Patent Evaluation: Novel Avermectins as Antibiotics

SummaryNovelty: Novel avermectin analogues in which C25 and its substituent are omitted by contracting the 6,6-spiroketal ring into a 6,5-ring are claimed as antibiotics. They may be used as anthelmintic and antiparasitic, acaricidal (ticks and mites) and nematocidal agents and are said to have high activity.Biology: No biological data are provided. Application methods of the compounds are described, including treatment of infestation by helminths, ectoparasites, insects and acarides in man, animals and plants.Chemistry: Ninety-two examples of syntheses of the compounds by standard techniques are given. Characterization is by NMR and MS. An exemplified compound is 4″,5-di-O-t-butyldimethylsilyl-avermectin B2a.Structure: