Preparation of the Glycosyl Fluorides

The first aeetylated glycosyl fiuoride derivative was prepared by Brauns in 1923 and, in subsequent papers, he explored the synthesis of a number of poly-O-acetylglycosyl fluorides. In addition, Brauns prepared the other poly-O-acetylglycosyl halides of the same carbohydrates and investigated the proportionality relations which exist between their optical rotations and the diameters of the respective halogen atoms.  

The method of synthesis employed in this early work involved the action of anhydrous, liquid hydrogen fluoride on the fully acetylated carbohydrate. In recent years, the process has been simplified by the use of the anhydrous hydrogen fluoride commercially available, and by substitution of polyethylene equipment for the platinum vessels used earlier.  

The compounds prepared by this method are listed in the Tables. Examples of the newer methods of synthesis will now be described. 

Hydrofluoric acid (50 ml., from a tank) is added to 20 g. of 1,2,3,4,6-penta-0-aoetyl-a(or 3-)-D-gluco8e cooled to —15° in a polyethylene flask. The acetate dis- 

Most of the acetylated monosaccharides afford the more stable anomeric fluoride in this process. However, the action of a solution of hydrogen fluoride in acetic anhydride on 1,6-anhydro-j8-D-glucopyranose triacetate (1) gave tetra-O-acetyl-jS-D-glucopyranosyl fluoride (3). This result is prob- 

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