Chiral receptors for phosphate ions
Chiral receptors for phosphate ions
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DOI：
10.1039/b504931h
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发表时间：
2005-01-01
影响因子：
3.2
通讯作者：
Monzani, E
中科院分区：
文献类型：
--
作者：
Amendola, V;Boiocchi, M;Monzani, E
通过UV-Vis和H-1NMR滴定实验，研究了中性受体1的对映体R、R和S、S与阴离子的结合倾向。这两种对映体都与羧酸盐和磷酸盐形成稳定的氢键络合物。特别是，受体1与两个H_2PO_4~-离子的结合遵循两个逐步平衡，其中logK(2)高于logK(1)。这种不寻常的协同效应归因于当两个H_2PO_4-阴离子与受体的两个尿素亚基结合时，在两个H_2PO_4-阴离子之间形成了强的H-键相互作用，如1：2络盐[Bu4N](2)[R，R-1...(H_2PO_4)(2)]的晶体和分子结构所证明的那样。S、S对映体与生物相关的D-2，3-二磷酸甘油酸阴离子形成氢键络合物，其结合常数是R，R络合物的两倍。P-31核磁共振研究表明，这种效应归因于两种非对映异构体络合物在溶液中的不同结构特征。
The binding tendencies of the enantiomeric forms, R,R and S,S, of the neutral receptor 1 towards anions were investigated through UV-vis and H-1 NMR titration experiments in DMSO. Both enantiomers form stable H-bond complexes with carboxylates and phosphates. In particular, receptor 1 strongly binds two H2PO4- ions according two stepwise equilibria, in which logK(2) is higher than logK(1). Such an unusual cooperativity effect is to be ascribed to the formation of strong H-bond interactions between the two H2PO4- anions, when bound to the two urea subunits of the receptor, as demonstrated by the crystal and molecular structures of the 1 : 2 complex salt: [Bu4N](2)[R,R-1...(H2PO4)(2)]. The S,S enantiomer forms an H-bond complex with the biologically relevant D-2,3-diphosphoglycerate anion, whose association constant is twice that of the R,R complex. Such an effect is ascribed to the different structural features of the two diastereomeric complexes in solution, as shown by P-31 NMR studies.