Synthesis, glycine NMDA and AMPA binding activity of some new 2,5,6-trioxopyrazino[1,2,3-de]quinoxalines and of their restricted analogs 2,5-dioxo- and 4,5-dioxoimidazo[1,5,4-de] quinoxalines

The synthesis of some new 1,2,3,5,6,7-hexahydro-2,5,6-trioxopyrazino[1,2,3- de]quinoxalines 1c-g and of their restricted analogs 2,4,5,6-tetrahydro-2,5 -dioxo-1H-2a-g and 5,6-dihydro-4,5-dioxo-4H-imidazo[1,5,4-de]quinoxaline 3a -d is reported. Compounds 1c-g, 2a-g, and 3a-d were tested for their bindin g activity at the glycine/NMDA and AMPA receptors. The results thar only th e 6,6,6-tricyclic derivatives 1c-g are able to bind glycine/NMDA and AMPA r eceptors, although with lower affinity than the previously reported lead co mpounds 1a-b. In contrasts, the 5,6,6-tricyclic derivatives 2a-g are inacti ve at both receptors and only one 4,5-dioxoimidazoquinoxaline (3b) displays a weak glycine/NMDA receptor affinity.