Avermectin derivatives

A compound represented by the general formula (I) or a salt thereof:

• 20
• wherein, —XY— represents —CH═CH—, —CH2—C(═O)—, —CH2—CH2—, —CH2—CH(R13)— (wherein R13 represents a hydroxyl group or a lower alkylcarbonyloxy group) or —CH2—C(═N—OR13c)— (wherein R13c represents a hydrogen atom or a lower alkyl group), between R2 and the carbon atom at 5-position represents a single bond or a double bond,
• R1 represents a substituted or unsubstituted lower alkyl group, a formyl group, a carboxyl group, a lower alkoxycarbonyl group (wherein a lower alkyl moiety of said lower alkoxycarbonyl group may be substituted with a heterocyclic group), —CH═N—OR4 (wherein R4 represents a hydrogen atom or a lower alkyl group), a lower alkenyloxycarbonyl group, —CH═N—NH—CONH2, a cyano group, —COR5 (wherein R5 represents an arylalkyloxy group (wherein the aryl group may contain one or more hetero atoms as ring-constituting atoms) or —NR6R7 (wherein R6 and R7 are combined together with the adjacent nitrogen atom to form a nitrogen-containing heterocyclic group), a vinyl group substituted with a lower alkenyloxycarbonyl group, —CO—S—CH2—CH2—NH—CO—Rx (wherein Rx represents a lower alkyl group), —CH═CH—COOH, or a substituted or unsubstituted aryl group, and R1a represents a hydrogen atom, provided that when R1 represents a lower alkoxycarbonyl group (wherein a lower alkyl moiety of said lower alkoxycarbonyl group may be substituted with a heterocyclic group) or a carboxyl group, R1a may further represents a lower alkoxycarbonyl group (wherein a lower alkyl moiety of said lower alkoxycarbonyl group may be substituted with a heterocyclic group), a carboxyl group, a cyano group, or an aryl group,
• and provided that when —XY— is —CH2—C(═O), —CH2—CH2—, or —CH2—CH(R13d)— (wherein R13d represents a lower alkylcarbonyloxy group), a substituent at the 4″-position may be a hydroxyl group instead of OCHR1R1a,
• when between R2 and the carbon atom at 5-position is a single bond, R2 represents a hydroxyl group, a lower alkoxyl group, or a tri(lower alkyl)silyloxy group, and when between R2 and the carbon atom at the 5-position is a double bound, R2 is combined with the carbon atom at 5-position to form a carbonyl group or a hydroxime group (—C(═NOH)), and
• R3 represents a hydroxyl group or a tri(lower alkyl)silyloxy group.