8.1 The Fischer projection is used to depict the acyclic forms of monosaccharides: the chain is shown vertically with carbon-1 on top and the horizontal bonds from carbon-2 to the penultimate carbon atom are assumed to be oriented towards the observer. This representation may be simplified by omitting the letter “C” in the central chain. The formulae are sometimes set out horizontally: they are then turned 90° clockwise, so that carbon-1 is on the right. Since such a representation is no longer a true Fischer projection, the vertical bonds should be shown as wedges to avoid any ambiguity:

8.2 The Haworth representation is preferably used to show the cyclic forms of monosaccharides, and not those with “chair-shaped” rings. In a pyranose ring, the oxygen is in the upper right-hand corner; in a furanose ring, the oxygen is at the top in the centre. If the configuration of the anomeric carbon is not specified, a wavy line is used. In practice, the conventional Haworth representation is simplified; the lower side of the ring, assumed to be nearer to the observer, is not thickened, and the hydrogen atoms linked to the carbon atoms in the ring are not shown:

Haworth representation of α-D-glucopyranose (conventional)

Haworth representation of α-D-glucopyranose (simplified)

α-D-ribofuranose

D-idopyranose

8.3 The non-cyclic part of a saccharide is shown as a Fischer projection (wedges are not necessary):

α-D-glucofuranose

lactitol

8.4 The standard conventions are used to show the oligo- and polysaccharides:

saccharose

sizofiran

8.5 In structures that are only partly saccharide, that part is shown in accordance with the standard provisions for carbohydrates, and the rest of the structure according to the conventions for acyclic or cyclic chemical compounds, or for compounds such as steroids, polypeptides, etc.:

rutoside

cytarabine

adenosine

ouabain

α-xylopyranosyl-L-serine