Asymmetric synthesis of quaternary α-amino acid derivatives and their fluorinated analogues

In this work, we describe the asymmetric synthesis of a series of fluorinated and non-fluorinated quaternary alpha-amino acid derivatives. This methodology involves the diastereoselective addition of chiral 2-p-tolylsulfinyl benzylcarbanions to either imines containing a 2-furyl moiety or trifluoromethyl alpha-imino esters. Synthetic practicality of this method is demonstrated by short (two-steps) and convenient preparation of 2-(trifluoromethyl)indoline-2-carboxylates.