5-nitro-2--deoxyuridine and Leukemia-L1210

Both photochemical aromatic substitution and palladium (0)-catalyzed biaryl coupling reactions have been employed in the synthesis of 5-substituted 2'-deoxyuridines. The former procedure was useful in the preparation of the 3,4-dimethyl-2,5-dimethoxyphenyl derivative 12a and the 3,4,6-trimethyl-2,5-dimethoxyphenyl derivative 12b. The latter reaction was efficient in the preparation of the 2-(3-methyl-1,4-dimethoxynaphthyl) derivative 14. These compounds and their nucleotides (20a-c) were converted to the corresponding quinone nucleosides 19a-c and nucleotides 6-8 by an oxidative demethylation reaction using ceric ammonium nitrate and silver(II) oxide, respectively. The kinetics and products of the reaction of the quinone nucleosides 19a,b with methyl thioglycolate showed rapid addition to the quinone ring in the trisubstituted derivative 19a and somewhat slower redox reactions with the tetrasubstituted quinones 19b and 19c. All six nucleotides had high affinity for the title enzyme from Lactobacillus casei with Ki values ranging from 0.59 to 3.6 microM; the most effective compounds were the dimethyl quinone 6 and the naphthoquinone 8. Somewhat higher inhibitory constants were observed with the quinones against the L1210 enzyme. The dimethyl quinone nucleotide 6 showed time-dependent inactivation (kinact = 0.015 s-1) against the L. casei enzyme, a rate saturation effect, and substrate protection in accord with the kinetic expression for an active-site-directed alkylating agent. The apparent second-order rate of this reaction (2.5 X 10(4) M-1 s-1) is one-twentieth the rate (kcat.) of the normal enzymatic reaction leading to product. None of the compound exhibited sufficient activity in the antitumor cell or antiviral assays to warrant further study.

Topics: Animals; Antineoplastic Agents; Antiviral Agents; Cell Division; Cell Line; Cell Survival; Deoxyuracil Nucleotides; Humans; Indicators and Reagents; Kinetics; Lacticaseibacillus casei; Leukemia L1210; Mice; Simplexvirus; Structure-Activity Relationship; Thymidylate Synthase; Vaccinia virus; Vesicular stomatitis Indiana virus

Results are described that demonstrate that the mechanism of action of the potent cytotoxic agent 5-nitro-2'-deoxyuridine (NO2-dUrd) involves thymidine (dThd) kinase catalyzed formation of 5-nitro-2'-deoxyuridylate (NO2dUMP) and subsequent potent inhibition of thymidylate (dTMP) synthetase by this compound. The evidence for this is as follows: (a) cells lacking dThd kinase are not inhibited by high concentrations of NO2dUrd; (b) the drug has no effect on dThd or uridine (Urd) incorporation into nucleic acids but prevents incorporation of deoxyuridine (dUrd); (c) growth inhibition is reversed by dThd but not by dUrd; (d) NO2dUrd causes changes in deoxynucleoside triphosphate pool sizes which are characteristic of specific inhibition of dTMP synthetase; (e) cells treated with [3H]NO2dUrd possess macromolecular bound [3H]NO2dUMP, which has properties characteristic of the NO2dUMP-dTMP synthetase complex. Treatment of L1210 leukemic mice at 400 mg/kg daily for 6 days gave only a 33% increase in life span, probably because of its rapid degradation to the inactive nitrouracil.

Topics: Adenosine Triphosphate; Animals; Antineoplastic Agents; Cells, Cultured; Deoxyuridine; DNA; Female; Leukemia L1210; Mice; RNA; Time Factors