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Furanose ring is stable in Ketohexoses like Fructose. It is one of the cyclic structures in Carbohydrates. Furanose ring is seen in case of Aldopentoses like...
Some of the mono saccharides can occur in either of two structural configurations: open-chain and cyclic (or ringed). Cyclic forms that contain a six-member ring are called pyranoses and those that contain a five-member ring are called furanoses.
Fructose forms a pentagon-shaped ring called a furanose ring, so instead of our previous base molecule, draw a pentagon with an oxygen atom inserted at the top of the shape. Now starting to the right of the oxygen atom and going clockwise, label the carbon atoms 2 through 5.
For example, ribose, an important aldopentose, commonly adopts a furanose structure, as shown in the following illustration. By convention for the D-family, the five-membered furanose ring is drawn in an edgewise projection with the ring oxygen positioned away from the viewer.
Cyclic structures of this kind are termed furanose (five-membered) or pyranose (six-membered), reflecting the ring size relationship to the common heterocyclic compounds furan and pyran shown below.
Pyranose and furanose ring structures of α-D-glucose. Since pentoses and hexoses form rings, the linear Fischer projection is best replaced by the Haworth representation, which also takes in account the anomerism of carbohydrates.
13 lip 2017 · Each isomer (alpha+ beta furanose, alpha + beta pyranose) has a unique three-dimensional structure and the most favored structure will be that which maximizes the strength of the inter- and intramolecular hydrogen bonds.
