Studies on cerebral protective agents. VIII. Synthesis of 2-aminothiazoles and 2-thiazolecarboxamides with anti-anoxic activity.

Various 2-aminothiazoles (2a-s and 3a-g) and 2-thiazolecarboxamides (4a-h), possessing a nitrogenous basic moiety at the C-2 position of the thiazole ring, were prepared and tested for anti-anoxic (AA) activity in mice. Among them, N-[2-(4-morpholinyl)ethyl]-4-(3-trifluoromethylphenyl)-2- thiazolecarboxamide hydrochloride (4e, FR108143) (minimum effective doses of 3.2 mg/kg i.p. and 10 mg/kg p.o., respectively) exhibited more potent AA activity than either FK360 or compound 1, each of which has a nitrogenous basic moiety at the C-5 position. The structure-activity relationships with regard to AA activity of this series of compounds are discussed, and the three-dimensional electrostatic potentials (3D-MEP) around the basic nitrogen atom of FK360 and the thiazole derivative (4e) are compared.