反应详情

Partially purified residue containing lactol 7, was dissolved in CH2Cl2 (40 ml) and stirred at r.t. t-BuOH (2.58 g, 3.33 ml, 34.8 mmol, 2.0 eq. based on ˜14% of 7 detected by internal standard in the previous reaction) was added via syringe. Amberlyst 15 (249 mg) and MgSO4 (5.15 g) were added as solids in one portion and the reaction mixture was stirred at r.t. for 14 h. The reaction was charged with further portions of t-BuOH (2.58 g, 3.33 ml, 34.8 mmol, 2.0 eq.), Amberlyst 15 (249 mg) and MgSO4 (5.15 g) and stirred for a further 24 h. The reaction mixture was filtered through a sinter funnel and the solids washed with CH2Cl2 (2×15 ml). The filtrate was concentrated under reduced pressure and purified by column chromatography (˜50 g silica), eluting with petrol/EtOAc (4:1), to give the t-butyl acetal 52, (as an approximately 2:1 mixture of diasteroisomers (635 mg, 2% (over 2 steps from succinaldehyde, 17% from lactol 7))) as a yellow oil.

1. customdetected by internal standard in the previous reaction)
2. additionwas added via syringe
3. stirringstirred for a further 24 h
4. filtrationThe reaction mixture was filtered through a sinter funnel
5. washthe solids washed with CH2Cl2 (2×15 ml)
6. concentrationThe filtrate was concentrated under reduced pressure
7. custompurified by column chromatography (˜50 g silica)
8. washeluting with petrol/EtOAc (4:1)