A process for the preparation of substantially pure calcium bis-(E)-3,5-dihydroxy-7-[4’-(4’’-flurophenyl)-2’- cyclopropyl-quinoline-3-yl]-hept-6-enoate 1, pitavastatin calcium a HMG-CoA reductase inhibitor is described. The prior methods reported for the said conversion involves use of large amount of organic solvents. The new procedure reported here involves use of only water as solvent. The operational simplicity, high yield, eco-friendly conditions and easily scalable process are major benefits.