The compound according to claim 1, wherein R1 is a phenyl group which is unsubstituted or substituted with one or more groups selected from the group consisting of a Substituent group ??1 and a Substituent group ??1, the Substituent group ??1 is selected from the group consisting of a hydroxyl group, a cyano group, a halogen atom, a lower alkoxy group and a halogeno lower alkoxy group; and the Sub