作者:Yasuhiko FUTAMURA、Masayuki KUROKAWA、Rika OBATA、Shigeru NISHIYAMA、Takeshi SUGAI
DOI:10.1271/bbb.69.1892
日期:2005.1
A new and efficient route to (S)-azetidine-2-carboxylic acid (>99.9% ee) in five steps and total yield of 48% via malonic ester intermediates was established. As the key step, efficient four-membered ring formation (99%) was achieved from dimethyl (S)-(1'-methyl)benzylaminomalonate by treating with 1,2-dibromoethane (1.5 eq) and cesium carbonate (2 eq) in DMF. Krapcho dealkoxycarbonylation of dimethyl
建立了一条新的有效途径,可分五个步骤制备(S)-氮杂环丁烷-2-羧酸(> 99.9%ee),并通过丙二酸酯中间体的总收率为48%。作为关键步骤,通过在1,2-二溴乙烷(1.5当量)和碳酸铯(2当量)中处理(S)-(1'-甲基)苄基氨基丙二酸二甲酯可实现有效的四元环形成(99%) DMF。(1'S)-1-(1'-甲基)苄基氮杂环丁烷-2,2-二羧酸二甲酯的Krapcho脱氧羰基化反应,是该环化过程的产物,优先形成所需(2S)(2.7:1,总收率78%) (1'S)-单酯,借助于在氮原子上引入的手性助剂。不需要的(2R,1'S)-异构体可以通过去质子化和随后的重质子化步骤以适当的立体化学转化为异构体。最后,