A compound represented by formula (I), wherein R 1 represents a hydrogen atom, etc., R 2 and R 3 each independently represents a hydrogen atom, optionally oxidized C1-4 alkyl group or optionally protected hydroxyl group, or R 2 and R 3 taken together represent optionally oxidized C2-5 alkylene group, R 4 represents an optionally oxidized C1-6 alkyl group, etc., R 5 represents an optionally oxidized C1-6 alkyl group, etc., R 6 represents an optionally oxidized C1-6 alkyl group, etc., m represents 0 or an integer from 1 to 3, n represents 0 or an integer from 1 to 4, and i represents 0 or an integer from 1 to 7.本發明係一種通式(I)所表示的化合物：(式中，R1表示氫原子等，R2及R3分別獨立表示氫原子、可被氧化之碳數為1~4之烷基或可被保護之羥基，或者R2及R3合併表示可被氧化之碳數為2~5之伸烷基，R4表示可被氧化之碳數為1~6之烷基等，R5表示可被氧化之碳數為1~6之烷基等，R6表示可被氧化之碳數為1~6之烷基等，m表示0或1~3之整數，n表示0或1~4之整數，i表示0或1~7之整數)。
