CARBOHYDRATES (SACCHARIDES, SUGARS)

(MONOSACCHARIDES, SIMPLE SUGARS)

PHOTOSYNTHESIS

Saccharide classification Monosaccharides (simple sugars) Glucose Mannose Ribose Oligosaccharides Sucrose Lactose Maltose Polysaccharides Starch Cellulose Pectins Hydrolyze to simple sugars. Contain many monosugars linked together Not hydrolyze to smaller molecules Hydrolyze to simple sugars. Contain 2-10 monosugars linked together

Monosaccharide structures an aldohexose a ketohexose an aldopentose

Naturally occurring D-sugars (R)-(+)-glyceraldehyde Configuration at stereogenic center farthest from the carbonyl group is on the right in Fischer projection

D-Aldoses an aldotriose 5 December 2016 aldotetroses

D-Aldoses aldotetroses aldopentoses

D-Aldoses

All Altruists Gladly Make Gum In Gallon Tanks D-Aldoses Allose Altrose Glucose Mannose Gulose Idose Galactose Talose All Altruists Gladly Make Gum In Gallon Tanks

D-Ketoses a ketotriose a ketotetrose a ketopentose a ketopentose

D-Ketoses ketopentoses ketohexoses

Cyclic forms of monosugars In monosugars carbonyl and hydroxyl groups are in the same molecule, so hemiacetal formed is a 6- or 5-membered ring with one oxygen atom – pyran or furan analogue

Cyclic forms of monosugars D-glucose, pyranose form D-fructose, furanose form

6- and 5-membered oxygen heterocycles

Interconversion of Fischer and Haworth projections D-glucose (Fischer) D-glucose (Haworth))

Two stereoisomers of pyranose form (anomers) α-D-glucopyranose 36% β-D-glucopyranose 64% α anomer β anomer

Mutarotation of monosaccharides α-D-glucopyranose (36%) [α]D = +112.2° β-D-glucopyranose (64%) [α]D = +18.7° At equilibrium [α]D = +52.6°

Chair conformations of glucopyranose anomers α-D-glucopyranose β-D-glucopyranose

Chair conformations of glucopyranose anomers Anomeric carbon (C1) Anomeric carbon (C1) α-D-glucopyranose β-D-glucopyranose

β-D-glucopyranose Anomeric hydroxyl

Physical properties of hexoses Crystalline solids, non-volatile, decompose at elevated temperature (caramelization) Polar, very well soluble in water, soluble to some extent in lower alcohols, insoluble in nonpolar organic solvents Form oversaturated solutions in water (syrups) – difficult for crystallization

Chemical properties of hexoses Enolization (isomerization) Oxidation Reduction Glycoside formation (acetals) Acylation (esters formation) Alkylation (ethers formation) Reactions with nitrogen nucleophiles Kiliani-Fischer chain lengthening Wohl degradation (chain shortening)

Chemical properties of hexoses Enolization (isomerization) D-glucose, D-mannose Keto-enol tautomerism (base or acid-catalyzed)

Chemical properties of hexoses Oxidation Tollens reagent Fehling reagent Ag0 Red solid Silver mirror

Chemical properties of hexoses Oxidation Oxidation of aldehyde group of aldose leads to aldonic acid

Chemical properties of hexoses Oxidation Oxidation of aldehyde and hydroxymethyl groups of aldoses leads to dicarboxylic aldaric acids

Chemical properties of hexoses Oxidation Oxidation of hydroxymethyl group of aldose leads to uronic acid

Chemical properties of hexoses Reduction Reduction of aldehyde group of aldoses leads to alditols

Acetal formation from hemiacetal Cyclic monosugar + alcohol → Glycoside + water

Chemical properties of hexoses Glycoside formation Acetal Hemiacetal

Glycosides in nature Bearberry Methylarbutin Skin-lightening activity

Glycosides in nature Salicin Anti-inflammatory activity Willow Salix alba Salicin Anti-inflammatory activity

Glycosides in nature Aglycon Amygdalin Cyanogenic glycoside

Properties of glycosides Exist as two distinct anomers - α or β Do not show reducing properties (ring does not open) Mutarotation is not possible (ring does not open) Stable in alkaline aq. solutions (like ethers) Hydrolyze in acidic aq. solutions into sugar and aglycon

Chemical properties of hexoses Acylation (esters formation)

Chemical properties of hexoses Alkylation (ethers formation)

Chemical properties of hexoses Reactions with nitrogen nucleophiles Reaction with hydroxylamine leads to D-glucose oxime

Chemical properties of hexoses Reactions with nitrogen nucleophiles Reaction with phenylhydrazine leads to D-glucose phenylhydrazone

Chemical properties of hexoses Reactions with nitrogen nucleophiles Reaction with excess of phenylhydrazine leads to D-glucose osazone

Chemical properties of hexoses Reactions with nitrogen nucleophiles D-glucose osazone can be converted into osone – 1,2-dicarbonyl derivative

Kiliani-Fischer chain lengthening of monosugars

Kiliani-Fischer chain lengthening of monosugars

Wohl degradation (chain shortening) of monosugars

GLYCOSIDES Monosugar + alcohol Glycoside + water Aglycon: 4-methoxyphenol Sugar: D-glucose

OLIGOSACCHARIDES

OLIGOSACCHARIDES Cellobiose, a 1,4’-β-glycoside D-Glup-(β 1→4)-D-Glup Monosugar + monosugar Disaccharide + water 1β,4’ glycoside bond Cellobiose, a 1,4’-β-glycoside D-Glup-(β 1→4)-D-Glup

CELLOBIOSE 1’ 1 4’

MALTOSE Maltose, a 1,4’-α-glycoside D-Glup-(α 1→4)-D-Glup 1α,4’ glycoside bond Maltose, a 1,4’-α-glycoside D-Glup-(α 1→4)-D-Glup

MALTOSE Maltose and cellobiose are diastereoisomers. The only differrence is the configuration of glycoside bond – α in maltose, β in cellobiose.

Cellobiose and maltose are reducing sugars They exist in two anomeric forms (α and β) Cellobiose and maltose are reducing disaccharides. They reduce Tollens or Fehling reagent They also show mutarotation

LACTOSE (milk sugar) Lactose, a 1,4’-β-galactoside 4-O-(β-D-galactopyranosyl)-D-glucopyranose Lactose, a 1,4’-β-galactoside D-Galp-(β 1→4)-D-Glup

LACTOSE (α anomer) Galactose Glucose

SUCROSE (saccharose, sugar) 1 2’ 2-O-(α-D-glucopyranosyl)-β-D-fructofuranoside Sucrose, a 1,2’-glycoside D-Glup-(1α→2β)-D-Fruf

SUCROSE Is sucrose reducing or nonreducing disaccharide? Fructose Glucose Glycoside bond Is sucrose reducing or nonreducing disaccharide?

OLIGOSACCHARIDES CYCLODEXTRINS 7 glucose molecules linked α1-4 form a ring

OLIGOSACCHARIDES CYCLODEXTRINS Outer surface is hydrophilic due to hydroxyl groups Cavity is hydrophobic and can accomodate lipophilic molecules Cyclodextrin form inclusion complexes with numerous compounds γ-cyclodextrin

CYCLODEXTRINS 6 7 8 Prepared by enzymatic cyclization of starch degradation products 7 Applications: food industry pharmaceutical industry chemical industry cosmetics agriculture environmental engineering chromatography 8

POLYSACCHARIDES 14 January 2019

POLYSACCHARIDES CELLULOSE Large molecules built from hundreds or thousands monosugars linked through glycoside bonds CELLULOSE D-Glucose units linked by β1- 4’ glycoside bonds

CELLULOSE Formation of cellulose fibers – intra- and intermolecular hydrogen bonds stabilize structure

CELLULOSE ACETATE (artificial fibre) Applications

(Energy storage in plants) STARCH (Energy storage in plants) Two kinds of D-glucose polymers AMYLOSE AMYLOPECTIN Soluble in cold water Insoluble in cold water

AMYLOSE Linear polymer of D-Glucose units linked by α1- 4’ glycoside bonds

AMYLOSE Spherical model of amylose helix

Branched polymer of D-Glucose units AMYLOPECTIN Branched polymer of D-Glucose units linked by α1- 4’ and α1- 6’ glycoside bonds

Branched polymer of D-Glucose units AMYLOPECTIN Branched polymer of D-Glucose units linked by α1-4’ and α1-6’ glycoside bonds

AMYLOPECTIN 1,6 glycoside bond 1,4 glycoside bond

Branched polymer of D-Glucose units GLYCOGEN Branched polymer of D-Glucose units linked by α1- 4’ and α1- 6’ glycoside bonds

Comparison of amylose, amylopectin and glycogen

Other important carbohydrates Pentoses Structural fragment of RNA Structural fragment of DNA

Other important carbohydrates (β-L-6-deoxygalactose) Deoxysugars β-L-Fucose (β-L-6-deoxygalactose)

Other important carbohydrates Aminosugars α-D-glucosamine

Other important carbohydrates Aminosugars β-D-N-acetylglucosamine (monomer of polysaccharide - chitin)

CHITIN GlcNAc units linked by β1→4’ glycoside bonds

Gentamicin (antibiotic)

Streptomycin (antibiotic)

Carbohydrates on cell surfaces Human blood group types

Structures of blood group antigenic determinants Group B

Structures of blood group antigenic determinants

Red blood cell compatibility Recipient[1] Donor[1] O- O+ A− A+ B− B+ AB− AB+ O−   compatible incompatible