Lk6 derivatives-a.

A LK6-A derivative represented by the formula ** ** [wherein R1 represents C1-C9 (C9-C1 alkyl may be substituted by one to a substitutable number of substituents which are the same or different and are selected from the group a) alkanoyl C2-C10 (alkyl moiety of the alkanoyl C2-C10 may be substituted by one to a substitutable number of substituents which are the same or different and are selected from the group a), carboxy, (C2-C10) - carbonyl, (wherein n represents 1 or 2) or COCH = CHR 9 {wherein R9 represents C1-C9 optionally substituted by one to a substitutable number of substituents which are the same or different and are selected from group B, C6-C14 aryl optionally substituted with 1 to 3 substituents which are the same or different and are selected from the group C, 5- or 6-membered optionally substituted with 1 to 3 substituents which are equal are different and are selected from the group C or NR10R11 (wherein R10 and R11, which may be the same or different, represents n each hydrogen, C1-C9 optionally substituted by one to a substitutable number of substituents which are the same or different and are selected from the group B, C2-C6 alkyl optionally substituted by one to a different number of substituents which are the same or .