Haworth notation

Haworth notation A type of notation used to describe the three-dimensional configuration of a compound. 

Haworth projections are used extensively in the hterature, but here, to make use of our knowledge of conformation (Sections 4-3 and 4-4), the cychc forms of sugars will be presented mostly as envelope (for furanoses) or chair (for pyranoses) conformations (Figures 4-4 and 4-6). As in Haworth notation, the ether oxygen will be placed usually top right and the anomeric carbon at the right vertex of the envelope or chair. 

The variants are distinguished by the locants of those ring atoms that lie outside a reference plane (defined below) and are listed for some examples in Table 1. The locants of ring atoms that lie on the side of the reference plane from which numbering appears clockwise (i.e. the upper side in the normal Haworth representation of furanoses and pyranoses) are written as superscripts and precede the letter those that lie on the other side are written as subscripts and follow the letter. Heteroatoms (e.g. O, S) are indicated by their subscript or superscript atomic symbols. Table 1 gives the notations and Chart III some examples. 

Figure 20-4 Haworth projection formulas showing the formation and reactions of O-methyl derivatives of glucose. The notation (H.OH) in 20 means that the anomeric configuration is unspecified.

Fig. 1. Chemical structures for simple sialic acids in different views, (a) S-amino-S.S-dideoxy-D-gfycero-D-ga/acro-non-2-ulosonic acid (Neu, open chain, Fischer projection formula) (b) 5-acetaraido-3,5-dideoxy-D-g/> cero-a-D-gfl/acto-non-2-ulopyranosonic acid (a-Neu5Ac, Fischer projection formula, note that C7 is the anomeric reference atom) (c) a-Neu5Ac (Haworth projection formula) (d) a-Neu5Ac ( 5 chair conformation) (e) 3-deoxy-D-g/ycero-3-D-gfl/acto-non-2-ulopyranosonic acid (P-Kdn, 5 chair conformation). Note that the D-notation is part of the trivial name.

Representation of the cyclic forms could be simplified by using the special shorthand notation called the Haworth formula (in the honor of Sir Norman Haworth). Fischer formulas can be easily transformed into Haworth formulas by the rules given in the following scheme. 

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