Ketal Formation in Macrolides: Chemistry Quiz
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Questions and Answers

What is the role of an acid catalyst in the chemical modification of erythromycin?

  • Deactivating the hydroxyl group to prevent a nucleophilic attack
  • Activating the hydroxyl group for a nucleophilic attack (correct)
  • Inhibiting the formation of a ketal linkage
  • Breaking down the erythromycin structure

    • What type of linkage is formed as a result of intramolecular nucleophilic attack in erythromycin?

  • Cyclic ketal linkage (correct)
  • Phosphodiester bond
  • Disulfide bond
  • Ester bond

    • How is the acid catalyst typically treated after its role in the chemical modification process with erythromycin?

  • Regenerated for further use (correct)
  • Disposed as waste
  • Stored for future experiments
  • Neutralized with a base

    • Which specific hydroxyl group in erythromycin is often selective for ketal formation?

    <p>C9 hydroxyl group</p> Signup and view all the answers

    How does bacterial resistance to erythromycin and lincomycins occur?

    <p>By methylation of a specific adenine residue at the ribosomal subunit</p> Signup and view all the answers

    Which characteristic of erythromycin is affected when the enzyme is produced by resistant strains?

    <p>Its binding to ribosomal RNA</p> Signup and view all the answers

    Which chemical modification of erythromycin is associated with a pKa value around 7.5?

    <p>The conjugated phenolic enone system extending from C-10 to C-12</p> Signup and view all the answers

    How do tetracyclines interfere with protein biosynthesis at the ribosomal level?

    <p>By inhibiting subsequent rRNA binding to the ribosomes</p> Signup and view all the answers

    What is the main resistance mechanism of Gram-negative bacilli against macrolides like Erythromycin?

    <p>Increased permeability of the bacterial cell wall.</p> Signup and view all the answers

    What is an alternative medical use of Erythromycin besides treating soft tissue infections?

    <p>Alternative for treating infections in patients allergic to penicillins.</p> Signup and view all the answers

    Which chemical group is esterified at the keto group site in Erythromycin?

    <p>Desosamine</p> Signup and view all the answers

    What is the major route of excretion for Erythromycin?

    <p>Bile</p> Signup and view all the answers

    Which modification is made to increase lipid solubility and acid stability of Erythromycin for improved oral absorption?

    <p>Removal of 9-keto group</p> Signup and view all the answers

    What feature distinguishes Azithromycin from other macrolides like Erythromycin?

    <p>15-membered lactone ring</p> Signup and view all the answers

    Why do Enterobacteriaceae family bacteria show pH-dependent sensitivities to Erythromycin?

    <p>MIC's decrease with increasing pH.</p> Signup and view all the answers

    What aspect was modified in Azithromycin to increase its stability to acid-catalyzed degradation?

    <p>Incorporation of tertiary amine nitrogen into the macrolide ring</p> Signup and view all the answers

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