First Application of Biopolymers for Chiral Reaction Field of Asymmetric Photoreactions

在这项研究中，作者提出了一种新的不对称光化学的策略或超分子光手性的新概念，其中生物分子的手性信息被转移或倍增的光产物通过溶液相的手性生物分子主体与前手性客体基板和随后的单，双分子光化学反应，所产生的主客体复合物。所有的超分子photochirogenic的方法，采用改性的环糊精，（寡）核苷酸，DNA，RNA和蛋白质作为手性生物分子的主机，是成功的，在良好的光学产率创建光学活性的photoproducts。因此，利用手性生物分子的超分子相互作用进行光化学不对称合成的最初想法已被证明是有用的，作为一种新的光手性方法，并有可能扩展到其他超分子系统。获得的主要结果 ...更多信息 本论文的主要工作如下：研究了不同温度下，环糊精包合物敏化的环辛烯在水溶液中的对映异构化反应。实际上，在185 nm下直接照射容纳在天然β-环糊精中的（Z）-环辛烯时获得的<1%的原始差ee显著提高至高达24%ee。首次显示出作为有效的手性光敏剂和/或或在水溶液中的手性光反应场来实现（Z）-环辛烯的对映异构化。用DNA光敏化后产生的手性（E）-异构体的最佳ee为15%，有利于（S）-（+）-（E）-环辛烯。以d（T）_ d（A）_为光敏剂，可得到ee高达26%的（R）-（E）-环辛烯<15><15>，而其它双链体的光敏化则得到几乎外消旋的（E）-环辛烯。因此，碱基的组成和排列顺序是决定（Z）-环辛烯光异构化反应对映选择性的重要因素，而连续的寡聚胸苷序列是实现（Z）-环辛烯高对映选择性光异构化反应的必要条件。少

In this study, the author has proposed a new strategy of asymmetric photochemistry or a new concept of supramolecular photochirogenesis, in which the chiral information of biomolecules is transferred to or multiplied in photoproducts through the solution-phase supramolecular interaction of chiral biomolecular hosts with prochiral guest substrates and the subsequent Uni, and bimolecular photochemical reactions of the resulting ,host-guest complexes. All of the examined supramolecular photochirogenic approaches, employing modified cyclodextrins, (oligo) nucleotides, DNA, RNA, and protein as chiral biomolecular hosts, were successful in creating optically active photoproducts in good optical yields. Thus, the original idea of using the supramolecular interactions of chiral biomolecules in photochemical asymmetric synthesis has been demonstrated to be useful as a novel photochirogenic methodology, and is potentially extended to the other supramolecular systems. The major findings obtained … More in this thesis may be summarized as follows.The enantiodifferentiating Z-to-E photoisomerization of cyclooctene included and sensitized by chromophoreappended cyclodextrins was investigated in aqueous solution at varying temperatures. Indeed, the original poor ee of <1 % obtained upon direct irradiation at 185 nm of (Z)-cyclooctene accommodated in native b-cyclodextrin was dramatically enhanced up to 24 % ee.The double stranded DNA, as well as nucleosides and (oligo)nucleotides, have been shown for the first time to function as effective chiral photosensitizers and/or chiral photoreaction field in aqueous solution to effect the enantiodifferentiating photoisomerization of (Z)-cyclooctene. The best ee of the chiral (E)-isomer produced upon, photosensitization with DNA was 15 % in favor of (S)-(+)-(E)-cyclooctene. (R)-(E)-cyclooctene was obtained in an ee as high as 26 % by using d(T)_<15> d(A) _<15> as a photosensitizer, whereas the photosensitizations by the other duplexes gave nearly racemic (E)-isomer. It is concluded therefore that the composition and the sequence of nucleobases are important factors in determinins the enantioselectivity, and the consecutive oligothymidine sequence is essential for realizing the highly enantioselectm photoisomerization of (Z)-cyclooctene. Less