Carbohydrate Structure and Stereochemistry

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Lecture 14

• Carbohydrate Structure and Stereochemistry

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Carbohydrate Structure
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Stereoisomers of Sugars
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Aldoses
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Some Common Monosaccharides
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Epimers

• Differ in configuration at only one carbon

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Cyclic Forms of Sugars
Hemiacetal
O
OH
C
H

C
H
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Cyclic Forms of Monosaccharides
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Haworth Projections
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Chair forms of glucose
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Oxidation of Sugars
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Glycosides Di- and Polysaccharides
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Nomenclature of Di-, Polysaccharides

• 1. Put non-reducing end to left
• 2. Name as derivative of sugar at right
  (reducing) end
• 3. Describe glycosidic bond(s)

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Determining linkages
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Determining linkages
By determining position of unmethylated OH
groups, deduce that bond was 1?4
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Carbohydrate Analysis

• Composition
• 1. Strong acid hydrolysis
• 2. Make volatile derivatives
• 3. Separate by GC
• Structure
• 1. Linkages (sequence)
• 2. Stereochemistry

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Polysaccharides

• Homopolysaccharide
• Glycogen ?(1?4)Glucose (and branches)
• Starch ?(1?4)Glucose (and branches)
• Cellulose ?(1?4)Glucose
• Chitin ?(1?4)GlcNAc

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Glycogen Branching
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Glycogen Structure
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Starch
Garrett and Grisham. Biochemistry. 1995
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Cellulose
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Cellulose