反应详情

A mixture of methyl α-D-mannopyranoside (Compound I, 50 g, 258 mmoles), α,α-dimethoxytoluene (92 g, 600 mmoles), and anhydrous p-toluene-sulfonic acid (1 g) in N,N-dimethylformamide (300 ml), in a 1-liter flask fitted with an air condenser attached to a water aspirator, was stirred magnetically and heated in an oil bath for 3 hours at 65°-75° C. None of the starting Compound I remained after this time (t.l.c., 4:1 ether-petroleum ether). The mixture was poured with vigorous stirring into 1 liter of ice-water containing sodium hydrogen carbonate (30 g). The resultant precipitate was filtered off, resuspended in ice-water, filtered off again, and dried in air and finally in vacuo over phosphorus pentaoxide; yield 90.6 g (95%), m.p. 120°-160° C, [α]D23 -33° (c 1, chloroform).

1. customin a 1-liter flask fitted with an air condenser
2. temperatureheated in an oil bath for 3 hours at 65°-75° C
3. additionThe mixture was poured
4. filtrationThe resultant precipitate was filtered off
5. filtrationfiltered off again
6. dry with materialdried in air and finally in vacuo over phosphorus pentaoxide