Synthesis and enzymic activity of some novel xanthine oxidase inhibitors. 3-Substituted 5,7-dihydroxypyrazolo(1,5-alpha)pyrimidines.

A series of 3-substituted 5,7-dihydroxypyrazolo[1,5-alpha]pyrimidines containing various aromatic [phenyl- (3e), 3-pyridyl- (3f), p-bromophenyl- (3g), p-chlorophenyl- (3h), p-acetamidophenyl- (3i), p-tolyl- (3j), m-tolyl- (3k), 3,4-methylenedioxyphenyl- (3m), or naphthyl- (3n)] or nonaromatic [hydrogen- (3a), nitro- (3b), bromo- (3c), or chloro- (3d)] substituents in the 3 position was synthesized and tested as inhibitors of xanthine oxidase. The compounds (3a-m) were synthesized by condensation of the appropriate 3-amino-4-substituted pyrazole with diethyl malonate in alcoholic sodium methoxide and neutralization of the resulting enol sodium salts. As inhibitors of xanthine oxidase, 3e-n greater than 3a,c,d congruent to allopurinol greater than 3b. The 3-aryl-substituted compounds 3e-n were 30-160 times better xanthine oxidase inhibitors than allopurinol using hypoxanthine as substrate and 10-80 times better using xanthine as substrate, as evidenced by a comparison of Ki values. The inhibition by all compounds (3a-n) was totally reversible and of the noncompetitive or mixed type. A study of the pH dependence of xanthine oxidase inhibition by 3a,e,g and allopurinol indicated that the 3-aryl substituents facilitated binding to the enzyme. These and the above results show that the compounds reported here inhibit xanthine oxidase by a mechanism which is significantly different from that of allopurinol.

Synthesis and antitrichomonal activity of certain pyrazolo (1,5-a) pyrimidines.

Several bridgehead nitrogen heterocycles were synthesized to be screened as antimicrobial agents, modeled after nalidixic acid. The activity of these new compounds, all derivatives of 3-nitro-4,6-disubstituted pyrazolo (1,5-a)pyrimidin-7-ones (3,7,8, and 9), however, was found to be highly specific for Trichomonas foetus and completely lacking in activity against bacteria, fungi, and parasites other than Trichomonas. Of the nine componds synthesized, including the intermediate 4,6-disubstituted pyrazolo (1,5-a) pyrimidin-7-ones (2-6) and the 6-substituted or unsubstituted pyrazolo (1,5-a) pyrimidin-7-ones (1 and 4), only 6-carbethoxy-4-ethyl-3-nitropyrazolo(1,5-a)pyrimidin-7-one (7) was found to be a potent antitrichomal agent, being comparable or perhaps better than metronidazole. From a tentative structure-activity relationship study, it was apparent that the combination of the 3-mitro, 4-ethyl, and 6-carbethoxy groups imparted specific activity, wheras other substitutions imparted little or no antitrichomonal activity.

Adenosine cyclic 3',5',-monophosphate phosphodiesterasr inhibitors. 2.3-Substituted 5,7-dialkylpyrazolo [1,5-a]pyrimidines.

A number of 3-bromo-, 3-nitro-, and 3-ethoxycarbonyl-5,7-dialkylpyrazolo[1,5-a]pyrimidines were synthesized and screened as in vitro cAMP phosphodiesterase inhibitors. The condensation of 3-aminopyrazole with symmetrical beta-diketones (acetylacetone, heptane-3,5-dione, etc.) afforded symmetrical dialkylpyrazolo[1,5-a]pyrimidines (5). The reaction of 3-aminopyrazole with unsymmetrical beta-diketones (hexane-2,4-dione, heptane-3,5-dione, etc.) gave a mixture of 5-methyl-7-alkylpyrazolo[1,5-a]pyrimidine (3) and 5-alkyl-7-methylpyrazolo[1,5-a]pyrimidines (4). The technique for the separation of 3 from 4 is described. The inhibition constants, alpha (the ratio of the molar I50 of theophylline to the molar I50 of the test compounds), were subjected to a Hansch correlation analysis. The results indicated that PDE isolated from beef heart tissue was most sensitive to changes in the length of the alkyl group in the 5 position of the pyrazolo[1,5-a]pyrimidine ring, whereas the PDE isolated from rabbit lung tissue was more sensitive to changes in the length of the 7-alkyl group. Experimentally and theoretically, the n-propyl group was found to approximate the ideal size for the alkyl group in both the 5 and 7 positions;5,7-di-n-propyl-3-ethoxycarbonylpyrazolo[1,5-a]pyrimidine (5e) was the most potent inhibitor of both lung and heart PDE.

Synthesis and enzymic activity of 6-carbethoxy- and 6-ethoxy-3,7-disubstituted-pyrazolo[1,5-a]pyrimidines and related derivatives as adenosine cyclic 3' ,5'-phosphate phosphodiesterase inhibitors.

A number of 3,7-disubstituted 6-carbethoxypyrazolo [1,5-a] pyrimidines and 3,7-disubstituted 6-ethoxypyrazolo-[1,5-a]pyrimidines have been prepared and evaluated as adenosine cyclic 3',5'-phosphate (cAMP) phosphodiesterase (PDE) inhibitors vs. the low Km enzyme isolated from beef heart, rabbit lung, and kidney preparations. The results were found to be between 0.5 to 13 times as potent as theophylline as inhibitors of PDE, depending on the tissue source. A number of these PDE inhibitors exhibited significant physiological effects in different animal systems, suggesting it should be possible to obtain selective PDE inhibition in various tissues. Several of these heterocycles were found superior to adenosine in inhibiting ADP-induced platelet aggregation in vitro.

Synthesis and enzymic activity of various substituted pyrazolo[1,5-a]-1,3,5-triazines as adenosine cyclic 3',5'-phosphate phosphodiesterase inhibitors.

A series of various pyrazolo[1,5-a]-1,3,5-triazines have been prepared and studied as inhibitors of cAMP phosphodiesterase isolated from bovine brain, bovine heart, and rabbit lung. A number of compounds were found to be superior to theophylline. 2-Ethyl-7-phenylpyrazolo[1,5-a]-1,3,5-triazine (35) was found to be 97 times more potent than theophylline as an inhibitor of bovine brain PDE. 8-Bromo-2,4-dimethyl-7-phenylpyrazolo[1,5-a]-1,3,5-triazine (52) showed alpha lung = 40 compared to alpha heart = 3.0. Thus, various substituents could increase or decrease the inhibition relative to the type and source of tissue from which the PDE was isolated. The most active compound was 8-bromo-4-(diethylamino)-7-phenylpyrazolo[1,3-a]-1,3,5-triazine (25), which was 185 times more potent than theophylline as an inhibitor of PDE isolated from rabbit lung. The stepwise synthesis via ring-closure procedures of requisite pyrazole intermediates, followed by electrophilic substitution in the pyrazole ring and/or nucleophilic substitution in the 1,3,5-triazine moiety, resulted in the various pyrazolo[1,5-a]1,3,5-triazines listed in Tables I and II. Structure-activity relationships are reviewed.

2-(Alkylthio)-1,2,4-triazolo[1,5-a]pyrimidines as adenosine cyclic 3',5'-monophosphate phosphodiesterase inhibitors with potential as new cardiovascular agents.

A series of new 2-(alkylthio)-5,7-disubstituted-1,2,4-triazolo[1,5-a]pyrimidines have been prepared as inhibitors of cAMP phosphodiesterase from various tissues. These derivatives were prepared via ring closure of various requisite 3-amino-1,2,4-triazole intermediates. 2-(Benzylthio)-5-methyl-7-(dimethylamino)-1,2,4-triazolo[1,5-a]pyrimidine (15a) is 6.3 times as potent as theophylline in inhibiting cAMP PDE isolated from rabbit heart. Treatment of dogs intravenously with 5 (mg/kg)/h of 15a gave a cardiac output increase of 69%, which was largely sustained for a 2-h period after administration of drug had ceased. There was no significant increase in heart rate upon administration of 15a. Related studies with 5,7-di-n-propyl-2-(benzylthio)-1,2,4-triazolo[1,5-a]pyrimidine (22a) in five dogs showed a 31.5% increase in cardiac output with an increase in stroke volume of 34.4% with no increase in heart rate. The specificity of action of these PDE inhibitors could be due to selective binding at a certain cAMP PDE site in the cardiovascular system. Several of these compounds are candidates for further studies with a view to clinical evaluation.

Once-daily verapamil in the treatment of mild-to-moderate hypertension: a double-blind placebo-controlled dose-ranging study.

Supine office blood pressures (SOBP) and 24-hour automated ambulatory blood pressure monitorings (AABPM) showed blood pressure reductions from a stable baseline to active treatment with 120-, 240-, and 480-mg doses of a new verapamil QD capsule (solid-spheroidal-oral once-daily drug-absorption system: (SODAS) in patients with mild-to-moderately severe (diastolic blood pressures 95-119 mm Hg) essential hypertension. Reductions were documented at 24 hours, hourly, and by the 24 hour average, using SOBP and AABPM, after the once-daily verapamil administration. Both SOBP and the 24-hour average by AABPM were significantly reduced from baseline by active verapamil treatment of 120-, 240-, and 480-mg doses. In comparison to verapamil QD (0 mg), blood pressure reductions from baseline to active treatment were significant at the 240- and 480-mg doses but not at the 120-mg dose. There was a significant linear dose response. This verapamil formulation (SODAS) was effective throughout the 24-hour period after once-daily dosing.