53940-83-3Relevant articles and documents
Memory of chirality of tertiary aromatic amides: A simple and efficient method for the enantioselective synthesis of quaternary α-amino acids
Branca, Mathieu,Pena, Sebastien,Guillot, Regis,Gori, Didier,Alezra, Valerie,Kouklovsky, Cyrille
scheme or table, p. 10711 - 10718 (2009/12/04)
A new methodology for the asymmetric synthesis of quaternary R-substituted amino acids using memory of chirality has been developed. The strategy utilizes the dynamic axial chirality of tertiary aromatic amides to memorize the initial chirality of an α-amino acid during an enolization step. Starting from five different L-amino acids, the corresponding oxazolidin-5-ones containing a tertiary aromatic amide group have been synthesized in one step and then alkylated with various electrophiles, with good yields and enantioselectivities (up to 96% and up to >99% after recrystallization). One-step deprotection affords enantioenriched or enantiopure quaternary α-amino acids. We describe here the optimization process, the results obtained in each series and a plausible explanation, based on NMR studies, DFT calculations and crystallographic structures. The methodology presented herein constitutes an efficient synthesis of enantiopure quaternary R-amino acids (three steps only) starting from tertiary L-amino acids, without any external source of chirality.
Tertiary aromatic amide for memory of chirality: Access to enantioenriched α-substituted valine
Branca, Mathieu,Gori, Didier,Guillot, Regis,Alezra, Valerie,Kouklovsky, Cyrille
, p. 5864 - 5865 (2008/09/20)
A new methodology for the asymmetric synthesis of quaternary α-substituted amino acids using memory of chirality has been developed. This strategy employs dynamic axial chirality of tertiary aromatic amides to memorize the initial chirality of an α-amino acid during the enolization step. Starting from l-valine, an oxazolidin-5-one containing a tertiary aromatic amide was synthesized in one step and then alkylated with various electrophiles with good yield and enantioselectivity (up to 96%). Quaternary products can be obtained enantiomerically pure by recrystallization. One-step deprotection affords enantioenriched (S)-α-methyl valine (ee = 94%) or enantiopure (S)-α-isopropyl aspartic acid (ee >99%) in only three steps starting from L-valine. Copyright
Synthesis of dipeptides containing α-substituted amino acids; their use as chiral ligands in Lewis-acid-catalyzed reactions
Kaptein, Bernard,Monaco, Vania,Broxterman, Quirinus B.,Schoemaker, Hans E.,Kamphuis, Johan
, p. 231 - 238 (2007/10/02)
L-α-Methylphenylalanine, obtained by enzymatic resolution of the corresponding racemic amide with amidase from Ochrobactrum anthropi NCIMB 40321, was used in the synthesis of dipeptides containing α-substituted amino acids.The 2-hydroxynaphthalene-1-carboxaldehyde Schiff bases of the dipeptides (1 and 2) were tested as Ti(IV) and Al(III) complexes in asymmetric Lewis-acid-catalyzed reactions.Only the Al(III) complex of 2 showed moderate enantioselectivity in the cyanation reaction of benzaldehyde with TMS-CN.
