Condensed isoquinolines. 35*. Synthesis and reactions of 4h-thieno[3′,4′:5,6]pyrimido-[1,2-<Emphasis Type="Italic">b</Emphasis>]isoquinoline-4,11(5H)-dione

Derivatives of the previously unknown tetracyclic system 4H-thieno3′,4′:5,6]pyrimido1,2-b]iso-quinoline-4,11(5H)-dione have been synthesized. A comparison of the spectral characteristics and the biological activities of these compounds has been carried out, and also of their positional isomers and benzene isosteres. The differences, associated with the position of the sulfur atom, are most reflected in their electronic spectra.