Condensed thienopyrimidines. I. Synthesis and gastric antisecretory activity of 2,3-dihydro-5H-oxazolothienopyrimidin-5-one derivatives.

A practical preparation of various 2,3-dihydro-5H-oxazolo[3,2-a]thieno[3,2-d]-, [3,4-d]-, and [2,3-d]pyrimidin-5-one derivatives was developed starting from the corresponding aminothiopheneesters in two steps, and their chloro-substituted derivatives were prepared. These compounds were evaluated for gastric antisecretory activity in pylorus-ligated rats, compared to the anti-ulcer standard, cimetidine, and their structure-activity relationships are discussed.