FIELD: organic chemistry, pharmacy. SUBSTANCE: invention relates to derivatives of avermectin and mylbemycin of the general formula (1) 
where dotted lines mean optional bonds independently being R1 and R2 are absent if C22-C23-double bond exists; R1 means H, OH; R2 means H, OH or C1-C8-alkoxy-group; R3 means H or C1-C6-alkyl; R4 means C3-C8-cycloalkyl, alpha-branched C3-C8-alkyl, alkenyl; R5 means methyl; R6 means hydrogen atom or the group of the formulas (2) 
and (3) 
where R7 means OH, C1-C4-alkoxy-, C2-C5-alkanoyloxy-, amino-, N-(C1-C4)-alkylamino-, N-(C1-C5)-alkanoyl-amino-, oxo- or oximino-group optionally substituted with C1-C4-alkyl group; A means the group 
; B means halide, C1-C8-alkyl, C2-C8-alkynyl, phenyl, pyridinyl, C2-C8-alkanoyl, mercapto-, alkylthio-, arylthio-, nitro-, alkoxyalkyl-, aminoalkyl substituted twice with alkyl, phenylseleno-, azido-group or cyclic system up to 5 carbon atoms that can be substituted with C1-C8-hydroxyalkyl. Invention relates to also a pharmaceutical composition showing an antiparasitic activity and a method of synthesis of derivatives of avermectin and mylbemycin of the formula (1). EFFECT: improved method of synthesis, an antiparasitic activity of compounds. 16 cl, 2 tbl, 140 ex
