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Sugar derivatives
There are many important compounds that are derived from
monosaccharides. They include sugar acids, sugar alcohols, deoxy sugars
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 carbonyl group (C1 in aldoses) to carboxylic
group e.g. gluconic acid from glucose.
H C O
H C OH
HO C H
COOH
H C OH
HO C H
H C OH
H C OH
H C OH
H C OH
CH2 OH
Glucose
CH2 OH
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 OH
HO C H
H C O
H C OH
HO C H
H C OH
H C OH
H C OH
H C OH
CH2 OH
Glucose
COOH
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
H C OH
HO C H
COOH
H C OH
HO C H
H C OH
H C OH
H C OH
H C OH
CH2 OH
Glucose
COOH
Saccharic acid
d- L-Ascorbic acid (vitamin C)
It is a water soluble vitamin. It is a 6-carbon sugar acid 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
H
H
H
OH
OH
OH
H
H
H 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 OH
HO C H
H C O
H C NH2
HO C H
H C OH
H C OH
H C OH
H C OH
CH2 OH
Glucose
CH2 OH
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 galactose is a constituent of
chondriotin sulphate.