Intramolecular benzyl protection delivery: a practical synthesis of DMDP and DGDP from D-fructose

[reaction: see text] A two-step protection of 1,2-diols as the corresponding o-xylylene cyclic ethers, involving an intramolecular ring-closing O-benzylation reaction, has been developed to overcome the problems associated to regioselective benzylation reactions. The strategy has been applied to the high-yielding synthesis of the pyrrolidine glycosidase inhibitors DMDP and DGDP.     

Synthesis and Structure of (CH3Si)6(NH)9: A Si–N Cage Made from Methyltrichlorosilane and Ammonia

No bulky substituents are bonded to the silicon centers of the cagelike title compound 1 , which is readily formed by reaction of methyltrichlorosilane with ammonia and sodium. According to X-ray structure analysis, 1 consists of two Si₃N₃ rings in the chair conformation that are bridged through the silicon centers by NH groups. The result is a cage in which three bars are missing, as can be seen on the right.     

Determination of the heat of hydride formation/decomposition by high-pressure differential scanning calorimetry (HP-DSC)

Among the thermodynamic properties of novel materials for solid-state hydrogen storage, the heat of formation/decomposition of hydrides is the most important parameter to evaluate the stability of the compound and its temperature and pressure of operation. In this work, the desorption and absorption behaviors of three different classes of hydrides are investigated under different hydrogen pressures using high-pressure differential scanning calorimetry (HP-DSC). The HP-DSC technique is used to estimate the equilibrium pressures as a function of temperature, from which the heat of formation is derived. The relevance of this procedure is demonstrated for (i) magnesium-based compounds (Ni-doped MgH2), (ii) Mg-Co-based ternary hydrides (Mg-CoHx) and (iii) Alanate complex hydrides (Ti-doped NaAlH4). From these results, it can be concluded that HP-DSC is a powerful tool to obtain a good approximation of the thermodynamic properties of hydride compounds by a simple and fast study of desorption and absorption properties under different pressures.     

Kinetic and Molecular Docking Studies to Determine the Effect of Inhibitors on the Activity and Structure of Fused G6PD::6PGL Protein from Trichomonas vaginalis

Trichomoniasis is a sexually transmitted disease with a high incidence worldwide, affecting 270 million people. Despite the existence of a catalog of available drugs to combat this infection, their extensive use promotes the appearance of resistant Trichomonas vaginalis (T. vaginalis), and some side effects in treated people, which are reasons why it is necessary to find new alternatives to combat this infection. In this study, we investigated the impact of an in-house library comprising 55 compounds on the activity of the fused T. vaginalis G6PD::6PGL (TvG6PD::6PGL) protein, a protein mediating the first reaction step of the pentose phosphate pathway (PPP), a crucial pathway involved in the parasite’s energy production. We found four compounds: JMM-3, CNZ-3, CNZ-17, and MCC-7, which inhibited the TvG6PD::6PGL protein by more than 50%. Furthermore, we determined the IC₅₀, the inactivation constants, and the type of inhibition. Our results showed that these inhibitors induced catalytic function loss of the TvG6PD::6PGL enzyme by altering its secondary and tertiary structures. Finally, molecular docking was performed for the best inhibitors, JMM-3 and MCC-7. All our findings demonstrate the potential role of these selected hit compounds as TvG6PD::6PGL enzyme selective inhibitors.     

Reversible Solvatomagnetic Switching in a Spongelike Manganese(II)–Copper(II) 3D Open Framework with a Pillared Square/Octagonal Layer Architecture

The concept of “molecular magnetic sponges” was introduced for the first time in 1999 by the creative imagination of the late Olivier Kahn. It refers to the exotic spongelike behavior of certain molecule‐based materials that undergo a dramatic change of their magnetic properties upon reversible dehydration/rehydration processes. Here we report a unique example of a manganese(II)–copper(II) mixed‐metal–organic framework of formula [Na(H₂O)₄]₄[Mn₄{Cu₂(mpba)₂(H₂O)₄}₃]? 56.5 H₂O ( 1 ) (mpba=N,N′‐1,3‐phenylenebis(oxamate)). Compound 1 possesses a 3D Mn^II₄Cu^II₆ pillared layer structure with mixed square and octagonal pores of approximate dimensions 1.2×1.2 nm and 2.1×3.0 nm, respectively, hosting a large amount of crystallization H₂O molecules and hydrated Na^I countercations as guests. It reversibly switches from a crystalline hydrated phase with long‐range ferromagnetic ordering at a rather high critical temperature (T_c) of 22.5 K to an amorphous dehydrated phase with T_c as low as 2.3 K, which is accompanied by a breathing‐type dynamic effect involving a large crystal volume (ca. 45 %) and color changes after water desorption/adsorption. The combination of both the open‐framework structure and the spongelike optical, mechanical, and magnetic switching behavior in this new class of oxamato‐based porous magnets offers fascinating possibilities in designing multifunctional materials for host–guest molecular sensing.     

New sesquiterpenes from Euonymus europaeus (Celastraceae)

A new sesquiterpene evoninate alkaloid (1), and two sesquiterpenes (2, 3) with a dihydro-beta-agarofuran skeleton, along with three known sesquiterpenes (4-6), were isolated from the seeds of Euonymus europaeus. Their structures were elucidated by high resolution mass analysis, and one- and two-dimensional (1D and 2D) NMR spectroscopy, including homonuclear and heteronuclear correlation [correlation spectroscopy (COSY), rotating frame Overhauser enhancement spectroscopy (ROESY), heteronuclear single quantum coherence (HSQC), and heteronuclear multiple bond correlation (HMBC)] experiments.     

Ring‐Opening Polymerization of Cyclic Esters by an Enantiopure Heteroscorpionate Rare Earth Initiator

With a sting in its tail : An enantiopure neodymium complex (see scheme) acts as an efficient single‐site initiator for the controlled ring‐opening polymerization of rac‐lactide, forming isotactic polyester. The heteroscorpionate complex was characterized spectroscopically and by X‐ray diffraction.

     

Rheology of ethyl cellulose solutions

Steady state flow and dynamic viscoelastic measurements of ethyl cellulose / m-Cresol solutions reveal the existence of an isotropic and anisotropic phase, as well as a biphasic interval. The effect of the applied shear rate is to shift the anisotropic phase to lower concentrations. The anisotropic phase, which is found from 20 wt.-% polymer concentration, is characterized by the following features: A) Three flow regions, pseudoplastic, Newtonian and pseudoplastic, respectively, are observed in $ \eta - \dot \gamma _{21} $ plots but not in η* - ω plots, b) “Grainy” and “thread” textures correspond to regions I and II respectively, c) Activation energies of flow are similar to that of the pure solvent, d) Both dynamic viscoelastic functions G′ and G″ scale with frecuency as ω^0.75, a dependence already observed in complex liquids, like heterogeneous block copolymers. On the other hand, dynamic viscoelastic measurements performed with isotropic systems allow to determine the entanglement modulus and the associated molecular weight between entanglement couplings, M_e⁰=7830.     

Interaction of human plasma fibrinogen with commercially pure titanium as studied with atomic force microscopy and X-ray photoelectron spectroscopy

The surface of a biomaterial interacts with the body fluid upon implantation in the human body. The biocompatibility of a material is strongly influenced by the adsorption of proteins onto the surface. Titanium is frequently used as a biomaterial for implants in orthopedics and cardiovascular devices. Understanding the biocompatibility is very important to improve implants. The surface chemistry of an implant material and its influence on the interaction with body fluid is crucial in that perspective. The main goal of this study was to investigate the conformation of human plasma fibrinogen (HPF) adsorbed on commercially pure titanium (CP Ti) on a molecular level by means of ex situ atomic force microscopy (AFM). With X-ray photoelectron spectroscopy combined with argon ion beam depth profiling, it was shown that the oxide layer present at the surface was mainly composed of TiO2, with a small percentage of Ti2O3. Ex situ AFM imaging showed the conformation of HPF on CP Ti. Single molecules and aggregates of fibrinogen were observed. The trinodular structure of single HPF molecules (two spherical D domains at the distal ends of the extended molecule and the central spherical E domain) adsorbed onto CP Ti was visualized. Aggregate formation through the connection of the D domains of the HPF molecules was observed on CP Ti. The alphaC domains of HPF were not visible on CP Ti. The ex situ AFM images indicated conformational changes of HPF upon adsorption onto CP Ti. The conformation of the adsorbed HPF molecules was different on mica and titanium. The difference in wettability between both substrates caused a larger spread of the protein on the CP Ti surface and thus resulted in a larger perturbation to the native structure of HPF as compared to mica.