Novel optically active 5-chloro- or 5-bromo-3-methylpentane derivatives, their preparation and their use as intermediate for the synthesis of the side chain of (R,R,R)- alpha -tocopherol

摘要

Novel optically active compounds of the general formula I <IMAGE> in which Y represents chlorine or bromine and Z represents OH, Cl, Br, I or -OSO2R, in which R denotes -CH3; -C2H5-; -C3H8 or -C4H9, in particular (R)-5-chloro-3-methylpentanol, (R)-5-bromo-3-methylpentanol, (S)-1-bromo-5-chloro-3-methylpentane, (R)-1-bromo-5-chloro-3-methylpentane, their use for the preparation of optically active compounds of the general formula II <IMAGE> in which Y represents Cl or Br, and a process for the preparation of the compounds of the formula I, which is characterised in that the corresponding novel optically active alkyl 5-halo-3-methylpentanoates of the general formula III <IMAGE> in which R represents alkyl having 1 to 4 C atoms, are reduced with lithium aluminium hydride or lithium borohydride to the optically active 5-halo-3-methylpentanol of the formula Ia <IMAGE> and this pentanol is reacted in the presence of bases with p-toluenesulphonyl chloride or halogenated in a manner known per se.