Optically Active Acylation Reagents

A variety of carbonyl chlorides have been used to generate optically active dipeptides. N-TFA-l( — )-prolyl chloride was first used in 1965 by Halpern and Westley who separated the isomers of alanine, leucine, methionine, phenylalanine, proline and va-line. The reagent was chosen because it was thought that the cyclic nature of the derivative would preclude recemization via an oxazolinone mechanism. This reasoning was later shown by Bonner to be incorrect but the problem was overcome by modifying the derivatization procedure. The reagent subsequently came into fairly common use. It was extensively studied by Iwase and Murai who combined TFA, PFP and HFB forms with methyl, «-propyl, «-butyl, tert-butyl and cyclopentyl esters. By assessing the resolution of alanine, valine, leucine and isoleucine, they concluded that the esters of «-alkyl alcohols gave better resolution than branched or cyclic chain alcohols.

Konig introduced a second asymmetric centre into amino acid methyl esters using the chiral reagent l-a-chloroisovaleryl chloride. Formation of the 3-methyl-2-butyl esters enabled resolution of all the proteic amino acid diastereomers, including arginine, on an SE-30 capillary column in less than 1 h. A separate analysis was required for the basic amino acids. Nevertheless, the diastereomer approach was to be overtaken by the more direct and absolute method of enantiomer resolution on chiral phases.

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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