The availability of 6-aminopenicillanic acid (6-APA)(11) in quantity from fermentation procedures' has made possible the synthesis of many new aid varied penicillins not amenable to production hy direct biosynthetic methods.?~~ In a previous communication4 we have reported a series of new partially synthetic penicillins prepared from 6- aminopenicillanic acid and a-aryloxyalkanoic acids, one of which, potassium a- ...