N-Boc-Phenylalanine (I) was treated with isobutyl chloroformate and N-methylmorpholine, and the resulting mixed anhydride (II) was coupled to 2-aminobenzophenone (III) to yield the corresponding amide (IV). After Boc deprotection of (IV) with HCl in EtOAc, the intermediate aminoketone was cyclized with NaOH to the benzodiazepine (V). Alkylation of (V) with 3-nitrobenzyl bromide (VI) in the presence of t-BuOK in THF gave the (nitrobenzyl)benzodiazepine (VII). The nitro group of (VV) was subsequently reduced with SnCl2 in boiling EtOAc to affford (VIII). Then, the resulting amine (VIII) was treated with N,N'-di-Boc-thiourea (IX) in the presence of HgCl2 to provide the diprotected guanidine (X), which was finally deprotected with trifluoroacetic acid in CH2Cl2.

N-Boc-Phenylalanine (I) was treated with isobutyl chloroformate and N-methylmorpholine, and the resulting mixed anhydride (II) was coupled to 2-aminobenzophenone (III) to yield the corresponding amide (IV). After Boc deprotection of (IV) with HCl in EtOAc, the intermediate aminoketone was cyclized with NaOH to the benzodiazepine (V). This was coupled to p-iodonitrobenzene (VI) in the presence of copper and NaOAc in DMF at 150 C to give the (nitrophenyl)benzodiazepine (VII). The nitro group of (VII) was subsequently reduced with SnCl2 in boiling EtOAc to yield (VIII). Then, the resulting amine (VIII) was treated with N,N'-di-Boc-thiourea (IX) in the presence of HgCl2 to provide the diprotected guanidine (X), which was finally deprotected with trifluoroacetic acid in CH2Cl2.