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LC-SPE (cryo)NMR approach to the impurity profiling of 7-ethyltryptophol

7-Ethyltryptophol, 2(7-ethyl-1H-indol-3- yl)ethanol, is a key starting material in the synthesis of Etodolac, a non-steroidal anti- inflammatory drug. Depending on the synthetic pathway for 7-ethyltryptophol, commercially available material comprises many different impurities which can cause formation of coproducts in the synthesis of Etodolac thus complicating the purification of the final product.[1] Therefore, to develop an optimal purification procedure of Etodolac, it is important to know the structures of impurities in 7-ethyltryptophol. Classical methods for separation and isolation of impurities, such as preparative or semi- preparative liquid chromatography, are time and solvent consuming. Nowadays, hyphenated NMR techniques are becoming faster, more efficient and more sensitive tool for determination of impurities and degradation products in pharmaceuticals and natural products. [2, 3] In this study LC-SPE (cryo)NMR methodology was used to identify impurities in 7-ethyltryptophol. Chromatographic separation was achieved on Waters XBridge Phenyl and C18 columns (150 mm x 4.6 mm ; 3.5 μm) using a combination of gradient and isocratic elution. Compounds were trapped on HySphere Resin GP cartridges in a SPE multitrapping mode. 1H, COSY, 1H-13C HSQC, 1H-13C HMBC NMR spectra and MS spectra were recorded to determine the structures of impurities. In this way 17 compounds were identified. These results show a good potential of LC-SPE (cryo)NMR technique in an identification and structural characterization of low level impurities and degradation products in pharmaceuticals. References: [1] M. C. Sekharayya, G. V. Narayana, S. Nigam, G. Madhusudhan, Indian J. Chem. 51B (2012) 1763-1766. [2] S. Singh, T. Handa, M. Narayanam, A. Sahu, M. Junwal, R. P. Shah, J. Pharm. Biomed. Anal. 69 (2012) 148-173. [3] J. W. Jaroszewski, Planta Med. 71 (2005) 795-802

LC-SPE-NMR ; 7-ethyltryptophol ; impurities

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