Michel Gelbcke

Studies in NMR spectroscopy: The helicenes and lower benzologues☆☆☆★

Abstract This paper reports the results of a comparative study of the NMR spectra of phenanthrene to nonahelicene (I-VII, Fig. 1). The four spin systems present in these hydrocarbons (end rings) have been calculated and the corresponding protons (A, B, C, D) have been assigned on the basis of the coupling constants. These assignments are fully confirmed by the study of substituted derivatives, epi cross-ring couplings and specific solvent effects. The repercussion of the progressive overlap of benzene rings on the NMR spectra is discussed.

Structure-Based Design, Synthesis, and Pharmacological Evaluation of 3-(Aminoalkyl)-5-fluoroindoles as Myeloperoxidase Inhibitors

Oxidized low-density lipoproteins (LDLs) accumulate in the vascular wall and promote local inflammation, which contributes to the progression of the atheromatous plaque. The key role of myeloperoxidase (MPO) in this process is related to its ability to modify APO B-100 in the intima and at the surface of endothelial cells. A series of 3-(aminoalkyl)-5-fluoroindole analogues was designed and synthesized by exploiting the structure-based docking of 5-fluorotryptamine, a known MPO inhibitor. In vitro assays were used to study the effects of these compounds on the inhibition of MPO-mediated taurine chlorination and oxidation of LDLs. The kinetics of the interaction between the MPO redox intermediates, Compounds I and II, and these inhibitors was also investigated. The most potent molecules possessed a 4- or 5-carbon aminoalkyl side chain and no substituent on the amino group. The mode of binding of these analogues and the mechanism of inhibition is discussed with respect to the structure of MPO and its halogenation and peroxidase cycles.

DYRK1A Kinase Inhibitors with Emphasis on Cancer

Various types of cancers (including gliomas, melanomas, and esophageal, pancreas and non-small-cell lung cancers) display intrinsic resistance to pro-apoptotic stimuli, such as conventional chemotherapy and radiotherapy, and/or the activation of a multidrug resistance phenotype, which are major barriers to effective treatment and lead to poor patient prognosis. The DYRK1A kinase is directly implicated in the resistance of cancer cells to pro-apoptotic stimuli and drives several pathways that enhance proliferation, migration, and the reduction of cell death, leading to very aggressive biological behavior in cancer cell populations. The DYRK1A kinase is also implicated in neurological diseases and in neoangiogenic processes. Thus, the DYRK1A kinase is of great interest for both cancer and neuroscience research. During the last decade, numerous compounds that inhibit DYRK1A have been synthesized. The present review discusses the available molecules known to interfere with DYRK1A activity and the implications of DYRK1A in cancer and other diseases and serves as a rational analysis for researchers who aim to improve the anti-DYRK1A activity of currently available compounds.

Simple di- and trivanillates exhibit cytostatic properties toward cancer cells resistant to pro-apoptotic stimuli

A series of 33 novel divanillates and trivanillates were synthesized and found to possess promising cytostatic rather than cytotoxic properties. Several compounds under study decreased by >50% the activity of Aurora A, B, and C, and WEE1 kinase activity at concentrations <10% of their IC(50) growth inhibitory ones, accounting, at least partly, for their cytostatic effects in cancer cells and to a lesser extent in normal cells. Compounds 6b and 13c represent interesting starting points for the development of cytostatic agents to combat cancers, which are naturally resistant to pro-apoptotic stimuli, including metastatic malignancies.

Interaction between dipyridamole and eudragit S

Amorphous solid dispersions of dipyridamole were prepared by the solvent method using Eudragit S and RL as carriers in order to obtain controlled release dosage forms. When Eudragit S was used the release of dipyridamole from the solid dispersion particles was inhibited at low pH, but remarkably improved at neutral or alkaline pH values which correspond to the pH of polymer dissolution. In contrast, the dissolution of the active drug in acidic media was neither slowed down nor delayed when Eudragit RL was used as the carrying polymer. The striking difference between the drug release profiles of the two coprecipitates seemed to be caused by some interaction between Eudragit S and dipyridamole. The mechanism of this interaction was further investigated using various spectroscopic methods (UV, infrared, 1H- and 13C-NMR). The existence of preferential hydrogen bonding between the carboxylic functions of the polymer and some of the nitrogen atoms of dipyridamole was clearly demonstrated.

Structure-activity relationship analysis of bufadienolide-induced in vitro growth inhibitory effects on mouse and human cancer cells.

The in vitro growth inhibitory effects of 27 bufadienolides and eight degradation products, with two cardenolides (ouabain and digoxin) chosen as reference compounds, were analyzed by means of an MTT colorimetric assay in six human and two mouse cancer cell lines. A structure-activity analysis was then performed to highlight the most important substituents relating to the in vitro growth inhibitory activity of bufadienolides in cancer cells. Thus, the current study revealed that various bufadienolides, including gamabufotalin rhamnoside (1a), bufotalin (2a), and hellebrin (3a), displayed higher growth inhibitory activities for various human cancer cell lines when compared to ouabain and digoxin. Gamabufotalin rhamnoside (1a) was the only compound that displayed growth inhibitory effects of <1 μM in mouse cancer cells that expressed mutated forms of the Na(+),K(+)-ATPase α-1 subunit. In addition, all genins and degradation products displayed weaker (if any) in vitro growth inhibitory effects on cancer cells when compared to their respective glycosylated homologue, with the exception of hellebrigenin (3b), which was as active as hellebrin (3a).

N-(2-{3-[3,5-Bis(trifluoromethyl)phenyl]ureido}ethyl)-glycyrrhetinamide (6b): A Novel Anticancer Glycyrrhetinic Acid Derivative that Targets the Proteasome and Displays Anti-Kinase Activity.

18-β-Glycyrrhetinic acid (GA; 1) and many of its derivatives are cytotoxic in cancer cells. The current study aims to characterize the anticancer effects of 17 novel 1 derivatives. On the basis of these studies, N-(2-{3-[3,5-bis(trifluoromethyl)phenyl]ureido}ethyl)-glycyrrhetinamide (6b) appeared to be the most potent compound, with IC(50)in vitro growth inhibitory concentrations in single-digit micromolarity in a panel of 8 cancer cell lines. Compound 6b is cytostatic and displays similar efficiency in apoptosis-sensitive versus apoptosis-resistant cancer cell lines through, at least partly, the inhibition of the activity of a cluster of a dozen kinases that are implicated in cancer cell proliferation and in the control of the actin cytoskeleton organization. Compound 6b also inhibits the activity of the 3 proteolytic units of the proteasome. Compound 6b thus represents an interesting hit from which future compounds could be derived to improve chemotherapeutic regimens that aim to combat cancers associated with poor prognoses.

Spectres RMN-13C DE β-Aminoalcools Derives DE L'Ephedrine ET De Leurs Oxazolidines

Abstract The carbon-13 NMR spectra of β-aminoalcohols related to nor-and pseudonor-ephedrine (N-CH3; N-C2H5; N-iC3H7; N-tC4H9) and the series of the corresponding oxazolidines from formaldehyde and benzaldehyde were obtained and dicussed. The configuration of the 3-alkyl-2, 5-diphenyl-4-methyloxazolidines was established.

1H-nuclear magnetic resonance determination of the enantiomeric purity of aliphatic primary amines, β-aminoalcohols, β-diamines and α-amino-acids with 1R-(−)-myrtenal: scope and limitations

Abstract 1R-(−)-myrtenal was tested as a chiral derivatising agent for the determination of the enantiomeric purity of aliphatic primary amines, β-aminoalcohols, β-diamines and α-amino-acids. Derivatisation procedure consists in mixing one equivalent each of the amine and 1R-(−)-myrtenal directly into the nuclear magnetic resonance (NMR) tube before addition of the appropriate deuterated solvent and, for α-amino-acids, one equivalent of NaOH was added to neutralise the acidic function. Diastereoisomeric imines were completely formed after 12 h and analysed by 1H-NMR except for N-methyl β-diamines for which imidazolidines were obtained. The method gave satisfactory results only for α- and β-arylalkylamines for which CDCl3 could be advantageously replaced by C6D6 or pyridine-d5 in order to increase the difference between the chemical shifts. The main advantage of the procedure is its simplicity as it does not involve steps such as activation, heating, solvent evaporation and isolation of the product. Its limitations are the limited series of compounds susceptible to be analysed and the small difference between the chemical shifts of the diastereoisomeric imines obtained.

Structure-Activity Relationship Analyses of Glycyrrhetinic Acid Derivatives as Anticancer Agents

Cancer cell resistance to kinase inhibitors and targeted agents, acquisition of a multidrug-resistant (MDR) phenotype and/or intrinsic resistance to apoptosis prevent effective treatment in about 50% of solid cancers in adults, and the percentage is even higher in children. Glycyrrhetinic acid (GA) and some of its derivatives may offer hope in combating cancer types associated with poor prognoses. Some GA derivatives are indeed able to target both the proteasome and peroxisome proliferator-activated receptors (PPARs), two proteins that play major roles in cancer cell biology but are not related to MDR and/or apoptosis-related resistance phenotypes.