[NH:1]([C:11]([O:13][CH2:14][C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)=[O:12])[C@H:2]([C:8]([OH:10])=[O:9])[CH2:3][CH2:4][C:5](=[O:7])[NH2:6].[CH3:21][C:22]1[CH:27]=[CH:26][C:25]([C:28](O)([C:35]2[CH:40]=[CH:39][CH:38]=[CH:37][CH:36]=2)[C:29]2[CH:34]=[CH:33][CH:32]=[CH:31][CH:30]=2)=[CH:24][CH:23]=1.C(OC(=O)C)(=O)C.S(=O)(=O)(O)O>C(O)(=O)C>[NH:1]([C:11]([O:13][CH2:14][C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)=[O:12])[C@H:2]([C:8]([OH:10])=[O:9])[CH2:3][CH2:4][C:5](=[O:7])[NH:6][C:28]([C:29]1[CH:34]=[CH:33][CH:32]=[CH:31][CH:30]=1)([C:35]1[CH:40]=[CH:39][CH:38]=[CH:37][CH:36]=1)[C:25]1[CH:24]=[CH:23][C:22]([CH3:21])=[CH:27][CH:26]=1A mixture of 140.14 g Z-Gln-OH (0.5 mole) and 274.4 g 4-methyltriphenylcarbinol (1 mole) in 1.5 l acetic acid and 93.4 ml acetic anhydride (1 mole) is stirred at room temperature for 7 minutes. Upon addition of 2.5 ml concentrated sulfuric acid the temperature is raised to 50° C.; a clear, yellow solution results after 15 minutes. After 21/2 hrs the solution is allowed to cool and poured into 5 l ice-cold water. The precipitate formed is filtered off, washed thoroughly with water and dissolved in 1 l ethylacetate. The resulting solution is washed with saturated brine, dried over sodium sulfate and concentrated under reduced pressure to an oil (400 ml) which crystallized on addition of diisopropylether.
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