Peptides Lossen reaction

The Lossen reaction of peptide carboxylic acids has teen investigated in order to determine the carboxy terminal amino acid residue of peptides." The procedure first involves the formation of 0-pivaloylhydroxamic acids (187) by condensation of peptide carboxylic acids (184) with O-pivaloylhy-droxylamine (185) using a water soluble carbodimide, l-ethyl-3-(3-dimethylaminopropyl)carbodiimide (186). The Lossen rearrangement of (187) occurs at pH 8.S and SO °C to give a mixture of isocyanates (188) and their reaction products, which, on acidic hydrolysis, afford the aldehydes (189), ammonia and amino acids, as shown in Scheme 30." Identification of aldehydes determines the C-terminal amino acids of the original peptides. 

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