N-tert-Butoxycarbonylation of amines using H3PW12O40 as an efficient heterogeneous and recyclable catalyst

The commercially available heteropoly acid H₃PW₁₂O₄₀ (0.5 mol %) is a very efficient and environmentally benign catalyst for N-tert-butoxycarbonylation of amines (primary, secondary) with di-tert-butyl dicarbonate at room temperature in short reaction times (<10 min). No competitive side products such as isocyanates, ureas, N,N-di-tert-butoxycarbonyls, O-Boc and oxazolidinones were observed. Chiral α-amino alcohols and esters afforded the corresponding N-Boc derivatives chemoselectively in excellent yields.     

2J(P,C) and 3J(P,C) Coupling Constants in Some New Phosphoramidates. Crystal Structures of CF3C(O)N(H)P(O)[N(CH3)(CH2C6H5)]2 and 4‐NO2‐C6H4N(H)P(O)[4‐CH3‐NC5H9]2

Some new phosphoramidates were synthesized and characterized by ¹H, ¹³C, ³¹P NMR, IR spectroscopy and elemental analysis. The structures of CF₃C(O)N(H)P(O)[N(CH₃)(CH₂C₆H₅)]₂ ( 1 ) and 4‐NO₂‐C₆H₄N(H)P(O)[4‐CH₃‐NC₅H₉]₂ ( 6 ) were confirmed by X‐ray single crystal determination. Compound 1 forms a centrosymmetric dimer and compound 6 forms a polymeric zigzag chain, both via ‐N‐H…O=P‐ intermolecular hydrogen bonds. Also, weak C‐H…F and C‐H…O hydrogen bonds were observed in compounds 1 and 6 , respectively. ¹³C NMR spectra were used for study of ²J(P,C) and ³J(P,C) coupling constants that were showed in the molecules containing N(C₂H₅)₂ and N(C₂H₅)(CH₂C₆H₅) moieties, ²J(P,C)>³J(P,C). A contrast result was obtained for the compounds involving a five‐membered ring aliphatic amine group, NC₄H₈. ²J(P,C) for N(C₂H₅)₂ moiety and in NC₄H₈ are nearly the same, but ³J(P, C) values are larger than those in molecules with a pyrrolidinyl ring. This comparison was done for compounds with six and seven‐membered ring amine groups. In compounds with formula XP(O)[N(CH₂R)(CH₂C₆H₅)]₂, ²J(P,CH₂)_benzylic>²J(P,CH₂)_aliphatic, in an agreement with our previous study.     

Zitterbewegung in External Magnetic Field: Classic versus Quantum Approach

We investigate variations of the Zitterbewegung frequency of electron due to an external static and uniform magnetic field employing the expectation value quantum approach, and compare our results with the classical model of spinning particles. We demonstrate that these two so far compatible approaches are not in agreement in the presence of an external uniform static magnetic field, in which the classical approach breaks the usual symmetry of free particles and antiparticles states, i.e. it leads to CP violation. Hence, regarding the Zitterbewegung frequency of electron, the classical approach in the presence of an external magnetic field is unlikely to correctly describe the spin of electron, while the quantum approach does, as expected. We also show that the results obtained via the expectation value are in close agreement with the quantum approach of the Heisenberg picture derived in the literature. However, the method we use is capable of being compared with the classical approach regarding the spin aspects. The classical interpretation of spin produced by the altered Zitterbewegung frequency, in the presence of an external magnetic field, are discussed.     

A Turn Off Fluorescence Probe Based on Carbon Dots for Highly Sensitive Detection of BRCA1 Gene in Real Samples and Cellular Imaging

Journal of Fluorescence - In this research, DNA-modified carbon dots (CDs) were exploited to construct a fluorescence assay for breast cancer genes (BRCA1, a potential marker for cancer diagnosis)...     

The Antioxidative Effects of Picein and Its Neuroprotective Potential: A Review of the Literature

Neurodegenerative diseases (NDDs) are the main cause of dementia in the elderly, having no cure to date, as the currently available therapies focus on symptom remission. Most NDDs will progress despite treatment and eventually result in the death of the patient after several years of a burden on both the patient and the caregivers. Therefore, it is necessary to investigate agents that tackle the disease pathogenesis and can efficiently slow down or halt disease progression, with the hope of curing the patients and preventing further burden and mortality. Accordingly, recent research has focused on disease-modifying treatments with neuroregenerative or neuroprotective effects. For this purpose, it is necessary to understand the pathogenesis of NDDs. It has been shown that oxidative stress plays an important role in the damage to the central nervous system and the progression of neurodegenerative disorders. Furthermore, mitochondrial dysfunction and the accumulation of unfolded proteins, including beta-amyloid (Aβ), tau proteins, and α-synuclein, have been suggested. Accordingly, cellular and molecular studies have investigated the efficacy of several natural compounds (herbs and nutritional agents) for their neuroprotective and antioxidative properties. The most popular herbs suggested for the treatment and/or prevention of NDDs include Withania somnifera (ashwagandha), ginseng, curcumin, resveratrol, Baccopa monnieri, and Ginkgo biloba. In some herbs, such as ginseng, preclinical and clinical evidence are available for supporting its effectiveness; however, in some others, only cellular and animal studies are available. In line with the scant literature in terms of the effectiveness of herbal compounds on NDDs, there are also other herbal agents that have been disregarded. Picein is one of the herbal agents that has been investigated in only a few studies. Picein is the active ingredient of several herbs and can be thus extracted from different types of herbs, which makes it more available. It has shown to have anti-inflammatory properties in cellular and plant studies; however, to date, only one study has suggested its neuroprotective properties. Furthermore, some cellular studies have shown no anti-inflammatory effect of picein. Therefore, a review of the available literature is required to summarize the results of studies on picein. To date, no review study seems to have addressed this issue. Thus, in the present study, we gather the available information about the antioxidative and potential neuroprotective properties of picein and its possible effectiveness in treating NDDs. We also summarize the plants from which picein can be extracted in order to guide researchers for future investigations.     

Local and global universal relations for first-gradient materials

Local universal relations are relations between stress and kinematic variables which hold for all materials of a particular class irrespective of specific material parameters. A method is developed for obtaining local universal relations for most first gradient materials. The currently known local universal relations for isotropic elastic materials have been extended to all isotropic first gradient materials under constant step deformation histories and have also been extended to all isotropic first gradient materials undergoing arbitrary time dependent triaxial extensions along fixed material directions. It has been shown that universal relations exist for some anisotropic materials. A set of pseudo-universal relations has been obtained for anisotropic elastic materials which can be used to decouple the material functions. These pseudo-universal relations contain some, but not all, material functions. A global universal relation has been developed for the extension and torsion of an isotropic cylindrical shaft which holds for all incompressible first gradient materials.     

Synthesis of narrow size distribution sub-micron TiO2 spheres

Ultra-fine spheres of TiO₂ are synthesized through sol-gel colloidal processing. Compared to previous studies, the present work shows a considerable achievement in controlling the shape of the produced particles as well as a relatively narrow size distribution.