1-O-[4-[(4-chloro-6-methoxy-1,3,5-triazin-2-yl)amino]phenyl] 5-O-(2-methoxyethyl) 4-bromo-2,2,4-trimethylpentanedioate;1-O-[2-(1,3-dioxoisoindol-2-yl)ethyl] 5-O-(2-methoxyethyl) 4-bromo-2,2,4-trimethylpentanedioate;5-O-(2,5-dioxopyrrolidin-1-yl) 1-O-(2-methoxyethyl) 2-bromo-2,4-dimethylpentanedioate;1-O-(2,5-dioxopyrrolidin-1-yl) 5-O-(2-methoxyethyl) 4-bromo-2,2,4-trimethylpentanedioate;1-O-(2-hydroxyethyl) 5-O-(2-methoxyethyl) 4-bromo-2,2,4-trimethylpentanedioate