Chapter 21: Q.32P.C (page 1123)
Show how you would use anhydrides to synthesize the following compounds. In each case, explain why an anhydride might be preferable to an acid chloride.
(c) phthalic acid monoamide
Answer
The use of anhydride to synthesize the given compound is given below.
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Propose a mechanism for the formation of 9-hydroxynonanoic acid lactone, as show in the preceding figure.
Show how you would use anhydrides to synthesize the following compounds. In each
case, explain why an anhydride might be preferable to an acid chloride.
(d) succinic acid monomethyl ester
Macrolide antibiotics, including erythromycin and azithromycin (), 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?
(c) Many complex NMR experiments were used to determine the stereochemistry of most, but not all, of the chiral centers. How many chiral centers does the structure contain?
Show how you would synthesize each compound, starting with an ester containing nomore than eight carbon atoms. Any other necessary reagents may be used.
h.
(a)Propose a mechanism for the reaction of benzyl alcohol with acetyl chloride to give benzyl acetate.
(b) Propose a mechanism for the reaction of benzoic acid with acetyl chloride to give acetic benzoic anhydride.
(c)Propose a secondmechanism for the reaction of benzoic acid with acetyl chloride to give acetic benzoic anhydride. This time, let the otheroxygen of benzoic acid serve as the nucleophile to attack the carbonyl group of acetyl chloride. Because proton transfers are fast between these oxygen atoms, it is difficult to differentiate between these two mechanisms experimentally.
(d)Propose a mechanism for the reaction of aniline with acetic anhydride to give acetanilide.
(e)Propose a mechanism for the reaction of aniline with ethyl acetate to give acetanilide. What is the leaving group in your proposed mechanism? Would this be a suitable leaving group for an reaction?
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