Triphenylphosphine‐Mediated Reduction of Electron‐Deficient Propargyl Ethers to the Allylic Ethers

Semihydrogenation of α,β‐unsaturated ynoates and ‐ynones bearing a γ‐alkoxy group can be performed using triphenylphosphine and water. α,β‐Unsaturated ynoates were reduced to a mixture of cis and trans α,β‐unsaturated enoates, whereas, ynones were reduced to trans α,β‐unsaturated enones as the only products.     

Soy Isoflavones Inhibit Both GPIb-IX Signaling and αIIbβ3 Outside-In Signaling via 14-3-3ζ in Platelet

Soy diet is thought to help prevent cardiovascular diseases in humans. Isoflavone, which is abundant in soybean and other legumes, has been reported to possess antiplatelet activity and potential antithrombotic effect. Our study aims to elucidate the potential target of soy isoflavone in platelet. The anti-thrombosis formation effect of genistein and daidzein was evaluated in ex vivo perfusion chamber model under low (300 s⁻¹) and high (1800 s⁻¹) shear forces. The effect of genistein and daidzein on platelet aggregation and spreading was evaluated with platelets from both wildtype and GPIbα deficient mice. The interaction of these soy isoflavone with 14-3-3ζ was detected by surface plasmon resonance (SPR) and co-immunoprecipitation, and the effect of αIIbβ3-mediated outside-in signaling transduction was evaluated by western blot. We found both genistein and daidzein showed inhibitory effect on thrombosis formation in perfusion chamber, especially under high shear force (1800 s⁻¹). These soy isoflavone interact with 14-3-3ζ and inhibited both GPIb-IX and αIIbβ3-mediated platelet aggregation, integrin-mediated platelet spreading and outside-in signaling transduction. Our findings indicate that 14-3-3ζ is a novel target of genistein and daidzein. 14-3-3ζ, an adaptor protein that regulates both GPIb-IX and αIIbβ3-mediated platelet activation is involved in soy isoflavone mediated platelet inhibition.     

The Amyloid Fibril-Forming β-Sheet Regions of Amyloid β and α-Synuclein Preferentially Interact with the Molecular Chaperone 14-3-3ζ

14-3-3 proteins are abundant, intramolecular proteins that play a pivotal role in cellular signal transduction by interacting with phosphorylated ligands. In addition, they are molecular chaperones that prevent protein unfolding and aggregation under cellular stress conditions in a similar manner to the unrelated small heat-shock proteins. In vivo, amyloid β (Aβ) and α-synuclein (α-syn) form amyloid fibrils in Alzheimer’s and Parkinson’s diseases, respectively, a process that is intimately linked to the diseases’ progression. The 14-3-3ζ isoform potently inhibited in vitro fibril formation of the 40-amino acid form of Aβ (Aβ₄₀) but had little effect on α-syn aggregation. Solution-phase NMR spectroscopy of ¹⁵N-labeled Aβ₄₀ and A53T α-syn determined that unlabeled 14-3-3ζ interacted preferentially with hydrophobic regions of Aβ₄₀ (L11-H21 and G29-V40) and α-syn (V3-K10 and V40-K60). In both proteins, these regions adopt β-strands within the core of the amyloid fibrils prepared in vitro as well as those isolated from the inclusions of diseased individuals. The interaction with 14-3-3ζ is transient and occurs at the early stages of the fibrillar aggregation pathway to maintain the native, monomeric, and unfolded structure of Aβ₄₀ and α-syn. The N-terminal regions of α-syn interacting with 14-3-3ζ correspond with those that interact with other molecular chaperones as monitored by in-cell NMR spectroscopy.     

Diffusion Measurements vs. Chemical Shift Titration for Determination of Association Constants on the Example of Camphor–Cyclodextrin Complexes

Measurements on camphor–cyclodextrin complexes reveal that precise association constants are more easily determined by chemical shift titration. Diffusion measurements using HR-DOSY allow easy following of the complex composition at different concentration ratios and estimation of the binding energy. Linear dependence of the diffusion coefficients on the molecular mass of free and associated cyclodextrins has been observed in D₂O. The solution structures of α- and β-cyclodextrin complexes of camphor in D₂O were deduced from intermolecular cross-relaxation data. Different preferential orientation in the 2:1 α-CD and 1:1 β-CD species have been derived in contrast to the loose 1:1 complex with γ-CD. Proton NMR chemical shift values proved to be much more sensitive to diastereomeric complex formation than diffusion coefficients.     

The antioxidant role of α-tocopherol in polymers. I. The nature of transformation products of α-tocopherol formed during melt processing of LDPE

The antioxidant role of α-tocopherol (vitamin E) in low-density polyethylene (LDPE), and the nature of its transformation products formed during extrusion of the polymer are investigated. The melt stabilizing effectiveness of α-tocopherol was found to be very high, higher than that of the commercial hindered phenol antioxidants, Irganox 1076 and 1010, after single and multiple extrusion. The high antioxidant activity of α-tocopherol as a melt stabilizer is due, at least in part, to its transformation products. The importance of the processing history and the parent antioxidant concentration on the transformation products is discussed. Transformation products of α-tocopherol were analyzed after each of the four extrusion passes of the polymer. These were fractionated, analyzed, and characterized by HPLC and spectroscopy, respectively. The main products formed are diastereoisomers of dimers and trimers, as well as aldehydes; the relative concentration of each was shown to depend on processing severity (number of extrusion passes) and the initial concentration of α-tocopherol. The dihydroxydimer was found to be formed at a high concentration relative to the other products and proportional with the initial concentration of tocopherol. Based on both the identity and distribution of transformation products, a mechanism is proposed for the melt stabilization effect of α-tocopherol in LDPE. © 1994 John Wiley & Sons, Inc.     

Reactions of 3, 5-Dimethyl-4-Carbethoxy-2-Cyclohexen-1-One at α-Position

3, 5-Dimethyl-4-carbethoxy-2-cyclohexen-1-one has been synthesized through the Knoevenagel condensation¹, which is then subjected to alkylation and acylation at α-position. The resulting products are hydrolyzed and decarboxylated to α-substituted cyclohexenones. 3, 5-Dimethyl-2-cyclohexen-1-one is converted by N-bromosuccinimide to phenol via enolization².     

A Novel Method for the Synthesis of α,β‐Unsaturated Amides Mediated by Samarium Diiodide

Promoted by Samarium diiodide (SmI₂), α,β‐unsaturated amides were formed from nitrogen anions (formed in situ by the reduction of nitro compounds) and α,β‐unsaturated esters. This reaction contrasts with the conjugate addition between amines and α,β‐unsaturated esters promoted by samarium triiodide (SmI₃) and provides an alternative attractive way to obtain α,β‐unsaturated amides using SmI₂.     

Synthesis of Phenanthrene Derivatives through the Reaction of an α,α‐Dicyanoolefin with α,β‐Unsaturated Carbonyl Compounds

Phenanthrene derivatives were prepared by reacting an α,α‐dicyanoolefin with different α,β‐unsaturated carbonyl compounds resulting from Wittig reaction of ninhydrin and phosphanylidene or condensation of barbituric acid and an aldehyde. The easy procedure, mild and metal‐catalyst free, reaction conditions, good yields, and no need for chromatographic purifications are important features of this protocol. The structures of the product of type 3 and 5 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Scheme 1).     

A Mild Isomerization Reaction for β,γ‐Unsaturated Ketone to α,β‐Unsaturated Ketone

A series of β,γ‐unsaturated ketones were isomerized to their corresponding α,β‐unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo‐cyclic double bond (β,γ‐position) on ketone was rearranged to exo‐cyclic double bond (α,β‐position) under the reaction conditions.     

Polymer-Attached Thiazolium Salts-Catalyzed Addition of Aldehydes to α, β-Unsaturated Carbonyl Compounds

A homogeneous catalyst, 3-benzyl-5-(2-hydroxyethyl)-4-methyl-1,3-thiazolium chloride, for addition of aldehydes to activated double bond, was attached to 20% cross-linked polystyrene-divinylbenzene copolymer. The attached catalysts could be easily removed from the reaction mixture. Polymer-attached thiazolium salts in the presence of triethylamine are active catalysts for addition of aromatic and aliphatic aldehydes to α,β-unsaturated ketones to yield γ-diketones.     

Perceived color of undoped electrospun polyacrylonitrile nanofibers

This work reveals influence of electrospinning of polyacrylonitrile–N ,N‐dimethylformamide solution of different concentrations on nanofiber web color parameters, molecular structure, and heat stability. It is found that fiber diameters depend on concentration through the power law relationship; however, the medium concentration‐based web is characterized by a green–yellow hue, representative of the chromophore color; while, the solvent‐rich and solvent‐poor solution‐based webs give rise to Stokes shifts and ultraviolet‐blue emission bands, attributed to fluorescence. The chromophore structure, present in the neat powder, undergoes changes as a result of electrospinning reflected by the enamine‐to‐ketonitrile conversion and the fraction of C?N conjugation. Blue‐shifting of the C?N conjugation is indicative of a reduction of the π‐electron system, which is coincident with the decreased color saturation value but observed only in the nanofibers prepared from the medium concentration solution. A decrease in the glass transition and an increase in cyclization temperatures also support these findings. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1278–1285     

A novel type of optically active helical polymers: Synthesis and characterization of poly(α,β‐unsaturated ketone)

New α,β‐unsaturated ketone monomers, menthyl vinyl ketone (MVK), and 1‐menthylbut‐3‐en‐2‐one (MBEK) were synthesized. The monomers were polymerized using butyllithium as an initiator. The polymer derived from MVK (poly‐MVK) had a tremendous specific optical rotation [α], which was as 32 times large as that of its monomer MVK. Poly‐MVK was confirmed to keep a prevailing helicity of backbone in solution by means of comparing the specific optical rotation and the CD spectra with that of MVK and the model compound such as ethyl menthyl ketone (EMK) and n‐hexyl menthyl ketone (n‐HMK). This conclusion was also confirmed by the fact that the specific optical rotation and the CD signal intensity of poly‐MBEK were not enough large due to backbone flexibility caused by the effective isolation of the main chain from the bulky menthyl. The excess value of one‐handed helicity of poly‐MVK decreased with the increase of polymerization temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1441–1448, 2010     

Steroidal Alkaloids from the Roots and Rhizomes of Vertrum nigrum L.

Two new steroidal alkaloids, neoverapatuline ( 1 ) and (1β,3α,5β)‐1,3‐dihydroxyjervanin‐12‐en‐11‐one ( 2 ), together with the four known compounds, veratramine ( 3 ), rubijervine ( 4 ), veratrosine ( 5 ), and veratroylzygadenine ( 6 ), were isolated from the roots and rhizomes of Veratrum nigrum L. Their structures were established through combined analyses of physicochemical properties and spectroscopic evidence. All compounds 1 – 6 were tested for their cytotoxicities in vitro against the human glioma cell line SF188.     

Gas chromatographic separation of the enantiomers of flumecinol and some related compounds

Flumecinol and related compounds can, without derivatization, be separated into their enantiomers by gas chromatography on cyclodextrin phases; permethylated β-cyclodextrin dissolved in OV-1701 can be particularly recommended. Thermodynamic data describing the different intensities of interaction of the individual enantiomers with the stationary phases were determined. The values measured imply different separation mechanisms for the compounds investigated.     

Diaryl-2-pyrrolidinemethanols catalyzed enantioselective epoxidation of α,β-enones: new insight into the effect of structural modification of the catalyst on reaction efficiency

Catalytic enantioselective epoxidation of α,β-unsaturated ketones promoted by diaryl-2-pyrrolidinemethanols and tert-butyl hydroperoxide (TBHP) is described. Investigation on structural modifications of the diaryl-2-pyrrolidinemethanols showed that fine tuning of the stereoelectronics of the substituents on the aryl moiety is important to achieve high efficiency. By employing a structurally optimized organocatalyst, significantly reduced loading (10 mol %) can be used to produce the epoxides in high yield and up to 90% ee at room temperature.     

Catalyst-Controlled Selectivity Switch in Three-Component Reaction: An NHC-Catalyzed Strategy for the Synthesis of δ-Lactone-Fused Spirobenzofuran-3-ones

An efficient, three-component reaction of aldehydes and benzofuran-3-ones was developed. This process provides a new approach for the preparation of synthetically and biologically important spirobenzofuran-3-one derivatives with moderate-to-good yields under mild conditions. A switch of intramolecular to intermolecular domino Michael–aldol–lactonization leading to differential product formation was achieved by different NHCs catalysis.     

Synthesis of new optically active α,α′,β‐trisubstituted‐β‐lactones as monomers for stereoregular biopolyesters

Various optically active (4R)‐alkyloxycarbonyl‐3,3‐dialkyl‐2‐oxetanones as monomers were synthesized from L‐(S)‐malic acid in six steps to prepare a new family of stereopolyesters for biomedical applications. The synthesis began with an esterification followed of a dialkylation in the aim to introduce hydrophobic groups as methyl or reactive group as allyl. Then, a saponification has permitted to obtain the corresponding diacids that reacted with appropriate alcohols to furnish different monoesters. The last and most important step was activation of hydroxyl group of monoesters with the asymmetric carbon configuration inversion according to the Mitsunobu reaction. Thus, this reaction has provided lactones from monoesters with 100% enantiomeric excess which was confirmed by ¹H NMR and by the synthesis of corresponding isotactic and semicrystalline homopolyesters. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2586–2597     

Synthesis of α,β-unsaturated ketone from α-iodo ketone using photoirradiation

Irradiation of α-iodo ketone in hexane under a nitrogen atmosphere with a high-pressure mercury lamp (λ>300nm) at room temperature afforded the corresponding α,β-unsaturated ketones in good yield. This reaction affords a new, clean and convenient synthetic method for the α,β-unsaturated ketone.     

Nucleophilic Fluoroalkylation of α,β‐Unsaturated Carbonyl Compounds with α‐Fluorinated Sulfones: Investigation of the Reversibility of 1,2‐Additions and the Formation of 1,4‐Adducts

A detailed investigation of the reactions of PhSO₂CF₂H and PhSO₂CH₂F with (E)‐chalcone (=(E)‐1,3‐diphenylprop‐2‐en‐1‐one) at low temperatures revealed that these two reactions were kinetically controlled, and the ratios of 1,2‐ vs. 1,4‐adducts, which did not change much over time at these temperatures, reflect the relative rates of the two reaction pathways. The controlled experiments of converting the PhSO₂CF₂‐ and PhSO₂CHF‐substituted 1,2‐adducts to 1,4‐adducts showed that these isomerizations are not favored due to the low stability and hard‐soft nature of PhSO₂CF and PhSO₂CHF^? anions. Moreover, taking advantage of the remarkable stability and softness of (PhSO₂)₂CF^? anion, an efficient thermodynamically controlled isomerization of (PhSO₂)₂CF‐substituted 1,2‐adduct to 1,4‐adduct was achieved for the first time.