Recent advances in avermectin research
In 1976 scientists at Merck & Co. Inc. discovered a complex of eight closely re1ate.d naturar roducts subsequently named avertpectins in a culture 6f -m ces i rmi ilis MA-468b (NRd8165 on inating from an isolate by the Kitasato In?zpr:m a klesadp e collected at Kawana. do dtv. Shizuoka Prefecture. JaDaIl. Thev are ado& the mo:t Doteft ... ~~.. anthelmintic, insectibidal an8 acaricidal compounds kndwn. - - The avermectins are closely related to another group of pesticidal natural products, the milbemycins, the first examples described by Japanese workers, but later found to be more abundant in nature than the avermectins. Both the avermectins and milbemycins are sixteen- membered lactones, with a spiroketal system containing two six-membered rings. The princi a1 difference is that the avermectins have an a-L-oleandrosj!-a-L:oleandrosyl disacclaride attached at the 13-position whereas the milbemycins have no 1 substitutent. Two avevectins have been commercialized to date. Selective reduction of the 22,23-olefin of avermectin B yields the 22 23-dihydro derivatiye assigned the non-propnetary name ivermectin. Ibermectin is widelv used as an antiDarasitic drug in animals and in man. Avermectin B is the most effective of the avermictin family 6f natural products a ainst agriculturally hportant insects and mites. It has been commercialized for agriculturi use under the non-proprietary name abamectin. Recent progress in the chemistry of the avermectins has focused on improved insecticidal activity and photostability.