Preparative resolution of enantiomers of prostaglandin precursors by liquid chromatography on a chiral stationary phase

Chiral separation of new sulfonamide derivatives and evaluation of their enantioselective affinity for human carbonic anhydrase II by microscale thermophoresis and surface plasmon resonance

The aim of this study was to develop a method combining chiral separation and biophysical techniques to evaluate the enantioselective affinity of original sulfonamide derivatives towards their therapeutic target, the human carbonic anhydrase II (hACII). The first step consisted in the preparation of the enantiomers by chromatographic separation. The performances of HPLC and Supercritical Fluid Chromatography (SFC) were studied at the analytical scale by optimization of various experimental conditions using adsorbed polysaccharide chiral stationary phases (amylose AD-H and cellulose OD-H). Since SFC allowed obtaining higher enantioresolutions per time unit, it was selected for the semi-preparative scale and successfully used to isolate each enantiomer with a satisfactory enantiomeric purity (>98%). Secondly, microscale thermophoresis (MST) method and surface plasmon resonance (SPR) used as reference method were developed to measure potential enantioselective affinities of these enantiomers towards the hACII. The optimizations of both methods were performed using a reference compound, i.e. acetazolamide, which affinity for hCAII has previously been demonstrated. For all compounds, K_D values obtained using MST and SPR were in good agreement, leading to similar affinity scales despite both approaches totally differ (labeling for MST versus immobilization of the protein for SPR). The equilibrium dissociation constants of our original compounds for the hCAII were in the range 100-1000nM and an enantioselectivity was observed using the MST and SPR methods for the diarylpyrazole 2. Finally, by comparing the MST and SPR techniques, MST appears especially adapted for further screening of a series of sulfonamide derivatives due to the lower time required to estimate a binding constant while consuming as little hCAII as SPR.

Rapid and high throughput separation technologies—Steady state recycling and supercritical fluid chromatography for chiral resolution of pharmaceutical intermediates

The SSR and SFC techniques were used for the enantiomeric resolution of three pharmaceutical intermediates at various sample scales. The separation conditions, the sample purities and yields, the productivities and the solvent consumptions were discussed in three case studies in this paper. In case (I), the SSR process was used for a low selectivity resolution of 2.0 kg of pharmaceutical intermediate. By using this separation process, a productivity of 750 g racemate/kg stationary phase/day was achieved, while solvent usage was minimized ( approximately 200 l/kg racemate). Case (II) pertained to the effectiveness of the SSR process. Productivity using SSR techniques increased by a factor of 4.5, while solvent usage decreased by a factor of 4.1 when compared to the productivity and solvent usage of batch HPLC. Case (III) compared SFC purification to HPLC purification. The SFC process was more effective in terms of an increase in productivity and a reduction in solvent usage. Based on these results, it appears that SSR and SFC are very useful choices at the early stage of the drug development for a high throughput and a rapid turn around of samples.

Optimization of the preparative separation of a chiral pharmaceutical intermediate by high performance liquid chromatography

The prediction of optimal conditions of the preparative HPLC separation of the enantiomers of a pharmaceutical intermediate was accomplished by employing analytical chromatographic data, i.e. sample injections at low concentrations. Various temperatures and mobile phase conditions were studied. It was assumed that the sample loadability of the stationary phase is constant for a constant value of the separation factor and different mobile phase conditions and temperatures. Using this assumption, possible production rates can be compared for different method conditions. Overloading experiments were carried out to verify that the procedure employed is adequate. It was found that the optimization approach used, changing the mobile phase composition and temperature to achieve the shortest cycle time while keeping the separation factor constant, could be applied to improve the production rate of the separation.

Resolution of a racemic pharmaceutical intermediate

Preparative HPLC and simulated moving bed (SMB) chromatography were used to resolve significant quantities of a racemic pharmaceutical intermediate. In addition, smaller scale studies using closed-loop recycling and steady state recycling (SSR) were performed so that a meaningful comparison of all these techniques could be made using the same real world separation. A highly optimized, six-column SMB process was clearly the superior technique and was used for the process-scale (247 kg of racemate) resolution. At the more moderate lab-scale (33 kg of racemate and 19 kg of racemate), a frequently used but less optimized eight-column SMB process was used. It was found that SSR was comparable to the lab-scale SMB process in productivity and solvent consumption. Thus, it appears that SSR can be a useful choice at such moderate scales. Finally, at moderate scales when neither SSR nor SMB is available, it was found that acceptable results were obtained with both closed-loop recycling and with a two-step preparative process.

Batch and simulated moving bed chromatographic resolution of a pharmaceutical racemate

The preparative chromatographic resolution of racemates has become over the past few years a standard approach for the generation of enantiomers in pharmaceutical research and development. This paper will discuss the chromatographic resolution of a racemic pharmaceutical intermediate. Initial analytical method development to determine the best preparative conditions will be presented. Batch resolution of kg quantities of racemate followed by the simulated moving bed resolution of tens and hundreds of kg of racemate will also be discussed. Finally the different approaches used for the separation will be compared.

Preparative chromatographic resolution of enantiomers using polar organic solvents with polysaccharide chiral stationary phases

The preparative chromatographic resolution of racemic mixtures is rapidly becoming a standard approach for the generation of enantiomers in pharmaceutical research and development. This paper will discuss the optical resolution of numerous pharmaceutical intermediates and final products using polar organic solvents with polysaccharide chiral stationary phases. The advantages of this approach compared to more traditional mobile phases for preparative separations will be presented. In addition the ability to reverse elution order using polar organic solvents will be presented.

Chromatographic resolution of the enantiomers of a pharmaceutical intermediate from the milligram to the kilogram scale

The preparative chromatographic resolution of racemic mixtures is rapidly becoming a standard approach for the generation of enantiomers in pharmaceutical R&D. This paper will discuss the optical resolution of a pharmaceutical intermediate as the separation is scaled up from the milligram to the kilogram scale. Difficulties encountered and their solutions at each scale will be discussed. In addition, the exploration of Simulated Moving Bed (SMB) for the separation will also be discussed. Finally, a comparison of the productivities and solvent consumption for each method and scale will be presented.

Preparative chromatographic separation of enantiomers

The potential of the chromatographic separation of enantiomers on a preparative scale as a tool for the isolation of optically pure compounds is gaining increasing recognition. This review surveys the different chiral stationary phases (CSPs) used for preparative chromatography, emphasizing the advantages and drawbacks of each. The strategy to be followed for preparative separations is discussed and tables summarizing separations reported in the literature give an overview of practical applications. Cellulose triacetate has been used most frequently, probably because of its broad application range and its low production costs in comparison with more recently introduced CSPs. Nevertheless, the high efficiency of some of the novel CSPs is likely to contribute to the further development and expansion of the method.

Analytical and preparative resolution of enantiomers of prostaglandin precursors and prostaglandins by liquid chromatography on derivatized cellulose chiral stationary phases

Analytical methods were developed for the separation of the enantiomers of four cyclopentenone precursors of prostaglandins. The resolution obtained is correlated with the chemical environment around the chiral center of the cyclopentenones. The analytical methods were scaled up to preparative loadings and the chromatographic parameters were varied to determine their effect on the preparative separations. The correlation between analytical resolution and preparative resolution was also investigated. In addition to the precursors, the preparative resolution of the enantiomers of a synthetic prostaglandin analogue was investigated.