14603-76-0Relevant 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
supporting information; experimental part, 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.
Asymmetric synthesis of α,α-disubstituted amino acids by diastereoselective functionalization of enantiopure phenyloxazinones, derivatives of asymmetric Strecker reaction products of aldehydes
Ding, Ke,Ma, Dawei
, p. 6361 - 6366 (2007/10/03)
Esterification of the asymmetric Strecker reaction products of a suitable aldehyde and (R)-phenylglycinol followed by lactonization and alkylation provides chiral oxazinones 5. Treatment of the enolates of 5 with active alkyl halides, or aldehydes provided the corresponding functionalization products with high diastereoselectivity. The configuration of newly created quaternary carbon is S for the products coupled with simple alkyl halides and aldehydes, and R for the products coupled with methyl bromoacetate. Deprotection of these products afforded the corresponding enantiopure α,α-dialkyl amino acids.
Asymmetric synthesis of α-methyl α-amino acids by diastereoselective alkylation of optically active 6-isopropyl-3-methyl-2,3-dihydro-6H-1,4-oxazin-2-ones
Chinchilla,Falvello,Galindo,Najera
, p. 995 - 997 (2007/10/03)
At room temperature already highly diastereoselective alkylation of the new, cyclic, chiral alanine ester derivatives (6R)-1 can be achieved with either K2CO3 as base under solid liquid phase-transfer catalysis or Pd catalysis under neutral conditions. The products (3S,6R)-2 can be easily hydrolyzed to form (S)-α-methyl α-amino acids.
