformation of the C2 and C7 substituents.
通过核磁共振光谱法研究了在2-位用酰胺基官能化且在7-位带有各种酰胺、脲和硫脲部分的吲哚基受体的构象预组织和阴离子诱导的构象变化。NOE实验表明，在没有阴离子的情况下，受体1-4在丙酮溶液中跨C2-C2α和C7-N7α键的反-反取向是优选的。通过¹H和¹⁵N化学位移变化评估了阴离子-受体相互作用。在2,7-双羧酰胺官能化的吲哚中，与氯离子和溴离子的相互作用主要发生在吲哚H1质子处。脲和硫脲部分的引入增加了氢键供体位点的数量，这表现为卤化物-受体相互作用在H1、H7α和H7γ质子之间的分布。醋酸根阴离子也与吲哚和脲NH供体基团强烈相互作用，而硝酸根阴离子仅与H7α和H7γ脲/硫脲质子相互作用。阴离子存在下的NOE增强表明，阴离子-受体复合物有利于C2和C7取代基的顺-顺构象。
