Chiral stationary phases starch

The use of chiral stationary phases (CSP) in liquid chromatography continues to grow at an impressive rate. These CSPs contain natural materials such as cellulose and starch as well as totally synthetic materials, utilizing enantioselective and retentive mechanisms ranging from inclusion complexation to Ti-electron interactions. The major structural features found in chiral stationary phases include cellulose, starch, cyclodextrins, synthetic polymers, proteins, crown ethers, metal complexes, and aromatic w-electron systems. 

Chiral stationary phases can consist of starch, which for instance... 

It has long been perceived that chromatography of enantiomers upon a chiral stationary phase (CSP) might, in principle, result in separation of the enantiomers. Owing to the potential utility of such a resolution procedure, a great many workers have attempted to so effect resolutions. Most early attempts involve empirically chosen, readily accessible CSP s, starches, modified celluloses, wool) with varying... 

The third approach to Isomer separation by HPLC Is based on the use of chiral stationary phases. The phase may be Inherently optically active (e.g., powdered d-quartz or starch) or may be a non-optlcally active material coated with or reacted with an optically active moiety. As early as 1938, enantiomers of a camphor compound were separated on a lactose column (54), and twenty years later, alumina coated with ortartarlc acid was used to separate Isomers of mandellc acid and phenylglyclne-methyl ester... 

Before synthetic chiral stationary phases were developed, attempts were made to use naturally occurring chiral materials for the stationary phase. Quartz, wool, lactose and starch were inadequate but triacetylated cellulose has met with some success. The synthetic stationary phases introduced by Pirkle are able to interact with solute enantiomers in three ways, one of which is stereochemically dependent. Typically these interactions are based on hydrogen bonding, charge transfer (rc-donoi -acceptor based) and steric repulsive types. An independent chiral stationary phase therefore consists of chiral molecules each with three sites of interaction bound to a silica (or other) support. Early work in this area demonstrated that 5-arginine bound to Sephadex would resolve 3,4-dihydroxy-phenylalanine, and that direct resolution of chiral helicenes could be accomplished with columns packed with 2-(2,4,5,7-tetranitro-9-fluorenylideneaminoxy)-propionamide or tri-P-naphthol-diphosphate amide. Amino acid esters have also been resolved with a silica bound chiral binaphthyl crown ether, but better separations are achieved with A-acylated amino acid derivatives with amino-acid derived chiral stationary phases. 

It is worth mentioning that natural products, due to their enantiopurity, play an important technical function in the development of suitable methods for chiral separations. Cellulose and amylose, which are easily accessible chiral polymers, after derivatization, are used as chiral stationary phases for both HPLC and TLC [29-31]. Microbial degradation of starch yielded CDs, -CD-bonded silica gel provide the most popular chiral stationary phases. 

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