Biocatalytic Enantioselective Synthesis of Atropisomers

[Image: see text] Atropisomeric compounds are found extensively as natural products, as ligands for asymmetric transition-metal catalysis, and increasingly as bioactive and pharmaceutically relevant targets. Their enantioselective synthesis is therefore an important ongoing research target. While a vast majority of known atropisomeric structures are (hetero)biaryls, which display hindered rotation around a C–C single bond, our group’s long-standing interest in the control of molecular conformation has led to the identification and stereoselective preparation of a variety of other classes of “nonbiaryl” atropisomeric compounds displaying restricted rotation around C–C, C–N, C–O, and C–S single bonds. Biocatalytic transformations are finding increasing application in both academic and industrial contexts as a result of a significant broadening of the range of biocatalytic reactions and sources of enzymes available to the synthetic chemist. In this Account, we summarize the main biocatalytic strategies currently available for the asymmetric synthesis of biaryl, heterobiaryl, and nonbiaryl atropisomers. As is the case with more traditional synthetic approaches to these compounds, most biocatalytic methodologies for the construction of enantioenriched atropisomers follow one of two distinct strategies. The first of these is the direct asymmetric construction of atropisomeric bonds. Synthetically applicable biocatalytic methodologies for this type of transformation are limited, despite the extensive research into the biosynthesis of (hetero)biaryls by oxidative homocoupling or cross-coupling of electron-rich arenes. The second of these is the asymmetric transformation of a molecule in which the bond that will form the axis already exists, and this approach represents the majority of biocatalytic strategies available to the synthetic organic chemist. This strategy encompasses a variety of stereoselective techniques including kinetic resolution (KR), desymmetrization, dynamic kinetic resolution (DKR), and dynamic kinetic asymmetric transformation (DYKAT). Nondynamic kinetic resolution (KR) of conformationally stable biaryl derivatives has provided the earliest and most numerous examples of synthetically useful methodologies for the enantioselective preparation of atropisomeric compounds. Lipases (i.e., enzymes that mediate the formation or hydrolysis of esters) are particularly effective and have attracted broad attention. This success has led researchers to broaden the scope of lipase-mediated transformations to desymmetrization reactions, in addition to a limited number of DKR and DYKAT examples. By contrast, our group has used redox enzymes, including an engineered galactose oxidase (GOase) and commercially available ketoreductases (KREDs), to desymmetrize prochiral atropisomeric diaryl ether and biaryl derivatives. Building on this experience and our long-standing interest in dynamic conformational processes, we later harnessed intramolecular noncovalent interactions to facilitate bond rotation at ambient temperatures, which allowed the development of the efficient DKR of heterobiaryl aldehydes using KREDs. With this Account we provide an overview of the current and prospective biocatalytic strategies available to the synthetic organic chemist for the enantioselective preparation of atropisomeric molecules

L’autobiographie au risque du plateau

Élisabeth Mazev dans Les Tribulations d’une étrangère d’origine Mise en scène : François Berreur © Raynaud de Lage Élizabeth Mazev, née en 1965, est célèbre avant tout comme actrice de théâtre : elle a joué dans bon nombre de mises en scène d’Olivier Py qu’elle connaît depuis l’école primaire. Elle a été l’in­terprète de Corneille, Racine, Marivaux, Giraudoux, Claudel, Ionesco, Valère Novarina, Lagarce, David Lescot ou Gregory Motton, sans que cette liste soit natu­rel­lement exhaustive. Par..

Receptor activator of nuclear factor-kappa B ligand (RANKL) directly modulates the gene expression profile of RANK-positive Saos-2 human osteosarcoma cells

Receptor activator of nuclear factor κB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) are the key regulators of bone metabolism. Recent findings demonstrated a crucial role of RANK in several bone-associated tumors. Indeed, we have recently demonstrated functional RANK expression both in a mouse and several human osteosarcoma cell lines. However, RANKL effects on osteosarcoma cells remain to be determined. In this study, we determined RANKL effects on RANK-positive Saos-2 human osteosarcoma cells. cDNA microarray and quantitative RT-PCR analyses clearly demonstrated that RANK-positive osteosarcoma cells were the target of RANKL as well as osteoclasts/osteoclast precursors. Thus, we present for the first time that RANKL can directly and significantly modulate gene expression of RANK-expressing Saos-2 cells. RANKL-modulated genes included genes that were implicated in protein metabolism, nucleic acid metabolism, intracellular transport, cytoskeleton organization and biogenesis, apoptosis and signaling cascade. Our results strengthen the involvement of the RANK/RANKL/OPG axis in osteosarcoma biology and capability to identify novel therapeutic approaches targeting RANK-positive osteosarcomas

Inhibition of BET proteins and epigenetic signaling as a potential treatment for osteoporosis

International audienceHistone modifications are important for maintaining the transcription program. BET proteins, an important class of " histone reading proteins " , have recently been described as essential in bone biology. This study presents the therapeutic opportunity of BET protein inhibition in osteoporosis. We find that the pharmacological BET protein inhibitor JQ1 rescues pathologic bone loss in a post-ovariectomy osteoporosis model by increasing the trabecular bone volume and restoring mechanical properties. The BET protein inhibition suppresses osteoclast differentiation and activity as well as the osteoblastogenesis in vitro. Moreover, we show that treated non-resorbing osteoclasts could still activate osteoblast differentiation. In addition, specific inhibition of BRD4 using RNA interference inhibits osteoclast differentiation but strongly activates osteoblast mineralization activity. Mechanistically, JQ1 inhibits expression of the master osteoclast transcription factor NFATc1 and the transcription factor of osteoblast Runx2. These findings strongly support that targeting epigenetic chromatin regulators such as BET proteins may offer a promising alternative for the treatment of bone-related disorders such as osteoporosis

Discrete pulses of molting hormone, 20-hydroxyecdysone, during late larval development ofDrosophila melanogaster: Correlations with changes in gene activity

Periodic pulses of the insect steroid molting hormone 20-hydroxyecdysone (20E), acting via its nuclear receptor complex (EcR/USP), control gene expression at many stages throughout Drosophila development. However, during the last larval instar of some lepidopteran insects, subtle changes in titers of ecdysteroids have been documented, including the so-called "commitment peak". This small elevation of 20E reprograms the larva for metamorphosis to the pupa. Similar periods of ecdysteroid immunoreactivity have been observed during the last larval instar of Drosophila. However, due to low amplitude and short duration, along with small body size and staging difficulties, their timing and ecdysteroid composition have remained uncertain. Employing a rigorous regimen of Drosophila culture and a salivary gland reporter gene, Sgs3-GFP, we used RP-HPLC and differential ecdysteroid RIA analysis to determine whole body titers of 20E during the last larval instar. Three small peaks of 20E were observed at 8, 20 and 28 hr following ecdysis, prior to the well-characterized large peak around the time of pupariation. The possible regulation of 20E levels by biosynthetic P450 enzymes and the roles of these early peaks in coordinating gene expression and late larval development are discussed

A Novel Ecdysone Receptor Mediates Steroid-Regulated Developmental Events during the Mid-Third Instar of Drosophila

The larval salivary gland of Drosophila melanogaster synthesizes and secretes glue glycoproteins that cement developing animals to a solid surface during metamorphosis. The steroid hormone 20-hydroxyecdysone (20E) is an essential signaling molecule that modulates most of the physiological functions of the larval gland. At the end of larval development, it is known that 20E—signaling through a nuclear receptor heterodimer consisting of EcR and USP—induces the early and late puffing cascade of the polytene chromosomes and causes the exocytosis of stored glue granules into the lumen of the gland. It has also been reported that an earlier pulse of hormone induces the temporally and spatially specific transcriptional activation of the glue genes; however, the receptor responsible for triggering this response has not been characterized. Here we show that the coordinated expression of the glue genes midway through the third instar is mediated by 20E acting to induce genes of the Broad Complex (BRC) through a receptor that is not an EcR/USP heterodimer. This result is novel because it demonstrates for the first time that at least some 20E-mediated, mid-larval, developmental responses are controlled by an uncharacterized receptor that does not contain an RXR-like component

Accès à des acides de Lewis par Umpolung de bases de Lewis chirales : applications en synthèse asymétrique

We explored the Umpolung of chiral enantiopure Lewis bases to access strongly Lewis acidic chiral fluorosulfoxonium and fluorophosphonium cations. The selected Lewis base must bear at least one external chirality element that is both chemically and configurationally stable under the applied reaction conditions in order to maintain a good control over the stereochemistry of the prepared acids. We evaluated the catalytic potential of the obtained Lewis acidic compounds. Despite their good activity, the possibility of inducing enantioselectivity using these species remains to be demonstrated. These results led us to question and study the true role of those Lewis acids in such catalysis. We developed an electrophilic mono-fluorination strategy for very weak Lewis bases. This strategy surpasses the previously described methodology, as it allows to access very strong Lewis acids in one step from substrates that were completely non-reactive under the standard Umpolung conditions. The Lewis acidity of the newly prepared fluorinated cations could be assessed by experimental and ab initio methods.Une méthodologie d’Umpolung de bases de Lewis chirales énantiopures permettant d’accéder à des cations fluorosulfoxonium et fluorophosphonium chiraux fortement acides de Lewis a été explorée. La base de Lewis choisie doit posséder au moins un élément de chiralité externe – chimiquement et configurationnellement stable dans les conditions réactionnelles appliquées – afin de garder un bon contrôle de la stéréochimie des acides préparés. Le potentiel en catalytise des composés acides de Lewis obtenus a été évaluée. Malgré de bonnes activités catalytiques, la possibilité d’induire de l’énantiosélectivité avec ces espèces en tant que catalyseurs reste encore à démontrer. Ces résultats nous ont conduit à questionner et étudier le rôle véritablement joué par ces acides de Lewis. Une stratégie de mono-fluoration électrophile directe de bases de Lewis très faibles a été mise au point. Cette stratégie surpasse la méthodologie décrite précédemment, puisqu’elle permet notamment d’accéder à des acides de Lewis très forts à partir de substrats parfois totalement inertes dans les conditions d’Umpolung classiques. L’acidité de Lewis des nouveaux cations fluorés ainsi préparés a pu être quantifiée par des méthodes expérimentales et ab initio

Impact économique des biosimilaires d'anti-TNFalpha à l'échelle des établissements adhérents du groupement de commandes PharmAlp'Ain

Mémoire de Diplôme d'Etudes Spécialisées (DES) tenant lieu de thèse d'exercice.The expenditures linked to the biosimilars consumption continue to increase, particularly with anti-TNF treatment, for several years, in hospital as well as in pharmacies. Despite reassuring clinical results and potential savings which represents their biosimilars marketing, the French health authorities have opted for a cautious approach concerning their using. They are recommanded for the initiation treatment. The aim of this memory was to evaluate the economic impact of anti-TNF biosimilars in the group orders of health products PharmAlp'Ain. In the first study, a using assessment of the original medicine and one biosimilar of infliximab, exclusively for hopsital use, was realised. Most of 77% of patients treated with biosimilar were initiation treatment. The others were maintenance therapy in patient treated by the original medicine. The competition induced by the tender allowed to save about 383 000 € including all taxes with these 2 drugs. The objective of the second study was to evaluate the potential economies for 2 futures anti-TNF biosimilars, etanercept and adalimumab, will be dispensed in pharmacies. If all patients were treated by biosimilars, the economies will be about 1 283 000 € by year from the viewpoint of Health Insurance. The arrival of biosimilars allows significant savings, which depends on the health staff's involvement, patient's adherence and authorities recommandations.Les dépenses liées à la consommation des biomédicaments, notamment des anti-TNFα, ne cessent de croître depuis plusieurs années, aussi bien en milieu hospitalier qu’en ville. Malgré des données cliniques rassurantes et les économies potentielles que représentent la commercialisation de leurs biosimilaires, les autorités de santé ont adopté une attitude prudente concernant leurs utilisations, en ne les recommandant que pour les initiations de traitements. L’objectif de ce travail a été d’évaluer l’impact économique des biosimilaires d’anti-TNFα à l’échelle des territoires de santé couverts par le groupement de commandes des produits pharmaceutiques PharmAlp’Ain. Dans une première étude, un bilan de l’utilisation du princeps et d’un biosimilaire de l’infliximab, médicaments réservés à l’usage hospitalier, a été réalisé. Plus de 77 % des patients traités par biosimilaire étaient des initiations, les autres étaient des poursuites chez des patients traités initialement par le princeps. Le jeu de la concurrence au cours de l’appel d’offres a permis d’économiser plus de 383 000 € TTC sur ces deux médicaments. La seconde étude avait pour objectif d’estimer les économies potentielles pour deux futurs biosimilaires d’anti-TNFα, l’etanercept et l’adalimumab, qui seront dispensés en ville. En cas de relais de l’ensemble des patients sous biosimilaires (naïfs et en poursuite), les économies obtenues permettraient d’économiser pour l’assurance maladie près de 1 283 000 € par an. L’arrivée des biosimilaires permet des économies conséquentes qui dépendent de l’implication des professionnels de santé, de l’adhésion des patients et des recommandations des tutelles