(3R,5S)-6-Chloro-3,5-dihydroxyhexanoic acid tert-butyl ester is a key chiral intermediate in organic synthesis. It is a white to off-white crystalline powder with a molecular formula of C₁₀H₁₉ClO₄. The compound features a tert-butyl ester protecting group and two chiral hydroxyl groups in the (3R,5S) configuration, which are crucial for its primary application. This compound is most notably used in the synthesis of statin drugs, particularly Atorvastatin (Lipitor) and Rosuvastatin (Crestor). It serves as a critical building block for constructing the essential dihydroxy acid side chain of these HMG-CoA reductase inhibitors. The (3R,5S) stereochemistry is vital for the biological activity of the final drug molecule, making this intermediate a cornerstone in the industrial production of these blockbuster cholesterol-lowering medications. Its synthesis and use are well-documented in pharmaceutical process chemistry. Due to its specific and high-value application as a statin side-chain synthon, it is primarily manufactured and supplied for pharmaceutical production rather than as a general-purpose laboratory reagent.