Host–guest complexation of antioxidative caffeic and ferulic acid amides with a functionalized cyclophane
作者:Claudia Virués、Zaira Domínguez、Magali Salas、Rosa Elena Navarro、Enrique F. Velázquez、Samuel Cruz、Javier Hernández、Motomichi Inoue
DOI:10.1007/s10847-012-0134-8
日期:2012.12
Host−guest complexation has been studied by 1H NMR on the benzyl and phenethyl amides of ferulic and caffeic acids as the guests in chloroform and acetonitrile; the counter host is a cyclophane which integrates four phenylene rings, amino and amide groups in the macrocyclic framework and bears four pendant methyl acetate ester arms. CAPE, one of the best known natural antioxidants, also has been studied for comparison. Among the guests studied, ferulic acid benzyl amide shows NMR shifts due to the formation of a host−guest complex in chloroform. The complexation occurs in two steps with the formation constants K 1 = [HG]/[H][G] = 6 M−1 and β 2 = [HG2]/[H][G]2 = 87 M−2. Two guest molecules are bound on the surface of the macrocyclic framework of a host molecule by two hydrogen bonds, NH(host amide)···O=C(guest amide) and C=O(host ester)···HO(guest phenol). The latter hydrogen bond may protect the bioactive site, i.e., phenol OH, of guest molecules captured in the complex against undesirable oxidation. This feature is observed only for ferulic acid benzyl amide in chloroform; the cyclophane ester interacts with this amide, distinctively from the other hydroxycinnamic acid derivatives.
我们通过 1H NMR 研究了阿魏酸和咖啡酸的苄基和苯乙基酰胺在氯仿和乙腈中的主-客复合物;反主是一种环烷,它在大环框架中集成了四个亚苯基环、氨基和酰胺基团,并带有四个下垂的醋酸甲酯臂。CAPE 是最著名的天然抗氧化剂之一,我们也对其进行了比较研究。在所研究的客体中,阿魏酸苄基酰胺在氯仿中形成的主-客体复合物显示出核磁共振偏移。络合分两步进行,形成常数 K 1 = [HG]/[H][G] = 6 M-1 和 β 2 = [HG2]/[H][G]2 = 87 M-2 。两个客体分子通过两个氢键(NH(主酰胺)--O=C(客体酰胺)和 C=O(主酯)--HO(客体苯酚))结合在主分子的大环框架表面。后一个氢键可保护络合物中捕获的客体分子的生物活性位点(即苯酚羟基)免受不良氧化。只有阿魏酸苄基酰胺在氯仿中才能观察到这一特征;环烷酯与这种酰胺的相互作用与其他羟基肉桂酸衍生物不同。