The Nitro Ketal Approach to Furane Systems. Total Synthesis of Racehic Bilobanone

Continuing our studies with the chemistry of ketals of β-nitro ketones¹, we wish to describe a new furane synthesis exemplified by a total synthesis of the sesquiterpene bilobanone 1 ².     

Stability and Bifurcation Analysis of a Spinning Space Tether

A detailed, geometrically exact bifurcation analysis is performed for a model of a power-generating tethered device of interest to the space industries. The structure, a short electrodynamic tether, comprises a thin, long rod that is spun in a horizontal configuration from a satellite in low Earth orbit, with a massive electrically conducting disk at its free end. The system is modelled using a Cosserat formulation leading to a system of Kirchhoff equations for the rod's shape as a function of position and time. Moving to a rotating frame, incorporating the effects of internal damping, intrinsic curvature due to the deployment method and novel force and moment boundary conditions at the contactor, the problem for steady rotating solutions is formulated as a two-point boundary value problem. Using numerical continuation methods, a bifurcation analysis is carried out varying rotation speeds up to many times the critical resonance frequency. Spatial finite differences are used to formulate the stability problem for each steady state and the corresponding eigenvalues are computed. The results show excellent agreement with earlier multibody dynamics simulations of the same problem.     

HPLC study of the efficiency of extraction of phenolic compounds

Summary The rate of extraction of phenolic compounds in two different solvents has been studied by liquid chromatography (HPLC) under reverse phase, gradient elution conditions. The solvents were diethyl ether and ethyl acetate. The method has been applied to two natural samples, a white wine and apple pulp.     

QSAR and conformational analysis of the antiinflammatory agent amfenac and analogues

Summary The new nonsteroidal antiinflammatory drug (NSAID) arylacetic amfenac (2-amino-3-benzoylphenylacetic acid) and 19 substituted derivatives were studied in order to correlate the biological activities with the structure-related parameters.The geometry of amfenac in neutral and anionic form was totally optimized, starting from standard geometries and crystallographic data, using semiempirical AM1 and MNDO quantum-mechanical methods. Conformational analysis shows the existence of a rigid structure for rotations of the acetic acid chain (°) and the central carbonyl group (°) around the bonds with the phenylamine ring, whereas the carboxyl group (°) and the phenyl ring of the benzoyl group (°) can rotate almost freely.Electrostatic potential maps were analyzed and showed that the electrostatic orientation effect seems to make an important contribution to the binding of the active compounds to prostaglandin synthase. An electrostatic orientation model of the binding site is proposed. The frontier orbital charge distribution was also described for each compound. On the other hand, steric, electronic and hydrophobic (log P) parameters were calculated and QSAR analysis showed that the most significant parameter for the antiinflammatory activity was the -electron density of the HOMO orbital in the second aromatic ring. These results suggest a possible electronic charge transfer between the aromatic fragments and the receptor.     

Interaction of graphene with antipsychotic drugs: Is there any charge transfer process?

Antipsychotics represent an effective therapy for schizophrenia (a chronic mental disorder). Their benefits are related to the interaction of the drugs with dopamine D2 receptor (D2R). Antipsychotics are classified as agonists or antagonists. One of the working hypotheses is that there is a charge transfer process between the drugs and the receptors, which is different for agonists and antagonists. To have more insight into the nature of the interaction of these molecules and the differences between agonists and antagonists, we analyze the interaction of graphene with three molecules: dopamine, pramipexole (an agonist of dopamine), and risperidone (an antagonist of dopamine). The idea is to use graphene as a simple model to analyze the charge transfer process of these three drugs. Optimized structures, atomic charges, and Density of States results indicate that global charges of dopamine and pramipexole are similar, while for risperidone, it is more than double. Pramipexole is an agonist, and the charge transfer process is similar to that of dopamine. Risperidone is an antagonist, and the charge transfer process is different from dopamine. The charge transfer is more significant with risperidone than with dopamine, and this could be related to the mechanism of action. This is in agreement with the working hypotheses that establish that it is possible to distinguish between agonists and antagonists since they have different capacity to transfer charge.     

Two Coordination Modes of CO in Zeolites: A Temperature-Dependent Equilibrium

CO interacts with exchangeable cations M⁺ (gray spheres in the picture) of zeolites to form M⁺⋅⋅⋅CO and M⁺⋅⋅⋅OC species (C: black; O: white) which are in a temperature-dependent equilibrium. For Na-ZSM-5 (M⁺=Na⁺) the difference in interaction energy amounts to 3.8 kJ mol⁻¹, as determined by means of variable-temperature FT-IR spectroscopy.     

Primary and secondary dielectric relaxations in semi-crystalline and amorphous starch

The thermally stimulated depolarization current technique, TSDC, has been used to study the dielectric relaxations in cassava starch on semi-crystalline and amorphous samples. The A-type structure was observed by WAXS experiments and the variation of the crystallinity as a function of the moisture content, h, was followed on native starch. Retrogradation of the amorphous sample occurred at room temperature after 4 weeks in a closed vessel with a water activity 97.3%. In these conditions the humidity content reached a value of 28.5 wt% dry base and the crystallinity degree was comparable to that of the native starch. Three secondary relaxation modes were detected and attributed to short range orientations of polar groups and to main chain restricted motion. The influence of the moisture plasticization effect on the relaxation parameters of the local modes, was determined by decomposing the global TSDC curve in elementary Debye peaks with Arrhenius relaxation times. The main relaxation, α, which is proposed to be the dielectric manifestation of the dynamic glass transition, sweeps a wide temperature interval around room temperature as the sample dries, shifting to higher temperatures as a result of the plasticization of the polysaccharide by water molecules. The α peak deconvolution lead to the 2D relaxation time distribution and Vogel-Tammann-Fulcher parameters were obtained confirming the cooperative character of this mode. The transformed sample showed a bimodal distribution of segmental relaxation times that is interpreted as the existence of a heterogeneous amorphous phase: the mobile one which is similar to the original disordered phase present in semi-crystalline native starch and a more restricted one originated by the disruption of the crystalline lamellae during the pre-gelatinization process.     

A complete TSDC description of molecular mobilities in polylactide/starch blends from local to normal modes: Effect of composition,moisture, and crystallinity

Thermally stimulated depolarization current is applied to study the dielectric relaxations coexisting from 80 to 380 K in the PLLA/starch, immiscible biodegradable blend system. The relaxation parameters are determined for chain mobilities at different ranges, whether in the amorphous or cold‐crystallized state for PLLA, and totally amorphous one for starch as demonstrated by wide‐angle X‐ray scattering experiments. The PLLA crystallization is favored by the presence of starch, in both the crystallinity degree reached and the crystallization time. The effect of moisture is followed for both the local modes and the segmental mobilities, where a bimodal relaxation for starch sweeps the temperature range, thus evidencing the heterogeneities existing in the starch disordered phase. The moisture plasticization effect is estimated and shows differences in the water absorption in starch either neat or as a minority component. The onset of the segmental mobility in PLLA is independent of composition or crystallinity, but the large intensity decrease observed when PLLA cold‐crystallizes evidences the simultaneous formation of a rigid amorphous fraction and the crystallites. The normal relaxation mode is recorded in amorphous PLLA whether neat or blended, which again demonstrates the absence of interactions among the blend components. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 680–691