反应详情

To a stirred mixture of D-alanine methyl ester hydrochloride (1, 12 g, 85.9 mmol) in anhydrous dichloromethane (120 mL) was added potassium acetate (8.5 g, 85.9 mmol) and the resulting reaction mixture was stirred at rt for ten minutes. The reaction was then cooled to 10° C. and treated with 1,4-dioxaspiro[4.5]decan-8-one (2, 13.4 g, 85.9 mmol), followed by the addition of sodium triacetoxyborohydride (22.6 g, 106.6 mmol) in portions over a period of ten minutes. The resulting reaction mixture was stirred at rt for 16 h. Saturated aqueous sodium bicarbonate solution was then added to the reaction and the mixture was stirred for another 30 minutes. Dichloromethane layer was separated and the aqueous layer was extracted with dichloromethane (100 mL×3). Organic layers were combined, washed with brine, dried over sodium sulfate, and evaporated to give the crude product as colorless oil (14 g), which was used for next step without any further purifications. 1HNMR (300 MHz, CDCl3): δ 1.22 (d, 3H), 1.40-1.61 (m, 4H), 1.65-1.90 (m, 4H), 2.42-2.55 (m, 1H), 3.42 (q, 1H), 3.72 (s, 3H), 3.98 (s, 4H).

1. customthe resulting reaction mixture
2. temperatureThe reaction was then cooled to 10° C.
3. customThe resulting reaction mixture
4. stirringwas stirred at rt for 16 h
5. stirringthe mixture was stirred for another 30 minutes
6. customDichloromethane layer was separated
7. extractionthe aqueous layer was extracted with dichloromethane (100 mL×3)
8. washwashed with brine
9. dry with materialdried over sodium sulfate
10. customevaporated