[Cl:1][CH2:2][C:3](Cl)=[O:4].[NH2:6][CH2:7][CH2:8][C:9]1([OH:22])[CH2:14][CH2:13][N:12]([C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16])[CH2:11][CH2:10]1.C(=O)([O-])[O-].[K+].[K+]>C(OCC)(=O)C.O>[Cl:1][CH2:2][C:3]([NH:6][CH2:7][CH2:8][C:9]1([OH:22])[CH2:14][CH2:13][N:12]([C:15]([O:17][C:18]([CH3:20])([CH3:19])[CH3:21])=[O:16])[CH2:11][CH2:10]1)=[O:4]Chloroacetyl chloride (0.483 mL) was added dropwise over 10 minutes to a vigorously stirred mixture at 0° C. of tert-butyl 4-(2-aminoethyl)-4-hydroxypiperidine-1-carboxylate (example 89, step b) (1.1 g) in ethyl acetate (25 mL) and potassium carbonate (1.77 g) dissolved in water (20 mL). The mixture was then stirred at 0° C. for 45 minutes before being extracted with ethyl acetate. The organic layer was dried over sodium sulphate, filtered and the solvent evaporated under reduced pressure. The crude product was purified by flash silica chromatography eluting with ethyl acetate. Pure fractions were evaporated to dryness to afford the subtitled compound. Yield 0.9 g.
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