[CH3:1][C:2]1([C:17]([O:19]C)=[O:18])[N:9]([C:10]([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11])[CH2:8][CH2:7][C:4]2([CH2:6][CH2:5]2)[CH2:3]1.O[Li].O>O1CCOCC1.O>[C:13]([O:12][C:10]([N:9]1[CH2:8][CH2:7][C:4]2([CH2:5][CH2:6]2)[CH2:3][C:2]1([CH3:1])[C:17]([OH:19])=[O:18])=[O:11])([CH3:16])([CH3:14])[CH3:15]6-tert-butyl 5-methyl 5-methyl-6-azaspiro[2.5]octane-5,6-dicarboxylate (D5) (320 mg, 1.13 mmol) was partitioned between dioxane/water (8/8 ml) prior addition of LiOH H2O (190 mg, 4.52 mmol). The mixture was stirred at RT for 18 hrs then heated at 150° C. under microwave irradiation 40 min (4 cycles of 10 min each). Organic solvent was evaporated off and the aqueous solution washed with EtOAc (2×10 ml), acidified to pH˜4 with citric acid sat. sol. and extracted with EtOAc (3×10 ml). The organic phases were washed with NaCl sat. sol, dried over Na2SO4 and evaporated to reduced pressure to afford the title compound (D6) (114 mg).
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