Water → Boc-Tyr(2-F)-N-Me-Val-N-Me-Tyr(3-tBu)-NH2

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Reaction Steps

To a solution of the above crude Boc-Tyr(2-F)-OH (0.82 g), N-Me-Val-N-Me-Tyr(3-tBu)-NH2 (0.77 g, 2.11 mmol) and CMPI (0.81 g, 3.17 mmol) in THF (5 ml), TEA (1.18 ml, 8.44 mmol) was added under cooling with ice and stirred at room temperature for 23 hours. The reaction mixture was mixed with water, and extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous magnesium sulfate and evaporated to remove the solvent under reduced pressure; the thus obtained residue was subjected to silica gel column chromatography (developing solvent: chloroform:methanol:concentrated aqueous ammonia=30:1:0.05), giving the titled compound (0.21 g, 15%).

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