Mylbemycin derivatives with antiparasitic activity.

摘要

Compounds of the formula: wherein either R<1> is hydrogen and R<1> is hydroxy or R and R are taken together and are oxo; R<2> is a C3-C8 straight or branched-chain alkyl, alkenyl or alkynyl group which may optionally contain an oxygen or sulphur atom as part of the chain, or a C3-C8 cycloalkyl or cycloalkenyl group, or a 3 to 6 membered oxygen or sulphur containing heterocyclic ring which may be saturated or fully or partially unsaturated and which may optionally be substituted by one or more C1-C4 alkyl groups or halogen atoms; R<3> is methyl or ethyl; R<4> is hydrogen or methyl; either R<5> is hydrogen or hydroxy and R<6> is methyl or hydroxymethyl, or the two groups R<5> and R<6> are taken together and are -O-CH2-; R<7> is hydrogen, methyl or ethyl; and R<8> is hydrogen or halogen; with the proviso that when R<2> is branched chain alkyl it is not isopropyl, are antiparasitic agents having utility as anthelmintics, ectoparasiticides, insecticides and acaricides.