Amino-acids and peptides. Part XXXVIII. Use of 4-picolyloxycarbonylhydrazides as ‘handles’ to facilitate peptide synthesis. Synthesis of fragments related to porcine gastric inhibitory polypeptide

Abstract

The use of the 4-picolyloxycarbonylhydrazide (4-pyridylmethoxycarbonylhydrazide) of the carboxy-terminal amino-acid provides both protection of the hydrazide group during peptide synthesis and a weakly basic ‘handle’ by which the product can readily be isolated after each coupling reaction. The procedure is illustrated by the synthesis of t-butoxycarbonyl-L-leucyl-L-alanylglycyl-L-valine hydrazide (5) and of the 4-picolyloxycarbonylhydrazides of a number of fragments related to the N-terminal sequence of porcine gastric inhibitory polypeptide. The 4-picolyloxycarbonyl group was removed by catalytic hydrogenolysis and by electrolytic reduction. The 4-picolyloxycarbonylhydrazides of eight-t-butoxycarbonylamino-acids are described.