Coupling of N-Boc-O-benzyltyrosine (I) with 4-fluoro-1,2-phenylenediamine (II) by means of EDC afforded amide (III), which was converted into thioamide (IV) upon treatment with phosphorus pentasulfide and Na2CO3. Then, ring closure of (IV) with phosgene afforded the benzimidazolone derivative (V).

Coupling of N-Boc-glycine (VI) with glycine benzyl ester hydrochloride (VII) by means of 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ) gave the protected dipeptide (VIII). After deprotection of the Boc group of (VIII) with HCl, the resulting amine (IX) was condensed with the thioacylating compound (V) to furnish thioamide (X). Finally, the Boc and benzyl protecting groups of (X) were cleaved using HF.