Design, synthesis of novel chromene-based scaffolds targeting hepatocellular carcinoma: Cell cycle arrest, cytotoxic effect against resistant cancer cells, apoptosis induction, and c-Src inhibition

New chromene derivatives were synthesized based on 4-(3,4-dimethoxy)-4H-chromene scaffold. All target compounds exhibited cytotoxic activity against HepG2 cells (IC50  = 2.40-141.22 μM). Chromens 5 and 9 showed superior cytotoxicity over staurosporine (IC50  = 18.27 μM) and vinblastine (IC50  = 5.20 μM). c-Src kinase inhibition assay of compounds 5 and 9 displayed the dominant c-Src inhibitory activity of 5 (IC50  = 0.184 μM) over 9 (IC50  = 0.288 μM). The safety of the most potent compound 5 against normal WI-38 cells was confirmed via its IC50 of 115.75 μM comparable with 5-FU (IC50  = 16.28 μM). Moreover, the promising chromene 5 displayed potent cytotoxicity against resistant HepG2 cells with IC50 of 26.03 μM comparable with 5-FU (IC50  = 42.68 μM). The most active chromene 5 arrested the HepG2 cell cycle at the S phase and induced a 29-fold increase in the total number of apoptotic cells indicating pre-G1 apoptosis. The ability of compound 5 to induce apoptosis was supported via elevation of caspase-3, caspase-7, caspase-9 and proapoptotic Bax protein levels in addition to downregulation of the antiapoptotic Bcl2 protein. Molecular docking studies of compound 5 showed good binding interaction pattern inside c-Src kinase enzyme active site.

Paratrimerin Z, an undescribed chromene derivative from the roots of Paramignya trimera

From an EtOAc-soluble fraction of the roots of Paramignya trimera, one undescribed chromene derivative, paratrimerin Z (1), was isolated. Its structure was elucidated on the basis of NMR spectroscopic interpretation. The absolute configuration of 1 was determined by the specific rotation analysis of its acid-catalyzed hydrolysis product. Paratrimerin Z (1), at a concentration of 100 μM, did not show cytotoxicity against Hep3B human liver cancer cell line.

Chromene-based BioAIEgens: 'in-water' synthesis, regiostructure-dependent fluorescence and ER-specific imaging

Exploration of artificial aggregation-induced emission luminogens (AIEgens) has garnered extensive interest in the past two decades. In particular, AIEgens possessing natural characteristics (BioAIEgens) have received more attention recently due to the advantages of biocompatibility, sustainability and renewability. However, the extremely limited number of BioAIEgens extracted from natural sources have retarded their development. Herein, a new class of BioAIEgens based on the natural scaffold of chromene have been facilely synthesized via green reactions in a water system. These compounds show regiostructure-, polymorphism- and substituent-dependent fluorescence, which clearly illustrates the close relationship between the macroscopic properties and hierarchical structure of aggregates. Due to the superior biocompatibility of the natural scaffold, chromene-based BioAIEgens can specifically target the endoplasmic reticulum (ER) via the introduction of tosyl amide. This work has provided a new chromene scaffold for functional BioAIEgens on the basis of green and sustainable 'in-water' synthesis, applicable regiostructure-dependent fluorescence, and effective ER-specific imaging.

Novel quinazoline-chromene hybrids as anticancer agents: Synthesis, biological activity, molecular docking, dynamics and ADME studies

In this study, new quinazoline-chromene hybrid compounds were synthesized. The cytotoxic effects on cell viability of the hybrid compounds were tested against A549 human lung adenocarcinoma and BEAS-2B healthy bronchial epithelial cell lines in vitro. In addition, the ability of the active compounds to inhibit cell migration was tested. Molecular docking studies were performed to evaluate the ligand-protein interactions, and molecular dynamics simulations were performed to determine the interactions and stability of ligand-protein complexes. In silico absorption, distribution, metabolism, and excretion (ADME) studies were conducted to estimate the drug-likeness of the compounds. Compounds 4 (IC50  = 51.2 µM) and 5 (IC50  = 44.2 µM) were found to be the most active agents against A549 cells. They are found to be more selective against A549 cells than the reference drug doxorubicin. They also have the ability to significantly inhibit cell migration. They have the best docking scores against epidermal growth factor receptor (EGFR) (-11.300 and -11.226 kcal/mol) and vascular endothelial growth factor receptor 2 (VEGFR2) (-10.987 and -11.247 kcal/mol), respectively. In MD simulations, compounds 4 and 5 have strong hydrogen bond interactions above 80% of simulation times and showed a low ligand root mean square deviation (RMSD) around 2 Å. According to the ADME analysis, compounds 4 and 5 exhibit excellent drug-likeness and pharmacokinetic characteristics.

Synthesis, biological evaluation, and molecular docking study of chromen-linked hydrazine carbothioamides as potent α-glucosidase inhibitors

Inhibiting α-glucosidase is a reliable method for reducing blood sugar levels in diabetic individuals. Several novel chromen-linked hydrazine carbothioamide (3a-r) were designed and synthesized by condensation of chromone-3-carbaldehyde with a variety of substituted thiosemicarbazides. The structures of these new analogues were elucidated through various advanced spectroscopic techniques (1 H NMR, 13 C NMR, and ESI-MS). The resulted compounds were screened for α-glucosidase inhibitory potential and all the compounds (3a-r) exhibited potent inhibition of α-glucosidase with IC50 values ranging 0.29-53.70 µM. Among them compounds 3c, 3f, 3h, and 3r displayed the highest α-glucosidase inhibitor capability with IC50 values of 1.50, 1.28, 1.08, and 0.29 µM, respectively. Structure-activity relationship showed that different substituted groups are responsible for the variation in the α-glucosidase inhibition. The kinetics studies of the most active inhibitor (3r) were performed, to investigate the mode of inhibition and dissociation constants (Ki), that indicated a competitive inhibitor with Ki value of 1.47 ± 0.31 µM. Furthermore, molecular docking studies was performed to reveal the possible interactions, such as H-bonding, or π-π stacking, with the key residues of α-glucosidase. Docking analysis revealed the importance of hydrazine carbothioamide moiety of compounds in the attachment of ligands with the crucial residues of α-glucosidase. The estimated pharmacokinetic, physicochemical, and drug likeness properties of compounds 3a-r reflects that these molecules have acceptable range of these properties.

2-Amino-4-(4-meth-oxy-phen-yl)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carbo-nitrile acetic acid monosolvate

In the title co-crystal, C20H14N2O4·C2H4O2, the expected proton transfer from acetic acid to amine has not occurred. In the crystal, the chromene mol-ecules are linked by N-H⋯O and N-H⋯N hydrogen bonds to generate [100] columns. The acetic acid mol-ecules form inversion dimers linked by pairwise O-H⋯O hydrogen bonds and occupy voids between the columns.

Crystal structure of N-[3-(benzo[d]thia-zol-2-yl)-6-bromo-2H-chromen-2-yl-idene]-4-methyl-benzenamine

The title compound, C₂₃H₁₅BrN₂OS, was the unexpected product in an attempted synthesis of the isomeric 3-(benzo[d]thia-zol-2-yl)-6-bromo-1-p-tolyl-quinolin-2(1H)-one. The C_chromene=N-C angle is wide [125.28 (8)°]. The benzo-thia-zole and chromene ring systems are almost coplanar, with their planes parallel to (10); the toluene ring system is rotated by ca 40° out of the chromene plane. The mol-ecular packing involves layers with π-stacking, borderline 'weak' hydrogen bonds and possible C-H⋯π contacts.

4-Dimethylaminopyridine (DMAP), A Superior Mediator for Morita-Balylis-Hillman Reaction-Triggered Annulative Condensation of Salicylaldehydes and Acrylonitrile to Form 3-Cyano-2H-chromenes

We unveiled superior base mediators for the annulative condensation of salicylaldehydes and acrylonitrile to give 3-cyano-2H-chromenes, which has been mediated only by 1,4-diazabicyclo[2.2.2]octane (DABCO) over the past two decades. The reactions were most efficiently mediated by 4-dimethylaminopyridine (DMAP), which yielded 3-cyano-2H-chromenes in higher yields than DABCO in most cases. We also confirmed that the reaction remained high yielding in a decagram-scale experiment with a catalytic amount of DMAP. The utility of this reaction was also exemplified by derivatization of an obtained 3-cyano-2H-chromene into a known 2H-chromene-3-carboxylic acid, which was previously synthesized with a non-readily available reagent.

Design and synthesis of novel benzoxazole/chromene-phthalide scaffolds hybrids as potential natural products-based fungicide

Phthalide, benzoxazole, and chromene are important heterocyclic skeletons with extensive biological activities. In order to develop novel potential antifungal agents, twenty-two benzoxazole/chromene-containing phthalide derivatives were prepared, and their fungicidal activity against nine common plants pathogenic fungi were evaluated in vitro. The EC50 values indicated that compound Z-4b displayed superior antifungal activity against P. oryzae (11.0 μg/mL), F. solani (8.5 μg/mL), P. capsici (27.8 μg/mL), V. mali (3.1 μg/mL) and A. brassicae (4.3 μg/mL) strains, which was more potent than the two commercialized fungicides hymexazol and chlorothalonil. In addition, the structure-activity relationship analysis demonstrated that the combination site of oxazolamide with phthalide has an important effect on antifungal activity. This research offers a potential compound for the development of novel agricultural fungicides.

Structural diversity, biosynthesis, and health-promoting properties of brown algal meroditerpenoids

Marine algae that constitute hundreds of millions of tons of biomass are the oldest representatives of the plant kingdom. Recently, there has been growing interest in the utilization of algae as sustainable feedstocks for natural products with an economic value. Among these natural products are the meroditerpenoids, which are renowned for their protective effects against oxidative stress, inflammation, cancer, obesity, diabetes, and neurodegenerative disorders. Meroditerpenoids have a mixed biosynthetic origin and display a wide range of structural diversity. Their basic structure consists of a ring system bearing a diterpenoid side chain. Structural variations are observed in terms of the functional groups and saturation/cyclization of the diterpenoid side chain. This review classifies algal meroditerpenoids as plastoquinones, chromanols, chromenes, chromones, cyclic meroditerpenoids, nahocols, and isonahocols and examines their potential applications in functional foods and biopharmacology. Their lipid solubility, low molecular weight, and propensity to cross the blood-brain barrier places meroditerpenoids as potential drug candidates. There is growing interest in the study of algal meroterpenoids, and recent research has reported the structure of several new meroterpenoids and their biological activities. Further research is needed to extend the use of algal meroditerpenoids in preclinical trials. Understanding the mechanism of their biosynthesis will allow the development of de novo biosynthesis and biomimetic synthesis strategies for the industrial-scale production of meroditerpenoids and their synthetic derivatives to aid pharmaceutical research. This review is the first to summarize up-to-date information on all brown algae-derived meroditerpenoids.

Inhibitory Potential of Chromene Derivatives on Structural and Non-Structural Proteins of Dengue Virus

Dengue fever is a mosquito-borne viral disease that has become a serious health issue across the globe. It is caused by a virus of the Flaviviridae family, and it comprises five different serotypes (DENV-1 to DENV-5). As there is no specific medicine or effective vaccine for controlling dengue fever, there is an urgent need to develop potential inhibitors against it. Traditionally, various natural products have been used to manage dengue fever and its co-morbid conditions. A detailed analysis of these plants revealed the presence of various chromene derivatives as the major phytochemicals. Inspired by these observations, authors have critically analyzed the anti-dengue virus potential of various 4H chromene derivatives. Further, in silico, in vitro, and in vivo reports of these scaffolds against the dengue virus are detailed in the present manuscript. These analogues exerted their activity by interfering with various stages of viral entry, assembly, and replications. Moreover, these analogues mainly target envelope protein, NS2B-NS3 protease, and NS5 RNA-dependent RNA polymerase, etc. Overall, chromene-containing analogues exerted a potent activity against the dengue virus and the present review will be helpful for the further exploration of these scaffolds for the development of novel antiviral drug candidates.

Discovery of chromene compounds as inhibitors of PvdQ acylase of Pseudomonas aeruginosa

The acquisition of iron is a crucial mechanism for the survival of pathogenic bacteria such as Pseudomonas aeruginosa in eukaryotic hosts. The key iron chelator in this organism is the siderophore pyoverdine, which was shown to be crucial for iron homeostasis. Pyoverdine is a non-ribosomal peptide with several maturation steps in the cytoplasm and others in the periplasmatic space. A key enzyme for its maturation is the acylase PvdQ. The inhibition of PvdQ stops the maturation of pyoverdine causing a significant imbalance in the iron homeostasis and hence can negatively influence the survival of P. aeruginosa. In this work, we successfully synthesized chromene-derived inhibitory molecules targeting PvdQ in a low micromolar range. In silico modeling as well as kinetic evaluations of the inhibitors suggest a competitive inhibition of the PvdQ function. Further, we evaluated the inhibitor in vivo on P. aeruginosa cells and report a dose-dependent reduction of pyoverdine formation. The compound also showed a protecting effect in a Galleria mellonella infection model.

Synthesis, application, and antibacterial activity of new direct dyes based on chromene derivatives

AIM

The goal of this study is to synthesise, analyse, and employ two new direct dyes based on chromenes derivatives as the chromophoric moiety in dyeing wool, silk, and cotton, with good colour strength, light fastness, and other desirable features.

BACKGROUND

The quest for new direct dyes with antimicrobial qualities for Gram-positive, Gram-negative bacteria, and fungus is underway. These dyes are commonly used on cotton, silk, and wool materials, which have great light fastness, washing, rubbing, and sweating fastness.

METHODS

Antibacterial activity has been measured for all dyeing fabrics. The parent structure 1 has been synthesized previously as part of the experiment. Then, these dyes are prepared by diazotization followed by coupling reaction.

RESULTS AND DISCUSSION

The p-Aminobenzenesulfonic acid (C1) and 4-Aminoazobenzene-3,4'-disulfonic acid (C2) are diazotized in hydrochloric acid with sodium nitrite, then coupled with compound 1 in a molar ratio (1: 1) at 250C until the pH is fixed at 5. Finally, the monoazo and diazo direct dyes (D1 and D2) are created.

CONCLUSION

Wool, silk, and cotton materials benefit from the synthetic dyes' increased antibacterial action and dyeing qualities (exhaustion and fixing). They also offer better fastness qualities (light, rubbing, and perspiration).

Design of a Functional Chromene-Type Kobayashi Precursor: Gram-Scale Total Synthesis of Natural Xanthones by Highly Regioselective Aryne Annulation

The 2,2-dimethyl-2H-chromene motif is widely found in many bioactive molecules, and is a privileged structure in the pharmaceutical arena. We have developed a concise and regioselective approach to chromenes and chromanes through an aryne-based synthetic strategy. A practical, gram-scale synthetic route to a chromene-type aryne precursor was explored. Subsequently, cyclization under mild conditions afforded tetracyclic xanthone skeletons with excellent regioselectivity. Our approach provides a concise strategy for the gram-scale synthesis of chromene-type xanthones such as 6-deoxyisojacareubin, cylindroxanthone D, staudtiixanthone D, brasilixanthone A and cudracuspixanthone O.

Synthesis and Antimicrobial Evaluation of Some Novel Pyrimidine, Pyrazole, Chromene and Tetrahydrobenzo[b]thiophene Derivatives Bearing Pyrimidinthione Moiety

AIM AND OBJECTIVE

A novel collection of fused pyrimidine, pyridine, pyrazole, chromene and thiophene derivatives 2-30 have been newly synthesized by using the 1a, b as starting material. Fused pyrane exhibits a range of pharmacological activity such as cancer agents [1], antimicrobial [2-4], antioxidant [5], antiproliferative [6], cytotoxic activity [7], anticipated antitumor [8], antiparkinsonian [9] and anti-inflammatory [10]. Moreover, pyrane derivatives are well known for bacterial biofilm disruptor [11], anticonvulsant [12] and inhibitors of mycobacterium bovis [13].

MATERIALS AND METHODS

All melting points were measured using the Akofler Block instrument and are uncorrected. IR spectra (KBr) were recorded on a FTIR 5300 spectrometer (υ, cm-1). The 1H-NMR spectra were recorded on a Varian Gemini spectrometer. The 1H-NMR spectra were run at 300, 400 MHz and 13C-NMR spectra were run at 100 MHz in DMSO-d6, CDCl3 as solvents. The chemical shifts are expressed in parts per million (ppm) by using tetramethylsilane (TMS) as an internal reference, 1000 EX mass spectrometer at 70 eV. The purity of synthesized compounds was checked by thin-layer chromatography (TLC) (aluminum sheets) using nhexane, EtOAc (9:1, V/V, 7:3 V/V) eluent. Elemental analyses were carried out by the Microanalytical Research Center, Faculty of Science, and Microanalytical Unit, Faculty of Pharmacy, Cairo University, Egypt.

RESULTS AND DISCUSSION

A novel series of azoles and azines were designed and prepared via the reaction of 7-amino- 5-(4-chlorophenyl)-4-phenyl-2-thioxo-2,5-dihydro-1H-pyrano- [2,3-d]pyrimidine-6-carbonitrile 1a and 7-amino-4,5- diphenyl-2-thioxo-2,5-dihydro-1H-pyrano[2,3-d]-pyrimidine-6-carbonitrile 1b with some electrophilic and nucleophilic reagents. The structures of target compounds were confirmed by elemental analyses and spectral data. The novel synthesized compounds showed good antimicrobial activity against the previously mentioned microorganisms.

CONCLUSION

In conclusion, compounds 1a, 1b underwent ready cyclization to give fused heterocyclic compounds through reaction with different reagents and under different conditions and subjected to antimicrobial screening.

Synthesis of some 1H-1,5-benzodiazepine Series Containing Chromene Ring from α,β-Unsaturated Ketones of 6-Acetyl-5-Hydroxy-4-Methylcoumarin

BACKGROUND

Reaction of α,β-unsaturated ketones with o-phenylenediamine afforded corresponding 2,3-dihydro-1H-1,5-benzodiazepines.

OBJECTIVE

α,β-Unsaturated ketones of 6-acetyl-5-hydroxy-4-methylcoumarin are precursors for synthesis of 2,3-dihydro-1H-1,5-benzodiazepines by a reaction with o-phenylenediamine.

METHODS

Enones of 6-acetyl-5-hydroxy-4-methylcoumarin were prepared from this ketone and (un)substituted benzaldehydes in the presence of piperidine, triethylamine, or pyridine as a catalyst in absolute ethanol with 1:1 molar ratios, respectively. 2',3'-Dihydro-1H-1',5'-benzodiazepines were synthesized by using the reaction of these enones with o-phenylenediamine in absolute ethanol in the presence of glacial acetic acid as a catalyst. Their biological activities were evaluated using the disk diffusion method.

RESULTS

Seven new 2',3'-dihydro-1H-1',5'-benzodiazepines were obtained and their structures were confirmed by thin-layer chromatography, IR, NMR and MS spectra. Some synthesized benzodiazepines showed antibacterial and antifungal activities against Escherichia coli (Gram-(-) bacterium), Staphylococus epidermidis (Gram-(+) bacterium). Candida albicans (fungus).

CONCLUSION

The formation of enones from 6-acetyl-5-hydroxy-4-methylcoumarin and (un)substituted benzaldehydes could be catalyzed by piperidine, triethylamine, pyridine to afford similar yields. 2',3'-dihydro-1H- 1',5'-benzodiazepines have been synthesized from the aforementioned enones and o-phenylenediamine.

Novel Biomass Derived from Grape Pomace Waste as an Efficient Nanocatalyst for the Synthesis of Dibenzoxanthene, Tetraketone, bis(indolyl)alkane and Chromene Derivatives and their Antimicrobial Evaluation

BACKGROUND

Sulfonated carbon-based solid acids (CBSAs) have been reported as an efficient solid acid catalyst for many acid-catalyzed reactions. Furthermore, the use of carbon obtained from biomass waste has been explored and these materials showed a higher catalytic performance and higher stability compared to other solid acids.

OBJECTIVE

Novel biomass carbon-based solid acids nanoparticles with high catalytic activity in organic transformation, such as Grape pomace waste-SO3H Nanoparticles (GPW-SO3H NPs), were successfully synthesized.

MATERIALS AND METHODS

Grape pomace waste-SO3H Nanoparticles (GPW-SO3H NPs) were successfully synthesized. The grape pomace waste was dried in an oven at a temperature of 70°C and crushed to powder using an electric spice grinder. A mixture of powdered grape pomace waste (1 g) and concentrated sulfuric acid (>98%, 10 mL) was stirred at room temperature. Then, the resultant mixture was transferred into a 100 mL sealed Teflon-lined autoclave and kept at 180°C for 12 h. After cooling to room temperature, the resulting black solid was dried at 100°C in an oven under vacuum and the sulfonic acid-functionalized magnetic nanoparticles (Fe3O4@C-SO3H) were obtained.

RESULTS AND DISCUSSIONS

The catalytic activity of GPW-SO3H was assessed through an easy and rapid protocol developed for the one-pot synthesis of 14-aryl-14-H-dibenzo [a,j]xanthene, arylmethylene [bis(3- hydroxy-2-cyclohexene-1-one)], bis(indolyl)alkane and 2-amino-4-aryl-7-hydroxy-4H-chromene-3-carbonitrile derivatives in excellent yields. The advantages of this method include use of waste material for catalyst synthesis, high yields, mild reaction conditions, uncomplicated work-up procedures, neutral conditions, and recoverable catalyst.

CONCLUSION

We have shown that biomass-derived solid acids, prepared from grape pomace waste, serve as a non-toxic, inexpensive and a promising eco-friendly and novel carbon-based solid acid nanocatalyst for organic transformations.

Two new chromene derivatives from Artemisia songarica

Two new chromene derivatives, songaricachromenes A (1) and B (2), were isolated from Artemisia songarica, along with 10 known compounds (3-12). The structures and stereochemistry of the new compounds were elucidated by analyses of the NMR, MS, and electronic circular dichroism (ECD) data. All the isolates (1-12) were evaluated for their NO inhibitory effects on LPS-stimulated BV-2 microglial cells.

Ethyl 2-[2-(4-oxo-4H-chromen-2-yl)phenoxy]acetate

In the title flavonoid derivative, C₁₉H₁₆O₅, the chromene portion is planar (r.m.s. deviation = 0.022 Å) with the substituents lying closely to the same plane. The dihedral angle between its mean plane and that of the benzene ring is 4.9 (1)°. This planarity is due, in part, to the presence of a strong intramolecular C-H⋯O hydrogen bond and to two weak C-H⋯O contacts. In the crystal, neighboring molecules are linked by a C-H⋯O hydrogen bond and a C-H⋯π interaction, forming chains along the a-axis direction.

Microtubule inhibitor, SP-6-27 inhibits angiogenesis and induces apoptosis in ovarian cancer cells

In ovarian cancer (OVCA), treatment failure due to chemo-resistance is a serious challenge. It is therefore critical to identify new therapies that are effective against resistant tumors and have reduced side effects. We recently identified 4-H-chromenes as tubulin depolymerizing agents that bind to colchicine site of beta-tubulin. Here, we screened a chemical library of substituted 4-H-chromenes and identified SP-6-27 to exhibit most potent anti-proliferative activity towards a panel of human cisplatin sensitive and resistant OVCA cell lines with 50% inhibitory concentration (IC₅₀; mean ± SD) ranging from 0.10 ± 0.01 to 0.84 ± 0.20 μM. SP-6-27 exhibited minimum cytotoxicity to normal ovarian epithelia. A pronounced decrease in microtubule density as well as G2/M cell cycle arrest was observed in SP-6-27 treated cisplatin sensitive/resistant OVCA cells. The molecular mechanism of SP-6-27 induced cell death revealed modulation in cell-cycle regulation by upregulation of growth arrest and DNA damage inducible alpha transcripts (GADD45). An enhanced intrinsic apoptosis was observed in OVCA cells through upregulation of Bax, Apaf-1, caspase-6, -9, and caspase-3. In vitro wound healing assay revealed reduced OVCA cell migration upon SP-6-27 treatment. Additionally, SP-6-27 and cisplatin combinatorial treatment showed enhanced cytotoxicity in chemo-sensitive/resistant OVCA cells. Besides effect on cancer cells, SP-6-27 further restrained angiogenesis by inhibiting capillary tube formation by human umbilical vein endothelial cells (HUVEC). Together, these findings show that the chromene analog SP-6-27 is a novel chemotherapeutic agent that offers important advantages for the treatment of ovarian cancer.

Crystal structure of 1-methyl-2-methyl-amino-3-nitro-1H-chromeno[2,3-b]pyridin-5(10aH)-one

In the title compound, C₁₄H₁₃N₃O₄, the pyran ring adopts an envelope conformation with the methine C atom as the flap. The dihedral angle between the benzene and hydro­pyridine rings is 29.33 (3)°. The methyl­amine C atom deviates from the plane of its attached ring by 0.380 (5) Å and an intra­molecular N—H⋯O hydrogen bond closes an S(6) ring. In the crystal, weak C—H⋯O hydrogen bonds and aromatic π–π stacking inter­actions [centroid–centroid distances vary from 3.6529 (10) to 3.6872 (10) Å] link the mol­ecules, generating a three-dimensional network.

Design, Synthesis and Biological Evaluation of Novel 5H-Chromenopyridines as Potential Anti-Cancer Agents

A novel series of 5H-chromenopyridines was identified as anticancer agents in our continuing effort to discover and develop new small molecule anti-proliferative agents. Based on our initial lead SP-6-27 compound, we designed and synthesized novel tricyclic 5H-thiochromenopyridine and 5H-chromenopyridine analogs to evaluate the impact of an additional ring, as well as conformational flexibility on cytotoxic activity against human melanoma and glioma cell lines. All of the 5H-thiochromenopyridines have been achieved in good yields (89%–93%) using a single-step, three-component cyclization without the need for purification. The 5H-chromenopyridine analog of the potent 5H-thiochromenopyride was obtained in a good yield upon purification. All newly-prepared 5H-thiochromenopyridines showed good to moderate cytotoxicity against three melanoma and two glioma cell lines (3–15 μM). However, the 5H-chromenopyridine analogue that we prepared in our laboratory lost cytotoxic activity. The moderate cytotoxic activity of 5H-thiochromenopyridines shows the promise of developing chromenopyridines as potential anticancer agents.

Crystal structure of 10-[(3-oxo-3H-benzo[f]chromen-1-yl)meth-yl]-2-tri-fluoro-methyl-9a,10-di-hydro-benz[4,5]imidazo[1,2-a]pyrimidin-4(5aH)-one

In the title compound, C₂₅H₁₄F₃N₃O₃, the dihedral angle between the planes of the benz[4,5]imidazo[1,2-a]pyrimidine unit (r.m.s. deviation = 0.035 Å) and the benzochromene ring system (r.m.s. deviation = 0.106 Å) is 72.82 (5)°. In the crystal, mol­ecules are linked by C—H⋯O inter­actions, generating [010] C(9) chains. A weak aromatic π–π stacking inter­action [centroid–centroid separation = 3.5376 (15) Å] is also observed.

Crystal structure of 2-methyl-amino-4-(6-methyl-4-oxo-4H-chromen-3-yl)-3-nitro-pyrano[3,2-c]chromen-5(4H)-one with an unknown solvate

In the title compound, C23H16N2O7, the mean planes of the two chromene units (r.m.s. deviations = 0.031 and 0.064 Å) are almost normal to one another with a dihedral angle of 85.59 (6)°. The central six-membered pyran ring has a distorted envelope conformation, with the methine C atom at the flap. There is an intra-molecular N-H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, mol-ecules are linked by pairs of N-H⋯O hydrogen bonds, forming inversion dimers with an R 2 (2)(12) ring motif. The dimers are linked by pairs of C-H⋯O hydrogen bonds, enclosing R 2 (2)(6) ring motifs, forming zigzag chains along [001]. The chains are linked by a second pair of C-H⋯O hydrogen bonds, forming slabs parallel to (110). Within the slabs there are C-H⋯π inter-actions present. A region of disordered electron density was treated with the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18] following unsuccessful attempts to model it as plausible solvent mol-ecule(s). The given chemical formula and other crystal data do not take into account the unknown solvent mol-ecule(s).

Crystal structure of methyl 2-(7-hy-droxy-2-oxo-2H-chromen-4-yl)acetate

In the title coumarin derivative, C₁₂H₁₀O₅, the fused ring system is almost planar (r.m.s deviation = 0.016 Å). The C_ar—C—C=O torsion angle of the side chain is −8.4 (2)° In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds, generating C(8) chains propagating in the [100] direction. The chains are cross-linked by weak C—H⋯O inter­actions, thereby generating undulating (001) sheets.

Crystal structure of 2-amino-7-hy-droxy-4-(4-hy-droxy-phen-yl)-4H-chromene-3-carbo-nitrile

In the title compound, C16H12N2O3, the chromene ring system is nearly planar [maximum deviation from the mean plane = 0.057 (1) Å], and is almost perpendicular to the benzene ring, with a dihedral angle of 85.29 (5)°. In the crystal, mol-ecules are linked by classical N-H⋯O, O-H⋯O and O-H⋯N hydrogen bonds, and weak C-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular network. Furthermore, a weak π-π stacking inter-action is observed; the centroid-to-centroid distance is 3.7260 (7) Å.

Crystal structure of 4-(6-chloro-4-oxo-4H-chromen-3-yl)-2-methyl-amino-3-nitro-4H,5H-pyrano[3,2-c]chromen-5-one chloro-form monosolvate

In the title compound, C₂₃H₁₄Cl₄N₂O₇, the pyran ring has an envelope conformation with the methine C atom as the flap. The chromene rings are almost planar (r.m.s. deviations of 0.027 and 0.018 Å) and their mean planes are inclined to one another by 85.61 (10)°. The mean planes of the pyran ring and the chromene ring fused to it are inclined to one another by 7.41 (13)°. The mol­ecular structure is stabilized by an intra­molecular N—H⋯O hydrogen bond, generating an S(6) ring motif. In the crystal, mol­ecules are linked by pairs of N—H⋯O hydrogen bonds, forming inversion dimers with an R²₂(12) ring motif. The dimers are linked by pairs of C—H⋯O hydrogen bonds, enclosing R²₂(18) ring motifs, forming chains along [010]. Within the chains there are C—H⋯π inter­actions. The chains are linked via slipped parallel π–π inter­actions, forming a three-dimensional structure [the shortest inter-centroid distance is 3.7229 (19) Å].

Crystal structure of 4-azido-methyl-6-tert-butyl-2H-chromen-2-one

In the title compound, C14H15N3O2, one of the methyl C atoms of the tert-butyl group lies almost in the plane of the chromene ring system [deviation = -0.097 (2) Å], one lies above and one lies below [deviations = 1.460 (3) and 1.006 (3) Å, respectively]. The C-C-N-N torsion angle is 142.33 (17)°. In the crystal, moelcules are linked by weak C-H⋯O hydrogen bonds to generate C(6) chains propagating in the [010] direction.

Crystal structure of 2-chloro-1-(6-fluoro-3,4-di-hydro-2H-chromen-2-yl)ethanone

In the title mol­ecule, C₁₁H₁₀ClFO₂, the benzene ring, the F atom and the O atom of the di­hydro­pyran ring are essentially coplanar, with an r.m.s. deviation of 0.007 Å. The di­hydro­pyran ring is in a half-chair conformation. In the crystal, mol­ecules are linked by pairs of weak C—H⋯π hydrogen bonds, forming inversion dimers.

Crystal structure of (E)-2-[(4-chloro-2H-chromen-3-yl)methyl-idene]-N-cyclo-hexyl-hydrazinecarbo-thio-amide

In the title compound, C17H20ClN3OS, the mean plane of the central thio-urea core makes dihedral angles of 26.56 (9) and 47.62 (12)° with the mean planes of the chromene moiety and the cyclo-hexyl ring, respectively. The cyclo-hexyl ring adopts a chair conformation. The N-H atoms of the thio-urea unit adopt an anti conformation. The chromene group is positioned trans, whereas the cyclo-hexyl ring lies in the cis position to the thione S atom, with respect to the thio-urea C-N bond. In the crystal, mol-ecules are linked by N-H⋯S hydrogen bonds, forming inversion dimers enclosing R (2) 2(8) ring motifs. The dimers are linked by C-H⋯Cl hydrogen bonds, enclosing R (6) 6(44) ring motifs, forming sheets lying parallel to (010).

Crystal structure of 4-(4-meth-oxy-phen-yl)-7,7-dimethyl-2-methyl-amino-3-nitro-7,8-di-hydro-4H-chromen-5(6H)-one

In the title compound, C₁₉H₂₂N₂O₅, the six-membered carbocyclic ring of the chromene moiety adopts an envelope conformation with the dimethyl-substituted C atom as the flap. The pyran ring has a flat-boat conformation. The meth­oxy­phenyl ring is orthogonal to the mean plane of the chromene moiety, with a dihedral angle of 89.97 (8)°. The amine N atom deviates from the chromene mean plane by 0.1897 (16) Å. The methyl­amine and the nitro group are involved in an intra­molecular N—H⋯O hydrogen bond which generates an S(6) ring motif. They are slightly twisted out of the plane of the chromene moiety with torsion angles of C—N—C—O(pyran) = 2.2 (3)° and O(nitro)—N—C—C = −5.6 (2)°. In the crystal, there are only C—H⋯π inter­actions present, forming inversion-related dimers.

Rhodium-catalyzed intramolecular hydroarylation of 1-halo-1-alkynes: regioselective synthesis of semihydrogenated aromatic heterocycles

The regioselective intramolecular hydroarylation of (3-halo-2-propynyl)anilines, (3-halo-2-propynyl) aryl ethers, or (4-halo-3-butynyl) aryl ethers was efficiently catalyzed by Rh2(OCOCF3)4 to give semihydrogenated aromatic heterocycles, such as 4-halo-1,2-dihydroquinolines, 4-halo-3-chromenes, or 4-(halomethylene)chromans, in good to excellent yields. Some synthetic applications taking advantage of the halo-substituents of the products are also illustrated.

Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives

An efficient entry to the preparation of elusive 4-unsubstituted-3-iodo-2H-chromenes has been accomplished as result of a catalytic cyclization. Thus, upon exposition of [(3-iodoprop-2-yn-1-yl)oxy]arenes to IPrAuNTf₂ (3 mol %), in 1,4-dioxane at 100 °C, the desired heterocyclic motif is readily assembled. This process nicely tolerates a variety of functional groups and, interestingly, it is compatible with the presence of strong electron-withdrawing groups attached to the arene. The overall transformation can be termed as a new example of a migratory cycloisomerization and, formally, it involves well-blended 1,2-iodine shift and hydroarylation steps.

Organocatalyzed synthesis of 2-amino-8-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles

2-Amino-8-oxo-tetrahydro-4H-chromene-3-carbonitriles were synthesized for the first time from a tandem Michael addition - cyclization reaction between cyclohexane-1,2-dione and benzylidenemalononitriles. An enantioselective synthesis of these compounds was achieved in moderate ee values (up to 63% ee) by using a cinchona alkaloid-derived thiouea catalyst.