Optically Active Esterification Reagents

Initial studies focused on forming active esters of N(O)-acyl amino acids and these were subsequently to be the most widely used derivatives. In 1965, Gil-Av reported the first resolution of amino acid diastereomers by GC (Figure 4). The 2-butyl and 2-octyl amino acid esters of alanine, glutamic acid, leucine, phenylalanine, proline and valine were resolved on capillary columns coated with either poly(trifluoropropylmethylsiloxane) or polypropylene glycol) operated isothermally at 140 or 180°C. In the same year, Pollock reported the resolution of the N-TFA 2-butyl esters of 13 amino acids but those of aspartic acid, serine and threonine were only partially resolved. A study by Westley (1968) concluded that the resolution was directly proportional to the size of the groups attached to the alcoholic asymmetric carbon and to the proximity of the branching to the asymmetric centre. Thus 3,3-dimethyl-2-butanol gave superior resolution. In 1968, Pollock extended his study to the resolution of all the proteic amino acids except arginine, histidine and cystine. Three years later, 37 amino acid diastereomers were resolved as the N-TFA 2-butyl esters.

In 1977, Konig separated the N-pentafluoro-propionyl (PFP) ( + )-3-methyl-2-butyl esters of all the

Figure 4 Resolution of diastereomers of A/-trifluoroacetyl amino acid (A/-TFA) 2-octyl esters. (Reproduced with permission from Gil-Av E, Charles R and Fischer G (1965) Resolution of amino acids by gas chromatography. Journal of Chromatography 17: 408-410.)

common proteic amino acids, including arginine, his-tidine and tryptophan. Excellent resolution was obtained using a 25 m column coated with SE30 and temperature programming from 85 to 220°C at 2°C min-1.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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