| abstract |
The compounds represented by the following formula (I) are disclosed: Wherein R 1 represents a hydrogen atom or the like; R 2 and R 3 independently represent a hydrogen atom, an optionally oxidized C 1 -C 4 alkyl group or an optionally protected hydroxy group, or alternatively R 2 and R 3 bond together to form an optionally oxidized C 2 -C 5 alkylene group; R 4 represents an optionally oxidized C 1 -C 6 alkyl group and the like; R 5 represents an optionally oxidized C 1 -C 6 alkyl group and the like R 6 represents an optionally oxidized C 1 -C 6 alkyl group or the like; m represents an integer of 0 or 1 to 3; n represents an integer of 0 or 1 to 4; i represents 0 or an integer of 1 to 7; ). |