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