Synthetic Diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylates Induce Apoptosis.

BACKGROUND: The Hantzsch ester, diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5- dicarboxylate, has been used as a hydride donor and its various biological effects have been reported. To identify chemotherapeutic agents with apoptotic effects, 21 diethyl 2,6-dimethyl-1,4- dihydropyridine-3,5-dicarboxylates were designed and synthesized; they have not been reported as apoptosis inducers thus far. Their structure-cytotoxicity relationships were investigated. Further biological experiments were performed on the title compound. METHODS: The cytotoxicities of the current synthetic compounds were measured using a clonogenic assay in HCT116 human colon cancer cells. An annexin V staining assay was used to confirm if the title compound induced apoptosis. To identify the synthetic compounds, Nuclear Magnetic Resonance (NMR) spectroscopy and high-resolution mass spectrometry (HR-MS) were conducted. As molecular symmetry was observed in the NMR spectroscopic data, the three dimensional structures were determined from ab initio calculations and X-ray crystallography. RESULTS: The results obtained from NMR spectroscopy, ab initio calculations, and X-ray crystallography revealed that the diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate derivatives synthesized in this research have symmetric structures. The cytotoxicities of the 21 derivatives were tested in the HCT116 human colon cancer cell lines, and their half-maximal cell growth inhibitory concentrations ranged between 16.29 and 68.88 µM. Structure-cytotoxicity relationships demonstrated that bulky substitutions were preferred, para-positioned substituents tended to have better cytotoxic values, and the polarity may have a function as well. The cytotoxicity of the title compound in HCT116 colon cancer cells was mediated through apoptotic cell death. CONCLUSION: To obtain chemotherapeutic agents that induce apoptosis, 21 diethyl 2,6-dimethyl- 1,4-dihydropyridine-3,5-dicarboxylates were designed and synthesized. NMR spectroscopy, ab initio calculations, and X-ray crystallography demonstrated that the diethyl 2,6-dimethyl-1,4- dihydropyridine-3,5-dicarboxylate derivatives synthesized in this research had symmetric structures. Even if the half-maximal cell growth inhibitory concentrations of the 21 derivatives did not show dramatic inhibitory activity against HCT116 human colon cancer cells, small changes in the structure affected the anticancer activities. Treatment with diethyl 4-(4-chlorophenyl)-2,6- dimethyl-1,4-dihydropyridine-3,5-dicarboxylate substantially reduced the cell viability and the cytotoxicity against HCT116 colon cancer cells was mediated through apoptotic cell death. As the ability of diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylates to induce apoptosis has not been previously reported, we have now reported their design, synthesis, cytotoxicity, and structureactivity relationships.

Synthesis and biological evaluation of 4,6-diphenyl-2-(1H-pyrrol-1-yl)nicotinonitrile analogues of crolibulin and combretastatin A-4.

A series of novel 4,6-diphenyl-2-(1H-pyrrol-1-yl)nicotinonitrile analogues of crolibulin and combretastatin A-4 (CA-4) were discovered using a 2-(1H-pyrrol-1-yl)pyridine ring as link-bridge to retain the cis-orientations of A-ring and B-ring. All the target compounds were synthesized and evaluated for their antiproliferative activity against five human cancer cell lines. Compounds 6a-d exhibited superior potency, with IC50 values at nanomolar levels. In particular, compound 6a exhibited antitumor activity similar to or higher than crolibulin and CA-4. Moreover, the inhibition of microtubule assembly by compound 6a was comparable to that by CA-4. A molecular modeling study of compound 6a was performed to elucidate its binding mode at the colchicine binding site in the tubulin dimer, which also provided a basis for further structure-guided design of novel colchicine binding site inhibitors.

6-Benzylidene-2-[4-(pyridin-3-ylcarboxy)benzylidene]cyclohexanones: A novel cluster of tumour-selective cytotoxins.

Novel cytotoxins 3-5 containing the 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore are disclosed. The compounds in series 3 and 5 have the potential to liberate niacin which may reduce some of the side effects of antineoplastic compounds. 3a-c emerged as the most potent cytotoxic compounds with IC50 values in the low micromolar range against human Molt4/C8 and CEM CD4+ T-lymphocytes as well as murine L1210 leukemia cells. QSAR studies revealed that cytotoxic potencies were negatively correlated with the magnitude of the Hammett sigma values of the aryl substituents. The compounds 3a-e displayed tumour-selective toxicity against human HL-60, HSC-2, HSC-3 and HSC-4 neoplasms as compared to human HGF, HPC and HPLF nonmalignant cells. A representative potent compound 3a caused PARP1 cleavage and G0/G1 cell cycle arrest in HSC-2 cells. These compounds are well tolerated in mice at doses up to and including 300mg/kg of the compounds and no mortalities were noted after 4h. The stability studies undertaken did not reveal that a representative compound 3a underwent hydrolysis to the related phenol 2a. Some guidelines for further analog development of the novel esters 3 were made.

Discovery of novel N-phenyl 1,4-dihydropyridines with a dual mode of antimycobacterial activity.

There is an urgent need for novel drugs for the treatment of tuberculosis (TB) due to the increasing prevalence of antibiotic resistance among Mycobacterium tuberculosis (Mtb) strains against first-line and second-line therapeutics. We developed novel N-phenyl 1,4-dihydropyridines as potential antituberculotic agents. The observed activity depends on the substitution patterns of the aromatic residues. N-unsubstituted 1,4-dihydropyridines are known inhibitors of the cancer-relevant transmembrane efflux pump ABCB1. Based on the similarity of ABCB1 amino acids sequences relevant to 1,4-dihydropyridine binding and the MTb efflux pump Rv0194, we determined ABCB1-inhibitory properties of our compounds in a cell line model. We identified one compound, which substantially increased the activity of two antituberculotic drugs which are substrates of ABCB1. The data indicate that our N-phenyl 1,4-dihydropyridines represent a novel compound class which improves the efficacy of anti-TB drugs by interfering with transmembrane efflux pumps in Mtb.

Structural Re-engineering of the α-Helix Mimetic JY-1-106 into Small Molecules: Disruption of the Mcl-1-Bak-BH3 Protein-Protein Interaction with 2,6-Di-Substituted Nicotinates.

The disruption of aberrant protein-protein interactions (PPIs) with synthetic agents remains a challenging goal in contemporary medicinal chemistry but some progress has been made. One such dysregulated PPI is that between the anti-apoptotic Bcl-2 proteins, including myeloid cell leukemia-1 (Mcl-1), and the α-helical Bcl-2 homology-3 (BH3) domains of its pro-apoptotic counterparts, such as Bak. Herein, we describe the discovery of small-molecule inhibitors of the Mcl-1 oncoprotein based on a novel chemotype. Particularly, re-engineering of our α-helix mimetic JY-1-106 into 2,6-di-substituted nicotinates afforded inhibitors of comparable potencies but with significantly decreased molecular weights. The most potent inhibitor 2-(benzyloxy)-6-(4-chloro-3,5-dimethylphenoxy)nicotinic acid (1 r: Ki =2.90 µm) likely binds in the p2 pocket of Mcl-1 and engages R263 in a salt bridge through its carboxylic acid, as supported by 2D (1) H-(15) N HSQC NMR data. Significantly, inhibitors were easily accessed in just four steps, which will facilitate future optimization efforts.

The rational design of a highly sensitive and selective fluorogenic probe for detecting nitric oxide.

A rationally designed small-molecule fluorogenic probe for nitric oxide (NO) detection based on a new switching mechanism has been developed. Attaching a NO-responsive dihydropyridine pendant group to a fluorophore led to a probe that displays a very high sensitivity to NO concentrations down to the low nM range and a very high specificity to NO while being insensitive to other oxidative oxygen/nitrogen species that often interfere with the sensing of NO.

Synthesis and anti-hypertensive effects of the twin drug of nicotinic acid and quercetin tetramethyl ether.

A novel twin drug consisting of nicotinic acid (VB3) and quercetin tetramethyl ether (QTME) has been synthesized as an antihypertensive in a total yield of 79.2% through methylation, hydrolysis, acylation and esterification starting from rutin. The structures of synthesized compounds were elucidated by 1H-NMR, 13C-NMR and elemental analysis. The anti-hypertensive effects of an oral daily dose (15 mg/kg) of the synthesized compounds in spontaneously hypertensive (SHR) rats and normotensive Wistar Kyoto (WKY) rats were analysed. The data demonstrate that the twin drug VB3-QTME both reduces the elevated blood pressure and prolongs the action time in SHR rats without effect on WKY rats. However, definitive evidence of a precise mechanism of action by which VB3-QTME might decrease blood pressure remains elusive. Based on the results, the therapeutic potential of this twin drug is discussed.

SPF32629A and SPF32629B: enantioselective synthesis, determination of absolute configuration, cytotoxicity and antibacterial evaluation.

We report herein an efficient enantioselective synthesis of SPF32629A and SPF32629B through one-pot enantioselective reduction and protecting-group-free regioselective O-acylation strategy. The absolute configuration of the enantiomerically pure isomers was established by Mosher ester analysis. The inhibitory potencies of the synthesized compounds were assayed in vitro against a panel of microorganisms and against A549 human lung adenocarcinoma cell line. Compounds 2, 11 and 12 displayed moderate to potent antibacterial activity against all the tested strains and compounds 7, 8, 2, 11 and 12 exhibited significant cytotoxicity in a dose-dependent manner with an IC50 values ranging from 2.92 to 4.14 µg/ml and 8-11 µM.

Nicotinic acid adenine dinucleotide phosphate analogues containing substituted nicotinic acid: effect of modification on Ca(2+) release.

Analogues of nicotinic acid adenine dinucleotide phosphate (NAADP) with substitution at either the 4- or the 5-position position of the nicotinic acid moiety have been synthesized from NADP enzymatically using Aplysia californica ADP-ribosyl cyclase or mammalian NAD glycohydrolase. Substitution at the 4-position of the nicotinic acid resulted in the loss of agonist potency for release of Ca(2+)-ions from sea urchin egg homogenates and in potency for competition ligand binding assays using [(32)P]NAADP. In contrast, several 5-substituted NAADP derivatives showed high potency for binding and full agonist activity for Ca(2+) release. 5-Azido-NAADP was shown to release calcium from sea urchin egg homogenates at low concentration and to compete with [(32)P]NAADP in a competition ligand binding assay with an IC(50) of 18 nM, indicating that this compound might be a potential photoprobe useful for specific labeling and identification of the NAADP receptor.

Synthesis of (aryloxyacetylamino)-isonicotinic/nicotinic acid analogues as potent hypoxia-inducible factor (HIF)-1alpha inhibitors.

We report a new series of HIF-1alpha inhibitors which were obtained through structural modifications of previously reported lead 1. The in vitro inhibitory potencies of newly synthesized compounds were evaluated against hypoxia-induced HIF-1 activation using cell-based reporter assay in three human cancer cell lines including SK-Hep-1, Hep3B, and AGS cells. Several compounds displayed significant inhibitory activity in all the three tested cell lines. In particular, analogue 17 displayed potent inhibition of hypoxia-induced accumulation of HIF-1alpha protein in Hep3B cell line, in addition to the dose-dependent inhibition of HIF-1 target genes VEGF and EPO.

Three-dimensional open frameworks based on cobalt(II) and nickel(II) m-pyridinecarboxylates.

Three-dimensional open frameworks [Co2(nicotinate)4(mu-H2O)]-CH3CH2OH-H2O, 1, and [Ni2(nicotinate)4(mu-H2O)]-CH3CH2OH-H2O, 2, were obtained by hydro(solvo)thermal reactions between 3-cyanopyridine and cobalt(II) nitrate and nickel(II) perchlorate, respectively. Both 1 and 2 exhibit complicated 3-D structures based on [M2(nicotinate)4(mu-H2O)] (M = Co or Ni) building blocks and possess open channels that are occupied by removable solvent molecules. 3-D open frameworks [M2L4(mu-H2O)]-HL-(H2O)x (where M = Co, x = 2, 3, and M = Ni, x = 1, 4, and L = trans-3-(3-pyridyl)acrylate) were similarly prepared with trans-3-(3-pyridyl)acrylic acid in place of 3-cyanopyridine. Compounds 3 and 4 are isostructural and exhibit network topologies similar to that of 1 with open channels occupied by disordered trans-3-(3-pyridyl)acrylic acid and water guest molecules. Crystal data for 1: triclinic space group Ponebar, a = 10.534(1) A, b = 11.907(1) A, c = 14.046(1) A, alpha = 106.645(1) degrees, beta = 101.977(1) degrees, gamma = 112.078(1) degrees, and Z = 4. Crystal data for 2: tetragonal space group P4/ncc, a = 20.089(1) A, c = 14.016(1) A, and Z = 4. Crystal data for 3: monoclinic space group C2/c, a = 14.082(2) A, b = 15.278(2) A, c = 18.537(2) A, beta = 105.360(2) degrees, and Z = 2. Crystal data for 4: monoclinic space group C2/c, a = 14.082(1) A, b = 15.250(1) A, c = 18.606(1) A, beta = 106.747(1) degrees, and Z = 2.

Nicotinylidene derivatives for the structural elucidation of glycerol mono-ethers and mono-esters by gas chromatography/mass spectrometry.

Nicotinylidene and methylnicotinylidene derivatives of representative glycerol ethers and glycerol esters were prepared by their reaction with pyridine-3-carboxaldehyde and 3-acetyl pyridine respectively. Each compound gave two sets of diastereoisomers which could be separated by gas-liquid chromatography. The extent of formation of the derivatives was nearly quantitative and chromatographic peak shape was good. The compounds producing both peaks gave similar spectra but with differences that were characteristic of the isomer. The derivatives fragmented in an analogous manner to that reported earlier for nicotinate derivatives of alcohols and picolinyl derivatives of carboxylic acids, with the production of a series of diagnostic ions formed by radical-induced cleavage of the chain following random hydrogen abstraction. Branched chain compounds, exemplified by glycerol ethers, gave spectra in which one of the ions diagnostic of the branch-point was missing. Unsaturated compounds, exemplified by the glycerol esters, gave characteristic mass spectra in which separation between ions representing formal cleavage at each side of the double bond enabled the position of this bond to be determined. In addition the spectra of unsaturated compounds contained two abundant ions whose formation could be rationalized by abstraction of the allylic hydrogen atoms. The nicotinylidene derivatives gave more diagnostic spectra than the methylnicotinylidene derivatives, whose spectra were complicated by the appearance of ions produced by loss of the methyl and pyridyl groups from the derivative. Both derivatives were superior to the nicotinate derivatives of these dihydroxy compounds in that only one pyridine residue was introduced on derivatization; this gave a lower molecular weight increment and allowed compounds with longer chains to be examined.(ABSTRACT TRUNCATED AT 250 WORDS)