Rekharsky Mikhail V, Yamamura Hatsuo, Kawai Masao, Inoue Yoshihisa
Entropy Control Project, ICORP, JST, 4-6-3 Kamishinden, Toyonaka 560-0085, Japan.
J Org Chem. 2003 Jun 27;68(13):5228-35. doi: 10.1021/jo034314r.
The stability constants (K) and the standard free energy (deltaG degrees ), enthalpy (deltaH degrees ), and entropy changes (deltaS degrees ) for the complexation of gamma-cyclodextrin with 34 enantiomeric and diastereomeric N-acetyl- and N-carbobenzyloxy-d/l-dipeptides with two aromatic moieties were determined in aqueous buffer solution at 298.15 K by titration microcalorimetry. Chiral recognition of the enantiomeric dipeptide pairs by gamma-cyclodextrin was found to be fairly poor, exhibiting only small percentage differences in K, while the diastereomeric dipeptides were discriminated to much greater extent with affinity differences of up to 6-7 times. The complex structures of several selected pairs were elucidated by NMR techniques. Combining the microcalorimetric and NMR data, the complexation and chiral recognition behavior of gamma-cyclodextrin is discussed in particular in terms of the length, bulkiness, and flexibility of the tether connecting the two aromatic moieties in a guest.
在298.15 K的水性缓冲溶液中，通过滴定微量热法测定了γ-环糊精与34种具有两个芳香基团的对映体和非对映体N-乙酰基和N-苄氧羰基-d/l-二肽络合的稳定常数（K）、标准自由能（ΔG°）、焓（ΔH°）和熵变（ΔS°）。发现γ-环糊精对对映体二肽对的手性识别相当差，K值的百分比差异很小，而非对映体二肽的区分程度要大得多，亲和力差异高达6至7倍。通过核磁共振技术阐明了几个选定对的络合物结构。结合微量热法和核磁共振数据，特别是从客体中连接两个芳香基团的链的长度、体积和柔韧性方面讨论了γ-环糊精的络合和手性识别行为。
