1,5-Benzodiazepine inhibitors of HCV NS5B polymerase

Optimization through parallel synthesis of a novel series of hepatitis C virus (HCV) NS5B polymerase inhibitors led to the identification of (R)-11-(4-benzyloxy-2-fluorophenyl)-6-hydroxy-3,3-dimethyl-10-(6-methylpyridine-2-carbonyl)-2,3,4,5,10,11-hexahydro-dibenzo[b,e][1,4]diazepin-1-one 11zc and (R)-11-(4-benzyloxy-2-fluorophenyl)-6-hydroxy-3,3-dimethyl-10-(2,5-dimethyloxazol-4-carbonyl)-2,3,4,5,10,11-hexahydro-dibenzo[b,e][1,4]diazepin-1-one 11zk as potent (replicon EC₅₀ = 400 nM and 270 nM, respectively) and selective (CC₅₀ > 20 μM) inhibitors of HCV replication. These data warrant further lead-optimization efforts.     

Novel 4-N-substituted aryl but-3-ene-1,2-dione derivatives of piperazinyloxazolidinones as antibacterial agents

Novel (5S)-N-[3-(3-fluoro-4-{4-[2-oxo-4-(substituted aryl)-but-3-enoyl]-piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-acetamide 3a–j analogues were synthesized and their in vitro antibacterial activity was evaluated. Most of the compounds of series showed superior in vitro activity against Gram-positive resistant strains than linezolid. Compound 3f is the most potent compound in the series with 0.04–0.39 μg/mL MIC.     

Chemical constituents from Saussurea cordifolia

Thirty-six naturally occurring compounds, including four C₁₀-acetylenic glycosides and a lignan, were isolated from the whole plants of Saussurea cordifolia. Their structures were elucidated by means of spectroscopic and chemical methods to be 4,6-decadiyne-1-O-β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranoside (1), 4,6-decadiyne-1-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside (2), (8E)-decaene-4, 6-diyn-1-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside (3), (8Z)-decaene-4,6-diyn-1-O-β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranoside (4), and (2R, 3S, 4S)-4-(4-hydroxy-3-methoxybenzyl)-2-(5-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-tetrahydrofuran-3-ol (5).     

Synthesis and biological evaluation of novel propargyl amines as potential fluorine-18 labeled radioligands for detection of MAO-B activity

The aim of this project was to synthesize and evaluate three novel fluorine-18 labeled derivatives of propargyl amine as potential PET radioligands to visualize monoamine oxidase B (MAO-B) activity.The three fluorinated derivatives of propargyl amine ((S)-1-fluoro-N,4-dimethyl-N-(prop-2-ynyl)-pent-4-en-2-amine (5), (S)-N-(1-fluoro-3-(furan-2-yl)propan-2-yl)-N-methylprop-2-yn-1-amine (10) and (S)-1-fluoro-N,4-dimethyl-N-(prop-2-ynyl)pentan-2-amine (15)) were synthesized in multi-step organic syntheses. IC₅₀ values for inhibition were determined for compounds 5, 10 and 15 in order to determine their specificity for binding to MAO-B. Compound 5 inhibited MAO-B with an IC₅₀ of 664 ± 48.08 nM. No further investigation was carried out with this compound. Compound 10 inhibited MAO-B with an IC₅₀ of 208.5 ± 13.44 nM and compound 15 featured an IC₅₀ of 131.5 ± 0.71 nM for its MAO-B inhibitory activity. None of the compounds inhibited MAO-A activity (IC₅₀ > 2 μM).The fluorine-18 labeled analogues of the two higher binding affinity compounds (10 and 15) (S)-N-(1-[¹⁸F]fluoro-3-(furan-2-yl)propan-2-yl)-N-methylprop-2-yn-1-amine (16) and (S)-1-[¹⁸F]fluoro-N,4-dimethyl-N-(prop-2-ynyl)pentan-2-amine (18) were both prepared from the corresponding precursors 9A, 9B and 14A, 14B by a one-step fluorine-18 nucleophilic substitution reaction. Autoradiography experiments on human postmortem brain tissue sections were performed with 16 and 18. Only compound 18 demonstrated a high selectivity for MAO-B over MAO-A and was, therefore, chosen for further examination by PET in a cynomolgus monkey.The initial uptake of 18 in the monkey brain was 250% SUV at 4 min post injection. The highest uptake of radioactivity was observed in the striatum and thalamus, regions with high MAO-B activity, whereas lower levels of radioactivity were detected in the cortex and cerebellum. The percentage of unchanged radioligand 18 was 30% in plasma at 90 min post injection.In conclusion, compound 18 is a selective inhibitor of MAO-B in vitro and demonstrated a MAO-B specific binding pattern in vivo by PET in monkey. It can, therefore, be considered as a candidate for further investigation in human by PET.     

Synthesis and biological evaluation of substituted 2-phenyl-2H-indazole-7-carboxamides as potent poly(ADP-ribose) polymerase (PARP) inhibitors

A potent series of substituted 2-phenyl-2H-indazole-7-carboxamides were synthesized and evaluated as inhibitors of poly (ADP-ribose) polymerase (PARP). This extensive SAR exploration culminated with the identification of substituted 5-fluoro-2-phenyl-2H-indazole-7-carboxamide analog 48 which displayed excellent PARP enzyme inhibition with IC₅₀ = 4 nM, inhibited proliferation of cancer cell lines deficient in BRCA-1 with CC₅₀ = 42 nM and showed encouraging pharmacokinetic properties in rats compared to the lead 6.     

Synthesis and pharmacological evaluation of optically pure,novel carbonyl guanidine derivatives as dual 5-HT2B and 5-HT7 receptor antagonists

A series of 9-disubstituted N-(9H-fluorene-2-carbonyl)guanidine derivatives have been discovered as potent and orally active dual 5-HT_2B and 5-HT₇ receptor antagonists. Upon screening several compounds, N-(diaminomethylene)-4′,5′-dihydro-3′H-spiro[fluorene-9,2′-furan]-2-carboxamide (17) exhibited potent affinity for both 5-HT_2B (K_i = 5.1 nM) and 5-HT₇ (K_i = 1.7 nM) receptors with high selectivity over 5-HT_2A, 5-HT_2C, α₁, D₂ and M₁ receptors. Optical resolution of the intermediate carboxylic acid 16 via the formation of diastereomeric salts using chiral alkaloids gave the optically pure compounds (R)-17 and (S)-17. Both enantiomers suppressed 5-HT-induced dural protein extravasation in guinea pigs in a dose-dependent manner and the amount of leaked protein was suppressed to near normal levels when orally administrated at 10 mg/kg. (R)-17 and (S)-17 were therefore selected as candidates for human clinical trials.     

Design,synthesis and evaluation of [3H]PF-7191, a highly specific nociceptin opioid peptide (NOP) receptor radiotracer for in vivo receptor occupancy (RO) studies

Herein we report the identification of (+)-N-(2-((1H-pyrazol-1-yl)methyl)-3-((1R,3r,5S)-6′-fluoro-8-azaspiro[bicyclo[3.2.1]octane-3,1′-isochroman]-8-yl)propyl)-N-[³H]-methylacetamide {[³H]PF-7191 [(+)-11]} as a promising radiotracer for the nociceptin opioid peptide (NOP) receptor. (+)-11 demonstrated high NOP binding affinity (K_i = 0.1 nM), excellent selectivity over other opioid receptors (>1000×) and good brain permeability in rats (C_b,u/C_p,u = 0.29). Subsequent characterization of [³H](+)-11 showed a high level of specific binding and a brain bio-distribution pattern consistent with known NOP receptor expression. Furthermore, the in vivo brain binding of [³H](+)-11 in rats was inhibited by a selective NOP receptor antagonist in a dose–responsive manner. This overall favorable profile indicated that [³H](+)-11 is a robust radiotracer for pre-clinical in vivo receptor occupancy (RO) measurements and a possible substrate for carbon-11 labeling for positron emission tomography (PET) imaging in higher species.     

(2S,4S)-1-[2-(1,1-Dimethyl-3-oxo-3-pyrrolidin-1-yl-propylamino)acetyl]-4-fluoro-pyrrolidine-2-carbonitrile: A potent,selective, and orally bioavailable dipeptide-derived inhibitor of dipeptidyl peptidase IV

A series of 2-[3-[2-[(2S)-2-cyano-1-pyrrolidinyl]-2-oxoethylamino]-3-methyl-1-oxobutyl]-based DPP-IV inhibitors with various monocyclic amines were synthesized. The structure–activity relationships (SAR) led to the discovery of potent DPP-IV inhibitors, having IC₅₀ values of <100 nM with excellent selectivity over the closely related enzymes, DPP-II, DPP8, DPP9 and FAP (IC₅₀ > 20 μM). Of these compounds, the analogues 12a, 12h and 12i exhibited a long-lasting ex vivo DPP-IV inhibition in rats.     

Asymmetric synthesis and effect of absolute stereochemistry of YCZ-2013, a brassinosteroid biosynthesis inhibitor

The four stereoisomers of 2RS,4RS-1-[[2-(2,4-dichlorophenyl)-4-(2-(2-propenyloxy)phenoxymethyl)-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole (YCZ-2013), a novel brassinosteroid biosynthesis inhibitor, were prepared. The diastereomers of 2RS,4R-5 and 2RS,4S-5 were prepared by using the corresponding optically pure R and S toluene-4-sulfonic acid 2,3-dihydroxypropyl ester (R-4,S-4). The enatiomerically and diastereomerically pure acetonide (5) was obtained by a method involving diastereoselective crystallisation of the tosylate salt, followed by re-equilibration with the mother liquor and chromatography. The optical purity of four target compounds (YCZ-2013) was confirmed by chiral high-performance liquid chromatography (HPLC) and NMR. The effects of these stereoisomers on Arabidopsis stem elongation indicated that the cis isomers of 2S,4R-YCZ-2013 and 2R,4S-YCZ-2013 exhibited potent inhibitory activity with IC₅₀ values of approximately 24 ± 3 and 24 ± 2 nM, respectively. The IC₅₀ values of the trans isomers of 2S,4S-YCZ-2013 and 2R,4R-YCZ-2013 are approximately 1510 ± 50 and 3900 ± 332 nM, respectively. Co-application of brassinolide (10 nM), the most potent BR, and GA₃ (1 μM) to Arabidopsis seedlings grown in the dark with 2R,4S-YCZ-2013 and 2S,4R-YCZ-2013 revealed that brassinolide recovered the induced dwarfism of Arabidopsis seedlings, whereas GA₃ showed no effect.     

Novel and potent small-molecule urotensin II receptor agonists

A series of analogs of the non-peptidic urotensin II receptor agonist N-[1-(4-chlorophenyl)-3-(dimethylamino)propyl]-4-phenylbenzamide (FL104) has been synthesized and evaluated pharmacologically. The enantiomers of the two most potent racemic analogues were obtained from the corresponding diastereomeric mandelic amides. In agreement with previously observed SAR, most of the agonist potency resided in the (S) enantiomers. The most potent UII receptor agonist in the new series was (S)-N-[3-dimethylamino-1-(2-naphthyl)propyl]-4-(4-chlorophenyl)benzamide (EC₅₀ = 23 nM at the urotensin II receptor).     

Substituted pyrimidines as cannabinoid CB1 receptor ligands

Cannabinoid CB1 receptors have been the avenue 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 substituted pyrimidines based on chemical structure of Merck’s taranabant, a cannabinoid CB1 receptor inverse agonist. Noticeably, N4-((2S,3S)-3-(3-bromophenyl)-4-(4-chlorophenyl)butan-2-yl)-N6-butylpyrimidine-4,6-diamine (13b) demonstrated good binding affinity and decent selectivity for CB1 receptor (IC₅₀ = 16.3 nM, CB2/CB1 = 181.6).     

Design,synthesis, assessment,and molecular docking of novel pyrrolopyrimidine (7-deazapurine) derivatives as non-nucleoside hepatitis C virus NS5B polymerase inhibitors

Hepatitis C virus (HCV) infection is highly persistent and presents an unmet medical need requiring more effective treatment options. This has spurred intensive efforts to discover novel anti-HCV agents. The RNA-dependent RNA polymerase (RdRp), NS5B of HCV, constitutes a selective target for drug discovery due to its absence in human cells; also, it is the centerpiece for viral replication. Here, we synthesized novel pyrrole, pyrrolo[2,3-d]pyrimidine and pyrrolo[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine derivatives. The non-toxic doses of these compounds on Huh 7.5 cell line were determined and their antiviral activity against HCVcc genotype 4a was examined. Compounds 7j, 7f, 5c, 12i and 12f showed significant anti HCV activity. The percent of reduction for the non-toxic doses of 7j, 7f, 5c, 12i and 12f were 90%, 76.7 ± 5.8%, 73.3 ± 5.8%, 70% and 63.3 ± 5.8%, respectively. The activity of these compounds was interpreted by molecular docking against HCV NS5B polymerase enzyme.     

Three new flavonoid glycosides from the aerial parts of Graptophyllum grandulosum Turril (Acanthaceae)

Grandulosides A-C, three new flavonoid glycosides, were isolated from the aerial parts of Graptophyllum grandulosum Turill and identified as chrysoeriol-7-O-β-d-apiofuranosyl-(1 → 2)-β-d-xylopyranoside (1), chrysoeriol-7-O-[4′′′-O-acetyl-β-d-apiofuranosyl-(1 → 2)]-β-d-xylopyranoside (2) and 7-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-(4′′-Sodium hydrogeno sulfate) glucopyranoside (3). Four known compounds, chrysoeriol-7-O-β-d-xyloside (4), isorhamnetin-3-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside (5), luteolin-7-O-β-d-apiofuranosyl-(1 → 2)-β-d-xylopyranoside (6) and sucrose (7) were also obtained. The structures of these compounds were established by interpretation of their spectral data, mainly HR-TOFESIMS, 1D-NMR (¹H, ¹³C) and 2D-NMR (COSY, NOESY, HSQC and HMBC) and by comparison with the literature data.     

Design,synthesis, and SAR study of 3-(benzo[d][1,3]dioxol-5-yl)-N-benzylpropanamide as novel potent synergists against fluconazole-resistant Candida albicans

Based on our previous discovery and SAR study on the lead compounds 7d, 5 and berberine which can significantly enhance the susceptibility of fluconazole against fluconazole-resistant Candida albicans, a series of 3-(benzo[d][1,3]dioxol-5-yl)-N-(substituted benzyl)propanamides were designed, synthesized, and evaluated for their in vitro synergistic activity in combination with fluconazole. The series 2a–f were designed by replacing the amide moiety of the lead compound 7d with retro-amide moiety, and compounds 2a and 2b showed more activity than the lead 7d. Furthermore, introducing biphenyl moiety into series 2d–f afforded series 3a–r, most of which exhibited significantly superior activity to the series 2d–f. Especially, compound 3e, at a concentration of 1.0 µg/ml, can enhance the susceptibility of fluconazole against fluconazole-resistant Candida albicans from 128.0 µg/ml to 0.125–0.25 µg/ml. A clear SAR of the compounds is discussed.     

Phenylethanoid glycosides from the leaves of Magnolia hodgsonii

Three new phenylethanoid glycosides, 2-(3-hydroxy-4-methoxyphenyl)ethyl 1-O-β-d-allopyranoside (hodgsonialloside A, 1), 2-(3-hydroxy-4-methoxyphenyl)ethyl 1-O-β-d-glucopyranosyl-(1 → 4)-β-d-allopyranoside (hodgsonialloside B, 2) and 2-(3-methoxy-4-hydroxyphenyl)ethyl 1-O-β-d-allopyranoside (hodgsonialloside C, 3) were isolated from the leaves of Magnolia hodgsonii in addition to six known compounds, tyrosol 4-O-β-d-xylopyranosyl-(1 → 6)-β-d-glucopyranoside (4), kaempferol 3-O-neohesperidoside (5), kaempferol 3-O-rutinoside (6), kaempferol 3-O-α-l-rhamnopyranosyl-(1 → 2)-[α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranoside (7), (+)-syringaresinol O-β-d-glucopyranoside (8), and oblongionoside C (9). The structure elucidation of these compounds was based on analyses of physical and spectroscopic data including 1D and 2D NMR experiments.     

Small molecule fusion inhibitors: Design,synthesis and biological evaluation of (Z)-3-(5-(3-benzyl-4-oxo-2-thioxothiazolidinylidene)methyl)-N-(3-carboxy-4-hydroxy)phenyl-2,5-dimethylpyrroles and related derivatives targeting HIV-1 gp41

By a scaffold elongation strategy, a series of (Z)-3-(5-(3-benzyl-4-oxo-2-thioxothiazolidinylidene)methyl)-N-(3-carboxy-4-hydroxy)phenyl-2,5-dimethylpyrroles and related derivatives with a linear multi-aromatic-ring skeleton were designed, synthesized, and evaluated in HIV-1 gp41 and cellular assays. Among them, the most active compounds, 12e, 12g, and 12k with a one-carbon linker (n = 1) between the rhodanine (C) and phenyl (D) rings, exhibited very promising inhibitory potency with IC₅₀ values of 1.8–2.6 μM and EC₅₀ values of 0.3–1.5 μM against gp41 6-HB formation and HIV-1 replication in MT-2 cells, respectively. Additionally, they were almost equally effective against both T20-sensitive and resistant strains. The related SAR studies and molecular modeling results provided potential for further developing a new class of non-peptide small molecular fusion inhibitors targeting the HIV-1 gp41.     

Gynostemosides A–E,megastigmane glycosides from Gynostemma pentaphyllum

Megastigmane glycosides (1–5) together with seven (6–12) related known compounds were isolated from the whole plants of Gynostemma pentaphyllum. The structures were elucidated by means of spectroscopic methods, including 2D NMR, HR-ESIMS, and circular dichroism (CD), as well as chemical transformations to be (3R, 4R, 5S, 6S, 7E)-3,4,6-trihydroxymegastigmane-7-en-9-one-3-O-β-d-glucopyranoside (gynostemoside A, 1), (3S, 4S, 5R, 6R, 7E, 9R)-3,4,6,9-tetrahydroxymegastigmane-7-en-3-O-β-d-glucopyranoside (gynostemoside B, 2), (3S, 4S, 5S, 6S, 7E, 9R)-3,4,9-trihydroxymegastigmane-7-en-9-O-β-d-glucopyranoside (gynostemoside C, 3), (3S, 4S, 5S, 6S, 7E, 9R)-3,4,9-trihydroxymegastigmane-7-en-3-O-β-d-glucopyranoside (gynostemoside D, 4), and (3S, 4S, 5S, 6S, 7E, 9R)-3,4,9-trihydroxymegastigmane-7-en-4-O-β-d-glucopyranoside (gynostemoside E, 5), respectively.     

New cytotoxic dihydrochalcone and steroidal saponins from the aerial parts of Sansevieria cylindrica Bojer ex Hook

A new dihydrochalcone, 2‘,4‘-dihydroxy-3‘-methoxy-3,4-methylenedioxy-8-hydroxymethylene dihydrochalcone 1 and two new steroidal saponins, (25S)-ruscogenin-1-O-α-l-rhamnopyranosyl-(1 → 2)-β-d-glucopyranoside 2, (25S)-ruscogenin-3-O-α-l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranoside 3, together with three known steroidal saponins (25S)-ruscogenin-3-O-β-d-glucopyranoside 4, (25S)-ruscogenin-1-O-α-l-rhamnopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 3)]-α-l-arabinopyranoside 5 and (25R)-26-O-β-d-glucopyranosyl-furost-5-ene-1β,3β,22α,26-tetrol-1-O-α-L-rhamnopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 3)]-α-l-arabinopyranoside 6 were isolated from the aerial parts of Sansevieria cylindrica. The structures of the new compounds were established by UV, IR, EI-MS, HR-ESI–MS as well as 1D (¹H,¹³C and DEPT-135) and 2D (HSQC, HMBC and TOCSY) NMR spectral analysis. The isolated compounds 1-6 were assayed for in vitro cytotoxicities against the three human tumor cell lines HT116, MCF7 and HepG2. Compound 1 showed a moderate cytotoxicity against MCF7. Compounds 2, 3 and 6 exhibited moderate cytotoxicities against the three used cell lines and compound 5 showed marked cytotoxicities against all used cell lines.     

Synthesis and SAR of derivatives based on 2-biarylethylimidazole as bombesin receptor subtype-3 (BRS-3) agonists for the treatment of obesity

This Letter describes a series of potent and selective BRS-3 agonists containing a biarylethylimidazole pharmacophore. Extensive SAR studies were carried out with different aryl substitutions. This work led to the identification of a compound 2-{2-[4-(pyridin-2-yl)phenyl]ethyl}-5-(2,2-dimethylbutyl)-1H-imidazole 9 with excellent binding affinity (IC₅₀ = 18 nM, hBRS-3) and functional agonist activity (EC₅₀ = 47 nM, 99% activation). After oral administration, compound 9 had sufficient exposure in diet induced obese mice to demonstrate efficacy in lowering food intake and body weight via BRS-3 activation.