- Structure and Reactivity of a Manganese(VI) Nitrido Complex Bearing a Tetraamido Macrocyclic Ligand
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Manganese complexes in +6 oxidation state are rare. Although a number of Mn(VI) nitrido complexes have been generated in solution via one-electron oxidation of the corresponding Mn(V) nitrido species, they are too unstable to isolate. Herein we report the isolation and the X-ray structure of a Mn(VI) nitrido complex, [MnVI(N)(TAML)]- (2), which was obtained by one-electron oxidation of [MnV(N)(TAML)]2- (1). 2 undergoes N atom transfer to PPh3 and styrenes to give Ph3P═NH and aziridines, respectively. A Hammett study for various p-substituted styrenes gives a V-shaped plot; this is rationalized by the ability of 2 to function as either an electrophile or a nucleophile. 2 also undergoes hydride transfer reactions with NADH analogues, such as 10-methyl-9,10-dihydroacridine (AcrH2) and 1-benzyl-1,4-dihydronicotinamide (BNAH). A kinetic isotope effect of 7.3 was obtained when kinetic studies were carried out with AcrH2 and AcrD2. The reaction of 2 with NADH analogues results in the formation of [MnV(N)(TAML-H+)]- (3), which was characterized by ESI/MS, IR spectroscopy, and X-ray crystallography. These results indicate that this reaction occurs via an initial "separated CPET"(separated concerted proton-electron transfer) mechanism; that is, there is a concerted transfer of 1 e- + 1 H+ from AcrH2 (or BNAH) to 2, in which the electron is transferred to the MnVI center, while the proton is transferred to a carbonyl oxygen of TAML rather than to the nitrido ligand.
- Shi, Huatian,Lee, Hung Kay,Pan, Yi,Lau, Kai-Chung,Yiu, Shek-Man,Lam, William W. Y.,Man, Wai-Lun,Lau, Tai-Chu
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supporting information
p. 15863 - 15872
(2021/09/30)
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- METHOD FOR SYNTHESIZING AN N-UNSUBSTITUTED OR N-SUBSTITUTED AZIRIDINE
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Process for preparing an N-unsubstituted or N-substituted aziridine of the formula which comprises reacting an olefin of the formula I where R1 to R5 are each, independently of one another, hydrogen, a linear or branched alkyl radica
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Page/Page column 4
(2010/08/07)
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- CEPHALOTAXUS ESTERS, METHODS OF SYNTHESIS, AND USES THEREOF
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The present invention provides novel cephalotaxus esters, syntheses thereof, and intermediates thereto. The invention also provides pharmaceutical compositions comprising a compound of the present invention and methods of using said compounds or compositions in the treatment of proliferative diseases (e.g., benign neoplasm, cancer, inflammatory disease, autoimmune disease, diabetic retinopathy) and infectious disease. The invention further provides methods of using said compounds or compositions in the treatment of multidrug resistant cancer.
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Page/Page column 79
(2009/12/28)
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- Synthesis of antiproliferative cephalotaxus esters and their evaluation against several human hematopoietic and solid tumor cell lines: Uncovering differential susceptibilities to multidrug resistance
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Deoxyharringtonine (2), homoharringtonine (3), homodeoxyharringtonine (4), and anhydroharringtonine (5) are reported to be among the most potent members of the antileukemia alkaloids isolated from the Cephalotaxus genus. Convergent syntheses of these four natural products are described, each involving novel synthetic methods and strategies. These syntheses enabled evaluation of several advanced natural and non-natural compounds against an array of human hematopoietic and solid tumor cells. Potent cytotoxicity was observed in several cell lines previously not challenged with these alkaloids. Variations in the structure of the ester chain within this family of alkaloids confer differing activity profiles against vincristine-resistant HL-60/RV+, signalling new avenues for molecular design of these natural products to combat multi-drug resistance.
- Eckelbarger, Joseph D.,Wilmot, Jeremy T.,Epperson, Matthew T.,Thakur, Chandar S.,Shum, David,Antczak, Christophe,Tarassishin, Leonid,Djaballah, Hakim,Gin, David Y.
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supporting information; experimental part
p. 4293 - 4306
(2009/05/07)
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- Conformationally restricted aza-BODIPY: Highly fluorescent, stable near-infrared absorbing dyes
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Novel NIR fluorescent, conformational restricted aza-dipyrromethene boron difluoride (aza-BODIPY) dyes were prepared by an efficient process. Such conformational restricted aza-BODIPY dyes possess intense absorption, strong fluorescence, high chemical and
- Zhao, Weili,Carreira, Erick M.
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p. 7254 - 7263
(2007/10/03)
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- Synthesis, Molecular Symmetry, and Chemical Reactivity of C-Aryl-Substituted Phosphoraziridines
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P,P-Bis- and P,P,P-tris(1-aziridinyl)phosphoramides containing aryl-substituted aziridine moieties, including para-substituted 2-phenylaziridines, an optically active aziridine, and all the possible C-aryl regioisomers of diphenylaziridine were prepared b
- Perlman, Michael E.,Bardos, Thomas J.
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p. 1761 - 1767
(2007/10/02)
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- Determination des pKa et reaction d'ouverture acide de quelques alkyl-2 et aryl-2 aziridines
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Some 2-para substituted aryl aziridines (with pY = CH3O-, CH3-, H-, and Cl-) have been prepared.Their ring opening reaction in acidic medium has been studied and compared with those of two aliphatic aziridines : 2 methyl- and 2,2 dimethyl-aziridine.In aqueous solvent, the addition of HCl, HBr, and HI to the aromatic aziridines leads exclusively to the secondary halogen product, due to the nucleophilic attack on the benzylic carbon.The hydrolysis reaction competes with the addition reaction and is very important for the para methoxy 2-phenyl aziridine.In ethyl alcohol (anhydrous solvent), the hydrohalogenation reaction leads exclusively to halogeno amine with a secondary halogen.The solvolysis reaction, leading to amino-ether, is far less important than in water (excepted for the para methoxy 2-phenyl aziridine).In both solvents, the importance of the solvolysis depends on the HX concentration, as well as the nucleophilic strength of the halogen.The pKa values of these aziridines have been measured, as well as those of 2-phenyl 1-amino 2-ethanol.A linear plot is obtained for the pKa versus ?+p of Brown ; the slopes are respectively -2.8 and 0.Therefore the aromatic aziridines seem to have a behavior similar to that of anilines.
- Lamaty, Gerard,Sanchez, Jean-Yves,Sivade, Andre,Wylde, James
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p. 1261 - 1266
(2007/10/02)
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