The ureido-modification of the resin-bound a luteinizing hormone releasing hormone(LHRH) analogue was investigated by CDI-activating method.The amino group at the side chain of LHRH analogue could be transformed into various substituted urea moieties in high yields.However,its terminal amino group was partially converted to a hydantoin structure due to the attack of the N atom of the adjacent amide bond. The ureido-modification of the resin-bound a luteinizing hormone releasing hormone (LHRH) analogue was investigated by CDI-activating method. The amino group at the side chain of LHRH analogue could be transformed into various substituted urea moieties in high yield. However, its terminal amino group was partially converted to a hydantoin structure due to the attack of the N atom of the adjacent amide bond.