title: Antagonist, partial agonist, and full agonist imidazo[1,5-a]quinoxaline amides and carbamates acting through the GABAA/benzodiazepine receptor.
abstract: (4RS)-1-(5-Cyclopropyl-1,2,4-oxadiazol-3-yl)-12,12a-dihyd roimidazo[1,5- a]pyrrolo[2,1-c]quinoxalin-10(11H)-one (1a), 5-benzoyl-3-(5-cyclopropyl-1,2,4-oxadiazol-3-yl)-4,5- dihydroimidazo[1,5-a]quinoxaline (13b), and tert-butyl (4S)-12,12a-dihydroimidazo[1,5-a]pyrrolo[2,1- c]quinoxaline-1-carboxylate (1e), as well as other imidazo[1,5-a]quinoxaline amides and carbamates, represent a new series of compounds which bind with high affinity to the GABAA/benzodiazepine receptor. These compounds exhibit a wide range of intrinsic efficacies as measured by [35S]TBPS binding ratios. The synthesis of 1a begins with the addition of DL-glutamic acid to 1-fluoro-2-nitrobenzene, followed by reduction of the nitro group and subsequent ring closure to form 3-(carbethoxymethyl)-1,2,3,4-tetrahydroquinoxalin-2-one, followed by a second ring closure to afford (4RS)-1,5-dioxo-1,2,3,4,5,6-hexahydropyrrolo[1,2-a]quinoxali ne as the key intermediate. Appendage of a substituted imidazo ring via the anion of 5-cyclopropyl-1,2,4-oxadiazol-3-yl gives 1a. The (-)- and (+)-isomers of 1a were prepared from 1-fluoro-2-nitrobenzene and L- and D-glutamic acid, respectively. 1a and its enantiomers demonstrated affinity for the [3H]flunitrazepam binding site with Ki's of 0.87, 0.62, and 0.65 nM, respectively.
authors.affiliation: Department of Medicinal Chemistry, Upjohn Laboratories, Upjohn Company, Kalamazoo, Michigan 49001.
authors.forename: R E
authors.initials: RE
authors.lastname: TenBrink
authors.forename: W B
authors.initials: WB
authors.lastname: Im
authors.forename: V H
authors.initials: VH
authors.lastname: Sethy
authors.forename: A H
authors.initials: AH
authors.lastname: Tang
authors.forename: D B
authors.initials: DB
authors.lastname: Carter
mesh_terms: D000818:Animals; D002219:Carbamates / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D018756:GABA Antagonists; D007093:Imidazoles / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D011810:Quinoxalines / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D018079:Receptors, GABA / Q000378:metabolism*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D002219:Carbamates; D018756:GABA Antagonists; D007093:Imidazoles; D011810:Quinoxalines; D018079:Receptors, GABA