Methanol → Becocalcidiol

Participants

Reaction Steps

Ozone was passed through a solution of vitamin D2 (3 g, 7.6 mmol) in methanol (250 mL) and pyridine (2.44 g, 2.5 mL, 31 mmol) for 50 minutes at −78° C. The reaction mixture was then flushed with oxygen for 15 min to remove the residual ozone, and the solution was treated with NaBH4 (0.75 g, 20 mmol). After 20 minutes, the second portion of NaBH4 (0.75 g, 20 mmol) was added, and the mixture was allowed to warm to room temperature. The third portion of NaBH4 (0.75 g, 20 mmol) was then added and the reaction mixture was stirred for 18 hours. The reaction was quenched with water (40 mL), and the solution was concentrated under reduced pressure. The residue was extracted with ethyl acetate (3×80 mL), and the combined organic phases were washed with 1M aq. HCl, saturated aq. NaHCO3, dried (Na2SO4) and concentrated under reduced pressure. The residue was chromatographed on silica gel with hexane/ethyl acetate (75:25) to give (20S)-de-A,B-20-(hydroxymethyl)pregnan-8β-ol 1 (1.21 g, 75% yield) as white crystals.

Provenance & Evidence