CFTA method, a new procedures for determination of absolute configurations of chiral sec-alchols by 1H and 19F NMR.
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Accession number;99A0711851
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| Title;CFTA method, a new procedures for determination of absolute configurations of chiral sec-alchols by 1H and 19F NMR. |
| Author;
TAKAHASHI TAMIKO
(Toyama Med. and Pharm. Univ., Fac. of Pharm. Sci.)
FUKUSHIMA AKI
(Toyama Med. and Pharm. Univ., Fac. of Pharm. Sci.)
TANAKA YUKI
(Toyama Med. and Pharm. Univ., Fac. of Pharm. Sci.)
TAKEUCHI YOSHIO
(Toyama Med. and Pharm. Univ., Fac. of Pharm. Sci.)
KABUTO KUNINOBU
(Tohoku Univ., Grad. Sch.)
KABUTO CHIZUKO
(Tohoku Univ., Grad. Sch.)
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Journal Title;Fusso Kagaku Toronkai Koen Yoshishu
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Journal Code:F0135B
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ISSN:
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VOL.22nd;NO.;PAGE.82-83(1998)
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| Figure&Table&Reference; |
| Pub. Country;Japan |
| Language;Japanese |
| Abstract;We have developed the CFTA method using .ALPHA.-cyano-.ALPHA.-fluoro-p-tolylacetic acid (CFTA), which procedure is much more useful than the well-known MTPA method in determining absolute configurations. In the 1H NMR, we observed a systematic trend of .DELTA..DELTA.H (.DELTA.SR - .DELTA.RR) values obtained for the CFTA esters with chiral secondary alcohols. Therefore, the concept of the modified Mosher's method has been successfully applied to the CFTA procedure. Furthermore, in addition to the greater magnitude of the .DELTA..DELTA.F (.DELTA.SR - .DELTA.RR) values, the consistency in the signs of these values suggests that the CFTA method can be more reliable in assigning absolute configurations of secondary alcohols based on 19F NMR. The ground state conformational geometry and energy of (S)- and (R)-menthyl esters of (R)-CFPA were evaluated by ab initio calculations (GAUSSIAN 94, RHF/6-31G*). Possible two stable rotamers were suggested for the esters: one is synperiplanar (sp) with the C.ALPHA.-F and C=O bonds and the other is antiperiplanar (ap) with these bonds. The sp rotamer can explain the signs of .DELTA..DELTA.H. The sence of nonequivalence in the 19F NMR could be rationalized by the bias of the presence of the sp and ap rotamers. (author abst.) |
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