Excitatory amino acid receptor antagonists

A compound of the formula ##STR7## and the other of Y and Z is hydrogen;

• each R.sup.3 is independently C.sub.1 -C.sub.16 alkoxy, phenyl-substituted C.sub.1 -C.sub.4 alkoxy, benzyloxy substituted on the phenyl ring with halogen, C.sub.1 -C.sub.4 alkyl, or C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.5 alkanoyloxymethyl, or C.sub.1 -C.sub.5 alkanoyloxymethyl substituted on the oxymethyl with C.sub.1 -C.sub.4 alkyl or C.sub.4 -C.sub.7 cycloalkyl;
• each R.sup.4 is independently hydrogen, C.sub.1 -C.sub.16 alkyl, phenyl-substituted C.sub.1 -C.sub.4 alkyl, or phenyl;
• or
• a pharmaceutically acceptable salt thereof.