反应详情

The ketal intermediate (step vi) in a mixture of 6M HCl-butanone (1:4, v/v, 100 mL) was refluxed for 16 hours. The butanone was evaporated in vacuo and the residual aqueous layer was diluted with more water (100 mL). The acidic aqueous layer was extracted with diethyl ether (2×40 mL) and then with dichloromethane (3×40 mL). The combined dichloromethane extracts were dried over sodium sulfate and the solvent was evaporated in vacuo to provide the crude title compound. The product was crystallized by triturating in diethyl ether and reprecipitated from a mixture of dichloromethane-diethyl ether to yield 1.8 g (72% yield) of the title compound, having the elemental analysis indicated in Table 1.

1. temperaturewas refluxed for 16 hours
2. customThe butanone was evaporated in vacuo
3. additionthe residual aqueous layer was diluted with more water (100 mL)
4. extractionThe acidic aqueous layer was extracted with diethyl ether (2×40 mL)
5. dry with materialThe combined dichloromethane extracts were dried over sodium sulfate
6. customthe solvent was evaporated in vacuo
7. customto provide the crude title compound
8. customThe product was crystallized
9. customby triturating in diethyl ether
10. customreprecipitated from a mixture of dichloromethane-diethyl ether