Suramin sodium synthesis

Suramin, a hexasodium salt of [8,8’ carbonyl-bis-[imino-3,1-phenylencarbonylimino(4-methyl-3,1-phenylen)carbonylimino]]-bis-1,3,5-naphthalintrisulfonic acid (37.4.13), can be made by reacting 1-aminonaphthalene-3,6,8-trisulfonic acid with 4-methyl-3-nitrobenzoyl chloride to make a nitrobenzoic derivative (37.4.8). The nitro group in this compound is reduced by activated iron to an amino derivative (37.4.9), which is acylated by m-nitrobenzoylchloride to make a new nitroderivative, m-nitrobenzoyl-(4-methyl-3-aminobenzoyl)-1-aminonaphthalene-3,6,8-trisulfonic acid (37.4.10).
This is once again reduced to the amine (37.4.11) in the same manner. Reacting the resulting product with phosgene makes [8,8′-carbonyl-bis-[imino-3,1-phenylencarbonylimino(4-methyl-3,1-phenylen]-carbonylimino]-bis-1,3,5-naphthalenetrisulfonic acid (37.4.12), which upon being treated with sodium hydroxide gives suramin.