Haloketone derivatives of amino acids

The striking successes achieved by Shaw (1970a) and his coworkers with haloketone derivatives of N-tosyl-phenylalanine and a-N-tosyl-lysine as affinity labels for chymotrypsin and trypsin, respectively, have stimulated their use in a large number of affinity labels. Haloketones are potentially reactive with all the nucleophilic amino acid residues in proteins. Examples of residues modified by haloketones include methionine (Sigman et al. 1970), glutamate (Visser et al. 1971), cysteine (Porter et al. 1971), histidine (Schoellman and Shaw 1963) and serine (Schroeder and Shaw 1971). 

T wo synthetic approaches for the preparation of haloketones include halogenation and the acidification of the corresponding diazoketone with the appropriate halo acid. Direct halogenation is most appropriately performed only with bromine. 

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