Experimental

15 (600mg, 1.39 mmol) and dioxane (30mL) were combined and saturated by bubbling O2 through the stirred solution for 15 minutes. Co(acac)2 (72mg, 0.278mmol, 0.2 equiv), was then added and a solution of PhSiH3 (0.516mL, 4.18 mmol, 3 equiv) and dioxane (3 mL) was added over 1 hour with a syringe pump. The solution continued to stir for 3 hours under an O2 atmosphere at ambient temperature. The reaction was quenched with sat. Na2S2O3, the aqueous layer was extracted with EtOAc (3 x 50mL), and the combined organic layers were washed with sat. aq. NaHCO3 (50mL) and brine (50mL). The solution was dried over Na3SO4 and then concentrated using vacuum filtration. Silica gel chromatography (2:3 to 3:2 EtOAc:hexanes) was performed to produce protected ouabageninone 16 as a white solid (538mg, 86% yield). IR (film) λmax: 3418, 2935, 2875, 1730, 1644, 1402, 1378, 1334, 1281, 1223, 1205, 1056cm-1.

The syringe pump allows for the PhSiH3 and dioxane to be added at a controlled rate for 1 hour. (image: sciencedirect.com)

Vacuum filtration is effective when purifying crystals or another solid product. (image: http://quiz2.chem.arizona.edu/vip/filtration/)

Silica gel chromatography is an effective way to separate a mixture of solvents (eluent) present in a solution. Each compound runs through the column at a different speed due to polarity. The less polar compound does not have as many interactions with the silica gel, and as a result comes off of the column first. Since the compounds travel down the column at different speeds, fractions are collected with the prospect that there is at least one pure fraction for each individual compound. (image: thesliquidphase.org)