Antide acetate was prepared as follows: the peptide intermediate was first treated with a suitable thiol to remove the Nps protecting group. It was then reacted with 2-benzyl-4-carboxypyridine in DMF in DCC as a coupling agent to acylate the Orn residue at the 5-position. After washing, the peptide resin was treated with piperidine to remove the Fmoc protecting group, followed by treatment with nicotinic acid and DIIC to acylate the D-Lys residue at the 6-position. Following cleavage and HPLC purification, the GnRH antagonist was tested and the peptide was considered effective in preventing ovulation in low-dose female mammals.
