Preparative separation and analysis of the enantiomers of [3H]Abbott-69992, an HIV anti-infective nucleoside, by ligand-exchange high-performance liquid chromatography

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.

Analytical and semipreparative resolution of enatiomers of albendazole sulfoxide by HPLC on amylose tris (3,5-dimethylphenylcarbamate) chiral stationary phases

Broad spectrum anthelmintic agent-albendazole sulfoxide (ABZSO) have been separated and semiprepared on amylose tris (3,5-dimethylphenylcarbamate) chiral stationary phases by HPLC using mobile phases contained with n-hexane and different alcohols. For analytical separation the influence of the nature and content of alcoholic modifiers on separation were systemically studied. Then, the analytical methods were scaled up to semipreparative loading to obtain small quantities (about 1 g) of both ABZSO enantiomers. Especially, different loading amounts were investigated for their effect on various parameters of semipreparative HPLC. In addition, optical rotation and circular dichroism (CD) of both ABZSO enantiomers collected were determined and single enantiomers were found stable in configuration for 1 year.

Streptavidin chiral stationary phase for the separation of adenosine enantiomers

In this paper, a microbore column packed with streptavidin particles was used, at various temperatures (0-24 degrees C), to separate the adenosine enantiomers by HPLC. Using an aqueous mobile phase, the apparent enantioseparation was high for a small molecule, varying from 11.5 at 0 degrees C to 6.2 at 24 degrees C. From the experiments carried out with a streptavidin-biotin complex stationary phase, it was demonstrated that the blockage of the biotin sites of the immobilized streptavidin was responsible for a strong decrease in the enantioselectivity via a direct and/or an indirect effect. From the analysis of the concentration dependencies of the solute retention factor, it was also shown that a reduction of the D-adenosine specific binding sites occurred at the lowest temperature. The thermodynamic parameters determined from the van't Hoff plots indicated that the D-adenosine binding to the streptavidin specific sites was enthalpically driven.

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.

Resolution of enantiomers of uridine analogs, potential antiviral agents

Racemic mixtures of 5-substituted carbocyclic analogs of uracil nucleosides, 2"- and 3"-furyl, 2"- and 3"-thienyl and 2"-selenienyl, potentially anti-viral agents, were resolved using amylose tris(3,5-dimethylphenyl)carbamate as the stationary phase. The mobile phase was n-hexane with ethanol or 2-propanol. Effects of some structural features on the extent of discrimination between the enantiomers were examined through the selectivity and resolution factors as well as the elution order. The structural features were as follows; the type and position of the hetero-atom O, S or Se, in the cyclopentadienyl substituent 5 of the uracil and hydroxymethyl vs. acetoxymethyl groups on the cyclopentene moiety of the uridine analogs. It appeared that effects of the structural features on the separation were solvent dependent, with some very unusual solvent effects. For example, average retention, which did not follow the polarity of the mobile phase modifiers, was much higher when ethanol was used compared to 2-propanol. Also, the elution order of the two enantiomers of several pairs was reversed when ethanol was changed to 2-propanol. In general, ethanol affected higher selectivity and resolution of all the enantiomeric pairs.