Bismethylene Triphosphate Nucleotides of Uridine 4-Phosphate Analogues:  A New Class of Anionic Pyrimidine Nucleotide Analogues

Cytidine-5‘-triphosphate synthase (CTPS) catalyzes the formation of cytidine triphosphate (CTP) from glutamine, uridine 5‘-triphosphate (UTP), and adenosine 5‘-triphosphate (ATP). This reaction proceeds via formation of the high-energy intermediate UTP-4-phosphate (UTP-4-P). Stable analogues of UTP-4-P may be potent inhibitors of CTPS and useful as lead structures for the development of anticancer and antiviral agents. Several bismethylene triphosphate (BMT) nucleotides of uridine 4-phosphate (U-4-P) analogues have been prepared. A key step was the selective methanolysis, with the aid of a tin catalyst, of the 5‘ ester moiety of 2‘,3‘,5‘-tri-<i>O</i>-acetyl or tri-<i>O</i>-benzoyl U-4-P analogues. We believe this represents the first general approach to the selective cleavage of 5‘ benzoyl esters in benzoylated nucleosides. Mitsunobu coupling of these 5‘-deprotected U-4-P analogues to an unsymmetrical, protected BMT bearing a free phosphonic acid moiety at one of the terminal positions gave fully protected BMT-U-4-P analogues. Global deprotection of these species was achieved using TMSBr followed by treatment with NH<sub>4</sub>OH−MeOH or NH<sub>4</sub>OH−pyridine. The resulting BMT nucleotides represent a new class of anionic pyrimidine nucleotide analogues.