反应详情

2.8 g (73.8 mmol) of sodium borohydride are added in fractions over the course of 15 minutes at room temperature to 28.0 g (73.6 mmol) of the compound obtained in Step 2 in 220 ml of tetrahydrofuran. The mixture is stirred overnight at room temperature, and then for 4 hours at reflux. After evaporation, the residue is taken up in 1 liter of dichloromethane, washed twice with 500 ml of water and then dried over magnesium sulphate. After concentration, the residue is chromatographed over silica (eluant: dichloromethane/methanol 99/1, then 98/2). The product eluted first corresponds to the cis isomer. Its stereochemistry was demonstrated by IR, in solution in chloroform, according to the method described by H. -J. Rimek et al. (Justus Liebigs Ann. Chem., 1969, 726, 25-29).

1. temperaturefor 4 hours at reflux
2. customAfter evaporation
3. washwashed twice with 500 ml of water
4. dry with materialdried over magnesium sulphate
5. concentrationAfter concentration
6. customthe residue is chromatographed over silica (eluant
7. washThe product eluted first corresponds to the cis isomer