22,23-Dihydroavermectin from avermectin

Avermectins and Ivermectin. The avermectins are pentacydic lactones isolated from fermentation products of Streptomyces avermitilisy and ivermectin is a semisynthetic chemical, 22,23-dihydroavermectin B1 (46). Ivermectin is effective in very low doses for the control of red spider mites on deciduous fruits, in baits for the control of imported fire ants, and as a parasiticide for Onchocerca volvulus in humans and for catde grubs. These insecticides appear to function as agonists for the neuroinhibitory transmitter y-aminobutyric acid (GABA) (see Antiparasitic agents, avermectins). 

These 3-dimensional structures are shown in Figure 4. The top panel shows avermectin Bia and 22, 23 dihydroavermectin Bia, from which we can see some general features of abamectin and ivermectin that are not obvious from the 2-dimensional representation. These include the rigid, corrugated planar form of... 

Extracted from the soil actinomycete Streptomyces avermitilis, the natural avermectins are 16-membered macrocyclic lactones that, on reduction of the C22-23 double bond, give rise to ivermectin (IVM), which is an 80 20 mixture of dihydroavermectin Bia and Bip, respectively. The natural avermectins have minimal biological activity, but IVM has proven to be quite beneficial in the treatment of various nematode infections. 

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