The invention relates to a method for preparing (3R, 5S, E)-7-{2-(N-methylsulphonylamino) -4-(4-fluorophenyl)-6-
isopropyl-
pyrimidine-5-yl}-2,2-dimethyl-3,5-dioxane-6-heptenoic acid (compound shown by a formula 4) which is an important intermediate of
Rosuvastatin Calcium in a one-pot way. The method comprises the steps of adding a compound in the formula 1 and a compound in the formula 2 into a
solvent under protection of dried
inert gas, adding a certain amount of strong base at minus 60 DEG C, then slowly increasing temperature to
room temperature, supplementing the strong base after a compound in the formula 3 is completely produced, adding N-methylsulphonylamino, and reacting to produce a compound in the formula 4 at the
room temperature. The method is stable in yield and easy to operate, and provides a method for preparing
Rosuvastatin, and the method has lower cost, is simplified for operation and easy for industrialization. The formula 1, 2, 3, and 4 are shown in the description, wherein R1 is shown in description, and R2 is
alkyl, naphthenic base or benzyl, and preferably methyl, ethyl or
tertiary butyl.