Antitumor agents. 199. Three-dimensional quantitative structure-activity relationship study of the colchicine binding site ligands using comparative molecular field analysis

Enantioselective Synthesis of Aza-Flavanones with an All-Carbon Quaternary Stereocenter via NHC-Catalyzed Intramolecular Annulation

An enantioselective synthesis of functionalized aza-flavanone derivatives using the N-heterocyclic carbene-catalyzed intramolecular Stetter reaction of sulphoamido benzaldehydes has been reported. This procedure presents the first original approach for synthesizing chiral functionalized flavonoids at the 3-position, containing an all-carbon quaternary stereogenic center. This advancement significantly enriches the chemical toolbox for the preparation of complex nitrogen-containing compounds and opens up new avenues for further research and development in synthetic organic chemistry.

Insights on a new sulfonamide chalcone with potential antineoplastic application

Chalcones (E)-1,3-diphenyl-2-propene-1-ones, a class of biosynthetic precursor molecules of flavonoids, have a wide variety of biological applications. Besides the natural products, many synthetic derivatives and analogs became an object of continued interest in academia and industry. In this work, a synthesis and an extensive structural study were performed on a sulfonamide chalcone 1-Benzenesulfonyl-3-(4-bromobenzylidene)-2-(2-chlorophenyl)-2,3-dihydro-1H-quinolin-4-one with potential antineoplastic application. In addition, in silico experiments have shown that the sulfonamide chalcone fits well in the ligand-binding site of EGFR with seven μ-alkyl binding energy interactions on the ligand-binding site. Finally, the kinetic stability and the pharmacophoric analysis for EGFR indicated the necessary spatial characteristics for potential activity of sulfonamide chalcone as an antagonist.

Palladium-catalyzed 1,2-amino carbonylation of 1,3-dienes with (N-SO2Py)-2-iodoanilines: 2,3-dihydroquinolin-4(1H)-ones synthesis

A palladium-catalyzed 1,2-amino carbonylation of 1,3-dienes with (N-SO₂Py)-2-iodoanilines has been developed for the construction of 2,3-dihydroquinolin-4(1H)-one scaffolds.

Palladium-catalyzed directing group assisted and regioselectivity reversed cyclocarbonylation of arylallenes with 2-iodoanilines

A palladium-catalyzed regioselective cyclocarbonylation of N-(2-pyridyl)sulfonyl (N-SO₂Py)-2-iodoanilines with allenes was developed. The regioselectivity of arylallenes was reversed. Control experiments and DFT calculations were performed to understand the reaction details.

One-Pot Synthesis of 4-Quinolone via Iron-Catalyzed Oxidative Coupling of Alcohol and Methyl Arene

Herein, we describe the iron(III)-catalyzed oxidative coupling of alcohol/methyl arene with 2-amino phenyl ketone to synthesize 4-quinolone. Alcohols and methyl arenes are oxidized to the aldehyde in the presence of an iron catalyst and di-tert-butyl peroxide, followed by a tandem process, condensation with amine/Mannich-type cyclization/oxidation, to complete the 4-quinolone ring. This method tolerates various kinds of functional groups and provides a direct approach to the synthesis of 4-quinolones from less functionalized substrates.

Chelating Group Enabled Palladium-Catalyzed Regiodivergent Carbonylative Synthesis of 2,3-Dihydroquinolin-4(1H)-ones

A new procedure on palladium-catalyzed carbonylative cyclization of N-(2-pyridyl)sulfonyl (N-SO₂ Py)-2-iodoanilines with terminal alkenes has been developed for the rapid construction of dihydroquinolin-4(1H)-one scaffolds. Enabled by the chelating group and using benzene-1,3,5-triyl triformate (TFBen) as the CO source, both aromatic and aliphatic alkenes were smoothly transformed into the corresponding 2,3-dihydroquinolin-4(1H)-ones in good yields with excellent regioselectivities. Notably, the reaction of aromatic alkenes produces 2-aryl-2,3-dihydroquinolin-4(1H)-ones, while 3-alkyl-2,3-dihydroquinolin-4(1H)-ones were obtained when aliphatic alkenes were used. This protocol has been applied in the synthesis of antitumor agent A as well.

Heterogeneous Synergistic Catalysis for Promoting Aza-Michael–Henry Tandem Reaction for the Synthesis of Chiral 3-Nitro-1,2-Dihydroquinoline

Heterogeneous synergistic catalysis by SBA-15 immobilized chiral amines catalysts has promoted efficient aza-Michael–Henry tandem reaction for the synthesis of chiral 3-Nitro-1,2-Dihydroquinoline. Final products in the asymmetric aza-Michael–Henry cascade reactions between 2-aminobenzaldehyde and β-nitrostyrolene were afforded in a yield of 85% and an enantiomeric excess (ee) value of 98% on (S)-(–)-2-aminomethyl-1-ethylpyrrolidine immobilized SBA-15. SBA-15-AEP catalyst has been also extended to the asymmetric aza-Michael–Henry cascade reaction of substituted R1-2-aminobenzaldehyde and R2-substituted nitroolefin. The heterogeneous synergistic mechanism for both tertiary amine and secondary amine immobilized mesoporous has been proposed in detail including the geometrical constraints in the ee promotion.

Synthesis of dihydroquinolinones via iridium-catalyzed cascade C-H amidation and intramolecular aza-Michael addition

An iridium-catalyzed annulation of chalcones with sulfonyl azides via cascade C-H amidation and intramolecular aza-Michael addition was developed, affording a variety of 2-aryl-2,3-dihydro-4-quinolones in moderate to good yields. This reaction features easy operation, readily available starting materials, and the cascade formation of two C-N bonds in one pot.

Recent advances in the asymmetric synthesis of pharmacology-relevant nitrogen heterocycles via stereoselective aza-Michael reactions

In this review, recent applications of a stereoselective aza-Michael reaction for asymmetric synthesis of naturally occurring N-containing heterocyclic scaffolds and their usefulness to pharmacology are summarized.

7-Deacetyl-10-alkylthiocolchicine derivatives - new compounds with potent anticancer and fungicidal activity

A series of new semi-synthetic 7-deacetyl-10-alkylthiocolchicne derivatives with ethyl, n-propyl, i-propyl and n-butyl substituents were synthesised and characterised by spectroscopic methods, elemental analysis, DFT calculations and molecular docking simulations. All the synthesized compounds have been tested for fungicidal and anticancer activities against SKOV-3, LoVo, MCF-7, MDA-MB-231 and the lung-derived fibroblast CCD39Lu. All the new colchicine derivatives exhibit significantly higher cytotoxicity towards the SKOV-3 tumour cell line than the natural product - colchicine. The most effective cytotoxic agents were 7-deacetyl-10-n-buthylthiocolchicine and 7-deacetyl-10-i-propylthiocolchicine. Among all the compounds tested, 7-deacetyl-10-n-buthylthiocolchicine exhibited the highest fungicidal activity. Molecular modeling indicated that several mutations found in the β-tubulin unit of the tested fungal strains are crucial for antifungal activity and selectivity of 7-deacetyl-10-n-buthylthiocolchicine. The obtained results may be useful for the development of selective colchicine derivatives as effective fungicidal and/or anticancer drugs.

Probing the opportunities for designing anthelmintic leads by sub-structural topology-based QSAR modelling

A quantitative structure-activity (QSAR) model has been developed for enriched tubulin inhibitors, which were retrieved from sequence similarity searches and applicability domain analysis. Using partial least square (PLS) method and leave-one-out (LOO) validation approach, the model was generated with the correlation statistics of [Formula: see text] and [Formula: see text] of 0.68 and 0.69, respectively. The present study indicates that topological descriptors, viz. BIC, CH_3_C, IC, JX and Kappa_2 correlate well with biological activity. ADME and toxicity (or ADME/T) assessment showed that out of 260 molecules, 255 molecules successfully passed the ADME/T assessment test, wherein the drug-likeness attributes were exhibited. These results showed that topological indices and the colchicine binding domain directly influence the aetiology of helminthic infections. Further, we anticipate that our model can be applied for guiding and designing potential anthelmintic inhibitors.

Synthesis, molecular modeling and biological evaluation of aza-flavanones as α-glucosidase inhibitors

An efficient acid catalyzed methodology has been employed to synthesize a variety of aza-flavanones and their α-glucosidase inhibitory activity is evaluated using acarbose, miglitol and voglibose as reference standards. Molecular modeling studies were performed for all compounds to identify the important binding modes responsible for the inhibition activity of α-glucosidase which helped find key interactions between the enzyme and the active compounds. Among all the compounds 5g, 5r and 5w have shown high α-glucosidase inhibition activity compared to standard reference drugs and have been identified as promising potential antidiabetic agents. This study is the first biological evaluation of aza-flavanones as α-glucosidase inhibitors.

Crystal structure of 6,8-diphenyl-2-(4-fluorophenyl)-2,3-dihydroquinolin-4(3H)-one, C27H20FNO

C27H20FNO, monoclinic, P21/n (no. 14), a = 13.1620 Å, b = 13.8779 Å, c = 11.1618 Å, β = 99.710(1)°, V = 2009.62(6) Å3, Z = 4, R gt(F) = 0.0436, wR ref(F 2) = 0.1310, T = 173(2) K.

Transition-metal-free oxidative intermolecular cyclization reaction: synthesis of 2-aryl-4-quinolones

Herein, a novel and efficient intermolecular cyclization of 2-aminoacetophenones with aldehydes was developed for the synthesis of 2-aryl-4-quinolones through C–C and C–N bond formation.

Organocatalytic one-pot asymmetric synthesis of 2-aryl-2,3-dihydro-4-quinolones

A highly efficient organocatalytic one-pot approach for enantioselective synthesis of (R)-2-aryl-2,3-dihydro-4-quinolones from o-aminoacetophenones and aryl aldehydes has been achieved.

Chiral Phosphoric Acid Catalyzed Asymmetric Synthesis of 2-Substituted 2,3-Dihydro-4-quinolones by a Protecting-Group-Free Approach

Chiral 2-substituted 2,3-dihydro-4-quinolones were synthesized based on the chiral phosphoric acid catalyzed intramolecular aza-Michael addition reaction using N-unprotected 2-aminophenyl vinyl ketones as substrates in good yields with high enantioselectivities.

Enantioselective one-pot synthesis of dihydroquinolones via BINOL-derived Lewis acid catalysis

A high-yielding and diastereoselective route to biologically significant 2-aryl- and 2-alkyl-3-amido dihydroquinolones has been developed in up to 90 : 10 e.r. by employing a novel Lewis acidic BINOL-derived copper(ii) catalyst.

Rhodium(iii)-catalyzed coupling of N-sulfonyl 2-aminobenzaldehydes with oxygenated allylic olefins through C–H activation

N-Sulfonyl-2-aminobenzaldehyde undergoes C–H activation and coupling with oxygenated allylic olefins under redox-neutral conditions with high efficiency.

Design, synthesis, and mechanism of action of 2-(3-hydroxy-5-methoxyphenyl)-6-pyrrolidinylquinolin-4-one as a potent anticancer lead

New 6- (or 6,7-) substituted 2-(hydroxyl substituted phenyl)quinolin-4-one derivatives were synthesized and screened for antiproliferative effects against cancer cell lines. Structure-activity relationship correlations were established and the most promising compound 2-(3-hydroxy-5-methoxyphenyl)-6-pyrrolidin-1-ylquinolin-4-one (6h) exhibited strong inhibitory activity against various human cancer cell lines, particularly non-small cell lung cancer NCI-H522. Additional studies suggested a mechanism of action resembling that of the antimitotic drug vincristine. The presence of a C-ring OH group in 6h will allow this compound to be converted readily to a water soluble and physicochemically stable hydrophilic prodrug. Compound 6h is proposed as a new anticancer lead compound.

Per-6-amino-β-cyclodextrin as a chiral base catalyst promoting one-pot asymmetric synthesis of 2-aryl-2,3-dihydro-4-quinolones

A highly efficient one-pot synthesis of enantiomerically enriched 2-aryl-2,3-dihydroquinolin-4(1H)-ones has been carried out for the first time using per-6-ABCD as a supramolecular host, chiral base catalyst, and a reusable promoter to give the corresponding scaffold with high yield (up to 99%) and enantiomeric excess (up to 99%). The catalyst is recovered and reused without loss in its activity.

Palladium-catalyzed asymmetric conjugate addition of arylboronic acids to heterocyclic acceptors

Flava Flavanone: Asymmetric conjugate additions to chromones and 4-quinolones are reported utilizing a single catalyst system formed in situ from Pd(OCOCF(3))(2) and (S)-tBuPyOX. Notably, these reactions are performed in wet solvent under ambient atmosphere, and employ readily available arylboronic acids as the nucleophile, thus providing ready access to these asymmetric heterocycles (see scheme).

Synthesis and photophysical properties of 2-aryl-6,8-bis(arylethenyl)-4-methoxyquinolines

Iodine-methanol mediated oxidative-aromatization of 2-aryl-6,8-dibromo-2,3-dihydroquinolin-4(1H)-ones afforded the corresponding 2-aryl-6,8-dibromo-4-methoxy-quinolines in high yield and purity. The isomeric 1-(2-amino-3,5-dibromophenyl)-3-aryl-2-propen-1-ones reacted with iodine in methanol afford in a single pot operation the corresponding 2-aryl-6,8-dibromo-4-methoxyquinoline (major) and 2-aryl-6,8-dibromoquinolin-4(1H)-one (minor) products that were separated in sequence by column chromatography on silica gel. Suzuki-Miyaura cross-coupling of the 6,8-dibromo-4-methoxyquinoline derivatives with excess arylvinylboronic acids afforded the corresponding 2-aryl-6,8-bis(2-arylethenyl)-4-methoxyquinolines. The absorption and fluorescence properties of these compounds were also determined.

Discrimination of ligands with different flexibilities resulting from the plasticity of the binding site in tubulin

Tubulin, an α,β heterodimer, has four distinct ligand binding sites (for paclitaxel, peloruside/laulimalide, vinca, and colchicine). The site where colchicine binds is a promising drug target for arresting cell division and has been observed to accommodate compounds that are structurally diverse but possess comparable affinity. This investigation, using two such structurally different ligands as probes (one being colchicine itself and another, TN16), aims to provide insight into the origin of this diverse acceptability to provide a better perspective for the design of novel therapeutic molecules. Thermodynamic measurements reveal interesting interplay between entropy and enthalpy. Although both these parameters are favourable for TN16 binding (ΔH < 0, ΔS > 0), but the magnitude of entropy has the determining role for colchicine binding as its enthalpic component is destabilizing (ΔH > 0, ΔS > 0). Molecular dynamics simulation provides atomistic insight into the mechanism, pointing to the inherent flexibility of the binding pocket that can drastically change its shape depending on the ligand that it accepts. Simulation shows that in the complexed states both the ligands have freedom to move within the binding pocket; colchicine can switch its interactions like a "flying trapeze", whereas TN16 rocks like a "swing cradle", both benefiting entropically, although in two different ways. Additionally, the experimental results with respect to the role of solvation entropy correlate well with the computed difference in the hydration: water molecules associated with the ligands are released upon complexation. The complementary role of van der Waals packing versus flexibility controls the entropy-enthalpy modulations. This analysis provides lessons for the design of new ligands that should balance between the "better fit" and "flexibility"', instead of focusing only on the receptor-ligand interactions.

Synthesis and structure-activity relationship study of antimicrotubule agents phenylahistin derivatives with a didehydropiperazine-2,5-dione structure

Plinabulin (11, NPI-2358) is a potent microtubule-targeting agent derived from the natural diketopiperazine "phenylahistin" (1) with a colchicine-like tubulin depolymerization activity. Compound 11 was recently developed as VDA and is now under phase II clinical trials as an anticancer drug. To develop more potent antimicrotubule and cytotoxic derivatives based on the didehydro-DKP skeleton, we performed further modification on the tert-butyl or phenyl groups of 11, and evaluated their cytotoxic and tubulin-binding activities. In the SAR study, we developed more potent derivatives 33 with 2,5-difluorophenyl and 50 with a benzophenone in place of the phenyl group. The anti-HuVEC activity of 33 and 50 exhibited a lowest effective concentration of 2 and 1 nM for microtubule depolymerization, respectively. The values of 33 and 50 were 5 and 10 times more potent than that of CA-4, respectively. These derivatives could be a valuable second-generation derivative with both vascular disrupting and cytotoxic activities.

Asymmetric Methods for the Synthesis of Flavanones, Chromanones, and Azaflavanones

Flavanones, chromanones, and related structures are privileged natural products that display a wide variety of biological activities. Although flavanoids are abundant in nature, there are a limited number of available general and efficient synthetic methods for accessing molecules of this class in a stereoselective manner. Their structurally simple architectures belie the difficulties involved in installation and maintenance of the stereogenic configuration at the C2 position, which can be sensitive and can undergo epimerization under mildly acidic, basic, and thermal reaction conditions. This review presents the methods currently used to access these related structures. The synthetic methods include manipulation of the flavone/flavanone core, carbon-carbon bond formation, and carbon-heteroatom bond formation.

Antitumor agents 273. Design and synthesis of N-alkyl-thiocolchicinoids as potential antitumor agents

As a part of our continuing study of colchicinoids as therapeutically useful antitumor drugs, thiocolchicine derivatives, including their phosphate and other water soluble salts, were synthesized and evaluated for inhibition of tubulin polymerization and for in vitro cytotoxicity. Three compounds, 7, 10, and 11, showed potent inhibition of tubulin assembly (IC(50)=0.88-1.1 microM). In addition, compound 7, a water soluble succinic acid salt of N-deacetylthiocolchicine (4), showed potent cytotoxicity against a panel of tumor cell lines, suggesting it might be a potential lead to be developed as a therapeutic antitumor agent. Compound 8, a water soluble succinic acid salt of N,N-dimethyl-N-deacetylthiocolchicine (5), showed selective activities against HCT-8 and SK-BR-3 cells. N,N-Diethyl-N-deacetylthiocolchicine (6) seemed not to be a substrate for the P-gp efflux pump, based on the similar ED(50) values obtained against P-gp over-expressing KBvin (0.0146 microg/mL) cells and the parent KB (0.0200 microg/mL) cell line.

Lead identification of conformationally restricted benzoxepin type combretastatin analogs: synthesis, antiproliferative activity, and tubulin effects

We have synthesized a series of polymethoxylated rigid analogs of combretastatin A-4 which contain a benzoxepin ring in place of the usual ethylene bridge present in the natural combretastatin products. The compounds display antiproliferative activity when evaluated against the MCF-7 and MDA human breast carcinoma cell lines. 5-(3-Hydroxy-4-methoxyphenyl)-4-(3,4,5-trimethoxyphenyl)-2,3-dihydro-benzoxepine (11g) was found to be the most potent product when evaluated against the MCF-7 breast cancer cell line. A brief computational study of the structure-activity relationship for the synthesized compounds is presented. These 4,5-diarylbenzoxepins are identified as potentially useful scaffolds for the further development of antitumor agents which target tubulin.

Glycopeptide dendrimer colchicine conjugates targeting cancer cells

Screening of a 65,536-member one-bead-one-compound (OBOC) combinatorial library of glycopeptide dendrimers of structure ((betaGal)(n)(+1)X(8)X(7)X(6)X(5))(2)DapX(4)X(3)X(2)X(1)(beta-Gal)(m) (betaGal=beta-galactosyl-thiopropionic acid, X(8-1)=variable amino acids, Dap=l-2,3-diaminopropionic acid, n, m=0, or 1 if X(8)=Lys resp. X(1)=Lys) for binding of Jurkat cells to the library beads in cell culture, resynthesis and testing lead to the identification of dendrimer J1 (betaGal-Gly-Arg-His-Ala)(2)Dap-Thr-Arg-His-Asp-CysNH(2) and related analogues as delivery vehicles. Cell targeting is evidenced by FACS with fluorescein conjugates such as J1F. The colchicine conjugate J1C is cytotoxic with LD(50)=1.5 microM. The beta-galactoside groups are necessary for activity, as evidenced by the absence of cell-binding and cytotoxicity in the non-galactosylated, acetylated analogue AcJ1F and AcJ1C, respectively. The pentagalactosylated dendrimer J4 betaGal(4)(Lys-Arg-His-Leu)(2)Dap-Thr-Tyr-His-Lys(betaGal)-Cys) selectively labels Jurkat cell as the fluorescein derivative J4F, but its colchicine conjugate J4C lacks cytotoxicity. Tubulin binding assays show that the colchicine dendrimer conjugates do not bind to tubulin, implying intracellular degradation of the dendrimers releasing the active drug.

Synthesis and preclinical evaluations of 2-(2-fluorophenyl)-6,7-methylenedioxyquinolin-4-one monosodium phosphate (CHM-1-P-Na) as a potent antitumor agent

CHM-1 [2-(2-fluorophenyl)-6,7-methylenedioxyquinolin-4-one] (1) has a unique antitumor mechanism of action. However, because 1 has relatively low hydrophilicity, it was evaluated only via ip administration, which is not clinically acceptable. In this study, we synthesized the monosodium phosphate salt (CHM-1-P-Na, 4) of 1 as a hydrophilic prodrug. Compound 4 was rapidly converted into 1 following iv and po administration and also possessed excellent antitumor activity in a SKOV-3 xenograft nude mice model. Compound 4 also had clear-cut pharmacological effects on enzymes related with tumor cells. Neither 4 nor 1 significantly affected normal biological function in a safety pharmacology profiling study. Compound 1 caused apoptotic effects in breast carcinoma cells via accumulation of cyclin B1, and importantly, the endogenous levels of the mitotic spindle checkpoint proteins BubR1 directly correlated with cellular response to microtubule disruption. With excellent antitumor activity profiles, 4 is highly promising for development as an anticancer clinical trials candidate.

Synthesis of an azide-tagged library of 2,3-dihydro-4-quinolones

We describe the assembly of a 960-member library of tricyclic 2,3-dihydro-4-quinolones using a combination of solution-phase high-throughput organic synthesis and parallel chromatographic purification. The library was produced with high efficiency and complete chemo- and diastereoselectivity by diversification of an azide-bearing quinolone via a sequence of [4 + 2] cycloadditions, N-acylations, and reductive aminations. The azide-functionalization of this library is designed to facilitate subsequent preparation of fluorescent or affinity probes, as well as small-molecule/surface conjugation.