C([N:11]1[CH2:16][CH2:15][CH:14]([N:17]2[CH2:21][CH2:20][N:19]([CH2:22][CH2:23][O:24]C3CCCCO3)[C:18]2=[O:31])[CH2:13][CH2:12]1)(OCC1C=CC=CC=1)=O.Cl.[H][H]>CO.[Pd]>[OH:24][CH2:23][CH2:22][N:19]1[CH2:20][CH2:21][N:17]([CH:14]2[CH2:13][CH2:12][NH:11][CH2:16][CH2:15]2)[C:18]1=[O:31]A solution of 59.7 g of 1-(1-carbobenzoxy-4-piperidyl)-3-[2(2-tetrahydropyranyloxy)-ethyl]-imidazolidin-2-one in 1,200 ml of absolute methanol is hydrogenated at room temperature and normal pressure with the addition of 1 mol equivalent of hydrochloric acid and 6 g of palladium-on-charcoal catalyst until 2 mol equivalents of hydrogen have been taken up. The catalyst is then filtered off and the filtrate is evaporated under reduced pressure. The residue is freed from moisture which is still adhering, by treatment with toluene. The reaction product is chromatographed on 2 kg of basic aluminium oxide using a mixture of chloroform/methanol (85:15) as the eluant mixture. In this way, 3-(2-hydroxyethyl)-1-(4-piperidyl)-imidazolidin-2-one is obtained in the form of a viscous oil, which is further used without additional purification.
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