Application of insoluble amylose 3,5-dimethylphenylcarbamate attached to the surface of silica for separation of enantiomers in high-performance liquid chromatography

Author: Nino Beridze
Keywords: enantiomers, covalently attached
Annotation:

Separation of enantiomers belongs to one of the hot topics in chemistry from both, practical and theoretical points of view. The practical importance of this topic is warranted by the fact that individual enantiomers of chiral drugs may exhibit very different bioactivities and/or toxicities. For any chiral entities interacting with a chiral environment such as biological organisms or chiral separation media, stereospecific differences can be manifested in a variety of ways. For instance, enantiomers of chiral pesticides degrading through enzymatic pathways may exhibit differences in environmental activity, persistence, or end products. About more than half of the drugs currently in use are chiral compounds of them are marketed as racemates consisting of an equimolar mixture of two enantiomers. Enantiomers of a chiral drug substance may have dramatically different pharmacological activities and different pharmacokinetic and pharmacodynamic properties. The issue of drug chirality is now a major topic in the design and development of new drugs, underpinned by a new understanding of the role of molecular recognition in many pharmacologically relevant events. Thus, chiral separations are significant to investigators pursuing a broad array of interests. Analytical and preparative separation of enantiomers was considered as the most difficult problem in separation science for many years due to identical properties of enantiomers in achiral environment. Only in 1980s chiral columns for high-performance liquid chromatographic (HPLC) separation of enantiomers became commercially available. Over the past 30 years, chiral separations have become an important tool in the separation science arsenal. Among all chiral stationary phases (CSP) available today for HPLC separation of enantiomers, polysaccharide derivatives are considered to be the most useful materials. Polysaccharide-based CSPs are commonly prepared by physical coating of polysaccharide derivative onto the surface of silica. This method of CSP preparation has several advantages: First of all this is a single-step fast process that does not require any specific prefunctionalization of the surface. In addition, the content of the chiral selector in GSP can be varried easily. The major disadvantage of coated-type polysaccharide- based CSPs is that these materials are not compatible with those organic solvents which dissolve the chiral selector and thus, can damage the column. In order to overcome this problem the current trend is to immobilize polysaccharidederivative onto the surface of inert carrier (commonly silica) by transforming it after coating onto the surface into insoluble material or creating covalent linkage between the polysaccharide derivative and silica. This kind of treatment significantly broadens the applicability of polysaccharide-based CSPs and makes it possible to use as chiral selectors some of the derivatives of polysaccharides which were not suitable for this purpose before due to solubility in solvents used as components of HPLC mobile phases. The main aim of the research of the present paper was to study one of these new chiral selectors, in particular, insoluble amylose 3,5-dimethylphenylcarbamate covalently attached to the surface of silica was be used to study the enantiomeric separations, and it was compared with the layered amylose 3,5-dimethylphenylcarbamate chiral selector, using different mobile phases. . randomly selected acid and base drugs were used in the research.