Synthesis, Enantiomeric Resolution and Biological Evaluation of HIV Capsid Inhibition Activity for Racemic, (S)- and (R)-PF74

PF74 is a capsid-targeting inhibitor of HIV replication that effectively perturbs the highly sensitive viral uncoating process. A lack of information regarding the optical purity (enantiomeric excess) of the single stereogenic centre of PF74 has resulted in ambiguity as to the potency of different samples of this compound. Herein is described the synthesis of enantiomerically enriched (S)- and (R)-PF74 and further enrichment of the samples (≥98%) using chiral HPLC resolution. The biological activities of each enantiomer were then evaluated, which determined (S)-PF74 (IC50 1.5 µM) to be significantly more active than (R)-PF74 (IC50 19 µM). Computational docking studies were then conducted to rationalise this large discrepancy in activity, which indicated different binding conformations for each enantiomer. The binding energy of the conformation adopted by the more active (S)-PF74 (ΔG = −73.8 kcal/mol) was calculated to be more favourable than the conformation adopted by the less active (R)-enantiomer (ΔG = −55.8 kcal/mol) in agreement with experimental observations.

Chemical derivatization in combination with supercritical fluid chromatography to improve resolution of stereoisomers

Aim: Quantification of stereoisomers in biological matrices is of pivotal importance for drug development. Supercritical fluid chromatography paired with chiral stationary phases is the gold standard for resolution of enantiomers. However, this technique often proves inadequate for resolution of polar stereoisomers. Materials & methods: A combination of achiral chemical derivatization with supercritical fluid chromatography using chiral stationary columns to improve enantiomeric resolution is described. Results: Separation of four possible stereoisomers of linerixibat was achieved after derivatization with 3N HCl in n-butanol within 12 min (case1). Derivatization with acetic, propionic, butyric, isobutyric, valeric and isovaleric anhydrides significantly improved the separation of stereoisomers (case 2 and 3) within 10 min. The best stereoisomeric resolution was achieved using valeric and isovaleric anhydrides.

Research progress of chiral ligand exchange stationary phases in the enantiomer resolution

The structure of chiral drugs contains at least one asymmetric center. When the enantiomers act on the human body, they are recognized by chiral receptors and enzymes in vivo, which will show different physiological effects and even adverse reactions. Therefore, it is very important for the development of chiral pharmacy to obtain chiral enantiomers with a single configuration by racemic resolution. Some general impurities will be introduced in the production of chiral drugs, thus the detection of impurities is also a crucial step in the quality control of chiral medicines. The chiral ligand exchange stationary phase has a strong recognition effect on enantiomer analytes with multiple chelating sites, and is very suitable for the separation and control of biological samples such as amino acids. In this work, the development of chiral ligand exchange stationary phases in enantiomeric resolution is reviewed, which is expected to provide a basis for the quality control of complex chiral drug components.

Enantiomeric Resolution and Absolute Configuration of a Chiral δ-Lactam, Useful Intermediate for the Synthesis of Bioactive Compounds

During the past several years, the frequency of discovery of new molecular entities based on γ- or δ-lactam scaffolds has increased continuously. Most of them are characterized by the presence of at least one chiral center. Herein, we present the preparation, isolation and the absolute configuration assignment of enantiomeric 2-(4-bromophenyl)-1-isobutyl-6-oxopiperidin-3-carboxylic acid (trans-1). For the preparation of racemic trans-1, the Castagnoli-Cushman reaction was employed. (Semi)-preparative enantioselective HPLC allowed to obtain enantiomerically pure trans-1 whose absolute configuration was assigned by X-ray diffractometry. Compound (+)-(2R,3R)-1 represents a reference compound for the configurational study of structurally related lactams.

Enantioselective Chromatographic Analysis of Formoterol Fumarate using Chiral Mobile Phase Additives and Achiral Core-Shell Column

<p>A simple, robust, cost-effective, and rapid RP-HPLC method was developed for the separation of enantiomers of formoterol. The separation was achieved by the chiral mobile phase additive technique on an achiral column. Formoterol is a bronchodilator that consists of 50:50 S, S-formoterol and R, R-formoterol. The bronchodilator activity is attributed to R, R-formoterol. Hence, it is important to develop a method to separate the enantiomers of formoterol. Various factors affecting enantiomeric resolution were investigated and optimized. The enantiomers of formoterol were successfully separated with a resolution of 2.57 with a run-time of 9 minutes. The method was validated in accordance with ICH guidelines. The validated method was successfully applied to the marketed formulation of arformoterol. </p>

Enantioselective Chromatographic Analysis of Formoterol Fumarate using Chiral Mobile Phase Additives and Achiral Core-Shell Column

<p>A simple, robust, cost-effective, and rapid RP-HPLC method was developed for the separation of enantiomers of formoterol. The separation was achieved by the chiral mobile phase additive technique on an achiral column. Formoterol is a bronchodilator that consists of 50:50 S, S-formoterol and R, R-formoterol. The bronchodilator activity is attributed to R, R-formoterol. Hence, it is important to develop a method to separate the enantiomers of formoterol. Various factors affecting enantiomeric resolution were investigated and optimized. The enantiomers of formoterol were successfully separated with a resolution of 2.57 with a run-time of 9 minutes. The method was validated in accordance with ICH guidelines. The validated method was successfully applied to the marketed formulation of arformoterol. </p>

A Validated LC Method for the Enantiomeric Separation of EAI045 on Chiral Stationary Phase

A simple and accurate chiral liquid chromatographic method was developed for enantiomeric resolution and determination of 2-(5-fluoro-2-hydroxyphenyl)-2-(1-oxo-2,3-dihydro-1H-isoindol-2-yl)-N-(1,3-thiazol-2-yl)acetamide (EAI045). The enantiomers of EAI045 were baseline resolved on a Chiralpak AD-H (250 mm × 4.6 mm, 5 μm) column using a mobile phase system containing n-hexane: 2-propanol (75: 25 v/v) at a flow rate of 1 mL min−1 at 30°C. The eluted analytes were subsequently detected with an ultraviolet detector at 254 nm. The effects of organic modifiers and temperature on the enantioselectivity and resolution of the enantiomers were evaluated. The calibration curves were plotted within the concentration range between 2 and 600 μg mL−1 (n = 11), and recoveries between 98.74% and 101.52% were obtained, with relative standard deviation &lt; 1.4%. The limit of detection and limit of quantitation for R-enantiomer were 0.94 and 3.07 μg mL−1 and for S-enantiomer were 0.86 and 2.84 μg mL−1, respectively. The validated method was found to be suitable for enantiomeric separation and sufficiently accurate for the determination of enantiomeric purity of EAI045 in bulk drugs.

Chromatographic and Computational Studies on the Chiral Recognition of Sulfated β-Cyclodextrin on Enantiomeric Separation of Milnacipran

<p></p><p>A new, cost-effective and fast chromatographic method using sulfated β-cyclodextrin (SβCD) as a chiral mobile phase additive (CMPA) was developed and validated for the enantiomeric separation of milnacipran. Milnacipran is an anti-depressant drug. Levo-milnacipran is the active enantiomer with less adverse effects than dextro-milnacipran. Hence, it is imperative to separate the enantiomers of milnacipran. Various parameters affecting enantiomeric resolution, for instance, the effect of type and concentration of cyclodextrins, the effect of pH of the mobile phase, effect of type and concentration of the organic solvent in the mobile phase and effect of type of achiral column, were investigated. We demonstrated successful resolution of enantiomers of milnacipran on reverse-phase HPLC with Kinetex C8 column (150x4.6mm, 5µ), using a mobile phase consisting of 18:82 v/v acetonitrile: 10mM sodium dihydrogen orthophosphate dihydrate buffer pH 3.0 (adjusted with orthophosphoric acid) containing 10mM SβCD with a flow rate 1.0 ml/minute. The column temperature was ambient and UV detection was carried out at 227 nm with an injection volume of 20µl. This method for enantiomeric separation of milnacipran was validated in accordance with ICH guidelines and successfully applied to the marketed formulation of Levomilnacipran. Furthermore, molecular docking was used to identify the chiral recognition mechanism. The results of molecular docking corroborated with our experimental findings.</p><br><p></p>