Methanol → benzyl-2(R)-[1(S)-(tert-butoxycarbonyl)-3-hydroxypropyl]-4-methylvalerate

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Reaction Steps

A solution of 32.12 g of (E)-benzyl-2(R)-[1(S)-(tert-butoxycarbonyl)-4-phenyl-3-butenyl]-4-methylvalerate in 300 ml of dichloromethane was cooled to −78° C. and ozone was then bubbled through the mixture for 2.5 hours. 35 ml of dimethyl sulfide was then addded to the mixture and stirring continued overnight at room temperature. The solvent was evaporated to give an orange oil. This was dissolved in 300 ml of methanol, cooled to 0° C. under nitrogen and then treated portionwise with 5.6 g of sodium borohydride. The mixture was then quenched with glacial acetic acid and evaporated. The residue was dissolved in ethyl acetate and washed sequentially with 2M aqueous hydrogen chloride, water, 5% aqueous sodium hydrogen carbonate and brine and then dried over anhydrous magnesium sulfate. Filtration and evaporation gave a residue which was purified by flash column chromatography on silica gel, using ethyl acetate/hexane (2:8 increasing to 4:6) for the elution, to give 15.3 g of benzyl-2(R)-[1(S)-(tert-butoxycarbonyl)-3-hydroxypropyl]-4-methylvalerate in the form of a pale yellow oil.

Provenance & Evidence