Carbohydrate-derived partners display remarkably high stereoselectivity in aldol coupling reactions
作者:Kuo Long Yu、Sheetal Handa、Raymond Tsang、Bert Fraser-Reid
DOI:10.1016/s0040-4020(01)80916-9
日期:1991.1
Aldol condensation between 3-keto and aldehyde sugars have been studied. The enolate 3 reacts with aldehydes preferentially from the β-face to give axial C2 condensation products. However, if the reaction conditions are not controlled properly some C2 epimerization may be observed. With respect to the aldehyde partner, facial selectivity can be predicted on the basis of the preferred, permissible chelation
已经研究了3-酮与醛糖之间的醛醇缩合。烯醇化物3优先从β面与醛反应,以产生轴向的C 2缩合产物。但是,如果未适当控制反应条件,则可能会观察到某些C2差向异构化。对于醛伴侣,可以基于优选的,允许的螯合模式来预测面部选择性。因此,α/β螯合(可能发生)会产生Cram产物,而α-螯合会产生抗Cram产物。对于主要(C2轴)产物,新伪造的C2C7键周围的立体化学可以通过C7-(S)缩合产物的J 2,7 = 8–10 Hz和〜5 Hz的幅度来确定。用于C7-(R)类似物。