Reactivity

of

carbohydrates

:

Hemiacetalstttemiketals

OH

HO

-

RS

OR3

Aldehyde

+

ketone

carbons

are

electrophilic

R'

-

Cy

,

1-1-10

-

R2

#

R'

-

¢-0B

'

Rtd

-

OR

-

+

HOH

H

14

Alcohol

oxygen

atom

is

nucleophilic

Aldehyde

Alcohol

Hemiacetal

"

°

-

Rˢ

Acetal

Aldehydes

attacked

by

alcohols

(

Hemlacetais

)

FH

Ho

-

R

"

ketones

attacked

by

alcohols

(

Hemiketals

)

Rt

,C=o

-140

-

Rˢ-_

R'

-

g-

OR3¥-RL§%R3+

HOH

R2

R2

2

Basis

of

cyclization

of

sugars

ketone

Alcohol

Hemiketal

"

°

-

R

"

Keta

/

Cyclization

of

Monosaccharides

ki

i

H

-

G

-

OH

1.

Nucleophilic

alcohol

attacks

electrophilic

carbonyl

carbon

.

>

allows

formation

Ofahemlacetal

+10-34-1-1

D-Glucose

H

-

OH

2.

linear

carbs

forma

ring

structure

chair

forms

of

B-

Dglucopyranose

1-1-54

-

OH

GCHZOH

3.

At

completion

,

carbonyl

carbon

is

reduced

-10

an

alcohol

Axis

CHZOH

'

GCHZOH

1

,

&

-

OH

orientation

of

alcohol

around

carbon

is

variable

and

transient

1%1

,

"

↳

a

,H

¥÷÷-%÷

:

"

HAP

"

'

i'

/

%

Pentoses

+

hexoses

readily

undergo

intramolecular

cyclization

OH

¥

,

-4

OH

Axis

former

carbonyl

carbon

becomes

achiral

center

/

anomeric

carbon

)

H

¢2

.

×

¥-9

{

HZOH

GCHZOH

Position

determines

lftheancmterlsa

"B

-14

,

"

°

,¥oµ

f-

◦

µ

¥

-

◦

µ

Hac

-

CH

¥1,4

IF

%

,

1T¥

Hydroxyl

group

on

the

opposite

side

(

trans

)0f+he

Pyran

µ

Ci

4C

1191-1

↑

/

+

,

3

.

+1101%1%1%-1

ring

as

CHZOH

moiety

;

configuration

Isai

/

◦

"

◦

§

-24

31

21

HC

\

CH

H

OH

H

OH

"

"

c-

c

a-

D

Ghlcopyranose

B-

DG

/

ucopyranose

Hydroxyl

group

on

the

same

side

(

Cis

)

ofthe

H

H

Furan

nngasctl.CH

moiety

;

configuration

/

SB

pypanoses

and

Futa

noses

cyclohexane

rings

→

"

chair

"

/

'

boat

"

conformations

six

membered

oxygen

-

containing

rings

→

pyranoseslpyranring

structure

)

Pyranose

rings

→

"

chair

"

conformations

five

membered

oxygen

-

containing

rings

→

furanoseslfuranring

Structure

)

Multiple

"

chair

"

conformations

possible

;

require

energy

for

anomeric

carbon

→

usually

drawn

on

the

right-side

interconversion

(

~

46kg

/

mole

)

GCHZOH

4-

◦

Ii

,

Hexoses

Derivatives

HOÉHZ

O

'

CHZOH

4

HOTH

Glucose

fam

"

's

amino

sugars

31=-1*01-1

¥¥,=

CHZOH

CHZOH

CHZOH

CHZOHO

%

"

H

OH

+1041¥

:*

no

¥IÉ¥"É¥i

"

"

¥-4

"

+p¥µ*

F-↑

"

HYLE

!

+10*4/+1

A-

D-

Glllcopyranose

a-

-

D-

Frcictofclranose

H

MHz

H

NH

H

MHz

H

H

£-0

B-

D-

Galactosamine

B-

D-

Mariposa

mine

CHZOH

B-

D-

Glucose

B-

D

Glucosamine

N

-

acetyl

-

B-ᵈÑ

?

glucosamine

peony

sugars

t_§H

Cttz

-

O

-

POI

i

o

"

"

%

"

1¥

.cn

,

¥-10k

1*-201-1

t

¥404

9+3

¥4

+10,1%+50>101-1

Fats

1-10*+1=-11%-1

coo

-

H0\↑¥↓H

HY

H

HÑ¥É

1-104-7

it

Ho¥y¥¥

"

-0-9-1-1

H

OH

H

MHz

OH

H

OH

OH

H

OH

OH

H

B-

b-

Glucose

{

󲰛

B-

D-

Glclcopyranose

B-

p

-

Frllctofclranose

6-

phosphate

Murano

acid

N-Acety.IM#ramicaold

B

-

L

-

Fucose

a-

-

L

-

Rhamnose

¥

Acidic

sugars

HC

/

°

CH

4+3

%

-

°

'

CHZOH

0=4

H

°¥°

'

HC

)

H

yɱ%

"

-0-+1×1-4=0

+1*91

"

=

+1-4-0+1

Hzc

-

c

#

"

Fi

-

Fi

HÑH

H0\FF%

H0↑↑

+14%+01-1

H

-

g-

OH

H

th

H

OH

H

OH

OH

H

b-

☐

Glllcclronate

D-

Gluconate

D-

Glucono

-

g-

lactone

N

-

acetylneuraminicacid

"

KOH

Pyran

Furan

(

astatic

acid

)