[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][N:11]([C:14]2[N:19]=[CH:18][C:17]([C:20]([OH:22])=[O:21])=[CH:16][N:15]=2)[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].CO.[CH:25]1C=CC=CC=1.C[Si](C=[N+]=[N-])(C)C>C(O)(=O)C>[CH3:25][O:21][C:20]([C:17]1[CH:16]=[N:15][C:14]([N:11]2[CH2:10][CH2:9][N:8]([C:6]([O:5][C:1]([CH3:4])([CH3:2])[CH3:3])=[O:7])[CH2:13][CH2:12]2)=[N:19][CH:18]=1)=[O:22]To 2-(4-tert-Butoxycarbonyl-piperazin-1-yl)-pyrimidine-5-carboxylic acid (150 mg, 0.486 mmol) in an oven dried round-bottom flask is added methanol (1.0 mL) and benzene (3.7 mL) under nitrogen, and the reaction stirred for 10 min. Trimethylsilyldiazomethane (0.34 ml, 0.678 mmol) is added and the reaction stirred for 1 h. Glacial acetic acid (0.05 ml) is then added until the yellow color has disappeared. The reaction mixture is concentrated under reduced pressure and co-evaporated with benzene. It is dried under high vacuum to yield the title compound as a white solid (155 mg, 99% yield).
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