Chem Basis - Structures - Penicillins 1

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  1. What is this molecule?
    6-aminopenicillinic acid, the penicillin pharmacophore
  2. The 2 methyls off the thiazolidine ring have what significance?
    Essential for activity and are present on all marketed products
  3. The nature of the R group will determine What characteristic?
    Spectrum of activity, Stability against hydrolysis by beta-lactamases, Acid stability, GI absorption, Side effects, DDIs and protein binding
  4. What action is occurring in this picture?
    In vitro hydrolysis of a penicillin by a base
  5.  The rare of this hydrolysis reaction will increase with increasing _________.
  6.  What reaction is occurring in the picture?
    In vitro or in vivo penicillin decomposition by acid
  7.  At what pH must the media be for this reaction to occur?
    < 3
  8. Preventing nucleophilic attack by the side chain acyl O at the lactam carbonyl C will have what effect on the Penicillin molecule?
    Increase acid stability

  9. Is the C3-COOH essential, why or why not?
    Yes, it mimics the glutamate in the bacterial cell wall

  10. In what form does the C3-COOH exist at physiological pH?

  11. If you create an inorganic salt (e.g. sodium or potassium) from the C3-COOH group, would it be water soluble or insoluble?

  12. If you create an organic salt from the C3-COOH group, would it be water soluble or insoluble?

  13.  If you wanted to formulate a penicillin to be administered by IV, how would you alter this molecule?
    Make the C3-COOH an inorganic salt with K or Na

  14. What is this structure?
    Pen G

  15.  Why is this structure acid liable?
    Because there is negligible electronic influence on side-chain acyl carbonyl, so the acyl carbonyl oxygen has good δ- character

  16. Why is Pen G susceptible to penicillinases?
    The benzyl group is not bulky enough to protect the structure from attack

  17. What characteristic of the R group on Pen G promotes activity against G+ organisms?
    Lipophilicity of the Benzyl group

  18. What characteristic of the R group on Pen G prevents activity against G- organisms?
    Lipophilicity of the Benzyl group

  19. The lipophilic nature of the benzyl group on Pen G has what effect on the molecule?
    Promotes activity against G+, prevents activity against G-, promotes protein binding and promote CNS distribution

  20. Why is Pen G not good for systemic infections?
    Lipophilicty of the benzyl group promotes protein binding and reduces percent free drug

  21. What structure of Pen G allows it to be used in the treatment of meningitis caused by strep pneumoniae?
    The lipophilic benzyl group, which allows it to cross the BBB and attack G+ organisms

  22. What aspect of Pen G allows it to cause side effects like nervousness, dizziness and convulsions?
    The lipophilic benzyl group that allows penetration of the BBB

  23. What enhancement of activity occurs when you add substituents on the benzene group of Pen G?
  24.  What is this structure?
  25. What is this structure?
    Thienyl group

  26. What is the R group called on Ticarcillin?
    Thienyl group

  27. How does the Thienyl group on Ticarcillin compare to a benzene?
    More polar than benzene and may be responsible for increased anaerobic activity
  28. What is the name of the R side chain on this molecule?
    Phenoxymethyl group

  29.  What is this R group called?

  30. How does the side chain of Pen V inhibit nucleophilic attack at the lactam carbonyl carbon in acidic medium?
    The O atom on the side chain is negative inducing, which decreases the nucleophilic character of the side chain acyl Oxygen, inhibiting nucleophilic attack
  31.  How can you change this molecule to provide protection against B-lactamase hydrolysis?
    Incorporate the on the side chain into a ring, providing sufficient steric hindrance

  32.  What is the benefit of having an R group of one of these structures on your penicillin?
    Sterically hinders attack by B-lactamases

  33. The ortho substituents on the rings (R1, R2) have what significance?
    Important for maximum beta-lactamase inhibiting activity (increase steric hindrance) AND for oral activity
  34.  What should R1 and R2 be in order for the molecule to have oral activity?
    Electron withdrawing (e.g. Cl)

  35. Cloxacillin has string B-lactamase inhibition and good oral activity, why?
    Isoxazole ring blocks B-lactamases and electron withdrawing Cl group enhances this and adds oral activity

Card Set Information

Chem Basis - Structures - Penicillins 1
2014-01-21 19:54:13
Chem Basis Structures Penicillins
Chem Basis - Structures - Penicillins 1
Chem Basis - Structures - Penicillins 1
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