[CH2:1]([O:3][C:4]([CH:6]1[C:12](=[O:13])[CH2:11][CH2:10][N:9]([C:14]([O:16][C:17]([CH3:20])([CH3:19])[CH3:18])=[O:15])[CH2:8][CH2:7]1)=[O:5])[CH3:2].[H-].[Na+].[CH3:23]I.O>CN(C=O)C>[CH2:1]([O:3][C:4]([C:6]1([CH3:23])[C:12](=[O:13])[CH2:11][CH2:10][N:9]([C:14]([O:16][C:17]([CH3:19])([CH3:18])[CH3:20])=[O:15])[CH2:8][CH2:7]1)=[O:5])[CH3:2].[C:14]([N:9]1[CH2:8][CH2:7][CH:6]([CH3:4])[C:12](=[O:13])[CH2:11][CH2:10]1)(=[O:16])[CH3:23]A solution of compound racemic 5-oxo-azepane-1,4-dicarboxylic acid 1-tert-butyl ester 4-ethyl ester (2.5 g, 8.77 mmole) in 10 mL of DMF was added at 0° C. to a stirred suspension of NaH 60% dispersion in oil (355 mg, 8.77 mmole) in 10 mL of DMF. The reaction mixture was allowed to stir RT for one hour before being cooled to 0° C. Methyl iodide (1.37 mL, 21.92 mmole, 2.5 eqv) was added slowly and the reaction mixture was stirred at RT for 3 h before being poured into cold H2O and extracted with EtOAc (50 mL). The organic layer was washed with brine, dried, and evaporated to give 2.5 g of 4-methyl-5-oxo-azepane-1,4-dicarboxylic acid 1-tert-butyl ester 4-ethyl ester desired compound (95% yield).
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