carbohydrate fischer projection vn

7/27/2019 Carbohydrate Fischer Projection VN

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Carbohydrate

Nhm cc hp cht polyhydroxylated aldehydes andketones thng c gi l ng c tng hp bi cy xanh qua qu trnh quang hp Tn bt ngun t glucose

Glucose l cht carbohydrate n gin u tin thuc dng tinh khit.

CTPT glucose, C6H12O6, l hydrate of carbon,C6(H2O)6

~ 50% trng lng kh sinh khi ca tri t l baogm cc polymerglucose

Carbohydrates


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Carbohydrates hot ng nh nhng cht trung gian ha hc

qua n nng lng nh sng mt tri c d tr v sdng h tr s sng trn tri t

Carbohydrates


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Carbohydrates c chia n gin

hoc phc tp ng n hay monosaccharides

Carbohydrates nh glucose vfructose khng th chuynthnh ng n gin hn qua

phn ng thy phn Carbohydrates phc tp

To thnh t 2 hay nhiung n

Sucrose l mt disaccharide ls kt hp ca glucose vfructose

Cellulose l mtpolysaccharidec kt hp bi hng ngnn v glucose

21.1 Phn loi Carbohydrates


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Monosaccharides c chia ra aldoseshocketoses -ose tip v ngxc nh carbohydrate aldo-tip u ng xc nh nhm aldehyde carbonyl trong

ng keto- prefix xc nh nhm ketone carbonyl trong ng S nguyn t carbon c xc nh bi tip u ng ch s

tri-, tetra-, pent-, hex-

Phn loi Carbohydrates


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Chiu Fischer

c ngh bi Emil Fischer (1891) Phng php chiu carbon t din trn mt phng

Carbon t din c biu th bng 2 ng thng vunggc ct nhau

ng ngang ngoi trang giy ng thng ng sau trang giy

21.2 M t ha lp th Carbohydrate:Chiu Fischer


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Chiu Fischerca (R)-glyderaldehyde

Depicting Carbohydrate Stereochemistry:

Fischer Projections


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Nhng quy tc xoay chiu Fischer: Chiu Fischerc xoay trn giy 180, khng 90 hay

270

Ch xoay 180 duy tr quy c Fischer bng cch ginhng nhm th ging nhau bn trong hay bn ngoi mt

phng


Fischer Projections


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Xoay 90

ph v Fischerban u bng trao i cc nhmvo trong hay ngoi mt phng Xoay 90 hay 270thay i i vi enantiomer


Fischer Projections


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Mt cng thc chiu Fischerc th c mt nhm c gic nh trong khi ba nhm khc xoay theo chiu kim ngh hoc ngc chiu kim ng h Tc ng l quay n gin quanh lin kt n


Fischer Projections


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Ba bc xc nh cu hnh ha lp thR,S trong chiuFischer

1. Xc nh u tin i vi 4 nhm th theo cch thng

2. nhm u tin thp nht, thng H, nh ca cng

thc chiu Fischerbng cch dng mt trong nhng cchdi chuyn sau

Nhm u tin thp nht theo hng xa mt nginhn

3. Xc nh hng quay 123 ca 3 nhm cn li v xcnh cu hnhRhay S


Fischer Projections


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Carbohydrates nhiu hn mt trung tm bt i chirality

centerc th hin qua cng thc chiu Fischerbngcch xp cc trung tm theo th t trn nhau

Theo quy tc nhm carbonyl carbon lun lun c t nh hoc gn nh


Fischer Projections


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Assign RorS configuration to the following Fischer projection

of alanine:

Worked Example 21.1

Assigning RorS Configuration to a FischerProjection


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Chin lc

Theo cc bc lit k

1. Xc nh u tin ca 4 nhm th ca chiral carbon2. Xoay cng thc chiu Fischer t nhm u tin nh

nht ln nh bng cch thc hin mt thay i chophp

3. Xc nh hng 123 ca ba nhm cn li

Worked Example 21.1



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Gii Th t u tin (1)NH2, (2)CO2H, (3)CH3, v (4)H

nhm u tin nh nht (H ) nh, bng cch gi cnh nhm CH3trong khi xoay ba nhm khc ngcchiu kim ng h

Worked Example 21.1



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i t nhm u tin t ln n nh thy ngc chiu kimng h, tng ng cu hnhS

Worked Example 21.1



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Glyceraldehyde

Aldose n gin nht

C 1 tm bt i chirality center

Hai dng enantiomeric (mirror-image) Ch c dextrorotatory enantiomer ()-glyceraldehyde xy

ratrong t nhin

(+)-Glyceraldehyde c cu hnh R

(R)-(+)-glyceraldehyde cng l D-glyderaldehyde (D fordextrorotatory)

(S)-()-glyceraldehyde c bit nh l L-glyceraldehyde(L for levorotatory)

21.3 D,L Sugars


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Hu ht monosaccharides trong t nhin c cu hnh ha lp

th Rnh D-glyceraldehyde trung tm bt i chiralitycenter xa nhm carbonyl nht

Trong cng thc chiu Fischer hu ht cc ng trong t nhin cnhm hydroxyl bn phi gn vi trung tm bt i cui cng

Nhng hp cht nh th c bit lD

sugars

D,L Sugars


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L sugarsc cu hnh ha lp th S trung tm bt i xa nht so

vi nhm carbonyl NhmOH nm bn tri trong cng thc chiu Fischer Mt Lsugar l nh qua gng (enantiomer) ca mt D sugar tng ng

D v Lsugars c th l dextrorotatory hay levorotatory D v Lch cu hnh ha lp th chuyn bit ti mt tm bt i

xa nhm carbonyl nht

D,L Sugars


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Aldotetroses l nhng ng c 4 carbon vi hai trung tm

bt i v mt nhm aldehyde carbonyl 22 = 4 c th c ng phn lp th aldotetroses

Hai cpD,Lhoc cc enantiomers c t tn l erythrosev threose

Aldopentoses l nhng ng c 5 carbon vi ba trung tmbt i v mt nhm aldehyde carbonyl

23 = 8 c th c ng phn lp th aldopentoses Bn cp D,L enantiomers c t tnribose, arabinose,

xylose, and lyxose Nhng tt c ph bin l lyxose

D-Ribose mt thnh phn quan trng trong RNA

L-Arabinose c tm thy trong thc vt

D-Xylose c tm thy trong c thc vt v ng vt

21.4 Configurations of the Aldoses


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Aldohexoses l ng c 6 carbon vi 4 trung tm bt i

v mt nhm aldehyde carbonyl 24 = 16 ng phn lp th c th c ca aldohexoses

Tm cp D,L enantiomers c t tn l allose,altrose, glucose, mannose, gulose, idose, galactose,

and talose D-Glucose t bt v cellulose v D-galactose t gums

v fruit pectins c ph bin trong t nhin

Configurations of the Aldoses


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Cc cu hnh caD-aldoses

Cc nhm -OH bn phihay bn tri ca chui mchcarbon



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Nh tn v cu trc ca tm D aldohexoses: t tm cng thc chiu Fischervi nhm CHO nh v

nhmCH2OH cui

C5, t tm nhm OH bn phi (dy D)

C4, ln lt bn nhmOH bn phi, bn bn tri

C3, ln lt hai nhmOH bn phi, hai bn tri

C2, ln lt nhmOH phi, tri, phi, tri


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V chiu FischercaL-fructose.

Worked Example 21.2

V cng thc chiu Fischer


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Chin lc

V L-fructose l enantiomercaD-fructose, nhncu trc ca D-fructose v chuyn i cu hnh mi trung tm bt i.

Worked Example 21.2

Drawing a Fischer Projection


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Gii

Worked Example 21.2

Drawing a Fischer Projection

21 5 Nh t Monosaccharides:


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Aldehydes v ketones qua phn ng cng i nhn nhanh v thun

nghchvi alcohols to ra hemiacetals

Monosaccharides tri qua cc phn ng cng i nhn ni phn t Cc nhm carbonyl v hydroxyl trong mt phn t phn ng to ra vng

hemiacetals

21.5 Nhng cu trc vng ca Monosaccharides:Anomers

Cyclic Structures of Monosaccharides:


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Glucose trong dung dch tn ti dng vng 6 cnh, vng

pyranose l kt qu ca phn ng cng i nhn ni phn t ca

nhmOH C5 vi nhm carbonyl C1

Tn pyranose bt ngun t tnpyran

Pyran l tn ca ether vng 6 cnh khng bo ha Vng Pyranose c hnh lp th trng ging chic ghvi cc

nhm th hng axial v equatorial


Anomers



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Cc vng Pyranose c v theo cch t hemiacetal

oxygen v tr ra phi NhmOH hemiacetal c th trn hay di mt

phng vng Nhm cuiCH2OH trn mt phng vng l D sugars

v di mt phng vng l L sugars Khi mt chui monosaccharide ng vng to vng

pyranose mt trung tm bt i mi c hnh thnh carbonyl carbon trc Hai diastereomers c gianomersv nguyn t

carbon hemiacetal c xem nh l trung tm anomeric


Anomers


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Hai anomers c hnh thnh t s ng vng glucose

NhmOH ti C1 trong phn t mi c hnh thnh lcisi vi nguyn t oxygen carbon bt i thp nht (C5) trong cngthc chiu Fischer laanomer. Ngc li trans th lbanomer

Cyclic Structures of Monosaccharides: Anomers


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Mt s monosaccharides cng tn ti dng hemiacetal vng nmcnh c gi l furanose

D-Fructose tn ti chai dng pyranose v furanose Hai pyranose anomers kt qu ca cng nhm C6OH vi nhm

carbonyl C2

Hai furanose anomers kt qu ca cng nhm C5OH vi nhmcarbonyl C2

Cyclic Structures of Monosaccharides: Anomers



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C hai anomers caD-glucopyranose c th c

tinh th ha v tinh khit ha Pure a-D-glucopyranose

Melting point = 146 C

[a]D specific rotation = +112.2

Pureb-D-glucopyranose

Melting point = 148-155 C

[b]D specific rotation = +18.7


Anomers



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Khi mt mu anomerca D-glucopyranose tinh khit cha tan vo nc, s quay quang hc ca n thay ichm v t n gi tr hng s +52.6

S quay c bit caa-D-glucopyranose gim t+112.2 ti +52.6 khi c ha tan trong dung dch nc

S quay c bit cab-D-glucopyranose tng t +18.7n +52.6 khi c ha tan trong dung dch nc

S thay trong quay quang hc ny l v s chuyni chm ca cc anomers tinh khit theo t l hn hpcn bng 37 : 63 v c bit nh l mutarotation


Anomers



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Mutarotation ca D-

glucopyranose Mutarotation xy ra

bng s m vngthun nghch ca

mi anomeri vimch h aldehydec theo sau bis ng vng li

Mutarotation cxc tc bng cacid v base


Anomers


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D-Mannose khc viD-glucose trong ha lp th ti

C2. V D-mannose dng pyranose ging gh.

Worked Example 21.3

v cV cu dng gh ca Aldohexose


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Chin lc

Trc ht v cng thc chiu Fischerca D-mannose

n ng v tr v un n cong sao cho nhm CHO (C1) pha bn phi ng trc v nhm CH2OH (C6) phara tri

Ni OH C5 vi C1 nhm carbonyl to vng pyranose

Khi v dng gh nng carbon (C4) ln cao bn tri v kocarbon (C1) bn phi xung

Worked Example 21.3

Drawing the Chair Conformation of an

Aldohexose


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Gii

Worked Example 21.3


Aldohexose


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Vb-L-glucopyranose cu dng gh bn hn ca n

Worked Example 21.4


Aldohexose


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Chin lc

iu c th d nht bt u d nht v cu hnh dng

gh cab-D-glucopyranose Ri v nh qua gng L enantiomer bng s thay i ha

lp th mi v tr trn vng

Thc hin xoay vng cho cu dng gh bn hn

Ch rng nhm CH2OH di mt phng ca vngtrong L enantiomer

Worked Example 21.4


Aldohexose


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Gii

Worked Example 21.4


Aldohexose

21 6 R ti f M h id


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Ester and Ether Formation

Monosaccharides exhibit chemistry similar to

simple alcohols

Usually soluble in water but insoluble in organic

solvents Do not easily form crystals upon removal of water

Can be converted into esters and ethers

Ester and ether derivatives are soluble in organic

solvents and are easily purified and crystallized

21.6 Reactions of Monosaccharides

R ti f M h id


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Esterification is normally carried out by treating the

carbohydrate with an acid chloride or acid anhydride inpresence of base

AllOH groups react including the anomericOH group

Reactions of Monosaccharides

R ti f M h id


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Carbohydrates are converted into ethers by treatment with an

alkyl halide in the presence of base the Williamson ethersynthesis

Silver oxide (Ag2O) gives high yields of ethers without

degrading the sensitive carbohydrate molecules


R ti f M h id


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Glycoside Formation

Hemiacetals yield acetals upon treatment with an alcohol and anacid catalyst

Treatment of monosaccharide hemiacetals with an alcohol and

acid catalyst yields an acetal, called a glycoside


R ti f M h id


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Glycosides are named by first citing the alkyl group and then

replacing theose ending of the sugar withoside Glycosides are stable in neutral water and do not mutarotate

Glycosides hydrolyze back to free monosaccharide plusalcohol upon treatment with aqueous acid

Glycosides are abundant in nature Digitoxigenin used for treatment of heart disease


R ti f M h id


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Biological Ester Formation: Phosphorylation

Glycoconjugates

Carbohydrates linked through their anomeric center

to other biological molecules such as lipids

(glycolipids) or proteins (glycoproteins) Constitute components of cell walls and participate

in cell-type recognition and identification


R ti f M h id


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Glucoconjugate

formation occurs byreaction of the lipid or

protein with a glycosyl

nucleoside

diphosphate Glycosyl nucleoside

diphosphate is initially

formed by

phosphorylation of

monosaccharide withATP to give glycosyl

phosphate


R ti f M h id


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Reaction with UTP

forms a glycosyluridine 5-diphosphate

Nucleophilic

substitution by anOH (orNH2)group on a protein

then gives the

glycoprotein


R ti f M h id


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Reduction of Monosaccharides

Treatment of an aldose or ketose with NaBH4 reduces it to a polyalcoholcalled an alditol

Reduction occurs by reaction of the open-chain form present in

aldehyde/ketone hemiacetal equilibrium

D-Glucitol, also known as D-sorbitol, is present in many fruits and

berries and is used as a sweetener and sugar substitute




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Oxidation of Monosaccharides

Aldoses are easily oxidized to yield corresponding carboxylicacids called aldonic acids

Oxidizing agents include:

Tollens reagent(Ag+ in aqueous NH3)

Gives shiny metallic silver mirror on walls of reactiontube or flask

Fehlings reagent(Cu2+ in aqueous sodium tartrate)

Gives reddish precipitate of Cu2O

Benedicts reagent(Cu2+ in aqueous sodium citrate) Gives reddish precipitate of Cu2O

(All three reactions serve as simple chemical tests forreducing

sugars)




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Fructose is a ketose that is a reducing sugar

Undergoes two base-catalyzed keto-enol tautomerizations thatresult in conversion to a mixture of aldoses (glucose and

mannose)




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Br2 is a mild oxidant that gives good yields of aldonic acid

products Preferred over Tollens reagent because alkaline conditions

in Tollens oxidation cause decomposition of thecarbohydrate




52/74

Aldoses are oxidized in warm, dilute HNO3 to dicarboxylic

acids called aldaric acids Both theCHO group at C1 and the terminalCH2OH group

are oxidized




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Enzymatic oxidation at theCH2OH end of aldoses yields

monocarboxylic acids called uronic acids No affect on theCHO group


21 7 The Eight Essential Monosaccharides


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Humans need to obtain

eightmonosaccharides for

proper functioning

All are used for

synthesis ofglycoconjugate

components of cell

walls

21.7 The Eight Essential Monosaccharides

The Eight Essential Monosaccharides


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Fucose is a deoxy sugar

TheOH group at C6 is replaced byH N-Acetylglycosamine and N-acetylgalactosamine are amide

derivatives ofamino sugars

TheOH group at C2 is replaced by anNH2 group

N-Acetylneuraminic acid is the parent compound ofsialicacids




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All eight essential monosaccharides all synthesized from D-

glucose Galactose, glucose, and mannose are simple aldohexoses

Xylose is an aldopentose


21 8 Disaccharides


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Cellobiose and Maltose

Disaccharides contain a glycosidic acetal bond

between the anomeric carbon of one sugar and

anOH group at any position on another sugar

A glycosidic bond between C1 of the first sugarand theOH at C4 of the second sugar is acommon glycosidic link called a 14 link

21.8 Disaccharides

Disaccharides


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Maltose consists of two a-D-

glucopyranose units joinedby a 14-a-glycoside bond

Maltose is the

disaccharide obtained

by enzyme-catalyzed

hydrolysis of starch

Cellobiose consists of twob-

D-glucopyranose units

joined by a 14-b-

glycoside bond Cellobiose is the

disaccharide obtained

by partial hydrolysis of

cellulose

Disaccharides

Disaccharides


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Maltose and cellobiose are both reducing sugars because

the anomeric carbons on the right-hand glucopyranose unitshave hemiacetal groups and are in equilibrium with the

aldehyde forms

Maltose and cellobiose also exhibit mutarotation ofaand

banomers Maltose is digested by humans and is fermented readily

by yeast

Cellobiose cannot be digested by humans and is not

fermented by yeast

Disaccharides

Disaccharides


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Lactose

Lactose is a disaccharide that occurs naturally in humanand cows milk

Lactose is a reducing sugar and exhibits mutarotation

Lactose contains a 14-b-link between C1 of galactose and

C4 of glucose

Disaccharides

Disaccharides


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Sucrose

Sucrose is ordinary table sugar and is among the mostabundant pure organic chemicals in the world

Sucrose is obtained from sugar cane (20% sucrose by weight)

or from sugar beets (15% sucrose by weight)

Sucrose is a disaccharide that consists of 1 equivalent ofglucose and 1 equivalent of fructose

1:1 mixture often referred to as invert sugarbecause the sign

of optical rotation inverts (changes) during hydrolysis from

sucrose ([a]D = +66.5) to a glucose/fructose mixture ([a]D = -

22.0) Honeybees have enzymes called invertases that catalyze the

hydrolysis of sucrose

Honey is primarily a mixture of sucrose, glucose, and fructose

Disaccharides

Disaccharides


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Sucrose is not a reducing sugar and does not undergo

mutarotation Glucose and fructose are joined by a glycoside link at the

anomeric carbons of both sugars, C1 of glucose and C2 of

fructose

Disaccharides

21 9 Polysaccharides and Their Synthesis


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Polysaccharides are complex carbohydrates in which tens or

even thousands of simple sugars are linked togetherthrough glycoside bonds

Only one free anomericOH on end of long polymeric chain

Not reducing sugars

Do not exhibit noticeable mutarotation Cellulose and starch are the two most widely occurring

polysaccharides

21.9 Polysaccharides and Their Synthesis

Polysaccharides and Their Synthesis


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Cellulose

Cellulose consists of several thousand D-glucose unitslinked by 14-b-glycoside bonds like those in cellobiose

Used by nature to impart strength and rigidity to plants

Used commercially as raw material for cellulose acetate

(acetate rayon) and cellulose nitrate (guncotton) themajor ingredient of smokeless gun powder




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Starch and Glycogen

Starch is a polymer of glucose found in potatoes, corn, andcereal grains

Monosaccharide units are linked by 14-a-glycosidebonds like those in maltose

Starch is separated into two fractions: Amylose accounts for about 20% by weight of starch

Amylopectin accounts for about 80% by weight of starch

Amylopectin is nonlinear and contains 16-a-glycoside

branches approximately every 25 glucose units




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Starch is digested in the mouth and stomach by a-glycosidase enzymes

which catalyze the hydrolysis ofa-glycoside links but leave theb-

glycoside links in cellulose untouched

Humans can digest potatoes and grains but cannot digest

grasses and leaves

Glycogen is a polysaccharide that serves as long-term storage of energy

for the human body Glycogen contains both 14 and 16 links




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Polysaccharide Synthesis

Glycal assemble method A glycal is an unsaturated sugar with a C1-C2 double

bond

The C6OH group is protected as a silyl ether (R3Si-O-R)

The C4 and C3OH groups are protected as a cycliccarbonate ester

Carbons C1 and C2 are epoxidized




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Treatment of the protected glycal with another glycal

containing a free C6OH group in the presence of ZnCl2yields a dissacharide

The dissacharide can be epoxidized and treated with a third

glycal to yield a trisaccharide

Process is continued to prepare a polysaccharide




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Lewis Y hexasaccharide

Synthesized complex polysaccharide Tumor marker that is currently being explored as a potential

cancer vaccine


GlcGal

GalGlcNAc

21.10 Cell-Surface Carbohydrates andC b h d t V i


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Small polysaccharide chains

covalently bound by glycosidiclinks toOH orNH2 groups onproteins act as biochemicalmarkers on cell surfaces

If human blood from one donor

type (A, B, AB, or O) istransfused into a recipient withanother blood type the red bloodcells clump together, oragglutinate

Agglutination results from thepresence of polysaccharidemarkers on the surface of thecells

Carbohydrate Vaccines

Cell-Surface Carbohydrates and CarbohydrateV i


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Types A, B, and O red blood cells each have their own

unique markers, orantigenic determinants, and type AB redblood cells have both A and B markers

Vaccines

Summary of Reactions


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Summary of Carbohydrate Reactions

Summary of Reactions

carbohydrate fischer projection vn

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