Enantioselective Total Synthesis of the Natural γ-Tocopherol Metabolite (<i>S</i>)-γ-CEHC [(<i>S</i>)-LLU-α]

Abstract

The asymmetric synthesis of the natural gamma-tocopherol metabolite (S)-gamma-CEHC (1) is described in 10 steps and 18.4% overall yield starting from 2,3-dimethylhydroquinone. The key step is a stereoselective TiCl(4)-mediated homochiral sulfoxide-directed allylation of ketal (SS)-3 to efficiently generate the challenging C-2 stereogenic carbon of chroman (SS,S)-2 with the correct absolute configuration.