 The stereocenter opposite the carbanion usually must be tertiary (rather than quaternary) in order to enforce the placement of the largest substituent in the RE position.The asymmetric induction approach relies on stereocenters already set in the starting material that are unaffected by the reaction (chiral auxiliaries).The most success has been achieved by placing these stereocenters either in the G group or in a substituent attached to the terminal end of the double bond.