Synthesis and Biological Study of the Cyclopentenyl Carbocyclic Nucleoside Analogue of 5-Azacytidine

Abstract Cyclopentenyl cytosine (CPE-C, 3) possesses excellent antitumor and antiviral activity. The synthesis of the analogous cyclopentenyl triazine nucleoside, 5-aza-CPE-C (4), was accomplished by a novel approach that utilized a key 1-cyclopentenyl-4-methylisobiuret intermediate (7) produced from the corresponding cyclopentenylamine 5. 5-Aza-CPE-C was more than six-hundred times less potent than CPE-C both in its capacity to reduce CTP levels as well as in its antitumor and antiviral activity.