355.0 mg (0.52 mmol) of ethyl 3-((S)-2-{(R)-2-tert-butoxycarbonylamino-3-[4-(9H-fluoren-9-ylmethoxycarbonylamino)phenyl]propionylamino}-3-methylbutoxy)propionate were dissolved in a mixture of 9 ml of THF and 3 ml of MeOH. 1.29 ml (1.29 mmol) of an aqueous 1M LiOH solution were added, and the resulting reaction mixture was stirred at room temp. for 1 h. After the reaction was complete, the mixture was neutralized by adding a little aqueous 1N HCl solution, concentrated under reduced pressure and codistilled with toluene. The product obtained in this way (225.0 mg) was employed crude in the next reaction.
