Phosphine-Directed Diastereoselective Allylic Substitutions

Significance

The authors report a solution to the challenge of creating a new stereogenic center next to a pre-existing one by a simple strategy. A ‘directing leaving group’ delivers the external nucleophile exclusively at the most hindered position, and the diastereoselectivity is controlled by the geometry of the alkene. Most of the current methods to prepare β-branched amino acids are based on intramolecular rearrangements. The application of the method was demonstrated in the synthesis of the natural amino acid 8.