- Probing for the pharmacophore of the cytotoxic neoclerodane salvileucalin B
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The novel [4.3.1]propelladiene 2, which embodies the key structural elements of the pentacyclic core of the cytotoxic neoclerodane salvileucalin B (1), has been prepared using a rhodium-catalysed intramolecular Bchner reaction as the key step. Compound 2 and the readily obtained derivatives 12-17 all proved to be essentially inactive when tested against a panel of four human cancer cell lines. Furthermore, not one of these compounds was a P-gp inhibitor.
- Heinrich, Nora,Banwell, Martin G.,Willis, Anthony C.,Cade, Ian A.,Capon, Robert J.,Huang, Xiao-Cong
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Read Online
- Efficient C-H Amination Catalysis Using Nickel-Dipyrrin Complexes
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A dipyrrin-supported nickel catalyst (AdFL)Ni(py) (AdFL: 1,9-di(1-adamantyl)-5-perfluorophenyldipyrrin; py: pyridine) displays productive intramolecular C-H bond amination to afford N-heterocyclic products using aliphatic azide substrates. The catalytic amination conditions are mild, requiring 0.1-2 mol% catalyst loading and operational at room temperature. The scope of C-H bond substrates was explored and benzylic, tertiary, secondary, and primary C-H bonds are successfully aminated. The amination chemoselectivity was examined using substrates featuring multiple activatable C-H bonds. Uniformly, the catalyst showcases high chemoselectivity favoring C-H bonds with lower bond dissociation energy as well as a wide range of functional group tolerance (e.g., ethers, halides, thioetheres, esters, etc.). Sequential cyclization of substrates with ester groups could be achieved, providing facile preparation of an indolizidine framework commonly found in a variety of alkaloids. The amination cyclization reaction mechanism was examined employing nuclear magnetic resonance (NMR) spectroscopy to determine the reaction kinetic profile. A large, primary intermolecular kinetic isotope effect (KIE = 31.9 ± 1.0) suggests H-atom abstraction (HAA) is the rate-determining step, indicative of H-atom tunneling being operative. The reaction rate has first order dependence in the catalyst and zeroth order in substrate, consistent with the resting state of the catalyst as the corresponding nickel iminyl radical. The presence of the nickel iminyl was determined by multinuclear NMR spectroscopy observed during catalysis. The activation parameters (ΔH? = 13.4 ± 0.5 kcal/mol; ΔS?= -24.3 ± 1.7 cal/mol·K) were measured using Eyring analysis, implying a highly ordered transition state during the HAA step. The proposed mechanism of rapid iminyl formation, rate-determining HAA, and subsequent radical recombination was corroborated by intramolecular isotope labeling experiments and theoretical calculations.
- Betley, Theodore A.,Clarke, Ryan M.,Dong, Yuyang,Porter, Gerard J.
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supporting information
p. 10996 - 11005
(2020/07/08)
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- Cooperative iodine and photoredox catalysis for direct oxidative lactonization of carboxylic acids
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A new method for the formation of γ- and δ-lactones from carboxylic acids through direct conversion of benzylic C-H to C-O bonds is described. The reaction is conveniently induced by visible light and relies on a mild cooperative catalysis by the combination of molecular iodine and an organic dye.
- Duhamel, Thomas,Mu?iz, Kilian
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supporting information
p. 933 - 936
(2019/01/23)
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- Reductive C-C Coupling by Desulfurizing Gold-Catalyzed Photoreactions
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[Au2(μ-dppm)2]Cl2-mediated photocatalysis reactions are usually initiated by ultraviolet A (UVA) light; herein, an unreported system using blue light-emitting diodes (LEDs) as excitation light source was found. The red shift of the absorption wavelength originates from the combination of [Au2(μ-dppm)2]Cl2 and ligand (Ph3P or mercaptan). On the basis of this finding, a gold-catalyzed reductive desulfurizing C-C coupling of electrophilic radicals and styrenes mediated by blue LEDs is presented, a coupling which cannot be efficiently accessed by previously reported methods. This mild and highly efficient C-C bond formation strategy uses mercaptans both as electron-deficient alkyl radical precursor as well as the hydrogen source. Two examples of amino acids have also been modified by using this strategy. Moreover, this methodology could be applied in polymer synthesis. Gram-scale synthesis and mechanistic insights into this transformation are also presented.
- Zhang, Lumin,Si, Xiaojia,Yang, Yangyang,Witzel, Sina,Sekine, Kohei,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
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p. 6118 - 6123
(2019/07/03)
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- Multiple Halogenation of Aliphatic C?H Bonds within the Hofmann–L?ffler Manifold
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An innovative approach to position-selective polyhalogenation of aliphatic hydrocarbon bonds is presented. The reaction proceeded within the Hofmann-L?ffler manifold with amidyl radicals as the sole mediators to induce selective 1,5- and 1,6-hydrogen-atom transfer followed by halogenation. Multiple halogenation events of up to four innate C?H bond functionalizations were accomplished. The broad applicability of this new entry into polyhalogenation and the resulting synthetic possibilities were demonstrated for a total of 27 different examples including mixed halogenations.
- Del Castillo, Estefanía,Martínez, Mario D.,Bosnidou, Alexandra E.,Duhamel, Thomas,O'Broin, Calvin Q.,Zhang, Hongwei,Escudero-Adán, Eduardo C.,Martínez-Belmonte, Marta,Mu?iz, Kilian
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supporting information
p. 17225 - 17229
(2018/11/10)
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- NOVEL TRICYCLIC CALCIUM SENSING RECEPTOR ANTAGONISTS
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Novel tricyclic compounds of Formula (I) and pharmaceutically acceptable salts thereof are disclosed as useful for treating or preventing osteoporosis and similar conditions. The compounds are effective as calcium sensing receptor antagonists. Pharmaceutical compositions and methods of treatment are also included.
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Page/Page column 106
(2015/07/07)
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- NOVEL TRICYCLIC CALCIUM SENSING RECEPTOR ANTAGONISTS FOR THE TREATMENT OF OSTEOPOROSIS
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Novel tricyclic compounds of the formula (I): and pharmaceutically acceptable salts thereof are disclosed as useful for treating or preventing osteoporosis and similar conditions. The compounds are effective as calcium sensing receptor antagonists. Pharmaceutical compositions and methods of treatment are also included.
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Page/Page column 105
(2015/07/07)
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- PPh3-mediated intramolecular conjugation of alkyl halides with electron-deficient olefins: Facile synthesis of chromans and relevant analogues
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With the mediation of phosphine, the direct intramolecular coupling of two electrophiles-alkyl halides with electron-deficient olefins-has been successfully realized in an intramolecular conjugate addition manner. The reaction provides a new approach for
- Zhu, Jian-Bo,Wang, Peng,Liao, Saihu,Tang, Yong
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p. 4570 - 4572
(2013/06/04)
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- Calcilytic compounds
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Novel phosphate esters compounds and methods of using them as calcilytic compounds are provided.
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Page/Page column 7
(2008/06/13)
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- Calcilytic compounds
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Novel calcilytic compounds and methods of using them are provided.
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Page/Page column 6
(2010/02/05)
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- Calcilytic compounds
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Novel calcilytic compounds and methods of using them are provided.
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- Diaminoindanes as microsomal triglyceride transfer protein inhibitors
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The synthesis and biological activities of biarylamide-substituted diaminoindanes as microsomal triglyceride transfer protein (MTP) inhibitors are described. One of the more potent compounds, 8aR, inhibited both the secretion of apoB from Hep G2 cells and the MTP-mediated transfer of triglycerides between synthetic acceptor and donor liposomes with IC50 values of 0.7 and 70 nM, respectively. In normolipidemic rats and dogs, oral administration of 8aR dose-dependently reduced both plasma triglycerides and total cholesterol. Moreover, in rats and dogs, 8aR also prevented the postprandial rise in plasma triglycerides following a bolus administration of a fat load. Because MTP inhibitors decrease very low density lipoprotein assembly in the liver, the potential for hepatic lipid accumulation was evaluated. In normolipidemic rats, hepatic cholesterol and triglyceride contents were dose-dependently increased by 8aR. However, hepatic lipid accumulation resulted in negligible change in total liver weight and was reversible after withdrawal of the compound.
- Ksander,DeJesus,Yuan,Fink,Moskal,Carlson,Kukkola,Bilci,Wallace,Neubert,Feldman,Mogelesky,Poirier,Jeune,Steele,Wasvery,Stephan,Cahill,Webb,Navarrete,Lee,Gibson,Alexander,Sharif,Hospattankar
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p. 4677 - 4687
(2007/10/03)
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- Acyl Radicals: Intermolecular and Intramolecular Alkene Addition Reactions
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A full study of the use of phenyl selenoesters as precursors to acyl radicals and their subsequent participation in intermolecular and intramolecular alkene addition reactions is detailed.Primary alkyl-, vinyl-, and arylsubstituted acyl radicals generated by Bu3SnH treatment of the corresponding phenyl selenoesters participate cleanly in intermolecular addition reactions with alkenes bearing electron-withdrawing or radical-stabilizing substituents at rates that exceed those of the potentially competitive decarbonylation or reduction.Similarly, their intramolecular addition to activated or unactivated alkenes proceeds without significant competitive reduction or decarbonylation and at rates generally >/= 1 x 106 s-1 with some occuring at rates >/= 3 x 107 s-1.Consistent with their behavior in intermolecular addition reactions, the 5-exo-trig cyclizations of secondary and tertiary alkyl-substituted acyl radicals to an unactivated olefin acceptor may be accompanied by varying degrees of decarbonylation, even under low-temperature free-radical conditions.Studies are presented which suggest that the intramolecular additions of acyl radicals to alkenes under the conditions detailed herein may be regarded as irreversible, kinetically controlled processes which exhibit regioselectivity that is predictable based on well-established empirical rules set forth for the analogous free-radical cyclization reactions of alkyl radicals.
- Boger, Dale L.,Mathvink, Robert J.
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p. 1429 - 1443
(2007/10/02)
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- Acyl Radicals: Functionalized Free Radicals for Intramolecular Cyclization Reactions
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A study describing the use of phenyl selenoesters as direct precursors to acyl radicals suitable for the initiation of intramolecular free-radical cyclization reactions is detailed.
- Boger, Dale L.,Mathvink, Robert J.
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p. 3377 - 3379
(2007/10/02)
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