Diastereoselective Reduction of Chiral α-Ketoamides Derived from (S)-Proline Esters with Sodium Borohydride. Preparation of Optically Active α-Hydroxy Acids
Diastereoselective reductions of chiral α-ketoamides (3) derived from (S)-proline esters (2) with sodium borohydride were examined.Hydrolysis of the reduction products afforded optically active α-hydroxy acids (5) in good enantiomeric excesses (e.e.).The most influential factor of the asymmetric induction was the effect of using a mixed hydroxylic and non-hydroxylic solvent.The degree of asymmetric induction varied considerably with the ratio of alcohol and tetrahydrofuran (THF) in the mixed solvent.With aromatic ketoamides (3), higher asymmetric induction occured in a mixed alcohol-THF solvent than in the corresponding individual solvents.
Soai, Kenso,Hasegawa, Hitoshi
p. 769 - 772
(2007/10/02)
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