Selective hydroalkoxycarbonylation of enamides to N-acyl amino acid esters: Synthetic applications and theoretical studies
N-acyl amino acid esters are easily accessible from enamides by cobalt-catalyzed hydroalkoxycarbonylation in moderate to excellent yield. An important reaction parameter for selective carbonylation is the use of low hydrogen partial pressure, which prevents hydrogenation as a side reaction. The reported method is applicable to various enamides and alcohols. A DFT calculation of the catalytic cycle explains the preferred pathway of this reaction.
Klaus,Neumann,Jiao,Von Wangelin, A. Jacobi,G?rdes,Strübing,Hübner,Hateley,Weckbecker,Huthmacher,Riermeier,Beller
The potential of two chiral amidines and three non-chiral boranes in the metal-free hydrogen activation was explored. The resulting chiral amidiunium borohydride salts were investigated in asymmetric hydrogenation reactions of ketimines, activated double bonds and dehydro amioacid esters.
K?ring, Laura,Paradies, Jan,Roesky, Peter W.,Sitte, Nikolai A.
We report an achiral bisphosphine rhodium complex equipped with a binding site for the recognition of chiral anion guests. Upon binding small chiral guests-cofactors-the rhodium complex becomes chiral and can thus be used for asymmetric catalysis. Screening of a library of cofactors revealed that the best cofactors lead to hydrogenation catalysts that form the products with high enantioselectivity (ee?s up to 99%). Interestingly, a competition experiment shows that even in a mixture of 12 cofactors high ee is obtained, indicating that the complex based on the best cofactor dominates the catalysis.
Dydio, Pawel,Rubay, Christophe,Gadzikwa, Tendai,Lutz, Martin,Reek, Joost N. H.
supporting information; experimental part
p. 17176 - 17179
(2011/12/13)
ENANTIOSELECTIVE HYDROLYSIS BY BAKER'S YEAST - II. ESTERS OF N-ACETYL AMINO ACIDS
D-N-Acetyl amino acid esters were obtained via enantioselective hydrolysis of their racemates by use of fermenting yeast.Evidence is given that proteinases are the enzymes involved.
Glaenzer, B. I.,Faber, K.,Griengl, H.
p. 771 - 778
(2007/10/02)
A general and accurate nmr determination of the enantiomeric purity of α-aminoacids and α-aminoacid derivatives
Derivatization of α-aminoacids, α-aminoesters and α-aminolactones as N-acetyl derivatives allow the accurate NMR determination of the enantiomeric purity. In these conditions the major coordination site with a chiral shift reagent will correspond to the NMR observation site. Experimental factors leading to the highest ΔΔδ values are ascertained. No straightforward correlation with absolute configurations can be established.
Calmes, Monique,Daunis, Jacques,Jacquier, Robert,Verducci, Jean
p. 2285 - 2292
(2007/10/02)
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