New polymer syntheses. IV. Polypeptides of lysine and ornithine with pending pyrimidine bases

Starting with β‐methoxy methacryloylisocyanate, β‐methoxy methacrylisothiocyanate, and β‐isocyanatopropionyl chloride, on the one hand, and Nα‐Z‐lysine or Nα‐Z‐ornithine, on the other hand, Nα‐Z‐amino acids with pyrimidine bases in the side chain were synthesized. These Z‐protected nucleoamino acids were converted to the corresponding N‐carboxyanhydrides (NCAs) via the silylester method. In the case of 2‐thiothymine derivatives, the reaction intermediate of the NCA synthesis caused benzylation of the thioxo‐ group, so that a new class of 2‐mercaptopyrimidine derivatives was isolated unexpectedly. The poly(nucleoamino acids) obtained by polymerization of the nucleoamino acid NCAs were characterized by elemental analyses, optical rotations 1H‐nmr and 13C‐nmr spectra. Vapor pressure osmometry revealed that the DPs were in the range of 20–30. Their spectra suggest a helical secondary structure. While all homopolypeptides are insoluble in water, copolypeptides containing L‐lysine Nε‐hydrobromide possess good solubility in water.