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The chrysanthemumcarboxylic acids. III.—Lactonization of the chrysanthemic acids
Author(s) -
Crombie L.,
Harper S. H.,
Thompson R. A.
Publication year - 1951
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740020909
Subject(s) - lactone , chemistry , hydrolysis , ring (chemistry) , organic chemistry , stereochemistry
(±)‐cis‐Chrysanthemic acid is readily lactonized in boiling dilute sulphuric acid to the crystalline (±)‐cis‐dihydrochrysanthemo‐δD‐lactone. The lactone ring is opened by alkali hydrolysis and a derivative of the (±)‐cis‐δD‐hydroxydihydrochrysanthemic acid is obtained. With methanolic sulphuric acid the lactone ring is opened to give mainly methyl (±)‐cis‐±‐methoxydihydrochrysanthemate together with methyl (±)‐cis‐chrysanthemate. In contrast, (±)‐trans‐chrysanthemic acid is converted under similar conditions into the crystalline (±)‐trans‐δ‐hydroxydihydrochrysanthemic acid. The mechanisms of these reactions and their bearing on the Seil and the Wilcoxon–Holaday methods of pyrethrum assay are discussed. On heating at 300° C. in sealed tubes (±)‐cis‐and (±)‐trans‐chrysanthemic acids and (±)‐cis‐dihydrochrysanthemo‐δ‐lactone are converted into an isomeric crystalline lactone, (±)‐pyrocin. This is shown by oxidative degradation not to be a dihydrochrysanthemo‐lactone but to be (±)‐β‐isobutenylisohexano‐σ‐lactone. These lactones are substantially non‐toxic to houseflies.