Anti-HIV protease triterpenoids from the acid hydrolysate of Panax ginseng

Three artificial triterpenoids, (20R)-20,25-epoxy-dammaran-2-en-6α,12β-diol (1), (20R)-20,25-epoxy-3-methyl-28-nordammaran-2-en-6α,12β-diol (2) and isodehydroprotopanaxatriol (3), were isolated from an acidic hydrolysate of Panax ginseng C.A. Meyer, along with three known triterpenes, (20R)-panaxadiol (4), (20R)-panaxatriol (5) and oleanolic acid (6). Compounds 1–3 and 6 showed inhibitory activity against HIV-1 protease with IC₅₀ of 10.5, 10.3, 12.3 and 6.3 μM, respectively. The results indicated that acid treatment of Ginseng extract could produce diverse structures with interesting bioactivity.     

Design and synthesis of HIV-1 protease inhibitors for a long-acting injectable drug application

The design and synthesis of novel HIV-1 protease inhibitors (PIs) (1–22), which display high potency against HIV-1 wild-type and multi-PI-resistant HIV-mutant clinical isolates, is described. Lead optimization was initiated from compound 1, a Phe–Phe hydroxyethylene peptidomimetic PI, and was directed towards the discovery of new PIs suitable for a long-acting (LA) injectable drug application. Introducing a heterocyclic 6-methoxy-3-pyridinyl or a 6-(dimethylamino)-3-pyridinyl moiety (R³) at the para-position of the P1′ benzyl fragment generated compounds with antiviral potency in the low single digit nanomolar range. Halogenation or alkylation of the metabolic hot spots on the various aromatic rings resulted in PIs with high stability against degradation in human liver microsomes and low plasma clearance in rats. Replacing the chromanolamine moiety (R¹) in the P2 protease binding site by a cyclopentanolamine or a cyclohexanolamine derivative provided a series of high clearance PIs (16–22) with EC₅₀s on wild-type HIV-1 in the range of 0.8–1.8 nM. PIs 18 and 22, formulated as nanosuspensions, showed gradual but sustained and complete release from the injection site over two months in rats, and were therefore identified as interesting candidates for a LA injectable drug application for treating HIV/AIDS.     

Evaluation of an octahydroisochromene scaffold used as a novel SARS 3CL protease inhibitor

An octahydroisochromene scaffold has been introduced into a known SARS 3CL protease inhibitor as a novel hydrophobic core to interact with the S2 pocket of the protease. An alkyl or aryl substituent was also introduced at the 1-position of the octahydroisochromene scaffold and expected to introduce additional interactions with the protease. Sharpless–Katsuki asymmetric epoxidation and Sharpless asymmetric dihydroxylation were employed to construct the octahydroisochromene scaffold. The introductions of the P1 site His-al and the substituent at 1-position was achieved using successive reductive amination reactions. Our initial evaluations of the diastereo-isomeric mixtures (16a–d) revealed that the octahydroisochromene moiety functions as a core hydrophobic scaffold for the S2 pocket of the protease and the substituent at the 1-position may form additional interactions with the protease. The inhibitory activities of the diastereoisomerically-pure inhibitors (3a–d) strongly suggest that a specific stereo-isomer of the octahydroisochromene scaffold, (1S, 3S) 3b, directs the P1 site imidazole, the warhead aldehyde, and substituent at the 1-position of the fused ring to their appropriate pockets in the protease.     

The mononuclear–dinuclear dance: Twisting the backbone in metalloligands operates a coordination switch

The copper(II) complex [Cu{(R,R)-1}] in which (R)-H₂1 is 1,6-bis(3-ethoxy-2-hydroxyphenyl)-(3R,4R)-(?)-cyclohexane-1,2-diyl-2,5-diazahexa-1,5-diene possesses an O₄-donor cavity that can bind Pb²⁺, Cd²⁺ and Eu³⁺. The single crystal structures of [Cu(OH₂){(R,R)-1}Pb(ONO₂)₂], {[Cu{(R,R)-1}Cd(ONO₂)(OH₂)₂][NO₃]^.MeOH}^.[Cu{(R,R)-1}] and [Cu{(R,R)-1}Eu(O₂NO)₃] are presented. The co-crystallization of [Cu{(R,R)-1}Cd(ONO₂)(OH₂)₂][NO₃] and [Cu{(R,R)-1}] appears to be driven by hydrogen-bonded host–guest interactions between each axial water ligand in [Cu{(R,R)-1}Cd(ONO₂)(OH₂)₂]⁺ with the O₄-domain of [Cu{(R,R)-1}]. When the ligand scaffold is changed from cyclohexane-1,2-diyl to 1,1′-binaphthyl to give (R)-H₂2, the N₂O₂-cavity is unable to bind copper(II) in its preferred square planar environment. The single crystal structure of [Zn{(R)-2}] confirms the presence of tetrahedral zinc(II). As a result, the spatial properties of the ethoxy arms in [Zn{(R)-2}] and [Cu{(R)-2}] are not suited to the facile formation of dimetallic complexes.     

Umbelliferone derivatives exert neuroprotective effects by inhibiting monoamine oxidase A,self-amyloidβ aggregation,and lipid peroxidation

Umbelliferone has been demonstrated to have a wide range of biological activities. However, the effect of incorporating a formyl moiety in the umbelliferone scaffold has not been investigated. In this paper, we investigated the inhibitory activity of six coumarins, namely umbelliferone (1), 6-formyl umbelliferone (2), 8-formyl umbelliferone (3), umbelliferone-6-carboxylic acid (4), esculetin (5), and scopoletin (6) against human monoamine oxidases (hMAOs), self-amyloid β (Aβ) aggregation, and lipid peroxidation. We found that all compounds had high selectivity for hMAO-A in comparison with hMAO-B. Among the compounds, 2 exhibited the highest hMAO inhibitory activity with an IC₅₀ value of 3.23 µM for hMAO-A and 15.31 µM for hMAO-B. Enzyme kinetic analysis showed that 2 and 3 were competitive hMAO inhibitors. In silico hydrated molecular docking simulations revealed that the coumarins interacted with substrate-binding site residues of the enzymes and the isoalloxazine ring of FAD. In addition, formyl coumarins 2 and 3 significantly inhibited lipid peroxidation in rat brain homogenates and self-Aβ_25-35 aggregation compared to other derivatives. These represent the first experimental and modelling data for hMAO-A/B inhibition by umbelliferone derivatives. Together, the data suggest that introduction of a formyl moiety in the 7-hydroxycoumarin scaffold, especially at the 6 position, plays an important role in the inhibition of hMAOs, Aβ self-aggregation, and lipid peroxidation. Umbelliferone derivative 2 is a promising therapeutic lead scaffold for developing anti-neuropsychiatric disorder drugs that function via selective hMAO-A inhibition.     

Synthesis and biological evaluation of 2-amino-5-aryl-3-benzylthiopyridine scaffold based potent c-Met inhibitors

A series of 2-amino-N-benzylpyridine-3-carboxnamides, 2-amino-N-benzylpyridine-3-sulfonamides and 2-amino-3-benzylthiopyridines against c-Met were designed by means of bioisosteric replacement and docking analysis. Optimization of the 2-amino-3-benzylthiopyridine scaffold led to the identification of compound (R)-10b displaying c-Met inhibition with an IC₅₀ up to 7.7 nM. In the cytotoxic evaluation, compound (R)-10b effectively inhibited the proliferation of c-Met addictive human cancer cell lines (IC₅₀ from 0.19 to 0.71 μM) and c-Met activation-mediated cell metastasis. At a dose of 100 mg/Kg, (R)-10b evidently inhibited tumor growth (45%) in NIH-3T3/TPR-Met xenograft model. Of note, (R)-10b could overcome c-Met-activation mediated gefitinib-resistance, which indicated its potential use for drug combination. Taken together, 2-amino-3-benzylthiopyridine scaffold was first disclosed and exhibited promising pharmacological profiles against c-Met, which left room for further exploration.     

Anti-AIDS agents 84. Synthesis and anti-human immunodeficiency virus (HIV) activity of 2′-monomethyl-4-methyl- and 1′-thia-4-methyl-(3′R,4′R)-3′,4′-di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) analogs

In a continuing investigation into the pharmacophores and structure–activity relationship (SAR) of (3′R,4′R)-3′,4′-di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) as a potent anti-HIV agent, 2′-monomethyl substituted 1′-oxa, 1′-thia, 1′-sulfoxide, and 1′-sulfone analogs were synthesized and evaluated for inhibition of HIV-1 replication in H9 lymphocytes. Among them, 2′S-monomethyl-4-methyl DCK (5a)³ and 2′S-monomethyl-1′-thia-4-methyl DCK (7a) exhibited potent anti-HIV activity with EC₅₀ values of 40.2 and 39.1 nM and remarkable therapeutic indexes of 705 and 1000, respectively, which were better than those of the lead compound DCK in the same assay. In contrast, the corresponding isomeric 2′R-monomethyl-4-methyl DCK (6) and 2′R-monomethyl-1′-thia-4-methyl DCK (8) showed much weaker inhibitory activity against HIV-1 replication. Therefore, the bioassay results suggest that the spatial orientation of the 2′-methyl group in DCK analogs can have important effects on anti-HIV activity of this compound class.     

Synthesis of dammarane-type triterpene derivatives and their ability to inhibit HIV and HCV proteases

We synthesized dammarane-type triterpene derivatives and evaluated their ability to inhibit HIV-1 and HCV proteases to understand their structure–activity relationships. All of the mono- and di-succinyl derivatives (5a–5f) were powerful inhibitors of HIV-1 protease (IC₅₀ < 10 μM). However, only di-succinyl (5e) and 2,3-seco-2,3-dioic acid (3b) derivatives similarly inhibited HCV protease (IC₅₀ < 10 μM). A-nor dammarane-type triterpenes (4a and 4b, IC₅₀ 10.0 and 29.9 μM, respectively) inhibited HIV-1 protease moderately or strongly, but were inactive against HCV protease. All compounds that powerfully inhibited HIV-1 or HCV protease did not appreciably inhibit the general human proteases, renin and trypsin (IC₅₀ > 1000 μM). These findings indicated that the mono-succinyl dammarane type derivatives (5a–5d) selectively inhibited HIV-1 protease and that the di-succinyl (5e, 5f) as well as 2,3-seco-2,3-dioic acid (3b) derivatives preferably inhibited both viral proteases.     

Synthesis and antimalarial evaluation of a screening library based on a tetrahydroanthraquinone natural product scaffold

As part of a research program aimed at discovering new antimalarial leads from Australian macrofungi a unique fungi-derived prefractionated library was screened against a chloroquine-sensitive Plasmodium falciparum line (3D7) using a radiometric growth inhibition assay. A library fraction derived from a Cortinarius species displayed promising antimalarial activity. UV-guided fractionation on the CH₂Cl₂/MeOH extract from this fungus resulted in the isolation of four known compounds: (1S,3R)-austrocortirubin (1), (1S,3S)-austrocortirubin (2), 1-deoxyaustrocortirubin (3), and austrocortinin (4). Compound 2 was used as a natural product scaffold in the parallel solution-phase synthesis of a small library of N-substituted tetrahydroanthraquinones (5–15). All compounds (1–15) were tested in vitro against P. falciparum 3D7 parasites and (1S,3S)-austrocortirubin (2), the major fungal constituent, was shown to be the most active compound with an IC₅₀ of 1.9 μM. This compound displayed moderate cytotoxicity against neonatal foreskin fibroblast (NFF) cells with an IC₅₀ of 15.6 μM.     

Improving the catalytic efficiency of aldo-keto reductase KmAKR towards t-butyl 6-cyano-(3R,5R)-dihydroxyhexanoate via semi-rational design

t-Butyl 6-cyano-(3R,5R)-dihydroxyhexanoate ((3R,5R)-2) is an important chiral diol synthon of atorvastatin calcium. Previously, we constructed a variant KmAKR-W297H (M1) of Kluyveromyces marxianus aldo-keto reductase (KmAKR, designated as M0), possessing excellent diastereoselectivity but moderate activity towards t-butyl 6-cyano-(5R)-hydroxy-3-oxohexanoate ((5R)-1). In this work, KmAKR-W297H/Y296W/K29H (M3) was developed via semi-rational design. It exhibited much improved catalytic efficiency towards (5R)-1. The K_m values of M3 for NADPH and (5R)-1 were 0.15 mmol/L and 1.41 mmol/L, and the maximal reaction rate v_max was 55.56 μmol/min/mg. Compared with M1, the catalytic efficiency k_cat/K_m of M3 was increased 2.64-fold. Coupled with Exiguobacterium sibiricum glucose dehydrogenase (EsGDH) for nicotinamide adenine dinucleotide phosphate (NADPH) regeneration, M3 took 3.5 h to completely reduce (5R)-1 at up to 100.0 g/L, producing 237.4 mmol/L (3R,5R)-2 in d.e._P value above 99.5%. The space-time yield (STY) of M3-catalyzed (3R,5R)-2 synthesis was 372.8 g/L/d.     

Novel imidazoline compounds as partial or full agonists of D2-like dopamine receptors inspired by I2-imidazoline binding sites ligand 2-BFI

Based on the well known biological versatility of the imidazoline nucleus, we prepared the novel derivatives 3a–k inspired by 2-BFI scaffold to assess imidazoline molecules as D₂-like dopamine receptor ligands. Conservative chemical modifications of the lead structure, such as the introduction of an hydroxy group in the aromatic ring alone or associated with N-benzyl substitution, provided partial (3f) or nearly full (3e and 3h) agonists, all endowed with D₂-like potency comparable to that of dopamine.     

Design,synthesis and evaluation of 2,2-dimethyl-1,3-dioxolane derivatives as human rhinovirus 3C protease inhibitors

The human rhinovirus (HRV) is the most significant cause of the common cold all over the world. The maturation and replication of this virus entirely depend on the activity of a virus-encoded 3C protease. Due to the high conservation among different serotypes and the minimal homology existing between 3C protease and known mammalian enzymes, 3C protease has been regarded as an attractive target for the treatment of HRV infections. In this study, we identified a novel (4R,5R)-N⁴-(2-((3-methoxyphenyl)amino)ethyl)-2,2-dimethyl-N⁵-(naphthalen-2-yl)-1,3-dioxolane-4,5-dicarboxamide (7a) to be a HRV 3C protease inhibitor via virtual screening. Further research has been focused on the design, synthesis and in vitro biological evaluation of 7a derivatives. The studies revealed that compound 7d has an IC₅₀ value of 2.50 ± 0.7 µM against HRV 3C protease, and it thus could serve as a promising compound for the development of novel anti-rhinoviral medicines.     

Development of selective inhibitors for the treatment of rheumatoid arthritis: (R)-3-(3-(Methyl(7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)pyrrolidin-1-yl)-3-oxopropanenitrile as a JAK1-selective inhibitor

A series of 3(R)-aminopyrrolidine derivatives were designed and synthesized for JAK1-selective inhibitors through the modification of tofacitinib’s core structure, (3R,4R)-3-amino-4-methylpiperidine. From the new core structures, we selected (R)-N-methyl-N-(pyrrolidin-3-yl)-7H-pyrrolo[2,3-d]pyrimidin-4-amine as a scaffold for further SAR studies. From biochemical enzyme assays and liver microsomal stability tests, (R)-3-(3-(methyl(7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)pyrrolidin-1-yl)-3-oxopropanenitrile (6) was chosen for further in vivo test through oral administration. Compound 6 showed improved selectivity for JAK1 compared to that of tofacitinib (IC₅₀ 11, 2.4?×?10², 2.8?×?10³, and 1.1?×?10²?nM for JAK1, JAK2, JAK3, and TYK2, respectively). In CIA and AIA model tests, compound 6 exhibited similar efficacy to tofacitinib citrate.     

Synthesis and structure–activity relationships of novel,substituted 5,6-dihydrodibenzo[a,g]quinolizinium P2X7 antagonists

Iminium quaternary protoberberine alkaloids (QPA) have been found to be novel P2X₇ antagonists. To assess their structure–activity relationships, these compounds were modified at their R¹ and R² groups and assayed for their ability to inhibit the 2′(3′)-O-(4-benzoylbenzoyl)-ATP (BzATP)-induced uptake of fluorescent ethidium by HEK-293 cells stably expressing the human P2X₇ receptor, and their ability to inhibit BzATP-induced IL-1β release by differentiated THP-1 cells. Compounds 15a and 15d, with alkyl groups at the R¹ position, and especially compound 19h, with the 2-NO₂-4,5-dimethoxy-benzyl group at the R² position, had potent inhibitory efficacy as P2X₇ antagonists.     

Diamidato-bis(diphenylphosphino) platinum(II) complexes: Synthesis, characterization, and reactivity in the presence of acid

The reaction of Pt(COD)Cl₂, where COD is 1,5-cyclooctadiene, with one equivalent of a diamidato-bis(phosphino) Trost ligand ((R,R)-2 = N,N′-bis(2-diphenylphosphino-1-benzoyl)-(1R,2R)-1,2-diaminocyclohexane, (R,R)-3 = N,N′-bis(2-diphenylphosphino-1-naphthoyl)-(1R,2R)-1,2-diaminocyclohexane, or (±)-4 = N,N′-bis(2-diphenylphosphino-1-benzoyl)-1,2-bis(aminobenzene)) in the presence of base afforded square planar diamidato-bis(phosphino) platinum(II) complexes (R,R)-2-Pt, (R,R)-3-Pt, (±)-4-Pt. Characterization of all complexes included the solution and solid state structure determination of each complex based on multinuclear NMR and X-ray analyses, respectively. Stability of the complexes in acid was examined on addition of HCl to (R,R)-2-Pt in chloroform and compared to the unreactive nature of the similar diamidato-bis(phosphino) complex 1-Pt (1 = 1,2-bis-N-[2′-(diphenylphosphino)benzoyl]diamino-benzene) in the presence of acid. Protonation of the bound amidato nitrogen atoms of (R,R)-2-Pt was observed along with decoordination of the nitrogen atoms from the platinum(II) center producing (R,R)-2-PtCl₂ in quantitative yield by NMR analysis. Confirmation of the product was made on comparison of the NMR spectra to that of authentic (R,R)-2-PtCl₂ prepared on reaction of Pt(COD)Cl₂ with (R,R)-2 in CH₂Cl₂ and characterized by single-crystal X-ray diffraction analysis and NMR spectroscopy. Results add to the knowledge of rich coordination chemistry of bis(phosphino) ligands with late transition metals, metal-amidato chemistry, and has implications in catalysis.     

Development of novel adenosine receptor ligands based on the 3-amidocoumarin scaffold

With the aim of finding new adenosine receptor (AR) ligands presenting the 3-amidocoumarin scaffold, a study focusing on the discovery of new chemical entities was carried out. The synthesized compounds 1–8 were evaluated in radioligand binding (A₁, A_2A and A₃) and adenylyl cyclase activity (A_2B) assays in order to determine their affinity for human AR subtypes. The 3-benzamide derivative 4 showed the highest affinity of the whole series and was more than 30-fold selective for the A₃ AR (K_i = 3.24 μM). The current study supported that small structural changes in this scaffold allowed modulating the affinity resulting in novel promising classes of A₁, A_2A, and/or A₃ AR ligands. We also performed docking calculations in hA_2A and hA₃ to identify the hypothetical binding mode for the most active compounds. In addition, some ADME properties were calculated in order to better understand the potential of these compounds as drug candidates.     

Chemical modification-mediated optimisation of bronchodilatory activity of mepenzolate,a muscarinic receptor antagonist with anti-inflammatory activity

The treatment for patients with chronic obstructive pulmonary disease (COPD) usually involves a combination of anti-inflammatory and bronchodilatory drugs. We recently found that mepenzolate bromide (1) and its derivative, 3-(2-hydroxy-2, 2-diphenylacetoxy)-1-(3-phenoxypropyl)-1-azoniabicyclo[2.2.2]octane bromide (5), have both anti-inflammatory and bronchodilatory activities. We chemically modified 5 with a view to obtain derivatives with both anti-inflammatory and longer-lasting bronchodilatory activities. Among the synthesized compounds, (R)-(–)-12 ((R)-3-(2-hydroxy-2,2-diphenylacetoxy)-1-(3-phenylpropyl)-1-azoniabicyclo[2.2.2]octane bromide) showed the highest affinity in vitro for the human muscarinic M3 receptor (hM₃R). Compared to 1 and 5, (R)-(–)-12 exhibited longer-lasting bronchodilatory activity and equivalent anti-inflammatory effect in mice. The long-term intratracheal administration of (R)-(–)-12 suppressed porcine pancreatic elastase-induced pulmonary emphysema in mice, whereas the same procedure with a long-acting muscarinic antagonist used clinically (tiotropium bromide) did not. These results suggest that (R)-(–)-12 might be therapeutically beneficial for use with COPD patients given the improved effects seen against both inflammatory pulmonary emphysema and airflow limitation in this animal model.     

Design,synthesis and biological evaluation of HIV-1 protease inhibitors with morpholine derivatives as P2 ligands in combination with cyclopropyl as P1′ ligand

A series of novel HIV-1 protease inhibitors has been designed and synthesized, which contained morpholine derivatives as the P2 ligands and hydrophobic cyclopropyl as the P1′ ligand at the meantime in this study, with the aim of improving the interactions between the active sites of HIV-1 protease and the inhibitors. Twenty-eight compounds were synthesized and assessed, among which inhibitors m18 and m1 exhibited excellent inhibitory effect on the activity of HIV-1 protease with IC₅₀ value of 47 nM and 53 nM, respectively. The molecular modeling of m1 revealed possible hydrogen bondings or van der Waals between the inhibitor and the protease, worthy of in-depth study.     

Design,synthesis and biological evaluation of novel HIV-1 protease inhibitors with pentacyclic triterpenoids as P2-ligands

The design, synthesis and SAR study of a new series of HIV-1 protease inhibitors with pentacyclic triterpenoids as P2 ligands and phenylsulfonamide as P2′ ligands were discussed. These compounds exhibited micromolar inhibitory potency, among which compound T1c displayed HIV-1 protease inhibition with IC₅₀ values of 0.12?μM, which was 67 times the inhibitory activity of its raw material Ursolic acid (8.0?μM).