For the last 60 or so years the chemotherapy of bacterial infections has been dominated by natural products and their semi-synthetic variants. Although the term antibiotic was initially used exclusively to describe those anti-bacterials of natural or semi-synthetic origin, it has become broadened in common usage to include antibacterial agents of purely synthetic origin as well. The emphasis of this chapter will be on the discovery of novel prototype structures that represent the different classes of antibiotic . penicillins, cephalosporins, and macrolides a distinct from the multiple generations of improved analogues within a class that have typically followed an initial discovery. In some cases, the prototypical molecule discovered.
