Two novel ribofuranose cyclonucleoside analogues have been synthesised by a
route using 5-azido-5-deoxy-1,2-O-isopropylidene-alpha-D-ribofuranose as t
he 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 nee
d for the correct anomeric configuration in the cyclisation step. (C) 1999
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