Erythroselective aldol condensation of amine Free 2-t-butyl-5-methyl-2-phenyl-1,3-dioxolan-4-one lithium enolate synthesis of the ethyl acetolactate enantiomers
摘要:
Generated by halogen metal exchange, the sterically hindered 2-t-butyl-5-methyl-2-phenyl -1,3-dioxolan-4-one lithium enolate reacts in an erythroselective way with acetaldehyde. Separation of the resulting diastereomers, followed by alcoholysis lead to the corresponding enantiomerically pure diols.
The results for the additionreactions of chiral lithium (2S)-enolates of 1,3-dioxolan-4-ones to aldehydes and to acetophenone, yielding the corresponding dioxolanone alcohols have been revised. The results reported herein differ from those reported in the literature, both in product distribution and in the stereochemical assignment of the products. In fact, in several cases no stereocontrol was observed
Cyclic or acyclic α-alkyl-α-hydroxy-β-keto esters were reduced by baker’s yeast with high stereospecificity. In the former case, one enantiomer of the racemic mixture was transformed into optically active trans-dihydroxy compounds, while the remaining α-hydroxy-β-keto ester was enantiopure.