1H and 13C NMR spectral assignments of 1,1′-(((ethane-1,2-diylbis(oxy))bis(4,1-phenylene))bis(methylene))-bispyridinium and -bisquinolinium bromide derivatives

Full text of DOI:10.1002/mrc.4468

Letters - spectral assignments
Published online in Wiley Online Library: 11 July 2016
(wileyonlinelibrary.com) DOI 10.1002/mrc.4468
1
13
H and C NMR spectral assignments of 1,1′-
(((ethane-1,2-diylbis(oxy))bis(4,1-phenylene))
bis(methylene))-bispyridinium and
-bisquinolinium bromide derivatives
Keywords: NMR; PHENOXYETHANE; SALTS; BIS-QUINOLINIUM; BIS-PYRIDINIUM
72 h at reflux of 1,2-bis(4-bromomethylphenoxy)ethane (8) to afford
Introduction
10a-l.
High levels of total choline (cho) and phosphocholine (Pcho) are
steadily found in aggressive cancers.[1,2] Choline kinase (ChoK)
catalyzes choline phosphorylation to produce phosphocholine that
will produce ultimately phosphatidylcholine, which is not only a
major phospholipid in eukaryotic cell membranes but is also a
NMR techniques
Proton nuclear magnetic resonance and 13C NMR data (chemical
shifts multiplicity and coupling constants) for compounds 10a-l
are shown in the following tables. Unambiguous assignments for
all NMR signals were made through the combined information of
one-dimensional and two-dimensional NMR experiments such as
DEPT, HSQC and HMBC.
substrate to produce lipid second messengers such as phosphatidic
acid and diacylglycerol.[1–3] ChoK plays a crucial role in human
carcinogenesis, and its selective inhibition (ChoK-α but not ChoK-β
is overexpressed in various cancers) is considered an efficient
antitumour strategy.[1,3,4] The reported crystal structure of human
ChoK and recent descriptions about the ChoK active site provide
inestimable information for designing new inhibitors.[5–7] The syn-
thesis and biological evaluation of a novel family of compounds
derived from 1,1′-(((ethane-1,2-diylbis(oxy))bis(4,1-phenylene))bis
(methylene))-bispyridinium or -bisquinolinium bromide as selec-
tive inhibitors of human ChoK α1 have been recently described.[8]
In this paper, we describe the 1H NMR and 13 C NMR unequivocal
assignments of these novel symmetrical biscationic compounds.
Proton nuclear magnetic resonance spectra were recorded on a
VarianInovaUnity (300 MHz), VarianDirect Drive (400 MHz) and/or
VarianDirect Drive (500 MHz). Chemical shifts (δ) are quoted in parts
per million (ppm) and are referenced to the residual solvent
peak: CD3OD, δ = 3.31 ppm (1H), δ = 49.05 ppm (13C); DMSO-d6,
δ = 2.50 ppm (1H), δ = 39.5 ppm (13C). Spin multiplicities are given
as singlet (s), wide singlet (ws), doublet (d), double doublet (dd),
double double doublet (ddd), triplet (t), double triplet (dt),
pseudotriplet (pt), cuadruplet (c) and multiplet (m). Coupling con-
stants (J) are given in hertz. 13C NMR spectra were recorded on a
VarianDirect Drive (400 MHz) and VarianDirect Drive (500 MHz).
The following parameters were used in DEPT experiments: PW
(135°), 9.0 ms; recycle time, 1 s; 1/2J (CH)= 4 ms; 65 536 data points
acquired and transformed from 1024 scans; spectral width, 15 KHz;
and line broadening, 1.3Hz. HMBC spectra were measured with a
pulse sequence gc2hmbc (standard sequence, Agilent Vnmrj_3.2A
software) optimized for 8 Hz (inter-pulse delay for the evolution of
long-range couplings: 62.5ms). The HSQC spectra were measured
with a pulse sequence gc2hsqcse (standard sequence Agilent
Vnmrj_3.2A software).
Experimental
Synthesis
Scheme 1 represents the previously reported synthetic pathway
followed in the preparation of the novel family of compounds
derivative of 1,1′-(((ethane-1,2-diylbis(oxy))bis(4,1-phenylene))bis
(methylene))-bispyridinium or -bisquinolinium bromide (10a-l)
containing a pair of oxygen atoms in the spacer of the linker
between the biscationic moieties.[8] The synthesis of the compounds
was carried out by microwave-assisted reactions that allowed us to
improve time and yields. The addition of 1,2-dibromoethane to the
4-methylphenol (6) (previously treated with NaOH) under
microwave irradiation (130 °C, 28 min) provides the 1,2-bis(p-
methylphenoy)ethane (7). Then, bromination in the methylene of
7 with N-bromosuccinimide (NBS) and dibenzoylperoxide in CCl4
also under microwave irradiation (120 °C, 21 min) gives the 1,2-
bis(4-bromomethylphenoy)ethane (8). Finally, the cationic heads
(4-substituted pyridine derivative (9a-c), quinuclidine derivative
(9d-e) or 4-substituted quinoline or 7-chloro-4-substituted quino-
line (9f-l), previously synthesized) are introduced by means of a
simple SN2 reaction in acetonitrile under argon atmosphere during
Results and discussion
To facilitate the analysis of all biscationic compounds, they
have been gathered in different tables according to the cationic
head; thus, Tables 1 and 2 show bispyridinium (10a-c) and
-bisquinuclidinium (10d-e) salts. Bisquinolinium (10f-l) salts are
shown in Tables 3 and 4. At the same time, bisquinolinium
compounds will be divided into two series to easily tackle the
assignments for all NMR signals: series 1 [bisquinolinium salts with
aromatic substituent in R4 position (10f-i)] and series 2
Magn. Reson. Chem. 2016, 54, 905–911
Copyright © 2016 John Wiley & Sons, Ltd.

S. SCHIAFFINO-ORTEGA ET AL.
Scheme 1. General synthetic pathway for compounds 10a-l.
[bisquinolinium salts with no aromatic substituent in R4 position
(10j-l)].
Figure 1 shows family of compounds derivative of both
bispyridinium and -bisquinuclidinium salts (10a-e) as well as the
number scheme of the compounds used.
nitrogen and mainly (ii) the phenomenon of resonance of the ar-
omatic ring that deshields those protons, and therefore, they will
appear at lower field. It is worth mentioning the presence in
position 4 of the pyridine ring of a tertiary amine (electron-donat-
ing group) influences the resonance by stabilizing the positive
charge.
Table 1 shows 1H-NMR chemical shifts (δ, ppm) for compounds
10a-e. It can be observed that there is a well-defined area where
resonance of the protons of the aromatic spacer and pyridine
(pyridine = pyr) (10a-b) at a higher field can be located at the
methylene groups bonded to the quaternary nitrogen (CH2-N+)
and oxygen (CH2-O) and finally, a defined zone where it is possible
to find the protons of pyrrolidine (pyrrolidine = pirr) and
quinuclidine (quinuclidine= q). Signals corresponding to protons
that are closer to the positive nitrogen of the pyridine (H-2,6pyr)
appear at a lower field because of the summation effect of both
the deshielding of the ring and the induction of the positive nitro-
gen. Signals from hydrogen atoms in the spacer, H-2, 6 and H-2′,6′,
appear as a doublet, an AB system typical of p-substituted aromatic
systems, a field of 7.01 ppm, and they are coupled with H-3,5 and
H-3′,5′ (δ = 7.34 ppm) with a coupling constant of 8.73 Hz. The
methylene directly attached to the cationic head (CH2-N +) appears
as a singlet at δ 5.28 ppm, while the methylene bonded to oxygen
(CH2-O) appears as a singlet at higher field (δ = 4.32ppm). Com-
pound 10a pyridine proton signals are slightly higher (H-2,6pyr
and H-3,5pyr; δ 8.20 and 6.99 ppm, respectively) owing to the con-
tribution of the dimethylamino group, which unlike the pyrrolidine
has no shielding effect. However, the signals corresponding to the
spacer have constant values because the distance between the
pyridine ring and the benzyl groups of the spacer does not feel
the influence of the cationic head. There are two factors that
influence the chemical shift of the protons of the pyridine ring:
(i) there is a small contribution of the positive charge of the
Quinuclidine is another type of cationic head used: a bicyclic
amine with a substituent in position 3 in the case of the com-
pound 10e. As a fully saturated compound, quinuclidine signals
appear as multiplets in the range of alkanes (δ 2 a 4 ppm). As a
symmetrical structure, quinuclidine in compound 10d, protons
are equivalent for the case of (H-2,6,7q and H-3,5,8q), but that
is not the case for the proton where both saturated cycles come
together, H-4q. The signals for the hydrogen atoms correspond-
ing to H-2,6,7q appear as a multiplet at δ 3.48 ppm, and they
are coupled with H-3,5,8q (δ = 2.01) and H-4q (δ = 2.18 ppm).
When an OH group is taking the position 3 up, bicycle symmetry
is lost, and as a result, more but not defined signals appear and
coupling constants are impossible to be determined. In the case
of the compound 10e, the presence of two diastereomers (RR/
SS and RS) that cannot be separated by conventional methods
prevents to allocate signals unequivocally, although it clearly
can be said that the presence of the OH group translates the
chemical shift of all protons of the quinuclidine to a lower
magnetic field. Quinuclidine of both compounds, 10d,e, has a
clear influence on the signals of the aromatic hydrogen atoms
of the spacer; thus, those signals appear at a lower field (H-3,5
and H-3′, 5′ resonate as a doublet at δ 7.48 ppm, while H-2,6
and H-2′,6′ resonate as a doublet at δ 7.13 ppm. The coupling
constant is 8.66 Hz). Even the methyl groups attached to oxygen
(CH2-O) resonate at slightly downfield (δ = 4.35 and 4.32ppm,
respectively). This may be because the quinuclidine is not an
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NMR phenoxyethane bis-salts derivatives
Magn. Reson. Chem. 2016, 54, 905–911
Copyright © 2016 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/mrc

S. SCHIAFFINO-ORTEGA ET AL.
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Copyright © 2016 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2016, 54, 905–911

NMR phenoxyethane bis-salts derivatives
Magn. Reson. Chem. 2016, 54, 905–911
Copyright © 2016 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/mrc

S. SCHIAFFINO-ORTEGA ET AL.
Table 4. 13C-NMR chemical shifts (δ, ppm) and coupling constants (J, Hz) of 1,1′-(((ethane-1,2-diylbis(oxy))bis(4,1-phenylene))bis(methylene))-
bisquinolinum bromide (10f-l)
Cationic head
Compound
C-1,1′
10f δ (ppm)
161.47
117.30
130.63
128.64
68.85
59.94
148.54
107.73
160.80
122.29
120.97
127.85
135.51
130.15
141.68
—
10 g δ (ppm)
161.48
117.30
130.69
128.52
68.84
60.09
148.77
108.36
160.92
122.41
121.13
128.20
135.68
130.00
141.68
—
10 hδ (ppm)
161.58
117.41
130.77
128.24
68.86
59.91
148.95
107.93
160.51
120.68
131.80
130.59
141.90
120.45
142.51
—
10iδ (ppm)
161.59
117.40
130.85
128.15
68.85
60.05
149.22
108.57
160.65
120.82
131.68
128.71
142.06
120.61
142.50
—
10jδ (ppm)
161.34
117.22
130.48
128.98
68.84
58.99
146.48
104.55
161.91
121.41
120.33
127.04
135.52
130.44
142.10
56.06
29.37
29.23
—
10 kδ (ppm)
161.44
117.32
130.59
128.57
68.85
59.00
146.77
105.00
161.56
119.88
119.78
127.45
141.82
132.31
142.95
56.12
29.28
29.16
—
10 lδ (ppm)
157.92
117.29
130.45
128.68
68.83
59.06
146.91
104.64
161.37
120.16
119.73
127.71
141.76
131.76
142.45
—
C-2,6 e C-2′,6′
C-3,5 e C-3′,5′
C-4,4′
CH2
+N-CH2
C-2quin
C-3quin
C-4quin
C-4a quin
C-5quin
C-6quin
C-7quin
C-8quin
C-8a quin
C-2,7az
C-3,6az
—
—
—
—
—
C-4,5az
—
—
—
—
—
C-2,5pirr
C-3,4pirr
C-1 ph
—
—
—
—
55.43
24.64
—
—
—
—
—
—
—
150.14
132.75
127.73
130.28
46.75
148.81
132.72
129.28
135.58
46.53
149.76
132.92
127.72
128.35
46.87
148.45
132.88
129.33
135.92
46.69
—
—
C-2,6 ph
C-3,5 ph
C-4 ph
—
—
—
—
—
—
—
—
—
N-CH3
—
—
—
contrary, the methylene group fixed to the cationic head appears
at higher field (δ = 4.43 ppm), compared with compounds 10a,b.
With respect to 13C-NMR that can be seen in Table 2, the signals
that appeared at lower field belong to quaternary carbons C-1,1′
(δ = 161.79–169.86 ppm) and C-4,4′ (δ = 121.54–129.97 ppm),
and they are followed in order of increasing magnetic field with
the peaks belonging to the pyridine C-2,6pyr (δ = 143.68–
143.76 ppm); C-3,5 and C-3′,5′ (δ = 131.92–131.98 ppm); C-2,6 and
C-2′,6′ (δ = 117.14–125.11 ppm); and finally, C-3,5pyr (δ = 109.93–
110.51 ppm) as the last character of the aromatic group.
The family of compound derivative of 1,1′-(((ethane-1,2-diylbis
(oxy))bis(4,1-phenylene))bis(methylene))-bisquinolinum bromide
(10f-l) is shown in Fig. 2. As said, bisquinolinium compounds have
been divided into two series to easily tackle the assignments for
all NMR signals: series 1 [bisquinolinium salts with aromatic substit-
uent in R4 position (10f-i)] and series 2 [bisquinolinium salts with
no aromatic substituent in R4 position (10j-l)]. It can be noticed that
all protons of the spacer, aromatics and methylene groups resonate
at lower field when an aromatic substituent is present in position 4
of the quinoline (quinoline= quin). H-2,3quin resonates at lower
frequencies (high field) in series 1 with respect to series 2, because
the aromatic substituent in position 4 deshields those hydrogens.
H-8, 7, 6, 5 of series 2 appear at lower field than those in series 1
Figure 1. Family of compound derivative of 1,1′-(((ethane-1,2-diylbis(oxy))
bis(4,1-phenylene))bis(methylene))-bispyridinium and -bisquinuclidinium
bromide (10a-e).
aromatic system and therefore cannot delocalized electronic
charge on the aromatic ring; consequently, the deshielding effect
upon the benzyls and CH2 bounded to oxygen is stronger. On the
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NMR phenoxyethane bis-salts derivatives
Figure 2. Family of compounds derivative of 1,1′-(((ethane-1,2-diylbis(oxy))bis(4,1-phenylene))bis(methylene))-bisquinolinum bromide (10f-l).
because the aniline has a shielding effect. The chlorine in position 7
of the quinoline barely has influence on the chemical shift of the
neighboring protons. However, the chlorine atom in position 4 of
the aniline has a greater influence on the protons of the quinoline
than on the protons of the aniline; thus, H-3 and CH2-N+ appear
at lower field when halogen is presented. It is assumed that the
spatial arrangement of the ring results in the approach of the
chlorine atom to these protons producing a deshielding effect
thereon.
* Correspondence to: Luisa Carlota Lopez-Cara and Antonio
Entrena Guadix, Departamento de Química Farmacéutica y
Orgánica, Facultad de Farmacia, Universidad de Granada,
Campus de Cartuja, 18071 Granada, Spain.
E-mail: lcarlotalopez@ugr.es; aentrena@ugr.es
Received: 27 April 2016; Revised: 28 May 2016; Accepted: 31 May 2016
References
According to the results shown in Table 4, those carbons of the
spacer, aromatic and methylene groups neighboring the oxygen
atoms are not influenced by substituents that may be introduced in
the quinoline. In series 1 (10f-i), a chlorine atom in position 7 of the
quinoline influences the chemical shift of C-5,6quin and the same
C-7quin, leading to a lower magnetic field. In series 2 (10j-l), the
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reduces the chemical shift (higher field) of the C-4quin in relation
to compounds of the series 2, and it influences the chemical shift
of C-2,3quin and CH2-N+. The presence of chlorine in position 4 of
the aniline has a deshielding effect on C-3,5ph and C-4 ph.
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Granada, Spain
Magn. Reson. Chem. 2016, 54, 905–911
Copyright © 2016 John Wiley & Sons, Ltd.
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