Stereoselective Michael addition of glycine anions to chiral Fischer alkenylcarbene complexes. Asymmetric synthesis of beta-substituted glutamic acids

Citation
J. Ezquerra et al., Stereoselective Michael addition of glycine anions to chiral Fischer alkenylcarbene complexes. Asymmetric synthesis of beta-substituted glutamic acids, J ORG CHEM, 64(18), 1999, pp. 6554-6565
Citations number
83
Categorie Soggetti
Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
JOURNAL OF ORGANIC CHEMISTRY
ISSN journal
00223263 → ACNP
Volume
64
Issue
18
Year of publication
1999
Pages
6554 - 6565
Database
ISI
SICI code
0022-3263(19990903)64:18<6554:SMAOGA>2.0.ZU;2-J
Abstract
The reaction of lithium enolates of achiral N-protected glycine esters with chiral alkoxyalkenylcarbene complexes of chromium provided the correspondi ng Michael adducts with either high anti or syn selectivity depending on th e nature of the nitrogen protecting group, ana high diastereofacial selecti vity when carbene complexes containing the (-)-8-phenylmenthyloxy group wer e employed. Subsequent oxidation of the metal-carbene moiety followed by de protection of the amine group and hydrolysis of both carboxylic esters affo rded enantiomerically enriched 3-substituted glutamic acids of natural as w ell as unnatural stereochemistry. Alternatively, when the deprotection seep was performed previously to the oxidation, cyclic aminocarbene complexes w ere formed, which finally led to optically active 3-substituted pyroglutami c acids.