Thieno[2,3-d]pyrimidines and -[1,3]oxazines as Glutamate Antagonists and Investigations on the Inhibitory Potency Toward Human LeukocyteElastase. -Fused thiophene derivatives such as thienopyrimidines, thienooxazines, and thienothiazines with the common 5-methyl-6-phenyl substitution pattern are designed and synthesized as cyclic analogues of a particularly active antagonist at the GluR6 kainate receptor. Thienooxazinone (Ib) is identified as a potent inhibitor of this receptor subtype and characterized as a noncovalent inhibitor of human leukocyte elastase (IC50 = 8.8 μM). -(BRIEL, D.; RYBAK, A.; KRONBACH, C.; UNVERFERTH, K.; GONZALEZ TANARRO, C. M.; GUETSCHOW*, M.; J.