23-nor-23-oxa avermectin analogs are active anthelmintic agents

摘要

Avermectin analogs are prepared where the 23-position ring carbon atom is deleted and replaced by an oxygen atom. The compounds are prepared by opening the outer spiroketal ring to gain access to the 23-position atom, substituting the ring-opened compounds with a substituent containing the oxygen atom in the appropriate position and closing the ring to prepare the desired compounds. The compounds are potent anthelmintic agents and methods and compositions including such 23-nor-23-oxa compounds are also disclosed.