Diisopropylamine → 4-[1-Carboxy-2-(4-fluoro-phenyl)-ethyl]-4-hydroxy-piperidine-1-carboxylic acid tert-butyl ester

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Reaction Conditions

Reaction Steps

n-Butyllithium (1.6 M in hexane, 8.8 mL, 14.0 mmol) was added dropwise under stirring over 5 min to a cooled solution of N,N-diisopropylamine (2.0 mL, 14.0 mmol) in THF (10 mL) at −40° C. The solution was warmed to 0° C. and a solution of 3-(4-fluoro-phenyl)propionic acid (1.18 g, 7.0 mmol) in THF (8 mL) was added. The mixture was stirred for 30 min at rt, cooled to −78° C. and N-BOC-4-piperidone (1.68 g, 8.4 mmol) in THF (7 mL) added dropwise over 15 min. The solution was allowed to warm to rt and poured into a stirred mixture of diethylether (100 mL) and water (50 mL). The organic layer was discarded, the aqueous layer extracted with another portion of diethylether. The aqueous layer was acidified with 2 M aq. HCl to pH 3.5 and extracted with dichloromethane (3×100 mL). The combined extracts were dried over Na2SO4, filtered and concentrated in vacuo, giving 69NLS56 as a yellow solid, which is used without further purification.

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