Pyrethroid Insecticides by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783030556969
Publisher: Springer International Publishing

2 Pyrethroid Structure Configuration

The synthesis of pyrethroids was modelled upon esters (pyrethrins) that constitute approximately 25–50% of pyrethrum, a natural extract of Chrysanthemum spp. flowers used for centuries as insecticide [13]. Among the six isolated esters of pyrethrum responsible for its insecticidal activity, there are two related groups: three esters similar to cyclopropanecarboxylic acid, also named chrysanthemic acid, and three esters related to pyrethric acid [14]. Both acids occur esterified with three alcohols (cinerolone, jasmolone and pyrethrolone), known generically as rethrolones (Fig. 1a). The esterification of the chrysanthemic acid with each rethrolone generates pyrethrins I, while the esterification of pyrethric acid with rethrolones forms pyrethrins II [14].

Fig. 1(a) Chrysanthemic acid, pyrethric acid and basic structure of rethrolones. Chiral carbons (C-1, C-3 and C-4) are presented with their natural configuration; (b) possible spatial configurations of chrysanthemic acid based on chiral carbons (C-1 and C-3) of the cyclopropane ring. Radicals R1 and R2 of the chrysanthemic acid are represented in the dashed frames of (a)

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