[OH:1][CH:2]1[CH2:7][CH2:6][N:5]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:4][CH2:3]1.C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.O[C:35]1[CH:40]=[CH:39][N:38]=[CH:37][CH:36]=1.N(C(OC(C)C)=O)=NC(OC(C)C)=O.C(=O)(O)[O-].[Na+]>O1CCCC1>[N:38]1[CH:39]=[CH:40][C:35]([O:1][CH:2]2[CH2:3][CH2:4][N:5]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:6][CH2:7]2)=[CH:36][CH:37]=1tert-Butyl 4-hydroxypiperidine-1-carboxylate (6.348 g, 31.546 mmol) and triphenylphosphine (10.256 g, 39.432 mmol) were added to a solution of 4-hydroxypyridine (3 g, 31.456 mmol) in tetrahydrofuran (50 ml) at room temperature. Diisopropyl azodicarboxylate (7.66 ml, 39.432 mmol) was subsequently added dropwise and the mixture was then stirred at 55° C. for 15 h. Saturated sodium bicarbonate solution (50 ml) was added to the reaction mixture and the mixture was extracted with ethyl acetate (4×80 ml). The combined organic phases were washed with sat. sodium chloride solution (20 ml), dried over sodium sulfate and concentrated in vacuo. The crude product was subsequently purified by column chromatography (silica gel) with ethyl acetate/hexane (4:1). Yield: 4.11 g (46%)
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