The present invention relates to an improved process for the manufacture of (3S)-3,4-trans-disubstituted azetidinones of the formula ##STR1## in which R.sub.1 represents hydrogen or lower alkyl, R.sub.2 represents hydrogen or a hydroxy-protecting group, Y represents the group --S(.dbd.O)--R.sub.3 or --S(.dbd.O).sub.2 --R.sub.3 wherein R.sub.3 represents an organic radical bonded to the sulphur atom by a carbon atom that is not bonded to hydrogen, or the group --C(.dbd.O)--O--R.sub.3 ' wherein R.sub.3 ' represents an organic radical bonded to the oxygen atom of the carboxy group by a carbon atom that is not bonded to hydrogen, or a carboxy-protecting group, and R.sub.4 represents hydrogen or an amino-protecting group R.sub.4 '. The process according to the invention is carried out under particularly favorable reaction conditions and yields compounds (I) in particularly high yields.
本发明涉及一种改进的制备式为##STR1##的(3S)-3,4-顺反取代的氮杂环丙
酮类化合物的方法,其中R.sub.1表示氢或低碳基,R.sub.2表示氢或羟基保护基,Y表示--S(.dbd.O)--R.sub.3或--S(.dbd.O).sub.2--R.sub.3,其中R.sub.3表示有机基团,通过未与氢键合的碳原子与
硫原子相结合,或者表示--C(.dbd.O)--O--R.sub.3 ',其中R.sub.3 '表示通过未与氢键合的碳原子与羧基氧原子相结合的有机基团或羧基保护基,R.sub.4表示氢或
氨基保护基R.sub.4'。根据本发明的方法在特别有利的反应条件下进行,产率特别高。