Tricyclic Quinazoline Alkaloids: Isolation, Synthesis, Chemical Modification, and Biological Activity

Visible-light promoted radical cascade cyclization of 3-allyl-2-arylquinazolinones for the synthesis of phosphorylated dihydroisoquinolino[1,2-b]quinazolinones

A novel visible-light promoted metal-free radical cascade cyclization reaction has been developed with 3-allyl-2-arylquinazolinones as a new class of radical acceptor. This photocatalytic protocol represents an efficient approach to construct phosphorylated dihydroisoquinolino[1,2-b]quinazolinones featuring mild conditions, broad substrate scope, and gram-scale synthesis.

Access to CF2COR-Containing Quinazolinones via Visible-Light-Induced Domino Difluoroalkylation/Cyclization of N-Cyanamide Alkenes

A green and highly efficient visible-light-induced radical cascade difluoroalkylation/cyclization reaction of N-cyanamide alkenes has been developed. A variety of CF2COR-containing quinazolinones have been obtained in high yields with cheap non-metallic 4CzIPN as the photocatalyst. This photocatalytic reaction provides rapid, facile, and practical access to valuable polycyclic quinazolinone, and it is amenable to the gram scale.

Photocatalytic cyclization of 3-(2-isocyanophenyl)quinazolin-4(3H)-ones for the construction of quinoxalino[2,1-b]quinazolinones

A new kind of building unit, 3-(2-isocyanophenyl)quinazolin-4(3H)-ones, was designed and synthesized for the construction of novel quinoxalino[2,1-b]quinazolinones. The radical cyclization of 3-(2-isocyanophenyl)quinazolin-4(3H)-ones with ethers afforded ether-substituted tetracyclic quinoxalino[2,1-b]quinazolinones under photocatalytic and metal-free conditions. In the process, the isocyano accepts a carbon radical to give an imidoyl radical, which adds to the electron-deficient CN bond in quinazolin-4(3H)-one.

Cinchonine: A Versatile Pharmacological Agent Derived from Natural Cinchona Alkaloids

BACKGROUND

Cinchonine is one of the Cinchona alkaloids that is commercially extracted from the Peruvian bark of Cinchona officinalis L. (Family: Rubiaceae). It is also obtained in much lower quantities from other species of Cinchona, such as Cinchona calisaya, Cinchona succirubra, and Cinchona pubescens, and in some other plants, such as Remijia peruviana. Cinchonine has been historically used as an anti-malarial agent. It also has a wide range of other biological properties, including anti-cancer, anti-obesity, anti-inflammatory, anti-parasitic, antimicrobial, anti-platelet aggregation, and anti-osteoclast differentiation.

AIM AND OBJECTIVE

This review discusses the pharmacological activity of cinchonine under different experimental conditions, including in silico, in vitro, and in vivo. It also covers the compound's physicochemical properties, toxicological aspects, and pharmacokinetics.

METHODOLOGY

A comprehensive literature search was conducted on multiple online databases, such as PubMed, Scopus, and Google Scholar. The aim was to retrieve a wide range of review/research papers and bibliographic sources. The process involved applying exclusion and inclusion criteria to ensure the selection of relevant and high-quality papers.

RESULTS

Cinchonine has numerous pharmacological properties, making it a promising compound for various therapeutic applications. It induces anti-cancer activity by activating caspase-3 and PARP-1, and triggers the endoplasmic reticulum stress response. It up-regulates GRP78 and promotes the phosphorylation of PERK and ETIF-2α. Cinchonine also inhibits osteoclastogenesis, inhibiting TAK1 activation and suppressing NFATc1 expression by regulating AP-1 and NF-κB. Its potential anti-inflammatory effects reduce the impact of high-fat diets, making it suitable for targeting obesity-related diseases. However, research on cinchonine is limited, and further studies are needed to fully understand its therapeutic potential. Further investigation is needed to ensure its safety and efficacy in clinical applications.

CONCLUSION

Overall, this review article explains the pharmacological activity of cinchonine, its synthesis, and physicochemical properties, toxicological aspects, and pharmacokinetics.

Nickel-Catalyzed Intramolecular Dual Annulation Reaction of Aryl Nitrile-Containing 1,2,3-Benzotriazin-4(3H)-ones: A Pathway To Synthesize Luotonin A and Related Polycyclic Pyrroloquinazolinones

Herein, we report a nickel-catalyzed intramolecular denitrogenative dual annulation reaction of aryl nitrile-containing 1,2,3-benzotriazine-4(3H)-ones to synthesize polycyclic pyrroloquinazolinones with a tolerance of a wide diversity of substituents. This catalytic reaction is the first denitrogenative transannulation of 1,2,3-benzotriazine-4(3H)-one with nitrile, which can be applied as the critical step to synthesize luotonin A with a high step economy.

Chemodivergent Tandem Radical Cyclization of Alkene-Substituted Quinazolinones: Rapid Access to Mono- and Di-Alkylated Ring-Fused Quinazolinones

Chemodivergent tandem radical cyclization offers exciting possibilities for the synthesis of structurally diverse cyclic compounds. Herein, we revealed a chemodivergent tandem cyclization of alkene-substituted quinazolinones under metal- and base-free conditions, this transformation is initiated by alkyl radicals produced from oxidant-induced α-C(sp3 )-H functionalization of alkyl nitriles or esters. The reaction resulted in the selective synthesis of a series of mono- and di-alkylated ring-fused quinazolinones by modulating the loading of oxidant, reaction temperature, and reaction time. Mechanistic investigations show that the mono-alkylated ring-fused quinazolinones is constructed by the key process of 1,2-hydrogen shift, whereas the di-alkylated ring-fused quinazolinones is mainly achieved through crucial steps of resonance and proton transfer. This protocol is the first example of remote second alkylation on the aromatic ring via α-C(sp3 )-H functionalization and difunctionalization achieved by association of two unsaturated bonds in radical cyclization.

Synthesis of 2,3-Fused Quinazolinones via the Radical Cascade Pathway and Reaction Mechanistic Studies by DFT Calculations

An efficient radical cascade cyclization of unactivated alkenes toward the synthesis of a series of ring-fused quinazolinones has been developed in moderate to excellent yields using commercially available ethers, alkanes, and alcohols, respectively, under a base-free condition in a short time without a transition metal as catalyst. Notably, the transformations can be carried out with the advantages of a broad substrate scope and high atomic economy. Density functional theory calculations and wavefunction analyses were performed to elucidate the radical reaction mechanism.

Metal-Free Photoinduced Hydrocyclization of Unactivated Alkenes toward Ring-Fused Quinazolin-4(3H)-ones via Intermolecular Hydrogen Atom Transfer

A visible-light-induced hydrocyclization of unactivated alkenes was developed using 3CzClIPN as the photocatalyst to generate substituted α-methyldeoxyvasicinones and α-methylmackinazolinones in moderate to good yields. An intermolecular hydrogen atom transfer with THF as the hydrogen source was involved. Mechanism studies indicated that the intramolecular addition of the in situ formed aminal radical to the unactivated alkene generated the polycyclic quinazolinone.

Supported Palladium-Catalyzed Tandem Synthesis of 2-(Alkylamino/amino)-3-arylquinazolin-4(3H)-ones Employing CO Source

Herein, we demonstrated heterogeneous and recyclable polystyrene-supported palladium (Pd@PS) nanoparticles (NPs) catalyzed tandem addition and intramolecular aminocarbonylative cyclization approach for the synthesis of potentially bioactive 2-(alkylamino/amino)-3-arylquinazolin-4(3H)-one analogues from 2-iodophenylcarbodiimides employing amines as nucleophiles and oxalic acid as an ex-situ CO alternative. Various cyclic/acyclic primary and secondary amines were employed and selectively produced substituted 2-(alkylamino)-3-arylquinazolin-4(3H)-ones in good to excellent yields. In addition, we extended the developed strategy to fix two ammonium carbamate and oxalic acid as gaseous NH₃ and CO sources respectively, for the synthesis of 2-amino-3-arylquinazolin-4(3H)-one derivatives. Furthermore, gram scale applicability, diverse substrate scope and high recyclability of the Pd@PS catalyst were the major achievements of the developed protocol.

Metal-Catalyzed Cascade Reactions between Alkynoic Acids and Dinucleophiles: A Review

Cascade reactions provide a straightforward access to many valuable compounds and reduce considerably the number of steps of a synthetic sequence. Among the domino and multicomponent processes that involve alkynes, the cascade reaction between alkynoic acids and C-, N-, O- and S-aminonucleophiles stands out as a particularly powerful tool for the one-pot construction of libraries of nitrogen-containing heterocyclic compounds with scaffold diversity and molecular complexity. This reaction, based on an initial metal-catalyzed cycloisomerization that generates an alkylidene lactone intermediate, was originally catalyzed by gold(I) catalysts, along with silver salts or Brönsted acid additives, but other alternative metal catalysts have emerged in the last decade as well as different reaction media. This review examines the existing literature on the topic of metal-catalyzed cascade reactions of acetylenic acids and dinucleophiles and discusses aspects concerning substrate/catalyst ratio for every catalyst system, nature of the aminonucleophile involved and substrate scope. In addition, alternative solvents are also considered, and an insight into the pathway of the reaction and possible intermediates is also provided.

Synthesis of Quinazolinone-Fused Tetrahydroisoquinolines and Related Polycyclic Scaffolds by Iodine-Mediated sp3 C-H Amination

An iodine-mediated intramolecular sp³ C-H amination reaction producing quinazolinone-fused polycyclic skeletons from 2-aminobenzamide precursors is reported. This reaction does not use transition metals, has a broad substrate scope, and can be used on a gram scale. Under the optimal reaction conditions, a variety of quinazolinone-fused tetrahydroisoquinolines and derivatives of Rutaecarpine were synthesized from readily accessible compounds. The reaction proceeds well with crude 2-aminobenzamide derivatives, allowing for the synthesis of the products from simple 2-aminobenzoic acids and tetrahydroisoquinolines without purification of the 2-aminobenzamide intermediates. Preliminary biological experiments have identified Cereblon (CRBN) inhibitory activity and relevant anti-myeloma medicinal properties in some of these polycyclic products.

A Novel Isaindigotone Derivative Displays Better Anti-Proliferation Activities and Induces Apoptosis in Gastric Cancer Cells

Isaindigotone is an alkaloid containing a pyrrolo-[2,1-b]quinazoline moiety conjugated with a benzylidene group and isolated from the root of Isatis indigotca Fort. However, further anticancer activities of this alkaloid and its derivatives have not been fully explored. In this work, a novel isaindigotone derivative was synthesized and three different gastric cell lines and one human epithelial gastric cell line were used to study the anti-proliferation effects of the novel isaindigotone derivative BLG26. HGC27 cells and AGS cells were used to further explore the potential mechanisms. BLG26 exhibited better anti-proliferation activities in AGS cells with a half-maximal inhibitory concentration (IC50) of 1.45 μM. BLG26 caused mitochondrial membrane potential loss and induced apoptosis in both HGC27 cells and AGS cells by suppressing mitochondrial apoptotic pathway and PI3K/AKT/mTOR axis. Acute toxicity experiment showed that LD50 (median lethal dose) of BLG26 was above 1000.0 mg/kg. This research suggested that BLG26 can be a potential candidate for the treatment of gastric cancer.

Synthesis of pyrimidine-containing alkaloids

This review deals with the synthesis of naturally occurring alkaloids containing partially or completely saturated pyrimidine nuclei. The interest in these compounds is associated with their structural diversity, high biological activity and toxicity. The review is divided into four parts, each of which describes a number of synthetic methodologies toward structurally different naturally occurring alkaloids containing saturated cyclic six-membered amidine, guanidine, aminal and urea (thiourea) moieties, respectively. The development of various synthetic strategies for the preparation of these compounds has remarkably increased during the past few decades. This is primarily due to the fact that some of these compounds are isolated only in limited quantities, which makes it practically impossible to study their full structural characteristics and biological activity.

Visible-Light Photosynthesis of CHF2 /CClF2 /CBrF2 -Substituted Ring-fused Quinazolinones in Dimethyl Carbonate

With eco-friendly and sustainable CO₂ -derived dimethyl carbonate as the sole solvent, the visible-light-induced cascade radical reactions have been established as a green and efficient tool for constructing various CHF₂ /CClF₂ /CBrF₂ -substituted ring-fused quinazolinones.

Structural insight from intermolecular interactions and energy framework analyses of 2-substituted 6,7,8,9-tetrahydro-11H-pyrido[2,1-b]quinazolin-11-ones

The crystal structures of three mackinazolinone derivatives (2-amino-6,7,8,9-tetrahydro-11H-pyrido[2,1-b]quinazolin-11-one at room temperature, and 2-nitro-6,7,8,9-tetrahydro-11H-pyrido[2,1-b]quinazolin-11-one and N-(11-oxo-6,8,9,11-tetrahydro-7H-pyrido[2,1-b]quinazolin-2-yl)benzamide at 100 K) are explored using X-ray crystallography. To delineate the different intermolecular interactions and the respective interaction energies in the crystal architectures, energy framework analyses were carried out using the CE-B3LYP/6-31G(d,p) method implemented in the CrystalExplorer software. In the structures the different molecules are linked by C-H...O, C-H...N and N-H...O hydrogen bonds. Together with these hydrogen bonds, C-H...π and C-O...π interactions are involved in the formation of a three-dimensional crystal network. A Hirshfeld surface analysis allows the visualization of the two-dimensional fingerprint plots and the quantification of the contributions of H...H, H...C/C...H and H...O/O...H contacts throughout the different crystal structures. To obtain additional information on the intrinsic properties of our targets and to compare the experimental crystal structures with their respective conformations in the gas phase, quantum chemical calculations at the B3LYP-D3BJ/6-311++G(d,p) level of theory, including Grimme's D3 correction term and BJ damping functions, were carried out to account for intramolecular dispersion interactions. The identified energy gaps between the highest occupied and the lowest unoccupied molecular orbitals (HOMO-LUMO gap) of our targets in the gas phase and in two implicit solvents (methanol and dimethyl sulfoxide) allow us to quantify the impact of different substituents on the reactivity of mackinazolinone derivatives.

Crystal structure and Hirshfeld surface analysis of bis-(6,7,8,9-tetra-hydro-11H-pyrido[2,1-b]quinazolin-5-ium) tetra-chlorido-zincate

The title compound, (C12H15N2)2[ZnCl4], is a salt with two symmetrically independent, essentially planar heterocyclic cations and a slightly distorted tetra-hedral chloro-zincate dianion. N-H⋯Cl hydrogen bonds link these ionic constituents into a discrete aggregate, which comprises one formula unit. The effect of hydrogen bonding is reflected in the minor distortions of the [ZnCl4]2- moiety: distances between the cation and chlorido ligands engaged in classical hydrogen bonds are significantly longer than the others. Secondary inter-actions comprise C-H⋯π hydrogen bonding and weak π-π stacking. A Hirshfeld surface analysis indicates that the most abundant contacts in packing stem from H⋯H (47.8%) and Cl⋯H/H⋯Cl (29.3%) inter-actions.

Crystal structure, Hirshfeld surface analysis and energy framework study of 6-formyl-7,8,9,11-tetra-hydro-5H-pyrido[2,1-b]quinazolin-11-one

At 100 K, the title compound, C13H12N2O2, crystallizes in the ortho-rhom-bic space group Pna21 with two very similar mol-ecules in the asymmetric unit. An intra-molecular N-H⋯O hydrogen bond leads to an S(6) graph-set motif in each of the mol-ecules. Inter-molecular π-π stacking and C=O⋯π inter-actions involving the aldehyde O atoms link mol-ecules into stacks parallel to [100]. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing stem from H⋯H (49.4%) and H⋯O/O⋯H (21.5%) inter-actions. Energy framework calculations reveal a significant contribution of dispersion energy. The crystal studied was refined as a two-component inversion twin.

Stereochemistry of the methyl-idene-bridged quinazoline-iso-quinoline alkaloid 3-{[6,7-dimeth-oxy-1-(4-nitro-phen-yl)-1,2,3,4-tetra-hydro-isoquinolin-2-yl]methyl-idene}-1,2,3,9-tetra-hydro-pyrrolo-[2,1-b]quinazolin-9-one methanol monosolvate

Two potentially bioactive fragments, namely a tricyclic quinazoline derivative with an exocyclic alkene moiety and a substituted iso-quinoline, are coupled to give 3-{[6,7-dimeth-oxy-1-(4-nitro-phen-yl)-1,2,3,4-tetra-hydro-isoquinolin-2-yl]methyl-idene}-1,2,3,9-tetra-hydro-pyrrolo-[2,1-b]quinazolin-9-one. The target product crystallizes as a methanol solvate, C₂₉H₂₆N₄O₅·CH₄O, and is E configured. The alternative Z isomer would necessarily imply either considerable twist about the central double bond or very unfavourable intra-molecular contacts between sterically more demanding substituents. The main residue and the co-crystallized solvent mol-ecule aggregate to discrete pairs via a classical O-H⋯O hydrogen bond with a distance of 2.8581 (7) Å between the methanol OH donor and the quinazolinone O=C acceptor.

(E)-6-(Furan-2-ylmethylidene)-6,7,8,9-tetrahydropyrido[2,1-b]quinazoline-11-thione

A new quinazolinthione derivative was synthesized, and X-ray diffraction analysis proved the E configuration for the exocyclic double bond in the mol­ecule.

A quinazolinthione, C₁₇H₁₄N₂OS, was synthesized by the condensation reaction of 6,7,8,9-tetra­hydro-11H-pyrido[2,1-b]quinazolin-11-thione with furfural. The mol­ecule crystallizes in the monoclinic system (Cc space group) and has an E configuration with respect to the exocyclic C=C bond. In the crystal, mol­ecules are linked through C—H⋯π(furan) inter­actions, forming zigzag chains propagating along the [001] direction.

Deep eutectic solvent for an expeditious sono-synthesis of novel series of bis-quinazolin-4-one derivatives as potential anti-cancer agents

To produce a new category of anti-cancer compounds, a facile and environmentally sustainable method for preparing diversified bis-quinazolinones was demonstrated using recyclable deep eutectic solvent (DES) under ultrasonic irradiation. The reactions were performed smoothly with a wide scope of substrates affording the desired derivatives in good-to-excellent yields under an atom-economical pathway. Particularly, halogen substituents that are amenable for further synthetic elaborations are well tolerated. Furthermore, the 'greenness' of the protocol was assessed within the scope of several green metrics and found to display an excellent score in the specified parameters. Cytotoxic activity of all novel bis-quinazolinones was investigated utilizing two cancer cell lines: breast (MCF-7) and lung (A549) cell lines and their IC50 values were determined. Most of the prepared derivatives displayed fascinating inhibitory activity with IC50 values in a low micromolar range. Remarkably, the derivative 7e [3,3'-(sulfonylbis(4,1-phenylene))bis(2-methyl-6-nitroquinazolin-4(3H)-one)] showed superior potency against MCF-7 and A549 cancer cell lines, with IC50 values of 1.26 µM and 2.75 µM, respectively. Moreover, this derivative was found to have low toxicity to the normal breast cell line (MCF-10A) and could serve as a promising lead candidate for further development.

Isaindigotone as an inhibitor of the lipopolysaccharide‑induced inflammatory reaction of BV‑2 cells and corresponding mechanisms

Isaindigotone possesses extensive pharmacological activities, including anti‑inflammatory effects. The present study investigated the role of isaindigotone in the inhibition of neuroinflammation. Mouse BV‑2 cells were incubated with lipopolysaccharide (LPS; 1 mg/l) for 24 h in a microglial inflammatory model in vitro. The effects of isaindigotone on BV‑2 cell proliferation were observed using the 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide method. Following co‑incubation, an enzyme‑linked immunosorbent assay and western blot analysis were used to analyze cellular levels of cytokines and associated protein expression, including the phosphorylation of nuclear factor (NF)‑κB. The effects of isaindigotone concentration on LPS‑mediated cell chemotaxis behavior were assessed using a chemotaxis assay. The results indicated that isaindigotone is non‑toxic towards BV‑2 cells. Compared with the LPS group, isaindigotone significantly reduced the secretion of tumor necrosis factor‑α and interleukin‑1β in BV‑2 cells and reduced the cell chemotaxis caused by LPS; it also reversed morphological changes in the BV‑2 cells and inhibited the phosphorylation of NF‑κB. The results of the present study suggest that isaindigotone can inhibit inflammatory reactions in LPS‑induced BV‑2 cells, and provides a theoretical basis and experimental evidence for examining the mechanism underlying the isaindigotone‑induced inhibition of neuroinflammation.

Regioselective synthesis and biological evaluation ofN-substituted 2-aminoquinazolin-4-ones

The reaction of methyl anthranilates withN-arylcyanamides can selectively form two different regioisomericN-substituted 2-aminoquinazolin-4-one derivatives.

Hexafluoroisopropyl alcohol mediated synthesis of 2,3-dihydro-4H-pyrido[1,2-a]pyrimidin-4-ones

An efficient synthesis of novel 2,3-dihydro-4H-pyrido[1,2-a]pyrimidin-4-ones has been reported. Inexpensive and readily available substrates, environmentally benign reaction condition, and product formation up to quantitative yield are the key features of this methodology. Products are formed by the aza-Michael addition followed by intramolecular acyl substitution in a domino process. The polar nature and strong hydrogen bond donor capability of 1,1,1,3,3,3-hexafluoropropan-2-ol is pivotal in this cascade protocol.

Progress in Studies on Rutaecarpine. II.--Synthesis and Structure-Biological Activity Relationships

Rutaecarpine is a pentacyclic indolopyridoquinazolinone alkaloid found in Evodia rutaecarpa and other related herbs. It has a variety of intriguing biological properties, which continue to attract the academic and industrial interest. Studies on rutaecarpine have included isolation from new natural sources, development of new synthetic methods for its total synthesis, the discovery of new biological activities, metabolism, toxicology, and establishment of analytical methods for determining rutaecarpine content. The present review focuses on the synthesis, biological activities, and structure-activity relationships of rutaecarpine derivatives, with respect to their antiplatelet, vasodilatory, cytotoxic, and anticholinesterase activities.

Ligand-free Pd-catalyzed and copper-assisted C-H arylation of quinazolin-4-ones with aryl iodides under microwave heating

A microwave-assisted method for the palladium-catalyzed direct arylation of quinazolin-4-one has been developed under copper-assistance. This method is applicable to a wide range of aryl iodides and substituted (2H)-quinazolin-4-ones. This protocol provides a simple and efficient way to synthesize biologically relevant 2-arylquinazolin-4-one backbones.