Post on 31-Dec-2015
description
Converting Fischer Converting Fischer structures to Haworth and structures to Haworth and chair formschair forms
Start with the Fischer Start with the Fischer (Rosanoff) structure(Rosanoff) structure
D-glucose
Form the pyranose ringForm the pyranose ring
D: CHD: CH22OH at C5 goes upOH at C5 goes up
L: CHL: CH22OH at C5 goes downOH at C5 goes down
O5
This is a D-sugarThis is a D-sugar
O
H
CH2OH
Determine alpha or Determine alpha or betabeta
If OH at C1 is on the same side If OH at C1 is on the same side of the ring as the CHof the ring as the CH22OH group, OH group, the sugar is betathe sugar is beta
If the OH at C1 is on the If the OH at C1 is on the opposite side of the ring as the opposite side of the ring as the CHCH22OH group, the sugar is alphaOH group, the sugar is alpha
Let’s make our example betaLet’s make our example beta
The beta anomerThe beta anomer
O
H
HOH
CH2OH Same side
What remains to be What remains to be done?done?
We need to know the We need to know the configuration of the OH groups configuration of the OH groups at carbons 2, 3, and 4at carbons 2, 3, and 4
How do we do this?How do we do this? Go back to the Fischer Go back to the Fischer
(Rosanoff) projection(Rosanoff) projection Then lay it over on it’s side to Then lay it over on it’s side to
the rightthe right
Fischer structureFischer structure
D-glucose
Place remaining OH Place remaining OH groupsgroups
Put the remaining OH groups Put the remaining OH groups on the Haworth ring at C2, C3, on the Haworth ring at C2, C3, and C4 in the same orientation and C4 in the same orientation (up or down) as they are in the (up or down) as they are in the leaned over Fischer/Rosanoff leaned over Fischer/Rosanoff structurestructure
Beta-D-glucopyranoseBeta-D-glucopyranose
O
HH
HH
OHOH
H OH
OH
CH2OH
Haworth to chair formHaworth to chair form
O
HH
HH
OHOH
H OH
OH
CH2OH
O
HOH
HH
H
H
OHOH
OHHOH2Ce
ae
a
a
e
e
a
a
e
beta-D-glucopyranose
(Haworth form)
beta-D-glucopyranose
4C1 chair form