2004年6月22日
Sequential arrangement of γ-vaierolactone enantiomers enclathrated in cholic acid channels as studied by 13C solid-state NMR: Elucidation of the optical resolution mechanism
Journal of the American Chemical Society
- ,
- ,
- ,
- 巻
- 126
- 号
- 28
- 開始ページ
- 8769
- 終了ページ
- 8776
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1021/ja049463l
The mechanism of the optical resolution of γ-valerolactone (VAL) enantiomers by enclathration in cholic acid (CA) channels was investigated. 13C cross-polarization magic-angle spinning spectra of CA/ VAL inclusion compounds show four methyl 13C peaks of VAL with different intensities depending on the enantiomeric ratios. The four peaks were assigned to the inner and end (S)-(-)-enantiomers (S) in the S domain and the inner and end (R)-(+)-enantiomers (R). The relative intensities of the four methyl 13C peaks cannot be explained by the random process model for inclusion but are successfully reproduced by assuming the first-order Markov process, in which the inclusion probabilities of S and R depend on which enantiomer has precedingly entered the CA channel. The probability p S/S that two S enantiomers successively enter a channel is thus found to be 83%, and pR/R is 50%. The large probability of pS/S indicates that once an S enantiomer enters a channel, it become easy for other S enantiomers to successively enter the channel, and thus the large enantiomeric excess of S is obtained. The inclusion probabilities of S and R were confirmed by 1D 13C-13C polarization-transfer experiments among the four methyl carbons of VAL in the CA channel. Further, we found that the 13C line widths and peak positions of the CA tail group change depending on the enantiomeric ratio. We concluded that once S is included, it changes the conformation of the CA tail group so that other S enantiomers become easy to successively enter the channel.
- ID情報
-
- DOI : 10.1021/ja049463l
- ISSN : 0002-7863
- PubMed ID : 15250730
- SCOPUS ID : 3242691279