Novel reversed cyclonucleoside analogues with a D-ribofuranose glycone

Two novel ribofuranose cyclonucleoside analogues have been synthesised by a route using 5-azido-5-deoxy-1,2-O-isopropylidene-alpha-D-ribofuranose as the starting material. This derivative was converted into two azole-reversed nucleosides, which were cyclised regiospecifically and stereospecifically by formation of a pentofuranosylamine. An alternative route, starting from a methyl beta-D-ribofuranoside, was much less efficient, reflecting the need for the correct anomeric configuration in the cyclisation step. (C) 1999 Elsevier Science Ltd. All rights reserved.