Aldol condensation of the magnesium enolate derived from anhydro-6,6-dibromopenicillin with acetaldehyde allows for the stereospecific introduction of a 1-R-hydroxyethyl substituent at C-6. Protection of the hydroxy group followed by reductive dehalogenation provides anhydro-6(α)-[(1-R)-(tert;-butyldimethylsilyloxy)-ethyl]-penicillin, an intermediate in the synthesis of thienamycin. A high yield conversion of this anhydro derivative to (4-R)-acetoxy-(3-S)-[(1-R)-(tert-butyldimethylsilyloxy-ethyl]-azetidin-2-one (5) is also reported.
镁烯醇酸盐与
乙醛的Aldol缩合反应,使得从无
水6,6-二
溴青霉素得到的
镁烯醇酸盐在C-6位置特异性引入1-R-羟乙基取代基。羟基的保护后进行还原去卤反应,得到无
水6(α)-[(1-R)-(tert;-butyldimethylsilyloxy)-ethyl]-
青霉素,这是合成噻
氨霉素的中间体。报道了将这种无
水衍
生物高产率转化为(4-R)-乙酰氧基-(3-S)-[(1-R)-(tert-butyldimethylsilyloxy-ethyl]-
氮杂环丙烷-2-酮 (5) 的方法。