Identification of the aspartimide structure in a previously-reported peptide.

Abstract

The octapeptide Leu-Ser-Arg-Leu-Phe-Asp-Asn-Ala (hGH 6-13) has been reported to show insulin-potentiating properties, and its synthesis by conventional solid-phase synthesis was previously described. It is now shown that peptide synthesized with diisopropylethylamine or N-methylmorpholine as neutralizing base in each cycle does have the above structure. When triethylamine was used as neutralizing base however, the Asp residue was converted to its imide, the presence of which has been demonstrated by means of infrared, 1H-NMR and fast-atom bombardment mass spectra, and by reactivity studies, electrophoresis at several pH values, and enzymic hydrolysis. Only the imide form of the peptide posse..