The present invention relates to a chemical process for HMG-CoA reductase inhibitors and intermediates thereof. Particularly, the present invention relates to an improved process for synthesizing calcium salt of (E)-7-[4-(4-flurophenyl)-6-isopropyl-2-[methyl(methylsulfonyl)amino] pyrimidin-5-yl](3R,5S)-3,5-dihydroxy-6-heptenoic acid (Rosuvastatin Calcium) in high purity.