5.0 g (14 mmoles) of H-Asp(OtBu)-D-Phg-NH2.HCl, prepared as described in Example 1, Step 4, and 4.85 g (14 mmoles) of BOC-Met-OSu are dissolved in 60 ml of DMF, and 1.96 ml (14 mmoles) of triethylamine are added to the solution. Next day the resulting suspension is evaporated in vacuo, and the residue is isolated with water. The obtained crude product, weighing 7.83 g, is decolourized in 40 ml of hot ethanol, and 40 ml of water are added to the hot solution to precipitate the product. 6.57 g (84%) of BOC-Met-Asp(OtBu)-D-Phg-NH2 are obtained; the chromatographically uniform product melts at 194°-196° C. A sample of the product melts at 197°-198° C. after recrystallization from ethanol. Rf4 =0.75; [α]D =-67.2° (c=1.0, in dimethyl formamide).
