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1.
Angew Chem Int Ed Engl ; 54(15): 4557-60, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25663427

RESUMO

The formation of highly substituted carbon centers using catalysis has been a widely sought after goal, but complexes of highly substituted carbon atoms with transition metals are rare, and the factors that affect the relative stability of complexes with differentially substituted carbon atoms are poorly understood. In this study, a set of equilibrating alkyl-palladium complexes were subtly tuned to form either a primary or trisubstituted alkyl complex as the more thermodynamically favored state, depending on either the substrate or reaction conditions. An X-ray crystal structure of the trisubstituted alkyl-palladium complex is presented and compared with the corresponding primary alkyl complex. The mechanism for rearrangement and the factors that drive the change in stability are discussed.

3.
J Am Chem Soc ; 135(24): 8854-6, 2013 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-23734771

RESUMO

An enantioselective Pd-catalyzed vicinal diamination of unactivated alkenes using N-fluorobenzenesulfonimide as both an oxidant and a source of nitrogen is reported. The use of Ph-pybox and Ph-quinox ligands afforded differentially protected vicinal diamines in good yields with high enantioselectivities. Mechanistic experiments revealed that the high enantioselectivity arises from selective formation of only one of four possible diastereomeric aminopalladation products of the chiral Pd complex. The aminopalladation complex was characterized by X-ray crystallography.

4.
ACS Chem Biol ; 8(4): 749-57, 2013 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-23330600

RESUMO

The Morita-Baylis-Hillman reaction forms a carbon-carbon bond between the α-carbon of a conjugated carbonyl compound and a carbon electrophile. The reaction mechanism involves Michael addition of a nucleophile catalyst at the carbonyl ß-carbon, followed by bond formation with the electrophile and catalyst disassociation to release the product. We used Rosetta to design 48 proteins containing active sites predicted to carry out this mechanism, of which two show catalytic activity by mass spectrometry (MS). Substrate labeling measured by MS and site-directed mutagenesis experiments show that the designed active-site residues are responsible for activity, although rate acceleration over background is modest. To characterize the designed proteins, we developed a fluorescence-based screen for intermediate formation in cell lysates, carried out microsecond molecular dynamics simulations, and solved X-ray crystal structures. These data indicate a partially formed active site and suggest several clear avenues for designing more active catalysts.


Assuntos
Proteínas/metabolismo , Catálise , Cinética , Simulação de Dinâmica Molecular , Proteínas/química , Difração de Raios X
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