Designing Chromane Derivatives as α2A-Adrenoceptor Selective Agonists via Conformation Constraint.

Enhancing the selectivity of alpha2-adrenoceptor (α2A-AR) agonists remains an unresolved issue. Herein, we reported the design of an α2A-AR agonist using the conformation constraint method, beginning with medetomidine. The structure-activity relationship indicated that the 8-substituent of chromane derivatives exerted the most pronounced effect on α2A-AR agonistic activity. Compounds A9 and B9 were identified as the most promising, exhibiting EC50 values of 0.78 and 0.23 nM, respectively. Their selectivity indexes surpassed dexmedetomidine (DMED) by 10-80 fold. In vivo studies demonstrated that both A9 and B9 dose-dependently increased the loss of righting reflex in mice, with ED50 values of 1.54 and 0.138 mg/kg, respectively. Binding mode calculations and mutation studies suggested the indispensability of the hydrogen bond between ASP1283.32 and α2A-AR agonist. In particular, A9 and B9 showed no dual reverse pharmacological effect, a characteristic exhibited by DMED in α2A-AR activation.

Synthesis of 2,2-dimethyl-chroman-based stereochemically flexible and constrained anti-breast cancer agents.

Receptors are proteinous macromolecules which remain in the apo form under normal/unliganded conditions. As the ligand approaches, there are specific stereo-chemical changes in the apo form of the receptor as per the stereochemistry of a ligand. Accordingly, a series of substituted dimethyl-chroman-based stereochemically flexible and constrained Tamoxifen analogs were synthesized as anti-breast cancer agents. The synthesized compounds 19a-e, 20a-e, 21, and 22a-e, showed significant antiproliferative activity against estrogen receptor-positive (ER+, MCF-7) and negative (ER-, MDA MB-231) cells within IC50 value 8.5-25.0 µM. Amongst all, four potential molecules viz 19b, 19e, 22a, and 22c, were evaluated for their effect on the cell division cycle and apoptosis of ER+ and ER- cancer cells (MCF-7 & MDA MB-231cells), which showed that these compounds possessed antiproliferative activity through triggering apoptosis. In-silico docking experiments elucidated the possible affinity of compounds with estrogen receptors-α and -ß.

Synthesis of New Chroman-4-one Based 1,2,3-Triazole Analogues as Antioxidant and Anti-Inflammatory Agents.

A library of new chroman-4-one based 1,2,3-triazole analogues were synthesized involving a series of condensation, cyclization, Suzuki coupling and copper catalysed click chemistry protocols. The newly synthesized compounds 8a-l were screened for their invitro antioxidant and anti-inflammatory activities by employing Ascorbic acid and Diclofenac as reference drugs respectively. The compound without any substituent on benzyl ring (8a), compound with -Cl substituent in para position of benzyl ring (8i), and compound with ethoxy substituent in para position of benzyl ring (8k) exhibited potent antioxidant and anti-inflammatory activities with higher percentage of inhibition. To understand their binding affinities, molecular docking study of these three compounds performed against NADPH oxidase with presented outstanding docking scores and promising binding interactions like H-bond and hydrophobic.

Structure-activity and structure-property relationship studies of spirocyclic chromanes with antimalarial activity.

Malaria is a prevalent and lethal disease. The fast emergence and spread of resistance to current therapies is a major concern and the development of a novel line of therapy that could overcome, the problem of drug resistance, is imperative. Screening of a set of compounds with drug/natural product-based sub-structural motifs led to the identification of spirocyclic chroman-4-one 1 with promising antimalarial activity against the chloroquine-resistant Dd2 and chloroquine-sensitive 3D7 strains of the parasite. Extensive structure-activity and structure-property relationship studies were conducted to identify the essential features necessary for its activity and properties.

Design, Synthesis, and Bioactivity Evaluation of New Thiochromanone Derivatives Containing a Carboxamide Moiety.

In this study, using the botanical active component thiochromanone as the lead compound, a total of 32 new thiochromanone derivatives containing a carboxamide moiety were designed and synthesized and their in vitro antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas oryzae pv. oryzicolaby (Xoc), and Xanthomonas axonopodis pv. citri (Xac) were determined, as well as their in vitro antifungal activities against Botryosphaeria dothidea (B. dothidea), Phomopsis sp., and Botrytis cinerea (B. cinerea). Bioassay results demonstrated that some of the target compounds exhibited moderate to good in vitro antibacterial and antifungal activities. In particular, compound 4e revealed excellent in vitro antibacterial activity against Xoo, Xoc, and Xac, and its EC50 values of 15, 19, and 23 µg/mL, respectively, were superior to those of Bismerthiazol and Thiodiazole copper. Meanwhile, compound 3b revealed moderate in vitro antifungal activity against B. dothidea at 50 µg/mL, and the inhibition rate reached 88%, which was even better than that of Pyrimethanil, however, lower than that of Carbendazim. To the best of our knowledge, this is the first report on the antibacterial and antifungal activities of this series of novel thiochromanone derivatives containing a carboxamide moiety.

Selective Pseudo-irreversible Butyrylcholinesterase Inhibitors Transferring Antioxidant Moieties to the Enzyme Show Pronounced Neuroprotective Efficacy In Vitro and In Vivo in an Alzheimer's Disease Mouse Model.

A series of multitarget-directed ligands (MTDLs) was designed by functionalizing a pseudo-irreversible butyrylcholinesterase (BChE) inhibitor. The obtained hybrids were investigated in vitro regarding their hBChE and hAChE inhibition, their enzyme kinetics, and their antioxidant physicochemical properties (DPPH, ORAC, metal chelating). In addition, in vitro assays were applied to investigate antioxidant effects using murine hippocampal HT22 cells and immunomodulatory effects on the murine microglial N9 cell line. The MTDLs retained their antioxidative properties compared to the parent antioxidant-moieties in vitro and the inhibition of hBChE was maintained in the submicromolar range. Representative compounds were tested in a pharmacological Alzheimer's disease (AD) mouse model and demonstrated very high efficacy at doses as low as 0.1 mg/kg. The most promising compound was also tested in BChE-/- mice and showed reduced efficacy. In vivo neuroprotection by BChE inhibition can be effectively enhanced by incorporation of structurally diverse antioxidant moieties.

Novel Thiochromanone Derivatives Containing a Sulfonyl Hydrazone Moiety: Design, Synthesis, and Bioactivity Evaluation.

A series of novel thiochromanone derivatives containing a sulfonyl hydrazone moiety were designed and synthesized. Their structures were determined by 1H-NMR, 13C-NMR, and HRMS. Bioassay results showed that most of the target compounds revealed moderate to good antibacterial activities against Xanthomonas oryzae pv. oryzae, Xanthomonas oryzae pv. oryzicolaby, and Xanthomonas axonopodis pv. citri. Compound 4i had the best inhibitory activity against Xanthomonas oryzae pv. oryzae, Xanthomonas oryzae pv. oryzicolaby, and Xanthomonas axonopodis pv. citri, with the EC50 values of 8.67, 12.65, and 10.62 µg/mL, which were superior to those of Bismerthiazol and Thiodiazole-copper. Meanwhile, bioassay results showed that all of the target compounds proved to have lower antifungal activities against Sclerotinia sclerotiorum, Fusarium oxysporum, Gibberella zeae, Rhizoctonia solani, Verticillium dahlia, and Botrytis cinerea than those of Carbendazim.

Synthesis of 2-alkyl-chroman-4-ones via cascade alkylation-dechlorination of 3-chlorochromones.

An efficient and mild synthetic approach for 2-alkyl-substituted chroman-4-ones via zinc-mediated cascade decarboxylative ß-alkylation and dechlorination of 3-chlorochromones was developed. This transformation employed commercially available starting materials and was performed under mild conditions without heat, visible light, peroxide or heavy metals. Moreover, various alkyl NHPI esters with functional groups and differently substituted 3-chlorochromones were tolerated, affording the targeted products with moderate to excellent yields. This protocol could be utilized to construct a diverse library of 2-substituted chroman-4-one derivatives, which could be useful in the discovery of lead compounds for drug discovery in the future.

Design, synthesis and biological evaluation of 7-(5-((substituted - amino)-methyl)-thiophen-2-yl)-spiro-[chroman-2,4'-piperidin]-4-one hydrochloride analogues as anticancer agents.

A series of thirty-one novel 7-(5-((amino)-methyl)-thiophen-2-yl)-spiro-[chroman-2,4'-piperidin]-4-one hydrochloride analogues (Cst 1 - 31) have been designed, synthesized and characterized by 1H NMR, 13C NMR and MS spectral analysis. Here, we evaluated the anticancer potential and biological results of low-molecular-weight bridgehead oxygen and nitrogen-containing spirochromanones on proliferation and apoptosis of the human breast cancer cell line (MCF-7) and Murine melanoma (B16F10). The anticancer activity ranged from 2.9 to 35.0 µM. The most potent compounds Cst-22, Cst-24 and Cst-31 were found to be less toxic against human embryonic kidney (HEK-293) cell lines. Cst-24 and Cst-31 were found to be causing significant cytotoxicity through apoptotic cell death and also G2 phase arrest of cell cycle in B16F10 cells. In-silico ADME prediction stidies of the titled compounds were found within the rules outlined, and these compounds may not face any pharmacokinetic associated issues in the mere future upon developmental stage. These conjugates may serve as a lead for the discovery of potential anticancer drug candidate with better therapeutic profile.

Two in one: bifunctional derivatives of trolox acting as antimalarial and antioxidant agents.

Background: The aim of the present work was to set-up compounds that are able to act simultaneously as antimalarial and antioxidants. Trolox, a known antioxidant was chosen as a core structure to ensure the antioxidant activity and contribute to antiplasmodial effect. Results: Ten compounds were prepared in one step and evaluated on chloroquino-sensitive (3D7) and chloroquino-resistant (FcB1) strains of Plasmodium falciparum. The most active compound (3d) shows antiplasmodial activity in the range of chloroquine against chloroquino-sensitive and chloroquino-resistant P. falciparum strain. The antioxidant activity of (3d) was conducted through four tests and was found to be more potent than trolox itself and L-ascorbic acid. Conclusion: Compound (3d) can be considered as an excellent lead molecule for further in vivo studies. This study paves the way for building large chemical libraries to be investigated in the field of malaria.

Discovery of Small-Molecule Inhibitors of Receptor Activator of Nuclear Factor-κB Ligand with a Superior Therapeutic Index.

Receptor activator of nuclear factor-κB ligand (RANKL) constitutes the master mediator of osteoclastogenesis, while its pharmaceutical inhibition by a monoclonal antibody has been approved for the treatment of postmenopausal osteoporosis. To date, the pursuit of pharmacologically more favorable approaches using low-molecular-weight inhibitors has been hampered by low specificity and high toxicity issues. This study aimed to discover small-molecule inhibitors targeting RANKL trimer formation. Through a systematic screening of 39 analogues of SPD-304, a dual inhibitor of tumor necrosis factor (TNF) and RANKL trimerization, we identified four compounds (1b, 3b, 4a, and 4c) that selectively inhibited RANKL-induced osteoclastogenesis in a dose-dependent manner, without affecting TNF activity or osteoblast differentiation. Based on structure-activity observations extracted from the most potent and less toxic inhibitors of RANKL-induced osteoclastogenesis, we synthesized a focused set of compounds that revealed three potent inhibitors (19a, 19b, and 20a) with remarkably low cell-toxicity and improved therapeutic indexes as shown by the LC50 to IC50 ratio. These RANKL-selective inhibitors are an excellent starting point for the development of small-molecule therapeutics against osteolytic diseases.

Design, synthesis and biological evaluation of novel chroman derivatives as non-selective acetyl-CoA carboxylase inhibitors.

Acetyl-CoA carboxylases (ACCs) are the rate-limiting enzymes in the de no lipogenesis, which play an important role in the synthesis and oxidation of fatty acid. Recent research reveals that ACCs are tightly relevant to many kinds of metabolic diseases and cancers. In this study, we synthesized a series of chroman derivatives and evaluated their ACCs inhibitory activities, obtaining compound 4s with IC50 value of 98.06 nM and 29.43 nM of binding activities in ACC1 and ACC2, respectively. Compound 4s exhibited the most potent anti-proliferation activity against A549, H1975, HCT116 and H7901 cell lines (values of IC50: 0.578 µΜ, 1.005 µΜ, 0.680 µΜ and 1.406 µΜ, respectively). Docking studies were performed to explain the structure-activity relationships. These results indicate that compound 4s is a promising ACC1/2 inhibitor for the potent treatment of cancer.

3-Aryl-4-nitrobenzothiochromans S,S-dioxide: From Calcium-Channel Modulators Properties to Multidrug-Resistance Reverting Activity.

Our research groups have been involved for many years in studies aimed at identifying new active organic compounds endowed with pharmacological properties. In this work, we focused our attention on the evaluation of cardiovascular and molecular drug resistance (MDR) reverting activities of some nitrosubstituted sulphur-containing heterocycles. Firstly, we have examined the effects of 4-nitro-3-(4-methylphenyl)-3,6-dihydro-2H-thiopyran S,S-dioxide 5, and have observed no activity. Then we have extended our investigation to the 3-aryl-4-nitrobenzothiochromans S,S-dioxide 6 and 7, and have observed an interesting biological profile. Cardiovascular activities were assessed for all compounds using ex vivo studies, while the MDR reverting effect was evaluated only for selected compounds using tumor cell lines. All compounds were shown to affect cardiovascular parameters. Compound 7i exerted the most effect on negative inotropic activity, while 6d and 6f could be interesting molecules for the development of more active ABCB1 inhibitors. Both 6 and 7 represent structures of large possible biological interest, providing a scaffold for the identification of new ABCB1 inhibitors.

Synthesis and Antimicrobial Evaluation of Side-Chain Derivatives based on Eurotiumide A.

Side-chain derivatives of eurotiumide A, a dihydroisochroman-type natural product, have been synthesized and their antimicrobial activities described. Sixteen derivatives were synthesized from a key intermediate of the total synthesis of eurotiumide A, and their antimicrobial activities against two Gram-positive bacteria, methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MSSA and MRSA), and a Gram-negative bacterium, Porphyromonas gingivalis, were evaluated. The results showed that derivatives having an iodine atom on their aromatic ring instead of the prenyl moiety displayed better antimicrobial activity than eurotiumide A against MSSA and P. gingivalis. Moreover, we discovered that a derivative with an isopentyl side chain, which is a hydrogenated product of eurotiumide A, is the strongest antimicrobial agent against all three strains, including MRSA.

Synthesis of enantiopure (S)-6-chlorochroman-4-ol using whole-cell Lactobacillus paracasei biotransformation.

Chromane, which has a fused cyclic structure, is a significant molecule that can be found in the structure of many important compounds. Lactobacillus paracasei BD101 was demonstrated as whole-cell biocatalyst for the synthesis of (S)-6-chlorochroman-4-ol with immense enantioselectivity. The conditions of asymmetric reduction were optimized one factor by one factor using L paracasei BD101 to achieve enantiomerically pure product and complete conversion. Using these obtained optimization conditions, asymmetric reduction of 6-chlorochroman-4-one was performed under environmentally friendly conditions; 6-chlorochroman-4-one, having a fused cyclic structure as previously noted to be difficult to asymmetric reduction with biocatalysts, was enantiomerically reduced to (S)-6-chlorochroman-4-ol with an enantiomeric excess >99% on a high gram scale. This study is the first example in the literature for the enantiopure synthesis of (S)-6-chlorochroman-4-ol using a biocatalyst. Also notably, the optical purity of (S)-6-chlorochroman-4-ol obtained in this study through asymmetric bioreduction using whole-cell biocatalyst is the highest value in the literature. In this study, (S)-6-chlorochroman-4-ol was produced on a gram scale by an easy, inexpensive, and environmentally friendly method, which has shown the production of valuable chiral precursors for drug synthesis and other industrial applications. This study provides a convenient method for the production of (S)-6-chlorochroman-4-ol, which can meet the industrial green production demand of this chiral secondary alcohol.

Four-component green synthesis of benzochromene derivatives using nano-KF/clinoptilolite as basic catalyst: study of antioxidant activity.

An efficient procedure for the synthesis of benzochromene derivatives employing 1-(6-hydroxy-2-isopropenyl-1-benzofuran-yl)-1-ethanone (euparin), aldehydes, alkyl bromides, dialkyl acetylenedicarboxylate and triphenylphosphine in the presence of KF/CP NPs as a heterogeneous base nano-catalyst in water at 80 °C is investigated. Also, the antioxidant activity of some synthesized compounds was studied. The workup of mixture of reaction is simple, and the products can be separated easily by filtration. KF/CP NPs showed a good improvement in the yield of the product and displayed significant reusable activity.

Design, synthesis and molecular modeling of isothiochromanone derivatives as acetylcholinesterase inhibitors.

Aim: A series of novel isothio- and isoselenochromanone derivatives bearing N-benzyl pyridinium moiety were designed, synthesized and evaluated as acetylcholinesterase (AChE) inhibitors. Results: Most of the target compounds exhibited potent anti-AChE activities with IC50 values in nanomolar ranges. Among them, compound 15a exhibited the most potent anti-AChE activity (IC50 = 2.7 nM), moderate antioxidant activity and low neurotoxicity. Moreover, the kinetic and docking studies revealed that compound 15a was a mixed-type inhibitor, which bounds to peripheral anionic site and catalytic active site of AChE. Conclusion: Those results suggested that compound 15a might be a potential candidate for AD treatment.

Synthesis of isochroman-4-ones and 2H-pyran-3(6H)-ones by gold-catalyzed oxidative cycloalkoxylation of alkynes.

Gold catalysis is a convenient tool to oxidatively functionalize alkyne into a range of valuable compounds. In this article, we report a new access to isochroman-4-one and 2H-pyran-3(6H)-one derivatives that involves a gold-catalyzed oxidative cycloalkoxylation of an alkyne in the presence of a pyridine N-oxide. The reaction proceeds under mild conditions, is relatively efficient and exhibits a high functional group compatibility.

Synthesis and biological evaluation of SHetA2 (NSC-721689) analogs against the ovarian cancer cell line A2780.

A series of Flexible Heteroarotinoid (Flex-Het) analogs was synthesized and their biological activities were evaluated against the A2780 ovarian cancer cell line. The objective of this study was to establish structure-activity relationships (SARs) for new Flex-Het derivatives, which were previously inaccessible due to the limited availability of aryl isothiocyanate precursors. The current work developed a synthesis of isothiocyanate 13 and used it to prepare 14 diverse thiourea analogs of the lead compound SHetA2 (1, NSC-721689) from a range of commercial amines. Additionally, five new ureas were prepared along with nine N-benzylthioureas, five derivatives incorporating hydrazine or hydrazide linkers and four desmethyl compounds. Potencies and efficacies were determined for each derivative. Some of the new Flex-Hets displayed high activity with IC50 values ranging from 1.86 to 4.70 µM and 85.6-95.9% efficacies, which are comparable to or better than the lead compound (IC50 3.17 µM, 84.3% efficacy). Although SHetA2 is scheduled to enter clinical trials in the near future, alternative backup drug candidates have been identified in this work. The new agents possess similar pharmacological properties and retain selective activity against A2780 ovarian cancer cells. Although a mixed SAR was obtained for these analogs, diversified, highly potent molecules were identified for further investigation. In particular, agents 2c-d and 3e-f, which incorporated CF3 and OCF3 groups in place of NO2 on the pendent aryl ring, displayed high activity and excellent differentiation between normal and cancerous cells.

Discovery of (S)-6-methoxy-chroman-3-carboxylic acid (4-pyridin-4-yl-phenyl)-amide as potent and isoform selective ROCK2 inhibitors.

ROCK1 and ROCK2 are highly homologous isoforms. Accumulated studies indicate that they have distinct different functions, and the development of isoform selective ROCK inhibitors will pave new roads for the treatment of various diseases. In this work, a series of amide-chroman derivatives were synthesized and biologically evaluated in order to develop potent and isoform selective ROCK2 inhibitors. Remarkably, (S)-6-methoxy-chroman-3-carboxylic acid (4-pyridin-4-yl-phenyl)-amide ((S)-7c) possessed ROCK2 inhibitory activity with an IC50 value of 3 nM and 22.7-fold isoform selectivity (vs. ROCK1). Molecular docking indicated that hydrophobic interactions were the key element for the high potency and isoform selectivity of (S)-7c. The binding free energies predicted by MM/GBSA were in good agreement with the experimental bioactivities, and the analysis of individual energy terms suggested that residue Lys105 in ROCK1 or Lys121 in ROCK2 was the key residue for the isoform selectivity of (S)-7c.