Br[CH:2]([C:8]([O:10][CH2:11][CH3:12])=[O:9])[C:3]([O:5][CH2:6][CH3:7])=[O:4].C(=O)([O-])[O-].[K+].[K+].[CH:19]12[O:26][CH:23]([CH2:24][CH2:25]1)[CH2:22][NH:21][CH2:20]2>C(#N)C>[CH:23]12[O:26][CH:19]([CH2:25][CH2:24]1)[CH2:20][N:21]([CH:2]([C:8]([O:10][CH2:11][CH3:12])=[O:9])[C:3]([O:5][CH2:6][CH3:7])=[O:4])[CH2:22]24.72 g (19.8 mmol) of diethyl 2-bromomalonate are introduced into 30 ml of acetonitrile. Then 3.82 g (27.7 mmol) of potassium carbonate and 2.46 g (21.7 mmol) of 8-oxa-3-azabicyclo[3.2.1]octane from step 4 are added. The suspension is stirred at 50° C. overnight. This is followed by filtration with suction and evaporation of the filtrate to dryness in a rotary evaporator. The residue is employed without further purification in the next stage.
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