Synthesis of succinimidyl-(S)-naproxen ester and its application for indirect enantioresolution of penicillamine by reversed-phase high-performance liquid chromatography

Relative quantitation of chiral thiol compounds labeled based on isotope novel mass spectrometry probes: Monitoring of the dynamic changes of chiral thiol compounds in human urine during normal, exercise, and rest recovery states

Monitoring changes in the content of chiral thiol compounds in the human body is crucial for the early diagnosis of oxidative stress-related diseases and the exploration of their pathogenesis. To address this, we synthesized a novel isotope mass spectrometry (MS) probe, denoted as (R)-(5-(3-isothiocyanato (13C) pyrrolidin-1-yl)-5-oxopentyl) triphenylphosphonium (N13CS-OTPP), with triphenylphosphine as its parent structure. In this study, we established a new ultra-high-performance liquid chromatography high-resolution mass spectrometry (UHPLCHRMS) relative quantitative method to monitor chiral thiol compounds in human urine under varying oxidative stress conditions. This method relies on the ratio of 12C/13C isotope-labeled peak areas. To assess the chiral separation efficiency of N13CS-OTPP, we employed three types of thiol compounds (D/L-GSH, D/L-Cys, and D/L-Hcy) and observed separation degrees (Rs) ranging from 1.82 to 1.89. We further validated the accuracy and feasibility of our relative quantitative methods using D/L-Cys-as a model compound. N12C/13CS-OTPP-Cys-exhibited excellent linearity (R2 = 0.9993-0.9994) across different molar ratios (D/L-Cys = 10:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1:10) and achieved a low limit of detection (LOD) of 2.5 fmol. Additionally, we monitored the dynamic changes in urine D/L-Cys-and D/L-Hcy ratios in 12 healthy volunteers (six males and six females) under various oxidative stress states. We generated fitting curves and investigated the trends in chiral thiol compounds in vivo. This study introduces a novel method for the relative quantitative monitoring of chiral thiol compounds in different oxidative stress states within the human body. It also presents a new strategy for understanding the pathogenesis of related diseases resulting from the abnormal metabolism of thiol compounds.

'Ab Ovo' Chiral Phases and Chiral Reagents for Liquid Chromatographic Separation and Isolation of Enantiomers

The de-novo approach of mixing chirally pure reagents or Cu(II)-L-amino acid complexes in the slurry of silica gel for preparing TLC plates was reported from author's laboratory and was successful for separation and isolation of enantiomers. Using high molar absorptivity molecules, e. g., 1,5-difluoro-2,4-dinitrobenzene and cyanuric chloride, more than 38 new chiral derivatizing reagents were synthesized in our laboratory by straightforward nucleophilic substitution with simple chiral auxiliaries. Besides, (S)-naproxen, (S)-ketoprofen, and (S)-levofloxacin were used as chiral platforms. A conceptual approach using both achiral phases in chromatography for enantioseparation was also adopted. ¹ H NMR and DFT based software were used to explain structures of non-covalent and covalent diastereomeric pairs and determination of configuration and separation mechanism. The methods can be easily used to determine and control enantiomeric purity with advantages over a variety of commercial chiral phases.

Reversed-phase-HPLC enantioseparation and control of enantiomeric purity of duloxetine using a new chiral reagent and recovery of enantiomers

This study reports a rapid and low-cost LC method for control of enantiomeric purity of duloxetine. Though duloxetine, as marketed and administered, is expected to be a single (S)-enantiomer, the analysis of a few commercial branded samples by the method developed and presented here showed that they contain a relatively high percentage of (R)-enantiomer (e.g., 2.71-5.42%, which is undesirable in drug formulations). A new chiral derivatizing reagent [isatinyl-(S)-naproxen amide] was synthesized on (S)-naproxen platform. Diastereomeric derivatives were synthesized under microwave irradiation and were separated using reversed-phase-HPLC on a C₁₈ column. A combination of acetonitrile and triethylammonium phosphate buffer (9 mM, pH 4) as the mobile phase and detection at 273 nm were found successful. The diastereomeric derivatives at preparative scale were separated using open column chromatography, and the native enantiomers were obtained and characterized. The HPLC separation method was validated for detection limit, linearity, accuracy, and precision. The limits of detection of (S,R)-diastereomer and (S,S)-diastereomer were found to be 12 and 16 pg/mL, respectively, for the 20-μL injected volume. The method so developed has a practical significance and greater societal impact in establishing the control of enantiomeric purity and in ensuring the enantiomeric purity of the drug meant for human consumption.

Simultaneous Determination of Chiral Thiol Compounds and Monitoring of Dynamic Changes in Human Urine after Drinking Chinese Korean Ethnic Rice Wine

Chinese Korean ethnic rice wine, a traditional fermented wine made from rice or corn, has antioxidant and antihypertensive activities. Although the determination of amino acids and other nutrients in rice wine has been reported, the existence of chiral thiol compounds has not been published in the literature. Therefore, we established a highly sensitive and selective ultrahigh-performance liquid chromatography-high-resolution mass spectrometry method for simultaneous determination and chiral separation of dl-Cys-GSH, dl-Cys-Cys, and dl-Cys-Hcy based on (R)-(5-(3-isothiocyanatopyrrolidin-1-yl)-5-oxopentyl) triphenylphosphonium derivatization. Three thiol diastereomers were completely separated on a YMC Triart C18 (2.0 × 150 mm, 1.9 μm) column with a resolution value (Rs) ≥ 1.52. The correlation coefficients were ≥0.9996, limit of detection was 2.40-7.20 fmol, and mean recoveries were 83.33-98.59%. Furthermore, fitted curves for dynamic changes in three kinds of chiral thiols in 10 human urine samples after drinking rice wine were drawn. Meanwhile, the metabolic changes in d/l-thiol compounds in human urine were investigated.

Bioanalysis and enantioseparation of dl-carnitine in human plasma by the derivatization approach

BACKGROUND

L-carnitine is an over the counter drug, used to treat disorders like cardiomyopathy, skeletal myopathy, hypoglycemia and hyperammonemia. Preparations containing D-carnitine should be avoided by dialysis patients because it has toxic influence on biochemical processes by inhibiting the carnitine acetyltransferase. Therefore, it is of utmost importance to assess and control the content of D-carnitine.

METHODS

A HPLC method was developed and validated for determination and enantiomeric resolution of DL-carnitine in human plasma by derivatization approach. (S)-Naproxen-based three derivatizing reagents were synthesized and applied.

CONCLUSION

The limit of detection values were found to be 1.26 and 1.35 ng ml(-1) for the two isomers. The method is simple, reproducible, and can be used for routine analysis in laboratories for control of enantiomeric purity of carnitine.

(S)-Naproxen based novel chiral reagent for C–N bond formation: enantioseparation of some β-blockers, determination of absolute configuration and elution order of diastereomers

Symmetrical anhydride proved to be a good reagent for C–N bond formation instead of direct reaction of amino group of analyte with (S)-Npx.

Indirect enantioseparation of proteinogenic amino acids using naproxen-based chiral derivatizing reagent and HPLC

Diastereomers of 18 proteinogenic amino acids were synthesized under microwave irradiation and by vortexing using (S)-naproxen-benzotriazole as chiral derivatizing reagent. The diastereomers synthesized by two approaches were found to be identical in terms of their characterization and chromatographic data. A linear gradient of triethylammonium phosphate (pH 3.5)-acetonitrile (30-65%, within 35 min) was found to be successful using reversed-phase high-performance liquid chromatography for their separation. Detection was carried out at 231 nm and sharp peaks were obtained. The method was validated for accuracy, precision and limit of detection.

Separation and determination of chiral composition in penicillamine tablets by capillary electrophoresis in a broad pH range

A chiral capillary electrophoretic method with nearly full pH window was explored for the separation and determination of dl-penicillamine. A facile one-pot labeling technique was coupled in the method for introduction of chromophore and charge groups onto the analytes to facilitate the electromigration and sensitive detection. By using simply a cost-effective neutral β-cyclodextrin as chiral selector, baseline separation of the dl-penicillamine was achieved from pH 2.0 to over pH 10. Quantification of standard d- and l-penicillamines was demonstrated by taking pH 4.5, 7.4, and 9.7 as the representatives of acidic, neutral, and basic conditions. The working curves were constructed between peak area and concentration, having linear ranges of 8.56-8.56 × 10(2) μg/mL for pH 4.5 and 8.56-1.71 × 10(3) μg/mL for pH 7.4 and 9.7, with correlation coefficients all better than 0.999. The limit of detection (S/N = 3) was 2.58 μg/mL in acidic and neutral conditions or 1.41 μg/mL in basic condition. The method was further validated by assaying the commercial penicillamine tablets, applicable to quantification of the effective enantiomer and the trace impurity of l-penicillamine at a content of down to 0.2, 0.6, and 2.0% for pH 9.7, 4.5, and 7.4, respectively. The recovery determined by spiking technique was in a range from 93.1 to 105 %. The method is easily extendable to the analysis of other chiral amines or amino acids.

Reversed-phase high-performance liquid chromatographic enantioresolution of six beta-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

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.