No abstract

Coupling of terminal alkynes with 5-iodo-l-methyluracil and 5-iodouracil nucleosides (protected as their p-toluyl esters) proceeded in high yields in the presence of bis(triphenylphosphine)palladium(II) chloride and copper® iodide in warm triethylamine. Several of the subsequently deprotected 5-alkynyl-2'-deoxyuridines, including the parent 5-ethynyl-2'-deoxyuridine, had antiviral activity, and their 5'-monophosphates inhibited thymidylate synthetase. Hydrogenation of the 5-alkynyl side chain can be controlled to give (Z)-5-alkenylor the saturated 5-alkyl-2,-deoxyuridines. This provides a stereocontrolled route to the known 5-ethyl-and 5-n-hexyl-2'-deoxyuridines as well as (£)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU). Hydration of the triple bond gave the corresponding uracil-5-alkanone products in favorable cases.

It has been found that 2'-deoxy-2'-methyleneuridine (MdUrd), 2'-deoxy-2'-methylenecytidine (MdCyd), and 2'-deoxy-2',2'-difluorocytidine (dFdCyd) 5'-diphosphates (MdUDP (1) MdCDP (2) and dFdCDP (3), respectively) function as irreversible inactivators of the Escherichia coli ribonucleoside diphosphate reductase (RDPR). 2 is a much more potent inhibitor than its uridine analogue 1. It is proposed that 2 undergoes abstraction of H3' to give an allylic radical that captures a hydrogen atom and decomposes to an active alkylating furanone species. RDPR also accepts 3 as an alternative substrate analogue and presumably executes an initial abstraction of H3' to initiate formation of a suicide species. Both 2 and 3 give inactivation results that differ from those of previously studied inhibitors. The potent anticancer activities of MdCyd and dFdCyd indicate a significant chemotherapeutic potential. The analogous RDPR of mammalian cells should be regarded as a likely target and/or activating enzyme for these novel mechanism-based inactivators.

No abstract

An extensive series of structural analogs of uridine that differed in substituents in the sugar and/or base moieties were subjected to inhibitor-sensitivity assays in a yeast expression system to define uridine structural determinants for inhibitors of human concentrative nucleoside transporters 1 and 3 (hCNT1 and hCNT3). The production of recombinant hCNT1 and hCNT3 in a nucleoside-transporter deficient strain of yeast was confirmed by immunoblotting, and uridine transport parameters (K m , V max ) were determined by defining the concentration dependence of initial rates of uptake of [ 3 H]uridine by intact yeast. The K i values of uridine analogs were obtained from inhibitory-effect curves and converted to binding energies.