Fine Tuning of the Cation Affinity of Artificial Receptors Based on Cyclic Peptides by Intramolecular Conformational Control
作者:Stefan Kubik、Richard Goddard
DOI:10.1002/1099-0690(200101)2001:2<311::aid-ejoc311>3.0.co;2-m
日期:2001.1
introduction of substituents at the 4-positions of the aromatic rings results in complete loss of the anion affinity. The cation complex stabilities depend on the substituents and cover a wide range from Ka = 140 M−1 for R = CH3 to Ka = 10800 M−1 for R = COOCH3 (Ka = 1260 M−1 for R = H) with n-butyltrimethylammonium picrate. The conformations of the peptides in solution have been determined by one- and two-dimensional
已经制备了一系列由交替的 4-取代 3-氨基苯甲酸单元 (R = CH3、Cl、CH2OCH3、OCH3、COOCH3) 和天然氨基酸脯氨酸残基组成的环状六肽,并研究了它们的离子亲和力。而未取代的母体化合物 (R = H) 能够通过与芳香族亚基的阳离子-π 相互作用结合阳离子,以及通过与肽 NH 基团的氢键结合阴离子,在芳香族亚基的 4 位引入取代基环导致阴离子亲和力完全丧失。阳离子络合物的稳定性取决于取代基,涵盖范围很广,从 R = CH3 的 Ka = 140 M-1 到 R = COOCH3 的 Ka = 10800 M-1(R = H 的 Ka = 1260 M-1),n-丁基三甲基苦味酸铵。溶液中肽的构象已通过一维和二维核磁共振技术和 FT-IR 光谱确定。发现所有取代基都阻止肽采用阴离子结合所需的构象。对于一种受体 (R = OCH3),结果已通过晶体结构测定得到证实。AM1