REGIOSELECTIVE INTRODUCTION OF 2-PROPYNYL GROUPS INTO THE C-2 OR C-3 POSITION OF FURANOSIDE RING

The reaction of methyl 2,3-anhydro-alpha-D-ribofuranoside or methyl hy dro-5,6-O-cyclohexylidene-alpha-D-allofuranoside with 2-propynyl metal lic reagents exclusively gave the corresponding 2-C-(2-propynyl)-arabi no-pentofuranosides and 2-C-(2-propynyl)-altro-hexofuranosides, respec tively. In contrast, the beta-anomers were selectively attacked at the position 3 to afford the corresponding 3-C-(2-propynyl)furanosides.