Synthesis and Anticancer Properties of New 3-Methylidene-1-sulfonyl-2,3-dihydroquinolin-4(1H)-ones.

Quinolinones have been known for a long time as broad-spectrum synthetic antibiotics. More recently, the anticancer potential of this group of compounds has been investigated. Following this direction, we obtained a small library of 3-methylidene-1-sulfonyl-2,3-dihydroquinolin-4(1H)-ones with various substituents at positions 1, 2, 6, and 7 of the quinolinone ring system. The cytotoxic activity of the synthesized analogs was tested in the MTT assay on two cancer cell lines in order to determine the structure-activity relationship. All compounds produced high cytotoxic effects in MCF-7, and even higher in HL-60 cells. 2-Ethyl-3-methylidene-1-phenylsulfonyl-2,3-dihydroquinolin-4(1H)-one, which was over 5-fold more cytotoxic for HL-60 than for normal HUVEC cells, was selected for further tests. This analog was shown to inhibit proliferation and induce DNA damage and apoptosis in HL-60 cells.

Syntheses and Reactions of Pyrroline, Piperidine Nitroxide Phosphonates.

Organophosphorus compounds occupy a significant position among the plethora of organic compounds, but a limited number of paramagnetic phosphorus compounds have been reported, including paramagnetic phosphonates. This paper describes the syntheses and further transformations of pyrroline and piperidine nitroxide phosphonates by well-established methods, such as the Pudovik, Arbuzov and Horner-Wadsworth-Emmons (HWE) reactions. The reaction of paramagnetic a-bromoketone produced a vinylphosphonate in the Perkow reaction. Paramagnetic a-hydroxyphosphonates could be subjected to oxidation, elimination and substitution reactions to produce various paramagnetic phosphonates. The synthesized paramagnetic phosphonates proved to be useful synthetic building blocks for carbon-carbon bond-forming reactions in the Horner-Wadsworth-Emmons olefination reactions. The unsaturated compounds achieved could be transformed into various substituted pyrroline nitroxides, proxyl nitroxides and paramagnetic polyaromatics. The Trolox® equivalent antioxidant capacity (TEAC) of new phosphonates was also screened, and tertiary a-hydroxyphosphonatate nitroxides exhibited remarkable antioxidant activity.

Synthesis of 2,2,6-Trisubstituted 5-Methylidene-tetrahydropyran-4-ones with Anticancer Activity.

In our continuous search for new, relatively simple 2-alkylidene-1-oxoheterocycles as promising anticancer drug candidates, herein we report an efficient synthesis of 2,2,6-trisubstituted 5-methylidenetetrahydropyran-4-ones. These compounds were obtained in a four step reaction sequence, in which starting diethyl 2-oxopropylphosphonate was transformed into 2,2-disubstituted 5-diethoxyphosphoryldihydropyran-4-ones, followed by Michael addition of various Grignard reagents and Horner-Wadsworth-Emmons reaction of the obtained adducts with formaldehyde. Stereochemistry of the intermediate Michael adducts is also discussed. Final 5-methylidenetetrahydropyran-4-ones were tested for their possible antiproliferative effect against three cancer cell lines and 6-isopropyl-2,2-dimethyl-5-methylidenetetrahydropyran-4-one (11c), which showed very high cytotoxic activity against HL-60 human leukemia cells and was three times more active than known anticancer drug carboplatin, was selected for further biological evaluation, in order to disclose its mechanism of action. The obtained results indicated that 11c induced apoptosis in HL-60 cells and caused the arrest of the cell cycle in the G2/M phase, which may suggest its cytotoxic and cytostatic activity.

Inhibitory effects of N-(acryloyl)benzamide derivatives on tyrosinase and melanogenesis.

Targeting of tyrosinase has proven to be the best means of identifying safe, efficacious, and potent tyrosinase inhibitors for whitening skin. We designed and synthesized ten NAB (N-(acryloyl)benzamide) derivatives (1a-1j) using the Horner-Wadsworth-Emmons olefination of diethyl (2-benzamido-2-oxoethyl)phosphonate and appropriate benzaldehydes. A mushroom tyrosinase inhibitory assay showed compounds 1a (36.71 ±â€¯2.14% inhibition) and 1j (25.99 ±â€¯2.77% inhibition) inhibited tyrosinase more than the other eight NAB derivatives and kojic acid (21.56 ±â€¯2.93% inhibition), and docking studies indicated 1a (-6.9 kcal/mole) and 1j (-7.5 kcal/mole) had stronger binding affinities for tyrosinase than kojic acid (-5.7 kcal/mole). At a concentration of 25 µM, 1a and 1j were nontoxic in B16F10 melanoma cells and exhibited stronger tyrosinase inhibition (59.70% and 76.77%, respectively) than kojic acid (50.30% inhibition) or arbutin (41.78% inhibition at 400 µM). Similarly, in B16F10 melanoma cells, compounds 1a and 1j at 25 µM decreased total melanin content by 47.97% and 61.77%, respectively (kojic acid; 38.98%). Similarities between inhibitions of tyrosinase activity and melanin contents suggested the anti-melanogenic effects of 1a and 1j were due to tyrosinase inhibition. The excellent DPPH scavenging activity of 1j suggests it might enhance in vivo effect on melanin contents. The study suggests compound 1j offers a potential starting point for the development of safe, potent tyrosinase inhibitors.

Synthesis and Cytotoxic Evaluation of 3-Methylidenechroman-4-ones.

In the search for new anticancer agents, a library of variously substituted 3-methylidenechroman-4-ones was synthesized using Horner-Wadsworth-Emmons methodology. Acylation of diethyl methylphosphonate with selected ethyl salicylates furnished 3-diethoxyphosphorylchromen-4-ones which were next used as Michael acceptors in the reaction with various Grignard reagents. The adducts were obtained as the mixtures of trans and cis diastereoisomers along with a small amount of enol forms. Their relative configuration and preferred conformation were established by NMR analysis. The adducts turned up to be effective Horner-Wadsworth-Emmons reagents giving 2-substituted 3-methylidenechroman-4-ones, which were then tested for their possible cytotoxic activity against two leukemia cell lines, HL-60 and NALM-6, and against MCF-7 breast cancer cell line. All new compounds (14a-o) were highly cytotoxic for the leukemic cells and showed a moderate or weak effect on MCF-7 cells. Analog 14d exhibited the highest growth inhibitory activity and was more potent than carboplatin against HL-60 (IC50 = 1.46 ± 0.16 µM) and NALM-6 (IC50 = 0.50 ± 0.05 µM) cells. Further tests showed that 14d induced apoptosis in NALM-6 cells, which was mediated mostly through the extrinsic pathway.

Synthesis and kinetic evaluation of ethyl acrylate and vinyl sulfone derived inhibitors for human cysteine cathepsins.

A series of inhibitors targeting human cathepsins have been designed and synthesized following a combinatorial approach. The compounds bear an α,ß-unsaturated phenyl vinyl sulfone or ethyl acrylate warhead and a peptidomimetic portion aligned to the non-primed binding region. Biochemical evaluation toward four human cathepsins was carried out and the kinetic characterization confirmed an irreversible mode of inhibition. Compound 6c combining the most advantageous building blocks for cathepsin S inhibition was identified as a potent cathepsin S inactivator exhibiting a second-order rate constant of 30600 M-1 s-1.

Synthesis of 3-Methylidene-1-tosyl-2,3-dihydroquinolin-4(1H)-ones as Potent Cytotoxic Agents.

An efficient synthetic strategy to 3-methylidene-2,3-dihydroquinolin-4(1H)-ones variously substituted in position 2 has been developed. The title compounds were synthesized in the reaction sequence involving reaction of diethyl methylphosphonate with methyl 2-(tosylamino)benzoate, condensation of thus formed diethyl 2-oxo-2-(2-N-tosylphenyl)ethylphosphonate with various aldehydes followed by successful application of the obtained 3-(diethoxyphosphoryl)-1,2-dihydroquinolin-4-ols as Horner-Wadsworth-Emmons reagents for the olefination of formaldehyde. Also, enantioselective approach to the target compounds has been evaluated using 3-dimenthoxyphosphoryl group as a chiral auxiliary. Single X-ray crystal analysis of (2S)-3-(dimenthoxyphosphoryl)-2-phenyl-1-tosyldihydroquinolin-4-ol revealed the presence of strong resonance-assisted hydrogen bond (RAHB). The obtained 3-methylidene-2,3-dihydroquinolin-4(1H)-ones were then tested for their cytotoxic activity against two leukemia cell lines NALM-6 and HL-60 and a breast cancer MCF-7 cell line. All compounds showed very high cytotoxic activity with the IC50 values mostly below 1 µm in all three cancer cell lines. The selected analogs were also tested on human umbilical vein endothelial cells (HUVEC) and on human mammary gland/breast cells (MCF-10A) to evaluate their influence on normal cells. Since one of the most serious problems in cancer chemotherapy is the development of drug resistance, the mRNA levels and activity of ABCB1 transporter considered to be the most important factor engaged in drug resistance, were evaluated in MCF-7 cells treated with two selected analogs. Both compounds were strong ABCB1 transporter inhibitors that could prevent efflux of anticancer drugs from cancer cells.

Synthesis of fluorinated and nonfluorinated sugar alkenylphosphonates via highly stereoselective Horner-Wadsworth-Emmons olefination.

New fluorinated and nonfluorinated sugar alkenylphosphonates were obtained. In all cases 1,2;5,6-di-O-isopropylidene-α-d-glucofuranose was used as the starting material. The synthesis of alkenylphosphonates was based on Horner-Wadsworth-Emmons olefination. The process led to products with E-stereochemistry exclusively or predominately.

Stereoselective Synthesis and Anticancer Activity of 2,6-Disubstituted trans-3-Methylidenetetrahydropyran-4-ones.

In this report, we present efficient and stereoselective syntheses of 2,6-disubstituted trans-3-methylidenetetrahydropyran-4-ones and 2-(4-methoxyphenyl)-5-methylidenetetrahydropyran-4-one that significantly broaden the spectrum of the available methylidenetetrahydropyran-4-ones with various substitution patterns. Target compounds were obtained using Horner-Wadsworth-Emmons methodology for the introduction of methylidene group onto the pyranone ring. 3-Diethoxyphosphoryltetrahydropyran-4-ones, which were key intermediates in this synthesis, were prepared by fully or highly stereoselective addition of Gilman or Grignard reagents to 3-diethoxyphosphoryldihydropyran-4-ones. Addition occurred preferentially by axial attack of the Michael donors on the dihydropyranone ring. Relative configurations and conformations of the obtained adducts were assigned using a detailed analysis of the NMR spectra. The obtained methylidenepyran-4-ones were evaluated for cytotoxic activity against two cancer cell lines (HL-60 and MCF-7). 2,6-Disubstituted 3-methylidenetetrahydropyran-4-ones with isopropyl and phenyl substituents in position 2 were more cytotoxic than analogs with n-butyl substituent. Two of the most cytotoxic analogs were then selected for further investigation on the HL-60 cell line. Both analogs induced morphological changes characteristic of apoptosis in cancer cells, significantly inhibited proliferation and induced apoptotic cell death. Both compounds also generated DNA damage, and one of the analogs arrested the cell cycle of HL-60 cells in the G2/M phase. In addition, both analogs were able to inhibit the activity of topoisomerase IIα. Based on these findings, the investigated analogs may be further optimized for the development of new and effective topoisomerase II inhibitors.

Synthesis, stereochemical characterization, and antimicrobial evaluation of a potentially nonnephrotoxic 3'-C-acethydrazide puromycin analog.

Puromycin is a peptidyl nucleoside endowed with significant antibiotic and anticancer properties, but also with an unfortunate nephrotoxic character that has hampered its use as a chemotherapeutic agent. Since hydrolysis of puromycin's amide to puromycin aminonucleoside is the first metabolic step leading to nephrotoxicity, we designed a 3'-C-hydrazide analog where the nitrogen and carbon functionality around the amide carbonyl of puromycin are inverted. The title compound, synthesized in 11 steps from D-xylose, cannot be metabolized to the nephrotoxic aminonucleoside. Evaluation of the title compound on Staphylococcus epidermidis and multi-drug resistance Staphylococcus aureus did not show significant antimicrobial activity up to a 400 µM concentration.

Synthesis of 4,4-Disubstituted 3-Methylidenechroman-2-ones as Potent Anticancer Agents.

The synthesis of a new library of 4,4-disubstituted 3-methylidene-3,4-dihydro-2H-chroman-2-ones applying Horner-Wadsworth-Emmons methodology for the construction of an exo-methylidene moiety is reported. Corresponding 3-diethoxyphosphorylchroman-2-ones were synthesized in a three-step reaction sequence consisting of O-methylation of ethyl 2-diethoxyphosphoryl-3-oxoalkanoates, followed by reaction of the obtained 2-diethoxyphosphoryl-3-methoxy-2-alkenoates with phenols or 1-naphthol. The resulting 3-diethoxyphosphorylochromen-2-ones proved to be effective Michael acceptors in reactions with various Grignard reagents. Preliminary biological evaluations showed that many of the synthesized 3-methylidenechroman-2-ones possess very high cytotoxic activity against NALM-6 and HL-60 cancer cell lines (IC50 <1.0 µm) as well as high activity against the MCF-7 cancer cell line (IC50 <10 µm). Furthermore, two of the highly active 3-methylidenechroman-2-ones with geminal methyl and ethyl substituents at position 4 showed promising therapeutic indexes of 10 and 13 in tests against human umbilical vein endothelial cells (HUVECs).