Asymmetric synthesis of α-amino acids through α-iodination of chiral unsaturated carboxamides and stereoselective iodolactonization

The α-iodination reaction of chiral enamides 1 possessing (2R,5R)-2,5-bis(methoxymethyl)pyrrolidine as a chiral auxiliary proceeded with high diastereoselectivity in the presence of I₂ and s-collidine. The chiral iodides 2 thus obtained were converted to the α-BocNH-amides 3 without epimerization. The subsequent iodolactonization afforded trans-lactones 4 with a relatively high selectivity.