Chirality chromatography

Neural networks were trained on the basis of these codes to predict chiralit> -dependent properties in enantioselective reactions [42] and in chiral chromatography [43]. A detailed description of the chirality codes is given in the Tutorial in Section 8,6,... 

Analytical techniques that utilise biopolymers, ie, natural macromolecules such as proteias, nucleic acids, and polysaccharides that compose living substances, represent a rapidly expanding field. The number of appHcations is large and thus uses hereia are limited to chiral chromatography, immunology, and biosensors. 

Chiral Chromatography. Chiral chromatography is used for the analysis of enantiomers, most useful for separations of pharmaceuticals and biochemical compounds (see Biopolymers, analytical techniques). There are several types of chiral stationary phases those that use attractive interactions, metal ligands, inclusion complexes, and protein complexes. The separation of optical isomers has important ramifications, especially in biochemistry and pharmaceutical chemistry, where one form of a compound may be bioactive and the other inactive, inhibitory, or toxic. 

In recent years the solid-phase hydrosilylation reaction was successfully employed for synthesis of hydrolytically stable surface chemical compounds with Si-C bonds. Of special interest is application of this method for attachment of functional olefins, in particular of acrolein and some chiral ligands. Such matrices can be used for subsequent immobilization of a wide range of amine-containing organic reagents and in chiral chromatography. 

T. E. Beesley and R. P. W. Scott, Chiral Chromatography, John Wiley and Sons, Chichester-New York, (1998), 46. 

The screening was performed in a way similar to that of Welch, except that it involved the use of a spectropolarimeter instead of chiral chromatography to determine the selectivity. Equal amounts of the target racemate 17 were added into each of the 16 wells containing beads and the ellipticity of the supernatant liquid in each well was measured after equilibrating for 24 h at the wavelength of the maximum adsorption (260 nm). Knowing the specific ellipticity of one enantiomerically pure... 

The past two decades have seen remarkable advances in chiral chromatography, as only 20 years ago, the direct resolution of enantiomers by chromatography was still considered to be an impressive technical achievement. 

In this chapter, we will discuss the present status of CHIRBASE and describe the various ways in which two (2D) or three-dimensional (3D) chemical structure queries can be built and submitted to the searching system. In particular, the ability of this information system to locate and display neighboring compounds in which specified molecular fragments or partial structures are attached is one of the most important features because this is precisely the type of query that chemists are inclined to express and interpret the answers. Another aspect of the project has been concerned with the interdisciplinary use of CHIRBASE. We have attempted to produce a series of interactive tools that are designed to help the specialists or novices from different fields who have no particular expertise in chiral chromatography or in searching a chemical database. 

CHIRSOURCE aims to explore the use of chiral chromatography for combinatorial chemistry approaches. Combinatorial chemistry, as well as parallel synthesis. 

Utilization of intelligent systems in chiral chromatography starts with an original project called CHIRULE developed by Stauffer and Dessy [36], who combined similarity searching and an expert system application for CSP prediction. This issue has recently been reconsidered by Bryant and co-workers with the first development of an expert system for the choice of Pirkle-type CSPs [37]. 

Today, the use of CHIRBASE as a tool in aiding the chemist in the identification of appropriate CSPs has produced impressive and valuable results. Although recent developments diminish the need for domain expertise, today the user must possess a certain level of knowledge of analytical chemistry and chiral chromatography. Nevertheless, further refinements will notably reduce this required level of expertise. Part of this effort will include the design of an expert system which will provide rule sets for each CSP in a given sample search context. The expert system will also be able to query the user about the specific requisites for each sample (scale, solubility, etc.) and generate rules which will indicate a ranked list of CSPs as well their most suitable experimental conditions (mobile phase, temperature, pH, etc.). 

The Cyclobond materials are some of the most effective in separating isiomers generally and their development continues. It is likely that chiral chromatography will become increasingly important as the products from biotechnology continue to proliferate into the pharmaceutical field. 

The design of simulated moving bed chromatography and its application to the separation of cycloheptanone and cyclopentanone as test substances to validate the system for subsequent chiral chromatography has been described.27 Briefly, eight silica-packed columns were hooked up in series to form a cyclic flow path. On the first pair, preliminary separation of the components was performed, with the less-retained raffinate being directed to waste. Following the second pair of columns, eluent was added. After the... 

Volume inefficient chiral chromatography required to deliver a single enantiomer Separation at final API necessitated processing excess material through the synthesis to give the desired amount... 

Volume inefficient chiral chromatography required to deliver a single enantiomer... 

Evaluation of the above route against our initial target objectives for the synthesis of taranabant indicated a high level of success, not just for the primary objectives of removing the tin chemistry and chiral chromatography, but for a number of other process improvements (Table 9.2). Of particular note was that the three crystalline intermediates were key for purification, first the phenethylamine salt 12 for the classical resolution, secondly the HC1 salt of amine 2 allowed for upgrade of diastereomeric purity, and finally the API allowed for upgrade of enantiomeric purity via initial removal of racemic material. 

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