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  • 1
    Language: English
    In: The Journal of organic chemistry, 01 September 2017, Vol.82(17), pp.9182-9190
    Description: A novel, organobase-catalyzed and highly chemoselective Michael-Michael-acetalization cascade is presented for the efficient synthesis of spiro-indandione skeletons. Following this very simple protocol, a broad range of products was obtained in good yields with excellent diastereocontrol. The role of steric factors in the acetalization step was evaluated.
    ISSN: 00223263
    E-ISSN: 1520-6904
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  • 2
    Language: English
    In: Chemistry – A European Journal, 10 June 2013, Vol.19(24), pp.7713-7717
    Description: : The direct vinylogous Michael addition of γ‐substituted butenolides with a series of 3‐aroyl acrylates and 1,2‐diaroylethylenes has been demonstrated. This organocatalytic method delivers highly enantio‐ and diastereomerically pure γ,γ‐disubstituted butenolides with adjacent quaternary and tertiary stereocenters (see scheme).
    Keywords: Cinchona Alkaloids ; Butenolides ; Michael Addition ; Organocatalysis ; Quaternary Stereogenic Center
    ISSN: 0947-6539
    E-ISSN: 1521-3765
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  • 3
    In: Chemical Communications, 2013, Vol.49(87), pp.10266-10268
    Description: Preparation of new types of trisubstituted oxazoles is realized via chemoselective O -acylations and intramolecular Wittig reactions with ester functionalities using in situ formed phosphorus ylides as key intermediates. A plausible reaction mechanism for this undiscovered chemistry is also proposed based on the existence of expected and rearranged isomeric oxazoles.
    Keywords: Oxazoles -- Chemical Synthesis;
    ISSN: 1359-7345
    E-ISSN: 1364-548X
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  • 4
    Language: English
    In: PLoS ONE, 2012, Vol.7(5), p.e37764
    Description: Withanolides are a large group of steroidal lactones found in Solanaceae plants that exhibit potential anticancer activities. We have previously demonstrated that a withanolide, tubocapsenolide A, induced cycle arrest and apoptosis in human breast cancer cells, which was associated with the inhibition of heat shock protein 90 (Hsp90). To investigate whether other withanolides are also capable of inhibiting Hsp90 and to analyze the structure-activity relationships, nine withanolides with different structural properties were tested in human breast cancer cells MDA-MB-231 and MCF-7 in the present study. Our data show that the 2,3-unsaturated double bond-containing withanolides inhibited Hsp90 function, as evidenced by selective depletion of Hsp90 client proteins and induction of Hsp70. The inhibitory effect of the withanolides on Hsp90 chaperone activity was further confirmed using in vivo heat shock luciferase activity recovery assays. Importantly, Hsp90 inhibition by the withanolides was correlated with their ability to induce cancer cell death. In addition, the withanolides reduced constitutive NF-κB activation by depleting IκB kinase complex (IKK) through inhibition of Hsp90. In estrogen receptor (ER)-positive MCF-7 cells, the withanolides also reduced the expression of ER, and this may be partly due to Hsp90 inhibition. Taken together, our results suggest that Hsp90 inhibition is a general feature of cytotoxic withanolides and plays an important role in their anticancer activity.
    Keywords: Research Article ; Biology ; Medicine ; Molecular Biology ; Cell Biology ; Oncology ; Biochemistry
    E-ISSN: 1932-6203
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  • 5
    Language: English
    In: Tetrahedron, 26 August 2014, Vol.70(34), pp.5038-5045
    Description: A Bu P-mediated mild and efficient synthesis of multi-functional alkenes has been described starting from substituted acrylate with aldehydes. In situ generated zwitterionic intermediates underwent proton-exchange to afford ylide intermediates, which were trapped by corresponding aldehydes providing the products in up to 92% yield with complete -stereoselectivity. Further derivatization of the products was performed to furnish functional pyridazinones. An efficient synthesis of multi-functional alkenes has been described starting from commercially available starting materials. Phosphorus ylide is the key intermediate in this approach. A plausible mechanism has been proposed and the products were further converted to pyridazinone derivatives.
    Keywords: Multi-Functional Alkene ; Phosphorus Ylide ; Wittig Reaction ; Pyridazinone ; Cyclopropane ; Chemistry
    ISSN: 0040-4020
    E-ISSN: 1464-5416
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  • 6
    Language: English
    In: The Journal of organic chemistry, 21 October 2016, Vol.81(20), pp.10071-10080
    Description: An enantioselective synthesis of benzopyrano[3,4-c]pyrrolidine derivatives via organocatalyzed [3 + 2] cycloaddition has been achieved. Cinchona alkaloid-derived organocatalysts as Brønsted bases have been examined for this asymmetric cycloaddition of o-hydroxy aromatic aldimines with 3-substituted coumarins. An unexpected rearrangement of the quaternary acyl moiety in the products resulted in an in situ protection of the o-hydroxy group.
    Keywords: Cyclization (Chemistry) – Usage ; Chemical Synthesis – Usage ; Benzene – Chemical Properties ; Catalysis – Usage;
    ISSN: 00223263
    E-ISSN: 1520-6904
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  • 7
    Language: English
    In: European Journal of Organic Chemistry, July 2013, Vol.2013(21), pp.4634-4641
    Description: A convenient protocol for the preparation of tricyclic fused furans in one step starting from acid chlorides and Michael acceptors is described. The reaction conditions are mild, operationally simple, and have a broad substrate scope. The reaction is believed to proceed by an intramolecular Wittig reaction with a phosphorus ylide as the key intermediate. Functionalized fused furan derivatives were prepared in an intramolecular Wittig reaction in one step starting from simple and readily available substrates. The reaction is belived to proceed via an ylide intermediate. Furthermore, the products could be easily transformed into synthetically useful naphthofurans.
    Keywords: Fused‐Ring Systems ; Oxygen Heterocycles ; Michael Addition ; Ylides ; Wittig Reactions
    ISSN: 1434-193X
    E-ISSN: 1099-0690
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  • 8
    Language: English
    In: Journal of Alloys and Compounds, 25 June 2016, Vol.671, pp.100-108
    Description: This study investigated the effect of massive spalling of intermetallic compounds (IMCs) on the microstructural evolution and mechanical properties of solder joints after multiple reflows. SAC305 solder was reflowed on substrates with four Co-based surface finishes: electroless Co (EC), electroless Co/immersion Au (ECIG), electroless Co/electroless Pd (ECEP), and electroless Co/electroless Pd/immersion Au (ECEPIG). CoSn was the main intermetallic compound (IMC) that formed in the systems, and it massively spalled in the systems with Pd and high P content. Systems with massive spalling have a high shear strength and low shear height owing to solid solution strengthening. Due to strain hardening, high shear velocity caused high strength in all systems. Massive spalling of CoSn transformed the failure mode from brittle to ductile and enhanced the shear strength of the joints.
    Keywords: Massive Spalling ; Multiple Reflows ; Intermetallic Compound ; Shear Test ; Sac305 ; Co–Sn–P ; Engineering ; Chemistry ; Physics
    ISSN: 0925-8388
    E-ISSN: 1873-4669
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  • 9
    In: Organic & Biomolecular Chemistry, 2014, Vol.12(24), pp.4044-4050
    Description: The development of efficient methods for the synthesis of heteroaromatic compounds is always of great importance for chemists. In this Perspective, we describe a general approach for the synthesis of functionalized heteroaromatics via intramolecular Wittig reactions. In all cases, the reaction proceeds via in situ generated phosphorus ylides. We especially emphasize the importance of chemoselective intramolecular Wittig reactions using designed Michael acceptors and suitable acyl chloride as trapping reagents, which allows formation of two different classes of heteroaromatics from the same substrates. This metal-free approach is quite general and works in a number of examples, furnishing the corresponding products in moderate to good yields under relatively mild reaction conditions.
    ISSN: 1477-0520
    E-ISSN: 1477-0539
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  • 10
    In: Organic & Biomolecular Chemistry, 2013, Vol.11(1), pp.44-47
    Description: An organocatalytic asymmetric synthesis of spironitrocyclopropanes has been demonstrated starting from 2-arylidene-1,3-indandiones and bromonitroalkanes catalyzed by a cinchona-derived bifunctional organocatalyst. The products were obtained with excellent enantioselectivities, diastereoselectivities and with good yields.
    Keywords: Cinchona Alkaloids -- Chemistry ; Cyclopropanes -- Chemical Synthesis ; Spiro Compounds -- Chemical Synthesis;
    ISSN: 1477-0520
    E-ISSN: 1477-0539
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