1-methoxypiperidin-4-ol

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 1-methoxy-piperidin-4-one [prepared according to Journal of Organic Chemistry (1961), 26, 1867-74] (15.0 g, 116.1 mmol) in ethanol (430 ml) was added sodium borohydride 96% (2.29 g, 58.1 mmol) in portions. The reaction mixture was stirred at room temperature for 5 hours, evaporated to half of its volume, poured on cold saturated aqueous ammonium chloride and thoroughly extracted with ethyl acetate. The combined organic layers were washed with brine, dried over sodium sulfate and concentrated. The residue was purified by chromatography on silica gel (ethyl acetate). Yield: 10.9 g of 1-methoxy-piperidin-4-ol as a liquid. evaporated to half of its volume poured on cold saturated aqueous ammonium chloride thoroughly extracted with ethyl acetate The combined organic layers were washed with brine dried over sodium sulfate concentrated The residue was purified by chromatography on silica gel (ethyl acetate)

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 21 g 1-Methoxy-piperidin-4-ol (from Step 1) and 19.4 g triethylamine were dissolved in 200 ml ethyl acetate, and cooled to 0° C. 15.0 g Methanesulfonyl chloride was added slowly. The resulting white suspension was stirred at 0° C. for 1 hour, then at room temperature for an additional 1 hour. Then the mixture was filtered and the solvent evaporated, yielding 34.6 g of methanesulfonic acid 1-methoxy-piperidin-4-yl ester. This material was used for the next step without further purification. at room temperature for an additional 1 hour Then the mixture was filtered the solvent evaporated

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Under an atmosphere of argon, 200 ml ethanol was cooled to 10° C. and 3.7 g sodium borohydride was added. A solution of 25 g 1-methoxy-piperidin-4-one (prepared according to J. Org. Chem. 1961, 26, 1867-74) in 200 ml ethanol was added to the stirred suspension, while the temperature was kept in the range of 15-20° C. Then the mixture was stirred at ambient temperature for 3 hours. 50 ml aqueous ammonium chloride was added slowly and then the solvent evaporated. The residue was purified by chromatography on silica gel, using ethyl acetate as a solvent. Thus, 22.8 g 1-methoxy-piperidin-4-ol was obtained. was kept in the range of 15-20° C the solvent evaporated The residue was purified by chromatography on silica gel

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of triphenylphosphine (1.11 g, 4.23 mmol) in THF (20 ml) at 0° C. was added diisopropyl azodicarboxylate (0.83 ml, 0.85 g, 4.24 mmol) dropwise and the resulting precipitate was stirred at 0° C. for 30 minutes. 4-{Hydroxy-[2-(2,4,6-trimethyl-phenyl)-acetyl]-amino}-1-methoxy-piperidine-4-carboxylic acid methyl ester (compound P3ii.3 obtained in analogy to preparation example 11, step 4) (1.3 g, 3.57 mmol) was further added in one portion, followed by a solution of 1-methoxy-piperidin-4-ol (0.53 g, 4.04 mmol) in THF (6 ml) dropwise at 0° C. The reaction mixture was stirred at room temperature for two hours and concentrated in vacuo. The residue was triturated with hexane and filtered to remove part of the insoluble triphenylphosphine oxide. The filtrate was evaporated and the residue purified by chromatography on silica gel (gradient ethyl acetate/heptane 3:7→ethyl acetate). Yield: 861 mg of pure 1-methoxy-4-{(1-methoxy-piperidin-4-yloxy)-[2-(2,4,6-trimethyl-phenyl)-acetyl]-amino}-piperidine-4-carboxylic acid methyl ester (title compound P3ii.26) as a colorless gum, followed by a second fraction of compound P3ii.26 (701 mg) slightly contaminated with triphenylphosphine oxide. The reaction mixture was stirred at room temperature for two hours concentrated in vacuo The residue was triturated with hexane filtered to remove part of the insoluble triphenylphosphine oxide The filtrate was evaporated the residue purified by chromatography on silica gel (gradient ethyl acetate/heptane 3:7→ethyl acetate)