[C:1]([O:5][C:6]([N:8]1[CH:14]2[CH:9]1[CH2:10][CH2:11][O:12][CH2:13]2)=[O:7])([CH3:4])([CH3:3])[CH3:2].Cl([O-])(=O)(=O)=O.[Li+].[N-:21]=[N+:22]=[N-:23].[Na+].O>C(#N)C>[C:1]([O:5][C:6](=[O:7])[NH:8][C@H:14]1[C@H:9]([N:21]=[N+:22]=[N-:23])[CH2:10][CH2:11][O:12][CH2:13]1)([CH3:4])([CH3:3])[CH3:2]3-Oxa-7-aza-bicyclo[4.1.0]heptane-7-carboxylic acid tert-butyl ester (intermediate E) (5.2 g, 26 mmol) was dissolved in 100 mL acetonitrile. Lithium perchlorate (23 g, 207 mmol) and sodium azide (6.8 g, 104 mmol) were added and the reaction mixture was stirred at 80° C. overnight. 200 mL Water was added. The mixture was extracted three times with diethylether. The combined organic phases were dried on sodium sulfate, filtered and evaporated. Purification of the residue by flash chromatography on silica gel (heptane/ethyl acetate 1:0→1:1) yielded the title compound as a colorless oil (3.3 g, 52%), MS: m/e=186 [(M-butene)+].
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