109522-07-8Relevant articles and documents
Enantiocatalytic activity of substituted 5-benzyl-2-(pyridine-2-yl) imidazolidine-4-one ligands
Drabina, Pavel,Karel, Sergej,Panov, Illia,Sedlak, Milos
, p. 334 - 339 (2013/04/23)
Currently, asymmetric synthesis represents one of the main streams of organic synthesis. Although an extensive research has been carried out in this area, the synthesis of chiral compounds with the required enantiomeric purity is still a challenging issue. Herein, we focus on the preparation of new enantioselective catalysts based on pyridine-imidazolidinones. The substituted 5-benzyl-2-(pyridine-2-yl)imidazolidine-4-ones 5-8 were prepared by condensation of chiral amino acid amides (α-methylDOPA and α- methylphenylalanine) with 2-acetylpyridine and pyridine-2-carbaldehyde. The individual isomers of the described ligands 5-8 were separated chromatographically. The copper(II) complexes of these chiral ligands were studied as enantioselective catalysts for the asymmetric Henry reaction of substituted aldehydes with nitromethane or nitroethane. The ligands containing a methyl group at the 2-position of the imidazolidinone ring 6a and 8a exhibit a high degree of enantioselectivity (up to 91% ee). The nitroaldols derived from nitroethane (2-nitropropan-1-ols) were obtained with a comparable enantiomeric purity to derivatives of 2-nitroethanol. This group of ligands represents a new and promising class of enantioselective catalysts, which deserve further attention.
New aspects of β-lactam chemistry: β-lactams as chiral building blocks
Ojima, Iwao,Shimizu, Nobuko,Qiu, Xiaogang,Chen, Hauh-Jyun C.,Nakahashi, Kazuaki
, p. 649 - 658 (2007/10/02)
Recent advances on the new aspects of β-lactam chemistry in which β-lactams are used as chiral building blocks for the synthesis of a variety of α-amino acids, 4α-alkyl-α-aminoacids, oligopeptides, labeled peptides, azetidines, amino alcohols, etc., are reviewed.The topics include new and effective routes to dipeptides via homochiral β-lactams obtained by extremely stereoselective cycloadditions of chiral ketenes to chiral imines, a novel route to labeled peptides through extremely stereoselective and stereospecific reductive cleavage of β-lactams on a palladium catalyst, and new efficient syntheses of α-alkyl-α-amino acids and their peptides by the highly effective asymmetric alkylations of β-lactam lithium enolates followed by hydrogenolysis or Birch reduction.Mechanism of those highly selective unique reactions are discussed.
