ABSTRACT
A microwave-assisted, one-pot, coupling reaction for the synthesis of C5-alkynyl-uracil and cytosine glucopyranonucleosides has been developed. The reaction is carried out under standard Sonogashira coupling conditions from glucopyranonucleosides of 5-iodouracil or 5-iodocytosine and various terminal alkynes. All compounds were evaluated for their cytostatic and antiviral activity. The 5-phenylethynyluracil pyranonucleoside derivative 6a showed the most promising cytostatic activity (50% inhibitory concentration in the lower micromolar range). No meaningful antiviral activity was recorded.
Subject(s)
Alkynes/chemical synthesis , Alkynes/pharmacology , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Pyrimidine Nucleosides/chemical synthesis , Pyrimidine Nucleosides/pharmacology , Alkynes/chemistry , Animals , Drug Screening Assays, Antitumor , Female , HeLa Cells , Humans , Leukemia L1210/drug therapy , Mice , Microwaves , Pyrimidine Nucleosides/chemistry , Uterine Cervical Neoplasms/drug therapyABSTRACT
Five ribofuranosyl pyrimidine nucleosides and their corresponding 1,2,3-triazole derivatives have been synthesized and characterized. Their inhibitory action to Ribonuclease A has been studied by biochemical analysis and X-ray crystallography. These compounds are potent competitive inhibitors of RNase A with low µM inhibition constant (K(i)) values with the ones having a triazolo linker being more potent than the ones without. The most potent of these is 1-[(ß-D-ribofuranosyl)-1,2,3-triazol-4-yl]uracil being with K(i) = 1.6 µM. The high resolution X-ray crystal structures of the RNase A in complex with three most potent inhibitors of these inhibitors have shown that they bind at the enzyme catalytic cleft with the pyrimidine nucleobase at the B(1) subsite while the triazole moiety binds at the main subsite P(1), where P-O5' bond cleavage occurs, and the ribose at the interface between subsites P(1) and P(0) exploiting interactions with residues from both subsites. The effect of a susbsituent group at the 5-pyrimidine position at the inhibitory potency has been also examined and results show that any addition at this position leads to a less efficient inhibitor. Comparative structural analysis of these RNase A complexes with other similar RNase A-ligand complexes reveals that the triazole moiety interactions with the protein form the structural basis of their increased potency. The insertion of a triazole linker between the pyrimidine base and the ribose forms the starting point for further improvement of these inhibitors in the quest for potent ribonucleolytic inhibitors with pharmaceutical potential.
