(S)-2-(dibenzylamino)-3-phenylpropanal as a chiral auxiliary:: a new strategy for the asymmetric synthesis of 2-substituted alcohols

The high levels of 1,2-stereocontrol observed in nucleophilic additions to (S)-2-(dibenzylamino)-3-phenylpropanal (available in three high-yielding steps from L-phenylalanine) can be converted to remote 1,4-stereocontrol by a stereospecific rearrangement if the nucleophile is a vinyl anion equivalent. Ozonolysis of the product followed by reductive work-up returns an enantiomerically pure 2-substituted alcohol, along with the (S)-2-(dibenzylamino)-3-phenylpropan-1-ol precursor to the starting aldehyde, which functions as a chiral auxiliary. The sequence provides a new strategy for the use of aldehydes as chiral auxiliaries in the synthesis of chiral alcohols bearing oxygen-or carbon-based 2-substituents. (C) 1998 Elsevier Science Ltd. All rights reserved.