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31.
A synthetic approach towards the novel anti-inflammatory diterpenoid rameswaralide from the cis-Corey lactone involving a tandem RCM and Diels-Alder reaction has been conceived and endeavors so far have led to the acquisition of the BCD ring fragment of the natural product. 相似文献
32.
In the present work, the influence of porosity and boron on shear thickening behavior of hybrid mesoporous silica has been studied. Three different levels of boron modification were performed by varying the molar composition of boric acid viz., 1.5 mmol, 2.5 mmol, and 3.5 mmol in a co-condensation approach. The incorporation of boron in mesoporous silica network was confirmed by various techniques such as Fourier transform infra-red (FTIR), and 11B solid- state nuclear magnetic resonance (NMR) spectroscopy. The morphology and particle size were confirmed by using scanning and transmission electron microscopy. To evaluate the effect of boron and porosity on the shear thickening behavior, dispersions were prepared from mesoporous boron- modified silica (MSiB), control mesoporous silica (MSi), non-porous boron-modified silica (SiB), and control non-porous silica (Si) in polyethylene glycol. The shear thickening behavior was studied using steady shear rheology. The dispersion prepared from different loadings of synthesized MSiB containing 1.5 mmol boron showed more than 16 times increase in viscosity (657.7 Pa.s) compared to that of MSi (39.2 Pa.s) at a fairly low volume fraction (φ = 0.15) of silica. It is expected that the highly ordered mesoporous architecture of hybrid silica has improved the interaction between the particle and the dispersing medium through hydrogen bonding. The porous morphology of the hybrid mesoporous silica as well as the incorporation of boron in the silica network favors the formation of a frictional contact network, and a transition from continuous shear thickening (CST) to discontinuous shear thickening (DST) behavior was observed. Therefore, silica prepared via incorporation of boron as well as porosity can be material of interest in variety of applications, for example, soft body armors, sporting goods, and shear thickening electrolytes for high impact resistant batteries. 相似文献
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A new synthetic strategy has been devised to access a variety of polyhydroxylated piperidines belonging to the azasugar class of glycosidase inhibitors. The key precursor (3aR, 7aR)-5-benzyl-2,2-dimethyl-7-methylenehexahydro[1,3]dioxo[4,5-c]pyridine is obtained by photoinduced electron transfer (PET) cyclization of the corresponding alpha-trimethylsilylmethylamine radical cation to the tethered acetylene functionality. The new molecules have been evaluated for inhibitory properties for certain beta-glycosidases and have been found to be moderate to weak inhibitors of the enzymes under study. 相似文献
37.
Nafisa Gull Shahzad Maqsood Khan Muhammad Taqi Zahid Butt Saba Zia Syed Khalid Atif Islam Imran Sajid Rafi Ullah Khan Martin William King 《先进技术聚合物》2019,30(9):2414-2424
Hydrogel‐based drug delivery systems can leverage therapeutically favorable upshots of drug release and found clinical uses. Hydrogels offer temporal and spatial control over the release of different therapeutic agents. Because of their tailor made controllable degradability, physical properties, and ability to prevent the labile drugs from degradation, hydrogels provide platform on which diverse physicochemical interactions with entrapped drugs cause to control drug release. Herein, we report the fabrication of novel vinyltrimethoxy silane (VTMS) cross‐linked chitosan/polyvinyl pyrrolidone hydrogels. Swelling in distilled water in conjunction with different buffer and electrolyte solutions was performed to assess the swellability of hydrogels. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X‐ray diffraction (XRD) analysis were further conducted to investigate the possible interactions between components, thermal stability, and crystallinity of as‐prepared hybrid hydrogels, respectively. In vitro time‐dependent biodegradability, antimicrobial study, and cytotoxicity were also carried out to evaluate their extensive biocompatibility and cytotoxic behavior. More interestingly, in vitro drug release study allowed for the controlled release of cephradine. Therefore, this facile strategy developed the novel biocompatible and biodegradable hybrid hydrogels, which could significantly expand the scope of these hydrogels in other biomedical applications like scaffolds, skin regeneration, tissue engineering, etc. 相似文献
38.
Collective syntheses of five spiro[4.5]decane framework bearing sesquiterpenoids, namely, α & β-vetispirenes, β-vetivone, agarospirol and hinesol as well as formal synthesis of axenol and gleenol from a readily available precursor cyclohexanone-β-ketoester via the intermediacy of a versatile intermediate (2,10-dimethylspiro[4.5]dec-1-en-6-one) have been accomplished in a concise manner. 相似文献
39.
Goverdhan Mehta Gagliardini Vanessa Kabirul Islam Kailasam Venkatesan 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(1):o90-o93
The cis,syn,cis‐tricyclic [2+2]‐dimer of cyclooctatetraene, C16H16, crystallizes in space group Pca21 with two molecules in the asymmetric unit. An extensive network of weak C—H⋯π(Czdbnd;C) interactions between the two independent molecules, A and B, as well as A⋯A and B⋯B interactions, are observed in the supramolecular assembly. The C—H groups point more towards one C atom than to the centre of the Czdbnd;C bond. Notable among the interactions are bifurcated (cyclobutane)C—H⋯Czdbnd;C contacts that span transannularly the eight‐membered ring. 相似文献
40.
Rahim MA Islam MS Bae TS Choi WS Noh YY Lee HJ 《Langmuir : the ACS journal of surfaces and colloids》2012,28(22):8486-8495
The mixing of Ag ion-doped poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAA) produced Ag ion-doped polyelectrolyte complex particles (PECs) in solution. Positively charged Ag ion-doped PECs (Ag ion PECs) with a spherical shape were deposited alternatively with PAA to form a multilayer assembly. The multilayered film containing Ag ion PECs was reduced to generate a composite nanostructure. Metal nanoparticle (NP)-enriched nanocomposite films were formed by an additional process of the postadsorption of precursors on PECs within the nanocomposite films, which resulted in the enhancement of the catalytic and electrical properties of the composite films. Because the films contain PECs that are responsive to changes in pH and most of the NPs are embedded in the PECs, interesting catalytic properties, which are unexpected in a particle-type catalyst, were observed upon pH changes. As a result of the reversible structural changes of the films and the immobilization of the NPs within the films, the film-type catalysts showed enhanced performance and stability during catalytic reactions under various pH conditions, compared to particle-type catalysts. 相似文献