To a solution of thiazole (2.5 g, 29 mmol) in THF (25 mL) at −78° C. was added n-BuLi (1.6 M in hexane, 19 mL) dropwise. The mixture was stirred for 30 minutes. Then a solution of Boc-Arg(Tos)-N(Me)OMe, from Example 1, (1.7 g, 3.6 mmol) in THF (50 mL) was added to the lithiothiazole mixture at −78° C. The solution was stirred for 2 hours. 1M HCl (30 mL) was added to the reaction mixture and warmed to room temperature. The mixture was extracted with EtOAc (100 mL). The organic layer was washed with sat. NaCl (30 mL), dried over MgSO4, filtered and evaporated. The crude oily residue was purified by flash column chromatography over SiO2 (50% EtOAc in CH2Cl2) to give Boc-Arg(Tos)-thiazole, shown above, (1.5 g, 84% yield) as a powder.
