Rel-1,4,7-Tris(1,1-dimethylethyl) Ester 10-[(5R,6S)-6-Hydroxy-2,2-dimethyl-1,3-dioxepan-5-yl]-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic Acid is an intermediate in the synthesis of rel-10-[(1R,2S)-2,3-Dihydroxy-1-(hydroxymethyl)propyl]-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic Acid (D479540), which is an intermediate in the synthesis of Calcobutrol (C145700), a new macrocyclic polyhydroxylated gadolinium chelate derivative which can be used as a contrast agent for Magnetic Resonance Imaging (MRI).