Mono- and diaryl-2-quinuclidinylcarbinols with local anesthetic and antiarrhythmic activity.

The reaction between 2-carboethoxyquinuclidine and various aryl- and heteroarylithium reagents gave mixtures of aryl 2-quinuclidinyl ketones and diaryl-2-quinuclidinylcarbinols. Diborane reduction of the ketones gave the erythro-carbinols, stereochemically analogous to quinidine. Several of the mono- and diarylcarbinols exhibited potent local anesthetic and antiarrhythmic activity, in some cases greater than that of quinidine. Diphenyl-2-quinuclidinylcarbinol and a (bromomethoxyphenyl)(methoxyphenyl)-2-quinuclidinylcarbinol were particularly active in reverting ouabain-induced arrhythmia in dogs, showing a potency and duration of action equal to or greater than that of propranolol.

Inhibitors of cyclic AMP phosphodiesterase. 3. Synthesis and biological evaluation of pyrido and imidazolyl analogues of 1,2,3,5-tetrahydro-2-oxoimidazo[2,1-b]quinazoline.

Hybridization of structural elements of 1,2,3,5-tetrahydro-2-oxoimidazo[2,1-b]quinazoline ring system common to the cyclic AMP (cAMP) phosphodiesterase (PDE) inhibitors lixazinone (RS-82856, 1) and anagrelide (3) with complementary features of other PDE inhibitor cardiotonic agents prompted the design and synthesis of the title compounds 7a-d, 11, 12, and 13a,b. The necessary features of these compounds were determined within the framework of the proposed active-site models for the high affinity form of cAMP PDE inhibited by cGMP (type IV). Evaluation of these targets, both in vitro as inhibitors of platelet or cardiac type IV PDE or in vivo as inotropic agents in the pentobarbital-anesthetized dog model of congestive heart failure, showed that these structure possessed negligibly enhanced activities over the parent heterocyclic system, and remained significantly inferior to 1 in all respects. This difference is ascribed to the absence of the N-cyclohexyl-N-methylbutyramidyl-4-oxy side chain of 1. The proposal that the acidic lactam-type functionality, common to the type IV PDE inhibitor inotropic agents such as 4-6 and 8-10, mimics the polarizable cyclic phosphate moiety of cAMP suggested that the side chain of 1 may function as an effective surrogate for selected characteristics of the adenine portion of cAMP. However, the results of this study show that incorporation of adenine-like hydrogen-bonding functionalities common to other type IV PDE inhibitors into the 1,2,3,5-tetrahydro-2-oxoimidazo[2,1-b]quinazoline system did not enhance activity to the levels observed for 1 and analogues. These observations, coupled with the kinetic pattern of inhibition of type IV PDE observed for 1 and analogues, suggest that access to a secondary, lipophilic-tolerant binding site, possibly coincident with the adenine binding domain, and adjacent to the catalytic ribose-phosphate binding site of platelet and cardiac type IV PDE, is responsible for the increased potency of these compounds.

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.

Digitoxigenin 3-O-beta-D-furanosides.

The syntheses of the title compounds were accomplished by Koenig-Knorr condensation of acylated furanoses with digitoxigenin followed by basic hydrolysis of protecting groups. In this manner the riboside, 5-amino-5-deoxyriboside, 3,6-anhydroglucoside, and 3,6-dideoxy-3,6-iminoglucoside of digitoxigenin were prepared. These compounds as well as several of the synthetic intermediates showed weak to moderate cardiotonic activity.

Inhibitors of cyclic AMP phosphodiesterase. 4. Synthesis and evaluation of potential prodrugs of lixazinone (N-cyclohexyl-N-methyl-4-[(1,2,3,5-tetrahydro-2- oxoimidazo[2,1-b]quinazolin-7-yl)-oxy]butyramide, RS-82856).

The cyclic AMP phosphodiesterase (cAMP PDE) inhibitor and cardiotonic agent lixazinone (N-cyclohexyl-N-methyl-4-[(1,2,3,5-tetrahydro-2- oxoimidazo[2,1-b]quinazolin-7-yl)oxy]butyramide, RS-82856, 1) and its acid and base addition salts were found to be insufficiently soluble in formulations suitable for intravenous administration. These results prompted an investigation into potential prodrugs with enhanced aqueous solubility designed to deliver 1 by three distinct mechanisms: (1) decarboxylation of alpha-carboxamides; (2) hydrolytic loss of a solubilizing N-1-(acyloxy)methyl or (N,N-dialkylamino)methyl moiety; or (3) intramolecular closure of a guanidino ester or amide. The target compounds were evaluated as delivery systems for 1 by three criteria: (1) chemical conversion rate to 1 under physiological conditions; (2) inhibition of type IV cAMP PDE at a fixed time point; and (3) in vivo inotropic activity in anesthetized dogs by both intravenous and oral administration. Release of 1 from 4a (series 1) was found to be too slow to be of value as a prodrug of 1, since decarboxylation could be induced only by strong acid, conditions under which hydrolytic ring opening was found to severely compete. Conversely, 1 was released too readily on exposure of (N,N-dialkylamino)methyl derivatives such as 8d (series 2) to physiological conditions, although no large increase in aqueous solubility was realized. Finally, both the physicochemical and in vitro studies indicated that ring closure of the guanidinium esters and amides 17a-k (series 3) to 1 was quantitative and pH- and time-dependent, suggesting the possibility of delivery of the open, water-soluble prodrug form, followed by closure to 1 in plasma. Detailed examination of these agents in vivo, however, demonstrated that only those compounds that rapidly cyclized to 1, as measured by plasma levels of 1, exhibited inotropic activity, indicating that the open prodrug form was not efficiently absorbed upon oral administration.

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.

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.

Therapeutic and systemic side effects of ocular beta-adrenergic antagonists in anesthetized dogs.

Beta adrenergic antagonists, while useful in the treatment of glaucoma, can be absorbed transocularly causing a variety of systemic side effects. An adequate animal model which simultaneously indicates the intraocular pressure lowering effects as well as the systemic effects of ocularly applied beta-adrenergic antagonists would be highly useful. The pentobarbital anesthetized dog, instrumented to record blood pressure (BP) and heart rate (HR) and in which intraocular pressure (IOP) was measured with a pneumatonometer, was investigated. Isoproterenol iv dose-response curves were run and IOP measured before and hourly for 3 hr following ocular application of 50 microliters 0.5% RS-52367 (a Syntex beta-adrenergic antagonist), or dH2O control. Timolol and RS-52367 produced similar decreases in IOP. However, timolol decreased basal BP and HR, markedly inhibited isoproterenol-induced BP and HR responses, and also decreased contralateral IOP. Systemic effects of RS-52367 were far more mild. Since both the IOP lowering and systemic beta-adrenergic antagonist properties of timolol were elicited, the anesthetized dog appears to be an excellent animal model for examining the effects of beta-adrenergic antagonists applied topically to the eye.

Circulatory effects of tazolol in experimental myocardial infarction.

The hemodynamic effects of tazolol, a new long-acting beta-stimulating drug, were studied in dogs with acute pump failure caused by experimental myocardial infarction and the results were compared with the actions of isoproterenol given in small and large doses. Tazolol produced a significant and sustained increase in cardiac output and stroke volume, while causing a decrease in peripheral resistance and mean aortic pressure. Heart rate was only modestly increased. Compared with isoproterenol at equivalent doses. tazolol appeared to cause less S-T segment elevation at the margin of infarction. The increase in double product (systolic pressure X heart rate) produced by tazolol was also considerably less than that of isoproterenol. Tazolol may prove to be a useful addition to the drugs available for the treatment of myocardial failure of various causes. It is now being studied in patients with heart failure due to coronary artery disease.

Synthesis and bronchodilator activity of endo-2-(2-cyclopentyl-2-hydroxy-2-phenyl)acetoxy-7-methyl-7- azabicyclo-[2.2.1]heptane methobromide, a potent and long-acting anticholinergic agent.

The synthesis of the alpha-cyclopentylmandelate ester of quaternized endo-7-methyl-7-azabicyclo[2.2.1]heptan-2-ol (4, RS-11635) is described. The key step of this synthesis consists of the intramolecular trans-diaxial epoxide opening of 4-(N-methylamino)-1,2-epoxycyclohexane (8) to form the endo-azabicyclic structure 9. Evaluation of anticholinergic bronchodilator activity by intravenous administration in methacholine-challenged guinea pigs indicated 4 to be approximately twice as potent as ipratropium bromide (ED50 of 1.1 versus 2 micrograms/kg) and to have a duration of action nearly five times as long (230 versus 50 min). Evaluation of anticholinergic bronchodilator activity by aerosol administration in methacholine-challenged dogs also indicated 4 to be approximately twice as potent as ipratropium bromide and to have a duration of action nearly three times as long.

Syntheses and hypotensive properties of substituted 2-aminotetralins.

The synthesis and activity in the spontaneously hypertensive rat of several 4-(1,2,3,4-tetrahydronaphthyl-2-amino)-1-(4-fluorophenyl)-1-but anones is reported. Maximal antihypertensive activity was associated with 5,6-dimethoxy substitution in the aminotetralin moiety.

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.

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.

The analgesic and anti-inflammatory profile of ketorolac and its tromethamine salt.

Ketorolac tromethamine[(+/-)-5(benzoyl)-2,3-dihydro-1N-pyrrolizine-1-carboxylic acid tris hydroxymethylaminomethane salt] is a highly potent member of a new class of compounds having analgesic and anti-inflammatory activity. When given orally in tests involving underlying inflammation it was a potent analgesic, whereas it was inactive in tests for narcotic activity. It was also highly active orally in rat models of acute and chronic inflammation and pyresis. These properties are mediated primarily via the compound's potent prostaglandin cyclooxygenase inhibitory activity. The agent elicited mild CNS and cardiovascular activity only at doses far in excess of those required for analgesic and anti-inflammatory activity. A single 10 mg tablet given orally to human volunteers following surgery provided pain relief equivalent to that provided by 10 mg of morphine given intramuscularly. When given intramuscularly to rabbits (0.25 ml of a 0.31-5% solution) or man (3 ml of a 1-3% solution), no drug-related irritation or changes in creatine phosphokinase were seen. Solutions (less than or equal to 0.5%) applied to the eyes of animals and man were not irritating. When applied topically in rat and rabbit models of ocular inflammation, less than or equal to 0.5% solutions of ketorolac tromethamine inhibited the inflammatory response.

The cardiovascular pharmacology and hemodynamic activity of tazolol, a selective myocardial beta-stimulant.

The pharmacology and hemodynamics of tazolol (1-iso-propylamino-3-(2-thiazoloxy)-2-propranolol HC1), a selective myocardial beta-stimulant, were studied in pentobarbital anesthetized dogs. Tazolol, i.v., increased myocardial contractile force and heart rate, but induced only minimal changes in arterial pressure. The cardiac effects of tazolol were blocked by pretreatment with the beta-blockers propranolol or practolol and inhibited in animals made tachyphylactic to amphetamine. They were not altered by pretreatment with hexamehtonium, atropine or reserpine. Tazolol increased left circumflex coronary artery flow to a far greater extent than a dose level of isoproterenol which produced a greater increase in cardiac output. Tazolol also increased superior mesenteric artery flow, whereas isoproterenol decreased it. Renal artery flow was not altered. Tazolol was also found to be orally active and to possess some mild general beta-blocking activity.

Antihypertensive drugs: their postural hypotensive effect and their blood pressure lowering activity in conscious normotensive rats.

The postural hypotensive (PH) response to various antihypertensive agents was examined as an independent pharmacologic activity in conscious normotensive rats. Full PH dose-response curves for standard antihypertensive drugs were explored and were compared to their hypotensive dose-response curves. In untreated control rats, only a negligible change in blood pressure occurred in response to a 2 min 90 degrees head-up tilt. However, treatment with an agent acting on the nervous system, pentolinium, resulted in a profound and dose-dependent drop of blood pressure in response to tilt. A comparable hypotensive effect was also induced. Alpha blockers (e.g., prazosin) induced only moderate dose-dependent PH effects while producing profound hypotensive effects. Direct vasodilators (e.g., minoxidil), calcium antagonists (e.g., nifedipine) and a converting enzyme inhibitor, captopril, were virtually free of PH effects despite moderate or profound hypotensive effects. Clonidine exhibited greater PH than hypotensive effects. Propranolol and hydrochlorothiazide did not exhibit PH effects and did not lower blood pressure. With the exception of clonidine, these findings are generally in agreement with human data. It is suggested that the normotensive rat may be a useful model for gaining an insight into a drug's potential for producing postural hypotension in man and that the full PH dose-response curve should be explored.

Role of angiotensin in pressure overload-induced hypertrophy in rats: effects of angiotensin-converting enzyme inhibitors, an AT1 receptor antagonist, and surgical reversal.

The renin-angiotensin system (RAS) has been proposed to play a major role in causing the heart to hypertrophy during pressure overload. We examined whether blockade of this system by the angiotensin-converting enzyme (ACE) inhibitors enalapril (0.5 to 20 mg/kg p.o.) or ramipril (1.0 mg/kg p.o.) or the angiotensin receptor (AT1) antagonist losartan (3.0 mg/kg p.o.) could prevent pressure overload-induced hypertrophy. Pressure overload was produced by abdominal aortic constriction in rats. Cardiac hypertrophy was assessed by an increase in the ratio of left ventricular (LV) weight to body weight and total protein content of the left ventricle. Treatment with enalapril or ramipril, initiated 3 weeks after aortic banding and continued for 3 more weeks, failed to prevent the progression or cause regression of cardiac hypertrophy. Treatment for 6 weeks with ramipril initiated immediately after aortic banding also failed to prevent cardiac hypertrophy. Losartan treatment initiated 3 weeks after aortic banding and continued for 3 more weeks resulted in a slight but significant reduction in the extent of cardiac hypertrophy (45.6% hypertrophy in controls and 35.6% hypertrophy in losartan-treated animals, p < 0.05, n = 11 and 10, respectively). Surgical removal of bands 3 weeks after placement reduced cardiac hypertrophy to a greater extent than that observed in losartan-treated animals. These results suggest that angiotensin may not play a major role in causing pressure overload-induced hypertrophy or in maintaining such hypertrophy.

The importance of catecholamine uptake inhibition in the reversal of guanethidine blockade of adrenergic neurons.

Adrenergic neuron blockade was induced by guanethidine in the pithed rat preparation. The pressor response to spinal electric stimulation was inhibited. The guanethidine blockade was reversed or prevented not only by tricyclic antidepressants but also by tripelennamine (an H1 antihistamine), tranylcypromine (a monoamine oxidase inhibitor) and viloxazine (a new antidepressant structurally unrelated to tricyclic antidepressants). Since these compounds all share neuronal uptake inhibitory activity, it seems that this property per se is sufficient to reverse/prevent the adrenergic neuron blockade induced by guanethdine.