The chemistry of peptides related to metabolites of Trichoderma spp. 2. An improved method of characterization of peptides of 2-methylalanine

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Abstract
4-Chlorobenzoylazide reacts with amino acid and peptide esters to give the 4-chlorobenzoyl derivatives in 60-90% yield, at room temperature, without measurable racemization. The reaction also proceeds smoothly with hindered amines such as methyl 2-methylalaninate and with secondary amines, e.g. methyl-L-prolyl-L-valinate. Ten examples of the reaction are reported with peptides, synthesized for the purpose, that might be accessible from hydrolysates of the numerous fungal metabolites now known, which contain a high proportion of 2-methylalanine. The derivatives of di-, tri-, tetra-, and pentapeptides were highly crystalline, with sharp melting points, and could be detected and integrated in the effluent from chromatography columns at about the 10-ng level. This simple method of derivatization might be usefully applied to the resolution of discrepancies in the physical properties of ostensibly the same 2-methylalanyl peptide prepared in different laboratories.