FICA,a new chiral derivatizing agent for determining the absolute configuration of secondary alcohols by 19F and 1H NMR spectroscopies |
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| Authors: | Tamiko Takahashi Hiroaki Kameda Tomoyo Kamei Jyunichi Koyanagi Fabio Pichierri Kenji Omata Miyuki Ishizaki Hiroshi Nakamura |
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| Affiliation: | 1. Faculty of Pharmaceutical Sciences, Josai International University, 1 Gumyo, Togane, Chiba 283-8555, Japan;2. Division of Chemistry, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan;3. Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-07, Sendai 980-8579, Japan;4. Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan |
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| Abstract: | Optically active 1-fluoroindan-1-carboxylic acid (FICA) was designed and prepared as its methyl ester for determining the absolute configuration of chiral molecules by both 1H and 19F NMR spectroscopies. Enantiomerically pure isomers of FICA methyl esters (FICA Me esters) were obtained by chromatographic separation using HPLC with a Daicel Chiralcel OJ-H column. The absolute configuration of the (+)-FICA Me ester was deduced to be (S) by X-ray crystallographic analysis of the (+)-FICA amide of (R)-α-phenethylamine. Both enantiomers were derived to the diastereomeric esters of chiral secondary alcohols by an ester exchange reaction. In the 1H NMR spectra, the signs of ΔδH (δR ? δS) were consistent on each side of the FICA molecular plane. Therefore, the concept of the modified Mosher’s method could be successfully applied to the FICA-based procedure. Moreover, the consistency in the signs of ΔδF (δR ? δS) values suggests that the FICA method would be reliable in assigning the absolute configurations of secondary alcohols based on 19F NMR spectroscopy. |
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