The N-alkylglycine trimeres (I), where R1, R2 and R3, independent of one another, are chosen from amongst cyclopropyl, sec-butyl, 2-metoxyethyl, 3-methylbutyl, cyclohexyl, 2-(N-pyrrolidinyl)ethyl, 2-(methylcarbonylamine)ethyl, 3-(2-oxo-N-pyrrolidinyl)propyl, 2-(2-pyridyl)ethyl, phenylethyl, 1-(2-tetrahydrofuryl)methyl, 2-(N-imidazolyl) ethyl, 2-(4-metoxyphenyl) ethyl, 2-(3,4-dimetoxyphenyl) ethyl, 2-(2,4-dichlorophenyl) ethtyl, 2-[2-(N-methyl) pyrrolidinyl] ethyl, 2-(4-aminosulfonylphenyl) ethyl, 2-(
morpholine) ethyl, 3-(N,N-
diethylamine) propyl, 3,3-diphenylpropyl, 3-(N,N-
dimethylamine) propyl, and 2-(N,N-
diethylamine) ethyl, their stereoisomeric forms and their mixtures, which are capable of blocking L-glutamate receptors and are useful for treating disorders mediated by said receptors.