Bovine serum albumin-mediated enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate
Bovine serum albumin-mediated enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate
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DOI：
10.1021/ja034641g
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发表时间：
2003-06-25
影响因子：
15
通讯作者：
Inoue, Y
中科院分区：
文献类型：
--
作者：
Wada, T;Nishijima, M;Inoue, Y
在牛血清白蛋白 (BSA) 存在下，2-蒽甲酸 (AC) 在水性缓冲溶液 (pH 7) 中于 25 °C 下进行对映分化光环二聚化，得到四种 [4 + 4] 环二聚体，即抗安顺头尾 (HT) (1and2) 和抗安顺头对头 (HH) 二聚体(3和4)，其中只有2和3是手性的。我们发现（1）BSA 拥有四组不同亲和力、化学计量和光反应手性环境的 AC 结合位点，可结合 1、3、2 和 3 个 AC 分子，结合常数分别为 5.3 × 107、1.3 × 105、1.4 × 104 和 3.0 × 103M-1，（2）通过添加 BSA，光二聚化从 HT 转变为 HH（HH/HT 比率从 0.28 到 4.3 变化），(3) BSA 介导的 AC 光二聚化分别提供高达 29% 和 41% ee 的光学活性产物 2 和 3。需要强调的是，利用与 BSA 络合时的光谱位移来选择性激发结合底物，并不是使用生物分子进行有效光致手性作用的先决条件。
Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxyalate (AC) was performed at 25 °C in aqueous buffer solution (pH 7) in the presence of bovine-serum albumin (BSA) to afford four [4 + 4] cyclodimers, i.e.,anti- andsyn-head-to-tail(HT) (1and2) andanti- andsyn-head-to-head(HH) dimers (3and4), of which only2and3are chiral. We found that (1) BSA possesses four sets of binding sites for AC of different affinities, stoichiometries, and chiral environment for photoreaction, which bind 1, 3, 2, and 3 AC molecules with binding constants of 5.3 × 107, 1.3 × 105, 1.4 × 104, and 3.0 × 103M-1, respectively, (2) the regioselectivity of photodimerization is switched from HT to HH by adding BSA (the HH/HT ratio varies from 0.28 to 4.3), (3) BSA-mediated photodimerization of AC affords optically active products2and3of up to 29% and 41% ee, respectively. It is emphasized that the selective excitation of bound substrate, utilizing the spectral shift upon complexation with BSA, is not a prerequisite for efficient photochirogenesis using biomolecules.