Feb 1, 1976

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

Journal of Medicinal Chemistry
R H SpringerJ P Miller


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 t...Continue Reading

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Mentioned in this Paper

Xanthine Oxidase
Spectrophotometry, Ultraviolet
Bos indicus
Hydrogen-Ion Concentration

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