What are Carbohydrates? A Few Common Carbohydrates

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What are Carbohydrates?
• Polyhydroxylated aldehydes and ketones
• Commonly called sugars
• General formula of common sugars
 Glucose:
 Glyceraldehyde:
C6(H2O)6
C3(H2O)3
Talking points:
• ACS Division of Carbohydrate Chemistry
• Understanding carbohydrate coating of a bacterium
leads to how antibodies and antibiotics work
A Few Common Carbohydrates
H OH
H O
H3C
O
H3C
O
O
O
HO
O
H
HO
H
OH
OH
H
OSO2NH2
CH3
CH3
2,3:4,5-bis-O-(1-methylethylidene)β-D-Fructopyranose sulfamate
Glucose
Topiramate (Topamax®)
H OH
Cl OH
H O
H O
HO
H
HO
H
OH
H
O
H
H
CH2OH
OH
H
HO
O
H
H
OH
H
O
CH2Cl
OH
O
HO
Glucose
H
H
Glucose
HO
H
HOH2C
Fructose
Sucrose
H
CH2Cl
Fructose
Sucralose (Splenda)
Aldoses and Ketoses
HO
HO
H
H
CHO
H
H
OH
OH
CH2OH
D-mannose
CH2OH
O
HO
H
H
OH
H
OH
CH2OH
D-mannoketose
triose:
tetrose:
pentose:
hexose:
Glyceraldehyde
CHO
H
OH
CH2OH
CHO
H
OH
CH2OH
CHO
HO
H
CH2OH
CHO
HO
H
CH2OH
1
2
3
4
(R)-2,3-dihydroxypropanal
D-(+)-glyceraldehyde
(S)-2,3-dihydroxypropanal
L-(–)-glyceraldehyde
• Structures 2 and 3 are drawn in the original Fisher projection
• Structures 1 and 4 are drawn in the Victor-Meyer modification
--Now commonly called the Fisher Projection
The D and L designations
and L signify the relationship of a particular
sugar to glyceraldehyde
• They do not designate the optical rotation of the
sugar
• Optical Rotation is designated by the lowercase
letters. i.e.
 d or (+) for dextrorotary
 l or (–) for levorotary
•
D
Examples:
CHO
H
OH
CH2OH
D-(+)-glyceraldehyde
CO2H
H
OH
CH2OH
D-(–)-lactic
acid
CHO
CHOH
CHOH
H
OH
CH2OH
*
A D-pentose
CHO
CHOH
CHOH
HO
H
CH2OH
*
An L-pentose
Drawing Fisher Projections of
Monosaccharides
1. Draw aldehyde or ketone carbon at the top
2. Number from top to bottom
3. The asymmetric carbon of highest number
is used to designate D or L
CHO
H
OH
HO
H
H
OH
H
OH
CH2OH
D-glucose
Some Terms
MethylolAbsolute configurationNumber of stereoisomersEnantiomersDiastereomersEpimersAnomers-
Types of Saccharides
Monosaccharides-
Disaccharides-
Oligosaccharides-
Polysaccharides-
The Family of D-Aldoses
H
H
H
CHO
OH
OH
OH
CH2OH
D-(–)-Ribose
HO
H
H
CHO
H
OH
OH
CH2OH
D-(–)-Arabinose
H
HO
H
CHO
OH
H
OH
CH2OH
D-(+)-Xylose
CHO
H
OH
H
OH
CH2OH
HO
HO
H
CHO
H
H
OH
CH2OH
D-(–)-Lyxose
HO
H
D-(–)-Erythrose
CHO
H
OH
CH2OH
D-(–)-Threose
H
CHO
OH
CH2OH
D-(+)-Glyceraldehyde
H
H
H
H
CHO
OH
OH
OH
OH
CH2OH
D-(+)-Allose
HO
H
H
H
CHO
H
OH
OH
OH
CH2OH
D-(+)-Altrose
H
H
H
H
HO
H
H
CHO
OH
H
OH
OH
CH2OH
D-(+)-Glucose
CHO
H
H
OH
OH
CH2OH
HO
HO
H
H
D-(+)-Mannose
CHO
OH
OH
OH
CH2OH
HO
H
H
D-(–)-Ribose
H
H
HO
H
CHO
OH
OH
H
OH
CH2OH
D-(–)-Gulose
CHO
H
OH
OH
CH2OH
H
HO
H
D-(–)-Arabinose
H
H
CHO
OH
OH
CH2OH
HO
H
HO
H
CHO
H
OH
H
OH
CH2OH
D-(+)-Idose
H
HO
HO
H
HO
HO
HO
H
HO
HO
H
D-(+)-Xylose
CHO
H
H
H
OH
CH2OH
D-(+)-Talose
D-(+)-Galactose
CHO
OH
H
OH
CH2OH
CHO
H
H
OH
CH2OH
D-(–)-Lyxose
The family of D-aldoses
D-(–)-Erythrose
CHO
OH
H
H
OH
CH2OH
HO
H
CHO
H
OH
CH2OH
D-(–)-Threose
H
CHO
OH
CH2OH
D-(+)-Glyceraldehyde
Cyclic Forms of Carbohydrates
pyranoses
O
H
H
H
H
H
OH
OH
OH
OH
CH2OH
H OH
HO
Mixture of stereoisomers
HO
H
OH OH
H
OH
This is NOT a CH2
D-allose
OH
H
H
H
H
H
H
H OH
OH
OH
OH
O
CH2OH
HO
HO
H
H
H
OH
OH
OH
HO
H
H
H
H
OH
OH
OH
O
CH2OH
D-allopyranose
H
HO
OH
HO
OH
H
H
OH
OH
H
This is NOT a CH2
Cyclic Forms of Carbohydrates
furanoses and “special” Fisher projections
S
OH
O
H
H
H
H
H
H
H
H
H
H
OH
OH
OH
OH
CH2OH
H
H
H
H
H
OH
OH
O
OH
CH2OH
D-allose
H
OH
HO H
HOHO
HO
H
H
OH
CH2OH
HO
H
H
H
H
OH
OH
O
OH
CH2OH
H
OH O
OH
HO
HOHO
H
OH
H
OH
OH
CH2OH
H
H
HO
OH
H
OH
OH
OH
OH CH2OH
HO
HO
H
H
O
O
H
H
OH
CH2OH
OH
HOH2C
H
O
OH CH2OH
H
OH
OH
OH
HOCH2
O
OH
H
H
OH
Haworth
Projection
Haworth Formulas
HO
H
H
H
OH
HO H
D-allofuranose
H
O
H
HO
OH
OH
H
OH
H
R
H
HO
H
H
H
H
OH
OH O
OH
OH
O
H
HO OH
H
CH2OH
Fisher-->pyranose form
HO
HO
HO
H
CHO
H
H
H
OH
CH2OH
O
HO
HO
HO
HOH2C
H
CHO
H
H
H
H
OH
HO OH
HO O
H
HO
H
H
H
OH
D-talose
D-Fructose
Cyclic Isomers
OH
*
O
β-D-fructopyranose
60%
HOCH2
OH
O
HO
O
OH CH2OH
HO
HO
H
CH2OH
*
OH CH2OH
β-D-fructofuranose
2%
OH OH
HO
HO
CH2OH
O
HO
H
H
OH
H
OH
CH2OH
*
α-D-fructopyranose
8%
HOCH2
CH2OH
O
H
HO
*
OH OH
α-D-fructofuranose
30%
Mutarotation
A change in specific rotation that accompanies the equilibrium of α- and β-anomers.
H
OH
H
H O
HO
HO
H
H O
keq
HO
HO
H
H
OH
OH
OH
OH
H
H
OH
H
α-D-(+)-Glucose
β-D-(+)-Glucose
[α]D +112
[α]D +18.7
At equilibrium [α]D +52.7
64% of β, 36% of α and 0.003% of the open chain form
Mechanism of Mutarotation
OH
H
H+
H
H O
HO
HO
H
H
H
OH
HO
OH
H
H
H O
HO
HO
H
H
H
OH
HO
OH
H OH
HO
HO
H
H
OH
O
H
H
H
OH
H
H O
HO
HO
OH
H
H
OH
H
OH
H
H
H O
HO
HO
OH
H
H
OH
H
OH
H
H OH
HO
HO
O
H
H
OH
H
Reactions of Carbohydrates
• Glycoside formation/hydrolysis
• Ether formation (Ag2O/CH3I)
• Acetonide formation
• Ester formation (Ac2O, AcCl & pyridine)
• Reduction (NaBH4)
• Reducing/non-reducing sugers
• Methods of oxidation
• Silver oxide/ammonia (Tollens)
• Bromine/water
• Copper sulfate (Benedicts & Fehlings rgts)
• HNO3
• Periodic Acid/oxidative cleavage
• Kilani-Fisher Synthesis
Glycoside Formation/Hydrolysis
H
OH
H O
HO
HO
H
H
H
OH
H
OH
OR'
H
H O
HO
HO
H
H
H+
H O
HO
HO
OH
O
H R'
H
H
O
H
OH
H O
HO
HO
H
OH
O
R"
H
OH
H
H
H
:B
:B
H O
HO
HO
OH
H
H O
HO
HO
H
H
H
OH
OR"
H
O
OH
H
H
H
H
OH
H
R"
H
R"
H
H
O
OH
R"
OH
H O
HO
HO
OR"
H
H
OH
H
Glycoside Parts
Ether Formation
Acetonide Formation
Ester Formation
A reaction with an acid anhydride or acid chloride in the
presence of a weak base leads to ester formation
Reduction
H
H
H
CHO
OH
OH
OH
CH2OH
water workup
H
OH
CH2OH
OH
OH
OH
CH2OH
mirror plane
ribitol/adonitol
($4/gram)
D-ribose
CH2OH
O
H
H
H
H
NaBH4 then
OH
H
H
OH
β-D-ribosfuranose
Oxidation
CHO
H
HO
H
HO
H
H
CO2H
OH
OH
CH2OH
galactose
H
Br2, H2O
OH
HO
H
HO
H
H
O
HO
HO
H OH
O
OH
CH2OH
galactonic acid
D-(–)-galactonic
γ-lactone
OH
acid
Reducing & Nonreducing sugars
H OH
H OH
H
HO
HO
H
O
HO
HO
H
H
H
OH
H
H
OH
H
OH
Oi-Pr
H OH
OH
H
HO
O
H
O
H
OH
H
H
HO
H OH
HO
H O H
O
H
H O
H
OH
H
O
OH
OH
H
OH
H
Oxidation
OH
OH
HO
OH
O
OH
O
HO
OH
O
HO
O
OH
O
OH
OH
Ag2O, NH4OH
Ag
Tollen's
Oxidation
OH
OH
HO
OH
O
OH
O
HO
OH
O
HO
O
OH
CuSO4
Cu2O
Fehling's or
Bendict's reagent
O
OH
OH
Fehling's solution is prepared from solutions of copper(II)
sulfate, Rochelle salt (potassium sodium tartrate tetrahydrate),
and NaOH
Benedict's reagent is prepared from sodium carbonate, sodium
citrate and copper(II) sulfate.
HNO3 Oxidation (Aldaric Acids)
Under vigorous conditions a dicarboxylic acid called an aldaric acid is formed
Periodic Acid
Aqueous periodic acid oxidatively cleaves 1,2-diols to give
aldehydes, ketones, or acids
Oxidative Cleavage
Kilani-Fisher Synthesis
DNA/RNA
NH2
NH2
N
N
O
O
N
adenine
adenine
PO
N
O
O
N
O
O
N
PO
N
N
NH2
NH2
O
O
N
cytosine
cytosine
O
OH
N
PO
N
O
O
N
O
O
O
O
O
PO
O
O
O
O
O
N
NH
guanine
O
N
O
N
NH2
NH
guanine
PO
PO
O
N
OH
N
O
O
N
NH2
O
O
O
O
NH
O
thymine
PO
N
O
O
O
O
NH
OH
uracil
PO
N
O
O
O
O
O
OH
See Smith page 1064
DNA: Hydrogen Bonding
See Smith page 1064
Sucrose: A Disaccharide
H OH
H O
α-glucosidic
linkage
HO
H
HO
H
H
OH
O
H
β-fructosidic
linkage
CH2OH
OH
O
Glucose
HO
H
HOH2C
Fructose
H
Lactose
Lactose, or milk sugar, constitutes more than 1/3 of the solid
residue remaining upon evaporation of milk.
The linkage between glucose and galactose is β. Crystallization
from water furnishes only the α anomer.
Disaccharides (of Glucose)
•
Maltose
 Maltose is the disaccharide of D-glucose having an α-linkage
 Maltose results from hydrolysis of starch by the enzyme diastase
• The two glucose units of maltose are joined by an α-glucosidic
linkage
•
Cellobiose
• Cellobiose is the disaccharide of D-glucose having a β-linkage
Polysaccarides
 The storage form of glucose in plants is called starch. The two forms of
starch are amylose (20%) and amylopectin (80%)
 Amylose consists typically of more than 1000 D-glucopyranoside units
connected by a linkages between C1 of one unit and C4 of the next
 Amylose adopts a very compact helical arrangement
Amylopectin
 Similar to amylose but has branching
points every 20-25 glucose units
 Branches occur between C1 of one
glucose unit and C6 of another
Glycogen (animal starch)
Branches ~10 units
Glycogen is a very large polysaccharide
 The large size of glycogen prevents if from leaving the storage cell
 The storage of tens of thousands of glucose molecules into one molecule
greatly relieves the osmotic problem for the storage cell (this would be caused
by the attempted storage of many individual glucose molecules)
 The highly branched nature of glycogen allows hydrolytic enzymes to have
many chain ends from which glucose molecules can be hydrolyzed
Cellulose
• In cellulose, glucose units are joined by β-1,4’-glycosidic linkages
• Cellulose chains are relatively straight
• The linear chains of cellulose hydrogen bond with each other to give the rigid, insoluble
fibers found in plant cell walls
 The resulting sheets then stack on top of each other
• Humans lack enzymes to cleave the β linkages in cellulose and so cannot use cellulose as
OH
OH
O
O
HO
H
OH
O
O
OH
O
O
O
HOH2C
O
H
Cellulose: makes up 90% of cotton and 50% of wood
O
OH
Chitin
Acidic Mammalian chitinase is a key player in acute inflammation pathway of Asthma
Science, 2004, 304, 1678.
Lufenuron vs. Chitin
Cl
O
F
O
O
CF3
F
N
H
F
N
H
Cl
F
F
lufenuron (active ingredient in Program)
Interferes with the production of chitin
Glycolipids and Glycoproteins
• Glycolipids and Glycoproteins are important for cell
signaling and recognition
• A, B, and O human blood groups are determined by
glycoprotein antigens designated A, B, and H
HO OH
O
OR
HO
O
H3C
O
H
OH
HO
OH
Type O Determinate:
α-fucopyranose --> β-galactopyranose
HO OH
O
OR
HO
O
HO OH
O
H3C
O
HO
H3C
O
NH
O
O
NH P
P
O
O
O
O
O
O
O
OH
N
HO OH
H
OH
HO
HO
O
O
O
OH
OH
OH
NH
O
O
O P O P O
O
O
O
Type O Determinate:
α-fucopyranose --> β-galactopyranose
Uridine diphosphate galactose N-Acetyl
(UDP-GalNAc)+ glycosyltransferase A (GTA)
OH
N
OH
Uridine diphosphate galactose (UDPGal)+ glycosyltransferase B (GTB)
HO OH
O
HO OH
HO
HO OH
O
NH
O
OR
O
H3C
O
O
HO OH
HO
O
OH
H3C
O
O
OR
O
H
OH
O
HO
H3C
OH
Type A Determinate:
α-galactopyranose N-acetyl --> β-galactopyranose
--> α-fucopyranose
GTA and GTB differ by only 4 amino acids
+/– blood is a result of the Rh factor agglutinogens
O
H
OH
HO
OH
JCE, 2005, 82 (12), 1846
Type B Determinate:
α-galactopyranose --> β-galactopyranose -->
α-fucopyranose
Gentamicin
an amino sugar antibiotic
H3C
H
N
purpurosamine
O
NH2
2-deoxystreptamine
H2N
NH2
O HO
O
garosamine
HO
O
Biochem/physiol
Mode of Action: Inhibits protein synthesis by binding to L6
protein of 50S ribosomal subunit.
Antimicrobial spectrum: Gram-negative and Gram-positive
bacteria, and mycoplasma.
CH3
NH
CH3
OH
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