反应详情

4.0 g (about 15 mmol) of the compound from Example I are heated to reflux overnight in 100 ml of isopropanol with 2.2 g (15 mmol) of isopropyl 3-amino-2-butenoate. After thin-layer chromatographic checking (SiO2, toluene/ethyl acetate 5:1) shows complete conversion, the reaction mixture is concentrated, the residue is-taken up with toluene, the solution is concentrated again and the residue is then purified by filtration on silica gel (eluent: toluene/ethyl acetate 100:1-5:1). A crystallizing yellow oil is obtained, which is recrystallized from methanol at about −15° C. 2.8 g (48%) of the target compound are obtained.

1. concentrationthe reaction mixture is concentrated
2. concentrationthe residue is-taken up with toluene, the solution is concentrated again
3. filtrationthe residue is then purified by filtration on silica gel (eluent: toluene/ethyl acetate 100:1-5:1)
4. customA crystallizing yellow oil is obtained
5. customwhich is recrystallized from methanol at about −15° C