2,3,5,6-Tetracarboxy-1,4-dihydropyridine derivatives

Claim 1

A compound of the formula: ##SPC52## or a pharmaceutically acceptable nontoxic salt thereof, wherein R is hydrogen, alkyl of up to 4 carbon atoms or alkenyl of up to 4 carbon atoms; R 2 is alkyl of up to 6 carbon atoms, alkenyl of up to 6 carbon atoms, said alkyl substituted by hydroxyl, said alkenyl substituted by hydroxyl, said alkyl interrupted by oxygen or said alkenyl interrupted by oxygen; R 3 is alkyl of up to 6 carbon atoms or alkenyl of up to 6 carbon atoms; R 5 is hydrogen or alkyl of 1 to 4 carbon atoms; n is 0, 1, 2 or 3; and X is phenyl; phenyl substituted by one or two nitro groups; one cyano group; one azido group; one or two trifluoromethyl groups; one S(O) n alkyl wherein n is 0 or 2 and alkyl is of 1 to 4 carbon atoms; one or two alkyl groups of 1 to 4 carbon atoms; one, two or three alkoxy groups of 1 to 4 carbon atoms; one or two acetoxy groups; one or two amino groups; one or two acetylamino groups; one or two alkylamino groups of 1 to 4 carbon atoms; one or two dialkylamino groups of 1 to 4 carbon atoms in each alkyl group; one to three chlorine, bromine or fluorine atoms, or by one phenyl moiety; naphthyl; benzyl; or phenethyl.