Indirect enantioseparation of selenomethionine by reversed‐phase high‐performance liquid chromatography using a newly synthesized chiral derivatizing reagent based on (S)‐naproxen moiety

Abstract

(S)-Naproxen was reacted with N-hydroxyphthalimide in the presence of coupling reagent dicyclohexylcarbodiimide, and a new chiral derivatizing reagent, phthalimidyl-(S)-naproxen ester, was synthesized. It was characterized and was used for synthesis of diastereomers of selenomethionine via microwave irradiation or vortexing. The reaction conditions were optimized. Diastereomeric pairs synthesized by two approaches were successfully separated by reversed-phase high-performance liquid chromatography using binary mixtures of aqueous triethylammonium phosphate and acetonitrile. Detection was carried out at 231 nm. The limit of detection was found to be 0.11 and 0.10 pmol/mL for diastereomers of d- and l-SeMet, respectively. The method was validated for accuracy, precision and limit of detection. The new chiral derivatizing reagent was capable of enantioseparation of dl-SeMet in the form of diastereomers having higher stability, enhanced resolution and lower limits of detection in comparison to the diastereomers prepared with other chiral derivatizing reagents reported in the literature. Optimized structures of the two diastereomers were drawn using the Gaussian 09 Rev. A.02 program and hybrid density functional B3LYP with 6-31G basis set to explain the separation mechanism.

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

“…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).…”

Liquid chromatographic enantioseparation of (RS)‐mexiletine and (RS)‐fluoxetine using chiral derivatizing reagents synthesized with (S)‐naproxen moiety

“…As reported (Bhushan and Nagar, ), the mechanism of separation can be considered on the basis of the structures of the two diastereomers having cis ‐ or trans ‐type arrangement because of the restricted rotation around the C–N bond which gives the amide bond a partial double character. Optimized structures of the two diastereomers were drawn using the Gaussian 09 Rev.…”

“…Nap‐Btz (CDR2), being an amide, is more stable than CDR1 (Bhushan and Tanwar, ) an ester, owing to higher thermodynamic stability of amides over esters. Synthesizing CDR3 (Nap‐Phth) is easier than other two since H‐Phth is neither explosive in nature like benzotriazole nor hygroscopic like H‐Suc (Bhushan and Nagar, ).…”

“…( S )‐Naproxen (Nap, 6‐methoxy‐ α ‐methyl‐2‐naphthaleneacetic acid), having a carboxylic acid group, high molar absorptivity ( ε >100,000) and commercial availability as the pure ( S )‐enantiomer, is suitable for the preparation of CDRs, which can be used for the indirect chiral chromatographic separation of amino group‐containing analytes. CDRs prepared by the reaction of ( S )‐Nap with (a) N ‐hydroxysuccinimide (H‐Suc) providing N ‐succinimidyl‐( S )‐2‐(6‐methoxynaphth‐2‐yl) propionate (SINP, CDR1; Bhushan and Tanwar, ), (b) 1 H ‐benzotriazole (H‐Btz) providing ( S )‐1‐[1 H ‐benzo(d)(1,2,3)triazol‐1‐yl]‐2‐(6‐methoxynaphthalen‐2‐yl)propan‐1‐one (Nap‐Btz, CDR2; Bhushan and Dubey, ; Bhushan and Nagar, ), (c) N ‐hydroxyphthalimide (H‐Phth) providing N ‐phthalimidyl‐( S )‐2‐(6‐methoxynaphth‐2‐yl) propionate (Nap‐Phth, CDR3; Bhushan and Nagar, ) and (d) hydrazine hydrate (Bhushan and Lal, ) have been used for the indirect enantioresolution of penicillamine, cysteine, homocysteine, selenomethionine and 18 proteinogenic amino acids, and certain carbonyl compounds. These CDRs were shown to require only mild derivatization conditions and shorter reaction time, and were sensitive to amino groups.…”

Enantioresolution of Amino Acids: A Decade’s Perspective, Prospects and Challenges

“…In conclusion, they highlighted that the large, highly conjugated naphthyl ring of CDR attached to the chiral center offers high UV absorbance and gives detection at very low concentration (LOD 0.1-1.2 pmol range), and the hydrophobic property of the naphthyl ring facilitates enantioresolution. Recently, a new CDR phthalimidyl-(S)-naproxen ester was prepared and used for synthesis of diastereomers of SeMet via microwave irradiation or vortexing, by Bhushan and Nagar [181]. The diastereomeric pairs were successfully separated by RP-HPLC using binary mixtures of aqueous triethylammonium phosphate and acetonitrile with low limit of detection 0.11 and 0.10 pmol/mL for d-and l-SeMet diastereomers, respectively.…”