A facile synthesis of peptide para -nitroanilides was developed using a novel urethane linked para -aminoanilide resin 3 and solid phase peptide synthesis. Conversion of the resulting peptide para -aminoanilides to the corresponding peptide para -nitroanilides was achieved by oxidation with sodium perborate. With the exception of sequences containing methionine, tryptophan and cysteine, all amino acid residues can be used. A representative synthesis of the tetrapeptide para -nitroanilide succinyl-Ala-Ala-Pro-Arg-PNA is described.