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0 °C

To a magnetically stirred, cooled (-10° C.) solution of lithium benzyloxide in anhydrous THF (400 mL), prepared from freshly distilled benzyl alcohol (28.7 mL, 30.0 g, 277 mmol) and 127.5 mL (1.6M in hexane, 204 mmol) of n-BuLi, was added a solution of the product of step 7 (48.9 g, approx. 146 mmol) in anhydrous THF (170 mL) over a 0.5 h period. After 15 min. at -10° C., the reaction mixture was warmed to 0° C., stirred for 2 h and then quenched by the addition of half-saturated aq NH4Cl (300 mL). Volatiles were removed in vacuo and the product was extracted into CH2Cl2 (3×). The combined organic extracts were successively washed with H2O (3×) and brine, dried over MgSO4 and concentrated in vacuo to give 74 g of a pale yellow oil. This crude material was purified in two portions by flash chromatography on silica with toluene giving the title compound as a colorless liquid (32.8 g), containing a small amount of butanoic acid benzyl ester and an unidentified impurity. This product was used as such for the next step.

1. stirringstirred for 2 h
2. customquenched by the addition of half-saturated aq NH4Cl (300 mL)
3. customVolatiles were removed in vacuo
4. extractionthe product was extracted into CH2Cl2 (3×)
5. washThe combined organic extracts were successively washed with H2O (3×) and brine
6. dry with materialdried over MgSO4
7. concentrationconcentrated in vacuo