A 2-azetidinone of formula (I): ##STR1## wherein R.sub.1 represents an aralkoxy, acyloxy, sulphonyloxy or amino group any of which may be substituted, or hydrogen, hydroxy, alkoxy or azido; R.sub.2 represents an alkyl or aralkyl group either of which may be substituted, or hydrogen; R.sub.3 represents an alkyl, aryl, aralkyl, alkenyl, aralkenyl, alkynyl, aralkynyl, acyl or heterocyclic group any of groups may be substituted; and R.sub.4 represents an alkyl, alkenyl, aryl or aralkyl group any of which may be substituted; or formula (I'): ##STR2## wherein R.sub.1 ' is the same as R.sub.1 above; R.sub.2 ' represents an alkyl, aralkyl or trialkylsilyl group any of which may be substituted, or hydrogen; R.sub.3 ' is the same as R.sub.3 above; and R.sub.4 ' represents an alkyl, aralkyl or trialkylsilyl group any of which may be substituted, or hydrogen; provided that when R.sub.1 ' represents azido or optionally substituted amino, R.sub.2 ' represents hydrogen or CH.sub.2 CCl.sub.3 and R.sub.4 ' represents ##STR3## R.sub.3 ' represents other than ##STR4## or a pharmaceutically acceptable salt thereof is disclosed. The derivatives exhibit .beta.-lactamase inhibiting activity and are thus of interest as anti-bacterial agents, used alone or together with known antibiotic subtances.
                            式(I)的2-
吖啶酮:其中R.sub.1代表芳基氧基、酰氧基、磺酰氧基或
氨基,其中任一可以被取代,或氢、羟基、烷氧基或
叠氮基;R.sub.2代表烷基或芳基烷基,其中任一可以被取代,或氢;R.sub.3代表烷基、芳基、芳基烷基、烯基、芳基烯基、炔基、芳基炔基、酰基或杂环基,其中任一可以被取代;R.sub.4代表烷基、烯基、芳基或芳基烷基,其中任一可以被取代;或式(I'):其中R.sub.1'与上述的R.sub.1相同;R.sub.2'代表烷基、芳基烷基或三烷基
硅基,其中任一可以被取代,或氢;R.sub.3'与上述的R.sub.3相同;R.sub.4'代表烷基、芳基烷基或三烷基
硅基,其中任一可以被取代,或氢;但是当R.sub.1'代表
叠氮基或可选择取代的
氨基时,R.sub.2'代表氢或CH.sub.2 CCl.sub.3,R.sub.4'代表R.sub.3'代表除了##STR4##或其药学上可接受的盐。这些衍
生物表现出β-内酰胺酶抑制活性,因此作为抗菌剂很有兴趣,可以单独使用或与已知抗生素物质一起使用。