Synthesis of protected γ-carboxyglutamates and γ-acylglutamates by rearrangement of N,N-diacylglutamates

A new method for gamma-acylation of protected glutamic acids, involving intramolecular rearrangement of an acyl urethane, has been devised to prepare the protected gamma-carboxyglutamates 7, 9 and 11 and the protected 4-acylglutamates 15 and 22 from N,N-bisurethanes or N-acyl-N-urethanes of general structure 1. When the formylurethane 17 was used in the reaction, then the intermediate 18 in the intramolecular rearrangement was obtained.