Asymmetric Synthesis of the Both Enantiomers of α-Hydroxy Acids by the Diastereoselective Reduction of Chiral α-Keto Amides with (Complex) Metal Hydrides in the Presence of Metallic Salt
metallic salts and the reducing reagents in the diastereoselective reduction of chiral α-keto amides derived from (S)-proline methylester were examined. Lithium borohydride afforded (S)-α-hydroxy acids, whereas diisobutylaluminum hydride afforded (R)-isomers. In the presence of lithium bromide, reduction with LiBH4 afforded (S)-mandelic acid in over 80% e.e.
检查了金属盐和还原剂在非对映选择性还原(S)-脯氨酸甲酯衍生的手性 α-酮酰胺中的作用。硼氢化锂提供 (S)-α-羟基酸,而二异丁基氢化铝提供 (R)-异构体。在溴化锂存在下,用 LiBH4 还原得到超过 80% ee 的 (S)-扁桃酸
Unusual effect of a mixed solvent on the asymmetric reduction of chiral α-keto-amides with sodium borohydride
The mixed solvent tetrahydrofuran + methanol (99 : 1) was much more effective than the individual solvents in the asymmetric reduction of chiral α-keto-amides with sodiumborohydride; this solventeffect in asymmetric induction is unprecedented.