Abstract As an extension of research on analgesic and antiinflammatory compounds, a series of substituted analogues based on the novel 4H-thieno [2′, 3′: 4, 5] pyrimido [2, 1- b] benzothiazole and 4H-thieno [2′, 3′: 4, 5] pyrimido [2, 1-b] benzoxazole ring systems