RESUMO
Lipase-catalyzed acylation of racemic alcohols with a highly fluorinated acyl donor allows their kinetic resolution accompanied by the simultaneous enantiomer-selective fluorous phase labeling. Both the tagged and the untagged enantiomer can be separated without chromatography by a very efficient partition between a fluorous and an organic phase. The method has been successfully applied to the resolution of typically racemic secondary alcohols of low molecular weight. The fluorous label can be recovered quantitatively.
Assuntos
Álcoois/química , Burkholderia cepacia/enzimologia , Química Orgânica/métodos , Hidrocarbonetos Fluorados/química , Lipase/metabolismo , Acilação , Catálise , Cromatografia Líquida de Alta Pressão , Cinética , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Estereoisomerismo , Compostos de Vinila/químicaRESUMO
No chromatography is necessary to separate a racemic alcohol into its enantiomers. A highly fluorinated acyl residue was tranferred in an enantiomer-selective manner onto a racemic alcohol in the presence of a lipase [Eq. (1)]. The labeled enantiomer was separated from the unlabeled one by a simple but very efficient partition between fluorous and organic phases.
RESUMO
A highly enantioselective and diastereoselective Claisen rearrangement of N-arylimidates derived from an axially chiral binaphthylamine auxiliary is reported. Upon deprotonation of the imidates with lithium diethylamide, the resultant azaenolates rearrange at 0 degrees C to give anti alpha,beta-disubstituted, gamma,delta-unsaturated N-binaphthyl amides. A iodolactonization/zinc reduction sequence readily converts these amides into the corresponding carboxylic acids of 91-95% ee and allows an efficient recovery of the chiral auxiliary.
