Carbohydrates Slides 1-34

Front 1

Glycan

Back 1

Polysaccharide

Front 2

Glycoproteins

Back 2

“Glucose-protein”

proteins with short branched carbohydrate chains bonded to the side chains of the amino acids

use: receptors, recognition, interaction

ex. Antigens

Front 3

Proteoglycans

(mucopolysaccharides)

Back 3

“Protein-saccharides”

proteins with long, linear carbohydrate chains bonded to the side chains of the amino acids

use: connecting tissues and cartilage

Front 4

Peptidoglycans

Back 4

“Peptide-saccharides”

long linear carbohydrates crosslinked by short oligopeptides

use: bacteria cell wall

Front 5

Lipopolysaccharide

Back 5

Fatty acids linked to carbohydrate

use: outer envelope of gram negative bacteria

Front 6

Carbohydrates

Back 6

“Carbon-hydrated”

organic molecules mainly composed of C, H, and O

Front 7

Simple Sugars

Back 7

Have the empirical of a carbohydrate Cn(H2O)n

When in hydrated form are classified as polyhydroxyaldehydes or polyhydroxyketones

^ either are these or are molecules which form these when hydrated

Front 8

Polyhydroxyaldehyde

Back 8

Simple sugar which when hydrated has a aldehyde functional group

Front 9

Polyhydroxyketone

Back 9

Simple sugar which when hydrated has a ketone functional group

Front 10

Monosaccharide

Back 10

“one-sugar”

a carbohydrate that cannot be obtained via the hydrolysis of a polysaccharide or oligosaccharide

Front 11

Polysaccharide

Back 11

“multiple-sugar”

reserved for sugar linkages greater than 10

Difficult to make in the lab

Front 12

Oligosaccharide

Back 12

“small group of-sugar”

reserved for sugar linkages between 3 and 10 sugars

Front 13

Disaccharide

Back 13

"two sugar"

Two linked carbohydrates

Front 14

Classification of saccharides

Back 14

1. By # of carbons - #—one

2. By functional group

- Aldo (for aldehyde groups) = Aldose

- Keto (for ketone groups, assumed position 2 is unspecified) = Ketose

3. By both

- Group—#—ose

- Note here that Keto can be represented instead by the ending close

- Thus Ketohexose = hexulose

Front 15

Triose

Back 15

Smallest simple sugar monomer, composed of three carbons

- Can be aldotriose (aldehyde C1 or C3) or a ketotriose/triulose (ketone C2)

- aldotriose has a chiral centre, triulose does not

Front 16

Fischer Projections of saccharides

Back 16

Saccharides are often drawn in fisher and show most oxidized carbon at the top

- horizontal bonds project out of the page, vertical bonds project in

Front 17

Enantiomers

Back 17

ALL chiral centres have opposite configuration

Rotate plane polarized light in opposite directions but SAME magnitude

(appear LIKE mirror images)

- Right is (+)- Left is (-)

- this has noting to do with R/S

Front 18

D and L naming

Back 18

Glyceraldehyde

- D ia (+) rotation of PPL

- L is (—) rotation of PPL

Every other sugar

Defined by the orientation of the furthest stereocenter from the carbonyl group (aldehyde or ketone)

- Position of the OH (usually on the penultimate)

- D has its OH on the right

- L has its OH on the left

Front 19

Penultimate Carbon

Back 19

Second last carbon (last chiral centre of the chain)

Usually used to define the D/L orientation of a saccharide

Front 20

Meso

Back 20

Compounds which do not rate plane polarized light (PPL)

- have a plate of symmetry dividing them in half

- Optically inactive

Front 21

Rotation of Plane Polarized Light

Back 21

Only linked to D/L in glyceraldehyde

Must be experimentally derived for all other sugars

Front 22

Hemiacetal

Back 22

Product of reaction of aldehyde or ketone with alcohol in acidic or basic conditions

A carbon atom is bonded to ONE heteroatom

Unstable —> readily revert back to alcohol and carbonyl components

Front 23

Conditions for hemiacetalation

Back 23

- Acidic: protonates the carbonyl and makes more electrophilic to weak OH nucleophile

- Basic: deprotonates the alcohol and makes it a better nucleophile for the electrophilic carbonyl carbon (anomeric carbon)

Front 24

Anomeric Carbon

Back 24

carbonyl carbon in a saccharide/carbohydrate new stereocenter formed here during hemiacetalation

- configuration of new stereocenter determines which anomer is present (beta or alpha)

Front 25

Anomers

Back 25

Stereoisomers differing based upon the configuration at their anomeric carbon

- Beta Anomer: OH is cis to terminal CH2OH

- Alpha Anomer: OH is trans to terminal CH2OH

The above ONLY hold true from hemiacetals formed using penultimate carbon

Front 26

Diastereomer

Back 26

steoisomers that differ at one or more (but not all) of their stereocenters

Front 27

Optical Rotation

Back 27

allows us to quantify the conversion between enantiomers/ anomers

Front 28

Mutarotation

Back 28

the process by which interconversion of a dissolved anomer results in a equilibrium mixture of both anomers (alpha and beta)

Will be DIASTEREOMERS

- The amount of each anomer present does not have to be equal

- the final specific rotation [alpha] after can be calculated by a weighted average of the percent of each anomer present at equilibrium and their specific rotation [alpha] when pure

- There will be a larger amount present of the anomer with a specific rotation further from equilibrium [alpha] in the final mixture

- specific rotations must e experimentally measured

Front 29

Glycoside

Back 29

Acetal of a sugar

A carbon is bonded two two heteroatoms and two R groups

- are stable in basic and neutral ph

- only revert to open chain in acid and glocosidase enzyme

named: sugar-ring-aside

Glycosidic linkages can form between glycosides and are used to join monosaccharides together

Formation requires acid and an alcohol (commonly methanol)

Sn1 reaction, with carbocation intermediate

A mixture of alpha and beta anomeric glycosides will form regardless of the hemiacetal we start with

NO mutarotation

Front 30

N-Glycosides

Back 30

Acetals of sugars found in nucleosides.

One of the heteroatoms bonded to the anomeric carbon is a Nitrogen

Nucleic acids

Front 31

Heteroatom

Back 31

any atom that is no carbon (C) or hydrogen (H)

Front 32

NaBH4

Back 32

Reduces aldehydes and ketones to alcohols

Front 33

Optically inactive product

Back 33

Product is meso (plane of symmetry)

Front 34

D or L based on position of CH2OH

Back 34

Upwards: D

Downwards: L

Front 35

Mutarotation Vs Optical Activity

Back 35

Requirements for mutarotaion: Compound originally has chirality (not meso) and has hemiacetal

If compound does not have hemicaetal it does not mean its optically inactive, it means it CANT mutarotate

Compounds are optically active unless they are achiral

Front 36

Aldonic acids

Back 36

Sugars which undergo a CHO—> COOH oxidation via a weak [O] agentSuffix “-onic”

Front 37

Requirements for Oxidation to aldonic:

Back 37

-hemiacetal -aldehyde sugar -Weak [O] agent (strong agent with oxidize alcohols as well)

Front 38

Reducing sugar:

Back 38

a sugar that can reduce and oxidant Must have an aldehyde group or the potential for aldehyde functionality (hemiacetal when linked) Sugars like sucrose which have an aldehyde however have no aldehyde potential due to glycosidic bond at the anomeric carbon with reduce once hydrolyzedSugar is in turn oxidized

Front 39

Agents used in Aldonic acid oxidation:

Back 39

(1) Bromine water: - Bromine dissolved in water - Br2 is reduced to two Br- ions by the reducing sugar

(2) Tollens Reagent: - [Ag(NH3)2]+ Functions as Ag+ - Oxidation is indicted by formation of silver mirror

(3) Benedict’s Reagent (Feelings)- Cu2+ in citrate (benedicts) OR tartrate buffer (fellings) - Oxidation is indicted by red solid formation (Cu2O)

Front 40

Alaric Acids:

Back 40

Sugars which undergo a CHO—> COOH oxidation AND a Primary alcohol oxidation Suffix “-aric”use nitric acid (HNO3)Done using a stronger [O] agent than Aldonic but not strong enough to oxidize secondary alcohols(primary alcohol on CH2OH) Can produce meso compounds.

Front 41

Uronic acids:

Back 41

Sugars with ONLY the primary alcohol oxidized Aldehyde is protected during the reaction Enzyme is used for this

Front 42

Glucuronic Acid

Back 42

The uronic acid of glucose formed via oxidation by an enzyme

Will form a glycoside with toxic substances, the aldehyde makes it more water soluble and skier to excrete in urine

Used by liver to detoxify

This is the compound tested for in drug testing (instead of test for each parent molecule we test for glucuronic acid because we know the drugs will be bound to it)

Front 43

Aditol:

Back 43

Sugar with reduced carbonylProduces “sugar alcohols”Reduction of ketone can result in new steeocenter Results in formation of CH2OH in place of CHO

Front 44

Reducing agents for Aditol formation:

Back 44

Catalytic hydrogenation

(H2/metal)

NaBH4

LiAlH4

Front 45

Sugar Alcohols:

Back 45

poorly absorbed by the body

Poorly metabolized #lowcal

Reduction of carbonyl group

Front 46

Alpha hydrogen:

Back 46

Hydrogen attached to carbon directly bonded to functional group(for our purposes, carbonyl group)

Presence of alpha hydrogen allows for tautomerization to enol form for aldehydes and ketones

Front 47

Epimer:

Back 47

stereoisomersdiastereomers that differ in the configuration of any one stereocenter

Front 48

Epimerization:

Back 48

Creation of epimers via enolate formation

creates and sp2 carbon (loss off stereochemistry)

- Deprotonation results in spy, reprotonation can occur from either side thus results in loss of stereochemistry.

Front 49

Tautomer:

Back 49

Constitutional isomer involving the movement of a proton (+) and a double bond position (=)

Front 50

Isomerization:

Back 50

ene-diol rearrangement resulting in isomerization of aldehydes to ketones and ketones to aldehydes

Front 51

Epimerization and Isomerization:

Back 51

Both occur in basic environments and so occur together.

Front 52

Benedict’s reagent:

Back 52

weak [O] agent

Used in basic (alkaline) conditions

can be used to test is sugar is reducing (aldehyde)

will give false positive for ketoses as it is basic and will spur isomerization reactions, changing some ketones to aldehydes, then oxidizing them.

(the original sugar is not being oxidized by bennedicts, the product of a side reaction is)

Front 53

Enol form:

Back 53

Double bond between carbonyl carbon and alpha carbon, OH where =O once was (proton shift from alpha C to carbonyl O)

Front 54

Keto form:

Back 54

Double bonded oxygen in carbonyl group off carbonyl carbon

Alpha carbon single bonded to carbonyl carbon, has H from OH in enrol form

Front 55

Enolate:

Back 55

Deprotonated enol form

Front 56

Aldol reaction:

Back 56

Nucleophilic addition forms new C-C bond

Enolate attacks aldehyde or ketone (double bond electrons attack vagina region of aldehyde or ketone)

Electrophile becomes the alcohol (enolate retains =O)

Adds beta hydroxy group

Front 57

Adolase:

Back 57

catalyzes gluconeogenisis(formation of 1,6- bisphosphate)

Deprotonates DHAP, protonates GAP once attacked by DHAP

Front 58

Retro-Adol reaction:

Back 58

glycolysis