Fall 2014���

Armen Zakarian�Office: Chemistry Bldn 2217!

Chem 109 C �

http://web.chem.ucsb.edu/~zakariangroup/courses.html!

Carbohydrates: Fischer projections manipulation of Fischer projections:�

OOHHOHHOHHOH

D-ribose �

OHO HHO HHO HHO

also D-ribose �

Carbohydrates: Fischer projections

manipulation of Fischer projections:�

OOHHOHHOHHOH

D-ribose �

OHO HHO HHO HHO

also D-ribose � not D-ribose �

O OH

H

OH

H

OH

H

OH

an alditol�

Carbohydrates: Reactions with Bases O

RRO-

RH

R

H HB: + B-H

fundamental reactivity!

base-catalyzed epimerization: D-glucose and D-mannose �

enolate formation:Section 18.2

Carbohydrates: Reactions with Bases O

RRO-

RH

R

H HB: + B-H

fundamental reactivity!

base-catalyzed enediol rearrangement: D-glucose and D-fructose �

Carbohydrates: Reduction fundamental reactivity!

O

R R

O-

R RH-: H

an alditol�

Carbohydrates: Reduction fundamental reactivity!

O

R R

O-

R RH-: H

Carbohydrates: Reduction fundamental reactivity!

O

R R

O-

R RH-: H

Carbohydrates: Oxidation

an aldonic acid�

Carbohydrates: Oxidation

“Tollens test”

Carbohydrates: Oxidation

an aldaric acid�

“Tollens test”

Carbohydrates: Oxidation

PROBLEM 9� Show how an enediol rearrangement can move the

carbonyl group of fructose from C-2 to C-3�

OOH

HHOOHHOHHOH

D-fructose �

Carbohydrates: Lengthening the Chain fundamental reactivity!

OR

RC N+ -O

R

R

N Kiliani-Fischer synthesis:

Steps/Reagents: 1. NaCN, HCl; 2. H2, Pd/BaSO4

3. HCl, H2O

Carbohydrates: Shortening the Chain fundamental reactivity!

Wohl degradation: OR

RC N+-O

R

R

N

OAcHHAcO

N

H OAcOAcHOAc

H OAc

Steps/Reagents: 1. NH2OH; H+ 2. Ac2O, 100 oC

3. NaOH, H2O