B. Marquet

Meriolins (3-(pyrimidin-4-yl)-7-azaindoles): synthesis, kinase inhibitory activity, cellular effects, and structure of a CDK2/cyclin A/Meriolin complex

We report the synthesis and biological characterization of 3-(pyrimidin-4-yl)-7-azaindoles (meriolins), a chemical hybrid between the natural products meridianins and variolins, derived from marine organisms. Meriolins display potent inhibitory activities toward cyclin-dependent kinases (CDKs) and, to a lesser extent, other kinases (GSK-3, DYRK1A). The crystal structures of 1e (meriolin 5) and variolin B (Bettayeb, K.; Tirado, O. M.; Marionneau-Lambert, S.; Ferandin, Y.; Lozach, O.; Morris, J.; Mateo-Lozano, S.; Drückes, P.; Schächtele, C.; Kubbutat, M.; Liger, F.; Marquet, B.; Joseph, B.; Echalier, A.; Endicott, J.; Notario, V.; Meijer, L. Cancer Res. 2007, 67, 8325-8334) in complex with CDK2/cyclin A reveal that the two inhibitors are orientated in very different ways inside the ATP-binding pocket of the kinase. A structure-activity relationship provides further insight into the molecular mechanism of action of this family of kinase inhibitors. Meriolins are also potent antiproliferative and proapoptotic agents in cells cultured either as monolayers or in spheroids. Proapoptotic efficacy of meriolins correlates best with their CDK2 and CDK9 inhibitory activity. Meriolins thus constitute a promising class of pharmacological agents to be further evaluated against the numerous human diseases that imply abnormal regulation of CDKs including cancers, neurodegenerative disorders, and polycystic kidney disease.

Meriolins, a new class of cell death inducing kinase inhibitors with enhanced selectivity for cyclin-dependent kinases

Protein kinases represent promising anticancer drug targets. We describe here the meriolins, a new family of inhibitors of cyclin-dependent kinases (CDK). Meriolins represent a chemical structural hybrid between meridianins and variolins, two families of kinase inhibitors extracted from various marine invertebrates. Variolin B is currently in preclinical evaluation as an antitumor agent. A selectivity study done on 32 kinases showed that, compared with variolin B, meriolins display enhanced specificity toward CDKs, with marked potency on CDK2 and CDK9. The structures of pCDK2/cyclin A/variolin B and pCDK2/cyclin A/meriolin 3 complexes reveal that the two inhibitors bind within the ATP binding site of the kinase, but in different orientations. Meriolins display better antiproliferative and proapoptotic properties in human tumor cell cultures than their parent molecules, meridianins and variolins. Phosphorylation at CDK1, CDK4, and CDK9 sites on, respectively, protein phosphatase 1alpha, retinoblastoma protein, and RNA polymerase II is inhibited in neuroblastoma SH-SY5Y cells exposed to meriolins. Apoptosis triggered by meriolins is accompanied by rapid Mcl-1 down-regulation, cytochrome c release, and activation of caspases. Meriolin 3 potently inhibits tumor growth in two mouse xenograft cancer models, namely, Ewings sarcoma and LS174T colorectal carcinoma. Meriolins thus constitute a new CDK inhibitory scaffold, with promising antitumor activity, derived from molecules initially isolated from marine organisms.

Structure-Activity Relationship of S-Trityl-L-Cysteine Analogues as Inhibitors of the Human Mitotic Kinesin Eg5

The human kinesin Eg5 is a potential drug target for cancer chemotherapy. Eg5 specific inhibitors cause cells to block in mitosis with a characteristic monoastral spindle phenotype. Prolonged metaphase block eventually leads to apoptotic cell death. S-trityl-L-cysteine (STLC) is a tight-binding inhibitor of Eg5 that prevents mitotic progression. It has proven antitumor activity as shown in the NCI 60 tumor cell line screen. It is of considerable interest to define the minimum chemical structure that is essential for Eg5 inhibition and to develop more potent STLC analogues. An initial structure-activity relationship study on a series of STLC analogues reveals the minimal skeleton necessary for Eg5 inhibition as well as indications of how to obtain more potent analogues. The most effective compounds investigated with substitutions at the para-position of one phenyl ring have an estimated K i (app) of 100 nM in vitro and induce mitotic arrest with an EC 50 of 200 nM.

Anodic fluorination of vinyl sulfides-synthesis of α-fluoro-β-thio-α,β-unsaturated carbonyl compounds

A series of new title compounds 3 was synthesised in moderate to excellent yield, by anodic fluorination of their corresponding hudrogenated homologues 1 in Et3N,3HF/CH3CN, followed by a chemical dehydrofluorination step. From vinyl sulfides, we showed that anodically generated vicinal difluoro adducts 2 were easily dehydrofluorinated by an E1cB mechanism, leading to 3 with high stereoselectivity in most cases. In contrast, the anodic behaviour of a thio flavone in the same media was slightly different, giving rise to the formation of vinylic fluoride 3 during the anodic fluorination.

Diastereoselective fluorination at benzylic position by anodic oxidation

Abstract By anodic oxidation of benzylic derivatives 1 in Et3N,3HF/CH3CN, diastereoselective fluorination in the α position of the electron withdrawing group is obtained. The observed stereoselectivities are discussed in connection with the inductor group. The role of the anode is also examined.

Anodic functionalization of vinyl sulfides. Formal access to gem or vicinal aryl thioether dications

Abstract The anodic oxidation of a number of vinyl thioethers has been performed in CH 3 CN-Et 3 N,3HF. Results clearly show that the reactivity of the vinyl sulfide radical cation depends on several factors as structure of substrates and nucleophilic conditions. For example a dimerization occurred from the unsubstituted vinyl sulfide 1a (CH 2 =CH-SPh) whereas α,β- and/or β,β-difluoro sulfides were obtained from substituted homologues. In order to understand this reactivity the anodic behaviour of 1a and 1b (Ph-CH=CH-SPh) has been especially analysed in two other nucleophilic media (CH 3 OH/Et 3 N,3HF and AcOH/AcOK) leading respectively to methoxylation and acetoxylation of starting compounds. Comparison with electrofluorination results has allowed us to propose a mechanism involving an intermediary episulfonium ion which could explain the formation and ratio of the products isolated.

Le groupe thioéther: Un bon substituant pour les fluorations oxydatives

Abstract Regiospecific monofluorinations of α-thio α-Eirylesters and α-thioacids were obtained by anodic and/or chemical oxidation in fluorinating media. This procedure provided a convenient synthesis of α-fluoroesters via the C-S bond cleavage induced by anodic process while chemical or electrochemical oxidation of α-thioacids underwent a fluoro decarboxylation, affording α-fluorothioethers.

ETUDE DE LA REGIOSELECTIVITE EN FLUORATION ANODIQUE DE DERIVES BENZYLIQUES

By anodic oxidation of paramethylbenzylsulfonate, ester and nitrite 1 in Et3N,3HF/CH3CN, regioselective functionalization at benzylic positions is obtained (benzylic fluorides 2 and acetamides 3 are formed). In order to examin the determining factors of the chemioselectivity. It was compared to those obtained in bromination of the same compounds by 1,3-dibromo 5,5-dimethylhydantoin (DBH)/2.2′-azobis(isobutyronitrile) (AIBN) in CCl4.

Reaction of thioglycolate with α-fluoro-β-(phenylthio)enones (or -enals): Synthesis of substituted α-carboxy-γ-fluorothiophenes

Abstract A new synthetic method to substituted α-carboxy-γ-fluorothiophenes 2F is reported. They were prepared by the reaction between two equivalents of methyl thioglycolate anion and α-fluoro-β-(phenylthio)enones (or -enals) 1F , in DMSO (70°C) in yields ranging from 41% to 85%. We show from the reaction of (Z) -α-fluoro-β-(phenylthio)but-enone 1aF , that cyclisation to fluorothiophene 2aF occurs via the formation of stable enolates of α-fluoro-β-(dithianyl)butanone.

Electrofluorination of chiral substituted phenylacetic acid derivatives

Abstract Several recent works on the syntheses of chiral fluorinated organic molecules [P. Bravo and G. Resnati, Tetrahedron Asymmetry, 1 (1990) 661, and references therein] show that stereoselective introduction of this halogen remains an interesting challenge. In this communication, we wish to describe diastereoselective fluorination at benzylic position via an anodic process [Preliminary note: S. Chebli, R. Faure, L. Kabore, E. Laurent and B. Marquet, Tetrahedron Letters, 31 (1990) 3137]: The paper will include: • discussion about the efficiency of the inductor group R*, • determination of the absolute configuration of the fluorinated carbon using 19F NMR data of these compounds compared to spectra of esters derived from the unsubstituted acid of known configuration [C. Beguin, S. Hamman, L. Kabore, E. Laurent and B. Marquet, J. Fluorine Chem., in press], • considerations about the nature of the induction.