Puromycin analogs. Ribosomal binding and peptidyl transferase substrate activity of a carbocyclic analog of 8-azapuromycin

The synthesis of an 8-aza carbocyclic puromycin analog, 7-dimethylamino-3-{(R)-[(2R)-hydroxy-(3R)-(p-methoxyphenyl-l-alanylamino)]cyclopentyl}-v-triazolo[4, 5-d]pyrimidine (1), is described. The previously described carbocyclic pyrimidine, 2α-acetamido-5β-(5-amino-6-chloro-4-pyrimidinylamino)cyclopentan-1α-ol (2), was diazotized and converted to the corresponding 8-azapurine (4). Treatment of 4 with aqueous dimethylamine followed by acid hydrolysis of the acetamido blocking group gave the amino nucleoside analog (6). Coupling of 6 with N-benzyloxycarbonyl-p-methoxyphenyl-l-alanine, followed by hydrogenolysis of the Cbz blocking group, gave a mixture of 1 and its diastereoisomer, 7-dimethylamino-3-{(S)-[(2S)-hydroxy-(3S)-(p-methoxyphenyl-l-alanylamino)] cyclopentyl}-v-triazolo[4, 5-d]pyrimidine (2). The diastereomers were separated by chromatography. Biological testing with Escherichia coli ribosomes provides a comparison of the relative ribosomal binding affinities and peptidyl transferase substrate activities of puromycin and 8-aza carbocyclic puromycin. Kinetic data indicate that such compounds are capable of binding to the ribosomal acceptor site and act as peptidyl transferase substrates in a manner identical with the mechanism of action of puromycin.