Preparation of α-amino-carboxylic acid derivatives via diastereoselective reactions of glycine enolate equivalents

Protected glycine analogues tethered to an imidazolidinone auxiliary undergo diastereoselective alkylation and acylation reactions in moderate to good yields (9-91%) with high levels of stereocontrol (generally >95% de). Subsequent alkylation of these derivatives has been demonstrated for the production of non-racemic alpha,alpha -disubstituted amino acid precursors. Diastereoselective aldol reactions are also found to proceed with good yields and excellent stereocontrol (62-84%, 93-95% de). Chiral auxiliary cleavage and hydrogenolysis of these adducts affords the beta -hydroxy-alpha -amino acid derivatives with no observed erosion of optical purity. (C) 2001 Elsevier Science Ltd. All rights reserved.