Concise synthesis and antibacterial evaluation of novel 3-(1,4-disubstituted-1,2,3-triazolyl)uridine nucleosides

We report herein a simple and efficient synthesis of a new series of antibacterial uridine nucleosides. The strategy involved a sequential silylation/N-glycosylation/N-propargylation procedure of uracil 1 for preparing the dipolarophile 5 in good yield. A series of novel uridine-[1,2,3]triazole nucleosides 6a-j were efficiently synthesized via the copper-catalyzed azide-alkyne cycloaddition (CuAAC) from dipolarophile 5 with different selected azides. The reactions were carried out under both conventional and ultrasonic irradiation conditions. In general, improvements were observed when reactions were carried out under sonication. Their antibacterial potential has been evaluated by means of a micro-dilution assay against either Gram-positive or Gram-negative bacteria. Compounds 6i and 6j have shown significant bactericidal activity against Staphylococcus aureus (MIC = 10 and 6 μM, respectively), and 6h against Escherichia coli (MIC = 8 μM). Moreover, antibacterial kinetic assays showed that 6i and 6j significantly reduced the S. aureus growth rate at the MIC concentration, after 6 h, compared to their deprotected analogs, 6k and 6l, respectively. Compound 6h also significantly reduced the growth of E. coli. These antibacterial effects may be related to the penetrating properties of these compounds, as revealed by the leakage of nucleic acids from the sensitive strains.