Synthesis of α,α-disubstituted α-amino acid derivatives in enantiopure form via stereoselective addition of Grignard reagents to a chiral acyclic nitrone derived from L-erythrulose

Article abstract of DOI:10.1055/s-2002-25358

The additions of various Grignard reagents to a chiral nitrone prepared from L-erythrulose take place with variable diastereoselectivity. The degree and strength of the facial selectivity can be modified if the reaction is performed in the presence of Lewis acidic additives: zinc bromide enhances attack to the si face whereas diethyl aluminum chloride promotes attack to the re side. The obtained adducts can be then efficiently transformed into protected N-hydroxy α,α-disubstituted α-amino acid derivatives as well as into the corresponding α,α-disubstituted α-amino acids.