Syntheses of some pyrazolo[1,5-a]pyrimidines were performed in order to study the relationship between structural modifications on the parent 4,7-dihydro-2-phenylpyrazolo[1,5-a]pyrimidin-7-one (1) and their antiinflammatory properties. The modifications carried out were introduction and functionalization of a longer side chain at the 4-position, substitution of the hydrogen atom at the 3-position, and replacement of the phenyl group with a 4-methylphenyl, methyl, or hydrogen substituent. 4-Ethyl-4,7-dihydro-2-phenylpyrazolo [1,5-a]pyrimidin-7-one (3) showed the highest activity and a better therapeutic index than phenylbutazone and indomethacin, used as reference drugs. All other changes at the 3-, 5-, and 6-positions, as well as the replacement of the phenyl group at position 2, caused a marked decrease of activity. Compound 3 was found devoid of ulcerogenic activity and was probably endowed with antiulcerogenic properties.

中文翻译：

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2-苯基吡唑并[1，5-a]嘧啶-7-酮。新型的非甾体类抗炎药，无溃疡活性。

为了研究母体4,7-二氢-2-苯基吡唑并[1,5-a]嘧啶-7-一的结构修饰之间的关系，进行了一些吡唑并[1,5-a]嘧啶的合成（1）及其抗炎特性。进行的修饰是在4-位上引入和官能化更长的侧链，在3-位上取代氢原子，并用4-甲基苯基，甲基或氢取代基取代苯基。与用作参考药物的苯基丁氮酮和消炎痛相比，4-乙基-4,7-二氢-2-苯基吡唑并[1,5-a]嘧啶-7-一（3）具有最高的活性和更好的治疗指数。3-位，5-位和6-位的所有其他变化以及位置2处的苯基取代导致活性显着下降。