The product from Example 8 (3.78 g; 13 mmol) and N-(fluorenylmethyloxycarbonyl)glycine (5.9 g; 20 mmol) are dissolved in anhydrous N,N-dimethylformamide (160 ml) under a protective atmosphere of argon gas. N,N'-Dicyclohexylcarbodiimide (4.11 g; 20 mmol) is added in portions at 0° C. The mixture is stirred at room temperature for 21 h and the solid which has precipitated is subsequently filtered off with suction. The solution is then concentrated in vacuo, and subsequently distilled repeatedly with toluene, and the crude product is chromatographed on silica gel. (Eluent: toluene/ethanol, 30:1-20:1). Yield: 6.33 g (82%).
