Design and synthesis of novel annulated thienopyrimidines as phosphodiesterase 5 (PDE5) inhibitors

Novel cycloalkene-fused thienopyrimidine analogues with enhanced phosphodiesterase 5 (PDE5) inhibitory properties are presented. The structure of the reported scaffold was modulated through variation of the terminal cycloalkene ring size, as well as by varying the substituents at position 4 through the attachment of different groups including aniline, benzylamine, cyclohexylethylamine, methyl/acetyl/aryl piperazines, and aryl hydrazones. Compound 15Y with a benzylamine substituent and cycloheptene as terminal ring showed the highest PDE5 inhibitory activity with an IC50 value as low as 190 nM and with good selectivity versus PDE7 and PDE9.