Polypeptides of formula (I):wherein R1 and R2 are substituents independently selected from substituted and un-substituted alkyl groups and substituted and un-substituted aryl groups, and n is an integer greater than or equal to 2. Synthesis methods are also provided that do not use amino acids as starting materials, but instead employ imines and carbon monoxide as monomers that undergo transition metal-catalyzed alternating copolymerization to directly provide polypeptides using an acylcobalt catalyst with the following structural formula:wherein R is selected from the group consisting of alkyl, phenyl, and substituted phenyl groups.
