Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

22. Carboxylic Acid Derivatives: NAS

Lactones, Lactams and Cyclization Reactions

Organic Chemistry

22. Carboxylic Acid Derivatives: NAS

Lactones, Lactams and Cyclization Reactions

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5:54 minutes

Problem 71a,b

Textbook Question

Macrolide antibiotics, including erythromycin and azithromycin (Zithromax®), contain a large ring lactone. One of the largest ever reported is Gargantulide A, the structure of which was determined by the research group of Prof. William Gerwick of the Scripps Institution of Oceanography (Organic Letters, 2015, 17, 1377–1380). Isolated from a Streptomyces bacterium, it kills pathogenic bacteria like MRSA and Clostridium difficile, but it proved too toxic to the test animals to continue further testing.
(a) Identify the lactone that makes this a macrolide structure.
(b) How many rings does this structure contain? How many atoms are in the largest ring?

Verified step by step guidance

Examine the structure of Gargantulide A provided in the image. A lactone is a cyclic ester, which contains a carbonyl group (C=O) bonded to an oxygen atom within a ring structure. Identify the lactone group in the molecule by locating the ester functional group within a ring.

The term 'macrolide' refers to a large ring lactone. In Gargantulide A, the largest ring containing a lactone group is the macrolide structure. Locate the largest ring in the molecule that contains the lactone functional group.

Count the number of rings present in the structure. Look for all cyclic structures, including the macrolide ring and any other smaller rings present in the molecule.

Determine the number of atoms in the largest ring. To do this, count all the atoms (carbon, oxygen, etc.) that form the perimeter of the macrolide ring.

Summarize the findings: Identify the lactone group that makes this a macrolide structure, state the total number of rings in the molecule, and specify the number of atoms in the largest ring.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Macrolide Structure

Macrolides are a class of antibiotics characterized by a large lactone ring, typically containing 14 to 16 atoms. The lactone is formed through the esterification of a hydroxy acid, which is crucial for the antibiotic's mechanism of action. Understanding the structure of macrolides, including the specific lactone present in Gargantulide A, is essential for identifying its properties and functions.

Ring Structure in Organic Chemistry

In organic chemistry, the term 'ring structure' refers to a cyclic arrangement of atoms within a molecule. The number of rings and their sizes can significantly influence the chemical properties and biological activity of a compound. For Gargantulide A, determining the number of rings and the size of the largest ring is vital for understanding its structural complexity and potential interactions with biological targets.

Antibiotic Mechanism of Action

Antibiotics like macrolides function by inhibiting bacterial growth through various mechanisms, such as blocking protein synthesis. Understanding how Gargantulide A interacts with bacterial cells, particularly its effectiveness against pathogens like MRSA, is crucial for evaluating its potential therapeutic applications. However, the toxicity observed in test animals highlights the importance of balancing efficacy with safety in drug development.

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