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

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.sup.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.sup.3 is alkyl of up to 6 carbon atoms or alkenyl of up to 6 carbon atoms;
• R.sup.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).sub.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.