Novel selective PDE4 inhibitors. 1. Synthesis, structure-activity relationships, and molecular modeling of 4-(3,4-dimethoxyphenyl)-2H-phthalazin-1-ones and analogues.
A number of 6-(3,4-dimethoxyphenyl)-4,5-dihydro-2H-pyridazin-3-ones and a novel series of 4-(3,4-dimethoxyphenyl)-2H-phthalazin-1-ones were prepared and tested on the cGMP-inhibited phosphodiesterase (PDE3) and cAMP-specific phosphodiesterase (PDE4) enzymes. All tested compounds were found to specifically inhibit PDE4 except for pyridazinone 3b, which showed moderate PDE4 (pIC(50) = 6.5) as well as PDE3 (pIC(50) = 6.6) inhibitory activity. In both the pyridazinone and phthlazinone series it was found that N-substitution is beneficial for PDE4 inhibition, whereas in the pyridazinone series it also accounts for PDE4 selectivity. In the phthalazinone series, the cis-4a,5,6,7,8,8a-hexahydrophthalazinones and their corresponding 4a,5,8,8a-tetrahydro analogues showed potent PDE4 inhibitory potency (10/11c,d: pIC(50) = 7.6-8.4). A molecular modeling study revealed that the cis-fused cyclohexa(e)ne rings occupy a region in space different from that occupied by the other fused (un)saturated hydrocarbon rings applied; we therefore assume that the steric interactions of these rings with the binding site play an important role in enzyme inhibition.
Van der Mey
M
M
Leiden/Amsterdam Center for Drug Research, Division of Medicinal Chemistry, Department of Pharmacochemistry, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam. mmeijJ@rnc.vu.nl
Hatzelmann
A
A
Van der Laan
I J
IJ
Sterk
G J
GJ
Thibaut
U
U
Timmerman
H
H
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D001792:Blood Platelets / Q000201:enzymology; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007962:Leukocytes / Q000201:enzymology; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D010793:Phthalazines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship
C432697:2-benzyl-4-(3,4--dimethoxyphenyl)-4a,5,6,7,8,8a-hexahydro-2H-phthalazin-1one; C432696:2-benzyl-4-(3,4-dimethoxyphenyl)-4a,5,8,8a-tetrahydro-2H-phthalazin-1-one; D004791:Enzyme Inhibitors; D010793:Phthalazines; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4