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931.
932.
Stereochemically defined enantioenriched molecules were, are and will always be playing a pivotal role in the development of novel pharmaceutical agents. On this line, compounds having tertiary benzylic stereocenter are of special note. This has led to an increase in the development of novel synthetic strategies for accessing molecules having this structural moiety. The current critical discussion proposes to describe the various synthetic methodologies for the enantioselective synthesis of diaryl methanols, diarylmethyl amines and other related scaffolds with tertiary benzylic stereogenic center that came up during 1995–2016. Through this critical view, we would not only like to give the readers a brief outlook on the different techniques that can be followed for the synthesis of a vast array of entities having this structural core, but also would like to highlight the limitations the protocols that need to be addressed. 相似文献
933.
R. Senthil Kumar Asit Kumar Khanra Roy Johnson 《Journal of Sol-Gel Science and Technology》2018,86(2):374-382
For the first time, sintered alumina with high transparency in mid infrared region, composed of submicron grains, has been fabricated using sol–gel processing. Commercially available boehmite powder was used to prepare the stable sol. The sol was mixed with appropriate amount of sintering aids and alumina seeds. The sol was further gelled, dried, and heat treated at 1000?°C for producing alumina powder. The powder was further shaped into pellets by compaction and sintered at temperatures between 1200 and 1400?°C in air. Sintered samples were further pressed hot isostatically to produce sintered submicron transparent alumina. The synthesized powder was characterized for its morphology and phase. The sintered and hot isostatically pressed samples were characterized for their physical, mechanical, and optical properties. The present method produced transparent alumina with transparency upto 87% in mid-wave infrared region. These transparency values were at par with the transparency of single crystal sapphire in the mid-wave infrared region and the hardness values were even superior than sapphire. 相似文献
934.
Sourav Ghosh Punarbasu Roy Naiwrit Karmodak Prof. Dr. Eluvathingal D. Jemmis Prof. Dr. Govindasamy Mugesh 《Angewandte Chemie (International ed. in English)》2018,57(17):4510-4515
Nanomaterials with enzyme‐like activity (nanozymes) attract significant interest owing to their applications in biomedical research. Particularly, redox nanozymes that exhibit glutathione peroxidase (GPx)‐like activity play important roles in cellular signaling by controlling the hydrogen peroxide (H2O2) level. Herein we report, for the first time, that the redox properties and GPx‐like activity of V2O5 nanozyme depends not only on the size and morphology, but also on the crystal facets exposed on the surface within the same crystal system of the nanomaterials. These results suggest that the surface of the nanomaterials can be engineered to fine‐tune their redox properties to act as “nanoisozymes” for specific biological applications. 相似文献
935.
Kihong Lee Bonnie Choi Dr. Ilan Jen‐La Plante Maria V. Paley Xinjue Zhong Prof. Andrew C. Crowther Prof. Jonathan S. Owen Prof. Xiaoyang Zhu Prof. Xavier Roy 《Angewandte Chemie (International ed. in English)》2018,57(21):6125-6129
Two‐dimensional (2D) materials are commonly prepared by exfoliating bulk layered van der Waals crystals. The creation of synthetic 2D materials from bottom‐up methods is an important challenge as their structural flexibility will enable chemists to tune the materials properties. A 2D material was assembled using C60 as a polymerizable monomer. The C60 building blocks are first assembled into a layered solid using a molecular cluster as structure director. The resulting hierarchical crystal is used as a template to polymerize its C60 monolayers, which can be exfoliated down to 2D crystalline nanosheets. Derived from the parent template, the 2D structure is composed of a layer of inorganic cluster, sandwiched between two monolayers of polymerized C60. The nanosheets can be transferred onto solid substrates and depolymerized by heating. Electronic absorption spectroscopy reveals an optical gap of 0.25 eV, narrower than that of the bulk parent crystalline solid. 相似文献
936.
Günther Pardatscher Matthaeus Schwarz‐Schilling Dr. Shirley S. Daube Prof. Dr. Roy H. Bar‐Ziv Prof. Dr. Friedrich C. Simmel 《Angewandte Chemie (International ed. in English)》2018,57(17):4783-4786
Lithographic patterning of DNA molecules enables spatial organization of cell‐free genetic circuits under well‐controlled experimental conditions. Here, we present a biocompatible, DNA‐based resist termed “Bephore”, which is based on commercially available components and can be patterned by both photo‐ and electron‐beam lithography. The patterning mechanism is based on cleavage of a chemically modified DNA hairpin by ultraviolet light or electrons, and a subsequent strand‐displacement reaction. All steps are performed in aqueous solution and do not require chemical development of the resist, which makes the lithographic process robust and biocompatible. Bephore is well suited for multistep lithographic processes, enabling the immobilization of different types of DNA molecules with micrometer precision. As an application, we demonstrate compartmentalized, on‐chip gene expression from three sequentially immobilized DNA templates, leading to three spatially resolved protein‐expression gradients. 相似文献
937.
Hypochlorite‐Mediated Modulation of Photoinduced Electron Transfer in a Phenothiazine–Boron dipyrromethene Electron Donor–Acceptor Dyad: A Highly Water Soluble “Turn‐On” Fluorescent Probe for Hypochlorite
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Disha Soni Naresh Duvva Deepak Badgurjar Dr. Tapta Kanchan Roy Dr. Surendra Nimesh Geeta Arya Dr. Lingamallu Giribabu Dr. Raghu Chitta 《化学:亚洲杂志》2018,13(12):1594-1608
A highly water‐soluble phenothiazine (PTZ)–boron dipyrromethene (BODIPY)‐based electron donor–acceptor dyad ( WS‐Probe ), which contains BODIPY as the signaling antennae and PTZ as the OCl? reactive group, was designed and used as a fluorescent chemosensor for the detection of OCl?. Upon addition of incremental amounts of NaOCl, the quenched fluorescence of WS‐Probe was enhanced drastically, which indicated the inhibition of reductive photoinduced electron transfer (PET) from PTZ to 1BODIPY*; the detection limit was calculated to be 26.7 nm . Selectivity studies with various reactive oxygen species, cations, and anions revealed that WS‐Probe was able to detect OCl? selectively. Steady‐state fluorescence studies performed at varied pH suggested that WS‐Probe can detect NaOCl and exhibits maximum fluorescence in the pH range of 7 to 8, similar to physiological conditions. ESI‐MS analysis and 1H NMR spectroscopy titrations showed the formation of sulfoxide as the major oxidized product upon addition of hypochlorite. More interestingly, when WS‐Probe was treated with real water samples, the fluorescence response was clearly visible with tap water and disinfectant, which indicated the presence of OCl? in these samples. The in vitro cell viability assay performed with human embryonic kidney 293 (HEK 293) cells suggested that WS‐probe is non‐toxic up to 10 μm and implicates the use of the probe for biological applications. 相似文献
938.
Provi Palit Saswata Rabi Benu Kumar Dey Debashis Palit Monir Uddin Tapashi Ghosh Roy 《Journal of the Iranian Chemical Society》2018,15(9):1947-1959
Biologically important tetraaza-macrocyclic ligand 3,10-C-meso-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene dihydroperchlorate, Me8[14]diene·2HClO4 (L1·2HClO4) was synthesized by the condensation of 1,2-diaminopropane with acetone in presence of quantitative amount of HClO4 and three isomeric ligands designated as LA, LB and LC were separated by the reduction of L1·2HClO4 with NaBH4 and fractional crystallization from xylene. The nitrato, nitro, bromido, and iodido complexes of palladium with diene ligand L1 were prepared by the interaction of L1·2HClO4 with K2[Pd(NO3)4], K2[Pd(NO2)4], K2[PdBr4], and K2[PdI4] (prepared by the reactions with PdCl2 with KNO3, KNO2, KBr, and KI, respectively), respectively. The bromide and iodido complexes of LA were prepared by the axial substitution reactions with [PdLACl2]Cl2. By contrast, similar complexes of other isomeric ligands LB and LC were prepared by axial addition reactions of [PdL?][PdCl4] (L′?=?LB or LC) with KBr and KI, respectively. The complexes were characterized on the basis of elemental analysis: IR, 1H-NMR, UV–Vis spectroscopic analysis, and magnetic and molar conductivity data. The antifungal and antibacterial activities of these compounds have been studied against some phyto-pathogenic fungi and bacteria. 相似文献
939.
Supramolecular Gels Derived from the Salts of Variously Substituted Phenylacetic Acid and Dicyclohexylamine: Design,Synthesis, Structures,and Dye Adsorption
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A well‐studied supramolecular synthon, namely, secondary ammonium monocarboxylate (SAM), was exploited to generate a new series of organic salts derived from variously substituted phenylacetic acid and dicyclohexylamine as potential low‐molecular‐weight gelators. As much as 25 % of the SAM salts under study were gelators. The gels were characterized by rheology, and the morphology of the gel networks was studied by high‐resolution electron microscopy. Single‐crystal and powder XRD data were employed to study structure–property (gelation) correlations. One of the gels could adsorb a hydrophobic dye (Nile Red) more efficiently than that of a hydrophilic dye (Calcein) from dimethyl sulfoxide; this might provide useful clues towards the development of stain‐removing gels. 相似文献
940.
Patricia Kaori Soares Gustavo Galo Marcheafave Adriano de Araújo Gomes Ieda Spacino Scarminio Roy Edward Bruns 《Chromatographia》2018,81(8):1189-1200
HPLC-DAD analysis of statistical mixture design extracts of Erythrina speciosa Andrews leaves provided chromatographic and UV–visible profiles of their basic and organic fractions that were treated with the PARAFAC multivariate method. The design extracts provided greater varieties and amounts of metabolites than could be obtained by classical extraction methods. Fractionation provided more diverse fingerprint information than obtained previously from only the crude extract. The two largest chromatographic peaks, one with a 4.8 min elution time having an intense spectral band at 235 nm and the other a 5.8 min peak with an intense 238 nm band for the basic fraction were obtained with the ternary 1:1:1 ethanol–dichloromethane–hexane mixture. These can be assigned to diene-type and lactonic alkaloids. Peaks with the same retention times are also found in the organic fraction but are extracted with different mixtures and have distinct spectral behavior in the 235 nm region, probably being aromatic alkaloids. The above strategy permits a more unambiguous assignment of metabolic groups to specific chromatographic peaks. This can be expected to provide higher quality chromatographic fingerprints for natural products’ chemistry. 相似文献