COC([CH:5]1[C:20](=[O:21])[C:9]2([CH2:12][N:11]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:10]2)[CH2:8][NH:7][C:6]1=[O:22])=O>C(#N)C.O>[C:16]([O:15][C:13]([N:11]1[CH2:12][C:9]2([C:20](=[O:21])[CH2:5][C:6](=[O:22])[NH:7][CH2:8]2)[CH2:10]1)=[O:14])([CH3:19])([CH3:17])[CH3:18]7,9-Dioxo-2,6-diaza-spiro[3.5]nonane-2,8-dicarboxylic acid 2-tert-butyl ester 8-methyl ester (Example 156g)(8.3 g; 26.6 mmol) is dissolved in acetonitrile/water (170 ml; 9/1) and refluxed for 1 hour. The reaction mixture is evaporated to dryness and delivers the title compound as white crystals (6.35 g; 94%).
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