Chiral polysaccharide type

Girod, M., Chankvetadze, B., and Blaschke, G. (2000) Enantioseparations in non-aqueous capillary electrochromatography using polysaccharide type chiral stationary phases, J. Chromatogr. A 887, 439-455. 

K. Tachibana and A. Ohnishi, Reversed-phase hquid chromatographic separation of enantiomers on polysaccharide type chiral stationary phase, J. Chromatogr. A 906 (2001), 127-154. 

ENANTIOSEPARATION OF PHARMACELTICALLY RELEVANT CHIRAL COMPOLNUS USING POLYSACCHARIDE TYPE CSPs... 

Fig. 7.5 Su mma7 of the chemical structures and tradenames of the most important cellulose and amylose derivatives incorporated in polysaccharide-type chiral stationary phases.

However, the (undisclosed) proprietary immobilization process appears to modify the enantiomer separation characteristics as compared to the coated versions [145, 146]. Ghanem et al. compared the chiral recognition profile of a coated CHIRALPAK AD CSPs with that of the immobilized version, employing hexane/ 2-propanol containing TEA (0.1%) as mobile phase [145]. They reported superior enantiomer separation for the coated CSP, with some analytes failing to resolve on the immobilized version. These differences in the enantiomer separation capacity of coated and immobilized polysaccharide-type CSPs may complicate attempts at direct method transfer. 

Chankvetadze, B.,Yamamoto, C., Okamoto,Y. Enantioseparation of selected chiral sulfoxides using polysaccharide-type chiral stationary phases and polar organic, polar aqueous-organic and normal-phase eluents,/. Chromatogr. A,... 

Chankvetadze, B., Kartozia, 1., Yamamoto, C., Okamoto, Y. Comparative enantioseparation of selected chiral drugs on four different polysaccharide-type chiral stationary phases using polar organic mobile phases,/. Pharmaceut. Biomed., 2001, 27, 467-478. 

The separation of the enantiomers of the chiral p-blocker propranolol in capillary HPLC using a polysaccharide type CSP is shown in Fig. 4 [120]. The capillary format requires aproximately 106 times less stationary and mobile phases, while offering separation characteristics at least adequate or better than that achieved with common-size columns. 

Zhe X, Wenwei X, Hua H, Lirui P, Xu X (2008) Direct chiral resolution and its application to the determination of the pesticide tetramethiin in soil by high-performance liquid chromatography using polysaccharide-type chiral statitmary phase. J Chromatogr Sci 46 783-786... 

The type of CSPs used have to fulfil the same requirements (resistance, loadabil-ity) as do classical chiral HPLC separations at preparative level [99], although different particle size silica supports are sometimes needed [10]. Again, to date the polysaccharide-derived CSPs have been the most studied in SMB systems, and a large number of racemic compounds have been successfully resolved in this way [95-98, 100-108]. Nevertheless, some applications can also be found with CSPs derived from polyacrylamides [11], Pirkle-type chiral selectors [10] and cyclodextrin derivatives [109]. A system to evaporate the collected fractions and to recover and recycle solvent is sometimes coupled to the SMB. In this context the application of the technique to gas can be advantageous in some cases because this part of the process can be omitted [109]. 

Examples with other Pirkle-type CSPs have also been described [139, 140]. In relation to polysaccharides coated onto silica gel, they have shown long-term stability in this operation mode [141, 142], and thus are also potentially good chiral selectors for preparative SFC [21]. In that context, the separation of racemic gliben-clamide analogues (7, Fig. 1-3) on cellulose- and amylose-derived CSPs was described [143]. 

Mourier s report was quickly followed by successful enantiomeric resolutions on stationary phases bearing other types of chiral selectors, including native and deriva-tized cyclodextrins and derivatized polysaccharides. Many chiral compounds of pharmaceutical interest have now been resolved by packed column SFC, including antimalarials, (3-blockers, and antivirals. A summary is provided in Table 12-2. Most of the applications have utilized modified CO, as the eluent. 

Many chiral compounds can be used as selectors, for example, chiral metal complexes, native and modified cyclodextrins, crown ethers, macrocyclic antibiotics, noncyclic oligosaccharides, and polysaccharides all have been shown to be useful for efficient separation of different types of compounds. 

Chiral separations result from the formation of transient diastereomeric complexes between stationary phases, analytes, and mobile phases. Therefore, a column is the heart of chiral chromatography as in other forms of chromatography. Most chiral stationary phases designed for normal phase HPLC are also suitable for packed column SFC with the exception of protein-based chiral stationary phases. It was estimated that over 200 chiral stationary phases are commercially available [72]. Typical chiral stationary phases used in SFC include Pirkle-type, polysaccharide-based, inclusion-type, and cross-linked polymer-based phases. 

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