Synthesis and Antiviral Activities of New Pyrazolo[4,3‐c]quinolin‐3‐ones and Their Ribonucleoside Derivatives

Several new pyrazolo4,3‐c]quinolin‐3‐one ribonucleosides (5a–g) and their corresponding heterocycle moieties (3a–g) were synthesized and evaluated against vaccinia virus (VV) and herpes simplex virus type 1 (HSV‐1). The derivatives 3c and 3d showed modest inhibitory activity against vaccinia virus reaching 70% at a concentration of 100 µM. All heterocyclic compounds (3a–f) showed a modest inhibition against HSV‐1, reaching the maximal inhibitory effect around 20–30%. The antiviral effects of most of the pyrazolo4,3‐c]quinolin‐3‐one ribonucleosides (5a–f) on VV and HSV were not impressive.