Stereoselective Michael Addition of Glycine Anions to Chiral Fischer Alkenylcarbene Complexes. Asymmetric Synthesis of beta-Substituted Glutamic Acids.
J Org Chem
; 64(18): 6554-6565, 1999 Sep 03.
Article
em En
| MEDLINE
| ID: mdl-11674657
ABSTRACT
The reaction of lithium enolates of achiral N-protected glycine esters with chiral alkoxyalkenylcarbene complexes of chromium provided the corresponding Michael adducts with either high anti or syn selectivity depending on the nature of the nitrogen protecting group, and high diastereofacial selectivity when carbene complexes containing the (-)-8-phenylmenthyloxy group were employed. Subsequent oxidation of the metal-carbene moiety followed by deprotection of the amine group and hydrolysis of both carboxylic esters afforded enantiomerically enriched 3-substituted glutamic acids of natural as well as unnatural stereochemistry. Alternatively, when the deprotection step was performed previously to the oxidation, cyclic aminocarbene complexes were formed, which finally led to optically active 3-substituted pyroglutamic acids.
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Base de dados:
MEDLINE
Idioma:
En
Ano de publicação:
1999
Tipo de documento:
Article