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Solutions for Carbohydrates and Nucleic Acids
CH2OH
H OH
H OH
CHO
HO H
OHH
OHH
CHO
OHH
OHH
CH2OH
OHH
Ph
NHCH3H
CH3
CH2OH
H OH
HO H
CHO
HO H
H OH
HHO
CHO
OHH
HHO
CH2OH
CH3
H3CHN H
Ph
HO H
CH2OH
H OH
HO H
CHO
HO H
HO H
OHH
Ph
HH3CHN
CH3
O H
OH
H
H
OH
H
HO
HO
H
CH2OH
HHO
HHO
CHO
OHH
OHH
CH2OH
CH3
H NHCH3
Ph
HO H
7 (a) continued: stereochemical view
1 2 3 4
(b) Ephedrine is the erythro diastereomer, represented by structures 1 and 2. Structures 3 and 4 represent 
pseudoephedrine, the threo diastereomer.
(c) The Fischer-Rosanoff convention assigns D and L to the configuration of the asymmetric carbon at the 
bottom of the Fischer projection. Structure 1 is D-ephedrine; structure 2 is L-ephedrine; structure 3 is L-
pseudoephedrine; and structure 4 is D-pseudoephedrine.
(d) It is not possible to determine which is the (+) or (–) isomer of any compound just by looking at the 
structure. The only compound that has a direct correlation between the direction of optical rotation and its D 
or L designation is glyceraldehyde, about which the D and L system was designed. For all other 
compounds, optical rotation can only be determined by measurement in a polarimeter.
33
2
inversion at bottom chiral center ⇒ 
L-series sugar4
8
(a) (b) (c)
D-allose D-talose D-idose
(d)
D-xylose L-arabinose
6
6
5
5
44
3
3
2
2
1
1
9 D-mannose
rotate
599

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