Structure-activity relationships of tricyclic quinoxalinediones as potent antagonists for the glycine binding site of the NMDA receptor 1

All possible methyl substituted isomers of tricyclic quinoxalinediones 20a – 28a and 20b – 27b were synthesized and evaluated for their affinity for the glycine binding site of the NMDA receptor. Trans 6-methyl derivatives 26a and 26b showed comparable activity to the parent compounds 1a and 1b, respectively.