O
O
H
O
N
H 2
O O
H
O
O
H O
H
NH 2
Me
NH 2
NH 2
OH
N
H
Me
Me
Gentamicin
A carbohydrate antibiotic
Purpurosamine
2-Deoxystreptamine
Garosamine
Sulphur-containing carbohydrate
In these sugars, the anomeric –OH group (of common sugars) is replaced by
a sulphur-containing group, e.g. lincomycin.
N
Me
Me
H
OH
O
O
H
OH S
Me
N
Me
OH
H
O
Lincomycin, an antibiotic
Ascorbic acid (vitamin C)
Ascorbic acid, commonly known as vitamin C, is a sugar acid, biosynthesized in plants, and also found in the livers of most vertebrates, except
human beings. Therefore, human beings need an external supply of this
vitamin, mainly from fresh vegetables and fruits. In many pharmaceutical
preparations ascorbic acid is used as an antioxidant preservative. Ascorbic
acid is highly susceptible to oxidation, and oxidized easily to dehydroascorbic acid.
O
OH OH
O
OH
O
H
O
O
OH
O
H
O
O
Ascorbic acid (Vitamin C)
[O
Dehydroascorbic acid
Glycoprotein and glycolipids
Glycoproteins and glycolipids are formed when sugars combine, respectively, with proteins and lipids. Biologically these are important compounds
as they are an integral part of cell membranes. Biological membranes are
composed of proteins, lipids and carbohydrates. The carbohydrates in the
membrane are covalently bonded to proteins (glycoproteins) or with lipids
(glycolipids).
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CH6 NATURAL PRODUCT CHEMISTRY