title: Studies on the biosynthesis of avermectins.
abstract: To elucidate the pathway of avermectin biosynthesis, the biosynthetic relationships of avermectins A1a, A2a, B1a, B2a, and their respective monosaccharides and aglycones were studied. 14C-labeled avermectin compounds prepared from [1-14C]acetate were fed to Streptomyces avermitilis strain MA5502 and their metabolites were determined. Two furan ring-free aglycones, 6,8a-seco-6,8a-deoxy-5-keto avermectin B1a and B2a, have been isolated from the fermentation broth of a blocked mutant of S. avermitilis. Addition of the compounds and a semisynthetic compound, 5-keto avermectin B2a aglycone, to the fermentation medium of a second blocked mutant established that the two compounds are intermediates in the avermectin biosynthetic pathway immediately preceding avermectin aglycones.
authors.affiliation: Department of Fermentation Microbiology, Merck Sharp & Dohme Research Laboratories, Rahway, New Jersey 07065.
authors.forename: T S
authors.initials: TS
authors.lastname: Chen
authors.forename: E S
authors.initials: ES
authors.lastname: Inamine
mesh_terms: D000085:Acetates / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005285:Fermentation; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000235:genetics; D009154:Mutation; D013302:Streptomyces / Q000235:genetics / Q000378:metabolism*
chemical_list: D000085:Acetates; D007559:Ivermectin; C019264:avermectin