Use of Ketene Dithioacetal as a Latent Carboxylic Acid in the Macrolactonization Applicable to the Synthesis of Dilactonic Pyrrolizidine Alkaloids
Resource
Journal of Organic Chemistry 61 (4): 1473-1477
Journal
Journal of Organic Chemistry
Journal Volume
61
Journal Issue
4
Pages
1473-1477
Date Issued
1996
Date
1996
Author(s)
Chou, Wen-Chih
Abstract
Acid 5a (or 5b) bearing the ketene dithioacetal moiety functioned as an equivalent of a dicarboxylic acid. Use of the ketene dithioacetal in the formation of 11-membered dilactones is demonstrated. Compound 5a (or 5b) was converted to an acid imidazolide which reacted regioselectively with retronecine at the allylic position. Mild acidic hydrolysis of the ketene dithioacetal moiety led to a thioester, which underwent macrocyclization with the secondary hydroxyl group mediated by silver(I) trifluoroacetate to give derivatives of the pyrrolizidine alkaloids.
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Type
journal article
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