Chiral recognition strategy

In earlier papers, enantioseparations of charged analytes with neutral chiral selectors were attributed to CZE and the enantioseparations of neutral analytes with charged chiral selectors to EKC. However, from the mechanistic point of view, there is no principal difference whether an analyte or a chiral selector is charged. Actually, it is the subject of convention which counterpart of chiral recognition process will be named selectand and which one chiral selector. The reciprocal chiral recognition strategy for a design of effective chiral selectors proposed by Pirkle and co-workers in HPLC is based on this philosophy [9] and that principle certainly applies for enantioseparations in EKC also [10]. 

The short-end injection was also used in a paper by Perrin et al. [28]. They saw a very high chiral recognition capability of highly sulfated cyclodextrins (HS-CD). Using a test set of 27 amino acid derivatives, the application of HS-a-CD, HS-fl-CD, and HS-y-CD in a 5% w/v concentration allowed the separation of 26 compounds, of which 22 had a Rs > 2. From their experiments, a screening and optimization scheme was derived (Figure 3.3), and based on this scheme, a separation strategy was defined... 

Many researchers have put a considerable amount of effort into studies of the chiral recognition mechanisms (using, e.g., NMR and molecular modeling), but yet the choice of chiral selector or chiral phase for a new compound is often based on trial and error. Different strategies for chiral method development have been presented by many of the retailers of chiral columns as a service for the customers. In addition to the information supplied by these retailers, another source of knowledge is Chirbase, a database that contains more than 50,000 HPLC separations of more than 15,000 different chiral substances [61], which also can provide guidance to the analytical chemist. 

One popular strategy to isolate and identify the binding domain of a protein type CSP is to compare the retention and enantioselectivity behaviour of CSPs prepared with whole proteins and with isolated protein domains. Such a study has been performed by Pinkerton et al. [204) with turkey ovomucoid. Columns made from whole-turkey ovomucoid displayed chiral activity toward many racemates, whereas the fused first and second domain resolved only a selected number of aromatic weak bases. The first and second domains independently expressed no appreciable chiral recognition activity. The third domain, however, exhibited enantioselective protein binding for fused-ring aromatic weak acids, and glycosylation of this domain did not affect chiral recognition. 

Chiral Recognition Using the Chiral Anion Strategy... 

Coordination interactions represent another strategy for producing chiral recognition in gas chromatography. Thus, the chiral metal coordination compound dicarbonylrhodium(i)-3-trifluoroacetyl-(lR)-campho-... 

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