[BH4-].[Li+].[C:3]([O:7][C:8]([NH:10][C@H:11]1[CH2:16][CH2:15][C@H:14]([C:17](OC)=[O:18])[CH2:13][CH2:12]1)=[O:9])([CH3:6])([CH3:5])[CH3:4].C(O)(=O)CC(CC(O)=O)(C(O)=O)O.[OH-].[Na+]>C(OC)(C)(C)C.O1CCCC1>[OH:18][CH2:17][C@H:14]1[CH2:13][CH2:12][C@H:11]([NH:10][C:8](=[O:9])[O:7][C:3]([CH3:5])([CH3:4])[CH3:6])[CH2:16][CH2:15]11.56 g lithium borohydride are placed in 25 ml abs. tetrahydrofuran. A solution of 15.9 g (61 mmol) methyl trans-4-tert-butoxycarbonylamino-cyclohexanecarboxylate in 25 ml abs. tetrahydrofuran is added dropwise to this suspension. This suspension is refluxed for 50 min. After the reaction mixture has cooled it is carefully added dropwise to 25 ml of 0.6 N citric acid solution. Then 30 ml tert-butylmethylether are added, the solution is made alkaline with sodium hydroxide solution and the organic phase is separated off, washed and evaporated down.
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