A series of N-1, 3 disubstituted 2, 1, 3-benzothiadiazine derivatives (BTDs) were synthesized and evaluated for their inhibitory activity versus enzymatic isoform PDE4 extracted from U937 cell line. Some of the tested compounds showed a high PDE4 inhibitory activity at 100 μM and the IC50 value of the most interesting terms were evaluated. The structure–activity relationships of these compounds showed that the 3, 5-di-tert-butyl-4-hydroxybenzyl ...