1. 1 © Patrick An Introduction to Medicinal Chemistry 3/e Chapter 16 ANTIBACTERIAL AGENTS Part 3: Other lactams

2. 1 © Newer b-Lactam Antibiotics Thienamycin (Merck 1976)(from Streptomyces cattleya) Potent and wide range of activity vs Gram +ve and Gram -ve bacteriaPotent and wide range of activity vs Gram +ve and Gram -ve bacteria Active vs. Pseudomonas aeruginosaActive vs. Pseudomonas aeruginosa Low toxicityLow toxicity High resistance to  -lactamasesHigh resistance to  -lactamases Poor stability in solution (ten times less stable than Pen G)Poor stability in solution (ten times less stable than Pen G)

3. 1 © Newer b-Lactam Antibiotics Thienamycin analogues used in the clinic Imipenem Ertapenem(2002) Meropenem

4. 1 © Newer b-Lactam Antibiotics Nocardicins (Fujisawa 1975) Monocyclic  -lactam ring - monobactamsMonocyclic  -lactam ring - monobactams Moderately active in vitro vs narrow group of Gram -ve bacteriaModerately active in vitro vs narrow group of Gram -ve bacteria Active vs. Pseusomonas aeruginosaActive vs. Pseusomonas aeruginosa Inactive vs. Gram +ve bacteriaInactive vs. Gram +ve bacteria Different spectrum of activity from penicillinsDifferent spectrum of activity from penicillins Thought to operate by a different mechanism from penicillinsThought to operate by a different mechanism from penicillins Low toxicityLow toxicity Nocardicin A

5. 1 © Newer b-Lactam Antibiotics Clinically useful monobactam Administered by intravenous injectionAdministered by intravenous injection Can be used for patients with allergies to penicillinsCan be used for patients with allergies to penicillins and cephalosporins No activity vs. Gram +ve or anaerobic bacteriaNo activity vs. Gram +ve or anaerobic bacteria Active vs. Gram -ve aerobic bacteriaActive vs. Gram -ve aerobic bacteria Aztreonam

6. 1 © b-Lactamase Inhibitors Clavulanic acid (Beechams 1976)(from Streptomyces clavuligerus) Weak, unimportant antibacterial activityWeak, unimportant antibacterial activity Powerful irreversible inhibitor of  -lactamases - suicide substratePowerful irreversible inhibitor of  -lactamases - suicide substrate Used as a sentry drug for ampicillinUsed as a sentry drug for ampicillin Augmentin = ampicillin + clavulanic acidAugmentin = ampicillin + clavulanic acid Allows less ampicillin per dose and an increased activity spectrumAllows less ampicillin per dose and an increased activity spectrum Timentin = ticarcillin + clavulanic acidTimentin = ticarcillin + clavulanic acid

7. 1 © 2 NH 2 Clavulanic acid - mechanism of action OH NH 2 1 543 b-Lactamase Inhibitors

8. 1 © Penicillanic acid sulfone derivatives Suicide substrates for  -lactamase enzymesSuicide substrates for  -lactamase enzymes Sulbactam has a broader spectrum of activity vs  -lactamases than clavulanic acid, but is less potentSulbactam has a broader spectrum of activity vs  -lactamases than clavulanic acid, but is less potent Unasyn = ampicillin + sulbactamUnasyn = ampicillin + sulbactam Tazobactam has a broader spectrum of activity vs  -lactamases than clavulanic acid, and has similar potencyTazobactam has a broader spectrum of activity vs  -lactamases than clavulanic acid, and has similar potency Tazocin or Zosyn = piperacillin + tazobactamTazocin or Zosyn = piperacillin + tazobactam b-Lactamase Inhibitors SulbactamTazobactam