[CH2:1]([O:3][C:4]([CH:6]1[CH2:14][CH2:13][CH2:12][CH2:11][CH2:10][CH2:9][CH2:8][C:7]1=[O:15])=[O:5])[CH3:2].CS(O)(=O)=O.[N-:21]=[N+]=[N-].[Na+].[OH-].[NH4+]>C(Cl)(Cl)Cl>[O:15]=[C:7]1[CH2:8][CH2:9][CH2:10][CH2:11][CH2:12][CH2:13][CH2:14][CH:6]([C:4]([O:3][CH2:1][CH3:2])=[O:5])[NH:21]12-Ethoxycarbonyl-cyclononanone (13.72 g, 64.7 mmol) is dissolved in chloroform (200 mL) and cooled to 0° C. Methanesulfonic acid (62.4 g, 650 mmol) is added, followed by sodium azide (12.68 g, 195 mmol). The reaction is stirred at room temperature for 30 minutes, and then heated to reflux for 4 hours. The reaction mixture is poured onto ice, made basic with concentrated ammonium hydroxide (pH=9), and extracted several times with methylene chloride. The combined organic layers are dried (MgSO4), and the solvent is evaporated. The product is purified by silica gel chromatography (40% ethyl acetate/hexane) to give ethyl 2-oxo-1-azacyclodecane-10-carboxylate, m.p. 101°-103° C.
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