Haworth pyranose forms

Haworth formulas are satisfactory for representing configurational relationships in pyranose forms but are uninformative as to carbohydrate conformations X ray crystal lographic studies of a large number of carbohydrates reveal that the six membered pyra nose ring of D glucose adopts a chair conformation... 

Haworth formulas (Section 25 6) Planar representations of furanose and pyranose forms of carbohydrates... 

The orientation of the model described above results in a clockwise numbering of the ring atoms. Groups that appear to the right of the modified Fischer projection appear below the plane of the ring those on the left appear above. In the common Haworth representation of the pyranose form of D-aldohexoses, C-6 is above the plane. 

FIGURE 7-7 Pyranoses and furanoses. The pyranose forms of o-glucose and the furanose forms of o-fructose are shown here as Haworth perspective formulas. The edges of the ring nearest the reader are represented by bold lines. Hydroxyl groups below the plane of the ring in these Haworth perspectives would appear at the right side of a Fischer projection (compare with Fig. 7-6). Pyran and furan are shown for comparison. 

Figure 9.7 Structures of some sugars. (A) L-Fucose (pyranose form). Note that the -CH3 group points downward this indicates l series in the Haworth structural convention. (B) Maltose (a-D-glucopyranosyl-l,4-D-glucopyranose) (C) cellobiose (/3-D-glucopyranosyl-1,4-D-glycopyranose) and (D) sucrose (a-D-glucopyranosyl-l,2-/3-D-fructofuranoside). (Reproduced by permission from Diem K, Lentner C. Scientific Tables. Basel Ciba-Geigy, 1971.)...

Like aldopentoses, aldohexoses such as D-glucose are capable of forming two fura-nose forms (a and (3) and two pyranose forms (a and (3). The Haworth representations of the pyranose forms of D-glucose are constructed as shown in Figure 25.4 each has a CH2OH group as a substituent on the six-membered ring. 

Fischer projection formulas, 973-974, 1007 furanose forms, 978-981, 1007 glycolysis, 1002-1004, 1015 glycoproteins, 995—996 glycosides, 988-991, 1008 Haworth formulas, 980 ketoses, 973, 986-987 mutarotation in, 985—986, 1008 photosynthesis, 976, 1015 polysaccharides, 993-995, 1008 pyranose forms, 981-984, 1007 reactions of... 

Haworth formulas are satisfactory for representing configurational relationships in pyranose forms but are uninformative as to carbohydrate conformations. X-ray... 

Solutions of aldoses at equilibrium contain mixtures of at least two (a and 3) furanoses and two (a and 3) pyranoses. Typically, the two pyranose forms predominate at equilibrium. The anomeric carbon is chiral (C-1 of aldoses and C-2 of ketoses). In the D-series, if the OH on the anomeric carbon is to the right in a Fischer projection or below the plane of a Haworth perspective formula, the isomer is a and it is 3 if the OH is to the left or above. Conversely, in the L-series, the a anomer has the OH at carbon 1 to the left or... 

Haworth projection (Section 25.2A) A way to view furanose and pyranose forms of monosaccharides. The ring is drawn flat and most commonly viewed through its edge with the anomeric carbon on the right and the oxygen atom of the ring to the rear. 

Mutarotation causes the conversion of (3-D-mannopyranose to a-D-mannopyranose. Using Haworth projections, draw the equilibrium between the two pyranose forms and the open-chain form of D-mannose. 

Draw a Haworth projection showing the a-pyranose form of the D-aldohexose that is epimeric with D-glucose at C3. 

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