Download 108B Carbohydrate Activity KEY

Carbohydrate Nomenclature Worksheet KEY
CHEM 8B, UCSC, Binder
1. Draw one example of each of the following types of monosaccharides (there may be several
correct answers) and indicate the number of possible stereoisomers while keeping the same D/L
configuration.
(a) D-Aldotriose
(c) L-Ketotetrose
(b) L-Aldotriose
CHO
H
OH
CH2OH
CHO
HO
H
CH2OH
1 possible
1 possible
CH2OH
C O
HO
H
CH2OH
1 possible
4 possible
(d) L-Aldopentose
CHO
CHO
CHO
HO
H
H
OH
H
OH
H
OH
HO
H
H
OH
HO
H
HO
H
HO
H
CH
CH2OH
CH2OH
2OH
CHO
HO
H
HO
H
HO
H
CH2OH
(e) D-Ketohexose
4 possible
CH
OH
CH2OH
CH2OH
2
C O
C O
C O
H
OH
H
OH
HO
H
H
H
OH HO
H
OH
H
OH
H
OH
H
OH
CH
OH
CH2OH
CH2OH
2
(f) L-Aldohexose
H
H
H
HO
CHO
OH
OH
OH
H
CH2OH
H
H
HO
HO
CHO
OH
OH
H
H
CH2OH
H
HO
H
HO
CHO
OH
H
OH
H
CH2OH
H
HO
HO
HO
CH2OH
C O
HO
H
HO
H
H
OH
CH2OH
ANY ONE EXAMPLE IS CORRECT
FOR (d), (e), & (f).
I WOULDN'T EXPECT YOU TO
DRAW ALL STEREOISOMERS
ON AN EXAM!
8 possible
CHO
CHO
CHO
OH
HO
H
HO
H
H
H
OH
H
OH
H
H
OH HO
H
H
HO
H
HO
H
CH2OH
CH2OH
CH2OH
HO
HO
H
HO
CHO
H
H
OH
H
CH2OH
HO
HO
HO
HO
CHO
H
H
H
H
CH2OH
2. What is the relationship between the following monosaccarides (enantiomers, diastereomers,
or epimers)? You’ll find the structures of D-monosaccharides in chapter 25. You should be able
to figure out the structures of the corresponding L-monosaccharides if you’re paying attention to
the reading! The only monosaccharide you’re expected to memorize for exams is D-glucose.
a.
b.
c.
d.
D-glucose and L-glucose ARE ENANTIOMERS
D-glucose and D-allose ARE C3 EPIMERS (more specific than diastereomers)
D-allose and D-altrose ARE C3 EPIMERS (more specific than diastereomers)
D-altrose and D-glucose ARE DIASTEREOMERS (more than one chiral center is
different)
e. D-glucose and D-mannose ARE C2 EPIMERS (more specific than
diastereomers)
f. L-glucose and D-idose ARE C5 EPIMERS (more specific than diastereomers)
Carbohydrate Nomenclature Worksheet KEY
CHEM 8B, UCSC, Binder
3. Fischer projections of D-glucose’s epimers
D-Glucose
H
HO
H
H
CHO
OH
H
OH
OH
CH2OH
CHO
H
H
OH
OH
CH2OH
C2 epimer
HO
HO
H
H
CHO
OH
OH
OH
OH
CH2OH
C3 epimer
H
H
H
H
CHO
OH
H
H
OH
CH2OH
C4 epimer
H
HO
HO
H
4. Monosaccharides can act as nucleophiles and/or electrophiles. Redraw any sugar from #1d
and #1e and indicate the functional groups that could act as nucleophiles and those that can
serve as electrophiles.
alcohol = nucleophile
aldehyde = electrophile
CHO
H
OH
H
OH
4 alcohols = nucleophiles
HO
H
CH2OH
CH2OH
C O ketone = electrophile
H
OH
H
OH
4 alcohols = nucleophiles
H
OH
CH2OH
5. Redraw the following structures exactly. These are the backbone structures to be used for #6
of this worksheet. Pay special attention to the placement of the oxygen and the particular chair
conformation used (no ring flips necessary!).
O
Haworth
projection
O
Chair
conformation
(NO KEY SHOULD BE NECESSARY!)
6. Draw Haworth projections and the chair conformation for the following aldohexoses using the
backbone structures from #5. Consult Fig 25.3 of McMurry; memorize the structure of DGlucose for the final exam.
Left or right side on Fischer projection
If it were LEFT UP to me, I'd be DOWN RIGHT angry * works for C2 through C4 *
Pointing up or down on the ring (Haworth or chair)
Carbohydrate Nomenclature Worksheet KEY
(a)
CHEM 8B, UCSC, Binder
Chair
Haworth
The C5 CH2OH (penultimate) group always points "up" for D-sugars
Bonds in Haworth
projections are
HO
up/down only,
no axial or equatorial,
no wedge/dash
4
1
CHO
H 2 OH
H 3 OH
H 4 OH
H 5 OH
6 CH 2OH
6
OH
C1-C4 are "down" but
alternate axial-equatorial.
5
O
5
Take special note of the
HO
1
2
angles of the equatorial
2
1
3
HO 3
OH
groups - parallel to bonds
OH
in the ring.
OH
OH
OH OH
C1 OH (anomeric) points "down" for alpha (α)
D-Allose
O
6
4
α-D-Allopyranose
(b)
HO
6
OH
O OH
5
4
2
2
3
O
5
HO
1
HO
6
4
3
OH
OH
1
OH
OH OH
Everything except C1 is the same as part (a)
β-D-Allopyranose
(c)
1
HO
CHO
H
OH
3
HO
H
H 4 OH
H 5 OH
6 CH 2OH
6
OH
2
5
4
O
4
2
HO
HO
1
OH
HO
3
OH
6
O
5
2
OH
3
OH
1
OH
Everything except C3 is the same as part (a)
α-D-Glucopyranose
D-Glucose
(d)
HO
6
OH
O OH
5
4
1
OH
2
HO
6
4
HO
HO
2
OH
OH
3
3
Hey, look at that!
They're all equatorial!
Notice that equatorial
bond angles still point
up or down, not
horizontally
O
5
1
OH
Everything except C1 is the same as part (c)
β-D-Glucopyranose
(e)
1
CHO
2
HO
H
H 3 OH
HO 4 H
H 5 OH
6 CH 2OH
D-Idose
(f)
HO
HO
OH OH
6
O
5
4
3
4
OH1
OH
2
OH
6
5
3
O
OH
2
OH
C2 and C4 differ from part (a)
α-D-Idopyranose
HO
6
HO
5
4
OH OH
6
O OH4
5
1
HO
3
1
OH
2
OH
3
O
OH
2
OH
1
OH
Everything except C1 is the same as part (e)
α-D-Idopyranose