Defining the structural parameters that confer anticonvulsant activity by the site-by-site modification of (R)-N'-benzyl 2-amino-3-methylbutanamide

Primary amino acid derivatives (PAADs) (N'-benzyl 2-substituted 2-amino acetamides) are structurally related to functionalized amino acids (FAAs) (N'-benzyl 2-substituted 2-acetamido acetamides) but differ by the absence of the terminal N-acetyl group. Both classes exhibit potent anticonvulsant activities in the maximal electroshock seizure animal model, and the reported structure-activity relationships (SARs) of PAADs and FAAs differ in significant ways. Recently, we documented that PAAD efficacy was associated with a hydrocarbon moiety at the C(2)-carbon, while in the FAAs, a substituted heteroatom one atom removed from the C(2)-center was optimal. Previously in this issue, we showed that PAAD activity was dependent upon the electronic properties of the 4'-N'-benzylamide substituent, while FAA activity was insensitive to electronic changes at this site. In this study, we prepared analogues of (R)-N'-benzyl 2-amino-3-methylbutanamide to identify the structural components for maximal anticonvulsant activity. We demonstrated that the SAR of PAADs and FAAs diverged at the terminal amide site and that PAADs had considerably more structural latitude in the types of units that could be incorporated at this position, suggesting that these compounds function according to different mechanism(s).     

The significance of the imidazole ring in anticonvulsant activity of (arylalkyl)imidazoles

The imidazole ring in nafimidone [1-(2-naphthyl)-2-(1-imidazolyl)ethanone] was substituted with various groups to investigate the significance of the imidazole ring in anticonvulsant activity. For this purpose, some 2-acetylnaphthalene derivatives and their reduction products were synthesized. Several N-alkylation methods were used to prepare 2-acetylnaphthalenes. NaBH₄ was used to synthesize their reduction products. Anticonvulsant activities of these compounds were determined by phase I tests of Antiepileptic Drug Development Programme.     

Influence of structural changes in the imidazolidine ring of clonidine on hypotensive activity.

2-(2,6-Dichlorophenylimino)piperimidine with HNO3 (St-404), 2-(2,6-dichlorophenyl)-5,6-dihydroimidazo[2,1-b]thiazole fumarate (compound 44-549) and 1,2,3,5-tetrahydroimidazo[2,1-b]quinazoline with HCl (TIQ) were studied with respect to their effects on blood pressure and heart rate in the anaesthetized, normotensive rat following intravenous administration and in the chloralose-anaesthetized cat by means of infusions via the left vertebral artery. St-404 and compound 44-549 possess central hypotensive and bradycardic activities and display modes of action similar to that of clonidine. Central alpha-adrenergic receptors are presumably involved. In the anaesthetized, normotensive rat St-404 is about 3,400 times less active than clonidine, whereas compound 44-549 is 5 times more effective in lowering arterial pressure. The hypotensive effect of TIQ is brought about by a mechanism of action which is different from that of clonidine. The alpha-sympatholytic properties of TIQ suggested previously by others are not confirmed by the experiments presented in this paper.     

Influence of lithium on the anticonvulsant activity of carbamazepine

The present study was undertaken to see whether the recently reported synergism between lithium and carbamazepine (CBZ) in mania also extends against convulsions. The anti-convulsant effect of various doses of CBZ was assessed in albino rats pretreated with vehicle or lithium salt (0.54 mEg/kg/day, p.o. for 9 days). The animals were subjected to 3 tests: maximum electro shock seizures (MES); minimum electro convulsive thresholds (MET) and pentylenetetrazol (PTZ)-induced convulsions: abolition of hind limb extension after electro shock, increases in the MET for appearance of neck jerk and absence of convulsions for one hr after PTZ were taken as parameters of the anticonvulsive effect respectively. In the MES and MET tests lithum did not alter the anticonvulsive effect of CBZ. Lithium, however, potentiated the anticonvulsant effect of CBZ against PTZ-induced convulsions.     

Antimycobacterial activity of 5-arylidene derivatives of hydantoin

The synthesis of various 5-arylidene-2-thiohydantoins and results of the primary assay in vitro for their antimycobacterial activity is reported. Eight of those compounds exhibited >90% inhibition of Mycobacterium tuberculosis growth and for them the minimum inhibitory concentrations, cytotoxicity (IC₅₀) and the selectivity index values were determined. The most active structure, (5Z)-5-(1,1′-biphenyl-4-ylmethylene)-2-thioxoimidazolidin-4-one, showed MIC=0.78 μg/ml. For all compounds log P and log D (pH 6.5) values were calculated.     

Alpha-adrenoreceptor reagents. 2. Effects of modification of the 1,4-benzodioxan ring system on alpha-adrenoreceptor activity

Modification of the 1,4-benzodioxan ring present in RX 781094 has not previously been considered. This paper describes a number of analogues of this ring system, including compounds in which one of the oxygen atoms has been replaced by a methylene group and also those in which the ring size has been changed to give, for example, furan and thiophene derivatives. The dihydrobenzofuranylimidazoline compound 7 is the only analogue possessing presynaptic antagonist potency potency and selectivity comparable to that of 1. In view of this result, a number of derivatives was prepared to determine the structure-activity relationships within this series. Many derivatives, as well as the parent compound 7, were found to possess presynaptic alpha 2-adrenoreceptor antagonist and postsynaptic alpha 1-adrenoreceptor partial agonist properties. Two of the selective presynaptic antagonists, 13 and 14 possess greater potency and selectivity than that possessed by 1. The 5-chloro derivative 25 is twice as potent as after oral administration but only about half as potent when given intravenously.     

Antimycobacterial activity of 5-arylidene derivatives of hydantoin

The synthesis of various 5-arylidene-2-thiohydantoins and results of the primary assay in vitro for their antimycobacterial activity is reported. Eight of those compounds exhibited > 90% inhibition of Mycobacterium tuberculosis growth and for them the minimum inhibitory concentrations, cytotoxicity (IC50) and the selectivity index values were determined. The most active structure, (5Z)-5-(1,1'-biphenyl-4-ylmethylene)-2-thioxoimidazolidin-4-one, showed MIC = 0.78 microg/ml. For all compounds log P and log D (pH 6.5) values were calculated.