Synthesis and pharmacological evaluation of N,N-di-n-propyldopamine congeners containing phenolic bioisosteres.

A series of analogues of N,N-di-n-propyldopamine (DPDA) in which the 3-hydroxyl group was replaced by bioisosteric groups was prepared and evaluated for D1- and D2-receptor affinity. The 3-methane-sulfonamide analogue (18) had a higher affinity for the D2 receptor than DPDA and was more selective for the D2 receptor. The 3-formamide derivative (15) also retained significant D2 affinity. Both of these compounds demonstrated in vivo cardiovascular and renal profiles in an anesthetized rat model that were consistent with selective D2-receptor agonism.

Antihypertensive 1-acyl-4-[2-(1,4-benzodioxan-2-yl)-2-hydroxyethylamino]pip eridines.

Several 1-acyl-4-[2-(1,4-benzodioxan-2-yl)-2-hydroxy-ethylamino]piperidine s were prepared and a number of the compounds showed antihypertensive activity in the spontaneously hypertensive rat (SHR). This activity was specific for the (2S, 2R) enantiomers. General pharmacological evaluation and ligand binding data on selected compounds indicated a moderate degree of alpha 1- and beta-antagonistic activity. The alpha 1 antagonism was probably not of sufficient magnitude to explain the blood pressure lowering activity in the SHR.

Antihypertensive aminotetralins related to labetalol and medroxalol.

A series of compounds was prepared in which the 1-methyl-3-phenylpropylamino moieties of the antihypertensive agents labetalol and medroxalol were replaced by 2-aminotetralins. Compounds containing a 6-methoxy and 6,7-methylenedioxy group in the aminotetralin were at least as active as labetalol in lowering the blood pressure of the spontaneously hypertensive rat (SHR). As determined by ligand binding, these compounds were comparable to labetalol as alpha 1-antagonists but were substantially weaker beta 1-antagonists.

Synthesis and antihypertensive activity of a series of spiro[1,3,4,6,7,11b-hexahydro-2H-benzo[a]quinolizine-2,5'-oxazolidin-2'-one]s.

The 2R*,11bS* and 2S*,11bS* diastereoisomers of the spiro[1,3,4,6,7,11b-hexahydro-2H-benzo[a]quinolizine-2, 5'-oxazolidin-2'-one] system were prepared by stereoselective methods. Evaluation of these compounds for antihypertensive activity by oral administration to the spontaneously hypertensive rat showed the 2S*,11bS* series was the more potent. Within that series it was found that small alkyl substituents at positions 3 and 4' enhanced antihypertensive activity and that methoxyl substitution at positions 9 and 10 was optimal. (2S,3S,11bS)-Spiro-[2-ethyl-9,10-dimethoxy-1,3,4,6,7, 11b-hexahydro-2H-benzo[a]quinolizine-2,5'-oxazolidin-2'-one] [(-)-9e] was one of the most efficacious compounds of this series, while its antipode, (+)-9e, was inactive. Selected compounds in this series were shown to be alpha-adrenoceptor antagonists.

Antihypertensive 9-substituted 1-oxa-4,9-diazaspiro[5.5]undecan-3-ones.

Forty-one 9-substituted 1-oxa-4,9-diazaspiro[5.5]undecan-3-ones were prepared for antihypertensive screening in the spontaneously hypertensive rat (SHR). For the 9-(2-indol-3-ylethyl) series, the parent compound, 9-(2-indol-3-ylethyl)-1-oxa-4,9-diazaspiro[5.5]undecan-3-one (21), was the most potent antihypertensive agent. Substitution of lower alkyl groups on the spirolactam ring gave compounds close in activity to 21, while substitution with large alkyl or aryl groups led to a significant decrease in activity. Ring-opened analogues of 21 that contained the same functionality were markedly less active. Several 1-oxa-4,9-diazaspiro[5.5]undecan-3-ones substituted at the 9 position with 1,4-benzodioxan-2-ylmethyl, 1,4-benzodioxan-2-ylhydroxyethyl, and 2-phenylethyl groups also demonstrated significant activity. Compound 21 was chosen for a detailed pharmacological evaluation. Its antihypertensive activity appears to be predominantly due to peripheral alpha 1-adrenoceptor blockade.

Synthesis and antihypertensive activity of 4'-substituted spiro[4H-3,1-benzoxazine-4,4'-piperidin]-2(1H)-ones.

A series of 4'-substituted spiro[4H-3,1-benzoxazine-4,4'-piperidin]-2(1H)-ones was prepared and evaluated for antihypertensive activity in the spontaneously hypertensive rat (SHR). The basic ring system was prepared in one step by condensation of dilithiated (tert-butoxycarbonyl)aniline (3) with (tert-butoxycarbonyl)piperidinone. Deprotection afforded 6, which was condensed with expoxides or alkyl halides to furnish the title compounds. The most active compound was dl-erythro-4'-[2-(1,4-benzodioxan-2-yl)-2-hydroxyethyl]spiro [4H-3,1-benzoxazine-4,4'-piperidin]-2(1H)-one (9), and various modifications of this compound were made in order to elucidate the structure-activity relationships in the series. Preliminary indications are that 9 may act by both central and peripheral mechanisms.

Structure-activity relationships for 2-substituted imidazoles as alpha 2-adrenoceptor antagonists.

Several 2-[(1,4-benzodioxan-2-yl)alkyl]imidazoles were prepared and evaluated for their blocking activity and relative selectivity on presynaptic (alpha 2) and postsynaptic (alpha 1) receptors in the isolated rat vas deferens. 1-Ethyl-2-[(1,4-benzodioxan 2-yl)methyl]imidazole (13) was the most selective alpha 2-adrenoceptor antagonist of the series and was, for practical purposes, devoid of alpha 1-adrenoceptor antagonist activity. The lipophilicity of 13 (log D = 2.31) indicated that it would have an excellent chance to enter the central nervous system. Compound 13 was selected for clinical evaluation as an antidepressant agent.

Synthesis and antihypertensive activity of a series of 8-substituted 1-oxa-3,8-diazaspiro[4.5]decan-2-ones.

Forty-three new 1-oxa-3,8-diazaspiro[4,5]decan-2-ones optionally substituted with 2-(3-indolyl)ethyl, 3-(2-methoxyphenoxy)-2-hydroxypropyl, or 2-(1,4-benzodioxan 2-yl)-2-hydroxyethyl at the 8 position were prepared for screening as antihypertensive agents in the spontaneous hypertensive rat. For the 8-[2-(3-indolyl)ethyl] compounds the most active were those substituted in the 4 position, where activity was at maximum with the 4-ethyl compound (1). The 8-[3-(2-methoxyphenoxy)-2-hydroxypropyl] compounds were less active than their 1,4-benzodioxane counterparts, which were tested as mixtures of erythro and threo diastereoisomers. Both the 4-ethyl-8-[2-(1,4-benzodioxan-2-yl)-2-hydroxyethyl]-substituted 38 and (S)-3-methyl-8-[3-(2-methoxyphenoxy)-2-hydroxypropyl]-substituted 42 were designed as mixed alpha- and beta-adrenergic receptor blockers. Bother compounds lowered blood pressure, but they gave no evidence of working as beta-adrenergic blockers. Examination of 8-[2-(3-indolyl)ethyl]-1-oxa-3,8-diazaspiro[4.5]-decan-2-one (8) and 3 methyl-8-[2-(1,4-benzodioxan-2-yl)-2-hydroxyethyl]-1-oxa-3,8-diazaspiro[4,5]decan-2-one (29) in the dog showed them to be alpha-adrenergic blockers. Compound 29 was primarily an alpha 2-adrenoceptor antagonist, while 8 was more skewed toward alpha 1-adrenoceptor antagonism. Tilt-response studies for evaluating the potential for producing orthostatic hypotension showed that both 8 and 29 had little potential for avoiding orthostatic hypotension at therapeutically effective doses.

Synthesis and evaluation of ureido- and vinylureidopenicillins as inhibitors of intraruminal lactic acid production.

A series of 14 vinylureidopenicillins and a series of 9 ureidopenicillins were prepared by reaction of 6-aminopenicillanic acid with vinyl isocyanates and isocyanates. These compounds were evaluated for their potential to protect ruminants against lactic acidosis. The compounds were tested for inhibition of in vitro ruminal lactic and propionic acid production, and six compounds inhibited lactic acid production to less than 10% of control at doses of 0.31 microgram/mL or lower, whereas they did not inhibit propionic acid production at doses greater than 10 micrograms/mL. The most active compounds also were screened for general antibacterial activity and were found to be weakly active against Gram-positive bacteria. The structure--activity relationships are discussed for both series. Triethylammonium 6-[3[2-(4-tert-butylphenyl)vinyl]ureido]penicillanate (4) was chosen for evaluation as an inhibitor of intraruminal lactic acidosis in vivo.

Tricyclic aryl-substituted anticoccidial azauracils.

Syntheses of tricyclic aryl-substituted 6-azauracils are described. These compounds showed anticoccidial activity when tested against Eimeria tenella and E. necatrix. Compound activity was correlated with the chemical shift of the azauracil ring proton. No correlation existed between activity and compound lipophilicity. One of the compounds, 2-(11-oxo-6,11-dihydrodibenzo[b,e]thiepin-3yl)-as-triazine-3,5(2H,4H)-dione (23), was tested extensively against E. tenella and E. brunetti both in vivo and in vitro. Compound 23 controlled mortality due to E. tenella at 62 ppm, and it afforded protection as measured by weight gain at 31 ppm. Compound 23 afforded little protection against E. brunetti. In vitro experiments with 23 showed that it exerted a coccidiostatic effect.

Simultaneous peptide and oligonucleotide formation in mixtures of amino acid, nucleoside triphosphate, imidazole, and magnesium ion.

Simultaneous peptide and oligonucleotide formation was observed in reaction mixtures of amino acid, nucleoside triphosphate, imidazole, and MgCl2. At 70 degrees C in solutions that were evaporated to dryness the formation of peptide for phe and pro was greatest with CTP relative to ATP, GTP, and UTP. Lysine exhibited a preference for GTP and glycine for UTP. At ambient temperature insolution at pH 7.8, CTP was preferred by glycine, but at pH 8.7 UTP was preferred. The glycine nucleotide phosphoramidates were also detected and characterized in reactions at 40 degrees C. The glycine-reaction preference for CTP at pH 7.8 and UTP at 8.7 suggested that the basicity of the nucleoside triphosphate was involved in increasing the peptide yield. CTP near neutrality is the most basic nucleoside triphosphate and the basic anionic form UTP could facilitate peptide formation at pH 8.7. These data, together with information on the complexing of poly(C) by GTP, led to the experimentally approchable hypothesis that GTP, by forming a basic triplex between the cytosine residues adjacent to the peptidyl adenosine and aminoacyl adenosine at the termini of two proto-tRNAs, would promote peptide bond synthesis between the aminoacyl residue and peptidyl residue.