Efficient Enantioselective Synthesis of Methyl Esters of α-Unsubstituted β-Hydroxy Acids via Asymmetric Aldol-Type Addition of Chiral Boron Enolates of (Methylthio)acetic Acid to Aldehydes
作者:Francesco Fringuelli、Oriana Piermatti、Ferdinando Pizzo
DOI:10.1055/s-1996-4365
日期:1996.10
The aldol-type addition of chiral boron enolates of (methylthio)-acetic acid to various aldehydes gives α-(methylthio)-β-hydroxy acids stereoselectively and with good yields. The desulfenylation of methyl esters of the condensation adducts allows methyl esters of α-unsubstituted β-hydroxy acids to be obtained with high ee. Derivatives of (+)-2- and (+)-3-carene were used as chiral inducers. The enantioselectivity and diastereoselectivity of the aldol-type addition are efficaciously controlled by the SMe group in the α-position of the enolate and by the type of chiral ligand used.
(甲硫基)乙酸的手性硼烯醇盐与各种醛进行aldol型加成反应,可以立体选择性地并以良好产率得到α-(甲硫基)-β-羟基酸。通过脱硫作用,可以将缩合加合物的甲酯转化为高对映体纯度的α-未取代-β-羟基酸的甲酯。使用(+)-2-蒎烯和(+)-3-蒎烯的衍生物作为手性诱导剂。aldol型加成的对映选择性和非对映选择性有效地受到烯醇盐α-位上的SMe基团和所用手性配体类型的控制。