Structural characterization of dimethyldithiodenafil and dimethylthiocarbodenafil, analogs of sildenafil

Abstract Two analogs of sildenafil (compounds 1 and 2) were detected in three powder products acquired from online drug markets during an LC–UV–MS analysis of psychotropic drugs. Their structures were established by high-resolution mass spectrometry and NMR spectroscopy. Compound 1 was identified as 5-(5-(3,5-dimethylpiperazine-1-carbonothioyl)-2-ethoxyphenyl)-1-methyl-3-propyl-1H-pyrazolo[4,3 -d ]pyrimidine-7(6H)-thione and named dimethyldithiodenafil. Compound 2 was identified as 5-(5-(3,5-dimethylpiperazine-1-carbonothioyl)-2-ethoxyphenyl)-1-methyl-3-propyl-1H-pyrazolo[4,3 -d ]pyrimidin-7(6H)-one and named dimethylthiocarbodenafil. Compound 1 was subjected to the phosphodiesterase assay (IC 50  = 0.20 nM). The three powder products were found to contain 12–19 mg of dimethyldithiodenafil and 1.4–3.9 mg of dimethylthiocarbodenafil per tube.