Avermectins synthetic approaches

Of the numerous synthetic approaches to the southern half of the avermectins published to date only one (by Danishefsky et al.) has led to a successful total synthesis of a naturally occurring avermectin. The feasibility of this approach, which utilizes a Michael-Aldol sequence to establish the ring system, was first demonstrated by Armistead and Danishefsky [109] in the synthesis of model system 19. In their synthesis, chiral aldehyde 14, which is readily available... 

The preparation of avermectins has been carried out by fermentation, microsomal oxidation of early fermentation compounds and by semi-synthetic methods [57,113]. Approaches to synthesize some avermectins such as abamectin [114] and ivermectin [115-117] have also been published. Recently the total synthesis of aver-mectin [118], avermectin A g [119] and the aglycones of avermectin A g and B g [120,121] have been reported. 

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