New syntheses of optically active vitamin E side chain by chemicoenzymatic approach

Two independent syntheses of enantiomerically pure ( 3R, 7R) -3,7,11-tri-methyldodecan-1-ol (), the C15 tocopherol side chain, are described. Both reaction sequences start from (R)-citrohellol, obtained by baker's yeast reduction of geraniol. One strategy is based on the coupling between (R)-citronellyl bromide and a C5 optically active unit derived from chemical degradation of the common starting template; the other one uses an achiral isoprenic unit and a C10, building block containing two asymmetric carbon atoms generated by microbial reactions.