Sildanafil 2nd stage impurity

Sildenafil, Sildanafil 2nd stage impurity, Sildanafil 2nd stage imp, Sildanafil 2nd stage, (1-{[3-(6,7-Dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl0sulfonyl]4-methylpiperizine), Sildanafil-2nd-stage-impurity, Sildanafil-2nd-stage-imp, Sildanafil-2nd-stage