Synthesis of acyclonucleoside hydroxamic acids as inhibitors of ribonucleotide reductase

N-Hydroxy-alpha-(2-hydroxyethoxy)-1(2H)-pyrimidineacetamides 1-3 were synthesized as potential antitumor agents whose mechanism of action would involve inhibition of ribonucleoside diphosphate reductase (RDPR, EC 1.17.4.1). Acyclonucleoside esters 6-8 were prepared by the stannic chloride catalyzed reaction of methyl chloro[2-(phenylmethoxy)ethoxy]acetate (5) with various silylated pyrimidines, generated in situ from the bases and bis(trimethylsilyl)acetamide. Catalytic didebenzylation of hydroxamate 11 gave 1, while 2 and 3 were synthesized by the reaction of lactones 14 and 22, respectively, with hydroxylamine. In vitro acyclonucleoside hydroxamic acids 1-3 were 3-10-fold less potent than hydroxyurea against calf thymus cytidine diphosphate reductase. 5-Fluorouracil derivative 2 is nearly equipotent with hydroxyurea in inhibiting the growth of HeLa cells, while 1 is a much weaker inhibitor and cytidine derivative 3 is devoid of activity at 200 micrograms/mL.