Geminally activated β-nitrostyrenes in reactions with cyclic β-diketones

The interaction of gem-benzoylnitroethenes and gem-alkoxycarbonylnitroethenes with cyclic β-diketones (dihydroresorcinol and dimedone) occurs as a one-pot process via sequential Ad_N and S_N steps followed by denitration to give functionally substituted hexahydrobenzofurans. The intermediate products of the nucleophilic addition have been isolated in the reactions of gem-acetylnitroethenes with dihydroresorcinol. The structures of the synthesized compounds have been confirmed by IR, ¹H, and ¹³C-{¹H} spectroscopy including the heteronuclear correlation experiments (¹H-¹³C HMQC and ¹H-¹³C HMBC).     

Stereochemistry in alkylations of dianions of β-hydroxysulfoxides and β-hydroxysulfones

Alkylations of dianions of β-hydroxysulfoxides and β-hydroxysulfones have been found to be affected by chelation of a Li cation with a sulfinyl group and by coordination of the cation with tetrahydrofuran rather than a sulfonyl group, respectively.     

Differences in cytotoxicity of β-sheet peptides originated from silk and amyloid β

The relationships between amino acid sequence, nano-assemblies, and cytotoxicity to neuron cytotoxicity were investigated using β-sheet-forming peptides from Araneus ventricosus spider silk, and amyloid forming peptides Aβ(12-28) (β1), Aβ(28-42) (β2), and full-length Aβ(1-42). Although silk derived peptides formed nano-assemblies, nanofilaments, and nanofibrils with β-sheet contents raging from 24 to 40%, they showed no significant cytotoxicity to neurons. In contrast, nano-assemblies and nanofibrils formed from Aβ peptides with high β-sheet content demonstrated cytotoxicity to the neurons. These differences in cell response between the silk β-sheets and Aβ peptides indicate that the general propensity to form beta sheets and form nanostructures is not sufficient to predict cytotoxicity, while surface charges of the assemblies are significant factors that impact cytotoxicity.     

Antioxidant activity of β-carotene compounds in different in vitro assays

β-Carotene (BC) is the most abundant carotenoid in human diet, almost solely as(all-E)-isomer. Significant amounts of (Z)-isomers of BC are present in processed food as well as in mammalian tissues. Differences are described for the activity of various BC isomers in forming retinal and protecting against cancer and cardiovascular diseases. Eccentric cleavage of BC leads to degradation products such as carotenals. A variety of negative consequences were published for the non-vitamin A active BC metabolites, such as inducing the carcinogenesis of benzo[a]pyrene, impairing mitochondrial function, or increasing CYP activity. To increase the knowledge on the antioxidant activity, a variety of BC isomers and metabolites were tested in various in vitro assays. In the present study, no ferric reducing activity (FRAP assay) was observed for the BC isomers. Between the major BC isomers (all-E, 9Z, and 13Z) no significant differences in bleaching the ABTS●+ (αTEAC assay) or in scavenging peroxyl radicals (ROO●) generated by thermal degradation of AAPH (using a chemiluminescence assay) were detected.However, the (15Z)-isomer was less active, maybe due to its low stability. The degradation to β-apo-carotenoids increased FRAP activity and ROO● scavenging activity compared to the parent molecule. Dependence on chain length and character of the terminal function was determined in αTEAC assay with following order of increasing activity: β-apo-8'-carotenal < β-apo-8'-carotenoic acid ethyl ester < 6'-methyl-β-apo-6'-carotene-6'-one (citranaxanthin). The results indicate that BC does not lose its antioxidant activity by degradation to long chain breakdown products.     

Advances in Detection Methods of β-Amyloid Protein

Alzheimer's disease (AD) is a neurodegenerative disease with unknown etiology. β-amyloid protein (Aβ) is one of the specific biomarkers of AD, and many clinical studies suggest that abnormal levels of Aβ in blood, cerebrospinal fluid and brain tissue are closely related to the progression of AD. The analysis and evaluation of Aβ are important for early detection, tracking, prevention, and treatment of AD. In this paper, the present situations of the commonly used detection methods of Aβ at home and abroad were summarized and compared. Specifically, the latest application of new electrochemical biosensor in Aβ detection was mainly described, and the summary of its future directions and the potential applications was given.     

Influence of β-substituents in aldol reactions of boron enolates of β-alkoxy methylketones

Moderate to good levels of substrate-based 1,5-syn-stereocontrol could be achieved in the boron-mediated aldol reactions of β-tert-butyl methylketones with achiral aldehydes, independent of the nature of the β-alkoxy protecting group (P = PMB or TBS). The analysis of the relative energies of the transition structures by theoretical calculations using the density functional B3LYP shows relative energies favoring the corresponding OUT-1,5-SYN transition structures, explaining the observed 1,5-syn stereoinduction.     

Temperature-dependent β-Crystal Growth in Isotactic Polypropylene with β-Nucleating Agent after Shear Flow

In our current work, the effect of the shear temperature on the growth of β-crystal in isotactic polypropylene(iPP) with β-nucleating agent is investigated by means of in situ two-dimensional wide-angle X-ray diffraction(2 D-WAXD). At low shear temperatures, the formed shear-induced oriented precursors are hard to relax back to random coiled state due to the weak mobility of molecular chains. Therefore, plenty of oriented α-crystals are induced by shear-induced oriented precursors, while β-crystal is greatly depressed. As the shear temperature increases, oriented β-crystal gradually increases along with the decrease of α-crystal. It is deduced that the shear temperature at which the content of β-crystal increases to the(maximum) value found in quiescent crystallization is almost the same as that at which the accelerating effect of flow on crystallization kinetics is completely erased. Our work manifests its significance in regulating β-crystal and thus in the structure and property manipulation of i PP.     

Reactivity of Alkoxy Radicals in β-Cleavage Reactions

The reactivity of alkoxy radicals in -cleavage reactions depends mostly on the nature of the leaving radical and not on the character of the arising ketone. The reactivity criteria based on isolated molecule approximation provide only qualitative relations. Yet the use of activation parameters calculated by quantum-chemical methods affords good quantitative correlations between the structure and the reactivity of alkoxy radicals in -cleavage reactions.     

Encapsulation of apple polyphenols in β-CD nanosponges

Rutin, phloridzin and chlorogenic acid are some of the most important and characteristic polyphenols found in apples and their by-products (cider, apple juice, apple pomace, etc.). Despite their antioxidant power, their low stability under light or heating conditions restricts the use of this kind of molecules as nutraceuticals. To deal with this issue, encapsulation seems to be an alternative solution. Based on the obtained results, it can be concluded that β-cyclodextrin nanosponges (β-CD NS) are promising agents for the encapsulation of polyphenols. Rutin, phloridzin and chlorogenic acid have been included for the first time in β-CD NS in this work. In particular, the highest encapsulation efficiency for rutin (83.7 %) was obtained using 1,1′-carbonyldiimidazole as cross-linker in a 1:3 ratio (nanosponge/cross-linker). However, for smaller molecules as phloridzin and chlorogenic acid, the nanosponge which showed the best results was the one with HMDI in a 1:8 ratio (87.2 and 77.5 %, respectively). In vitro dissolution studies of encapsulated polyphenols showed that rutin and phloridzin are better dissolved in ethanol, while chlorogenic acid is better dissolved in water. Besides, TGA, DSC, FTIR and XRPD were used as characterization techniques. Individual polyphenols and nanosponges, equimolar physical mixtures and synthesized complexes were characterized. Taking into account the obtained results, it can be confirmed that the solid products were not physical mixtures, but inclusion complexes. Thus, using these encapsulating agents, other polyphenols from apple and its by-products could be encapsulated in order to enhance their bioavailability.     

Towards β-selectivity in functional estrogen receptor antagonists

Based on the benzo[b]naphtho[1,2-d]furan and benzo[b]naphtho[1,2-d]thiophene frameworks, a series of ligands with different basic side chains (BSCs) has been synthesized and pharmacologically evaluated. Also, their binding modes have been modelled using docking techniques. It was found that the introduction of a BSC in these systems brings about a decrease of affinity for both estrogen receptors α and β in an in vitro competitive binding assay. However, two full antagonists of the estrogen receptor β ( and ) have been discovered, with potency in the low micromolar concentration in a cell-based luciferase reporter assay, and completely devoid of activity against the α receptor at the same concentration range. Differences in the ERα/ERβ binding modes have also been rationalized with the help of molecular modelling techniques. This interesting functional profile could be used to elucidate the physiological role of each ER subtype.     

Synthesis and Polymerization in Unsaturated Co β-Diketonates

Polymerization of some unsaturated -diketonates of cobalt containing double bonds both unconjugated and conjugated with a metal cycle. Unlike monomeric complexes, cobalt in metal-containing polymers was shown to have tetrahedral structure of the coordination polyhedron. The kinetic parameters of polymerization depend on electronic and steric properties of -diketonates.     

Inclusion Complexes of Conjugated Nitroolefins in β-Cyclodextrin

Physical studies such as Powder X-ray,FT-IR, UV, ¹H and ¹³C NMR clearly identifya 1 : 1 inclusion complex formed between-cyclodextrin and nitroolefins such as-nitrostyrene, 1-nitrocyclohexene in thesolid state as well as in solution. The olefins lieshallow inside the cavity leaving the nitro groupoutside the torus. It has been found that the complexis capable of reacting with a-phenyl-N-p-methylphenyl nitrone ina 1,3-dipolar cycloaddition with excellent rateacceleration and regioselection. The NaBH₄reduction of the complex in the solid state leads tothe corresponding nitroalkane.     

Mycelia-associated β-xylosidase in pellets ofAspergillus sps.

A screening of 10 strains ofAspergillus for pellet formation and mycelia-associated β-xylosidase activity was performed in media containing glucose and glucose supplemented with methyl β-d-xylopyranoside. The aim was to produce an immobilized enzyme preparation. Three strains with high mycelia-associated β-xylosidase activity were investigated for enzyme leakage and enzyme stability:A. terreus QM 1991,A. phoenicis ATCC 13157, andA. phoenicis QM 329. The pellets ofA. phoenicis QM 329 had the highest β-xylosidase activity (280 IU/g dry wt mycelia) after 333 h of incubation. From measurements of both cell-bound enzyme activity and the activity in solution, it could be concluded that forAspergillus phoenicis QM 329 and ATCC 13157 the decrease in β-xylosidase activity bound to the pellets was owing to enzyme leakage. ForAspergillus terreus QM 1991, the decrease of pellet-bound β-xylosidase activity was the result of both leakage and enzyme deactivation at 50°C. β-Xylosidase in pellets ofA. phoenicis QM329 hydrolyzes xylobiose andp-nitrophenyl β-d-xylopyranoside with the same rate of conversion.

     

Photo-responsive nanoparticles for β-lapachone delivery in vitro

We reported a one-step encapsulation of indocyanine green (ICG) in ZIF-8 nanoparticles (NPs). The as-prepared ICG@ZIF-8 NPs possess an absorption band in the near infrared region and have the good photothermal conversion efficiency.     

Electronic Structure and Chemical Bonding in β-Sialons

Using the discrete variation procedure we investigated the electronic structure, charge distributions, and chemical bonding in solid solutions of variable composition based on -Si₃N₄ with Si substituted by Al and N substituted by O (the general composition ). The electronic processes at the initial stage of SiAlON formation were studied (x = 1, 2) considering different distributions of Al–O pairs in the lattice of -Si₃N₄. The distribution mode of the dopant is found to be a more significant factor affecting the electronic structure of sialons compared to increased Al–O content; in particular, clusterization of dopant pairs leads to increased forbidden gap and splitting of the upper and lower valence bands. The results of calculations are used to interpret the systematic variations in the functional properties of -sialons depending on their chemical composition.     

Bonding in β-diketiminate boron and its analogues

Bonding analysis in β-diketiminate boron and related systems has been performed. For the optimized geometries (MP2/aug-cc-pVTZ), the post-SCF electron density function has been produced and its topological parameters have been analyzed according to Atoms in Molecules Quantum Theory approach. The B–N bond has characteristics similar to those found for TM–ligand bonding. The symmetric character of the B–N interaction found for the β-diketiminate boron results from the fully π-electron delocalized character of the β-diketiminate moiety. If the π-electron system in NCCCN sequence of bonds is localized, the asymmetric B–N bonding is enforced. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Synthesis of β-Amino Phosphonates in One-Pot Procedure

Abstract: β-amino phosphonate derivatives are synthesized in one-pot procedure via reduction of β-enamino phosphonate intermediates with NaBH₄/acetic acid or trifluoroacetic acid.     

Free-Radical Reaction Routes in γ-Irradiated β-D-Fructose

-Irradiated -D-fructose was studied over a wide temperature range (77–380 K) using EPR spectroscopy. A plausible scheme of the radiation-induced degradation of -D-fructose is proposed.     

Inclusion of the Antidepressant Paroxetine in β-cyclodextrin

The X-ray structure and thermal stability of a -cyclodextrin inclusion complex of the antidepressant paroxetine [(3S-trans)-3-[(1,3-benzodioxol-5-yloxy)methyl]-4-(4-fluorophenyl)piperidine], with the formula ( -cyclodextrin)₂...paroxetine...28H₂O, are reported. On heating, the crystals dehydrate in two stages and begin to decompose from approximately 270 °C. An X-ray diffraction study at 173K showed that the complex crystallizes in the monoclinic system, space group P2₁ with a = 15.2262(3), b = 31.4771(1), c = 15.6739(1) Å, = 104.320(1)° and Z = 2 formula units. Refinement on F² converged at R1 = 0.066, wR₂ = 0.182 (21478 reflections). On encapsulation within a head-to-head -cyclodextrin dimer, the paroxetine molecule adopts an unusual `hairpin' conformation, stabilised by intramolecular ... interaction between the phenyl rings. The guest piperidine ring is located at the primary face of one host molecule of the dimer while the fluorophenyl and benzodioxole moieties respectively occupy the dimer interfacial region and the cavity of the second host molecule. Experimental and computed X-ray powder diffraction patterns for the complex are also reported. The mode of stacking of the dimeric complex units is shown to be one of at least three distinct variants which can be identified for -cyclodextrin complexes with similar unit cell dimensions and crystallizing in the same space group.     

Angular dependence of the β-proton hyperfine coupling constant in β-substituted ethyl radicals

The β-proton hyperfine coupling constants in β-substituted ethyl radicals Ḣ₂-CH₂-X (X = CH₃, NH₂, OH, F, SiH₃, PH₂, SH, Cl) were computed as a function of the rotational angle α about the C_αC_β bond by ab initio calculations at the UHF/DZ + d level. They follow the relation a_H⨿(θ,α) = A + Bcos²θ + C cosθcosα, where A and B are not significantly affected by the substituent, and C is closely related to the electronegativity of the heteroatom.