Two approaches leading to the enantiomerically pure tricyclic quinoxalinedione class of NMDA-glycine antagonists using enzymatic resolutions are described. An intermediate, racemic methyl 1, 2, 3, 4-tetrahydroquinoline-2-carboxylate 3, was resolved to (S)-3 in 97% ee and 47% yield (E= 67) using α-chymotrypsin. In an improved method, hydrolysis of another intermediate, racemic methyl 1, 2, 3, 4-tetrahydroquinoline-2-acetate 4, with ...