The invention provides novel 7,8-dihydro-imidazo[l,2-a]pyrazolo[4,3-e]pyrimidin-4-one compounds and 7,8,9-trihydro-[lH or 2H]- pyrimido [l,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-one compounds, substituted at the 1 or 2 position with C2-9 alkyl, 03.9 cycloalkyl, heteroarylalkyl, or substituted arylalkyl, in free, salt or prodrug form, processes for their production, their use as Pharmaceuticals, particularly as PDE1 inhibitors, and pharmaceutical compositions comprising them.
