Imidazole → 4-Benzyl 3-(tert-butyl) (S)-1,2,3-oxathiazolidine-3,4-dicarboxylate 2,2-dioxide

Beteiligte Stoffe

Reaktionsschritte

In an inert atmosphere and under exclusion of moisture, at 0° C. a solution of 6.9 g (102 mmol) of imidazol in 80 ml of dichloromethane was treated dropwise within 15 minutes with a solution of 2.2 ml (30 mmol) of thionylchloride in 30 ml of dichloromethane. After complete addition, the reaction mixture was left to warm to room temperature and stirring was continued for 30 minutes. Thereafter, a solution of 5.0 g (17 mmol) of (S)-2-tert-butoxycarbonylamino-3-hydroxy-propionic acid benzyl ester in 20 ml of dichloromethane was added dropwise at −78° C. After 1 hour at −78° C., the reaction mixture was left to warm to room temperature and stirring was continued overnight. For the working-up, the reaction mixture was quenched with 150 ml of a solution (10%) of citric acid. The organic layer was separated, washed with water, dried over sodium sulfate, and evaporated. The crude product (5.5 g of a colourless oil) was dissolved in 50 ml of ethyl acetate and cooled to 0° C. Thereafter, an aqueous solution (10%) of 9.0 g (29 mmol) of sodium metaperiodate, cooled to 0° C., and 0.36 g (2 mmol) of ruthenium(IV)oxide hydrate were added. After stirring at 0° C. for 30 minutes, the organic layer was separated, filtered over Dicalit and silica gel, and, finally, evaporated under reduced pressure. There were obtained 4.0 g (66%) of the (S)-2,2-dioxo-2λ6-[1,2,3]oxathiazolidine-3,4-dicarboxylic acid 4-benzyl ester 3-tert-butyl ester as a grey solid, [α]589=−21.51° (c=1.0% in MeOH), MS m/e (%): 356.0 (M−H+, 100).

Herkunft & Nachweise