A compound of formula (I) and salts and solvates thereof, in which: R0 represents
hydrogen,
halogen, or C1-6
alkyl; R1 represents
hydrogen, C1-6
alkyl, C2-6alkenyl, C2-6alkynyl, haloC1-6
alkyl, C3-8cycloalkyl, C3-8cycloalkylC1-3alkyl, arylC1-3alkyl, or heteroarylC1-3alkyl; R2 represents an optionally substituted monocyclic aromatic ring selected from
benzene,
thiophene,
furan, and
pyridine, or an optionally substituted bicyclic ring (a) attached to the rest of the molecule via one of the
benzene ring carbon atoms, and wherein the fused ring (A) is a 5- or 6-membered ring which may be saturated or partially or fully unsaturated, and comprises carbon atoms and optionally one or two heteroatoms selected from
oxygen, sulphur, and
nitrogen; and R3 represents
hydrogen or C1-3alkyl, or R1 and R3 together represent a 3- or 4-membered alkyl or alkenyl chain. A compound of formula (I) is a potent and selective inhibitor of cyclic
guanosine 3',5'-monophosphate specific
phosphodiesterase (cGMP specific PDE) having a utility in a variety of therapeutic areas where such inhibition is beneficial, including the treatment of cardiovascular disorders and
erectile dysfunction.