1

Sugar derivatives

There are many important compounds that are derived from monosaccharides. They include acids, sugar alcohols, deoxy and amino sugars

1- Sugar acids

They are the oxidation products of monosaccharides. According to the site of oxidation sugar acids are classified into:

a- Aldonic acids

It is produced by oxidation of (C1 in ) to carboxylic group e.g. gluconic acid from .

H C O COOH H C OH H C OH HO C H HO C H H C OH H C OH H C OH H C OH

CH2 OH CH2 OH Glucose Gluconic acid b- Uronic acids

It is produced by oxidation of the last carbon e.g. glucuronic acid from glucose.

H C O H C O H C OH H C OH HO C H HO C H H C OH H C OH H C OH H C OH

CH2 OH COOH Glucose Glucuronic acid

2

Glucunonic acid is important in:

- Detoxication reactions

- Biosynthesis of mucopolysaccharides

- Metabolism of bilirubin

- Excretion of steroids.

c- Aldaric acid (Saccharic acid)

It is a dicarboxylic acid resulting from oxidation of both carbonyl carbon and last carbon e.g. glucaric acid from glucose.

H C O COOH H C OH H C OH HO C H HO C H H C OH H C OH H C OH H C OH

CH2 OH COOH Glucose Saccharic acid d- L-Ascorbic acid (vitamin C)

It is a water soluble vitamin. It is a 6-carbon derived from glonic acid.

2- Sugar alcohols

Aldoses and Ketoses may be reduced at the carbonyl carbon to the corresponding sugar alcohols

D-Sorbitol from D-glucose

D-mannitol from D-mannose

D-ribitol from D-ribose

Inositol is a cyclic alcohol derived from glucose.

OH OH H H H H H H OH OH OH OH

3

It is a member of vitamin B complex that acts as a lipotropic factor preventing accumulation of fats in the liver

Also, inositol triphosphate has a role in the mechanism of action of some hormones.

3- Deoxysugars

These are monosaccharides with one hydroxyl group (usually at C2) is replaced by hydrogen e.g. 2-deoxyribose which is a constituent of DNA.

4- Amino sugars

These are monosaccharides in which the hydroxyl group at C2 is replaced by amino group.

Glucosamine and galactosamine are examples of amino sugars.

H C O H C O

H C OH H C NH2 HO C H HO C H H C OH H C OH H C OH H C OH

CH2 OH CH2 OH Glucose Glucosamine Amino sugars are important for biosynthesis of mucopolysaccharides and glycoproteins.

Glucosamine which is derived from glucose is a constituent of heparin and hyaluronic acid

Galactosamine which is derived from is a constituent of chondriotin sulphate.