Chiroptical sensing of amino acids by stereodynamic imprinting into the ZnII-Complex generating a dihedral chirality

Article abstract of DOI:10.1016/j.dyepig.2019.01.007

A stereodynamic chiroptical sensor based on three-component assembly of 3-(di-2-picolylaminoacetamido)-2-formyl-naphthalene (1), Zn^II and amino acids was developed. The imine formed between 1 and an amino acid has six coordination sites to bind

Full text of DOI:10.1016/j.dyepig.2019.01.007

Accepted Manuscript
II
Chiroptical sensing of amino acids by stereodynamic imprinting into the Zn -Complex
generating a dihedral chirality
Qian Chen, Mukesh Eknath Shirbhate, Youngmee Kim, Sung-Jin Kim, Baotao Kang,
Kwan Mook Kim
PII:
S0143-7208(18)32073-4
https://doi.org/10.1016/j.dyepig.2019.01.007
DYPI 7280
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 21 September 2018
Revised Date: 5 January 2019
Accepted Date: 7 January 2019
Please cite this article as: Chen Q, Shirbhate ME, Kim Y, Kim S-J, Kang B, Kim KM, Chiroptical sensing
II
of amino acids by stereodynamic imprinting into the Zn -Complex generating a dihedral chirality, Dyes
and Pigments (2019), doi: https://doi.org/10.1016/j.dyepig.2019.01.007.
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ACCEPTED MANUSCRIPT
Chiroptical Sensing of Amino Acids by Stereodynamic Imprinting into the
II
Zn -Complex Generating a Dihedral Chirality
a
a
a
a
b
Qian Chen, Mukesh Eknath Shirbhate, Youngmee Kim, Sung-Jin Kim, Baotao Kang,* Kwan
a
Mook Kim*
a
Department of Chemistry & Nano Science, Ewha Womans University, Seoul 03760, Korea. *E-
mail: kkmook@ewha.ac.kr
b
School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, China.
*
E-mail: chm_kangbt@ujn.edu.cn
Abstract: A stereodynamic chiroptical sensor based on three-component assembly of 3-(di-2-
II
picolylaminoacetamido)-2-formyl-naphthalene (1), Zn and amino acids was developed. The
II
imine formed between 1 and an amino acid has six coordination sites to bind tightly Zn ion. The
II
crystal structure of the Zn complex, 1-Zn-
D
-Phe, revealed that the naphthyl ring is tilted to one
-Phe
-Phe binding
-Phe-α by 5.5 kcal/mol.
pyridine ring to generate axial chirality. The dihedral conformations observed in 1-Zn-
D
were herein arbitrarily designated as α and α . DFT calculation suggests that the
D
1
2
prefer the α -conformer: the energy of
D-Phe-α is more stable than
L
1
1
1
This preference to one diastereomer generates amplification of CD signal with Cotton effect,
which can be applied to the determination of ee values of the amino acid.
Keywords: Circular dichroism amplification, absolute configuration of amino acid, enantiomeric
excess determination, dihedral chirality, stereodynamic imprinting
1
. Introduction
Chiral molecules such as amino acids are key components in asymmetric catalysts, bioactive
compounds and pharmaceuticals [1-2]. Significant efforts have been devoted to the development
of the methods to determine enantiomeric excess (ee) of chiral compounds using analytical tools
such as high-performance liquid chromatography (HPLC) [3-4], gas chromatography (GC) [5-6],
fluorescence [7-9], nuclear magnetic resonance (NMR) [10-13] and circular dichroism (CD) [14-
1
7]. The CD determination method has some advantages over others in the points that it does not

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require chiral receptors and can be operated conveniently with relatively cheap instruments, and
thus can be applied in high-throughput screening (HTS) for large number of samples [18-20].
CD sensing technologies employ the strategy of stereodynamic imprinting of the chiral
information of a substrate through ion pair interactions [21-23], imine formations [24-26], and
metal bindings [27-29], which generate diastereomers with an axial chirality to exhibit amplified
CD signals [30-33].
Most CD sensors for amino acids so far developed usually possess carbonyl groups that bind
the amino acids by reversible imine bond formation. J. Chin’s group developed the
dihydroxybenzophenone system that bind amino acids in a highly stereospecific manner [34]. C.
Zonta’s group reported the benzaldehyde connected to a tripicolyl amine ligand that bind amino
II
acids and Zn metal ion [35-37]. It is postulated that the metal binding impart a rigidity to the
imine compound and improve the stereoselectivity for one conformation of the complex, and the
chromophore of metal-ligand charge transfer may contribute to the enhancement of CD signal
intensities.
In this context, we have designed and synthesized an achiral molecule 1, amino naphthol
aldehyde linked to di-2-picolylamine. Compound 1 and an amino acid would form a Schiff base
and provide six coordination sites to bind tightly a metal ion. We expected that the complex
II
formed by three components of 1, an amino acid and Zn ion would have a sufficiently rigid and
compact structure, whose axial chirality be governed by the chirality of the amino acid to
generate amplified strong CD signals (Chart 1).
Chart 1. Chiroptical sensing
2. Experimental section
2.1 Synthesis

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2.1.1 General information.
II
3
-Amino-2-naphthoic acid, bromoacetylbromide, Zn perchlorate hexahydrate and other
reagents or solvents were purchased from commercial sources and used without any further
purification unless otherwise stated. CD spectra were obtained with a Jasco J-715 spectrometer
1
13
(
1 cm quartz cell) at 25 °C. H and C NMR spectra were recorded in CDCl containing
3
tetramethylsilane (TMS) as an internal standard. Uv/Vis absorption spectra was conducted with
Lambda 365 (1 cm quartz cell) at 25 °C. Column chromatography was performed on a silica gel
of 230-400 mesh.
2.1.2 Synthesis of N-di-2-picolyaminomethy-3-aminonaphthyl-2-aldehyde (1)
Synthesis of methyl 3-amino-2-naphthoate (3)
A solution of conc. H SO (10 mL) and 3-amino-2-naphthoic acid (5.61 g, 30 mmol) in
2
4
o
methanol (50 mL) was refluxed for 6 h at 80 C. The reaction mixture was poured into an ice
water, neutralized with Na CO , and extracted with CH Cl (methylenechloride). The extracted
2
3
2
2
organic layer was evaporated, and the residue was purified by column chromatography with
1
eluent of ethylacetate (EA)/hexane (1/20) to obtain 3 as a yellow solid (4.82 g). Yield 80%. H
NMR (300 MHz, CDCl ): 8.52 (s, 1H), 7.75 – 7.72 (m, 1H), 7.60 – 7.51 (m, 1H), 7.49 – 7.33 (m,
3
1
3
1
H), 7.21 (s, 1H), 7.05 – 6.92 (m, 1H), 5.60 (s, 2H), 3.98 (s, 3H). C NMR (125 MHz,
CDCl ):168.3, 145.9, 137.3, 133.4, 128.7, 126.0, 125.1, 122.5, 114.7, 109.9, 51.9. HRMS (EI):
3
+
calcd for C H NO [M+H] : 202.0790; found 202.08754.
1
2
11
2
Synthesis of methyl 3-(2-bromoacetamido)-2-naphthoate (4)
Bromoacetylbromide (4.82 g, 24 mmol) was added to the mixture of 3 (4.02 g, 20 mmol) and
o
K CO (3.31 g, 24 mmol) in acetonitrile (20 mL) at 0 C for 30 min. After stirring for 5 h, the
2
3
reaction was quenched with aqueous saturated NH Cl, and the solution was extracted with EA.
4
The organic layer was evaporated under reduced pressure, and the residue was purified by
column chromatography with eluent of EA/Hexane (1/10) to obtain 4 as a brown liquid (4.17 g).
1
Yield 65%. H NMR (300 MHz, CDCl ): 11.71 (s, 1H), 9.13 (s, 1H), 8.66 (s, 1H), 7.86 – 7.84 (m,
3
1
3
2
H), 7.62 – 7.57 (m, 1H), 7.49 – 7.45 (m, 1H), 4.10 (s, 2H), 4.04 (s, 3H). C NMR (125 MHz,
CDCl ): 168.3, 164.7, 136.2, 135.2, 133.3, 129.3, 128.9, 128.7, 127.8, 125.9, 117.7, 115.9, 52.7.
3
+
HRMS (EI): calcd for C14
H
12BrNO
3
[M+H] : 322.0001; found 322.00949.

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Synthesis of methyl 3-(di-2-picolylaminoacetoamido)-2-naphthoate (5)
The mixture of 4 (3.21 g, 10 mmol), di-2-picolylamine (2.38 g, 12 mmol), K CO (1.65 g, 12
2
3
mmol) and KI (1.99 g, 12 mmol) in acetonitrile (20 mL) was refluxed for 6 h. The reaction was
terminated by saturated ammonium chloride solution. After extraction, the organic layer was
evaporated and the residue was purified by column chromatography with eluent of EA/Hexane
1
(
1/6) to obtain 5 as a brown liquid (2.60 g) Yield 59%. H NMR (300 MHz, CDCl
3
): 11.90 (s,
1
7
2
1
H), 9.14 (s, 1H), 8.58 (s, 1H), 8.53 – 8.50(m, 2H), 7.85 – 7.77(m, 4H), 7.68 – 7.62 (m, 2H),
.53 – 7.47 (m, 1H), 7.41 – 7.35 (m, 1H), 7.15 – 7.11 (m, 2H), 4.03 (s, 3H), 4.01 (s, 4H), 3.50 (s,
1
3
H). C NMR (125 MHz, CDCl ): 170.2, 167.9, 158.0, 149.0, 136.5, 136.2, 135.4, 132.9, 129.0,
3
28.7, 127.6, 125.5, 123.5, 122.3, 117.8, 61.2, 59.3, 52.4. HRMS (EI): calcd for C H N O
3
2
6
24
4
+
[
M+H] : 441.1848; found 441.17137
Synthesis of 3-(di-2-picolyaminoacetoamido)-2-hydroxymethyl-naphthalene (6)
The mixture of 5 (2.55 g, 5.80 mmol) and sodium borohydride (1.10 g, 29 mmol) in THF (15
mL) was refluxed for 6 h, quenched with brine, and extracted with CH Cl . The organic layer
2
2
was evaporated in vacuo. The residue was purified by column chromatography with an eluent of
1
CH Cl /hexane (1/1), to obtain 6 as a brown liquid (1.65 g). Yield, 69%. H NMR (300 MHz,
2
2
CDCl ): 11.23 (s, 1H), 8.62 (s, 1H), 8.61-8.58 (m, 2H), 7.84 – 7075 (m, 2H), 7.74 – 7.68 (m, 3H),
3
1
3
7
.49 – 7.37 (m, 4H), 7.28 – 7.23 (m, 2H), 4.98 (s, 2H), 3.89 (s, 4H), 3.44 (s, 2H). C NMR
(
125MHz, CDCl ): 168.8, 157.3, 149.2, 137.5, 134.9, 133.6, 127.8, 127.6, 127.3, 126.2, 125.0,
3
+
1
24.4, 122.9, 118.7, 63.1, 60.6, 59.5. HRMS (EI): calcd for C25
found 413.19956.
Synthesis of 3-(di-2-picolyaminoacetamido)-2-formyl-naphthalene (1)
The mixture of 6 (4.12 g, 10 mmol) and manganese dioxide (4.35 g, 50 mmol) in CH Cl (20
H
22
N
4
O
2
[M+H] : 413.1899;
2
2
mL) was refluxed for 6 h, filtered out to remove manganese dioxide. The filtrate was purified by
2 2
column chromatography with the eluent of CH Cl to get 1 as a light yellow liquid (2.80 g).
1
Yield, 68.3%. H NMR (300 MHz, CDCl ): 11.86 (s, 1H), 10.00 (s, 1H), 9.03 (s, 1H), 8.44 –
3
8
7
1
.42(m, 2H), 8.04 (s, 1H), 7.81 – 7.78 (d, 2H), 7.73 – 7.57 (m, 4H), 7.46 – 7.40 (m, 1H), 7.32 –
1
3
.26 (m, 1H), 7.06 – 7.02 (m, 2H), 3.92 (s, 4H), 3.44 (s, 2H). C NMR (125 MHz, CDCl
3
):
94.4, 170.6, 157.9, 148.9, 139.7, 136.8, 136.6, 134.7, 130.1, 128.8, 128.5, 127.7, 125.7, 123.4,

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+
1
4
23.2, 122.3, 117.3, 61.2, 59.2. HRMS (EI): calcd for C25
11.18239.
24 4 2
H N O [M+H] : 411.1743; found
2.1.3 Synthesis of 1-Zn-D-Phe
The solution of 1 (102 mg, 0.25 mmol) in acetonitrile (10 mL) and the solution of Zn
ClO ) 6H O (1.0 eq), -Phe (1.0 eq) and tetramethylammonium hydroxide (1.0 eq) in MeOH
0.2 mL) were mixed, and stirred at room temperature for 5 h. The solution was filtered out,
(
(
D
4
2·
2
evaporated, and the residue was purified by column chromatography on alumina using an eluent
of CH Cl /MeOH (20/1) to obtain pure 1-Zn-
D
-Phe. Single crystals for X-ray crystallography
2
2
1
were obtained by recrystallization in the cosolvent of CH
2
Cl
2
and toluene. H NMR (300 MHz,
CDCl ): 9.26 (s, 1H), 8.07 (d, J = 4.4 Hz, 2H), 7.96 (d, J = 4.5 Hz, 1H), 7.82 (t, J = 7.4 Hz, 1H),
3
7
.75 – 7.53 (m, 3H), 7.49 – 7.21 (m, 11H), 7.15 – 7.04 (m, 1H), 4.68 (t, J = 13.3 Hz, 2H), 4.41 (d,
J = 5.9 Hz, 1H), 4.34 – 4.14 (m, 2H), 3.91 – 3.64 (m, 1H), 3.38 (s, 2H), 3.22 (dd, J = 13.8, 9.5
1
3
Hz, 1H). C NMR (125 MHz, CDCl ): 175.5, 171.7, 170.3, 153.7, 152.9, 147.5, 146.5, 144.5,
3
1
1
39.1, 139.0, 138.3, 137.9, 136.6, 130.7, 129.2, 128.8, 128.1, 128.1, 127.7, 127.2, 124.6, 124.6,
24.3, 123.8, 123.8, 123.7, 121.6, 70.2, 64.2, 63.4, 62.8, 40.9. HRMS (FAB): calcd for
+
C H N O Zn [M+H] : 620.1640; found 620.1642.
34
29
5
3
2
.2 General procedure for CD measurements
Compound 1, Zn (ClO ) 6H O, amino acid and Me NOH were mixed together in 1:1:1 molar
4
2·
2
4
-4
ratio and stirred for 5 h. The reaction solution was diluted to the concentration of 5.0 × 10 M
using an additional acetonitrile solvent, with which CD spectra was obtained without any work-
up procedure.
2
.3 X-ray crystallographic study
Crystallographic data for 1-Zn-
D
29 5 3 2 2
-Phe, [C34H N O Zn]·1.5(CH Cl ): A orange block crystal
with approximate dimensions of 0.15 mm x 0.17 mm x 0.18 mm was used for the X-ray
crystallographic analysis [38]. The frames were integrated with the Bruker SAINT software
package using a narrow-frame algorithm. The integration of the data using a orthorhombic unit
cell yielded a total of 47705 reflections to a maximum θ angle of 25.50°, of which 6493 were
1 1 1
independent (Rint = 0.1315). The final cell constants are orhtorhombic space group P2 2 2 , a =

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3
1
1.440(7) Å, b = 13.554(8) Å, c = 22.717(14) Å, V = 3522.(4) Å . Data were corrected for
absorption effects using the multi-scan method (SADABS) [39]. The final anisotropic full-matrix
2
least-squares refinement on F with 442 variables converged at R = 7.34% for the observed data.
1
The goodness-of-fit was 1.033. The structure has been deposited with Cambridge Structural
Database, CCDC 1866168.
3. Results and discussion
3.1 Synthesis
Esterification of 3-amino-2-naphthoic acid followed by the reaction with bromoacetylbromide,
the substitution reaction with di-2-picolylamine, reduction and oxidation reactions produced the
1
desired compound 1 (Scheme 1). The chemical structure of compound 1 was confirmed by H
1
3
and C NMR and HRMS (SI).
2 4 2 3 2 2
Scheme 1. Reagent and condition: a) H SO , MeOH, reflux, 5 h; b) Bromoacetylbromide, K CO , CH Cl ,
reflux, 10 h; c) Di-2-picolylamine, K CO , KI, CH CN, reflux, 3 h; d) NaBH , THF, rt, 5 h; e) MnO ,
2
3
3
4
2
CH Cl , reflux, 8 h.
2
2
Chemical Structure of 1-Zn-
D-Phe
The reaction of compound 1,
D
-Phe as tetramethylammonium salt and Zn(ClO ) in acetonitrile
4 2
solution in 1:1:1 molar ratio gave the complex with a discrete structure, 1-Zn-D-Phe, whose
1
molecular structure was confirmed by H NMR and X-ray crystallographic studies. Figure 1

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1
compares the partial H NMR spectra for the free form of compound 1 and the complex, 1-Zn-
Phe. The signal of the aldehyde proton exhibiting at 10.00 ppm in the free form shifts upfield to
.04 ppm in the complex indicating the formation of the imine bond. The –CH - protons of D-
D-
8
2
Phe and pyridyl groups are shown as a doublet of doublet pattern at 3 to 5 ppm region (Figure
1
1
b), which indicates the rigidity of the metal complex. The amide proton signal appearing at
1.87 ppm in the free form disappeared at the complex, which strongly indicates that the amide
nitrogen is involved in the binding of the metal ion.
1
Figure 1. The H NMR spectra of compound 1 (a) and 1-Zn-
D
-Phe (b) in CDCl3.
X-ray Analysis
2 2
The optimum single crystals of 1-Zn-D-Phe were grown from the solution of CH Cl and
toluene, and crystallized in an orthorhombic space group, P2 2 2 . It was formulated
1
1 1
[
C H N O Zn]·1.5(CH Cl ), and the structure was shown in Figure 2. The coordination sphere
34 29 5 3 2 2
II
around the Zn ion can be described as a distorted octahedral geometry with five N atoms and
one carboxylate O atom as ligand atoms. The Zn(1)-N(1) bond length of 2.047(8) Å, where N(1)
is the imine bond from
D-Phe, is shorter than other Zn-N coordination bonds ranging from
2
.071(7) Å to 2.264(9) Å. The distance of Zn(1)-O(1) is 2.123(6) Å.

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Figure 2. Crystal structure of the complex, 1-Zn-D-Phe. All hydrogen atoms are omitted for clarity.
3.2 Chiroptical sensing
CD Analysis.
CD measurement of achiral aldehyde 1 only does not give any signal throughout all the
wavelengths, as is expected. The CD measurement on -Phe only did not give any significant
D
signal at the wavelengths longer than 300 nm in the condition of this work. The mixture of
compound 1, Zn (ClO ) ·6H O and tetramethylammonium salt of phenylalanine in 1:1:1 molar
4
2
2
-4
ratio was stirred in acetonitrile for 5 h at room temperature, diluted to 5.0 × 10 M solution using
an additional acetonitrile solvent, with which CD spectra was obtained.
The CD spectrum in Figure 1 shows Cotton effect (CE) for 1-Zn-D-Phe complex with a trough
at the wavelength of 308 nm and a peak at 360 nm, and negative CE for 1-Zn-L-Phe complex
with the opposite couplets.

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8
6
4
2
0
0
0
0
0
D-Phe-Zn-1
L-Phe-Zn-1
D-Phe-Zn
320
340
360
380
400
-20
-40
-60
-80
II
Figure 3. CD spectra for the reaction mixtures of 1, Zn and separate enantiomers of
phenylalanine.
CD measurements were performed for the complexes of other representative amino acids 8-16
(Chart 2) under the same condition with that used in the experiment of Phe. Their CD patterns
were similar with that shown in Figure 1, except the complex of aspartic acid 15 which gave
positive CE spectrum for 1-Zn-
L-Asp complex (see supporting information). The presence of
II
two carboxylate groups in Asp may compete to bind Zn ion [36].
Chart 2. Structures of amino acids tested.

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Origin of CD
When the complex of 1-Zn-D-Phe shown in Figure 2 is viewed from the top side, two pyridine
rings are disposed on both left and right sides of the naphthalene ring as shown in Figure 4a. It is
noticeable that there exist two dihedral angles in the complex. One angle was assigned as α and
the other as α , and an axial chirality was generated by the difference of the two dihedral angles.
1
2
Herein we will assign this axial chirality as a dihedral chirality. We can distinguish α
1
conformer
from α conformer, where α -conformer is the one with a smaller angle of α and α -conformer is
2
1
1
2
the opposite. Figure 4b shows a simplified schematic expression for the complexes of 1-Zn-
D-
AA, its mirror image 1-Zn- -AA, and its possible dihedral diastereomer.
L
(
a)
Figure 4. The dihedral chirality observed in the crystal structure of 1-Zn-
angle of α is smaller than that of α (a), and a schematic representation for the possible
diastereomers including the mirror image (b).
(b)
D
-Phe where the
1
2
As revealed in the crystal structure,
DFT calculation on the possible diastereomers,
more stable than -Phe-α by 5.5 kcal/mol. Thus, it may be proposed that when
the α conformer is favored with
D-Phe bound complex adopted the conformation of α . The
1
D
-Phe-α and L-Phe-α , revealed that D-Phe-α is
1 1 1
L
D
-Phe is bound,
2
1
D
-Phe binding and the α
2
conformer is favored with -Phe
L
binding. The consequence is that the chirality of the amino acid is imprinted in the metal
complex, which is a key condition to obtain CD signals with a CD silent chiral compound.
The
D-forms of seven amino acids among eight amino acids tested seem to adopt α1
II
conformation in the Zn complex because they all showed positive Cotton Effect in the same
manner with Phe.

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Analysis of ee.
Figure 5 shows the calibration CD curves for the controlled valine enantiomeric mixtures with
100, +80, +60, +40, +20, 0, -20, -40, -60, -80 and -100% ee values, where (+) indicates -form
+
L
excess. A fairly good linear relationship between the CD signals and ee values, as shown in
II
Figure 5b, indicates that compound 1, Zn and Val react in 1:1:1 ratio to generate the complex
quantitatively. Good linear relationship is a prerequisite for the determination of ee values of
unknown enantiomeric mixtures of an amino acid.
Based on the calibration curve of Figure 5, four samples with arbitrary optical purities of +84,
+
32, -52 and -30% ee were determined for their ee values by CD measurements. The
experimentally calculated ee values are quite well in good agreement with the actual values
within error range of less than 5% as shown in Table 1. This reveals that the ensemble of 1 and
II
Zn is a potential chiroptical sensor to determine the absolute ee values of amino acids in a
convenient and effective way.
1
20
00
1
1
20
00
80
80
60
40
20
0
1
60
40
20
0
320
340
360
380
400-120
-80
-40
0
40
80
120
-
20
40
60
80
-100
120
-
-
-
-
20
40
60
80
ee
nm
-
-
-
-
-
-
100
120
II
Figure 5. CD spectra for the reaction samples of 1, Zn and Val with variable ee values of -100,
80, -60, -40, -20, 0, +20, +40, +60, +80 and +100, where +100 indicates -form of 100% ee. All
-
L
-4
the concentrations of the components were adjusted to 5.0×10 M in CH CN.
3
Table 1. Determination %ee values for four arbitrary samples of Val.
Absolute form Actual% ee
Calculated% ee Absolute

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Error%
L
L
D
D
84
32
-52
-30
83.2
33.2
-53.8
-31.1
0.9
3.7
3.5
3.7
4
. Conclusion
II
We synthesized compound 1, and demonstrated that the ensemble of 1 and Zn bind an amino
acid by imine formation and metal coordination, and generate the CD signal of a mirror image
for the opposite enantiomer of an amino acid. The 3-dimensional structure for the complex of 1-
Zn-D-Phe was totally determined by X-ray crystallography, where the disposition of the
naphthalene and two pyridine rings generate a dihedral chirality discriminated by dihedral angles.
This is an example of imprinting of the chirality of the amino acid in the complex, and
amplification of the CD signal for the chiral compound with negligible CD intensity. We
demonstrated that absolute chiral sense and optical purity of an amino acid can be conveniently
II
determined within 5% error range by CD measurements by using 1 and Zn as a cooperative CD
sensor.
Acknowledgments
This work was supported by the National Research Foundation of Korea (NRF) grant funded by
the Korea government (MSIP) (NO. NRF-2017R1A2B2009672).
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3
[
[
[
[
2
[
[
2

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–
[
2

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Scheme Title and Captions of Figures
Chart 1. Chiroptical sensing
Chart 2. Structures of amino acids tested.
Scheme 1. Synthesis of compound 1.
1
Figure 1. The H NMR spectra of compound 1 (a) and 1-Zn-
D
-Phe (b) in CDCl
3
.
Figure 2. Crystal structure of 1-Zn-D-Phe complex. All hydrogen atoms are omitted for clarity.
II
Figure 3. CD spectra for the reaction mixtures of 1, Zn and separate enantiomers of
phenylalanine.
Figure 4. The dihedral chirality observed in the crystal structure of 1-Zn-D-Phe where the angle
of α1 is smaller than that of α2 (a), and schematic representation for the possible diastereomers
including the mirror image (b).
II
Figure 5 CD spectra for the reaction samples of 1, Zn and Val with variable ee values of -100, -
8
0, -60, -40, -20, 0, +20, +40, +60, +80 and +100, where +100 indicates
L-form of 100 % ee. All
-4
the concentrations of the components were adjusted to 5.0×10 M in CH
Table 1. Determination %ee for four arbitrary samples of Val.
3
CN.

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Graphical Abstract
Sensing of the Chirality of Amino Acids by Stereodynamic
II
Imprinting into the Zn -Complex with a Dihedral Chirality
Qian Chen, Mukesh Eknath Shirbhate, Youngmee Kim, Sung-Jin Kim, Baotao Kang, Kwan
Mook Kim
Highlight
II
1
. The three-component assembly of 1, Zn and an amino acid generates a dihedral chirality on
the complex.
. The CD signal of an amino acid was amplified by the stereodynamic imprinting, and the %ee
of an arbitrary sample of the amino acid could be determined within a 5% error margin.
2

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Manuscript_DYPI_2018_1989
Sensing of the Chirality of Amino Acids by Stereodynamic
II
Imprinting into the Zn -Complex with a Dihedral Chirality
Qian Chen, Mukesh Eknath Shirbhate, Youngmee Kim, Sung-Jin Kim, Baotao Kang, Kwan Mook
Kim
Highlights
ò
ò
ò
Aminonaphthylaldehyde linked by dipycolylamine (1) was synthesized.
An amino acid is imprinted into Zn(II) complex of 1 to give dihedral chirality
Dihedral chirality produces a CD signal to measure %ee of the amino acid

ACCEPTED MANUSCRIPT
Supporting information
Chiroptical Sensing of Amino Acids by Stereodynamic Imprinting into the
II
Zn -Complex Generating a Dihedral Chirality
a
a
a
a
b
Qian Chen, Mukesh Eknath Shirbhate, Youngmee Kim, Sung-Jin Kim, Baotao Kang,* Kwan
a
Mook Kim*
a
Bio-Chiral Lab, Department of Chemistry & Nano Science, Ewha Womans University, Seoul
0
3760, Korea. *E-mail: kkmook@ewha.ac.kr
b
School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, China.
E-mail: chm_kangbt@ujn.edu.cn
*

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1. Synthetic scheme and NMR spectra
Synthetic Scheme. Reagent and condition: a) H
2 4 2 3
SO , MeOH, reflux, 5 h; b) Bromoacetylbromide, K CO ,
CH Cl , reflux, 10 h; c) Di-2-picolylamine, K CO , KI, CH CN, reflux, 3 h; d) NaBH , THF, rt, 5 h; e)
2
2
2
3
3
4
MnO , CH Cl , reflux, 8 h.
2
2
2

ACCEPTED MANUSCRIPT
1
Figure S1-1. H NMR spectrum of 3 in CDCl .
3
1
3
Figure S1-2. C spectrum of 3 in CDCl .
3

ACCEPTED MANUSCRIPT
1
Figure S1-3. H NMR spectrum of 4 in CDCl .
3
1
3
Figure S1-4. C NMR spectrum of 4 in CDCl .
3

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1
Figure S1-5. H NMR spectrum of 5 in CDCl .
3
1
3
Figure S1-6. C NMR spectrum of 5 in CDCl .
3

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1
Figure S1-7. H NMR spectrum of 6 in CDCl .
3
1
3
3
Figure S1-8. C NMR spectrum of 6 in CDCl .

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1
Figure S1-9. H NMR spectrum of 1 in CDCl .
3
1
3
3
Figure S1-10. C NMR spectrum of 1 in CDCl .

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2. HRMS data
6
+ Scan (rt: 0.170 min) 170112-EWU-KKM-A-p.d Subtract
202.08754
x10
3
4
.5
3
2
.5
2
1
.5
1
0
.5
0
4
15.12869
400
1
00
200
300
500
600
700
800
900
1000
1100
Counts vs. Mass-to-Charge (m/z)
Figure S2-1. ESI-HRMS of 3.
6
+ Scan (rt: 0.115 min) 170112-EWU-KKM-B-p.d Subtract
22.00949
x10
3
7
6
5
4
3
2
1
0
1
97.10797
511.46632
666.98748
1
00 150 200 250 300 350 400 450 500 550 600 650 700
Counts vs. Mass-to-Charge (m/z)
750 800
Figure S2-2. ESI-HRMS of 4.

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6
8
6
4
2
0
+ Scan (rt: 0.210 min) 180306-EWU-KKM-Step5-p.d Subtract
41.17137
x10
4
2
21.07489
9
03.35973
900
3
64.10445
690.23034
700
1185.28011
1
00
200
300 400
500
600
800
1000 1100 1200 1300
Counts vs. Mass-to-Charge (m/z)
Figure S2-3. ESI-HRMS of 5.
6
+ Scan (rt: 0.188 min) 170112-EWU-KKM-C-p.d Subtract
413.19956
x10
6
5
4
3
2
1
0
1
98.09857
8
47.37279
1
00 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000
Counts vs. Mass-to-Charge (m/z)
Figure S2-4. ESI-HRMS of 6.
6
- Scan (rt: 0.131 min) 170112-EWU-KKM-C-n.d Subtract
x10
5
4
11.18209
4
3
2
1
0
2
48.96030
1
033.98700
1
00 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600
Counts vs. Mass-to-Charge (m/z)
Figure S2-5. ESI-HRMS of 1.

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3. Circular Dichroism Measurement
General: A stock solution of 1 (0.5 mL, 0.01 M) in acetonitrile, a solution of an amino acid in
anionic form as tetramethylammonium salt in MeOH (0.01 mL, 0.5 M) and a stock solution of
Zn(ClO ) in MeOH (0.01 mL, 0.5 M) were mixed together in 4 mL vial. The mixture was
4
2
-4
stirred for 5 h at 25 ℃ and diluted to the concentration of 5.0×10 M by addition of acetonitrile,
with which CD spectroscopy was obtained. The CD spectroscopy was acquired with
accumulations of 3 scans, a data pitch of 2.0 nm, a band width of 1 nm, a scanning speed of 200
nm/s and response of 1.0 s using a quartz cuvette (1 cm path length), temperature of 25 ℃.
The amino acids tested:

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Table S3-1 CD data of amino acids with compound 1
Amino acid
-7
λ [nm]
mdeg
-74.52
20.55
80.68
3
3
3
08
66
10
D
L-7
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
64
16
70
10
70
20
66
20
66
08
64
08
62
12
62
10
64
08
64
08
66
-21.57
-95.09
16.48
96.93
-23.10
-35.29
9.03
D
-8
L-8
D-9
36.89
-9.37
L-9
-112.77
10.44
113.92
-15.29
-53.05
13.96
51.51
-13.41
-91.29
22.42
80.17
-21.29
-60.83
D
-10
L-10
D
-11
L-11
D
-12
L-12
D
-13
330

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4
3
4
3
3
3
3
3
3
3
3
3
3
3
3
00
28
02
18
58
18
52
10
64
10
62
10
68
12
73
66.17
58.91
-55.55
-28.03
10.48
30.36
-6.08
93.15
-5.45
-95.49
7.54
L
-13
D
-14
L-14
D
-15
L-15
-23.56
7.83
D
-16
19.76
-11.56
L-16