Synthesis and Antibacterial Activity of Novel Triazolo[4,3-a]pyrazine Derivatives

Infectious diseases pose a major challenge to human health, and there is an urgent need to develop new antimicrobial agents with excellent antibacterial activity. A series of novel triazolo[4,3-a]pyrazine derivatives were synthesized and their structures were characterized using various techniques, such as melting point,1H and13C nuclear magnetic resonance spectroscopy, mass spectrometry, and elemental analysis. All the synthesized compounds were evaluated for in vitro antibacterial activity using the microbroth dilution method. Among all the tested compounds, some showed moderate to good antibacterial activities against both Gram-positiveStaphylococcus aureusand Gram-negativeEscherichia colistrains. In particular, compound2eexhibited superior antibacterial activities (MICs: 32 μg/mL againstStaphylococcus aureusand 16 μg/mL againstEscherichia coli), which was comparable to the first-line antibacterial agent ampicillin. In addition, the structure–activity relationship of the triazolo[4,3-a]pyrazine derivatives was preliminarily investigated.Keywords:nitrogen-containing heterocycles;triazole compounds;triazolo[4,3-a]pyrazine derivatives;antibacterial activity