Suk Youn Kang

Biarylpyrazolyl Oxadiazole as Potent, Selective, Orally Bioavailable Cannabinoid-1 Receptor Antagonists for the Treatment of Obesity

Since the CB1 cannabinoid receptor antagonist 1 (SR141716, rimonabant) was previously reported to modulate food intake, CB1 antagonism has been considered as a new therapeutic target for the treatment of obesity. In the present study, biarylpyrazole analogues based on a pyrazole core coupled with 1,3,4-oxadiazole were synthesized and tested for CB1 receptor binding affinity. Thorough SAR studies to optimize pyrazole substituents as well as 1,3,4-oxadiazole ring led to several novel CB1 antagonists with IC(50) approximately 1 nM for the CB1 receptor binding. Among these analogues, we identified 2-(4-((1H-1,2,4-triazol-1-yl)methyl)-5-(4-bromophenyl)-1-(2,4-dichlorophenyl)-1H-pyrazol-3-yl)-5-(1-(trifluoromethyl)cyclopropyl)-1,3,4-oxadiazole 43c as a promising precandidate for the development as an antiobesity agent.

Tetrazole-biarylpyrazole derivatives as cannabinoid CB1 receptor antagonists

Cannabinoid CB1 receptors have been the focus of extensive studies since the first clinical results of rimonabant (SR141716) for the treatment of obesity and related metabolic disorders were reported in 2001. To further evaluate the properties of CB receptors, we have designed a new series of tetrazole-biarylpyrazoles. The various analogues were efficiently prepared and bio-assayed for binding to cannabinoid CB1 receptor. Six of the new compounds which displayed high in vitro CB1 binding affinities were assayed for binding to CB2 receptor. Noticeably, cyclopentyl-tetrazole (9a) demonstrated good binding affinity and selectivity for CB1 receptor (IC(50)=11.6nM and CB2/CB1=366).

Novel C-aryl glucoside SGLT2 inhibitors as potential antidiabetic agents: Pyridazinylmethylphenyl glucoside congeners

Novel C-aryl glucoside SGLT2 inhibitors containing pyridazine motif were designed and synthesized for biological evaluation. Among the compounds tested, pyridazine containing methylthio moiety 22l or thiadiazole ring 22ah showed the best in vitro inhibitory activities in this series (IC(50)=13.4, 11.4nM, respectively) against SGLT2 to date. Subsequently, compound 22l exhibited reasonable urinary glucose excretion and glucosuria in normal SD rats, thereby demonstrating that this pyridazine series possesses both in vitro SGLT2 inhibition and in vivo efficacy, albeit to a lower degree.

Synthesis of pyridazine and thiazole analogs as SGLT2 inhibitors

With anticipation of the improvement in biological aspects in our SGLT2 program, novel pyridazinyl and thiazolyl analogs were designed and efficiently synthesized. The installation of the pyridazine ring at the anomeric carbon of d-glucopyranose was carried out in a stereoselective fashion. On the other hand, a series of thiazolyl analogs was also synthesized through a coupling reaction between perbenzyl gluconolactone 9 and 2-lithiothiazole. Biological activities of the compounds thus prepared were evaluated by the in vitro SGLT2 inhibition assay. Considering assay results, the novel benzylpyridazinyl and benzylthiazolyl analogs, disclosed in this article, could be a quick reference to prospective SGLT2 inhibitors useful for pharmacotherapy.

Arylpiperazine-containing pyrimidine 4-carboxamide derivatives targeting serotonin 5-HT(2A), 5-HT(2C), and the serotonin transporter as a potential antidepressant.

Arylpiperzine-containing pyrrole 3-carboxamide derivatives were synthesized and evaluated as novel antidepressant compounds. The various analogues were efficiently prepared and bio-assayed for binding to 5-HT(2A), 5-HT(2C) receptor, and 5-HT transporter. Based on their in vitro and in vivo activities as well as selectivity over other neurotransmitter receptors and PK profiles, 33 and 34 were identified as lead compounds. Consequently, this pyrrole series of compounds appears to be promising enough to warrant further investigation.

Oxadiazole-diarylpyrazole 4-carboxamides as cannabinoid CB1 receptor ligands

Cannabinoid CB-1 receptors have been the focus of extensive studies since the first clinical results of rimonabant (SR141716) for the treatment of obesity and obesity-related metabolic disorders were reported in 2001. To further evaluate the properties of CB receptors, we have designed and efficiently prepared a series of oxadiazole-diarylpyrazole 4-carboxamides. Six of the new compounds which displayed high in vitro CB1 binding affinities were assayed for binding to CB2 receptor. Noticeably, 5-(4-bromophenyl)-3-(5-tert-butyl-1,3,4-oxadiazol-2-yl)-1-(2,4-dichlorophenyl)-N-phenyl-1H-pyrazole-4-carboxamide (12q) and 5-(4-bromophenyl)-3-(5-tert-butyl-1,3,4-oxadiazol-2-yl)-1-(2,4-dichlorophenyl)-N-(pyridin-2-yl)-1H-pyrazole-4-carboxamide (12r) demonstrated good binding affinity and decent selectivity for CB1 receptor (IC(50) = 1.35 nM, CB2/CB1 = 286 for 12q; IC(50) = 1.46 nM, CB2/CB1 = 256 for 12r).

Design and Synthesis of Novel Arylpiperazine Derivatives Containing the Imidazole Core Targeting 5-HT2A Receptor and 5-HT Transporter

Serotonin antagonist reuptake inhibitor (SARI) drugs that block both 5-HT(2) receptors and the serotonin transporters have been developed. The human 5-HT(2A/2C) receptor has been implicated in several neurological conditions, and potent selective 5-HT(2A/2C) ligands may have therapeutic potential for treatment of CNS diseases such as depression. An imidazole moiety usually provides good pharmacokinetic properties as a drug substance, and thus considerable efforts have been devoted to develop imidazole derivatives into drug candidates. The imidazole series of compounds was evaluated against 5-HT(2A/2C) and serotonin reuptake inhibition. A few of the compounds in the series showed promising IC(50) values and antidepressant-like effect in in vivo forced swimming test (FST). On the basis of these results, further lead optimization studies resulted in identifying promising compounds potentially for therapeutic use.

Glucosides with cyclic diarylpolynoid as novel C-aryl glucoside SGLT2 inhibitors.

Novel C-aryl glucoside SGLT2 inhibitors containing cyclic diarylpolynoid motif were designed and synthesized for biological evaluation. Alkylzinc bromides have been efficiently prepared by the direct insertion of zinc metal into alkyl bromides. The organozinc reagents underwent smooth Pd-catalyzed cross-coupling reactions. Subsequent ring closing metathesis using 2nd generation Grubbs catalyst successfully generated novel class of ansa-compounds. These glucosides with cyclic diarylpolynoids demonstrated moderate in vitro inhibitory activity against SGLT2 in this series to date (IC(50)=59.5-103 nM).

Further optimization of novel pyrrole 3-carboxamides for targeting serotonin 5-HT2A, 5-HT2C, and the serotonin transporter as a potential antidepressant

In the continuing search for novel compounds targeting serotonin 5-HT(2A), 5-HT(2C), and serotonin transporter, new arylpiperazine-containing pyrrole 3-carboxamide derivatives were synthesized and evaluated. Based on the lead reported previously, structural modifications regarding N-(3-(4-(2,3-dichlorophenyl)piperazin-1-yl)propyl)-1,2-dimethyl-5-phenyl-1H-pyrrole-3-carboxamide 5, were accomplished for improvements in not only binding affinity against serotonin receptors and transporter, but also in hERG channel inhibition. Along the line, both the forced swimming tests and spontaneous locomotor activity tests were performed to distinguish between antidepressant activity and false positive results. As potential antidepressant agents, both 2,4-dimethyl-5-phenyl-1H-pyrrole-3-carboxamide and 5-tert-butyl-2-methyl-1H-pyrrole-3-carboxamide derivatives exhibited favorable in vitro and in vivo activities, warranting further investigation around these scaffolds.

Pentacycle derivatives as cannabinoid CB1 receptor ligands

Cannabinoid CB-1 receptors have been the focus of extensive studies since the first clinical results of rimonabant (SR141716) for the treatment of obesity and obesity-related metabolic disorders were reported in 2001. To further evaluate the properties of CB receptors, we have designed and efficiently prepared a series of pentacycle derivatives. Five of the new compounds which displayed high in vitro rCB1 binding affinities were assayed for binding to hCB2 receptor. Noticeably, 2-(5-(4-bromophenyl)-1-(2,4-dichlorophenyl)-4-(5-methyl-1,3,4-thiadiazol-2-yl)-1H-pyrazol-3-yl)-5-(1-(trifluoromethyl)cyclopropyl)-1,3,4-oxadiazole (16l) demonstrated good binding affinity and decent selectivity for rCB1 receptor (IC(50)=1.72 nM, hCB2/rCB1=142).