65638-78-0Relevant academic research and scientific papers
Single enantiomer free-radical chemistry - Lewis acid-mediated reductions of racemic halides using chiral non-racemic stannanes
Dakternieks, Dainis,Perchyonok, V. Tamara,Schiesser, Carl H.
, p. 3057 - 3068 (2007/10/03)
Additions of one to two equivalents of Lewis acids that include magnesium salts to free-radical reduction reactions involving ester functionalized radicals and (1R,2S,5R)-menthyldiphenyltin hydride 4, bis((1R,2S,5R)-menthyl) phenyltin hydride 5, tris((1R,
The enzyme-catalysed stereoselective transesterification of phenylalanine derivatives in supercritical carbon dioxide
Smallridge, Andrew J.,Trewhella, Maurie A.,Wang
, p. 259 - 262 (2007/10/03)
The subtilisin Carlsberg catalysed transesterification of N-acetyl phenylalanine methyl ester (1), N-acetyl phenylalanine ethyl ester (2), N-trifluoroacetyl phenylalanine methyl ester (3) and N-trifluoroacetyl phenylalanine ethyl ester (4) was studied in supercritical carbon dioxide. The water content of the reaction affects the reactivity of the system; for the transesterification of the methyl esters with ethanol the optimum concentration of water was determined to be about 0.74 M, while for the transesterification of the ethyl esters with methanol the optimum concentration of water was about 1.3 M. The conversion is also dependent upon the concentration of alcohol; for ethanol, 2% v/v gives the maximum conversion, whilst for methanol, only 0.8-1. 2% v/v is required. This is probably due to a difference in the solubility of the substrates in the two alcohol/supercritical carbon dioxide mixtures. The reaction is highly stereoselective, in all cases no evidence for reaction of the D-isomer could be detected by chiral gas chromatography.
Chiral Recognition of Amino Acid Derivatives: An NMR Investigation of the Selector and the Diastereomeric Complexes
Spisni, Alberto,Corradini, Roberto,Marchelli, Rosangela,Dossena, Arnaldo
, p. 684 - 688 (2007/10/02)
A tetraamidic selector containing two chiral synthons ((S)-phenylalanine) spaced by a 3,6,9-oxadecanoyl bridge (Phe-3-O-TA) (1) was used as stationary phase in capillary GC to perform chiral resolution of N-TFA-amino esters.In this paper we report an investigation on the mechanism of chiral recognition by NMR spectroscopy (1D and 2D, COSY, NOESY, and J-resolved experiments and 13C relaxation times).First the conformation of the selector in CDCl3 and CD3OD was studied to evaluate the structural features that might justify the enantiomeric discrimination ability.Thenthe self-associations of the selector and of the enantiomers (S)- and (R)-methyl (2a,2b) and (S)- and (R)-n-butyl N-TFA-phenylalaninate (3a, 3b) were investigated at variable temperature and concentration in CDCl3.Finally, titration experiments were carried out to detect the sites of the binding interactions between the selector and the enantiomers.A simple recognition mode is proposed to account for both the enantioselectivity of the phase and the elution order of the enantiomers observed in GC (t'RS).This is the first spectroscopic study on the mechanism of chiral recognition in GC concerning the real phase and not a model system.
