Some intramolecular rearrangements when pentofuranoses are treated with diethylaminosulphur trifluoride (DAST)

Article abstract of DOI:10.1016/S0022-1139(00)80038-X

Treatment of methyl 2,3-O-isopropylidene-β-D-ribofuranoside with DAST gave a good yield of 2,3-O-isopropylidene-5-O-methyl-β-D-ribofuranosyl fluoride in which the methoxy group had migrated from C-1 -> C-5 and been replaced with retention of configuration by fluorine.The corresponding aldehyde when treated under similar conditions underwent a similar migration to give 5-deoxy-5-fluoro-2,3-O-isopropylidene-5-O-methyl-β-D-ribofuranosyl fluoride.A similar migration occurred with methyl 2',3'-di-O-acetyl-β-D-ribofuranoside and with acetyl 2,3-O-isopropylidene-D-ribofuranose but not with 1,2,3-tri-O-acetyl-D-ribofuranose.Thus the migration depends upon the migratory aptitude of the substituent at C-1 and the conformation of the furanose ring.Two ribofuranosyl fluorides were used as starting materials from which to make nucleosides by the method of Noyori and Hayoshi.