Synthesis of (3 S,4 R,3′ S,4′ R)- and (3 S,4 S,3′ S,4′ S)-Crustaxanthins and Further Compounds with 3,4-Dihydroxy β-End-groups Starting from 3, the enantiomerically pure title compounds were synthesized in eight steps. Spectra and HPLC systems are presented that allow a distinction between these isomers.