1, 4-Pyrimido- (2a), 1, 4-diazepino- (2b), and 1, 4-diazocino[1, 2, 3-gh]purine (2c) were designed as selective cAMP-phosphodiesterase 4 (PDE 4) inhibitors. The desired condensed-purines(2b, c) were synthesized by reaction of 7-aminoalkyl-3-propylpurine-2, 4-diones (6b, c) with hexamethyldisilazane by intramolecular cyclization via silylation-amination.