Penicillins Common nucleus S、/CH Penicillin G(Requires injection) CH2-C-NH-CH-CH C CH2 O=C—N—CH-COOH 0 S、/CH Penicillin V(Can be taken orally) OCH2-C-NH-CH-CH O-CN CH COOM B-lactam ring (a)Natural(antibiotic)penicillins Common nucleus 0 S、CH Oxacillin C-NH-CH-CH (Resistant to penicillinase) CH3 0=C十N—GHC地ooH B-lactam ring S、CH Ampicillin(Extended spectrum) CH-C-NH-CH-CH CH3 NH2 O=C—N—CH-COOH (b)Semisynthetic penicillins Figure 20.6Penicillins Figure 20.6