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Chapter 7: Outline. Monosaccharides Monosaccharide stereoisomers Cyclic structures Reactions Examples and derivatives Di and oligosaccharides Polysaccharides Homo and heteropolysaccharides Glycoconjugates.

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Chapter 7 outline l.jpg
Chapter 7: Outline

Monosaccharides

Monosaccharide stereoisomers

Cyclic structures

Reactions

Examples and derivatives

Di and oligosaccharides

Polysaccharides

Homo and heteropolysaccharides

Glycoconjugates


Slide2 l.jpg


7 1 monosaccharides l.jpg
7.1 Monosaccharides formula C

polyhydroxy

Number of carbons

Aldehydes

are aldoses

Ketones

are

ketoses

3=triose

4=tetrose

5=pentose

6=hexose


Monosaccharides generic names l.jpg
Monosaccharides: generic names formula C

  • The generic name for a simple sugar begins with the carbonyl prefix aldo or keto and ends with the term for the number of carbons.

  • An aldose with three carbons is called an aldotriose. A ketose with three carbons is a ketotriose.

What is the name for a six carbon

aldehyde sugar?

aldohexose

What is the name for a five carbon

ketone sugar?

ketopentose


Dihydroxyacetone l.jpg
Dihydroxyacetone formula C

  • Dihydroxyacetone

Is a ketotriose


Glyceraldehyde l.jpg
Glyceraldehyde formula C

Glyceraldehyde

Is an aldotriose

Glyceraldehyde exists in two

stereoisomeric forms because the

starred carbon is a stereocenter: it has

four different groups attached.


Slide7 l.jpg

stereocenter formula C

  • The stereoisomers of glycer-aldehyde are designated D or L. The D isomer has the OH on the stereocenter to the right. The L isomer has the OH on the left .


Glyceraldehyde 3 l.jpg
Glyceraldehyde: 3 formula C

  • The stereoisomeric forms of glycer-aldehyde are enantiomers: nonsuper-imposable mirror image molecules.

  • Perspective drawings of the two enantiomers of glyceraldehyde are on the next slide. A stereo view is on slide 11.

  • Remember, barred bonds ( ) recede behind the plane of the screen and wedge ( ) bonds project in front of the plane.


Perspective view l.jpg
Perspective View formula C


Slide10 l.jpg

View with blue lens on the left eye. formula C

Carbonyl group

OH group

H atom

CH2OH group

Stereoscopic view of glyceraldehyde


Fischer projections l.jpg
Fischer Projections formula C

  • In a Fischer projection, the sugar molecule is oriented so that the most oxidized carbon is to the top. The stereocenter carbons are arranged so that the groups not part of the main chain project horizontally toward the viewer.

  • The molecule is in the all eclipsed form.


Slide12 l.jpg

  • Monosaccharides are drawn in Fischer projections with the most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

  • Most common sugars are in the D form.

  • Note: Fisher projections represent an all eclipsed conformation.


Slide13 l.jpg

1 most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

2

1

2

3

3

4

4

5

5

6


Slide14 l.jpg

These diastereomers are also most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.epimers, they

differ in configuration at only one stereo-

center (colored dot).


Cyclic forms for sugars l.jpg
Cyclic forms for sugars most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

  • Most simple sugars of four or more carbons exist in the cyclic (hemiacetal or hemiketal) form.

  • A hydroxy group in the sugar reacts with the carbonyl group.

  • The new OH bearing carbon is now a stereo center and is called an anomeric carbon.

  • If the OH on the ring is “up” the carbon is b, if the OH is “down” it is a.


Cyclic forms for sugars 2 l.jpg
Cyclic forms for sugars-2 most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

  • Fischer projections for a D glucose


Cyclic forms for sugars 3 haworth l.jpg
Cyclic forms for sugars-3 Haworth most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

  • 1. Draw a five- or six-membered ring

2. Anomeric C to right of O. Place OH up or down. Left on Fischer, up on ring.

3. In D- sugars, the last C is always up.


Cyclic forms for sugars 4 haworth l.jpg
Cyclic forms for sugars-4 Haworth most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

Anomeric C

b-OH


Cyclic forms for sugars 5 glucose l.jpg
Cyclic forms for sugars-5 Glucose most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

Pyranose

ring form


Cyclic forms for sugars 6 l.jpg
Cyclic forms for sugars-6 most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

  • The alpha and beta forms of cyclic sugars are said to be anomers. They differ in configuration about the hemiacetal or hemiketal carbon.


Cyclic forms for sugars 7 l.jpg
Cyclic forms for sugars-7 most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

  • Ribose also exists mainly in the cyclic form.


A d glucose the chair conformer l.jpg
a most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L. D-glucose: the chair conformer

Four of the five bulky groups (OH and CH2OH on C 2,3,4,5)

on the ring are in the more stable equitorial positions!


Oxidation of monosac charides l.jpg
Oxidation of most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.Monosaccharides

+ Ag(mirror)

Ag(NH3)2+

Cu2+

+ Cu2O (red-orange)

Benedict’s reagent (a blue copper ion solution) also gives a

lactone. The blue color fades as reaction occurs.

Aldoses react with Tollen’s reagent (Ag(NH3)2+) to give a

lactone (cyclic ester). The silver ion plates out as a mirror.


Slide24 l.jpg

Oxidation of Monosaccharides-2 most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

Term CH2OH oxid’n

uronic acid

  • Aldehyde oxid’n

  • aldonic acid


Oxidation of monosac charides 3 l.jpg
Oxidation of most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.Monosaccharides-3

  • Aldehyde + term CH2OH oxid’n 

  • aldaric acid


Reduction of monosaccharides l.jpg
Reduction of Monosaccharides most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

The most important reduced sugar is deoxyribose. (In DNA)

When the carbonyl of a sugar is reduced to an alcohol, alditols are produced. The two shown above are used to sweeten nonsugar gum.


Isomerization l.jpg
Isomerization most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

  • Isomerization of mono-

  • saccharides occurs

  • through an enediol.


Esters of monosaccharides l.jpg
Esters of Monosaccharides most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

  • The OH groups of sugars can react with phosphoric acid to give phosphate esters.


Glycosides l.jpg
Glycosides most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.

Acetal link: R-O-C-O-R

Acetal

carbon

  • The anomeric OH can react with another OH on an alcohol or sugar. Water is lost to form an acetal/ketal


Important monosaccharides l.jpg
Important Monosaccharides most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.


Amino sugars l.jpg
Amino Sugars most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.


Amino sugars 2 l.jpg
Amino Sugars-2 most oxidized carbon closest to the top. The carbons are numbered from the top. If the the stereocenter with the highest number has the OH to the right, the sugar is D. If the OH is to the left, the sugar is L.


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