1H and 13C NMR spectral assignments of novel chromenylchalcones

Several types of chalcones containing 2H‐chromen group were synthesized. Claisen–Schmidt condensation of 2H‐chromen‐3‐carbaldehydes (I) with methoxy substituted acetophenones afforded (E)‐3‐(2H‐chromen‐3‐yl)‐1‐(methoxyphenyl)prop‐2‐en‐1‐ones (chromenylchalcones, 1–7). Other types of chromenylchalcone, (E)‐1‐(6‐methoxy‐2H‐chromen‐3‐yl)‐3‐(methoxyphenyl)prop‐2‐en‐1‐ones (8–13) were also obtained between reaction of methoxy substituted benzaldehydes and 1‐(6‐methoxy‐2H‐chromen‐3‐yl)ethanone (II). Dichromenylchalcones (14–16) were also synthesized through the same reaction between aldehydes (I) and ketone (II). Their complete ¹H‐NMR and ¹³C‐NMR assignments are reported here and more polysubstituted chromenylchalcones synthesized or isolated from the natural sources in the future can be identified on the basis of the NMR data reported here. Copyright © 2012 John Wiley & Sons, Ltd.     

Organic hybrid of chlorinated polyethylene and hindered phenol. II. Influence of the chemical structure of small molecules on viscoelastic properties

The viscoelastic properties and stabilities of those properties of organic hybrids consisting of chlorinated polyethylene (CPE) and tetrakis[methylene‐3‐(3‐5‐di‐tert‐butyl‐4‐hydroxy phenyl)propionyloxy]methane (AO‐60) and triethylene glycol bis[3‐(3‐tert‐butyl‐4‐hydroxy‐5‐methyl phenyl)propionyloxy] (AO‐70) were investigated. The CPE/AO‐70 hybrids show only one transition, whereas for the CPE/AO‐60 hybrids, one novel relaxation appears above the glass‐transition temperature of CPE. This relaxation on the higher temperature side in the mechanical spectrum for CPE/AO‐60 is associated with the appearance of the AO‐60‐rich phase. Furthermore, the stabilities of the viscoelastic properties and microstructures of the organic hybrids consisting of CPE and multifunctional hindered phenols are dominated by the strength of the intermolecular interaction between CPE and phenols and the conformations of the middle skeletal parts of hindered phenols. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1496–1503, 2000     

Indium trichloride mediated intramolecular Prins-type cyclization

[reaction: see text] Intramolecular Prins-type reactions of compounds having both functionalities of homoallyl alcohol and acetal moiety are described. The intramolecular Prins cyclizations were performed using indium trichloride in chloroform or 25% aqueous THF. Both 9-oxabicyclo[3.3.1]nonane and 3,9-dioxabicyclo[3.3.1]nonane compounds were successfully obtained in moderate yields.     

Biomedical significance of endothelial cell specific growth factor, angiopoietin

Until recently, vascular endothelial growth factor (VEGF) was the only growth factor proven to be specific and critical for blood vessel formation. Other long-known factors, such as the fibroblast growth factors (FGFs), platelet-derived growth factor, or transforming growth factor-beta, had profound effects in endothelial cells. But such factors were nonspecific, in that they could act on many other cells, and it seemed unlikely that these growth factors would be effective targets for treatment of endothelial cell diseases. A recently discovered endothelial cell specific growth factor, angiopoietin, has greatly contributed to our understanding of the development, physiology, and pathology of endothelial cells (Davis et al., 1996; Yancopoulos et al., 2000). The recent studies that identified and characterized the physiological and pathological roles of angiopoietin have allowed us to widen and deepen our knowledge about blood vessel formation and vascular endothelial function. Therefore, in this review, we describe the biomedical significance of these endothelial cell growth factors, the angiopoietins, in the vascular system under normal and pathological states.     

ZIF-Induced d-Band Modification in a Bimetallic Nanocatalyst: Achieving Over 44 % Efficiency in the Ambient Nitrogen Reduction Reaction

The electrochemical nitrogen reduction reaction (NRR) offers a sustainable solution towards ammonia production but suffers poor reaction performance owing to preferential catalyst–H formation and the consequential hydrogen evolution reaction (HER). Now, the Pt/Au electrocatalyst d-band structure is electronically modified using zeolitic imidazole framework (ZIF) to achieve a Faradaic efficiency (FE) of >44 % with high ammonia yield rate of >161 μg mg_cat⁻¹ h⁻¹ under ambient conditions. The strategy lowers electrocatalyst d-band position to weaken H adsorption and concurrently creates electron-deficient sites to kinetically drive NRR by promoting catalyst–N₂ interaction. The ZIF coating on the electrocatalyst doubles as a hydrophobic layer to suppress HER, further improving FE by >44-fold compared to without ZIF (ca. 1 %). The Pt/Au-N_ZIF interaction is key to enable strong N₂ adsorption over H atom.     

A synthetic route to highly substituted 1,2,3,4-tetrahydroisoquinolines via Yb(OTf)3 -catalyzed diastereoselective ring opening of bridged oxazolidines: asymmetric synthesis of 2-azapodophyllotoxin

We herein report a robust and efficient synthetic route to highly functionalized enantiopure 1,2,3,4-tetrahydroisoquinolines (THIQs) from Garner aldehyde. We utilized the inherent chirality of Garner aldehyde through 1,2- and 1,3-/1,4-asymmetric inductions iteratively to obtain 1,2,3,4-tetrasubstitued THIQs using rigid and isolable bridged oxazolidines without any external chiral sources. All possible stereoisomers of bridged oxazoliodines were efficiently synthesized from L- and D-Garner aldehydes and transformed into fully functionalized THIQs via diastereoselective ring opening with various nucleophiles in the presence of Yb(OTf)(3). This methodology furnished four out of eight possible diastereomers of 1,2,3,4-tetrasubstituted THIQs despite the electronic nature of substituents on the aryl rings. Finally, the enantioselective synthesis of 2-azapodophyllotoxin was achieved with an overall yield of 35.4% (eight steps) from D-Garner aldehyde using this synthetic route.     

Isolation and crystallographic characterization of solvate- and anion-stabilized PCP pincer complexes of palladium(II)

Pincer PCP-Pd(II) complex [PdCl(PCP)] (1) (PCP = ^?CH(CH₂CH₂PPh₂)₂) reacts with AgNO₃ to give [Pd(NO₃)(PCP)] (2). Similar reaction with AgBF₄ gives the aqua complex [Pd(OH₂)(PCP)][BF₄] (3) and the dinuclear complex [{Pd(PCP)}₂(μ-Cl)][BF₄] (4) with singly bridging chloro ligand. All new complexes were characterized by NMR spectroscopy, ESI-MS and single-crystal X-ray diffraction. Complex 1 and the triflate complex [Pd(OTf)(PCP)] (5) are active towards Suzuki–Miyaura coupling between aryl bromides and phenyl boronic acid.     

Preparation of interpenetrating polymer network composed of poly(ethylene glycol) and poly(acrylamide) hydrogels as a support of enzyme immobilization

Poly(ethylene glycol)(PEG)‐based interpenetrating polymeric network (IPN) hydrogels were prepared for the application of enzyme immobilization. Poly(acrylamide)(PAAm) was chosen as the other network of IPN hydrogel and different concentration of PAAm networks were incorporated inside the PEG hydrogel to improve the mechanical strength and provide functional groups that covalently bind the enzyme. Formation of IPN hydrogels was confirmed by observing the weight per cent gain of hydrogel after incorporation of PAAm network and by attenuated total reflectance/Fourier transform infrared (ATR/FTIR) analysis. Synthesis of IPN hydrogels with higher PAAm content produced more crosslinked hydrogels with lower water content (WC), smaller M_c and mesh size, which resulted in enhanced mechanical properties compared to the PEG hydrogel. The IPN hydrogels exhibited tensile strength between 0.2 and 1.2 MPa while retaining high levels of hydration (70–81% water). For enzyme immobilization, glucose oxidase (GOX) was immobilized to PEG and IPN hydrogel beads. Enzyme activity studies revealed that although all the hydrogels initially had similar enzymatic activity, enzyme‐immobilizing PEG hydrogels lost most of the enzymatic activity within 2 days due to enzyme leaching while IPN hydrogels maintained a maximum 80% of the initial enzymatic activity over a week due to the covalent linkage between the enzyme and amine groups of PAAm. Copyright © 2008 John Wiley & Sons, Ltd.