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An oven dried flask was charged with (R)-tert-butyl 3-((R)-hydroxy(phenyl)methyl)-piperidine-1-carboxylate (3.18 g, 10.9 mmol) and 60% NaH in mineral oil (2.19 g, 54.8, 5 equiv). The flask was purged with N2 gas, cooled to 0° C. and anhydrous THF (100 mL) was added slowly. The mixture was allowed to warm to rt slowly. A solution of 3-ethoxypropyl methanesulfonate (6.0 g, 32.9 mmol, 3 equiv) in anhydrous THF (50 mL) was added. The mixture was heated at reflux for 4 h. LC-MS indicated the reaction completed. The reaction mixture was cooled to 0° C. slowly and water was added dropwise to quench the reaction. After separation, the aqueous layer was extracted with ether three times. The combined organic layers were washed with 5% aq HCl, satd aq NaHCO3, brine, and dried over Na2SO4. After concentration, the crude product was purified by flash chromatography on a 120-g silica gel cartridge eluted with a 0-30% EtOAc in hexanes gradient) to afford (R)-tert-butyl 3-((R)-(3-ethoxypropoxy)(phenyl)methyl)piperidine-1-carboxylate (3.70 g, 90%) as a clear oil. Chiral HPLC indicated 95.5% purity. LC-MS (3 min) tR=2.38 min, m/z 400 (M+Na). 1H NMR (CDCl3) δ 7.26 (m, 5H), 4.39 (d, 1H), 3.89 (t, 2H), 3.53-3.40 (m, 4H), 3.38-3.23 (m, 2H), 2.75-2.60 (m, 2H), 1.85-1.47 (m, 4H), 1.45 (s, 9H), 1.40-1.22 (m, 2H), 1.15 (t, 3H), 1.10-0.96 (m, 1H).

1. customAn oven dried flask
2. customThe flask was purged with N2 gas
3. additionanhydrous THF (100 mL) was added slowly
4. temperatureto warm to rt slowly
5. temperatureThe mixture was heated
6. temperatureat reflux for 4 h
7. temperatureThe reaction mixture was cooled to 0° C. slowly
8. customto quench
9. customthe reaction
10. customAfter separation
11. extractionthe aqueous layer was extracted with ether three times
12. washThe combined organic layers were washed with 5% aq HCl
13. dry with materialdried over Na2SO4
14. concentrationAfter concentration
15. customthe crude product was purified by flash chromatography on a 120-g silica gel cartridge
16. washeluted with a 0-30% EtOAc in hexanes gradient)