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xie0311

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Sodium triethylborohydride  (840 μL of a 1 M solution in THF, 0.843 mmol, 10 equ iv) was added dropwise to a room  temperature solution of digoxin (65.8 mg, 0.0843 mmol, 1.0  equiv) in THF (16.9 mL, 5  mM). After 10 min, the reaction was quenched with the slow addition of methanol (5  mL), stirred for 15 min, and concentrated in vacuo to afford an inseparable mixture of  saturated diol (Dig(dhd)) and alkene diol (20,22 -alkene) (~3:1 of satur ated:alkene) as a white solid.  R f  = 0.15 (9:1 ethyl acetate/methanol).  The crude material was used without  purification.  
To the above mixture of compounds in methanol (4.2 mL, 20 mM) was added  10 wt% palladium on carbon (9.0 mg, 0.0084 mmol, 0.1 equiv). The reaction atmosphere  was sparged with hydrogen and the contents were stirred under a balloon of hydrogen for  16 h, at which point the reaction was filt ered through Celite and concentrated in vacuo.  The crude material was dry-loaded onto Celite and purified by flash chromatography on  silica gel (19:1 → 9:1  → 85:15 dichloromethane/methanol) to afford Dig(dhd) (63.7 mg,  0.0809 mmol, 96% yield over two steps ) as a white solid. Dig(dhd) was obtained as a  ~1.5:1 mixture of diastereomers that were not separated.
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咸鱼贩

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感谢参与,应助指数 +1
mouse103: 金币+1, 谢谢参与 2012-04-23 08:33:18
xie0311: 金币+30, ★★★★★最佳答案 2012-04-23 10:55:37
三乙基硼氢化钠的THF溶液室温下逐滴加至地高辛的THF溶液中,反应10min后缓慢滴加5ml甲醇将反应猝灭,搅拌15min,减压浓缩得到饱和二醇和不饱和二醇(~3:1)的混合物,白色固体。Rf=0.15(乙酸乙酯:甲醇=9:1),所用原料均未经纯化。
将上诉白色固体溶于甲醇4.2ml,加10 wt%钯碳。在氢气饱和后加上氢气球,继续搅拌反应16h,然后反应液用硅藻土过滤,减压浓缩。粗产物干装至硅藻土上(相当于拌样),硅胶上急骤层析(二氯甲烷/甲醇梯度洗脱),得到Dig(dhd) ,为白色固体,1.5:1的对映异构体混合物,未分离。
2楼2012-04-22 23:26:20
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