Syntheses of branched non-1-ynitols by chemoselective addition of (trimethylsilyl)-propargylmagnesium bromide at the anomeric center of side chain halogeno functionalized carbohydrates

A convenient method for the syntheses of non-1-ynitols 8a-8d, by chemoselective addition of (trimethylsilyl)-propargylmagnesium bromide at the anomeric center of a 1-unprotected sugar, in the presence of 3-C′-halide and 3-C′-silyl functions in the side chain is described. In addition, an efficient method for the synthesis of 3-C′-hydroxymethyl sugar 3 via the addition of C1 silyl Grignard reagents to ulose 1 and subsequent oxidation by the Fleming-Tamao method in excellent yields is reported. Also, a suitable acid-catalyzed isomerization of the 1,2-O-isopropylidene group to the 2,3-O-isopropylidene group (5a-5f), to get access to the anomeric center, in good to excellent yields has been depicted.