Cl.Cl.[NH:3]1[CH2:8][CH2:7][CH:6]([CH:9]2[CH2:14][CH2:13][NH:12][CH2:11][CH2:10]2)[CH2:5][CH2:4]1.[C:15](OC([O-])=O)([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16]>C(O)C.[OH-].[Na+]>[NH:3]1[CH2:8][CH2:7][CH:6]([CH:9]2[CH2:14][CH2:13][N:12]([C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16])[CH2:11][CH2:10]2)[CH2:5][CH2:4]1A solution is prepared of 41 g (0.17 M) of 4,4′-bipiperidine dihydrochloride in 250 ml of ethanol and 250 ml of 2N sodium hydroxide. A solution of 18.5 g (0.085 M) of t-butyl dicarbonate in 100 ml of ethanol are added slowly, at 0° C. The reaction mixture is agitated for 1 hour at 10° C. and the ethanol is then removed by an evaporator, under reduced pressure. The residual aqueous phase is saturated with sodium chloride and extracted with ethyl acetate. The organic phase obtained is dried over magnesium sulphate and concentrated under reduced pressure. The crude product is purified by silica gel chromatography in eluting with the aid of a dichloromehane/methanol/aqueous ammonia mixture (8/2/0.4; v/v/v). 16.5 g of the compound sought after are thus obtained as a white solid (yield=72%).
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