Riluzole series. Synthesis and in vivo "antiglutamate" activity of 6-substituted-2-benzothiazolamines and 3-substituted-2-imino-benzothiazolines.

Two series of analogues of riluzole, a blocker of excitatory amino acid mediated neurotransmission, have been synthesized: monosubstituted 2-benzothiazolamines and 3-substituted derivatives. Of all the compounds prepared in the first series, only 2-benzothiazolamines bearing alkyl, polyfluoroalkyl, or polyfluoroalkoxy substituents in the 6-position showed potent anticonvulsant activity against administration of glutamic acid in rats. The most active compounds displaying in vivo "antiglutamate" activity were the 6-OCF(3) (riluzole), 6-OCF(2)CF(3), 6-CF(3), and 6-CF(2)CF(3) substituted derivatives with ED(50) values between 2.5 and 3.2 mg/kg i.p. Among the second series of variously substituted benzothiazolines, compounds as active as riluzole or up to 3 times more potent were identified in two series: benzothiazolines bearing a beta-dialkylaminoethyl moiety and compounds with an alkylthioalkyl chain and their corresponding sulfoxides and sulfones. The most potent derivatives were 2-imino-3-(2-methylthio)- and 2-imino-3-(2-methylsulfinyl)-ethyl-6-trifluoromethoxybenzothiazolines (61 and 64, ED(50) = 1.0 and 1.1 mg/kg i.p., respectively). In addition, intraperitoneal administration of some of the best benzothiazolines protected mice from mortality produced by hypobaric hypoxia.

4-Amino-6-chloro-2-piperazinopyrimidines with selective affinity for alpha 2-adrenoceptors.

A series of 4-amino-6-chloro-2-piperazinopyrimidines were synthesized and evaluated for their ability to interact with alpha 1- and alpha 2-adrenoceptors in vitro in binding assays using [3H]WB-4101, [3H]clonidine, and [3H]idazoxan as radioligands. Some compounds were also tested as inhibitors of [3H]spiroperidol binding. Several members of this series showed high and selective affinity for alpha 2-adrenoceptors. The nature of the 4-amino substituent seems to be the most critical factor in determining the potency at these receptors.

2-Amino-6-chloro-4-(N-methylpiperazino)pyrimidines, inhibitors of spiroperidol binding.

A series of 30 6-chloro-2,4-diaminopyrimidines was synthesized and tested in vitro as inhibitors of [3H]spiroperidol binding. The affinity for the dopamine receptor was shown to be related to the 6-chloro-4-(N-methyl-piperazine)pyrimidine structure bearing a NH2 or NHR1 group as a substituent in position 2, provided that R1 was not an alpha branched alkyl group. The nature of the substituent in position 5 is also of importance for the affinity; 2-(benzylamino)-6-chloro-4-(N-methylpiperazino)-5-(methylthio)pyrimidine (22) is the most active member of the series. Molecular structures of three compounds were analyzed by X-ray diffraction and PCILO computation.

3-(4-Piperidinylalkyl)indoles, selective inhibitors of neuronal 5-hydroxytryptamine uptake.

A series of 3-(4-piperidinylalkyl)indoles was synthesized and tested as uptake inhibitors of biogenic amines. Some of these compounds are potent and very selective in blocking the 5-hydroxytryptamine (5-HT) uptake, as evidenced by biochemical data and behavioral tests. A discussion on structure-activity relationships is given. The most interesting member of the series, indalpine, 3-[2-(4-piperidinyl)ethyl]indole (1), was selected for clinical studies.