4276-74-8Relevant articles and documents
HPLC separation of 2-aryloxycarboxylic acid enantiomers on chiral stationary phases
Charushin, V. N.,Chulakov, E. N.,Krasnov, V. P.,Levit, G. L.,Sadretdinova, L. Sh.,Tumashov, A. A.,Vakarov, S. A.
, p. 900 - 907 (2021/06/07)
The possibility for separating enantiomers of a number of practically significant 2-aryloxycarboxylic acids was studied by normal- and reversed-phase HPLC on popular chiral stationary phases. The best separation parameters were achieved on the chiral phases with the polysaccharide base Chiralcel OD-H and Chiralpack AD under the normal-phase HPLC conditions. The (S)- and (R)-enantiomers of 2-(1-naphthyloxy)- and 2-(2-iodophenoxy)propionic acids with enantiomeric excess ee >99% were isolated using preparative chiral HPLC.
Mutual Kinetic Resolution of Racemic 3,4-Dihydro-3-methyl-2H-[1,4]benzoxazines with Acyl Chlorides of Racemic O-Phenyllactic Acids and DFT Modelling of Transition States
Korolyova, Marina A.,Vakarov, Sergey A.,Kozhevnikov, Dmitry N.,Gruzdev, Dmitry A.,Levit, Galina L.,Krasnov, Victor P.
, p. 4577 - 4585 (2018/09/06)
The effect of the electronic nature of the para substituent on the aromatic ring of 2-aryloxypropionyl chlorides on the stereochemical outcome of the acylation of 3,4-dihydro-3-methyl-2H-[1,4]benzoxazine and its 7,8-difluoro-containing analogue has been studied. The geometries of the diastereoisomeric transition states and the corresponding Gibbs free enthalpies of activation were determined through DFT calculations at the COSMO-CH2Cl2-B3LYP-D3-gCP/def2-TZVP (or def2-SVP)//B3LYP-D3-gCP/def2-SVP level of theory. It has been found that a low-cost quantum chemical calculation at a chosen level of theory describes well the quantitative dependence of the selectivity of acylation on the structures of the reagents. The obtained results indicate that aromatic interactions between the reagents play a significant role in the process of stereodifferentiation, ensuring high selectivity of the acylation of benzoxazines with 2-aryloxyacyl chlorides.
Metal ions dramatically enhance the enantioselectivity for lipase-catalysed reactions in organic solvents
Okamoto, Takashi,Yasuhito, Ebara,Ueji, Shin-Ichi
, p. 1147 - 1153 (2008/02/03)
We propose a simple and a powerful method to enhance the enantioselectivity for lipase-catalysed transformations in organic solvents by an addition of metal ion-containing water to the reaction mixture. In this paper, various metal ions such as LiCl or MgCl2 are tested to improve the enantioselectivity for the model reactions. The enantioselectivities obtained are dramatically enhanced, the E values of which are about 100-fold as compared with the ordinary conditions without a metal ion, for example, E = 200 by addition of LiCl. Furthermore, lowering the reaction temperature led to an almost perfect enantioselectivity of lipase in the presence of a metal ion, for example, E = 1300 by addition of LiCl. Also, a mechanism for the drastic enhancement by metal ions is discussed briefly on the basis of the EPR spectroscopic study and the initial rate for each enantiomer of the substrate. The Royal Society of Chemistry 2006.
