for the following products
5-(2-Ethoxy-5-((4-methylpiperazin-1-yl)sulfonyl)phenyl)-3-isobutyl-1-methyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one | 5-[2-Ethoxy-5-[(4-methyl-4-oxido-1-piperazinyl)sulfonyl]phenyl]-1,6-dihydro-1-methyl-3-(2-methylpropyl)-7H-pyrazolo[4,3-d]pyrimidin-7-one and Sildenafil impurity A
