Adaptability of nonnatural aromatic amino acids to the active center of the E. coli ribosomal A site

3'-N-Aminoacyl analogs of puromycin with nonnatural aromatic amino acids were synthesized and their inhibitory activity in E. coli in vitro protein synthesizing system was evaluated. The analogs with L-2-naphthylalanine, L-p-biphenylalanine, L-2-anthrylalanine and trans-L-p-phenylazophenylalanine were found to inhibit the protein synthesis with high efficiency. The inhibition suggests that these nonnatural amino acids are accepted by the active center of the E. coli ribosomal A site. A model for the adaptability of nonnatural aromatic amino acids to the active center is proposed.