Synthesis and determination of the enantiomeric purity of (R)‐ and (S)‐2,3‐Dihydroxy‐3‐methylbutyl p‐Toluensulfonate

Abstract (R)‐ and (S)‐2,3‐dihydroxy‐3‐methylbutyl p‐toluenesulfonate, used as building blocks for vitamine D 3 metabolites and carotenoids, respectively, were resynthesized since differing melting points and optical rotations are reported in the literature. The given data of the (S)‐enantiomer could be corrected. A method for the determination of the enantiomeric purity was elaborated using the influence of a chiral lanthanide shift reagent on the 1 H‐n.m.r. spectra of these compounds. By this way it was shown that both compounds exhibit an enantiomeric excess of more than 94%. The (S)‐enantiomer was synthesized according to an improved synthetic scheme starting from L‐serine.