Rhazinilam-leuconolam family of natural products: a half century of total synthesis

Covering: 1972 to 2021The rhazinilam family of natural products exhibits a main structure with a stereogenic quaternary carbon and a tetrahydroindolizine core imbedded within a 9-membered macrocycle, imposing axial chirality. This unique architecture combined with their taxol-like antimitotic activities have attracted various attention, especially from synthetic chemists, notably in the past decade. The present review describes the known total and formal syntheses of the members of the rhazinilam family (rhazinilam, rhazinal, leuconolam and kopsiyunnanines), according to the strategy developed

Electron microscopy for inorganic-type drug delivery nanocarriers for antitumoral applications: What is possible to see?

The use of nanoparticles able to transport drugs, in a selective and controlable manner, directly to diseased tissues and cells have improved the therapeutic arsenal for addressing unmet clinical situations. In the recent years, a vast number of nanocarriers with inorganic, organic, hybrid and even biological nature have been developed, expecially for their application in oncology fied. The exponential growing in the nanomedicine field would not have been possible without the also rapid expansion of electron microscopy techniques, which allow a more precise observation of nanometric objects. The use of these techniques provides a better understanding of the key parameters which rule their synthesis and behavior. In this review, the recent advances performed in the application of inorganic nanoparticles for clinical uses and the role which has played electron microscopy will be presented

A revisit of the interaction of gaseous ozone with aqueous iodide. Estimating the contributions of the surface and bulk reactions

The main source of atmospheric iodine is the heterogeneous reaction of aqueous iodide (I‐ ) with ozone (O3), which takes place in surface seawater and probably in sea‐salt aerosols. However, there are seemingly contradictory conclusions about whether this heterogeneous reaction occurs in the bulk of the aqueous phase, via O3 dissolution, or at the aqueous surface, via O3 adsorption. In this work, the ozone uptake coefficient has been calculated as a function of the concentration of aqueous iodide ([I‐ ]aq) and gaseous ozone near the aqueous surface ([O3]gs) by estimating parameters of the resistor model using results of previous studies. The calculated uptake coefficients suggest that the aqueous‐phase reaction dominates at low I ‐ concentrations (about 10 ppm), regardless of [I‐ ]aq. In contrast, the surface reaction dominates at high [I‐ ]aq (about >10‐4 mol/L) as long as [O3]gs is low enough (about <10 ppm). This trend is able to reconcile previous studies of this reaction, and is a consequence of several factors, including the high surface excess of both reactants ozone and iodide. Given the typical O3 concentrations in the troposphere and the possible I ‐ concentrations and O3 solubilities in sea‐salt aerosols, the surface reaction may compete with the aqueous phase reaction in sea‐salt aerosols, unlike in surface seawater, where the aqueous‐phase reaction prevails. The rate constant of the surface reaction has been estimated as (5‐500)10^‐13 cm2 molecule‐1 s‐1

Reaction of OH radicals with CH3NH2 in the gas phase: experimental (11.7–177.5 K) and computed rate coefficients (10–1000 K)

Nitrogen-bearing molecules, like methylamine (CH3NH2), can be the building blocks of amino acids in the interstellar medium (ISM). At the ultralow temperatures of the ISM, it is important to know its gas-phase reactivity towards interstellar radicals and the products formed. In this work, the kinetics of the OH + CH3NH2 reaction was experimentally and theoretically investigated at low- and high-pressure limits (LPL and HPL) between 10 and 1000 K. Moreover, the CH2NH2 and CH3NH yields were computed in the same temperature range for both pressure regimes. A pulsed CRESU (French acronym for Reaction Kinetics in a Uniform Supersonic Flow) apparatus was employed to determine the rate coefficient, k(T), in the 11.7–177.5 K range. A drastic increase of k(T) when the temperature is lowered was observed in agreement with theoretical calculations, evaluated by the competitive canonical unified statistical (CCUS) theory, below 300 K in the LPL regime. The same trend was observed in the HPL regime below 350 K, but the theoretical k(T) values were higher than the experimental ones. Above 200 K, the calculated rate coefficients are improved with respect to previous computational studies and are in excellent agreement with the experimental literature data. In the LPL, the formation of CH3NH becomes largely dominant below ca. 100 K. Conversely, in the HPL regime, CH2NH2 is the only product below 100 K, whereas CH3NH becomes dominant at 298 K with a branching ratio similar to the one found in the LPL regime (≈70%). At T > 300 K, both reaction channels are competitive independently of the pressure regimeLas moléculas que contienen nitrógeno, como la metilamina (CH 3 NH 2 ), pueden ser los componentes básicos de los aminoácidos en el medio interestelar (ISM). A las temperaturas ultrabajas del ISM, es importante conocer su reactividad en fase gaseosa hacia los radicales interestelares y los productos formados. En este trabajo se investigó experimental y teóricamente la cinética de la reacción OH + CH 3 NH 2 a límites de baja y alta presión (LPL y HPL) entre 10 y 1000 K. Además, las reacciones CH 2 NH 2 y CH 3Los rendimientos de NH se calcularon en el mismo rango de temperatura para ambos regímenes de presión. Se empleó un aparato CRESU (acrónimo francés de Reaction Kinetics in a Uniform Supersonic Flow) pulsado para determinar el coeficiente de velocidad, k ( T ), en el rango de 11,7–177,5 K. De acuerdo con los cálculos teóricos, evaluados por la teoría de la estadística unificada canónica competitiva (CCUS), se observó un aumento drástico de k ( T ) cuando se baja la temperatura, por debajo de 300 K en el régimen LPL. La misma tendencia se observó en el régimen HPL por debajo de 350 K, pero el k teórico ( T) los valores fueron superiores a los experimentales. Por encima de 200 K, los coeficientes de velocidad calculados mejoran con respecto a estudios computacionales previos y están en excelente acuerdo con los datos de la literatura experimental. En el LPL, la formación de CH 3 NH se vuelve mayoritariamente dominante por debajo de ca. 100 K. Por el contrario, en el régimen HPL, CH 2 NH 2 es el único producto por debajo de 100 K, mientras que CH 3 NH se vuelve dominante a 298 K con una relación de ramificación similar a la encontrada en el régimen LPL (≈70%). A T > 300 K, ambos canales de reacción son competitivos independientemente del régimen de presión

Syn-cryptophanes: macrocyclic compounds with optimized characteristics for the design of 129 Xe NMR-based biosensors

International audienceA new water-soluble xenon host system with great promise for the 129 Xe NMR-based biosensing approach is presented: the syn-cryptophane-222-hexacarboxylate. It compares favorably with its already known anti diastereomer, on the one hand, and with cucurbit[6]uril, on the other hand, in particular in terms of xenon binding constant and xenon in-out exchange, a key parameter for the efficiency of the most sensitive HyperCEST method

Selection of green solvents for organic photovoltaics by reverse engineering

International audienceFor a sustainable scale-up of solution-processed organic photovoltaic modules, the replacement of toxic solvents, generally used at laboratory scale, by alternative "green" solvents with a reduced impact on the environment and human health is a critical prerequisite. Yet, because of the complex relationship between solvent properties and device performance, the selection of alternative solvents relies primarily on time-consuming and costly trial-and-error approaches. In this work we propose a new methodology involving prediction of molecular properties and reverse design for a more efficient and less empirical selection of green and bio-sourced solvents. The method is applied to four different small molecule-and polymer based donor-acceptor blends. It allows to establish lists of possible alternative solvents ranked quantitavely by a global performance function encompassing all target properties. The actual performance of the highest ranked solvents are evaluated by using the selected solvents to elaborate photovoltaic devices and comparing the power conversion efficiencies with those obtained with devices processed from halogenated solutions. In all cases, the photovoltaic performances obtained with the alternative solvents are similar or superior to those of the standard devices, confirming the relevance of the new solvent selection method for solution-processed organic photovoltaic devices

Generation and nature of water-tolerant Lewis acid sites in In x Sn 10− x O y /Al 2 O 3 catalysts as active centers for the green synthesis of methyl lactate from glucose

International audienceGeneration and nature of water-tolerant Lewis acid sites in In x Sn 10-x O y /Al 2 O 3 catalyst as active centers for green synthesis of methyl lactate from glucos

Flow synthesis of an α-amino boronic ester as key precursor of Bortezomib drug

International audienceThe flow synthesis of the optically active α-amino boronate precursor of the bortezomib drug is described, including a key diastereoselective Matteson rearrangement

Tailoring the SWIR emission of gold nanoclusters by surface ligand rigidification and their application in 3D bioimaging

International audienceThe influence of solvent polarity and surface ligand rigidification on the SWIR emission profile of gold nanoclusters with an anistropic surface was investigated. A strong enhancement of the SWIR emission band at 1200 nm was observed when measuring in different local environments: in solution, in polymer composites, and in solids. SWIR in vivo imaging of mice assisted by deep learning after intravenous administration of these gold nanoclusters provides high definition pseudo-3D views of vascular blood vessels

Biomimetic catalysis of nitrite reductase enzyme using copper complexes in chemical and electrochemical reduction of nitrite

International audienceCopper nitrite reductase mimetics were synthesized using three new tridentate ligands sharing the same N,N,N motif of coordination. The ligands were based on L-proline modifications, attaching a pyridine and a triazole to the pyrrolidine ring, and differ by a pendant group (R = phenyl, n-butyl and n-propan-1-ol). All complexes coordinate nitrite, as evidenced by cyclic voltammetry, UV-Vis, FTIR and electron paramagnetic resonance (EPR) spectroscopies. The coordination mode of nitrite was assigned by FTIR and EPR as κ2O chelate mode. Upon acidification, EPR experiments indicated a shift from chelate to monodentate κO mode, and 15N NMR experiments of a Zn2+ analogue, suggested that the related Cu(II) nitrous acid complex may be reasonably stable in solution, but in equilibrium with free HONO under non catalytic conditions. Reduction of nitrite to NO was performed both chemically and electrocatalytically, observing the highest catalytic activities for the complex with n-propan-1-ol as pendant group. These results support the hypothesis that a hydrogen bond moiety in the secondary coordination sphere may aid the protonation step