Asymmetric synthesis of 1-(2- and 3-haloalkyl)azetidin-2-ones as precursors for novel piperazine, morpholine, and 1,4-diazepane annulated beta-lactams

A high-yielding, asymmetric synthesis of novel 4-formyl-1-(2- and 3-haloalkyl)azetidin-2-ones was developed as valuable starting materials for the synthesis of different enantiomerically enriched bicyclic azetidin-2-ones, such as piperazine, morpholine, and 1,4-diazepane annulated beta-lactam derivatives. Especially the hydride reduction of 4-imidoyl-1-(2- and 3-haloalkyl)azetidin-2-ones turned out to be an efficient and straightforward method for the preparation 2-substituted piperazines and 1,4-diazepanes.     

Thermoregulated Microemulsions by Cyclodextrin Sequestration: A New Approach to Efficient Catalyst Recovery

The combination of imidazolium surfactants with α‐cyclodextrins (CDs, in green) was used as a control element in the thermoregulated aqueous olefin hydroformylation. The self‐assembly of the imidazolium surfactants (red) favors the micellization process at high temperatures, whereas at lower temperatures the complexation of the surfactant monomers into the α‐CDs is favored.

     

Linear High Molar Mass Polyglycidol and its Direct α-Azido Functionalization

Summary: Linear polyglycidols with narrow chain dispersity and controlled high molar masses were prepared in a few hours by monomer-activated anionic polymerization of protected monomers, ethoxyethyl glycidyl ether and tert-butyl glycidyl ether, using a system composed of tetraoctylammonium bromide as initiator and triisobutylaluminum, used in 1.5 to 5-fold excess compared to the initiator, as co-initiator and monomer activator. This synthetic approach was shown to give various polyglycidol-based copolyethers in particular with propylene oxide or butene oxide. α-Azido,ω-hydroxy-poly(ethoxyethyl glycidyl ether) and other polyethers were directly prepared when tetrabutylammonium azide was used as initiator. Size exclusion chromatography and matrix-assisted laser desorption/ionization time-of-flight characterizations as well as “click” reactions were used to demonstrate the efficiency of the functionalization.     

Field Induced Stationary State for an Accelerated Tracer in a Bath

Our interest goes to the behavior of a tracer particle, accelerated by a constant and uniform external field, when the energy injected by the field is redistributed through collision to a bath of unaccelerated particles. A non equilibrium steady state is thereby reached. Solutions of a generalized Boltzmann-Lorentz equation are analyzed analytically, in a versatile framework that embeds the majority of tracer-bath interactions discussed in the literature. These results??mostly derived for a one dimensional system??are successfully confronted to those of three independent numerical simulation methods: a direct iterative solution, Gillespie algorithm, and the Direct Simulation Monte Carlo technique. We work out the diffusion properties as well as the velocity tails: large v, and either large ?v, or v in the vicinity of its lower cutoff whenever the velocity distribution is bounded from below. Particular emphasis is put on the cold bath limit, with scatterers at rest, which plays a special role in our model.     

Mueller matrix polarimetry for improved liver fibrosis diagnosis

An experimental Mueller matrix polarimeter is used to quantify human liver fibrosis by measuring retardance and depolarization of thin biopsies. The former parameter is sensitive to fibrillar collagen, the latter is specifically sensitive to fibrillar collagen around blood vessels, which is not significant for liver fibrosis diagnosis. By using depolarization like a filter, retardance distribution enables distinguishing between disease stages and limits the high degree of observer discrepancy.     

Controlled Decoration of [60]Fullerene with Polymannan Analogues and Amino Acid Derivatives through Malondiamide-Based Linkers

In the last few years, nanomaterials based on fullerene have begun to be considered promising tools in the development of efficient adjuvant/delivery systems for vaccination, thanks to their several advantages such as biocompatibility, size, and easy preparation and modification. In this work we reported the chemoenzymatic synthesis of natural polymannan analogues (di- and tri-mannan oligosaccharides characterized by α1,6man and/or α1,2man motifs) endowed with an anomeric propargyl group. These sugar derivatives were submitted to 1,3 Huisgen dipolar cycloaddition with a malondiamide-based chain equipped with two azido terminal groups. The obtained sugar-modified malondiamide derivatives were used to functionalize the surface of Buckminster fullerene (C₆₀) in a highly controlled fashion, and yields (11–41%) higher than those so far reported by employing analogue linkers. The same strategy has been exploited to obtain C₆₀ endowed with natural and unnatural amino acid derivatives. Finally, the first double functionalization of fullerene with both sugar- and amino acid-modified malondiamide chains was successfully performed, paving the way to the possible derivatization of fullerenes with immunogenic sugars and more complex antigenic peptides.     

Revealing Excited-State Trajectories on Potential Energy Surfaces with Atomic Resolution in Real Time

Photoexcited molecular trajectories on potential energy surfaces (PESs) prior to thermalization are intimately connected to the photochemical reaction outcome. The excited-state trajectories of a diplatinum complex featuring photo-activated metal–metal σ-bond formation and associated Pt−Pt stretching motions were detected in real time using femtosecond wide-angle X-ray solution scattering. The observed motions correspond well with coherent vibrational wavepacket motions detected by femtosecond optical transient absorption. Two key coordinates for intersystem crossing have been identified, the Pt−Pt bond length and the orientation of the ligands coordinated with the platinum centers, along which the excited-state trajectories can be projected onto the calculated PESs of the excited states. This investigation has gleaned novel insight into electronic transitions occurring on the time scales of vibrational motions measured in real time, revealing ultrafast nonadiabatic or non-equilibrium processes along excited-state trajectories involving multiple excited-state PESs.     

Statistical self-organization of an assembly of interacting walking drops in a confining potential

The European Physical Journal E - In this study, polyurethane (PU)-based xerogels were synthesized by using the biobased polyol derived from chaulmoogra seed oil. These polyol was used for the...     

Triggered Functional Dynamics of AsLOV2 by Time-Resolved Electron Paramagnetic Resonance at High Magnetic Fields

We present time-resolved Gd−Gd electron paramagnetic resonance (TiGGER) at 240 GHz for tracking inter-residue distances during a protein's mechanical cycle in the solution state. TiGGER makes use of Gd-sTPATCN spin labels, whose favorable qualities include a spin-7/2 EPR-active center, short linker, narrow intrinsic linewidth, and virtually no anisotropy at high fields (8.6 T) when compared to nitroxide spin labels. Using TiGGER, we determined that upon light activation, the C-terminus and N-terminus of AsLOV2 separate in less than 1 s and relax back to equilibrium with a time constant of approximately 60 s. TiGGER revealed that the light-activated long-range mechanical motion is slowed in the Q513A variant of AsLOV2 and is correlated to the similarly slowed relaxation of the optically excited chromophore as described in recent literature. TiGGER has the potential to valuably complement existing methods for the study of triggered functional dynamics in proteins.