Enantiodifferentiating Photoisomerization of Cyclooctene Included and Sensitized by Aroyl-β-cyclodextrins: A Critical Enantioselectivity Control by Substituents

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• 作者：Runhua Lu ; Cheng Yang ; Yujuan Cao ; Linhui Tong ; Wei Jiao ; Takehiko Wada ; Zhizhong Wang ; Tadashi Mori ; Yoshihisa Inoue
• 刊名：Journal of Organic Chemistry
• 出版年：2008
• 出版时间：October 3, 2008
• 年：2008
• 卷：73
• 期：19
• 页码：7695-7701
• 全文大小：252K
• 年卷期：v.73,no.19(October 3, 2008)
• ISSN：1520-6904

文摘

A series of 6-O-benzoyl-β-cyclodextrins (CDs) with methyl, methoxy, methoxycarbonyl, and bromo substituent(s) at the ortho-, meta-, and/or para-position(s) were synthesized as chiral sensitizing hosts for the use in supramolecular enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z) to its chiral (E)-isomer (1E). The complex stability constants (K_S) of the modified β-CDs with 1Z in aqueous methanol solutions were highly sensitive to the substituent(s) introduced to the benzoate moiety, and the log K_S values decreased linearly with slightly different slopes with increasing methanol content. The enantiomeric excess (ee) of 1E obtained upon photosensitization with these hosts was a critical function of the size and position of the substituent, varying from almost zero to 46% ee. This indicates that even an apparently small structural difference between methyl and methoxy can critically affect the enantiodifferentiating photoisomerization of a guest included in the chiral cavity, probably through manipulation of both the orientation of ground-state 1Z and the subsequent rotational relaxation of excited 1Z inside the chiral cavity.