Derivatizing agents achiral

Derivatization with Optically Active Reagents and Separation on Achiral Columns. This method has been reviewed (65) a great number of homochiral derivatizing agents (HD A) are described together with many appHcations. An important group is the chloroformate HD As. The reaction of chloroformate HD As with racemic, amino-containing compounds yields carbamates, which are easily separated on conventional hplc columns, eg (66),... 

This strategy is the one most commonly used for the analytical determination of ena-tiopurity. A given racemate is reacted with a unichiral derivatizing agent, and the resulting pair of diastereomers is separated on an achiral stationary phase, in most of the cases on a reversed-phase type (Fig. 7-2). 

Let us assume that a given compound has a purity of 98 % ee, and that this compound is reacted with a derivatizing agent which has also a purity of 98 % ee. The two major compounds plus the minor impurities in the compound to be analyzed and the derivatizing agent will create a set of four diastereomers. Two pairs of diastereomers (-i-)-A(-i-)B and (-)-A(-)-B as well as (- )-A(-i-)-B and (-i-)-A(-)-B are enantiomeric pairs, and thus elute together on an achiral column. Therefore, a peak area of 98.011 % will be detected for (-i-)-A(-i-)-B, which leads to a purity of 96.03 % ee for (-i-)-A. This is a quite significant deviation from the true value for (-i-)-A. 

Amino acid duplications, in sulfonamide resistance, 23 505 Amino acid inhibitors, 13 300-302 Amino acid racemization dating, 5 752 Amino acid residues, 9 494 26 376 Amino acids, 2 554-618 20 447 achiral derivatizing agents, 6 96t analysis, 2 596-600 analysis in green coffee, 7 253t analysis in roasted, brewed, and instant coffee, 7 255t... 

AT-Hydroxyacetamide, 14 127 4-Hydroxyacetanilide, 2 670 physical properties of, 2 666t Hydroxyacetic acid, 14 126-130 applications for, 14 128-129 grades of, 14 128 production of, 14 127-128 Hydroxy acids, achiral derivatizing agents, 6 96t... 

Phenols. See also Phenol Phenolic entries achiral derivatizing agents, 6 96t alkylation, 2 196-197, 212-214 aroma chemicals, 3 243-246 aroma compounds in roasted coffee, 7 256ts... 

There are several characteristics of diastereomeric chiral separations (also known as indirect enantiomeric separations) that are worth mentioning. Achiral phases that are cheaper, more rugged, and widely commercially available are used. The elution order can be controlled by choice of the chirality of the derivatizing agent. This feature is useful for the analysis of trace levels of enantiomers. The separation can be designed such that the minor enantiomer is eluted first, allowing for more accurate quantitation. 

In a similar manner, the racemates shown in Fig. 5.4 could be transformed into the corresponding conglomerates very easily by salt formation with achiral derivatizing agents [6]. These results indicate that salt formation with an achiral derivatizing agent is very effective for the transformation of an acidic or basic racemate into a conglomerate. 

Figure 2.7. Achiral derivatizing agents for the determination of enantiomer ratio and partial resolutions [45-47].

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