The Carbohydrates [C(H 2 O)] n Emil Hermann Fischer (1852-1919)
The Carbohydrates [C(H2O)]n
Title
Emil Hermann Fischer (1852-1919)
C6-CH2OH
CHO
C5-OH
C4-OH
C2-OH
C3-OH
The Fischer-Rosanoff Convention
F-R Convention
CHO
CH2OH
OH
OH
OH
OH
H
H
H
H
CHO
CH2OH
OH
OH
OH
OH
H
H
H
H
Fischer Projections Rosanoff Modification
OH on the right of the highest numbered chiral carbon = D-series.
Fischer-Rosanoff D- and L-Series
OH on the left of the highest numbered chiral carbon = L-series.
D/L Series
The D-Aldohexoses
C4 4 right 4 left
8 right
C2
2 right 2 left 2 right 2 left C3
right left right left right left left right
Allose Altrose
Glucose Mannose
Gulose Galactose Idose Talose
All altruists gladly make gum in gallon tanks [L. Fieser]
D-Aldohexoses
C5
Reactions of Aldoses
3 equiv. PhNHNH2 3 equiv. PhNHNH2
OH OH OH
HO CHO
CH2OH
CHO
OH OH OH OH
CH2OH
+ PhNH2 + NH3
=N-NHPh
=N-NHPh
CH2OH
OH OH
OH osazone
CO2H
OH OH OH OH
CH2OH aldonic acid
Br2/H2O Br2/H2O
aldonic acid
HO CO2H
OH OH OH
CH2OH alditol
OH OH OH OH
CH2OH
CH2OH
alditol
NaBH4 NaBH4
OH OH OH
CH2OH
CH2OH
HO
achiral
CO2H
OH OH OH OH
CO2H aldaric acid aldaric acid
CO2H
OH OH OH
CO2H
HO
HNO3 HNO3
achiral
Rxn of Aldoses
More on Osazones
1 equiv. PhNHNH2
=N-NHPh OH
OH OH
CH2OH
HO
D-glucose phenylhydrazone
CHO
OH
OH OH
CH2OH
HO
D-glucose
OH OH
HO CHO
CH2OH
HO
D-mannose
OH OH
CH2OH
CH2OH
HO
D-fructose
O
OH OH
HO =N-NHPh
CH2OH
HO
D-mannose phenylhydrazone
1 equiv. PhNHNH2
3 equiv. PhNHNH2
Ca(OH)2 Ca(OH)2
(Lobry de Bruyn- Alberda van Eckenstein rearrangement, 1895)
Osazones
+ PhNH2 + NH3
2 equiv. PhNHNH2
2 equiv. PhNHNH2
=N-NHPh
=N-NHPh
CH2OH
OH OH
HO
Chain Lengthening and Shortening of Aldoses
OH OH OH
CH2OH
CHO
OH OH OH
HO CN
CH2OH
CN
OH OH OH OH
CH2OH
HCN Fischer-Kiliani Synthesis
HCN Fischer-Kiliani Synthesis
Pd/BaSO4 pH 4.5, H2
Pd/BaSO4 pH 4.5, H2
CHO
OH OH OH OH
CH2OH
HO CHO
OH OH OH
CH2OH
Fe+++ H2O2
Ruff Degradation
CO2Ca1/2
OH OH OH OH
CH2OH
HO OH OH OH
CH2OH
CO2Ca1/2 Br2/H2O Br2/H2O
Aldonic acid as Ca salt
F-K and Ruff
Interrelationship of the D-Series of Aldoses via Chain Lengthening and Degradation
D-Series Interrelationship
The Aldohexoses
D-series
L-series
But which one is (+)-glucose?
Which one is Glucose?
Rosanoff Formulation of C6 Aldaric Acids and Alditols
Terminal groups identical; CO2H or CH2OH
Aldaric Acids/Alditols
1 2 3 4 5 6 7 8
9 10 11 12 13 14 15 16
Fischer’s Proof: Part 1
(+)-Glucose forms an optically active aldaric acid and optically active alditol.
• 1, 7, 9, 15 eliminated: plane of symmetry, achiral
X
X
X
X
Fischer Proof: 1
Fischer’s Proof: Part 2
(+)-Glucose and (+)-mannose form the same osazone. If 1, 7, 9, and 15 are not related to (+)-glucose, then they are not related to (+)-mannose nor are 2, 8, 10, and 16 related to (+)-glucose.
1 2 3 4 5 6 7 8
9 10 11 12 13 14 15 16
X
X
X
X
X
X
X
X
Fischer Proof:2
Fischer’s Proof: Part 3
(+)-Arabinose affords (-)-glucose and (-)-mannose by Kiliani-Fischer synthesis.
What is the structure of arabinose?
(+)-Arabinose must be of the opposite series (D/L)as (+)-glucose and have the same absolute configuration at C3-5 as (-)-glucose and (-)-mannose.
Fischer Proof:3
• Arabinose is either
or • Arabinose forms an optically active aldaric acid (arabinaric acid) and optically active alditol (arabitol) as its borax complex.
F P:3, con’t
X
and not
X
• Arabinose is
X X
X X
• (+)-Glucose is one of these structures
Fischer’s Proof: Part 4
The pentose (+)-xylose affords optically inactive xylaric acid and optically inactive xylitol as its borax complex.
• (+)-Xylose can only be one of the following: X X
• These enantiomers cannot be (+)-xylose because their Fischer-Kiliani hexoses (already eliminated) would lead to one optically active and one optically inactive aldaric acid.
• (+)-Xylose must be one of the remaining two structures.
Fischer-Kiliani synthesis of (+)-xylose leads to two new hexoses, (+)-gulose and (+)-idose, both of which form optically active aldaric acids.
Fischer Proof:4
Fischer’s Proof: Part 5
• (+)-Gulose/(+)-Idose
• (+)-Xylose
• (+)-Arabinose
• (+)-Glucose/(+)-Mannose
Fischer Proof:5
or
Fischer’s Proof: Part 5
(+)-Glucose and (-)-gulose form the same optically active aldaric acid, glucaric acid.
identical
identical
• (+)-Glucose must be either
Fischer Proof:5, con’t
• Mannaric acid is formed from a single hexose.
Fischer’s Proof: Part 5
identical
identical
rotate 180o
rotate 180o
• (+)-Mannose must be one of these hexoses, the C2 epimer of (+)-glucose.
mannaric acid
Fischer Proof:5, con’t-2
Fischer’s Proof: Part 6
But which enantiomer of glucose is (+)-glucose?
D-glucose L-glucose
Just Guess!
• Fischer arbitrarily assigned the D-series to the dextrorotatory enantiomer.
• Sixty years later (1951), he was proved correct when Bijvoet related (+)-glucose to (+)-tartaric acid.
• Fischer: All sugars related to D-(+)-glucose by chemical correlation belong to the D-series.
Fischer Proof:6
(-)-Galactose
Identical Achiral Mucic Acid (An Aldaric Acid)
A Flaw in the Fischer Scheme
(+)-Galactose (+)-Galactose
(+)-Glucose (-)-Glucose
Fischer’s Flaw
"Two aldoses can produce the same dibasic acid only if they belong to the same stereochemical family. That this, however, is erroneous as a general proposition, may be readily seen from the fact that the two enantiomorphous galactoses - plainly belong to the opposite families - yield the same mucic acid.” A. M. Rosanoff-1906
2 4
8
16
mirror plane
Rosanoff’s Reorganization of the Carbohydrates
δ-series λ-series
• Arranged by successive Kiliani syntheses
• The D- and L- assignments were Fischer’s based on chemical correlation with D-(+)-glucose, an unreliable scheme.
Rosanoff’s Wheel
Optical Activity Configuration
Fischer-1891 +/- d,l
Rosanoff-1906 +/- δ,λ
Today +/- = d,l D,L
Evolution of Signage
Evolution of Signage
The D-Series of Aldoses
(+)-glyceraldehyde
(+)-threose (-)-erythrose
(-)-ribose (-)-arabinose (+)-xylose (-)-lyxose
(+)-altrose (+)allose (+)-glucose (+)-mannose (-)-gulose (-)-idose (+)-galactose (+)-talose
aldotriose
aldotetrose
aldo hexose
aldo pentose
All altruists gladly make gum in gallon tanks [L. Fieser]
D-Aldohexoses
Fischer Projections of Glucose
D-(+)-Glucose
CHO
OH
OH
HOH2C
HO
OH
=
rotate C5 about C4 by 120o
form hemiacetals between C5-OH and C1
CHO
OH
OH
OH
HO
CH2OH
2 3
4
5
Fischer Projections
C
OH
OH
O
HO
CH2OH
HO C
OH
OH
O
HO
CH2OH
OH
Fischer Projections of Glucopyranose Anomers
β-D-(+)-Glucopyranose α-D-(+)-Glucopyranose
right alpha
left beta
Anomers
Haworth Projections of Glucopyranose Anomers
O
CH2OH
OH
OH
OH
OHO
CH2OH
OH
OH
OHOH
β-D-(+)-Glucopyranose α-D-(+)-Glucopyranose
up (top) beta
down (bottom) alpha
Haworth
Chair Conformations of Glucopyranose Anomers
β-D-(+)-Glucopyranose α-D-(+)-Glucopyranose
up (top) beta
down (bottom) alpha
O O H
H O H O
O H
O H
O O H
H O H O
O H O H
Conformational Glucopyranose
How an Old Salt Remembers
starboard
right
fewer letters
port
left
alpha beta
down up
bottom top
more letters
red light green light
Old Salt
Mutarotation of Anomers
β-D-(+)-Glucopyranose
O O H
H O H O
O H
O H
α-D-(+)-Glucopyranose
O O H
H O H O
O H O H
Crystallizes above 98oC
pure β-anomer mp 150oC [α]D = +18.7o
Crystallizes below 98oC
pure α-anomer mp 146oC [α]D = +112.2o
H2O H2O equilibrium mixture [α] = +52.6o
β/α =64/36
Mutarotation
Ring Sizes of Hexoses
Ring Sizes of Hexoses
Hexose Pyranose Form (%α/%β) Furanose Form allose 92 8 altrose 70 30 glucose ~100(36.5/63.5) <1 mannose ~100(67/33) <1 gulose 97 3 idose 75 25
galactose 93(27.5/72.5) 7 talose 69 31
fructose 67 33
Periodic Acid Cleavage of Carbohydrates as a Diagnostic Tool
CH2=O + OH
CHO CH2=O + HCO2H
OH
OH
HO H2O
HIO4
HIO4
OH
OH 2 CH2=O
HIO4
OH
OH
OH
HIO4
Formaldehyde (CH2O) arises from a primary alcohols
Formic acid (HCO2H) arises from a secondary alcohols
Periodic acid
Periodic Acid Cleavage of Carbohydrates as a Diagnostic Tool
OH
OH
CHO
HIO4
OH
OH
OH
HIO4 2 CH2=O + HCO2H
CH2=O + 2 HCO2H
HIO4 OH
OH
O CH2=O + OH
CO2H HIO4 CH2=O + CO2
• RCH2OH CH2=O
• R2CHOH HCO2H
• RCH=O HCO2H
CO2 • R2C=O
Periodic Acid Diagnostic
Periodic Acid Cleavage of Carbohydrates
HCO2H
HCO2H HCO2H
HCO2H HCO2H
H2CO CH2OH
CHO
HO OH OH
OH
D-glucose
CH2OH
HO OH OH
CH2OH
HO
D-mannitol
H2CO
HCO2H HCO2H HCO2H HCO2H H2CO
H2CO
HCO2H HCO2H HCO2H H2CO
CO2 HO
OH OH
CH2OH
O
OH
D-fructose
Periodic on Carbohydrates
Methylation of Pyranoses: Pyranosides
HO HO
HO
OH O
OCH3
HO HO
HO
OH O
OH
CH3OH, H+
CH3O O
OCH3 CH3O
CH3O
OCH3
CH3I Ag2O (CH3)2SO4
NaOH
CH3O O
OH CH3O
CH3O
OCH3 H3O+
Methylation
Ring Size of Pyranosides
CH3O O
OH CH3O
CH3O
OCH3
CH3O
CH3O O
CH3O
OCH3
CO2H
OCH3
OCH3
CO2H
CO2H
CH3O
OCH3
CO2H
CO2H
CH3O
HNO3
HNO3
via oxidation of the enol of the ketone
HNO3
Ring Size
Periodic Acid Cleavage of Methyl α-Glucopyranoside
HO HO
HO
OH O
OCH3
OH O
OCH3
OHC
OHC HCO2H
HIO4
H3O+
OH
OH
CHO
+ OHCCHO + CH3OH
D-glyceraldehyde
glyoxal
Periodic on Glycosides
OHO
HOHO
HOOCH3
OHO
HOHO
HOOCH3
Methyl α-D-glucoside Methyl β-D-glucoside
maltase
α-D-glucose
OHO
HOHO
HOOH
OHO
HOHO
HOOH
emulsin
β-D-glucose
Enzymatic Cleavage of Glucosides
H3O+
Enzymes
The Silver Mirror Test
Methyl -D-glucoside
OHO
HOHO
HO OCH3
non-reducing sugar (a glycoside)
no reaction Tollens reagent Ag(NH3)2
+ OH-
Tollens reagent Ag(NH3)2
+ OH-
OHO
HOHO
HO OH
D-glucose
CO2H
CH2OH
OH
OHOH
HO+ Ago silver mirror
reducing sugar (an aldose) www.chem-pics.co.uk/download.htm
Tollens
The Silver Mirror Test
Aldoses and ketoses are reducing sugars
OHO
OH
OHHO
OH
β-D-fructofuranose
CH2OH
CH2OH
OHOH
HOO
D-fructose
Ag(NH3)2+ OH-
CH2OH
OHOH
HOOH
OHenediol
CHO
CH2OH
OHOH
HOOH
Ag(NH3)2+ OH-
Ago +
silver mirror
Ag(NH3)2+ OH-
CO2H
CH2OH
OHOH
HOOH
Tollens 2
Disaccharides
and
Polysaccharides
Intro: Di- and Polysaccharides
α-D-Glucopyranosyl- β -D-fructofuranoside
or β-D-Fructofuranosyl-α-D-glucopyranoside
HO
HO HO
HO
HO
HO
OH
OH O
O
O
Sucrose (non-reducing sugar)
RCOO
RCOO RCOO
RCOO
RCOO
RCOO
OOCR
OOCR O
O
O
Olestra (R=n-CnH2n+1; n=6-8)
ketal
acetal
Sucrose/Olestra
This discussion brings to mind a wonderful story told to me by Professor Harry Wasserman (Yale), who during the late 1940's was a graduate student of Professor R. B. Woodward at Harvard. Apparently Woodward had received a notice of a $1,000 prize for the first person to accomplish a chemical synthesis of sucrose. He went into the laboratory and said to his students that all they had to do was connect two molecules of glucose together [...and lose a molecule of water] and they would have themselves $1,000. One student, obviously not overwhelmed by Woodward's stature in the field even at such a young age, replied that if you did it that way,
Sucrose is Formed from Glucose and Fructose
the prize would be $2,000!
Woodward
OHO
OH
OHHO
OHO
OH
OHOH
O
Sucralose
Sucralose
1,6-Dichloro-1,6-dideoxy-β-D-fructofuranosyl-4-chloro-4-deoxy-α-D-galactopyranoside
OOH
OHHO
OCl
OH
OHCl
O
Cl
Sucralose (600 times sweeter than sucrose)
Sucrose (non-reducing sugar)
OHO
OH
OHHO
OHO
OH
OHOH
Ogluco
galacto
Bees Do It
Sucrose [α]D = +66.5o (non-reducing, non-mutarotating sugar)
HO
HO HO
HO
HO
OH
OH O
O
O HO
invertase
CH2OH
CHO
HO OH OH
OH
D-glucose [α]D = +52.7o dextrose
HO OH OH
CH2OH
O
OH
D-fructose [α]D = -92.4o
levulose
or H3O+
Bees Do It
OHOHOHO
HOO
OHO
HOHO
OOHO
HOHO
OH
n
Cellulose (polysaccharide)
partial hydrolysis H3O+
OHOHOHO
HOO
OHO
HOHO
OH
Cellobiose (disaccharide)
4-O-(β-D-glucopyranosyl)-D-glucopyranose
β-acetal linkage
emulsin, β-glucosidase (termites, ruminants)
Disaccharides-Cellobiose
4-O-attachment
Cellobiose
OHOHOHO
HOO
OHO
HOHO
OH
Cellobiose
Cellobiose-Structure Proof
• positive Tollens test ----> reducing sugar
• hydrolysis ----> only D-glucose • emulsin ----> β-glucoside
permethylation
OMeOMeOMeO
MeOO CO2H
OMeMeO
MeOMeO
Br2/H2O OHOHOHO
HOO CO2H
OHHO
HOHO
tetramethoxy aldehyde
H3O+
CHO
CH2OMe
OMe
OMeOH
MeO
tetramethoxy- carboxylic acid
CO2H
CH2OMe
OMe
OHOMe
MeO
• shows mutarotation
Cellobiose-Str. Proof
OHOHOHO
HOO
OHO
HOHO
OH Cellobiose-Structure Proof OMeOMeOMeO
MeOO CO2H
OMeMeO
MeOMeO
tetramethoxy aldehyde
CHO
CH2OMe
OMe
OMeOH
MeO
tetramethoxy- carboxylic acid
CO2H
CH2OMe
OMe
OHOMe
MeO
hot HNO3
CO2H
CO2H
OMeMeO
dimethyl L-tartaric acid
CO2H
CO2H
OMe
OMeMeO
trimethyl xylaric acid
hot HNO3
CO2H
CH2OMeOMe
dimethyl D-glyceric acid
Cellobiose-Str. Proof
Disaccharides: Maltose
• positive Tollens test ----> reducing sugar
• hydrolysis ----> only D-glucose • maltase ----> α-glucoside
• shows mutarotation
Starches: poly-α-D-glucosides
OHO
HOHO
OH
OHOHOHO
HOO
Malt (barley) maltase
• differs from cellobiose at the glycosidic anomeric center
Maltose
OHO
HOHO
OOHO
HOHO
OH
HO
Disaccharides: Lactose
4-O-(β-D-galactopyranosyl)-D-glucose
• positive Tollens test ----> reducing sugar
• hydrolysis ----> D-glucose and D-galactose
• shows mutarotation
~5% of human and cow milk
Lactose
• β-galactosidase (lactase) ----> β-galactoside
• lactose intolerance
Disaccharides: Amygdalin
OHO
HOHO
HOO
OHO
HOHO
O CN
PhH
Laetrile (laevorotatory mandelonitrile), “vitamin 17”
1,6-β-linkage
cyanohydrin of benzaldehyde β-linkage
Touted in some circles as a treatment for cancer.
1836 - Isolated from bitter almonds by Wohler. Demonstrated that emulsin produces glucose, benzaldehyde and prussic acid (HCN)
Amygdalin
OHOHOHO
HOO
OHO
HOHO
OOHO
HOHO
OH
n
OMeOMeOMeO
MeOO
OMeO
MeOMeO
OOMeO
MeOMeO
OMe
n
permethylation
OMeO
MeOMeO
MeO OH
OMeO
HOMeO
MeO OH
H3O+
2,3,4,6-tetra-O- methyl D-glucose (terminal)
2,3,6-tri-O- methyl D-glucose (chain) 100-200 units
0.6% 99.4%
Cellulose: Chain Length
Cellulose: Chain Length
Starches: Plant Polysaccharides
Starches: Plant Polysaccharides
OHO
HOHO
OHOHOHO
HOO
OHO
HOHO
O
n OH
Amylose :
• ~20% water soluble starch; poly 4-O-(α-D-glucoside)
• forms helical structure; blue complex with iodine
Amylopectin:
• ~80% water insoluble starch branched poly-4-O-(α-D-glucoside)
Starches: Plant Polysaccharides
Starches: Plant Polysaccharides
• permethylation:
Average 20 glucose units /chain
90% 2,3,6-tri-O-methyl-D-glucose
OMeO
HOMeO
MeO OH
chain
~5% 2,3-di-O-methyl-D-glucose
OHO
HOMeO
MeO OH
junction
~5% 2,3,4,6-tetra-O-methyl-D-glucose
OMeO
MeOMeO
MeO OH
terminus
• permethylation/hydrolysis
And Finally, a True Story
In March of 1986 I was in California visiting several universities. While at Stanford University, I stopped at the health center to have a swollen foot examined. The young resident was very attentive. To assess his qualifications, I asked him where he had attended college. “M.I.T.,” he responded. “So you must have had Professor Kemp for organic chemistry,” I countered. “Yes, I did,” he said. Then I asked, “What D-aldohexose forms the same osazone as glucose?”
“I really enjoyed organic chemistry!” Really?
“Organic, don’t remind me!” An honest man?
“I know the mechanism of the aldol condensation.” Wrong chapter!
“I know what a Grignard reagent is.” Wrong test!
“Wait! Give me some time.” “It’s only an hour exam.”
Response: My thought:
Like Diogenes the Cynic in search of an honest man (person), I have posed this question to many a practitioner of the medical and dental professions. Neither Diogenes nor I have fulfilled our quests. However, the responses to my query were often amusing.
Diogenes
The Moral of the Story
Somewhere,…sometime…someone might ask you this question.
What D-aldohexose forms the same osazone as D-glucose?
Moral
Your answer will be...
D-Mannose!
The End
The End