Search results for "Hydride"
showing 10 items of 322 documents
CCDC 1508074: Experimental Crystal Structure Determination
2016
Related Article: Christopher G. Gianopoulos, Bartosz Zarychta, Simone Cenedese, Vladimir V. Zhurov, A. Alan Pinkerton|2016|J.Phys.Chem.A|120|4059|doi:10.1021/acs.jpca.6b03787
CCDC 1436954: Experimental Crystal Structure Determination
2016
Related Article: Kaspars Traskovskis, Valdis Kokars, Andrejs Tokmakovs, Igors Mihailovs, Edgars Nitiss, Marina Petrova, Sergey Belyakov, Martins Rutkis|2016|J.Mater.Chem.C|4|5019|doi:10.1039/C6TC00203J
Rethinking Cysteine Protective Groups:S-Alkylsulfonyl-l-Cysteines for Chemoselective Disulfide Formation
2016
The ability to reversibly cross-link proteins and peptides grants the amino acid cysteine its unique role in nature as well as in peptide chemistry. We report a novel class of S-alkylsulfonyl-l-cysteines and N-carboxy anhydrides (NCA) thereof for peptide synthesis. The S-alkylsulfonyl group is stable against amines and thus enables its use under Fmoc chemistry conditions and the controlled polymerization of the corresponding NCAs yielding well-defined homo- as well as block co-polymers. Yet, thiols react immediately with the S-alkylsulfonyl group forming asymmetric disulfides. Therefore, we introduce the first reactive cysteine derivative for efficient and chemoselective disulfide formation…
Increased dynamic effects in a catalytically compromised variant of Escherichia coli dihydrofolate reductase
2013
Isotopic substitution (15N, 13C, 2H) of a catalytically compromised variant of Escherichia coli dihydrofolate reductase, EcDHFR-N23PP/S148A, has been used to investigate the effect of these mutations on catalysis. The reduction of the rate constant of the chemical step in the EcDHFR-N23PP/S148A catalyzed reaction is essentially a consequence of an increase of the quasi-classical free energy barrier and to a minor extent of an increased number of recrossing trajectories on the transition state dividing surface. Since the variant enzyme is less well set up to catalyze the reaction, a higher degree of active site reorganization is needed to reach the TS. Although millisecond active site motion…
Synthesis of new half sandwich tetrachloro derivatives of molybdenum(V) and tungsten(V). X-ray structures of (C5HPri4)W(CO)3(CH3) and (C5Et5)WCl4
2002
International audience; The new synthetic intermediates (Ring)MCl4 [Ring=C5HPri4 or 4Cp, M=Mo, 2; Ring=C5Et5 or VCp, M=W, 4, Ring=4Cp, M=W, 6] containing sterically protecting cyclopentadienyl ligands have been synthesized. Along the synthetic pathway to 2, it was found that the treatment of [4CpMo(CO)3]− with an aqueous ferric solution according to the well established Manning procedure affords the hydride compound 4CpMo(CO)3H (1) by hydrolysis rather than the expected neutral dimer by oxidation. Compound 1 could be converted, however, to 2 upon oxidation with PhICl2 in good yields. Compound 4 is shown by a single crystal X-ray analysis to adopt a monomeric four-legged piano stool structur…
Unique regioselectivity in the C(sp3)-H α-alkylation of amines: the benzoxazole moiety as a removable directing group.
2014
The benzoxazol-2-yl- substituent was found to act as a removable activating and directing group in the Ir-catalyzed alkylation of C(sp(3))-H bonds adjacent to nitrogen in secondary amines. It can be easily introduced by oxidative coupling or by an SNAr reaction, and it can be removed by hydroxide or by hydride reduction. For 1,2,3,4-tetrahydroisoquinolines, activation exclusively takes place in the 3-position. A variety of activated as well as unactivated terminal olefins are suitable reaction partners.
Regioselective Epoxide Ring Opening. Steroselective Synthesis of a Tetrahydropyran Ring
1998
The stereoselective synthesis of a 2-substituted tetrahydropyran with adjacent alkoxy-bearing stereogenic centre is described. The key steps of this synthesis were the stereoselective epoxidation of an allylic alcohol and the regioselective epoxide ring opening by lithium aluminum hydride. The regio and stereoselective synthesis of a trihydroxyselenide and a trihydroxysulfide is also described. The latter compounds are not suitable for cyclization to tetrahydrofuran ring.
Generation, Characterization, and Electrochemical Behavior of the Palladium-Hydride Cluster [Pd3(dppm)3(3-CO)(3-H)]+ (dppm=Bis(diphenylphosphinometha…
2007
Addition of formate on the dicationic cluster [Pd(3)(dppm)(3)(mu(3)-CO)](2+) (dppm=bis(diphenylphosphinomethane) affords quantitatively the hydride cluster [Pd(3)(dppm)(3)(mu(3)-CO)(mu(3)-H)](+). This new palladium-hydride cluster has been characterised by (1)H NMR, (31)P NMR and UV/Vis spectroscopy and MALDI-TOF mass spectrometry. The unambiguous identification of the capping hydride was made from (2)H NMR spectroscopy by using DCO(2) (-) as starting material. The mechanism of the hydride complex formation was investigated by UV/Vis stopped-flow methods. The kinetic data are consistent with a two-step process involving: 1) host-guest interactions between HCO(2) (-) and [Pd(3)(dppm)(3)(mu(3…
Zur Acetylierung von Spironolacton, Canrenon und 2-Methylencanrenon
1995
Bei der Umsetzung der Titelverbindungen mit Acetanhydrid und Acetylchlorid werden das 3,5-Dien-3-yl-acetat 2, die isomeren 2,4,6- und 3,5,7-Trien-3-yl-acetate 3 und 4 sowie das 2,4,6,8(14)-Tetraen-3-yl-acetat 7 erhalten. Hydrolyse von 7 liefert das 2α-Methl-8,14-didehydro-canrenon (9). 7 und 9 wurden auf ihre Bindungsfahigkeit gegenuber Hormon-Rezeptoren sowie den Serumproteinen SHBG und CBG gepruft: Die Substanzen erwiesen sich als inaktiv. Acetylation of Spironolactone, Canrenone, and 2-Methylene Canrenone Reaction of the title compounds with acetic anhydride and acetyl chloride yields the 3,5-dien-3-yl acetate 2 the isomeric 2,4,6- and 3,5,7-trien-3-yl acetates 3 and 4 as well as the 2,4…
Early lanthanide organometallic hydrides: electronic and steric control of the stability
2000
Abstract Steric and electronic effects on the stability of early lanthanide, neodymium and samarium, organometallic hydrides are discussed. The instability of (tmp)2SmH (tmp=tetramethylphospholyl) is attributed to electronic factors and the low stability of (tBuC5H4)2SmH is related to steric reasons. The analogous neodymium hydride (tBuC5H4)2NdH, could not be obtained, whereas the more hindered triethylborohydride was formed. Access to bisphospholyl bridged heterobimetallic ruthenium–lanthanide hydrides is also related to the size of the lanthanide atom. The bimetallic structures are accessible for lanthanides of ionic radii smaller than 1 A. The role of organometallic hydrides versus alkyl…