Antimicrobial activity is exhibited by .beta.-lactams having a ##STR1## substituent in the 1-position and an acylamino substituent in the 3-position, or a pharmaceutically acceptable salt thereof; wherein Y is oxygen or sulfur and R.sub.5 is hydroxyl, alkyl, substituted alkyl, phenyl, substituted phenyl, alkoxy, alkylthio, (substituted alkyl)oxy, (substituted alkyl)thio, phenyloxy, phenylthio, (substituted phenyl)oxy or (substituted phenyl)thio.
具有##STR1##取代基于1-位置和酰胺取代基于3-位置的β-内
酰胺类化合物或其药用可接受盐表现出抗微
生物活性;其中Y为氧或
硫,R.sub.5为羟基、烷基、取代烷基、苯基、取代苯基、烷氧基、烷
硫基、(取代烷基)氧基、(取代烷基)
硫基、苯氧基、苯
硫基、(取代苯基)氧基或(取代苯基)
硫基。