The 2′-deoxy (2a) and 2′-ara-fluoro (3a) derivatives of zebularine 1-(β-D-ribofuranosyl)-dihydropyrimidin-2-one, 1a were phosphorylated in high yield to the 5′-nucleotides 2b and 3b, respectively, ...and characterized by HPLC, enzyme degradation,
1
H,
13
C and
31
P NMR, and high resolution mass spectral analysis. Their inhibitory activity against partially purified MOLT-4 deoxycytidylate deaminase (dCMPD) in the presence of the allosteric effector deoxycytidine triphosphate (dm) and Mg
+2
ion was examined. Compounds 2b and 3b inhibited dCMPD with K
i
values of 2.1 × 10
−8
M and 1.2 × 10
−8
M, respectively. The parent nucleotide, zebularine monophosphate 1b was ineffective at concentrations > 100 μmol. The effect of the nucleosides, 1a-3a, as well as tetrahydrouridine (THU) and 2′-deoxy THU (dTHU), on the cellular production of DNA precursors was examined in human MOLT-4 peripheral lymphoblasts. It was shown that 1a, 2a and 3a all elevated intracellular dCTP and TTp levels in whole cells with the most powerful effect elicited by 1a. The 2′-fluoro derivative 3a was chemically phosphorylated much more cleanly and higher yield than 2a, without the formation of diphosphorylated by-products. This compound was found to be infinitely less sensitive to acid-catalyzed degradation than 2a. Since the substitution of fluorine for hydrogen had a slight potentiating effect on the dCMPD inhibitory activity white stabilizing the compound toward acid-catalyzed and enzymatic depyrimidination, compound 3b emerges as a very attractive tool for the pharmacological modulation of pyrimidine deaminase activity.
