The invention thus relates to compounds of formula 1(see formula 1)in whichR1 is 1-4C-alkyl andR2 is 1-4C-alkyl,and R3 and R9 have prescribed meanings. The compounds according to theinventionhave useful pharmacological properties which make them industriallyutilizable. Asselective cyclic nucleotide phosphodiesterase (PDE) inhibitors (specificallyof type 4),they are suitable on the one hand as bronchial therapeutics (for the treatmentof airwayobstructions on account of their dilating action but also on account of theirrespiratoryrate- or respiratory drive-increasing action) and for the removal of erectiledysfunction onaccount of their vascular dilating action, but on the other hand especiallyfor thetreatment of disorders, in particular of an inflammatory nature, e.g. of theairways(asthma prophylaxis), of the skin, of the intestine, of the eyes, of the CNSand of thejoints, which are mediated by mediators such as histamine, PAF (platelet-activatingfactor), arachidonic acid derivatives such as leukotrienes and prostaglandins,cytokines,interleukins, chemokines, alpha-, beta- and gamma-interferon, tumor necrosisfactor(TNF) or oxygen free radicals and proteases. In this context, the compoundsaccordingto the invention are distinguished by a low toxicity, a good enteralabsorption (highbioavailability), a large therapeutic breadth and the absence of significantside effects.