反应详情

Oxalyl chloride (14.0 ml, 160 mmol) was added dropwise to a stirred solution of (3aR,4S,6R,6aR)-6-methoxy-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxole-4-carboxylic acid (J. Amer. Chem. Soc., 80, 5168–5173 (1958)) (23.30 g, 107 mmol) in anhydrous dichloromethane (120 ml) and N,N-dimethylformamide (2 drops) and the mixture stirred at room temperature for 3 hours until gas evolution had ceased. TLC analysis showed that some starting material still remained and therefore further N,N-dimethylformamide (2 drops) was added and stirring continued for 1 hour. The solvent was removed under reduced pressure and the residue azeotroped with anhydrous dichloromethane (×2). The residue was dissolved in anhydrous dichloromethane (200 ml) and the solution treated dropwise with ethylamine (2 M solution in tetrahydrofuran, 140 ml, 280 mmol). This solution was allowed to stand at room temperature for 48 hours. Diethyl ether (250 ml) was added and the mixture stirred for 15 minutes. The mixture was filtered and the solvent removed from the filtrate under reduced pressure. The residue was purified by column chromatography on silica gel eluting with a gradient system of dichloromethane gradually changing to dichloromethane:ethyl acetate (44:66, by volume) to afford the title compound as a yellow solid (24.70 g).

1. stirringstirring
2. waitcontinued for 1 hour
3. customThe solvent was removed under reduced pressure
4. customthe residue azeotroped with anhydrous dichloromethane (×2)
5. dissolutionThe residue was dissolved in anhydrous dichloromethane (200 ml)
6. waitto stand at room temperature for 48 hours
7. stirringthe mixture stirred for 15 minutes
8. filtrationThe mixture was filtered
9. customthe solvent removed from the filtrate under reduced pressure
10. customThe residue was purified by column chromatography on silica gel eluting with a gradient system of dichloromethane