Antiviral activity of substituted 6-methylmercaptopyrazolo(3,4-d)pyrimidines and their ribosides.

The antiviral activities of pyrazolo(3,4-d)pyrimidines and their nucleosides, divided into 7 groups based on the substituent in position 4 (mercapto-, methylmercapto-, amino-, hydrazine-, dialkyl amino-, oxy-, and methoxyderivatives), were studied against herpes simplex virus type 1 (HSV 1) and vaccinia virus. Numerous compounds inhibited the virus yields by 1-4 log CPD50. Most antiviral compounds inhibited HSV 1 more than vaccinia virus. Only methylmercapto- derivatives inhibited both viruses approximately to the same degree.