The use of MPA amide for the assignment of absolute configuration of a sterically hindered cyclic secondary amine by 'mix and shake' NMR method.
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Gao, Jinhai, Haas, Hansjoerg, Wang, Kate Yaping, Chen, Zhuoliang, Breitenstein, Werner and Rajan, Srinivasan (2008) The use of MPA amide for the assignment of absolute configuration of a sterically hindered cyclic secondary amine by 'mix and shake' NMR method. Magnetic Resonance in Chemistry : MRC, 46 (1). pp. 17-22. ISSN 1097-458X
Abstract
We present here a new method using methoxyphenylacetic acid (MPA) as the chiral derivatizing agent (CDA) for the assignment of absolute configuration of cyclic secondary amines. The MPA amides were prepared using the purification-free 'mix and shake' method. A detailed conformational analysis for the two diastereomeric amides was conducted by 2D NMR experiments and molecular mechanics calculations. We have established that, in the most stable conformation of each syn rotamer of MPA amides, the H-alpha in the MPA moiety is oriented toward the bulky substituent group at the asymmetric carbon in the chiral amine, presumably to avoid steric and/or electrostatic interactions. The observed NMR data were correlated with the conformational model to allow unambiguous assignment of absolute configuration of secondary amines. The results demonstrate that the MPA can be used as a useful CDA in the case of sterically crowded cyclic secondary amines from which the MTPA amides are usually difficult to make. Copyright (c) 2007 John Wiley & Sons, Ltd.
| Item Type: | Article |
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| Additional Information: | archiving not allowed on institutional repository |
| Keywords: | 1H NMR; absolute configuration; cyclic secondary amine; MPA amide |
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| Date Deposited: | 14 Dec 2009 13:51 |
| Last Modified: | 14 Dec 2009 13:51 |
| URI: | https://oak.novartis.com/id/eprint/919 |