作者:Dieter Seebach、Reto Naef、Giorgio Calderari
DOI:10.1016/s0040-4020(01)82417-0
日期:1984.1
α-Hydroxy- and α-mercapto-carboxylic acids are condensed with pivalaldehyde to give 2-t-butyl-5-substituted-l,3-dioxolanones or 1,3-oxathiolanones (2); the predominate CK-isomers are separated by crystallization. The cis-disubstituted heterocycles 2 derived from lactic, mandelic and malic acid furnish, after deprotonation with LDA, reaction with electrophiles such as alkyl halides, aldehydes and ketones
将α-羟基和α-巯基羧酸与新戊醛缩合,生成2-叔丁基-5-取代的-1,3-二氧戊环酮或1,3-氧杂硫杂环戊酮(2);主要的CK异构体通过结晶分离。的顺式二取代的杂环2从乳酸,扁桃酸和苹果酸配料衍生,用LDA,与亲电子试剂如烷基卤化物,醛和酮,去质子化反应后,水解α-α支链羟基-羧酸(3,6,8,9,10)。这些归因于质子在α-CO位置上的整体置换而保留了构型。旋光羧酸是α-烷基化的,没有消旋作用,也没有使用手性助剂(“手性的自我复制”方案I)。非对映选择性(ds)通常> 95%(表1、2和20-25)。