Exploration of SAR for novel 2-benzylbenzimidazole analogs as inhibitor of transcription factor NF-κB.

A novel series of 2-benzylbenzimidazole analogs was designed, synthesized and investigated for their in vitro activities against LPS induced NF-κB inhibition in RAW 264.7 cells using the SEAP assay. Among them, 4-((4-(cyclohexylmethoxy)-1H-benzo[d]imidazol-2-yl)methyl)phenol (6e, >100% inhibition at 30 µM, IC50 = 3.0 µM), 4-((5-(cyclohexylmethoxy)-1H-benzo[d]imidazol-2-yl)methyl)phenol (6j, 96% inhibition at 30 µM, IC50 = 4.0 µM) and 2-((4-(cyclohexylmethoxy)-1H-benzo[d]imidazol-2-yl)methyl)phenol (6k, 95% inhibition at 30 µM, IC50 = 5.0 µM) showed strong inhibitory activity. The structure activity relationship confirmed that the substitution on benzimidazole ring A with hydrophobic cyclohexylmethoxy group at position 4 or 5 markedly enhances the activity. In addition, the hydrophilic hydrogen bonding donor group (OH) at position 2 or 4 on phenyl ring B connected with one methylene spacer to the benzimidazole ring is favorable for the inhibitory activity. However, hydrophobic (-OCH3 and -Cl) groups on phenyl ring B decrease the activity.

Discovery of enantioselectivity of urea inhibitors of soluble epoxide hydrolase.

Soluble epoxide hydrolase (sEH) hydrolyzes epoxyeicosatrienoic acids (EETs) in the metabolic pathway of arachidonic acid and has been considered as an important therapeutic target for chronic diseases such as hypertension, diabetes and inflammation. Although many urea derivatives are known as sEH inhibitors, the enantioselectivity of the inhibitors is not highlighted in spite of the stereoselective hydrolysis of EETs by sEH. In an effort to explore the importance of enantioselectivity in the urea scaffold, a series of enantiomers with the stereocenter adjacent to the urea nitrogen atom were prepared. The selectivity of enantiomers of 1-(α-alkyl-α-phenylmethyl)-3-(3-phenylpropyl)ureas showed wide range differences up to 125 fold with the low IC50 value up to 13 nM. The S-configuration with planar phenyl and small alkyl groups at α-position is crucial for the activity and selectivity. However, restriction of the free rotation of two α-groups with indan-1-yl or 1,2,3,4-tetrahydronaphthalen-1-yl moiety abolishes the selectivity between the enantiomers, despite the increase in activity up to 13 nM. The hydrophilic group like sulfonamido group at para position of 3-phenylpropyl motif of 1-(α-alkyl-α-phenylmethyl-3-(3-phenylpropyl)urea improves the activity as well as enantiomeric selectivity. All these ureas are proved to be specific inhibitor of sEH without inhibition against mEH.

Exploration of 2-benzylbenzimidazole scaffold as novel inhibitor of NF-κB.

For finding the novel inhibitor of nuclear factor κB activity, a series of benzimidazole derivatives were rationally designed, synthesized and systematically studied for their in vitro activities against LPS induced NF-κB inhibition in RAW 264.7 cells using the SEAP assay based on the flexible chalcone JSH ((E)-1-(2-hydroxy-6-(isopentyloxy)phenyl)-3-(4-hydroxy phenyl)prop-2-en-1-one) which was previously reported. Although most of the benzimidazole derivatives showed strong inhibitory activity in low micromolar potency, 2-(4-methoxybenzyl)-1H-benzo[d]imidazole (3m; IC50=1.7 µM) and 2-(2-methoxybenzyl)-1H-benzo[d]imidazole (3n; IC50=2.4 µM) showed the best inhibition. The structure activity relationship revealed that 2-benzylbenzimidazole scaffold with hydrogen bonding acceptor on phenyl ring appears as a pharmacophore.

Exploration of Pharmacophore in Chrysosplenol C as Activator in Ventricular Myocyte Contraction.

Chrysosplenol C (4',5,6-trihydroxy-3,3',7-trimethoxyflavone) isolated from Miliusa balansae has unique structural features as a reversible inotropic agent independent of ß-adrenergic signaling and with selective activation of cardiac myosin ATPase. Hence, a series of chrysosplenol analogues were synthesized and explored for identification of pharmacophore that is essential for the increasing contractility in rat ventricular myocytes. Analogue 7-chloro-2-(3-hydroxyphenyl)-3-methoxy-4H-chromen-4-one showed highly potent contractility (54.8% at 10 µM) through activating cardiac myosin ATPase (38.7% at 10 µM). Our systematic structure-activity relationship study revealed that flavonoid nucleus of chrososplenol C appears to be an essential basic skeleton and hydrophobic substituent at position 7 of chromenone such as methoxy or chloro enhances the activity. Additionally, our ATPase study suggested that these chrysosplenol analogues have selectivity toward cardiac myosin activation. Thus, the novel flavonone with 3-/7-hydrophobic substituent and 3'-hydrogen bonding donor function is a novel scaffold for discovery of a new positive inotropic agent.

Exploration of benzamidochromenone derivatives with conformational restrictor as interleukin-5 inhibitors.

Novel amidochromen-4-one analogs 8a-k and 9a-f were prepared and studied for their IL-5 inhibitory activity. Among the synthesized compounds, (6-benzamido-2-cyclohexyl-4-oxo-4H-chromen-3-yl)methyl acetate (8a, 95% inhibition at 30 µM, IC50=6.1 µM) exhibited potent IL-5 inhibitory activity. The conformational restrictor at position 2 like bulky cyclohexyl group is favorable for the formation of effective conformer of side chain small ester like acetoxymethyl at position 3 of these chromenone analogs 8. In addition the hydrophobic planarity of benzamido group at position 6 should be important for the potent IL-5 inhibitory activity. Since replacing acetoxymethyl moiety with hydroxymethyl group at position 3 of chromenone decreases the activity, which indicates that the location of hydrogen bonding group should be near 4 atom distances away from chromenone ring is more optimum for the activity. Therefore, these benzamidochromen-4-one analogs 8 are novel scaffold for finding potent interleukin-5 inhibitors.