39H
Quiz Chemistry 7
Tuesday, May 1, 2007
Name (printed) KEY
_____
Signature
This quiz consists of three questions -- check that you have them all. A perfect score on this
quiz is 30.
------------------------------------------------------------------(10)
1
(10)
2
(10)
3
TOTAL
1
Name ____________________________
(10) 1. Circle the correct answer.
(2) a. Which reduced carbohydrate is achiral?
H
(a)
HO
CH2OH
OH
H
CH2OH
CH2OH
OH
OH
CH2OH
H
H
(b)
HO
(c)
H
CH2OH
H
OH
CH2OH
(d)
CH2OH
H
OH
H
H
CH2OH
(2) b. For the amino acid synthesis shown below, the key carbon-nitrogen bond is formed between
O
O
1) PBr3, Br2; H2O
OH
H 2N
2) N H 3
R
OH
R
(a) an electrophilic carbon and a nucleophilic nitrogen.
(b) an electrophilic carbon and an electrophilic nitrogen.
(c) a nucleophilic carbon and a nucleophilic nitrogen.
(d) a nucleophilic carbon and an electrophilic nitrogen.
(2) c. Which compound is equivalent to D-idose?
HO
OH
HO
OH
O
OH D-idose
H
OH
HO
(a HO
HO
H
O
OH
OH
OH
HO HO
(b) HO
HO
OH
O
H
HO HO
(c) HO
HO
O
H
(d) HO
HO
HO
O
H
HO
(2) d. Treatment of alcohol 1 with CH3I/base provides glycoside 2. This reaction is an example of
AcO
AcO
AcO
AcO
O
CH3I
base
OH
AcO
AcO
AcO
AcO
1
O
O CH3
2
(a) glycosylation.
(b) mutarotation.
(c) nucleophilic acyl substitution.
(d) Sn2 substitution.
(2) e. Which amino acid is likely to have the lowest isoelectric point?
O
H 2N
RH
OH
R=
(a) CH2CH2CO2H
(c) CH2OH
(b) CH3
(d) CH2CH2CH2CH2NH2
2
Name ____________________________
(10) 2.
Provide short answers to the following questions.
(5) a.
Identify the product formed by heating chiral triene 1. Pay careful attention the
stereochemical to depiction of this product. Show how this stereochemistry evolves in
illustrative transition state depictions.
H
H
O
H
heat
H
Cope
O
O
H
H
1
H
H
Claisen
O
O
O
H
OHC
H
(5) b. Design a synthesis of (chiral) amino acid 2 starting from acetic acid (1).
O
Ph
??
1
O
Ph
H2/Pd
OH
NH2
H
OH
SOCl2
O
OH
N3
2
LiOH
H2O
O
O
O
Cl
N
O
Li
N
Ph
LDA
O
O
O
LDA
N
PhCH2Br
O
3
O
O
Ph
O
N
TolSO2N3
N3
O
Name ____________________________
(10) 3. The Maillard reaction is a complex sequence of transformations that are responsible for the
browning of food upon cooking. The initial steps involve the dehydrating condensation of a
carbohydrate with an amino acid, as modeled by the reaction of glucose (1) with alanine (2).
The product imine 3 then undergoes an isomerization to give the ketone product 4.
O
HO
O
HO
HO
+ H2N
OH
OH
CH3
HO
1
OH
cat. H+
heat
H2O
OH
O
N
HO
OH
OH
2
OH
cat. H+
OH
O
HO
CH3
OH
O
H
N
OH
OH
CH3
4
3
Provide a detailed mechanistic description of these processes.
O
H 2N
HO
cat.
O
HO
HO
HO
H+
OH
HO
HO
O
HO
HO
+
O H2
+
OH
CH3
2
HO
O
HO
HO
O
HO H N+
2
HO
OH
standard glycosylation chemistry
HO
HO
HO
O
HO
HO
1
proton
trans.
HO
H
O+
HO
O
HO HN
OH
HO HO Hb Ha O
H a+
N
OH
+
OH OH
CH3
iminium ion
HO HO Hb
O
N
HO
OH
OH
3
OH
CH3
H b+
HO
OH
Ha
O
N
HO
OH OH
enamine
tautomerization
OH
CH3
HO
O
Ha
O
N
HO
OH OH
OH
CH3
4
Rather than deptotonation of the iminium ion to give an enamine, many of you invoked a 1,2-hydride
shift of Hb in order to convert the iminium ion to product 4. That suggestion is quite plausible as
well.
4
5