Syntheses are described of eleven protected peptide fragments which cover the entire sequence of porcine proinsulin and of two partially protected polypeptides which correspond to the 17–84 and 15–84 amino acid sequences, respectively, of porcine proinsulin.
The amino acid sequences of the two partially protected polypeptides are illustrated in the text. In these peptides, the sulfhydryl group of cysteine is protected with the ethylcarbamyl function, and the s-amino group of lysine is blocked with the formyl function. The partially protected octahexacontapeptide I cross-reacted with anti-synthetic porcine connecting peptide antisera to the same extent as did the porcine proinsulin or the synthetic connecting peptide. Heptacontapeptide II cross-reacted with antisera to porcine proinsulin and slightly with antisera to porcine insulin.