Pyrido[2,3-D]pyrimidine derivatives and pharmaceutical compositions thereof

PCT No. PCT/JP96/03389 Sec. 371 Date Apr. 30, 1998 Sec. 102(e) Date Apr. 30, 1998 PCT Filed Nov. 20, 1996 PCT Pub. No. WO97/19078 PCT Pub. Date May 29, 1997This invention relates to compounds (I) or pharmaceutically acceptable salts thereof, having a function to inhibit type IV phosphodiesterase (PDE) [X: an oxygen atom or a sulfur atom, R1: a lower alkyl group, a cycloalkyl-lower alkyl group or a cycloalkyl group, R2: a hydrogen atom, a halogen atom, a lower alkyl group, a halogeno-lower alkyl group, a hydroxy-lower alkyl group, a mercapto-lower alkyl group, a lower alkoxy-lower alkyl group, a lower alkylthio-lower alkyl group, a lower alkanoyloxy-lower alkyl group, a lower alkanoylthio-lower alkyl group, a lower alkanoyl-lower alkyl group, a hydroxyimino-lower alkyl group, a lower alkoxyimino-lower alkyl group, a cycloalkyl group, an aryl group or a lower alkanoyl group, R3: a hydrogen atom, a halogen atom or a lower alkyl group, R4: a hydrogen atom or a lower alkyl group, R5: a cycloalkyl group; a naphthyl group substituted; a five- or six-membered monocyclic hetero ring group having 1 to 4 hetero atoms selected from nitrogen atom, oxygen atom and sulfur atom; or a group represented by the formula amd F6: a halogen atom, a lower alkyl group, a halogeno-lower alkyl group, a hydroxyl group, a lower alkoxy group, a cyano group or a nitro group].