Reaction SMILES: [C:1]([O:5][C:6]([NH:8][C@@H:9]([CH2:13][CH2:14][CH2:15][CH2:16][OH:17])[C:10]([OH:12])=[O:11])=[O:7])([CH3:4])([CH3:3])[CH3:2].[Si](C=[N+]=[N-])(C)(C)[CH3:19]>C(Cl)Cl.CO>[CH3:19][O:11][C:10](=[O:12])[C@@H:9]([NH:8][C:6]([O:5][C:1]([CH3:4])([CH3:3])[CH3:2])=[O:7])[CH2:13][CH2:14][CH2:15][CH2:16][OH:17]
Reactant: C[Si](C)(C)C=[N+]=[N-]
Reactant: CC(C)(C)OC(=O)N[C@@H](CCCCO)C(=O)O
Solvent: ClCCl
Solvent: CO
Product: COC(=O)[C@H](CCCCO)NC(=O)OC(C)(C)C
Reaction time: 1 h

Procedure:
To a solution of (S)-2-tert-butoxycarbonylamino-6-hydroxy-hexanoic acid (1 g, 6 mmol) in 30 mL of CH2Cl2 and 5 mL of MeOH at rt was slowly added TMSCHN2 (10 mL), and the reaction mixture was left with stirring for 1 h. The solvent was remove under reduced pressure, and the resulting residue was diluted with water and EtOAc. The organic layer was separated, dried over Na2SO4, and concentrated to afford an oil (S)-2-tert-butoxycarbonylamino-6-hydroxy-hexanoic acid methyl ester. MS [M+H]+ 262. (37b) To a solution of oxalyl chloride (0.33 mL, 0.36 mmol) in CH2Cl2 (10 mL) at −78 C. was added DMSO (0.1 mL, 1.32 mmol). Ten minutes later, a solution of alcohol (S)-2-tert-butoxycarbonylamino-6-hydroxy-hexanoic acid methyl ester (144 mg, 0.55 mmol) in CH2Cl2 (10 mL) was added and stirred for 15 min before iPr2NEt (0.5 mL, 2.7 mmol) was added. The reaction mixture was allowed to warm up to 0 C and left with stirring for 2 h before water and EtOAc were added. The organic layer was separated, dried over Na2SO4, and concentrated to afford to a crude oil (S)-2-tert-butoxycarbonylamino-6-oxo-hexanoic acid methyl ester. (37c) To a solution of (1S*,2R*,4R*)-4-azido-2-benzenesulfonylmethyl-cyclohexylamine (see example 10, steps 10a-10d with the substitution of methyl phenyl sulfone in step 10a and then treated with TFA) (135 mg, 0.45 mmol) and (S)-2-tert-butoxycarbonylamino-6-oxo-hexanoic acid methyl ester (140 mg, 0.55 mmol) in CH2Cl2 (15 mL) at rt was added NaBH(OAc)3 (194 mg, 0.9 mmol). After 16 h, the solution was concentrated. The resulting residue was re-dissolved in EtOAc and washed with saturated NaHCO3, water, and brine. The organic layer was dried, filtered, and concentrated to afford to a crude oil (1S,2R,3S,4R)-6-(4-azido-2-benzenesulfonylmethyl-cyclohexylamino)-2-tert-butoxycarbonylamino-hexanoic acid methyl ester. MS [M+H]+=538. (37d) To a solution of (1S,2R,3S,4R)-6-(4-azido-2-benzenesulfonylmethyl-cyclohexylamino)-2-tert-butoxycarbonylamino-hexanoic acid methyl ester (270 mg) in THF (15 mL) and H2O (3 mL) at rt was added LiOH (24 mg). After 1 h, the reaction was diluted with water and EtOAc. Upon adjusting the pH value to 7, the organic layer was collected, dried, and concentrated to afford to a crude oil (140 mg) which was re-dissolved in DMF (15 mL), followed by the addition of HATU (132 mg, 0.34 mmol) and Hunig's base (0.06 mL, 0.34 mmol). The resulting mixture was stirred for 16 before EtOAc was added. The EtOAc layer was washed with 1 N HCl, NaHCO3 solution (aq), and brine. The EtOAc was dried (MgSO4), filtered, and concentrated. Flash chromatography of the resulting residue gave [(3S)-1-(1S,2R,4R)-(4-azido-2-benzenesulfonylmethyl-cyclohexyl)-2-oxo-azepan-3-yl]-carbamic acid tert-butyl ester (120 mg). MS found: (M+H)+=506. (37e) To a solution of [(3S)-1-(1S,2R,4R)-(4-azido-2-benzenesulfonylmethyl-cyclohexyl)-2-oxo-azepan-3-yl]-carbamic acid tert-butyl ester (120 mg) in CH2cl2 (10 mL) was added TFA (3.3 mL). After 45 min, the solution was diluted with NaHCO3solution (aq) and EtOAc. The organic layer was collected, dried, and concentrated to afford to a crude oil 3-amino-(3S)-1-(1S,2R,4R)-(4-azido-2-benzenesulfonylmethyl-cyclohexyl)-azepan-2-one. MS [M+H]+=406. (37f) To a solution of 3-amino-(3S)-1-(1S,2R,4R)-(4-azido-2-benzenesulfonylmethyl-cyclohexyl)-azepan-2-one (50 mg, 0.12 mmol) in DMF (15 mL) was added 3-trifluoromethyl benzoic acid (28 mg, 0.15 mmol), HATU (57 mg, 0.15 mmol) and Hunig's base (0.03 mL, 0.15 mmol). The resulting mixture was stirred for 16 h before EtOAc was added. The EtOAc layer was washed with 1 N HCl, NaHCO3solution (aq), and brine. The EtOAc was dried (MgSO4), filtered, and concentrated. Flash chromatography of the resulting residue gave N-[(3S)-1-(1S,2R,4R)-(4-azido-2-benzenesulfonylmethyl-cyclohexyl)-2-oxo-azepan-3-yl]-3-trifluoromethyl-benzamide (70 mg). MS found: (M+H)+=578. (37 g) N-[(3S)-1-(1S,2R,4R)-(4-Azido-2-benzenesulfonylmethyl-cyclohexyl)-2-oxo-azepan-3-yl]-3-trifluoromethyl-benzamide (70 mg) was dissolved in MeOH (10 mL) prior to the addition of 10% Pd/C (20 mg). A hydrogen balloon was added and the solution was stirred at rt for 16 h. The palladium was filtered and the solvent was concentrated to N-[(3S)-1-(1S,2R,4R)-(4-amino-2-benzenesulfonylmethyl-cyclohexyl)-2-oxo-azepan-3-yl]-3-trifluoromethyl-benzamide. MS found: (M+H)+=552. (37 h) To a solution of N-[(3S)-1-(1S,2R,4R)-(4-amino-2-benzenesulfonylmethyl-cyclohexyl)-2-oxo-azepan-3-yl]-3-trifluoromethyl-benzamide (30 mg) in CH2Cl2 (15 mL) at rt was added NaBH(OAc)3 (50 mg), acetone (2 mL), and three drops of AcOH. After 2 h, formaldehyde (2 mL) was added and the solution was stirred for another 2 h. The reaction mixture was diluted with EtOAc and washed with saturated NaHCO3, water, and brine. The organic layer was dried, filtered, and concentrated to afford to a crude oil which was purified by semi-preparative HPLC to give the title compound. MS [M+H]+=608.