Chapter 25: Carbohydrates
hydrates of carbon: general formula Cn(H2O)n
Plants: photosynthesis
6 CO2 + 6 H2O
hn
C6H12O6 + 6 O2
Polymers: large molecules made up of repeating smaller units
(monomer)
Biopolymers:
carbohydrates (Chapter 25)
peptides and proteins (Chapter 27)
nucleic acids (Chapter 28)
Monomer units:
monosaccharides
amino acids
nucleotides
246
25.1: Classification of Carbohydrates.
I. Number of carbohydrate units
monosaccharides: one carbohydrate unit
(simple carbohydrates)
disaccharides: two carbohydrate units
(complex carbohydrates)
trisaccharides: three carbohydrate units
polysaccharides: many carbohydrate units
CHO
H
OH
HO
HO
HO
HO
H
H
OH
H
OH
HO
O
HO
HO
HO
O
HO
OH
OH
CH2OH
HO
HO HO
O
HO
HO
O
HO
HO
O
HO
HO
O
HO
HO
O
O
HO
HO
O
HO
O
HO
HO
O
HO
O
HO
HO
OH
O
O
O
247
II. Position of carbonyl group
at C1, carbonyl is an aldehyde: aldose
at any other carbon, carbonyl is a ketone: ketose
III. Number of carbons
three carbons: triose
four carbons: tetrose
five carbons: pentose
six carbons: hexose
seven carbons: heptose
etc.
IV. Cyclic form (chapter 25.6 and 25.7)
CHO
CHO
H
OH
HO
CH2OH
H
CHO
CHO
H
H
OH
H
OH
OH
H
OH
HO
CH2OH
H
OH
H
OH
H
OH
CH2OH
H
OH
H
OH
H
CH2OH
glyceraldehyde
(triose)
CH2OH
threose
(tetrose)
ribose
(pentose)
glucose
(hexose)
(aldohexose)
O
HO
H
CH2OH
fructose
(hexose)
(ketohexose)
248
25.2: Fischer Projections and the D-L Notation. Representation
of a three-dimensional molecule as a flat structure. Tetrahedral
carbon represented by two crossed lines:
horizontal line is coming
out of the plane of the
page (toward you)
vertical line is going back
behind the plane of the
paper (away from you)
substituent
carbon
(R)-(+)-glyceraldehyde
H C
CH2OH
HO
CHO
CHO
CHO
H
OH
H
OH
CH2OH
CH2OH
CHO
CHO
(S)-(-)-glyceraldehyde
CHO
HO C
CH2OH
H
HO
H
CH2OH
HO
H
CH2OH
249
before the R/S convention, stereochemistry was related to (+)-glyceraldehyde
CHO
H
OH
CH2OH
D-glyceraldehyde
R-(+)-glyceraldhyde
(+)-rotation = dextrorotatory = D
CHO
HO
H
CH2OH
L-glyceraldehyde
S-(-)-glyceraldhyde
(-)-rotation = levorotatory = L
D-carbohydrates have the -OH group of the highest numbered
chiral carbon pointing to the right in the Fisher projection as in
R-(+)-glyceraldhyde
For carbohydrates, the convention is to arrange the Fischer
projection with the carbonyl group at the top for aldoses and
closest to the top for ketoses. The carbons are numbered from
top to bottom.
250
Carbohydrates are designated as D- or L- according to the
stereochemistry of the highest numbered chiral carbon of the
Fischer projection. If the hydroxyl group of the highest numbered
chiral carbon is pointing to the right, the sugar is designated as
D (Dextro: Latin for on the right side). If the hydroxyl group is
pointing to the left, the sugar is designated as L (Levo: Latin for
on the left side). Most naturally occurring carbohydrates are of
the D-configuration.
highest numbered
"chiral" carbon
1 CHO
H 2 OH
3
HO
H
H 4
OH
OH
1 CHO
2
H
OH
3
HO
H
4
HO
H
6 CH2OH
5 CH2OH
H 5
D-Glucose
highest numbered
"chiral" carbon
L-Arabinose
CHO
HO
H
highest numbered
"chiral" carbon
CHO
H
OH
HO
H
HO
H
H
OH
HO
H
H
OH
CH2OH
L- glucose
highest numbered
"chiral" carbon
CH2OH
251
D-Arabinose
25.3: The Aldotetroses. Glyceraldehyde is the simplest
carbohydrate (C3, aldotriose, 2,3-dihydroxypropanal). The next
carbohydrate are aldotetroses (C4, 2,3,4-trihydroxybutanal).
aldotriose
CHO
H
OH
CH2OH
D-glyceraldehyde
CHO
HO
H
CH2OH
L-glyceraldehyde
aldotetroses
highest numbered
"chiral" carbon
1 CHO
2
H
OH
3
H
OH
4 CH2OH
D-erythrose
1 CHO
HO 2
H
HO 3
H
4 CH2OH
L-erythrose
CHO
CHO
highest numbered
"chiral" carbon
HO
H
H
OH
CH2OH
D-threose
highest numbered
"chiral" carbon
H
HO
OH
H
highest numbered
"chiral" carbon
CH2OH
L-threose
252
25.4: Aldopentoses and Aldohexoses.
Aldopentoses: C5, three chiral carbons, eight stereoisomers
CHO
H
H
OH
HO
H
OH
H
OH
HO
H
OH
H
OH
H
CH2OH
H
OH
HO
H
H
HO
H
H
OH
D-xylose
D-arabinose
OH
CH2OH
CH2OH
CH2OH
D-ribose
CHO
CHO
CHO
D-lyxose
Aldohexoses: C6, four chiral carbons, sixteen stereoisomers
CHO
CHO
CHO
OH
HO
H
OH
H
OH
HO
H
OH
H
OH
H
OH
H
OH
HO
H
OH
H
OH
H
OH
H
OH
H
D-allose
CH2OH
D-altrose
H
CHO
H
CH2OH
H
CHO
OH
HO
H
H
OH
HO
H
HO
H
H
OH
H
CH2OH
D- glucose
CH2OH
D-mannose
H
OH
CH2OH
D-gulose
CHO
CHO
HO
H
H
H
CHO
OH
HO
H
OH
HO
H
HO
H
H
HO
H
HO
H
OH
CH2OH
D-idose
H
OH
H
OH
CH2OH
CH2OH
D-galactose
D-talose
253
Manipulation of Fischer Projections
1. Fischer projections can be rotate by 180° (in the plane of the
page) only!
CHO
180 °
H
CH2OH
OH
HO
H
CH2OH
CHO
(R)
(R)
CHO
180 °
HO
H
CH2OH
(S)
CH2OH
H
OH
CHO
(S)
180°
180°
Valid
Fischer
projection
Valid
Fischer
projection
254
a 90° rotation inverts the stereochemistry and is illegal!
90 °
OH
CHO
H
OH
CH2OH
(R)
°
OHC
CH2OH
H
(S)
90 °
90°
This is not the correct convention
for Fischer projections
Should be projecting toward you
Should be projecting away you
This is the correct convention
for Fischer projections and is
the enantiomer
255
2. If one group of a Fischer projection is held steady, the other
three groups can be rotated clockwise or counterclockwise.
hold
steady
CHO
H
CHO
OH
HO
CH2OH
CH2OH
H
(R)
(R)
CHO
H
HO
hold
steady
H
OHC
CH2OH
CH2OH
(S)
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
hold
steady
120°
(S)
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
hold
steady
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
120°
hold
steady
OH
120°
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
hold
steady
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
120°
hold
steady
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
hold
steady
256
Assigning R and S Configuration to Fischer Projections
1. Assign priorities to the four substitutents according to the
Cahn-Ingold-Prelog rules
2. Perform the two allowed manipulations of the Fischer projection
to place the lowest priority group at the top or bottom.
3. If the priority of the other groups 123 is clockwise then
assign the carbon as R, if priority of the other groups 123
is counterclockwise then assign the center as S.
2
CO2H
1 H2N
hold steady
rotate other
three groups
counterclockwise
place at
the top
4
H
H 4
2 HO2C
CH3
NH2 1
CH3
3
3
1-2-3 counterclockwise = S
2
4
CO2H
4 H
NH2
CH3
3
H
1
H2N
1
2
CO2H
CH3
3
1-2-3 clockwise = R
2
CO2H
1 H2N
H
4
CH3
3
257
Fischer projections with more than one chiral center:
1 CHO
2
HO
H
3
H
CHO
HO
OH
H
H
4 CH2OH
OH
CH2OH
Threose
2
CHO
1
HO
2
4 H
3
Hold Steady
H4
4
2
OHC
OH
1
3 CH2OH
4 H
H
S
2
3
1
OH
OH 1
CH2OH
3
(2S, 3R)
Hold Steady
H4
H4
2
OHC
4 H
2
3
1
OH
OH 1
CH2OH
3
2
2
OHC
1 HO
S
3
R
H
4
1
OH
CH2OH
3
258
25.5: A Mnemonic for Carbohydrate Configuration.
(please read)
25.6: Cyclic Forms of Carbohydrates: Furanose Forms.
O
H+
+
R1
H
R2OH
HO OR2
R1
H+, R2OH
H
R1
hemiacetal
O
OH
(Ch. 17.8)
H
acetal
OR
OH
H
H
R2O OR2
O
cyclic hemiacetal
H
H+, ROH
Ch. 25.13
O
mixed acetal (glycoside)
259
In the case of carbohydrates, cyclization to the hemiacetal
creates a new chiral center.
* CHO
H
OH
H
OH
CH2OH
H
OH
O
H
H
OH
H
OH
H
*
H
+
H
O
H
H
OH
OH
OH
H
*
D-erythrose
Converting Fischer Projections to Haworth formulas
260
25.7: Cyclic Forms of Carbohydrates: Pyranose Forms.
H
5
H
CHO
H
H
H
H
4
1
2
HO
OH
3
H H H
OH
H
4
OH
H
5
H
HO
5
4
HO
H
O
OH
H
1
H
3
OH
OH
OH
new chiral
center
1
2
3
H
H
4
1
2
3
5
H
O
H
HO
H
H
OH
CHO
H OH OH OH
H
H
5
H
OH
H
H
4
D-ribose
OH
HO
HO
O
H
H
1
2
3
OH
OH
HO
O
H
H
4
1
2
3
H
H
H
5
OH
OH
ribopyranose
6
CH2OH
OH
H
H
4
OH H
HO
2
6
5
1
CHO
H
HO
H
HOH2C
6
2
3
HOH2C H OH H
4
OH
HO
5
H
D-glucose
H
5
4
3
H OH H
2
OH
4
HO
OH
1
H
3
H
OH
H
6
H
OH
1
3
OH
H
O
CH2OH
O
H
H
OH
5
OH
new chiral
center
1
CHO
6 CH
2OH
OH
5
H
4
H
OH
HO
3
H
6
H
H
1
H
2
OH
O
4
HO
CH2OH
O
H
H
OH
5
3
H
H
1
2
OH
OH
glucopyranose
261
25.8: Mutarotation and the Anomeric Effect. The hemiacetal
or hemiketal carbon of the cyclic form of carbohydrates is the
anomeric carbon. Carbohydrate isomers that differ only in the
stereochemistry of the anomeric carbon are called anomers.
Mutarotation: The - and -anomers are in equilibrium, and
interconvert through the open form. The pure anomers can be
isolated by crystallization. When the pure anomers are dissolved
in water they undergo mutarotation, the process by which they
return to an equilibrium mixture of the anomer.
HOH2C
HO
HO
H
HO
H
H
CHO
OH
H
OH
OH
CH2OH
D-glucose
O
HO
H
OH
Trans
HOH2C
H
O
O
-D-Glucopyranose (64%)
(-anomer: C1-OH and
CH2OH are cis)
H
OH
HO
HO
HO
HO
HOH2C
HO
HO
Cis
HOH2C
OH
HO
HO
O
H
HO
OH
-D-Glucopyranose (36%)
(-anomer: C1-OH and
CH2OH are trans)
262
25.9: Ketoses. Ketoses are less common than aldoses
CH2OH
CH2OH
CH2OH
O
CH2OH
O
CH2OH
CH2OH
O
H
OH
H
H
OH
HO
CH2OH
OH
O
HO
H
H
OH
H
OH
H
OH
H
OH
H
OH
HO
H
O
CH2OH
CH2OH
dihydroxyacetone
Dxylulose
D-ribulose
H
CH2OH
D-sedohepuloase
D-fructose
Fructofuranose and Fructopyranose
1
CH2OH
2
HO
3
H
4
HOH2C
5
6
6
O
HOH2C H OH
H
HO
5
4
1
2
3
CH2OH
HOH2C OH
5
H
4
3
2
H
CH2OH
H
HO
4
3
OH
1
OH
O
H
5
HO
OH
H
CH2OH
O
H
O
H OH H
OH
6
6
H
2
CH2OH
1
furanose
OH
1
2
O
HO
3
H
H
4
OH
H
5
OH
6
H
CH2OH
CH2OH
6
6
HOH2C
H H OH
5
4
3
OH OH H
2
O
1
CH2OH
H
5
6
OH
O
H
H
HO
4
HO
HO
2
3
H
CH2OH
1
H
4
HO
H
5
H
H
O
HO
2
CH2OH
3
OH
OH
H
pyranose
1
263
25.10: Deoxy Sugars. Carbohydrates that are missing a
hydroxy group.
1
1
H
2
H
2
H
3
H
3
OH
H
4
H
4
OH
CHO
CHO
OH
OH
HOH2C
H
OH
H
OH
5 CH2OH
O
OH
H
H
OH
1
CHO
6
HO
H
H
3
OH
H
4
OH
4
HO
5
H
HO
CH2OH
L-Galactose
H
OH
O
H
H
H
OH
H
2-Deoxy-D-ribose
2
6
HOH2C
5 CH2OH
D-ribose
1
H
H
H
5
O
OH
CH2OH
HO
H
H
3
OH
2
H
1
CHO
6
HO
2
H
H
3
OH
H
4
OH
4
HO
5
H
HO
6
H
CH3
H
5
O
CH3
H
HO
2
H
3
OH
OH
H
1
6-Deoxy-L-Galactose
(fucose)
264
25.11: Amino Sugars. Carbohydrates in which a hydroxyl
group is replaced with an -NH2 or -NHAc group
HOH2C
HO
HO
HOH2C
O
OH
HN
O
H
N-acetyl-D-glucosamine
(GlcNAc or NAG)
HO2C
HO
O
O
OH
HN
CH3
O
H
N-Acetylmuramic acid
(MurNAc)
25.12: Branched-Chain Sugars. (Please read)
265
25.13: Glycosides. Acetals and ketals of the cyclic form of
carbohydrates.
O
H+
+
R1
H
HO OR2
R2OH
R1
H+, R2OH
R2O OR2
H
R1
hemiacetal
H
HO
H
H
CHO
OH
H
OH
OH
CH2OH
D-glucose
HOH2C
HO
HO
acetal
HOH2C
ROH
O
OH
HO
H
pyranose
(hemiacetal)
H+
HO
HO
H
HOH2C
O
OR
HO
H
+
HO
HO
O
H
HO
Glycoside
(acetals)
OR
Note that only the anomeric hydroxyl group is replaced by ROH
266
25.14: Disaccharides. A glycoside in which ROH is another
carbohydrate unit (complex carbohydrate).
OH
HO
HO
HO
OH
HO
HO
O
H
HO
OH
O
HO
O
HO
H
O
HO
OH
HO
OH
O
HO
OH
O
HO
O
HO
HO
H
OH
HO
HO
HO
O
HO
O
HO
O
OH
OH
HO
sucrose
(1,2'-glycoside)
Lactose
(1,4'--glycoside)
cellobiose
(1,4'--glycoside)
HO
O
OH
maltose
(1,4'--glycoside)
O
OH
25.15: Polysaccharides. Cellulose: glucose polymer made up
of 1,4’--glycoside linkages
HO
HO
O
HO
O
HO
O
HO HO
HO
HO
O
O
HO
O
HO
H
H
O
HO
HO
HO
O
HO
O
HO
O
HO
H
H
O
HO
O
O
HO
H
H
Amylose: glucose polymer made up of 1,4’--glycoside linkages
HO
O
HO HO
O H
HO
O H
O
HO HO
HO
O HO
HO
O
H
HO
O
HO HO
O
H
HO
O HO
HO
O
H
HO
O
HO HO
O
H
O
267
OH
Amylopectin:
O
HO
O
H
OH
HO
O
HO
HO
O H
O
HO HO
O
HO
HO
O H
O
HO HO
HO
O
O
HO HO
H
O
O
HO HO
O
H
HO
H
O
O
HO HO
HO
O
O
HO HO
H
O
25.16: Reactions of Carbohydrates. Glycoside formation is
related to acetal formation.
25.17: Reduction of Monosaccharides. C1 of aldoses are
reduced with sodium borohydride to the 1° alcohol (alditols)
Reacts like
A carbonyl
HOH2C
HO
HO
O
HO
OH
H
HO
H
H
CHO
OH
H
OH
OH
CH2OH
D-glucose
NaBH4
H
HO
H
H
CH2OH
OH
H
OH
OH
CH2OH
D-glucitol
268
Reduction of ketoses
CH2OH
O
HO
CH2OH
CH2OH
H
H
NaBH4
OH
HO
H
H
OH
H
OH
H
OH
H
OH
CH2OH
CH2OH
D-fructose
D-glucitol
HO
H
HO
H
+
H
OH
H
OH
CH2OH
D-mannitol
25.17: Oxidation of Monosaccharides. C1 of aldoses can be
selectively oxidized to the carboxylic acid (aldonic acids) with
Br2 or Ag(I) (Tollen’s test).
CHO
H
OH
HO
CO2H
Ag(I)
H
Ag(0)
H
H
OH
H
OH
HO
NH3,
H2O
CH2OH
OH
H
H
OH
H
OH
CH2OH
aldonic acid
HOH2C
HO
HO
CO2H
HOH2C
Br2
O
HO
OH
HO
HO
H2O
O
HO
O
H
HO
OH
H
H
OH
H
OH
CH2OH
Reducing sugars: carbohydrates that can be oxidized to aldonic
269
acids.
Oxidation of aldoses to aldaric acids with HNO3.
CO2H
CHO
H
HO
H
OH
H
HNO3
HO
OH
H
H
OH
H
OH
H
OH
H
OH
CO2H
CH2OH
Glucaric acid
Uronic Acid: Carbohydrate in which only the terminal -CH2OH is
oxidized to a carboxylic acid.
CHO
CHO
H
HO
H
OH
H
[O]
HO
H
H
OH
H
OH
H
OH
H
OH
CH2OH
HO2C
OH
CO2H
HO
HO
O
HO
OH
Gluronic acid
270
Reducing sugars: carbohydrates that can be oxidized to aldonic
acids.
HO
HO
HO
HO
HO
HO
O
HO
O
HO
HO
HO
HO
O
O
HO
Ag(I)
O
HO
OH
OH
HO
O
HO
1
Ag(I)
HO
HO
O
HO
O
HO
HO
O
HO
[O]
OH
H
HO
OH
reducing
end
lactose
(1,4'--glycoside)
O
HO
+ Ag(0)
OH
OH
HO
O
HO HO
4'
HO
cellobiose and maltose
are reducing sugar
HO HO
O
O
O
reducing
end
HO
H
HO
HO
[O]
HO
HO
HO
HO HO
HO
O
HO
HO
O
HO
+ Ag(0)
OH
OH
HO
O
O
lactose is a
reducing sugar
HO
HO
HO
glucose
O
Ag(I)
HO
HO 1 
O 2' 
[O]
O fructose
OH
HO
sucrose
(1,2'-glycoside)
No reducing end
OH
No reaction
sucrose is not
a reducing sugar
271
25.19: Cyanohydrin Formation and Chain Extension.
Kiliani-Fischer Synthesis- chain lengthening of monosaccharides
272
Determination of carbohydrate stereochemistry
1) HCN
2) H2, Pd/BaSO4
3) H2O
CHO
H
OH
H
OH
HNO3,
heat
CO2H
H
OH
H
OH
CH2OH
CO2H
D-(-)-erythrose
tartaric acid
CHO
H
OH
CH2OH
Killiani-Fischer
synthesis
D-(+)-glyceraldehyde
CHO
HO
H
1) HCN
2) H2, Pd/BaSO4
3) H2O
H
OH
CH2OH
HNO3,
heat
CO2H
HO
H
H
OH
CO2H
D-(-)-threose
D-(-)-tartaric acid
273
1) HCN
CHO
2) H2, Pd/BaSO4
H
OH
3) H2O
H
OH
H
CO2H
HNO3,
heat
OH
H
OH
H
OH
H
OH
CH2OH
CO2H
D-(-)-ribose
ribonic acid
CHO
H
OH
H
OH
Killiani-Fischer
synthesis
CH2OH
D-(-)-erythrose
CHO
HO
1) HCN
2) H2, Pd/BaSO4
3) H2O
H
H
OH
H
OH
CH2OH
D-(-)-arabinose
CO2H
HNO3,
heat
HO
H
H
OH
H
OH
CO2H
arabonic acid
274
1) HCN
2) H2, Pd/BaSO4
3) H2O
CO2H
CHO
H
HO
H
OH
H
HNO3,
heat
H
HO
H
OH
OH
H
OH
CO2H
CH2OH
D-(+)-xylose
xylonic acid
CHO
HO
H
H
OH
Killiani-Fischer
synthesis
CH2OH
D-(-)-threose
CO2H
CHO
1) HCN
2) H2, Pd/BaSO4
3) H2O
HO
H
HO
H
H
OH
CH2OH
D-(-)-lyxose
HNO3,
heat
HO
H
HO
H
H
OH
CO2H
lyxonic acid
275
CHO
CHO
CHO
H
OH
HO
H
OH
H
OH
HO
H
OH
H
OH
H
CH2OH
H
H
CH2OH
D-ribose
CHO
CHO
CHO
HO
H
OH
H
OH
HO
H
OH
H
OH
H
OH
H
OH
HO
H
OH
H
OH
H
OH
H
OH
H
CH2OH
D-altrose
CO2H
OH
CH2OH
D-lyxose
CHO
HO
H
HO
H
H
OH
H
CH2OH
D-mannose
CO2H
H
OH
HO
H
CH2OH
D-gulose
CO2H
OH
H
OH
HO
H
OH
H
OH
H
OH
H
OH
HO
H
OH
H
OH
H
OH
H
OH
H
H
H
OH
HO
H
HO
H
H
OH
H
CO2H
CO2H
optically
active
optically
active
enantiomers
CO2H
optically
active
H
HO
H
CHO
OH
HO
H
OH
HO
H
HO
H
H
HO
H
HO
H
OH
H
OH
H
H
OH
CH2OH
D-galactose
CO2H
HO
OH
H
D-idose
OH
H
CHO
CH2OH
CO2H
H
optically
active
H
OH
HO
optically
inactive
OH
H
OH
CO2H
H
H
D- glucose
H
HO
HO
H
CO2H
H
H
OH
CH2OH
CO2H
H
CHO
OH
D-allose
H
HO
D-xylose
H
CH2OH
H
OH
CH2OH
D-arabinose
CHO
CHO
CH2OH
D-talose
CO2H
H
CO2H
OH
HO
H
OH
HO
H
HO
H
H
HO
H
HO
H
OH
CO2H
optically
active
H
OH
H
CO2H
optically
inactive
OH
CO2H
optically
active
276
25.20: Epimerization, Isomerization and Retro-Aldol Cleavage.
HO ,
H2O
O
C6H5
CH2CH3
OH
C6H5
H CH3
O
HO ,
H2O
CH2CH3
C6H5
H
HO
O
(R)
OH
H
H C
HO ,
H2O
From
Ch 18.10
H3C H
CH3
H C
CH2CH3
OH
OH
HO
H
H
HO ,
H2O
HO
HO
O
C
(S)
H
H
H
OH
H
OH
H
OH
H
OH
H
OH
H
OH
CH2OH
CH2OH
CH2OH
D-mannose
D-glucose
HO ,
H2O
CH2OH
O
HO
H
H
OH
H
OH
Fructose is a reducing sugar
(gives a positive Tollen’s test)
CH2OH
D-fructose
277
Retro-aldol reaction of carbohydrates
CH2OH
CH2OH
O
HO
H
H
O H
OH
H
:B
O
H
O
HO
H
H
OH
H
O
H
OH
CH2OH
+
CH2OH
H-B
O
HO
CH2OH
CH2OH
D-fructose
CH2OH
O
H
CH2OH
Dihydroxyacetone
D-Glyceraldehyde
Glycolysis
H
O
CH2OH
C
H
OH
HO
phosphoglucose
isomerase
H
O
HO
H
H
OH
H
OH
H
OH
H
OH
D-glucose-6-phosphate
O
CH2OPO3
HO
OH
D-fructose1,6-bisphosphate
O
CH2OH
OH
OH
-D-fructofuranose6-phosphate
D-fructose-6-phosphate
CH2OPO32-
2-
O
aldolase
HO
OH
2-O POH C
3
2
phosphofructokinase
HO
CH2OPO32-
CH2OPO32-
2-O POH C
3
2
phosphoglucose
isomerase
H
H
OH
H
OH
CH2OPO32-
aldolase
CH2OPO32O
CHO
+
H
OH
CH2OPO32-
CH2OH
Dihydroxyacetone
phosphate
D-glyceraldehyde3-phosphate
D-fructose1,6-bisphosphate
triose phosphate
isomerase
278
25.21: Acylation and Alkylation of Hydroxyl Groups
Acylation (ester formation):
O
HO
HO
HO
O
HO
H3C
O
O
O
CH3
H3C
OH
pyridine
O
O
O
H3C
O
O
O
-D-glucopyranose
O
H3C
O
CH3
O
CH3
O
Alkylation (ether formation):
H
HO
HO
HO
O
HO
Ag2O, CH3I
OH
H3CO
H3CO
H3CO
H3CO
H3O+
O
OCH3
H3CO
H3CO
H3CO
H3CO
O
C
H
O
OCH3
H3CO
OH
-D-glucopyranose
H
H
OCH3
H
OCH3
CH2OCH3
25.22: Periodic Acid Oxidation. The vicinal diols of
carbohydrate can be oxidative cleaved with HIO4.
279