The Fluorination (at C5) of Some Derivatives of D-Glucose

Abstract

The photobromination of various per-esters of β-D-glucopyranose and α- and β-D-glucopyranosyl fluoride has yielded 5-bromo derivatives capable of conversion into the corresponding 5-fluorides. The best reagent for this conversion was found to be silver tetrafluoroborate in ether/dichloromethane. The single-crystal X-ray structure determination of penta-O-benzoyl-5-fluoro-α-L-idopyranose is presented.As well, various approaches to 5-fluoro glycopyranosides have been developed. The photobromination of phenyl tetra-O-acetyl-β-D-glucopyranoside, followed by fluorination and protecting group removal gave phenyl 5-fluoro-β-D-glucopyranoside. The photobromination of penta-O-acetyl-β-D-glucopyranose, followed by hydro- lysis and treatment with methanol, gave a hemiacetal that was converted via treatment with diethylaminosulfur trifluoride followed by protecting group removal into methyl 5-fluoro-β-D-glucopyranoside. Methyl 2,3,4-tri-O-benzyl-6-deoxy-α- and -β-D-xylo-hex-5-enosides were converted into their corresponding epoxides with either dimethyldioxirane or 3-chloroperbenzoic acid; subsequent treatment with hydrogen fluoride/pyridine then generated the 5-fluoro glycopyranosides as the major products. A single-crystal X-ray structure determination of 1,6-anhydro-2,3,4-tri-O-benzyl-5-hydroxy-β-L-idose is presented.