3-(6,7-Dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-hydroxy-benzenesulfonyl Chloride; 5-(5-Chlorosulfonyl-2-hydroxyphenyl)-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one

Sildenafil derivative. Used in the preparation purinone derivatives for treatment of precancerous lesions and as cardiovascular agents.