Cohen S M, Raymond K N
Department of Chemistry, University of California, Berkeley, California 94720, USA.
Inorg Chem. 2000;39(16):3624-31. doi: 10.1021/ic990608c.
While iron release from enterobactin-mediated iron transport occurs primarily via an esterase that destroys the siderophore, other catechol siderophores that are not susceptible to hydrolysis act as bacterial growth factors. Elucidating the structures of protonated ferric enterobactin may reveal the pathway by which synthetic analogues fulfill bacterial iron requirements. In order to more completely model this potential delivery pathway for ferric iron, as well as to understand the pH dependent structural dynamics of ferric enterobactin, two ligands, (2-hydroxybenzoyl-2-aminoethyl)-bis(2,3-dihydroxybenzoyl-2-aminoethyl)amine (TRENCAMSAM) and (2-hydroxy-3-methoxybenzoyl-2-aminoethyl)-bis(2,3-dihydroxybenzoyl-2- aminoethyl)amine (TRENCAM(3M)SAM), have been synthesized as models for monoprotonated enterobactin. The coordination chemistry of these ligands with Fe3+ and Al3+ has been investigated. Fe[TRENCAMSAM]2- crystallizes in the triclinic space group P1: Z = 1, a = 11.3307(6) A, b = 12.5479(7) A, c = 15.5153(8) A, alpha = 94.513(1) degree, beta = 105.867(1) degree, gamma = 94.332(1) degree. The structure is a two-metal two-ligand dimer supported by mu-oxo bridges from two catecholate moieties. Al[TRENCAMSAM]2- crystallizes in the triclinic space group P1: Z = 2, a = 9.1404(2) A, b = 13.3570(1) A, c = 15.5950(1) A, alpha = 95.711(1) degree, beta = 104.760(1) degree, gamma = 92.603(1) degree. The complex is a monomer with a five-coordinate, square-pyramidal aluminum cation. Al[TRENCAM(3M)SAM]2- crystallizes in the monoclinic space group C2/m: Z = 8, a = 34.244(2) A, b = 11.6206(6) A, c = 21.9890(12) A, beta = 101.478(1) degree. The complex is also a monomer, but with a highly distorted five-coordinate, square-pyramidal aluminum cation coordination sphere. At high pH these complexes do not display a salicylate mode of binding; however, at low pH Al[TRENCAMSAM]2- converts to protonated Al[H3TRENCAMSAM]+, which is a six-coordinate, tris-salicylate complex. Al[H3TRENCAMSAM]+ crystallizes in the triclinic space group P1: Z = 2, a = 11.5475(4) A, b = 12.1681(4) A, c = 12.5094(4) A, alpha = 109.142(1) degree, beta = 104.327(1) degree, gamma = 103.636(1) degree. This is the first catecholamide enterobactin analogue that has been structurally characterized in both a catecholate and salicylate mode of coordination.
虽然肠杆菌素介导的铁转运过程中铁的释放主要通过一种破坏铁载体的酯酶来实现，但其他不易水解的儿茶酚铁载体可作为细菌生长因子。阐明质子化的高铁肠杆菌素的结构可能会揭示合成类似物满足细菌铁需求的途径。为了更全面地模拟这种潜在的高铁递送途径，并了解高铁肠杆菌素的pH依赖性结构动力学，已合成了两种配体，即(2-羟基苯甲酰基-2-氨基乙基)-双(2,3-二羟基苯甲酰基-2-氨基乙基)胺(TRENCAMSAM)和(2-羟基-3-甲氧基苯甲酰基-2-氨基乙基)-双(2,3-二羟基苯甲酰基-2-氨基乙基)胺(TRENCAM(3M)SAM)，作为单质子化肠杆菌素的模型。研究了这些配体与Fe3+和Al3+的配位化学。Fe[TRENCAMSAM]2-在三斜空间群Pī中结晶：Z = 1，a = 11.3307(6) Å，b = 12.5479(7) Å，c = 15.5153(8) Å，α = 94.513(1)°，β = 105.867(1)°，γ = 94.332(1)°。该结构是一个双金属双配体二聚体，由来自两个儿茶酚部分的μ-氧桥支撑。Al[TRENCAMSAM]2-在三斜空间群Pī中结晶：Z = 2，a = 9.1404(2) Å，b = 13.3570(1) Å，c = 15.5950(1) Å，α = 95.711(1)°，β = 104.760(1)°，γ = 92.603(1)°。该配合物是一个单体，具有五配位的四方锥铝阳离子。Al[TRENCAM(3M)SAM]2-在单斜空间群C2/m中结晶：Z = 8，a = 34.244(2) Å，b = 11.6206(6) Å，c = 21.9890(12) Å，β = 101.478(1)°。该配合物也是一个单体，但具有高度扭曲的五配位四方锥铝阳离子配位球。在高pH值下，这些配合物不显示水杨酸酯结合模式；然而，在低pH值下，Al[TRENCAMSAM]2-转化为质子化的Al[H3TRENCAMSAM]+，它是一个六配位的三水杨酸酯配合物。Al[H3TRENCAMSAM]+在三斜空间群Pī中结晶：Z = 2，a = 11.5475(4) Å，b = 12.1681(4) Å，c = 12.5094(4) Å，α = 109.142(1)°，β = 104.327(1)°，γ = 103.636(1)°。这是第一个在儿茶酚酯和水杨酸酯配位模式下都进行了结构表征的儿茶酚酰胺肠杆菌素类似物。
