1. Lecture IV CHO Reactions II
Lecture #4 - CHO Reactions II

2. Reactions of Carbohydrates I Important Reactions
Carbonyl group (only)
Hydroxyl groups
Anomeric hydroxyl group
Both carbonyl & hydroxyl groups
Hydrolysis
Dehydration/degradation

3. Major Hexose Sugars (related to Glucose)6
CH2OH 5 O 1 4 OH OH OH 3 2
OH- to here =
Mannose
OH- to here =
Galactose OH
a-D-GLUCOSE
(a-D-Glucopyranose)

4. Reactions of Carbohydrates III Hydroxyl Groups
Ester formation*
Ether formation*
Cyclic acetal formation*
Oxidation to a carbonyl group*
Reduction to a deoxy carbon atom*
Replacement with amino,* thiol and halogeno groups
Note: Asterisks indicate common biochemical reactions

5. Reactions of Carbohydrates III Ester Formation I
Pyridine
(catalyst)
ROH +
(anhydride)
R-O-C-R’ O
(ester)
HO-C-R’ O +
(carboxylic acid) or R’ C Cl O
(acyl chloride)
Pyridine
(catalyst)
R-O-C-R’ O
(ester)
ROH + +
HCl

6. Reactions of Carbohydrates III Ester Formation II
D-Glucose C H O
CH2OH OH
CH2OH C OH
CH2OAc
CH2 C
OAc
AcO
NaBH4
Ac2O
Pyridine
(catalyst)
D-Glucitol
Acetylated D-Glucitol
Note, “Ac” = CH3C- =O

7. CHO Ester Examples “Natural” Components (esters) of Polysaccharides
In Synthetic CHO chemistry
Metabolic Intermediates
Modifications of Polysaccharides

8. Reactions of Carbohydrates III Hydroxyl Groups- Ether Formation
Ester formation*
Ether formation*
Cyclic acetal formation*
Oxidation to a carbonyl group*
Reduction to a deoxy carbon atom*
Replacement with amino,* thiol and halogeno groups
Note: Asterisks indicate common biochemical reactions

9. Reactions of Carbohydrates III Hydroxyl Groups- Ether Formation
Methylation analysis (steps follow)
Methylate polysaccharide
Hydrolyze (acid)
Analyze hydrolizate
Deduce where PS linkages were

10. Methylation Analysis I
CH2OH OH HO A
CH2 B C
ROH RO-
30% NaOH
For example ……..
1. Strong base in DMSO
2. Methyl Iodide (Me I) O
CH2OMe
OMe
MeO A
CH2 B C
90% formic acid
100o, 1 hr
Note, “Me” = CH3-

11. Methylation Analysis II
MeO O
CH2OMe
OMe A OH
m.p. = 72oC
2,3,4,6-Tetra-O-methyl-D-galactose + O
CH2OH
OMe
MeO HO B OH
Cool, concentrate
Dil H2SO4
14 hrs, 100o,
neutralize
A syrup +
2,3-Di-O-methyl-D-mannose O
CH2OMe
OMe HO C
MeO OH
A syrup
2,3,6-Tri-O-methyl-D-mannose

12. Internal Ethers 3 - 6 anhydro
Found in various red seaweed polysaccharides
agar
k- and i-carrageenans
fucellaran
R-OH + HO-R’ ---> R-O-R’ + H2O

13. Internal Ethers 3 - 6 anhydro ring
CH2OH OH OR O
H2C OR
H2O 5 1 4 2 3
Substituted D-galactose unit
3-6 anhydro ring in
k- or i-carrageenan
portion
R = H for k-carrageenan
& = SO3- for i-carrageenan

14. Internal Ethers Other anhydro ring compounds Sorbitan esters + +
1,5-anhydro-D-sorbitan
ester
1,4:3,6-dianhydro-D-sorbitan
ester
ether linkages
ether linkages
CH2OH C
H2C O
OCR =O
R’CO
R’CO =O
CH2OH C
H2C O
OCR
CH2 C
H2C O
OCR =O + +
1,4-anhydro-D-sorbitan
ester
R = stearic acid ester(C18)
R’ = palmitic (C16) acid ester

15. H2C =O C OCR =O R’CO C O =O C OCR =O OCR C CH2OH CH2OH O OH CH2OH O C6 5 4 3 2 1

16. Reactions of Carbohydrates III Hydroxyl Groups- Cyclic Acetals
Ester formation*
Ether formation*
Cyclic acetal formation*
Oxidation to a carbonyl group*
Reduction to a deoxy carbon atom*
Replacement with amino,* thiol and halogeno groups
Note: Asterisks indicate common biochemical reactions

17. Reactions of Carbohydrates III Cyclic Acetals II
CH2OH HO O
CH2OH
(CH3)2C
C(CH3)2
Acetone,
acid catalyst, or
dehydrating
agent
a-D-galactose 1,2; 3,4-diacetonide or
1,2,3,4-diisopropylidene-a-D-galacto-
pyranose
a-D-galactopyranose
acid catalysts = HCl, H2SO4
dehydrating agts = ZnCl2,
anyhd CuSO4, P2O5

18. Reactions of Carbohydrates III Cyclic Acetals II
O—CH2 O
CH2OH
a-D-glucopyranose
a-D-glucofuranose 1,2; 5,6-diacetonide or
1,2,5,6-diisopropylidene-a-D-gluco-
furanose

19. Reactions of Carbohydrates III Cyclic Acetals III
CH2OH OH
XANTHAN GUM
STRUCTURE
CH2OAc O
4,6-O-(1-carboxyethylidene) group or
pyruvic acid (CH3-CO-COOH) OH HO
COO-M+ O OH O
COO-M+
O–CH2 O C
CH3 OH OH O

20. Reactions of Carbohydrates III Oxidation of Hydroxyls I
Ester formation*
Ether formation*
Cyclic acetal formation*
Oxidation to a carbonyl group*
Reduction to a deoxy carbon atom*
Replacement with amino,* thiol and halogeno groups
Note: Asterisks indicate common biochemical reactions

21. Reactions of Carbohydrates III Oxidation of Hydroxyls II
COOH C OH C OH
30% HNO3 OH C OH C OH C
(boiling) OH C C OH C OH
CH2OH
COOH
D-Galactose
D-Galactaric acid
(Mucic acid)
30% HNO3
D-Glucaric acid
(Saccharic acid)
D-Glucose
(boiling)

22. NOTE: Pb(OAc)4 reacts similarly
Reactions of Carbohydrates III Oxidation of Hydroxyls III Periodate Oxidation I OR O
CH2OH OH HO O
CH2OH
HC=O OR +
O=CH
2 IO4-
pH 3 - 5
HCOH =O
HCOOH =
Formic acid
NOTE: Pb(OAc)4 reacts similarly

23. NOTE: Pb(OAc)4 reacts similarly
Reactions of Carbohydrates III Oxidation of Hydroxyls III Periodate Oxidation II O OH
HOH2C C H
OCH3 O
CHO
OCH3
2 IO4-
pH 3 - 5 +
HCHO
Formaldehyde
NOTE: Pb(OAc)4 reacts similarly

24. Reactions of Carbohydrates III Oxidation of Hydroxyls IV
OMe O
CH2OH OH HO
Methyl-a-D-glucopyranoside
OMe O
COOH OH HO
Methyl-a-D-glucopyranosiduronic
acid
N2O4

25. Reactions of Carbohydrates III Oxidation of Hydroxyls V
CH2OH OH
OMe
galactose
oxidase (GO) O
CHO OH
CH2OH
OMe
Methyl-b-D-Lactoside O
COOH OH
CH2OH
OMe
acid resistant
linkage
IO-
HOOH Oxidation
Fe2+ + HO-OH
Fe3+ + HO. + OH-

26. D-glucurono-g-lactone
Reactions of Carbohydrates III Oxidation of Hydroxyls VI Glucuronic acid and its Lactones OH O C H =O O
COOH OH HO
HOH
H2O,
HOH
HOR, OH-
COR =O
D-glucuronic acid
D-glucurono-g-lactone O
HOH
Borneol R=
HOH OH HO
D-glucuronide
(excreted) OH

27. Reactions of Carbohydrates III Hydroxyl Groups- Deoxy Cpds
Ester formation*
Ether formation*
Cyclic acetal formation*
Oxidation to a carbonyl group*
Reduction to a deoxy carbon atom*
Replacement with amino,* thiol and halogeno groups
Note: Base catalyst examples = Na2CO3, NaOH, Mg(OH)2, Ca(OH)2 or Na3PO4

28. Reactions of Carbohydrates III
cis or trans enediol
D-mannose, or
D-glucose
D-glucose
D-fructose
Lobry de Bruyn-Alberda van Ekenstein reaction of D-glucose.

29. Monosaccharide isomerization
CH2OH C OH O H
CH2OH C OH H
CH2OH OH C O
D-Fructose
trans-enediol
D-Glucose
CH2OH C HO OH O H
CH2OH C OH H
trans-enediol
D-Mannose

30. Reactions of Carbohydrates III Hydroxyl Groups- Deoxy Cpds
CH2OH
CH2 OH C H O
CH2OH OH = HO a b H+ C =O
CH2OH
CH2 OH C H
O:-
CH2OH
: OH OH =
OH-
3-Deoxyhexosulose
b-carbon
Meta-saccharinic
acid
enediol

31. Reactions of Carbohydrates III Hydroxyl Groups- Replacements
Ester formation*
Ether formation*
Cyclic acetal formation*
Oxidation to a carbonyl group*
Reduction to a deoxy carbon atom*
Replacement with amino,* thiol and halogeno groups
Note: Asterisks indicate common biochemical reactions

32. Reactions of Carbohydrates III Hydroxyl Groups- ReplacementsCN
NH2 O C H
CH2OH OH
D-Arabiose C C
NH2 N C OH C H C
HCN = O
NH3 C OH C OH C OH C OH
CH2OH
CH2OH H
(2)
(2a)
(1) C O C
NH2.HCl
H2 , Pt OH C
Also from Chitin!
HCl C OH C
(3) OH
CH2OH
D-Glucosamine hydrochloride