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 D3 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 1H‐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.