Asymmetric Reduction of 3-Ketoproline Ethyl Ester by Modified Borohydrides and Various Vegetables
作者:Wibowo, Agustono、Shaameri, Zurina、Mohammat, Mohd Fazli、Hamzah, Ahmad Sazali
DOI:10.5012/jkcs.2017.61.5.244
日期:——
Reduction of ($\pm}$)-3-ketoproline ethyl ester (1) by $NaBH_4$ in the presence of $CaCl_2$ and $MgCl_2$ as the chelating agents gave selective products cis-3(R/S)-alcohols, while reduction by $NaBH_4$ alone or chelated with $NiCl_2$ and $AlBr_3$ gave mixtures of cis- and trans-alcohols. The reduction of ($\pm}$)-1 by various vegetables however, gave exclusively the cis-alcohol as the major and trans-alcohol as the minor. On the contrary, reduction of ($\pm}$)-1 by carrot afforded a mixture of cis- and trans-alcohols, in which the trans-alcohol exists as the major product. In addition, we found that this biocatalyst selectively converted S-enantiomer of ($\pm}$)-1 to the cis-alcohol, and R-enantiomer to a mixture of cis- and trans-alcohols with cis-alcohol as the major product. This fact prompted us to use various fresh plant tissues for stereoselective reduction of diverse types of pyrrolidinones, as its stereoselectivity towards racemic mixtures is higher compared to that using chemical reducing agents.
在$CaCl_2$和$MgCl_2$作为螯合剂存在的情况下,用$NaBH_4$还原($-$\pm}$)-3-酮脯氨酸乙酯(1)得到的选择性产物是顺式-3(R/S)-醇,而单独用$NaBH_4$还原或与$NiCl_2$和$AlBr_3$螯合还原得到的则是顺式和反式醇的混合物。然而,用各种蔬菜还原($-$\pm}$)-1时,得到的产物主要是顺式醇,反式醇含量很少。相反,用胡萝卜还原($-$\pm}$)-1时,得到的产物是顺式和反式醇的混合物,其中反式醇是主要产物。此外,我们发现这种生物催化剂选择性地将($-$\pm}$)-1的S对映体转化为顺式醇,将R对映体转化为顺式和反式醇的混合物,其中顺式醇是主要产物。这一事实促使我们使用各种新鲜植物组织对不同类型的��