(+/-)-9-bromo-5-[p-(2,3-di-tert-butoxycarbonylguanidinomethyl)-o-(methoxycarbonylmethyl)phenylcarbamoylmethyl]-6,7-dihydro-1H, 5H-pyrido[1,2,3-de]quinoxaline-2,3-dione 以90%的产率得到(+/-)-9-bromo-5-[p-guanidinomethyl-o-(carboxymethyl)phenylcarbamoylmethyl]-6,7-dihydro-1H, 5H-pyrido[1,2,3-de]quinoxaline-2,3-dione