Reversed‐phase high‐performance liquid chromatographic enantioresolution of six β‐blockers using dinitrophenyl‐l‐Pro‐N‐hydroxysuccinimide ester, N‐succinimidyl‐(S)‐2‐(6‐methoxynaphth‐2‐yl) propionate and twelve variants of Sanger's reagent as chiral derivatizing reagents

Abstract

Twelve chiral derivatizing reagents (CDRs) were synthesized by substituting one of the fluorine atoms in 1,5-difluoro-2,4-dinitrobenzene (DFDNB) with three optically pure amines [(R)-(-)-1-cyclohexylethylamine, (+)-dehydroabietylamine and (S)-(-)-alpha,4-dimethylbenzylamine], six amino acid amides [L-Ala-NH(2), L-Phe-NH(2), L-Val-NH(2), L-Leu-NH(2), L-Met-NH(2) and D-Phg-NH(2)] and three amino acids [L-Ala, L-Val and L-Leu]. In addition, dinitrophenyl-L-Pro-N-hydroxysuccinimide ester and N-succinimidyl-(S)-2-(6-methoxynaphth-2-yl) propionate were also synthesized and used as CDR. Keeping in view the presence of an amino group, diastereomers of six beta-blockers (atenolol, propranolol, bisoprolol, metoprolol, salbutamol, and carvedilol) were synthesized by reaction with these 14 CDRs. The diastereomers were separated by RP-HPLC. The method was validated for linearity, accuracy, limit of detection and limit of quantification.

(RS)‐Propranolol: enantioseparation by HPLC using newly synthesized (S)‐levofloxacin‐based reagent, absolute configuration of diastereomers and recovery of native enantiomers by detagging

“…Although the CDRs were considered as enantiomerically pure, their enantiomeric purity was further confirmed as per literature reports (Bhushan and Tanwar, 2009;Bhushan and Dixit, 2012). (S)-(À)-Lfx isolated from commercial tablets was purified and characterized and it was used as an enantiomerically pure chiral auxiliary for synthesis of CDRs.…”

“…In addition, new CDRs were found to be more stable (>5 months at 2-5°C) as compared with CDRs based on DFDNB (Bhushan and Tanwar, 2009;Bhushan and Nagar, 2014a) and isothiocyanate (Kleidernigg et al, 1996;Péter et al, 2001;Péter and Fülöp, 2002). In addition, new CDRs were found to be more stable (>5 months at 2-5°C) as compared with CDRs based on DFDNB (Bhushan and Tanwar, 2009;Bhushan and Nagar, 2014a) and isothiocyanate (Kleidernigg et al, 1996;Péter et al, 2001;Péter and Fülöp, 2002).…”

“…The separation factors (α, 1.23-1.61) for the diastereomers prepared with the newly synthesized CDRs were found to be better than the diastereomers prepared with CDRs based on (S)-naproxen (Batra and Bhushan, 2014;Bhushan and Nagar, 2014b), and CDRs having L-amino acids as chiral auxiliary in cyanuric chloride (Bhushan and Dixit, 2012), DFDNB (Bhushan and Tanwar, 2009; N-Benzotriazolyl-(S)-9-fluoro-3-methyl-10-(4-methylpiperazin-1-yl)-7-oxo-3,7- Bhushan and Nagar, 2014a) and isothiocyanate (Kleidernigg et al, 1996;Péter and Fülöp, 2002). The newly synthesized CDRs were found to provide better Rs (2.91-4.71) in comparison with the resolution reported in the literature (Bhushan and Tanwar, 2009;Bhushan and Dixit, 2012;Péter and Fülöp, 2002;Péter et al, 2001;Kleidernigg et al,1996;Büschges et al, 1996); for example, Rs was 2.34 and 3.23 using (R)-MBIC and (S)-NEIC as CDRs, respectively (Bhushan and Dubey, 2011).…”

“…In addition, there have been a few reports from this laboratory on successful enantioseparation of certain β-blockers using ligand exchange chromatography (Kumar and Bhushan, 2014) and CDRs based on difluorodinitrobenzene (Bhushan and Tanwar, 2009;Bhushan and Nagar, 2014a), cyanuric chloride (Bhushan and Dixit, 2012) and (S)-naproxen (Singh and Bhushan, 2015). For 1,5-Difluoro-2,4-dinitrobenzene (DFDNB)-based derivatives a photochemical decomposition occurs if the solutions are not protected from light and many of the other reagents lead to formation of unstable derivatives, or lack of quantitative yield or poor detection.…”

Molecular Modeling Study of Chiral Separation and Recognition Mechanism of β-Adrenergic Antagonists by Capillary Electrophoresis

“…Analytical methods so far used for chiral separations of these β-adrenergic antagonists include thin layer chromatography [4,5], HPLC [6–8], capillary electrochromatography [9,10], and capillary electrophoresis (CE) [11–14]. CE especially has attracted the greater interest for chiral separations.…”