tert-Butyl rosuvastatin , its cas register number is 355806-00-7. It also can be called tert-Butyl (6E)-7-[4-(4-fluorophenyl)-6-isopropyl-2-[methyl(methylsulfonyl)amino]pyrimidin-5-yl]-(3R,5S)-3,5-dihydroxyhept-6-enoate ; (3R,5S,6E)-7-[4-(4-Fluorophenyl)-6-isopropyl-2-[(methanesulfonyl)methylamino]pyrimidin-5-yl]-3,5-dihydroxyhept-6-enoic acid tert-butyl ester .It is a white to off-white crystal powder.