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With sodium hydroxide; In 1,4-dioxane; water; at 0 - 20℃; for 3.5h;
A solution of (Boc) 20 (800 mg, 3.5 mmol) in 1,4-dioxane (5 ML) was added to a cold (0 C) solution OF DI-L-PHE-PHE (1 g, 3.20 mmol) in 1,4-dioxane (6 mL) and 1N NAOH (3.3 mL). The mixture was stirred at 0-5 C FOR 2 hours. Another portion of (BOC) 20 (100 mg) was added and the mixture was stirred for an additional 60 minutes at 0-5 C then at room temperature for 30 minutes. The mixture was then evaporated to dryness. The solid was taken in a mixture of water/EtOAc and pH was adjusted to 2 with 2N HCI. The aqueous layer was extracted 3 times with EtOAc. The combined organic layers were dried with brine and the solvent was evaporated. Some solid was insoluble in a mixture of EtOAc/CHC13 : it was removed by filtration. The desired N Boc-L-Phe-L-Phe 1 was obtained as a white foamy solid (913.7 mg, 2.215 mmol, 71% yield).