#Id: 7846

#Unit 1. Molecules and their Interaction Relevant to Biology

When the anomeric hydroxyl of a D-hexose is on the same side of the ring as C-6, the structure is β a by definition; when it is on the opposite side from C-6, the structure is α.

#Id: 7847

#Unit 1. Molecules and their Interaction Relevant to Biology

The two diastereomers of glucose in its "pyranose" form are called the alpha (a) and beta (B) isomers, which differ in the orientation of the OH at C-1

#Id: 7849

#Unit 1. Molecules and their Interaction Relevant to Biology

The pyranose form of glucose dominates (>99%) at equilibrium in aqueous solution

#Id: 7850

#Unit 1. Molecules and their Interaction Relevant to Biology

The 6-membered cyclic form of sugars is usually called the “pyranose” form in reference to the cyclic ether pyran.

#Id: 7852

#Unit 1. Molecules and their Interaction Relevant to Biology

The pyranose forms of the sugars are more stable than the furanose forms in solution.

#Id: 7853

#Unit 1. Molecules and their Interaction Relevant to Biology

Thus, D glucose in aqueous solution exists as an equilibrium mixture of 5 compounds. The pyranose form predominates in solution.

aD glucofuranose (0.5%)

aD-glucopyranose (37%)

aldehydo- -glucose (0.003%)

bD-glucofuranose (0.5%)

bD-glucopyranose (62%)