PYRIDO[2, 3-D] PYRIMIDINE DERIVATIVES AND MEDICINAL COMPOSITIONS THEREOF

摘要

Compounds represented by general formula (I) or pharmaceutically acceptable salts thereof which have the effect of inhibiting the activity of type IV phosphodiesterases and are usable as drugs, in particular, type IV phosphodiesterase inhibitors or preventives and remedies for diseases in association with the sthenic type IV phosphodiesterase activity, in particular, respiratory diseases such as bronchial asthma. In said formula (I), X represents oxygen or sulfur; R1 represents lower alkyl, cycloalkyl(lower alkyl) or cycloalkyl; R2 represents hydrogen, halogeno, lower alkyl, halo(lower alkyl), hydroxy(lower alkyl), mercapto(lower alkyl), (lower alkoxy)(lower alkyl), (lower alkylthio)(lower alkyl), (lower alkanoyloxy)(lower alkyl), (lower alkanoylthio)(lower alkyl), (lower alkanoyl)(lower alkyl), hydroxyimino(lower alkyl), (lower alkoxyimino)(lower alkyl), cycloalkyl, aryl or lower alkanoyl; R3 represents hydrogen, halogeno or lower alkyl; R4 represents hydrogen, or lower alkyl; R5 represents cycloalkyl optionally substituted by the same group as R6; naphthyl optionally substituted by the same group as R6; a 5- or 6-membered monocyclic heterocycle optionally substituted by the same group as R6, optionally fused with a benzene ring and having one to four heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur atoms; or a group of formula (a); and R6 represents halogeno, lower alkyl, halo(lower alkyl), hydroxy, lower alkoxy, cyano or nitro.