ORGANOFLUORINE COMPOUNDS AND FLUORINATING AGENTS .11. GLYCOSYL FLUORIDES FROM ACETAL-PROTECTED SUGARS

-Acetoxyethyl)-3,4,6-tri-O-methyl-alpha-D-glucosyl fluoride (5) was ob tained by partial cleavage of the 1,2-O-ethanediyl-beta-D-glucopyranos e derivative 4 at the glycosidic position by means of the HF/nitrometh ane/acetic anhydride system. The same medium allows the selective clea vage of the 1,2-isopropylidene function in alpha-D-glucofuranosides (7 , 11) and of the 5,6-0-isopropylidene group in acetyl 2,3:5,6-di-O-iso propylidene-D-manno-furanoside (15) with simultaneous conversion into the corresponding acetylated glycosyl fluorides (8, 12, 16). The secon d acetal function in 11 and 15 is not cleaved by the weakened HF mediu m. 2-0-Benzyl-protected sugars such as methyl 3,5,6-tri-O-methyl-2-O-b enzyl-D-glucofuranoside (13) react intramolecularly in the presence of HF/nitromethane/acetic anhydride to form a cyclic C-glycoside (14).