A novel chiral indanol 11 is conveniently synthesized by using a stepwise displacement of the methoxy groups of 2,6-dimethoxybenzoic ester 1 by a vinyl and then an aryl Grignard reagent as the key step. The racemic indanol 11 is optically resolved as the diastereomeric (Sa)-2′-methoxy-1,1′-binaphthyl-2-carboxylic esters 12 by column chromatography. The absolute stereochemistry of the indanol (+)-11 is established to be S by an X-ray crystallographic analysis of the ester (Sa,S)-12. Performance of the indanol 11 as a chiral auxiliary, and as a protective group for the carboxy function, is examined in the atrolactic
acid synthesis from phenylglyoxylic ester 13 and methylmagnesium iodide and in the biphenyl coupling reaction of 2,3-dimethoxybenzoic ester 15 with 2-methoxy-4,6-dimethylphenylmagnesium bromide, resulting in quantitative formations of atrolactic ester 14 with up to 83% de and biphenyl 16 with 72% de, respectively.
一种新颖的手性
吲哚醇11通过逐步置换
2,6-二甲氧基苯甲酸酯1中的甲氧基,首先使用
苯乙烯Grignard试剂,然后使用芳基Grignard试剂方便地合成。 Racemic
吲哚醇11通过柱色谱被光学分离为二态异构体(Sa)-2'-甲氧基-1,1'-
萘基-2-
羧酸酯12。通过对酯(Sa,S)-12进行X射线晶体学分析,确定了
吲哚醇(+)-11的绝对构型为S。
吲哚醇11作为手性辅助试剂及羧基的保护基团的性能在从苯乙酰酸酯13和
碘化甲基
镁反应合成阿托拉酸中,以及在
2,3-二甲氧基苯甲酸酯15与2-甲氧基-4,6-二甲基苯
镁溴化物的
联苯偶联反应中被检验,结果分别得到在83%对映体过量(de)的阿托拉酸酯14和在72%对映体过量的
联苯16的定量生成。