cAMP-dependent phosphodiesterase inhibition and SAR studies on novel 6,8-disubstituted 2-phenyl-3-(substituted benzothiazole-2-yl)-4[3 H]-quinazolinone.

Two series of 6,8-disubstituted-2-phenyl-3-(substituted benzothiazole-2-yl)-4[3 H]-quinazolinone ( 1–13 and 14–26) were synthesized by reported method and evaluated for their phosphodiesterase inhibitory activity. All test compounds exhibited good activity. The structure–activity relationships based on the results obtained for these series were also studied. In both series, electron-withdrawing substitutions showed more activity. Among the tested compounds 6,8-dibromo-2-phenyl-3-(5-chloro benzothiazole-2-yl)-4[3 H]-quinazolinone ( 20) and 6,8-dibromo-2-phenyl-3-(6-nitro benzothiazole-2-yl)-4[3 H]-quinazolinone ( 24) were found to be even more potent than theophylline (IC₅₀ of 1438 ± 85 μM for 20 and 1520 ± 48 μM for 24). [ABSTRACT FROM AUTHOR]