Peracetylated α-D-glucopyranosyl fluoride and Peracetylated α-maltosyl fluoride

The X-ray analyses of 2,3,4,6-tetra-O-acetyl-[alpha]-D-glucopyran­osyl fluoride, C14H19FO9, (I), and the corresponding maltose derivative 2,3,4,6-tetra-O-acetyl-[alpha]-D-glucopyranosyl-(1[rightwards arrow]4)-2,3,6-tri-O-acetyl-[alpha]-D-glucopyran­osyl fluoride, C26H35FO17, (II), are reported. These add to the series of published [alpha]-glyco­syl halide structures; those of the peracetyl­ated [alpha]-glucosyl chloride [James & Hall (1969). Acta Cryst. A25, S196] and bromide [Takai, Watanabe, Hayashi & Watanabe (1976). Bull. Fac. Eng. Hokkaido Univ. 79, 101-109] have been reported already. In our structures, which have been determined at 140 K, the glycopyranosyl ring appears in a regular 4C1 chair conformation with all the substituents, except for the anomeric fluoride (which adopts an axial orientation), in equatorial positions. The observed bond lengths are consistent with a strong anomeric effect, viz. the C1-O5 (carbohydrate numbering) bond lengths are 1.381 (2) and 1.381 (3) Å in (I) and (II), respectively, both significantly shorter than the C5-O5 bond lengths, viz. 1.448 (2) Å in (I) and 1.444 (3) Å in (II).