Kiliani synthesis of aldonic acids

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Kiliani synthesis of aldonic acids
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Kiliani synthesis

• Kiliani synthesis on Arabinose gives
• Glucose and Mannose

Mannose and Glucose differ only at C-2
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Phenylhydrazone Formation
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Osazone of Glucose and Mannose
Reaction of glucose and mannose with
phenylhydrazine produced the same osazone thus,
glucose and mannose differ only at C-2. They are
identical in configuration at C-3, C-4 and C-5.   
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Question 9

• Which of the following D-aldohexoses would give
  the same Osazone products.

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The Third Elimination

• Eliminate the aldohexoses that have the same
  osazone as those already eliminated.

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Nitric acid Oxidation of Arabinose
Produces an optically active glycaric
acid. Specifies the configuration of C-3 relative
to C-5.
(opposite sides)
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Oxidation of Glucose and Mannose

• both products were optically active

given the relative configurations at C-3 and C-5,
the C-4 -OH must be to the right
OH
OH
HO
symmetric
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Question 10

• Which of these two would provide a new sugar when
  the ends were interchanged.

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C2 Epimers and Symmetry
Used to select which was glucose (not mannose)
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Fischer's Reasons

• 1. Osazone formation with glucose and mannose ?
  same osazone
• epimers at C-2
• 2. a) Ruff shortening glucose ? arabinose  
• b) Kiliani-Fischer synthesis on arabinose ?
  glucose mannose.
•  
• 3. a) Ruff degradation Ribose and arabinose ?
  erythrose.
• b) Kiliani-Fischer synthesis on erythrose ?
  ribose arabinose.
•  
• 4. Oxidation of erythrose ? achiral (optically
  inactive) aldaric acid.
•  
• 5. Oxidation of ribose ? achiral (optically
  inactive) aldaric acid.
•  
• 6. Identify Two epimers glucose and mannose.

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Common Modifications to Monosaccharides

• Deoxy sugars
• Amino sugars
• Glycosides (acetal)

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Deoxy Sugar
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Amino Sugar

• Glucosamine

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Formation of Glycosides - Acetals

• Glycoside a carbohydrate in which the -OH of
  the anomeric carbon is replaced by -OR

A monosaccharide hemiacetal can react with a
second molecule of an alcohol to form an acetal
A glycoside bond
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Glycosides

• Glycoside bond the bond from the anomeric
  carbon of the glycoside to an -OR group.

• Unlike cyclic hemiacetals, cyclic acetals are not
  in equilibrium with their open chain
  carbonyl-containing forms.

• Glycosides do NOT undergo mutarotation.

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Naming Glycosides

• List the name of the alkyl or aryl group
  attached to oxygen followed by the name of the
  carbohydrate with the ending -e replaced by -ide
• methyl ?-D-glucopyranoside
• methyl ?-D-ribofuranoside

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Glucopyranoside

• Methyl b-D-glucopyranoside
• (methyl b-D-glucoside)

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Disaccharides
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Disaccharides

• Three naturally occurring glycosidic linkages

• 1-4 link The anomeric carbon is bonded to
  oxygen on C4 of second sugar.

• 1-6 link The anomeric carbon is bonded to
  oxygen on C6 of second sugar.

• 1-1 link The anomeric carbons of the two sugars
  are bonded through an oxygen.

• 3 important Disaccharides
• Maltose, Lactose and Sucrose

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Cellobiose

• Two glucose units linked 1-4.
• Disaccharide of cellulose.
• A mutarotating, reducing sugar.

Is this a reducing sugar?
Yes, Notice the free OH on the end.
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Gentiobiose

• Two glucose units linked 1-6.
• Rare for disaccharides, but commonly seen as
  branch point in carbohydrates.

Is this a reducing sugar?
Yes, Notice the free OH on the end.
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Maltose

• From malt, the juice of sprouted barley and other
  cereal grains.

• What is the full IUPAC name?

4-O-( a-D-glucopyranosyl)-D-glucopyranose
Is this a reducing sugar?
Yes, Notice the free OH on the end.
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Lactose

• The principle sugar present in milk
• 5 - 8 in human milk and 4 - 5 in cows milk

• What is the full IUPAC name?

4-O-( b-D-galactopyranosyl)-D-glucopyranose
Is this a reducing sugar?
Yes, Notice the free OH on the end.
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Sucrose

• Table sugar, from the juice of sugar cane and
  sugar beet

• What is the full IUPAC name?

b-D-fructofuranosyl-a-D-glucopyranoside or a-D-glu
copyranosyl-b-D-fructofuranoside
Is this a reducing sugar?
No, There is no free OH on the anomeric carbon.
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N-Glycosides

• The anomeric carbon of a cyclic hemiacetal
  undergoes reaction with the N-H group of an amine
  to form an N-glycoside
• N-glycosides of the following purine and
  pyrimidine bases are structural units of nucleic
  acids

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Formation of N-Glycosides(Nucleosides)

• For example, reaction between b-D-ribofuranose
  and cytosine produces water and uridine, one of
  the structural units of RNA