1H and 13C NMR spectral assignments of 18 novel polymethoxylated naphthochalcones bearing pyrazoline-1-carbothioamide groups

Full text of DOI:10.1002/mrc.4217

Letter ‐ spectral assignment
Received: 20 August 2014
Revised: 26 November 2014
Accepted: 20 January 2015
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/mrc.4217
1
13
H and C NMR spectral assignments of 18
novel polymethoxylated naphthochalcones
bearing pyrazoline-1-carbothioamide groups
a†
a†
a
a
Hyeryoung Jung, Seunghyun Ahn, Mijoo Park, Hyuk Yoon,
b
b
c
c
Hyung Jun Noh, Seung Yu Kim, Jin Sil Yoo, Dongsoo Koh **
a
and Yoongho Lim *
N-phenyl-pyrazoline-1-carbothioamide is described as follows.
,3-dimethoxybenzaldehyde (II, 1.6 g, 10 mmol) was added to a
Introduction
2
Plant-derived polyphenols are classified based on their carbon
skeleton. Polyphenols with a C6–C3–C6 skeleton are called flavo-
noids and include flavones, flavanones, isoflavones, anthocya-
solution of 1-hydroxy-acetonaphthone (I, 1.86g, 10 mmol) in 50 ml
of ethanol, and the temperature was adjusted to 4 °C in an ice bath.
Five milliliters of 50% (w/v) aqueous KOH solution was added to the
cooled reaction mixture, and the reaction mixture was stirred at
room temperature for 48 h. The reaction mixture was poured into
ice water and acidified with 6 N HCl. The resulting precipitate was
filtered and washed with ethanol and used for the next reaction
(III, yield 75%). Excess hydrazine monohydrate (1 ml of 64–65%
solution, 13 mmol) was added to a solution of 1-hydroxy-
naphthochalcone (III, 1.7 g, 5 mmol) in 30 ml of anhydrous ethanol,
and the solution was refluxed for 6 h. The reaction mixture was
cooled to room temperature to yield a solid that was then filtered.
[1]
nins, and chalcones. While most flavonoids have C3 with a
closed ring, the chalcone C3 has an α,β-unsaturated carbonyl
group so that the two benzene rings of the chalcone are con-
nected through an open ring. Polyphenols bearing a pyrazoline
moiety show various biological activities, including antimicrobial,
[
2–4]
anti-inflammatory, antitumor, and antidepressant activities.
Chalcones bearing a pyrazoline moiety instead of an α,β-unsatu-
rated carbonyl group conserve the C6–C3–C6 skeleton and have
a closed-ring C3 like other flavonoids. The anti-colorectal cancer
activities and inhibitory effects on aurora B kinase of several
[
5]
chalcones bearing a pyrazoline moiety have been reported.
Polyphenols bearing a carbothioamide substituent at the N-1
of pyrazoline have antimicrobial, anticonvulsant, and antidepres-
[6,7]
sant activities.
Therefore, combined chalcones bearing both a
pyrazoline moiety and a carbothioamide substituent can be
designed. Methoxylation increases the cell permeability and
[
8]
stability of many plant-derived polyphenols. The previous works
demonstrated that the position and number of methoxy groups al-
[
9–11]
ter the biological activities of polymethoxylated polyphenols.
To discover the potent polyphenols with antitumor activity, we de-
signed and synthesized 18 novel polymethoxylated naphtho-
chalcones bearing a pyrazoline-1-carbothioamide moiety (Fig. 1).
Figure 1. Chalcone bearing pyrazoline, carbothioamide, and naphthyl
groups.
1
The number of methoxy groups ranged from two to five. Their H
13
and C nuclear magnetic resonance (NMR) data were assigned
completely, and their molecular mass data were collected. This
should help us identify the plant-derived polyphenols newly
synthesized or isolated from the natural sources in the future.
*
Correspondence to: Prof. Yoongho Lim, Division of Bioscience and Biotechnology,
BMIC, Konkuk University, Hwayang-Dong 1, Kwangjin-Ku, Seoul, Korea 143-701.
E-mail: yoongho@konkuk.ac.kr
** Correspondence to: Prof. Dongsoo Koh, Department of Applied Chemistry,
Dongduk Women’s University, Seoul, Korea 136-714. E-mail: dskoh@dongduk.ac.kr
†
H. Jung and S. Ahn contributed equally to this work.
Experimental
a Division of Bioscience and Biotechnology, BMIC, Konkuk University, Seoul 143-701,
Korea
Syntheses
Typical synthetic procedures for the polymethoxylated
b Department of Herbal Crop Research, National Institute of Horticultural and
Herbal Science, Rural Development Administration, Eumseoung 369-873, Korea
naphthochalcones bearing
a pyrazoline-1-carbothioamide
moiety listed in Fig. 2 are summarized in Scheme 1. As a
representative example, the synthetic procedure for deriva-
tive 1, 5-(2,3-dimethoxyphenyl)-3-(1-hydroxynaphthalen-2-yl)-
c Department of Applied Chemistry, Dongduk Women’s University, Seoul 136-714,
Korea
Magn. Reson. Chem. 2015, 53, 383–390
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H. Jung et al.
Figure 2. Structures, names, and mass data of polymethoxylated naphthochalcones 1–18 bearing pyrazoline-1-carbothioamide moieties.
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1
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H and C NMR spectral assignments of polymethoxylated naphthochalcones
Scheme 1. The procedure used to prepare polymethoxylated naphthochalcones 1–18 bearing pyrazoline-1-carbothioamide moieties.
The crude solid was purified by recrystallization from ethanol to af-
ford pure pyrazoline (IV, yield 86%, mp 127–128 °C). Phenyl isothio-
cyanate (V, 68 mg, 0.5mmol) and pyrazoline (IV, 174 mg, 0.5mmol)
were dissolved in 15 ml of anhydrous ethanol, and the reaction
mixture was refluxed for 2 h. After cooling to room temperature,
the resulting solid was filtered and purified by recrystallization in
ethanol to give a pure compound of 1 (yield 80%, mp 212–214
respective parameters were 3 s, 15.0 μs, 20 964 Hz, 64 K, and
0.640Hz/point. For two-dimensional (2D) experiments, such as
correlation spectroscopy (COSY), heteronuclear multiple-quantum
correlation (HMQC), and heteronuclear multiple-bond correlation
[12]
2 1
(HMBC), all data points (t × t ) were acquired with 2 K × 256.
The long-range coupling time for HMBC was 70 ms. Zero-filling of
2 K and the sine-squared bell window function were applied before
[
13,14]
°C). The other derivatives were synthesized using similar methods.
Fourier transformation using XWin-NMR (Bruker).
were analyzed using Sparky.
All NMR data
[
15]
Nuclear Magnetic Resonance Spectra
General Experimental Procedures
The synthetic polymethoxylated naphthochalcones bearing a
pyrazoline-1-carbothioamide moiety except derivatives 3 and 8
were dissolved in deuterated dimethyl sulfoxide, and derivatives
To confirm the structures of the 18 derivatives, high-resolution
electron impact ionization mass spectrometry was performed on
a JMS700 spectrometer (JEOL, Tokyo, Japan) at the Korea Basic
Science Institute at Daegu, Korea.
1
13
3
and 8 were dissolved in deuterated chloroform. The H and
C
chemical shifts of the deuterated solvent were referenced to
tetramethylsilane. Nuclear magnetic resonance samples were pre-
pared at approximately 50 mM and transferred to a 2.5-mm NMR
tube for spectral analysis. All NMR experiments were carried out
on an Avance 400 spectrometer system (9.4 T; Bruker, Karlsruhe,
Results and discussion
All of the polymethoxylated naphthochalcones bearing
a
1
Germany) at 25 °C. For the one-dimensional (1D) H NMR spectra,
pyrazoline-1-carbothioamide moiety shown in Fig. 2 are novel.
The number of methoxy groups ranged from two to five. The
the relaxation delay, 90° pulse, spectral width, number of
data points, and digital resolution were 1 s, 11.8μs, 5555 Hz, 32 K,
and 0.339Hz/point, respectively. For the C NMR spectra, the
procedure used to assign the NMR data of derivative 3 was as
13
13
follows. The
C peak shifted the farthest downfield was
Figure 3. The partial HMBC spectrum of derivative 3 collected in deuterated chloroform. Long-range coupling between C-2’’ (148.7 ppm) and 2’’-OMe
4.10 ppm), and C-2 (145.0 ppm) and 2-OMe (3.98 ppm), and C-3 (152.5 ppm) and 3-OMe (3.88 ppm).
(
Magn. Reson. Chem. 2015, 53, 383–390
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H. Jung et al.
1
1
70.8 ppm and was assigned as thioketone. The next farthest
frequency)> 7–12> 13–18 (low frequency). While the H chemical
1
3
downfield C peak was 158.0 ppm and was determined to be
the C-3 of pyrazoline (named C-py-3). It was long-range coupled
to four H peaks at 3.39, 4.02, 6.36, and 7.23 ppm in the HMBC
spectrum. Because the two protons at 3.39 and 4.02 ppm are
attached to the carbon at 42.4ppm directly in HMQC, they were
assigned as the methylene protons of H-py-4. The H peak at
shifts of H-py-4a are in the order derivatives 13–18 > 1–6 > 7–12,
those of H-py-4b are in the order 1–6> 13–18 > 7–12. For the pro-
ton chemical shifts of the carbothioamide group, derivatives 7–12
are observed at a lower frequency than derivatives 1–6 and 13–18.
The chemical shifts of all of the hydroxyl protons are observed at
approximately 10.5 ppm, but because derivatives 3 and 8 were
dissolved in chloroform, their hydroxyl groups are found at
10.8 ppm. These findings will help us identify new naphthochalcones
bearing pyrazoline-1-carbothioamide moieties in the future.
1
1
13
6.36 ppm is one-bond correlated with the
C peak at
57.6ppm, which is the second upfield shifted peak excluding
the methoxyl groups, so it is H-py-5. The remaining proton,
.23 ppm, should be H-3’. The proton and carbon peaks
7
contained in the naphthalene group were determined based
on the correlations of the COSY and HMBC spectra. The two
carbons at 145.0 and 118.1 ppm were long-range coupled to
H-py-5, so the former was assigned as C-2 and the latter as
(A)
(B)
13
C-6. H-py-4 showed long-range coupling with two C peaks at
07.6 and 134.8 ppm in the HMBC. Because the former was
1
already determined to be C-2’ based on the correlations of the
COSY and HMBC spectra, the carbon at 134.8ppm was assigned
as C-1. The three proton peaks at 6.82, 6.86, and 7.01ppm were
correlated with each other in the COSY spectrum, so they are
H-4, H-5, or H-6. Based on the interpretation of the COSY and
HMBC spectra, they were assigned as H-6, H-4, and H-5, respec-
1
3
tively. Because the C peak at 152.5 ppm showed long-range
1
coupling with the H peak at 7.01 ppm (H-5), it was identified
as C-3. Because the two carbons at 128.1 and 148.5 ppm were
long-range coupled to H-5’’ and H-4’’, respectively, they were
assigned as C-1’’ and C-2’’, respectively. C-2’’ showed long-range
couplings with two protons at 7.11 and 8.98 ppm. They may be
H-4’’ and/or H-6’’. While the former shows doublet of doublet of
doublet (ddd), the latter does doublet of doublet (dd). Therefore,
two protons at 7.11 and 8.98 ppm were assigned H-4’’ and H-6’’,
respectively. Because four protons at 6.98, 7.00, 7.11, and 8.98
showed cross peaks in the COSY spectrum, they should be H-3’’,
H-4’’, H-5’’, and/or H-6’’. H-4’’ and H-6’’ were determined as men-
tioned previously already; thus, two protons at 6.98 and 7.00ppm
could be assigned to be H-3’’ and/or H-5’’. C-1’’ was long-range
1
coupled with the H peak at 6.98ppm in the HMBC spectrum.
Therefore, it should be H-3’’. As a result, the remaining proton at
7.00 ppm was determined to be H-5’’. Derivative 3 contains three
methoxy groups. As shown in Fig. 3, three peaks in the partial HMBC
1
spectrum provide information about three methoxy groups. The H
peaks at 3.88, 3.98, and 4.10 ppm can be assigned as 3-OMe, 2-OMe,
1
and 2’’-OMe, respectively. Likewise, the two H peaks at 9.72 and
Figure 4. The partial HMBC spectrum of derivative 3 collected in
deuterated chloroform. (A) Long-range coupling between NH (9.72 ppm)
and C-6’’ (119.5 ppm)/C-2’’ (148.5 ppm) and (B) long-range coupling
between OH (10.82 ppm) and C-2’ (107.6 ppm)/C-9’ (124.3 ppm)/C-1’
(154.8 ppm).
10.82 ppm show long-range coupling peaks, as shown in Fig. 4A
and 4B, in which the former peak is coupled to C-2’’ and C-6’’ and
the latter peak is coupled to C-1’, C-2’, and C-9’. Therefore, they
are NH and OH, respectively. These assignments agreed with the
[16]
reported results. The important correlations obtained from the
COSY and HMBC spectra of derivative 3 are shown in Fig. 5. The
NMR data for the other derivatives were determined in a similar
1
13
manner. Their complete H and C NMR data are listed in Tables 1
1
13
and 2, respectively. For reference, the H and C NMR spectra are
provided as supporting information.
The 18 derivatives can be placed in three groups: 1–6 (2,3-
dimethoxy groups), 7–12 (2,4-dimethoxy groups), and 13–18 (3,5-
13
dimethoxy groups). The C chemical shifts of py-3 are in the order
derivatives 7–12 (high frequency) > 1–6 > 13–18 (low frequency).
For C-py-4 and C-py-5, derivatives 13–18 are in the high-frequency
group, and derivatives 7–12 are in the low-frequency group. The
1
1
3
C chemical shifts of thioketone, C-1’ and C-1’’, do not differ. The
H chemical shifts of py-5 are in the order derivatives 1–6 (high
Figure 5. The important correlations obtained from the COSY (dot lines)
and HMBC (solid lines) spectra of derivative 3.
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Copyright © 2015 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2015, 53, 383–390

1
13
H and C NMR spectral assignments of polymethoxylated naphthochalcones
Magn. Reson. Chem. 2015, 53, 383–390
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/mrc

H. Jung et al.
wileyonlinelibrary.com/journal/mrc
Copyright © 2015 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2015, 53, 383–390

1
13
H and C NMR spectral assignments of polymethoxylated naphthochalcones
Magn. Reson. Chem. 2015, 53, 383–390
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/mrc

H. Jung et al.
[
9] S. Y. Shin, H. Yoon, S. Ahn, D. W. Kim, D. H. Bae, D. Koh, Y. H. Lee, Y. Lim.
Acknowledgements
Int. J. Mol. Sci. 2013, 14, 16970.
This work was supported by the Priority Research Centers Program
[10] S. Y. Shin, H. Yoon, S. Ahn, D. W. Kim, S. H. Kim, D. Koh, Y. H. Lee, Y. Lim.
Bioorg. Med. Chem. 2013, 21, 4250.
(NRF, 2012–0006686) and Agenda Program (RDA, Agenda 13–46,
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