Investigation of acyclic uridine amide and 5′-amido nucleoside analogues as potential inhibitors of the Plasmodium falciparum dUTPase

Previously we have shown that trityl and diphenyl deoxyuridine derivatives and their acyclic analogues can inhibit Plasmodium falciparum dUTPase (PfdUTPase). We report the synthesis of conformationally restrained amide derivatives as inhibitors PfdUTPase, including both acyclic and cyclic examples. Activity was dependent on the orientation and location of the amide constraining group. In the case of the acyclic series, we were able to obtain amide-constrained analogues which showed similar or greater potency than the unconstrained analogues. Unfortunately these compounds showed lower selectivity in cellular assays.     

The synthesis and evaluation of thymoquinone analogues as anti-ovarian cancer and antimalarial agents

Thymoquinone (TQ), 2-isopropyl-5-methyl-1,4-benzoquinone, a natural product isolated from Nigella sativa L., has previously been demonstrated to exhibit antiproliferative activity in vitro against a range of cancers as well as the human malarial parasite Plasmodium falciparum. We describe here the synthesis of a series of analogues of TQ that explore the potential for nitrogen-substitution to this scaffold, or reduction to a hydroquinone scaffold, in increasing the potency of this antiproliferative activity against ovarian cancer cell lines and P. falciparum. In addition, alkyl or halogen-substituted analogues were commercially sourced and tested in parallel. Several TQ analogues with improved potency against ovarian cancer cells and P. falciparum were found, although this increase is suggested to be moderate. Key aspects of the structure activity relationship that could be further explored are highlighted.     

N-Benzyl-1-heteroaryl-3-(trifluoromethyl)-1H-pyrazole-5-carboxamides as inhibitors of co-activator associated arginine methyltransferase 1 (CARM1)

A series of N-benzyl-1-heteroaryl-3-(trifluoromethyl)-1H-pyrazole-5-carboxamides targeting co-activator associated arginine methyltransferase 1 (CARM1) have been designed and synthesized. The potency of these inhibitors was influenced by the nature of the heteroaryl fragment with the thiophene analogues being superior to thiazole, pyridine, isoindoline and benzofuran based inhibitors.     

Synthesis of cembranoid analogues and evaluation of their potential as quorum sensing inhibitors

Natural cembranoids have shown Quorum Sensing Inhibitory (QSI) activity, but their structure–function interactions are not well understood. Thirty-four cembranoid analogues were synthesized using six natural cembranoids (1–6) previously isolated from the Colombian Caribbean octocorals Eunicea knighti and Pseudoplexaura flagellosa as lead compounds. The analogues (7–40) obtained through the selected chemical transformations were tested in vitro against the QS systems of a Chromobacterium violaceum biosensor. Half of the cembranoid analogues assayed showed superior QSI activity to the lead compounds; three (8, 13, and 18) displayed remarkable potency up to three times higher than the natural compounds. Thereby, we have synthesized a pool of cembranoid QS inhibitors that can be used in concert with natural compounds to develop antipathogenic drugs and antifouling agents.     

Synthesis and biological evaluation of tricyclic anilinopyrimidines as IKKβ inhibitors

A series of tricyclic anilinopyrimidines were synthesized and evaluated as IKKβ inhibitors. Several analogues, including tricyclic phenyl (10, 18a, 18c, 18d, and 18j) and thienyl (26 and 28) derivatives were shown to have good in vitro enzyme potency and excellent cellular activity. Pharmaceutical profiling of a select group of tricyclic compounds compared to the non-tricyclic analogues suggested that in some cases, the improved cellular activity may be due to increased clog P and permeability.     

Discovery of aminocyclohexene analogues as selective and orally bioavailable hNav1.7 inhibitors for analgesia

hNav1.7 receives a lot of attention owing to its attractive mechanism of action in pain processing pathway. We have previously reported our design of a novel series of tetrahydropyridine analogues towards hNav1.7 selective inhibitors. Herein, we disclose further efforts to the optimization of hit compound (?)-6, which led to the identification of aminocyclohexene analogues (?)-9 and (?)-17 with good potency, high selectivity, and minimal CYP inhibition. Both compounds (?)-9 and (?)-17 demonstrated improved pharmacokinetic profiles in rats, and robust efficacy in rat formalin-induced nociception and spinal nerve ligation (SNL) models.     

Antitumor complexes of platinum with carrier molecules. 2 [1]. Mixed complexes of amino acids and tert-butylamine

In the search for a fine modulation of cisplatin analogues we have synthesized complexes with two different inert ligands bound to platinum in the cis- position. This paper reports on compounds of formula cis-[PtCl₂(aaH)(tba)] (aaH, amino acid; tba, tert-butylamine). These complexes have been synthesized with the aim of obtaining liposoluble cisplatin analogues bound to natural carrier groups. The derivatives of glycine, D-alanine, L-threonine, and L-serine were found to be moderately active against murine P388 and L1210 leukemia models. The compound K[PtCl₃(tba)] was also found to be active against the same tumor models. Their activity and potency was, however, much lower than that of cisplatin.     

Discovery of novel thieno[2,3-d]pyrimidin-4-yl hydrazone-based inhibitors of Cyclin D1-CDK4: Synthesis,biological evaluation,and structure–activity relationships

The synthesis and evaluation of new analogues of thieno[2,3-d]pyrimidin-4-yl hydrazones are described. 2-Pyrdinecarboxaldehyde [6-(tert-butyl)thieno[2,3-d]pyrimidine-4-yl]hydrazone derivatives have been identified as cyclin-dependent kinase 4 (CDK4) inhibitors. The potency, selectivity profile, and structure–activity relationship of this series of compounds are discussed.     

Synthesis and biological evaluation of 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]-4-ethynylimidazole. A novel and highly potent anti-inflammatory and cytoprotective agent

To explore more potent N-acylimidazole analogues of CDDO than CDDO-Im, which is one of the most potent compounds in several widely used bioassays related to protection against inflammation and carcinogenesis; we have synthesized and evaluated five new N-acyl(acetylenic)imidazole analogues. Among them, 4-ethynylimidazole 4 is nearly equivalent to CDDO-Im in potency in these bioassays. Remarkably, the solid form of 4 is more stable than that of CDDO-Im. These findings suggest that 4 is a very promising anti-inflammatory and cytoprotective agent and its further preclinical evaluation is warranted.     

Intermolecular interaction of voriconazole analogues with model membrane by DSC and NMR,and their antifungal activity using NMR based metabolic profiling

The development of novel antifungal agents with high susceptibility and increased potency can be achieved by increasing their overall lipophilicity. To enhance the lipophilicity of voriconazole, a second generation azole antifungal agent, we have synthesized its carboxylic acid ester analogues, namely p-methoxybenzoate (Vpmb), toluate (Vtol), benzoate (Vbz) and p-nitrobenzoate (Vpnb). The intermolecular interactions of these analogues with model membrane have been investigated using nuclear magnetic resonance (NMR) and differential scanning calorimetric (DSC) techniques. The results indicate varying degree of changes in the membrane bilayer’s structural architecture and physico-chemical characteristics which possibly can be correlated with the antifungal effects via fungal membrane. Rapid metabolite profiling of chemical entities using cell preparations is one of the most important steps in drug discovery. We have evaluated the effect of synthesized analogues on Candida albicans. The method involves real time ¹H NMR measurement of intact cells monitoring NMR signals from fungal metabolites which gives Metabolic End Point (MEP). This is then compared with Minimum Inhibitory Concentration (MIC) determined using conventional methods. Results indicate that one of the synthesized analogues, Vpmb shows reasonably good activity.     

7β-Methyl substituent is a structural locus associated with activity cliff for nepenthone analogues

With the purpose of identifying novel selective κ opioid receptor (KOR) antagonists as potential antidepressants from nepenthone analogues, starting from N-nor-N-cyclopropylmethyl-nepenthone (SLL-020ACP), a highly selective and potent KOR agonist, a series of 7β-methyl-nepenthone analogues was conceived, synthesized and assayed on opioid receptors based on the concept of hybridization. According to the pharmacological results, the functional reversal observed in orvinol analogues by introduction of 7β-methyl substituent could not be reproduced in nepenthone analogues. Alternatively, introduction of 7β-methyl substituent was associated with substantial loss of both subtype selectivity and potency but not efficacy for nepenthone analogues, which was not found in 7β-methyl orvinol analogues. Surprisingly, SLL-603, a 7β-methyl analogue of SLL-020ACP, was identified to be a KOR full agonist. The possible molecular mechanism for the heterogeneity in activity cliff was also investigated. In conclusion, 7β-methyl substituent was a structural locus associated with activity cliff and demonstrated as a pharmacological heterogeneity between nepenthone and orvinol analogues that warrants further investigations.     

Cyclic biphalin analogues with a novel linker lead to potent agonist activities at mu,delta, and kappa opioid receptors

In an effort to improve biphalin’s potency and efficacy at the µ-(MOR) and δ-opioid receptors (DOR), a series of cyclic biphalin analogues 1–5 with a cystamine or piperazine linker at the C-terminus were designed and synthesized by solution phase synthesis using Boc-chemistry. Interestingly, all of the analogues showed balanced opioid agonist activities at all opioid receptor subtypes due to enhanced κ-opioid receptor (KOR) activity. Our results indicate that C-terminal flexible linkers play an important role in KOR activity compared to that of the other cyclic biphalin analogues with a hydrazine linker. Among them, analogue 5 is a potent (Ki?=?0.27, 0.46, and 0.87?nM; EC₅₀?=?3.47, 1.45, and 13.5?nM at MOR, DOR, and KOR, respectively) opioid agonist with high efficacy. Based on the high potency and efficacy at the three opioid receptor subtypes, the ligand is expected to have a potential synergistic effect on relieving pain and further studies including in vivo tests are worthwhile.     

Quinolidene based monocarbonyl curcumin analogues as promising antimycobacterial agents: Synthesis and molecular docking study

A series of quinoline incorporated monocarbonyl curcumin analogues was efficiently synthesized using [HDBU][HSO₄] as catalyst via Knoevenagel type condensation and evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H37Ra (MTB) and Mycobacterium bovis BCG in dormant state. The analogues 3e, 3h, 4a and 4e exhibited very good antitubercular activity. The antiproliferative activity of the analogues against MCF-7, A549 and HCT-116 cell lines was evaluated using modified MTT assay and these compounds were found to be non-cytotoxic. Molecular docking study has been carried out against M. tuberculosis pantothenate synthetase (MTB PS) enzyme in an effort to enhance the understanding of their action as antitubercular agents. The potency, low cytotoxicity and selectivity of these analogues support them as valid leads for further optimization.     

Examination of halogen substituent effects on HIV-1 integrase inhibitors derived from 2,3-dihydro-6,7-dihydroxy-1H-isoindol-1-ones and 4,5-dihydroxy-1H-isoindole-1,3(2H)-diones

Using 2,3-dihydro-6,7-dihydroxy-1H-isoindol-1-one and 4,5-dihydroxy-1H-isoindole-1,3(2H)-dione based HIV-1 integrase inhibitors as display platforms, we undertook a thorough examination of the effects of modifying the halogen substituents on a key benzyl ring that is hypothesized to bind in a hydrophobic pocket of the integrase·DNA complex. Data from this study suggest that in general dihalo-substituted analogues have higher potency than monohalo-substituted compounds, but that further addition of halogens is not beneficial.     

Synthesis,Antitubercular Activity and Mechanism of Resistance of Highly Effective Thiacetazone Analogues

Defining the pharmacological target(s) of currently used drugs and developing new analogues with greater potency are both important aspects of the search for agents that are effective against drug-sensitive and drug-resistant Mycobacterium tuberculosis. Thiacetazone (TAC) is an anti-tubercular drug that was formerly used in conjunction with isoniazid, but removed from the antitubercular chemotherapeutic arsenal due to toxic side effects. However, several recent studies have linked the mechanisms of action of TAC to mycolic acid metabolism and TAC-derived analogues have shown increased potency against M. tuberculosis. To obtain new insights into the molecular mechanisms of TAC resistance, we isolated and analyzed 10 mutants of M. tuberculosis that were highly resistant to TAC. One strain was found to be mutated in the methyltransferase MmaA4 at Gly101, consistent with its lack of oxygenated mycolic acids. All remaining strains harbored missense mutations in either HadA (at Cys61) or HadC (at Val85, Lys157 or Thr123), which are components of the β-hydroxyacyl-ACP dehydratase complex that participates in the mycolic acid elongation step. Separately, a library of 31 new TAC analogues was synthesized and evaluated against M. tuberculosis. Two of these compounds, 15 and 16, exhibited minimal inhibitory concentrations 10-fold lower than the parental molecule, and inhibited mycolic acid biosynthesis in a dose-dependent manner. Moreover, overexpression of HadAB HadBC or HadABC in M. tuberculosis led to high level resistance to these compounds, demonstrating that their mode of action is similar to that of TAC. In summary, this study uncovered new mutations associated with TAC resistance and also demonstrated that simple structural optimization of the TAC scaffold was possible and may lead to a new generation of TAC-derived drug candidates for the potential treatment of tuberculosis as mycolic acid inhibitors.     

Identification of purinoceptors in the isolated stomach and intestine of the three-spined stickleback Gasterosteus aculeatus L.

1. Adenine nucleosides and nucleotides were examined for pharmacological activity in isolated stomach and intestine from the stickleback Gasterosteus aculeatus L.2. Adenosine and its stable analogues all concentration-dependently relaxed carbachol-contracted stomach and intestine, with no significant difference in the potency of the analogues. Only 8-(p-sulphophenyl) theophylline inhibited the relaxant response to adenosine in both tissues; other adenosine antagonists such as 1,3-dipropyl-8-cyclopentylxanthine were not active.3. ATP, α, β-methylene ATP (α,β-MeATP) and 2-methylthio ATP (2-MeSATP) all caused concen- tration-dependent contractions of the stomach and intestine.4. In the stomach, the order of potency was 2-MeSATP >α, β-MeATP = ATP; the P_2γ-purinoceptor antagonist reactive blue 2 inhibited responses to ATP.5. In the intestine, the order of potency was α,β-MeATP > 2-MeSATP = ATP; reactive blue 2 did not affect responses to ATP, nor did prolonged incubation with α,β-MeATP.6. It is concluded that in both the stomach and intestine, adenosine is acting through a non-specific or undifferentiated P₁-purinoceptor. In the stomach, however, the P₂-purinoceptor appears to be analogous to the mammalian P_2γ-purinoceptor, and in the intestine, the receptor is more similar to the mammalian P_2x-subtype, although it was not susceptible to desensitization.     

Modification of the N-terminal sulfonyl residue in 3-amidinophenylalanine-based matriptase inhibitors

Replacement of the N-terminal β-alanyl-amide moiety in previously identified matriptase inhibitors by non-charged aryl groups caused a slightly decreased potency and partially reduced selectivity, especially towards thrombin. However, some of these analogues are still potent matriptase inhibitors with K_i-values <10 nM. In contrast, improved activity was observed for newly designed tribasic analogues, especially for compound 21, which inhibits matriptase with an K_i-value of 80 pM.     

Enhanced bioactivity of silybin B methylation products

Flavonolignans from milk thistle (Silybum marianum) have been investigated for their cellular modulatory properties, including cancer chemoprevention and hepatoprotection, as an extract (silymarin), as partially purified mixtures (silibinin and isosilibinin), and as pure compounds (a series of seven isomers). One challenge with the use of these compounds in vivo is their relatively short half-life due to conjugation, particularly glucuronidation. In an attempt to generate analogues with improved in vivo properties, particularly reduced metabolic liability, a semi-synthetic series was prepared in which the hydroxy groups of silybin B were alkylated. A total of five methylated analogues of silybin B were synthesized using standard alkylation conditions (dimethyl sulfate and potassium carbonate in acetone), purified using preparative HPLC, and elucidated via spectroscopy and spectrometry. Of the five, one was monomethylated (3), one was dimethylated (4), two were trimethylated (2 and 6), and one was tetramethylated (5). The relative potency of all compounds was determined in a 72 h growth-inhibition assay against a panel of three prostate cancer cell lines (DU-145, PC-3, and LNCaP) and a human hepatoma cell line (Huh7.5.1) and compared to natural silybin B. Compounds also were evaluated for inhibition of both cytochrome P450 2C9 (CYP2C9) activity in human liver microsomes and hepatitis C virus infection in Huh7.5.1 cells. The monomethyl and dimethyl analogues were shown to have enhanced activity in terms of cytotoxicity, CYP2C9 inhibitory potency, and antiviral activity (up to 6-fold increased potency) compared to the parent compound, silybin B. In total, these data suggested that methylation of flavonolignans can increase bioactivity.     

Elaboration of a proprietary thymidylate kinase inhibitor motif towards anti-tuberculosis agents

We report the design and synthesis of a series of non-nucleoside MtbTMPK inhibitors (1–14) based on the gram-positive bacterial TMPK inhibitor hit compound 1. A practical synthesis was developed to access these analogues. Several compounds show promising MtbTMPK inhibitory potency and allow the establishment of a structure–activity relationship, which is helpful for further optimization.     

Structure-Guided Design of Selective Epac1 and Epac2 Agonists

The second messenger cAMP is known to augment glucose-induced insulin secretion. However, its downstream targets in pancreatic β-cells have not been unequivocally determined. Therefore, we designed cAMP analogues by a structure-guided approach that act as Epac2-selective agonists both in vitro and in vivo. These analogues activate Epac2 about two orders of magnitude more potently than cAMP. The high potency arises from increased affinity as well as increased maximal activation. Crystallographic studies demonstrate that this is due to unique interactions. At least one of the Epac2-specific agonists, Sp-8-BnT-cAMPS (S-220), enhances glucose-induced insulin secretion in human pancreatic cells. Selective targeting of Epac2 is thus proven possible and may be an option in diabetes treatment.