Lithium bis(trimethylsilyl)amide, (1M solution in toluene, 4.76 mL, 4.76 mmol) was added to a solution of (5R,6S)-1-((S)-1-(tert-butyldiphenylsilyloxy)butan-2-yl)-5-(3-chlorophenyl)-6-(4-chlorophenyl)piperidin-2-one (Example 185, Step C, 2.0 g, 3.17 mmol) and 3-bromopropene (0.274 mL, 3.17 mmol) in THF at −78° C. The reaction was warmed to 0° C. and stirred for 2 hours. After recooling to −78° C., a solution of LDA (7.93 mmol in THF) followed by 2-(chloromethoxy)ethyltrimethylsilane (0.842 mL, 4.76 mmol) was added. The reaction was warmed to 50° C. and stirred for 1.5 hours. The reaction mixture was diluted with EtOAc and washed with HCl (1N). The organic extract was washed with satd NaCl and dried over Na2SO4. The solution was filtered and concentrated in vacuo. The crude material was purified by chromatography on silica gel, eluting with a gradient of 0% to 20% EtOAc in hexane, to provide (3S,5R,6S)-3-allyl-1-((S)-1-(tert-butyldiphenylsilyloxy)butan-2-yl)-5-(3-chlorophenyl)-6-(4-chlorophenyl)-3-((2-(trimethylsilyl)ethoxy)methyl)piperidin-2-one as the first eluting diastereomer and the title compound as the second diastereomer as an oil.
