Occasional Survey Choice among Penicillins and Cephalosporins *

In 1944 medical personnel in London was scattered and communications were difficult, but a meeting at the Royal Society of Medicine in November of that year was one of the most crowded ever held there. Such an audience could then have been attracted by only one subject, penicillin, which at that time was proving its worth in the treatment of battle casualties. Of the opening speakers, Fleming is fully reported in the Proceedings, but Florey1 much more briefly, and without reference to a prediction he made-namely, that "some day chemists will manipulate the penicillin molecule to improve its performance." Fulfilment of this prophecy came 15 years later with the isolation of the penicillin nucleus, 6-aminopenicillanic acid. Until then about 30 natural penicillins had been known, whose formation could be induced by adding the appropriate precursor to the culture medium. But the only functioning precursors were derivatives of acetic acid. Removal of the side chain enabled others of quite different nature to be attached and by such means several thousand new penicillins