Compounds of the formula I ##STR1## are disclosed. In this formula, R is a member selected from the group consisting of --CR.sub.1 R.sub.2 R.sub.3, hydroxy, an alkoxy group having 1 to 4 carbon atoms and --NR.sub.4 R.sub.5, in which at most one of R.sub.1, R.sub.2 and R.sub.3 is hydrogen and the remainder are each independently selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkynyl group having 2 to 4 carbon atoms, a cycloalkyl group having 3 to 7 carbon atoms, a cycloalkylalkyl having 4 to 9 carbon atoms and a 3 to 6 membered cyclic ether; R.sub.4 and R.sub.5 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms; R.sub.6 and R.sub.7 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms; and R.sub.8 is hydrogen, an alkyl group having 1 to 4 carbon atoms, hydroxy, an alkoxy group having 1 to 4 carbon atoms or halogen. Salts of these compounds are also disclosed. Also disclosed are pharmaceutical compositions of these compounds with a pharmaceutically acceptable carrier, the use of these materials as N-methyl-D-aspartate receptor antagonists, processes for preparing these compounds and salts, and methods to treat cerebral diseases by administering an effective amount of these compounds, salts or compositions.