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680 Chapter 20
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b.
When d-sorbose is reduced, C-2 becomes an asymmetric center, so both d-iditol and the C-2 epimer of
d-iditol (d-gulitol) are formed.
CH
2
OH
C
CH
2
OH
OH H
H HO
OH H
D
-sorbose
CH
2
OH
CH
2
OH
H HO
OH H
H HO
OH H
D
-iditol
O
CH
2
OH
CH
2
OH
OH H
OH H
H HO
OH H
D
-gulitol
+
1. NaBH
4
2. H
3
O
+
13.
a. 1.
d-Altrose is reduced to the same alditol that d-talose is reduced to. The easiest way to answer this
question is to draw d-talose and its alditol. Then draw the monosaccharide with the same configu-
ration at C-2, C-3, C-4, and C-5 as d-talose, reversing the functional groups at C-1 and C-6. (Put
the primary alcohol group at the top and the aldehyde group at the bottom.) When this structure is
rotated 180
°
in the plane of the paper, the monosaccharide can be identified.
CH
2
OH
H HO
H HO
H HO
OH
H
D
-talose
the alditol of
D
-talose
CH
2
OH
CH
2
OH
H HO
H HO
H HO
OH H
CH
2
OH
H HO
H HO
H HO
OH H
CH
2
OH
H HO
OH
H
OH
H
OH
H
D
-altrose
rotate 180
°
C
H O
C
H O
C
H O
1. NaBH
4
2. H
3
O
+
1. NaBH
4
2. H
3
O
+
2.
l-Gulose is reduced to the same alditol that d-glucose is reduced to.
OH H
H HO
OH H
OH H
CH
2
OH
CH
2
OH
OH H
H HO
OH H
OH H
CH
2
OH
CH
2
OH
OH H
H HO
OH H
OH H
C
H O
rotate 180
°
D
-glucose
the alditol of
D
-glucose
L
-
gulose
C
H O
H HO
H HO
OH H
H HO
CH
2
OH
C
H O
1. NaBH
4
2. H
3
O
+
1. NaBH
4
2. H
3
O
+