Synthesis and evaluation of potent and selective c-GMP phosphodiesterase inhibitors

Syntheses and structure-activity relationships (SAR) of cGMP selective phosphodiesterase inhibitors are discussed. Potent and selective inhibitors are produced when the C-2 position of tetracyclic guanine 1 is substituted with alkyl chains containing six carbon atoms.

Synthesis and evaluation of polycyclic pyrazolo[3,4-d]pyrimidines as PDE1 and PDE5 cGMP phosphodiesterase inhibitors

Polycyclic pyrazolo[3,4-d]pyrimidines (represented by 3 and 4) were synthesized as analogues of the recently reported polycyclic guanine phosphodiesterase (PDE) inhibitors. From the structure-activity relationship (SAR) development of a series of compounds, it was discovered that C-3 benzyl and N-2 methyl disubstitution on the pyrazole ring gave the best combination of potency and selectivity for PDE1 and PDE5 cGMP PDEs as represented by compound 4c: PDE1, IC50 = 60 nM; PDE3, IC50 = 55,000 nM; PDE5, IC50 = 75 nM. These compounds were also evaluated in vivo and found to be good orally active antihypertensives in laboratory animal models. Finally, comparisons were made of the in vitro and in vivo profiles of the pyrazolo-[3,4-d]pyrimidine compound 4c with those of two representative guanine compounds.

Potent tetracyclic guanine inhibitors of PDE1 and PDE5 cyclic guanosine monophosphate phosphodiesterases with oral antihypertensive activity

Tetracyclic guanines have been shown to be potent and selective inhibitors of the cGMP-hydrolyzing enzymes PDE1 and PDE5. In general, these compounds are inactive or only weakly active as inhibitors of PDE3, which is a major isozyme involved in cAMP hydrolysis. Structure-activity relationships are developed at N-1, C-2, N-3, and N-5 on the core nucleus. Compound 31, with an IC50 of 70 pM, is the most potent inhibitor of PDE1, while 50, with an IC50 of 4 nM, is the most potent inhibitor of PDE5. Compounds 20, 22, 30, and 50 are potent dual inhibitors with IC50 values below 30 nM for both PDE1 and PDE5. Compounds 12, 20, and 28 reduced blood pressure by more than 45 mmHg when administered orally at 10 mg/kg to the spontaneously hypertensive rat (SHR).