Human proinsulin, VII: synthesis of two protected peptides corresponding to the sequences 1--45 and 46--96 of the prohormone.

The synthesis of two protected large peptides 1--45, and 46--86 covering the entire amino acid sequence of human proinsulin is described. Peptide 1--45, was synthesized from two intermediate fragments 1--23 and 24--45 and purified by countercurrent distribution in dimethylformamide system (K = 0.5). Peptide 46--86 was synthesized from two intermediate fragments 46--70 and 71--86 and purified by countercurrent distribution in two solvent systems, the dimethylformamide system (K = 0.06), and the toluene system (K = 0.16).