Synthesis and pharmacological activity of 2-alkylthio substituted thieno[2,3-d]pyrimidine-4-one and 5H-pyrimido [5,4-b]indol-4-one.

Quaternary salts of several 2-alkylthio substituted derivatives of thieno [2,3-d]pyrimidin-4-one and 5H-pyrimido [5,4-b]indol-4-one with a basic group in position 2 of the alkyl chain were synthesized and screened for potential spasmolytic activity. These substances were prepared by condensation of the corresponding mercapto compounds with a 2-chloroalkyltertiary amine. The tertiary bases were quaternized with methyl iodide. Among the assayed compounds, the thieno [2-3-d]pyrimidin-4-one derivatives displayed a potent spasmolytic activity in the in vitro and in vivo assays.