The preparation and the reaction of enantiomerically pure (R) – and (S)-5-trimethylsilyl-2-cyclohexenone are described. The enones can undergo diastereospecific alkylation or conjugate addition leading to the corresponding substituted cyclohexe (a) nones with a newly created tertiary or quaternary chiral center. The synthesis of some optically active natural products utilizing the enantiomerically pure enones are also described. © 1990, The Society of Synthetic Organic Chemistry, Japan. All rights reserved.