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 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