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A novel approach for enantioseparation as applied to ( RS )‐etodolac from pharmaceutical formulations: LC MS and density functional theory support for confirmation of diastereomers so separated
Author(s) -
Singh Manisha,
Bhushan Ravi
Publication year - 2015
Publication title -
biomedical chromatography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 65
eISSN - 1099-0801
pISSN - 0269-3879
DOI - 10.1002/bmc.3427
Subject(s) - diastereomer , etodolac , chemistry , derivatization , chromatography , racemization , organic chemistry , high performance liquid chromatography , biochemistry
In the present studies formation of diastereomers of ( RS )‐etodolac was confirmed using LC‐MS when [M + H] + or [M] + were recorded for the diastereomers. The lowest energy optimized structures of two diastereomers were drawn, which confirmed the three‐dimensional geometry of the diastereomers. This supports the optimized analytical separation conditions. In addition, separation of diastereomers was successful using a C 18 column and a binary mixture of methanol and triethyl ammonium phosphate buffer of pH 4.5 (80:20, v/v) as mobile phase at a flow rate of 1 mL min −1 and UV detection at 223 nm. The separation method was validated as per International Conference on Harmonization guidelines. ( RS )‐Etodolac was isolated from commercial tablets and purified and characterized to be used as racemic standard. Three pairs of diastereomers were synthesized using enantiomerically pure amines, namely, ( R )‐(+)‐ α ‐methyl benzyl amine, ( S) ‐(−)‐ α ,4‐dimethylbenzylamine and ( R )‐(−)‐1‐cyclohexylethylamine. Derivatization reactions were carried out under conditions of stirring at room temperature (30 °C for 2 h) as well as under microwave irradiation (MWI), and the two types of diastereomers were compared. Reaction conditions for derivatization were optimized with respect to mole ratio of chiral derivatizing agent and ( RS )‐etodolac and MWI time. No racemization was observed throughout the study. Copyright © 2015 John Wiley & Sons, Ltd.