| abstract |
Antiparasitic avermectin and milbemycin derivatives of formula (I) wherein the broken lines represent independently optional bonds, R<1> and R<2> being absent when the C22-C23 double bond is present, R<1>, R<2>, R<6> are independently H, OH, halo, oximino or an organic radical, R<4> and R<5> organic radicals, R<3> is H or an organic radical, and A and B may be a wide variety of substituents, are prepared by reacting a compound of formula (I) in which A is an optionally substituted hydrazone group with an electrophilic species to effect substitution at the 3-position, followed by further synthetic steps if necessary. |