alpha-Acetobromogalactose → (2R,3S,4S,5R,6S)-2-(Acetoxymethyl)-6-fluorotetrahydro-2H-pyran-3,4,5-triyl triacetate
Reaktionsgleichung
[C:1]([O:4][C@@H:5]1[C@@H:10]([O:11][C:12](=[O:14])[CH3:13])[C@@H:9]([O:15][C:16](=[O:18])[CH3:17])[C@@H:8]([CH2:19][O:20][C:21](=[O:23])[CH3:22])[O:7][C@@H:6]1Br)(=[O:3])[CH3:2].[FH:25].[F-].[K+]>C(#N)C>[C:1]([O:4][C@@H:5]1[C@@H:10]([O:11][C:12](=[O:14])[CH3:13])[C@@H:9]([O:15][C:16](=[O:18])[CH3:17])[C@@H:8]([CH2:19][O:20][C:21](=[O:23])[CH3:22])[O:7][C@H:6]1[F:25])(=[O:3])[CH3:2]Komponenten
4
Edukt 2
Produkt 1
Reagenzien, Katalysatoren, Lösungsmittel 1
Versuchsvorschrift
10.0 g (24.3 mmol) of 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide were heated under reflux in 100 ml of anhydrous acetonitrile with 10.0 g (128 mmol) of potassium hydrogen difluoride for 6 hours. The mixture was then filtered, the solvent was stripped off in vacuo and the residue was taken up in methylene chloride. After filtration over a short silica gel column and concentration of the solution, it was possible to crystallize the product from ether. Yield 6.1 g (72%), melting point 100° C., [α·D20 =+17.5 (c=1.03 in CHCl3) [F. Micheel et al., Chem. Ber. 88, 475 (1955), melting point 98°-99° C., [α]D18 =+22 (CH3OH)]. 1H NMR (CDCl3): δ=5.26 (dd, 1-H), J1.2 =7.0, J1,F =50.0 Hz.