Syntheses are described of a series of peptides and peptide derivatives which correspond to the sequence of the seven N-terminal positions in the primary structure of bovine pancreatic ribonuclease A. The hydrazides of Na, N'-di-t-butylox y ca rb on y Ily sy 1-7-tb u ty lg lu t amy I-threonyla1anylaIanylalanyl-N'-t-butyloxy carbonyllysine, Nt-butyloxycarbonylthreon ylalan ylalan ylalan yl-N'-tbutyloxycarbonyllysine, and t-butyloxycarbonylalanylalanylalanyl-N'-t- ...