Synthesis of new steroidal derivatives by the reaction of steroid-amino acid conjugates with N,N′-dicyclohexyl-carbodiimide. Unusual formation of steroidal imide derivatives

Several new steroid derivatives have been synthesised by the reaction of steroid-amino acid conjugates with N,N′-dicyclohexyl-carbodiimide. Selectivity of the reaction was found to depend greatly on the properties of the amino acid moiety. While the reaction of the glycine derivative led to the corresponding 5(4H)-oxazolone, an unusual imide formation together with an N-acylurea side product was observed in the case of conjugates of l-alanine, l-phenylalanine and l-methionine. The structures of the new products, steroidal imide and N-acylurea derivatives, were determined by various spectroscopic methods.