Name_______________________________
215 F12-Exam No. 3
Page 2
I. (26 points) Raffinose is a trisaccharide occurring in cottonseed meal. Answer the following questions as
directed in the boxes.
(1) (3 points) Label each of the glycosidic bonds in
raffinose using a small arrow (
).
HO
(2) (3 points) Classify each glycosidic bond in raffinose
as α or β right next to each of the arrows you have shown.
H
no (circle one)
HO
1
2
1
2
CH2
O
H
3 (circle one)
3
H
H
OH
H
H
OH
HO
H
HO
HO
H
H
(circle one)
(6) (2 points) Describe the glycosidic linkage between the sugar
units B and C [e.g., β(1->6)]:
O
O
HOH2C
(5) (2 points) How many reducing sugars are formed upon
complete acid hydrolysis of raffinose?
0
O
B
(4) (2 points) How many D sugars are formed upon complete
acid hydrolysis of raffinose?
0
A
H
H
(3) (2 points) Is raffinose a reducing sugar?
yes
CH2OH
O
H
H
OH
CH2OH
C
raffinose
14
(7) (12 points) Draw Fischer projections for the open chain forms of the carbohydrates produced when
raffinose is treated with excess dimethyl sulfate and NaOH, and then the permethylated product is
hydrolyzed with warm dilute acid.
raffinose
(C18H32O16)
(CH3)2SO4
(excess)
permethylated
raffinose
(C29H54O16)
From sugar unit B
From sugar unit A
NaOH
(excess)
H2O
(solvent)
H3O+
H2O
From sugar unit C
+
Δ
4
+
4
4
Name_______________________________
215 F12-Exam No. 3
Page 3
II. (8 points) Narbosine is a naturally occurring disaccharide. It is a dimer of L-rhodinose (as pyranose
forms) joined together by an α(1→4) glycosidic linkage. Draw in the box below the structure of narbosine
having the equatorial anomeric OH, using a conformational representation.
O
H
2
H
H
H
HO
H
H
OH
H
CH3
L-rhodinose
8
III. (14 points) Vancosamine is a small portion of vancomycin, one of the most powerful antibiotics that are
effective against drug-resistant bacteria. Show in the boxes provided below: i) if the vancosamine structure
given is a D- or L-sugar; ii) draw an open-chain Fischer projection formula of vancosamine; and iii) draw its
two pyranose chair conformations.
ii) Draw in a Fischer open- iii) Draw two chair
chain form.
conformations of
H3C
vancosamine.
O
HO
OH
H3C
NH2
vancosamine
3
i) stereochemical
designation:
D ; L
2
Circle the one that
applies.
4
3
IV. (9 points) Using the pKa and structure information given on page 11, answer the following questions.
(1) (6 points) Draw the structure of the major species for each of the following three amino acids at pH 5.
aspartic acid at pH 5
histidine at pH 5
arginine at pH 5
2
2
(2) (3 points) The amino acid among above three (i.e., histidine, aspartic acid, and arginine) that has the
highest isoelectric point (pI) is:
3
2
Name_______________________________
215 F12-Exam No. 3
Page 4
V. (22 points) In a recent publication, an interesting sequence of the Dieckmann condensationdecarboxylation reactions was used in the synthesis of a pharmacologically significant alkaloid molecule
[Org. Lett. 2012, 14, 852].
O
Ph2CH
1. LHMDS
(1 euiv), 0 °C
OCH3
N
O
O
2. H3O+ workup
OCH2CH3
OH O
Ph2CH
N
OCH2CH3
O
(1) (18 points) Draw in the box below a step-by-step, curved-arrow mechanism for the above Dieckmann
condensation reaction, including the last protonation step. Use LiNRR' for LHMDS.
O
Ph2CH
OCH3
N
O
O
OCH2CH3
H H
OH O
Ph2CH
N
OCH2CH3
O
18
(2) Treatment of the product shown above with H3O+/H2O with heat produces a ketone product. Draw in
the box the structure of the expected product from the reaction below.
OH O
Ph2CH
N
OCH2CH3
H3O+, H2O
+ CO2 + CH3CH2OH
Δ
O
4
Name_______________________________
215 F12-Exam No. 3
Page 5
VI. (20 points) Complete the following reactions by providing in each of the boxes the structure of the
starting compound, intermediate, or product. Indicate stereochemistry for the product/intermediate and if
more than one stereoisomer is formed, draw one structure and write “+ enantiomer” or “+ diastereomer.”
(1) [Synlett 2012, 2785]
O
OCH2CH3
+
1. NaH
2. H3O+-workup
O
O
C11H16O4
4
C11H19NO
4
C14H20O
4
(2) [J. Mol. Catal. A: Chemical 2013, 366, 36]
O
NH
+
MgCO3 (mild base)
H2O, 40 °C
(3) [Org Lett. 2004, 6, 3719]
O
1.
CuLi
2. H3O+-workup
(4)
OCH2CH3
O
O
1.
Ph
OCH2CH3
O
NaH
2. H3O+-workup
H3O+, H2O
Δ
4
4
+ CO2 + 2 CH3CH2OH
Name_______________________________
215 F12-Exam No. 3
Page 6
VII. (21 points) Complete the following reactions by providing in each of the boxes the structure of the
intermediate or product. Indicate stereochemistry for the product/intermediate and if more than one
stereoisomer is formed, draw one structure and write “+ enantiomer” or “+ diastereomer.”
(1) [Synlett 2012 2789]
HO
O
OH
O
HO
O
(excess)
O
OH
OH
N
HBr
CH2Cl2
(solvent)
(solvent)
3
S
S
N
HN(CH2CH3)3
SN2!
4
4
(2) [ACS Catal. 2012, in press]
O
O
O
O
O
O
SH
O
BF3•O(CH2CH3)2
or
TsOH
β anomer
4
NaOCH3 (catalytic)
HOCH3 (solvent)
NaH (2 equiv)
Br (2 equiv)
3
3
+ 2 NaBr
+ 2
O
OCH3
Page 9
The Reagent List
215 F12 Exam 3 - Page 9
Shown below is a list of key reagents (not always the whole recipe) that may be useful for solving questions
on the final exam.
reagent
classification
or specialized use
____________________________________________________________________________________
From
OsO4
oxidation
Chem 210 KMnO4
oxidation
peroxyacid
epoxidation
(e.g., 3- or meta-chloroperoxybenzoic acid or MCPBA)
i. O3; ii. (CH3)2S or Zn
ozonolysis
i. O3; ii. H2O2
ozonolysis
NaNH2
base, nucleophile
NaH
base
KOC(CH3)3
bulky base
H2/Pd
hydrogenation
H2/Pd, BaSO4, quinoline
hydrogenation
i. BH3 or 9-BBN; ii. H2O2, NaOH
hydroboration
PBr3
e.g., R-OH → R-Br
SOCl2
e.g., R-OH → R-Cl
p-CH3C6H4SO2Cl (p-TsCl)
tosylate formation
CH3SO2Cl (MsCl)
mesylate formation
N-bromosuccinimide (NBS)
O
Br N
source of electrophilic Br
O
===========================================================================
Ch. 13
C5H5NH+•ClCrO3- (PCC)
oxidant
CrO3/H2SO4/H2O/acetone
oxidant
i. ClC(=O)-C(=O)Cl, (CH3)2SO; ii. N(CH2CH3)3 oxidant
Ch. 14
NaBH4
LiAlH4
diisobutylaluminum hydride (DIBAL)
RMgX
RLi
4-CH3C6H4SO3H (p-TsOH) (pKa ~ -1)
Raney Ni
HSCH2CH2SH; HSCH3
BF3•O(CH2CH3)2
H2NNH2
H2NOH
nucleophilic hydride
nucleophilic hydride
nucleophilic hydride
nucleophilic carbon
nucelophilic carbon
organic-soluble acid
desulfurization
thioacetal/thioketal formation
Lewis acid
hydrazone formation
oxime formation
215 F12 Exam 3 - Page 10
Ch. 15
Ch. 17
SOCl2
Ag2O, NaOH, H2O
CH2 +N2 (diazomethane)
R-C(=O)OH → R-C(=O)Cl
oxidant
LiN[CH(CH3)2]2
strong, bulky base
(lithium diisopropylamide or LDA)
LiN[Si(CH3)3]2
strong, bulky base
(lithium hexamethldisilazide or LHMDS)
K2CO3
weak base
e.g., R-C(=O)OH →
R-C(=O)OCH3
The 20 naturally occurring amino acids
215 F12 Exam 3 - Page 11
Neutral amino acids
O
O
H2N
H
OH
H2N
H
CH3
Alanine
O
OH
H2N
H
O
NH2
Asparagine
H2N
SH
Cysteine
H2N
OH
OH
H2N
SCH3
H
H2N
Phenylalanine
H H
OH
Glycine
H
N
O
H2N
N
H
Tryptophan
OH
H Proline
N
H
NH2
O
H2N
OH
H
OH
O
OH
Tyrosine
H2N
NH
Arginine
H2N
H2N
OH
Lysine
H
O
O
OH
H
H
NH2
O
OH
O
OH
H
Glutamine
Basic amino acids
H2N
O
O
OH
Glutamic acid
H
H
O
OH
O
Aspartic acid
O
H
Methionine
H2N
H
O
Threonine
O
OH
H
H
HO
OH
OH
OH
Leucine
O
H2N
H
H2N
H
H2N
OH
O
O
OH
O
O
H2N
OH
Serine
Isoleucine
O
OH
H
H
Acidic amino acids
H2N
HN
OH
N
Histidine
H
Valine
pKa Values for the Ionizable Functional Groups of an α-Amino Acid
Amino acid
α-C(=O)OH
α-NH3+
side chain
___________________________________________________________________________________________________
Alanine
2.35
9.87
Arginine
2.01
9.04
12.48
Asparagine
2.02
8.80
Aspartic acid
2.10
9.82
3.86
Cysteine
2.05
10.25
8.00
Glutamic acid
2.10
9.47
4.07
Glutamine
2.17
9.13
Glycine
2.35
9.78
Histidine
1.77
9.18
6.10
Isoleucine
2.32
9.76
Leucine
2.33
9.74
Lysine
2.18
8.95
10.53
Methionine
2.28
9.21
Phenylalanine
2.58
9.24
Proline
2.00
10.60
Serine
2.21
9.15
Threonine
2.09
9.10
Tryprophan
2.38
9.39
Tyrosine
2.20
9.11
10.07
Valine
2.29
9.72
________________________________________________________________
NH2