Patent ID: 7144866

Claim:
A compound represented by the general formula (I) or a salt thereof: wherein, —X Y— represents —CH═CH—, —CH 2 —C(═O)—, —CH 2 —CH 2 —, —CH 2 —CH(R 13 )— (wherein R 13 represents a hydroxyl group or a lower alkylcarbonyloxy group) or —CH 2 —C(═N—CR 13c )— (wherein R 13c represents a hydrogen atom or a lower alkyl group), between R 2 and the carbon atom at 5-position represents a single bond or a double bond, R 1 represents a substituted 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—OR 4 (wherein R 4 represents a hydrogen atom or a lower alkyl group), a lower alkenyloxycarbonyl group, —CH═N—NH—CONH 2 , a cyano group, —COR 5 (wherein R 5 represents an arylalkyloxy group (wherein the aryl group may contain one or more hetero atoms as ring-constituting atoms) or —NR 6 R 7 (wherein R 6 and R 7 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—CH 2 —CH 2 —NH—CO—R x (wherein R x represents a lower alkyl group), —CH═CH—COOH, or a substituted or unsubstituted aryl group, and R 1a represents a hydrogen atom, provided that when R 1 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, R 1a 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 —X Y— is —CH 2 —C(═O), —CH 2 —CH 2 , or —CH 2 —CH(R 13d )—(wherein R 13d represents a lower alkylcarbonyloxy group), a substituent at the 4″-position may be a hydroxyl group instead of OCHR 1 R 1a , when between R 2 and the carbon atom at 5-position is a single bond, R 2 represents a hydroxyl group, a lower alkoxyl group, or a tri(lower alkyl)silyloxy group, and when between R 2 and the carbon atom at the 5-position is a double bound, R 2 is combined with the carbon atom at 5-position to form a carbonyl group or a hydroxime group (—C(═NOH)), and R 3 represents a hydroxyl group or a tri(lower alkyl)silyloxy group.