Readily functionalized AAA-DDD triply hydrogen-bonded motifs

Article abstract of DOI:10.1039/c8ob00479j

Herein we present a new, readily functionalized AAA-DDD hydrogen bond array. A novel AAA monomeric unit (3a-b) was obtained from a two-step synthetic procedure starting with 2-aminonicotinaldehyde via microwave radiation (overall yield of 52-66%). ¹H NMR and fluorescence spectroscopy confirmed the complexation event with a calculated association constant of 1.57 × 10⁷ M^-1. Likewise, the usefulness of this triple hydrogen bond motif in supramolecular polymerization was demonstrated through viscosity measurements in a crosslinked supramolecular alternating copolymer.

Full text of DOI:10.1039/c8ob00479j

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10.1039/C8OB00479J.
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ISSN 1477-0520
COMMUNICATION
Takeharu Haino et al.
Solvent-induced emission of organogels based on tris(phenylisoxazolyl)
benzene
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Readily Functionalized AAA-DDD Triply Hydrogen-Bonded Motifs
Feng Tong,a Iamnica J. Linares-Mendez,a,b Yi-Fei Han,a James A. Wisner,a,b Hong-Bo Wang.a,b
*
Received 00th January 20xx,
Accepted 00th January 20xx
Herein we present a new readily functionalized AAA-DDD hydrogen bond array. The novel AAA monomeric unit (3a-b) was
obtained from a two-step synthetic procedure starting with 2-aminonicotinaldehyde and via microwave radiation (overall
yield of 52-66%). 1H NMR and fluorescence spectroscopy confirmed the complexation event with a calculated association
constant of 1.57 x 107 M-1. Likewise, the usefulness of this triple hydrogen bond motif into supramolecular polymerization
DOI: 10.1039/x0xx00000x
www.rsc.org/
was demonstrated through viscosity measurements in
a crosslinked supramolecular alternating copolymer.
alternating polymers and polymeric blends.12 Likewise,
complementary complexes with all hydrogen-bonded acceptor
(A) and donor (D) sites arranged in an AAA-DDD way, exhibit
high association constants.13-16, 18
Introduction
Supramolecular polymerization represents a significant
evolution in polymer science. Characterized by being
a
In this sense, both Zimmerman and Leigh groups have
developed notorious attempts to achieve complementary
arrays readily accessible for supramolecular polymers.
Zimmerman and coworkers reported the synthesis of an AAA
monomer starting from (trimethoxy)methylbenzene, and
malononitrile in pyridine, followed by an aminolysis, catalytic
dynamic equilibrium, it allows to reversibly tune polymer’s
viscosity, aggregation, and morphology through the influence
of external stimuli without compromising the chemical
integrity of their components.1 In this sense, there are good
examples of this materials with a desired and controlled
response towards temperature change,2 pH,3 competitive
binders,4 and light.5 One of the best applications known is the
creation of self-healing rubber.6 Additionally, supramolecular
polymer’s synthesis is as complicated as the synthesis of their
monomers; since the polymeric network is a result of the
intermolecular interactions between these units. In other
words, the polymerization step does not require any synthetic
procedure such as cation/anion living polymerization,
metal/radical catalysis, or polycondensation, as covalent
polymers do.1, 7
hydrogenation
acetophenone.14 On the other hand, Leigh’s AAA system
started with 2,6-diamino-3,5-diiodopyridine and 2-
and
a
Friedländer
reaction
with
formylphenyl boronic acid via double Suzuki coupling-
cyclization-aromatization.15 Later, this group applied Pd cross-
coupling of 2-chloro-3-cyano-1,8-naphthyridine and 2-
aminopyridine, followed by ring closure to afford another AAA
system.16
In our previous work it is possible to find both coplanar17
and helical18 AAA-DDD arrays; however, these systems
required several synthetic steps which defeat their usefulness
in the construction of supramolecular polymers. Herein, we
present some readily functionalized AAA-DDD triply hydrogen-
bonded motifs, which can also be employed for the
construction of supramolecular polymers.
From all intermolecular interactions employed in
supramolecular polymerization, hydrogen bonds stand out due
to their high directionality, and the strong binding achieved
when several are used within an array.7, 8 Self-complementary
hydrogen-bonded arrays have gained high notoriety since their
synthesis seem straightforward.9 However, this approach may
have two inconveniences: 1) intramolecular interactions that
restrict polymer chain growth;10 and, 2) to be limited to
homopolymers.11 Instead, the high fidelity in complementary
hydrogen-bonded arrays has favoured the creation of
Results and Discussion
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The synthesis of the novel AAA systems presented in this
work is a two-step procedure starting with the synthesis of 2-
cyanoacetamide ( ) from ethyl cyanoacetate (95-99%). The
mixture of and 2-amino-3-pyridinecarboxaldehyde under
basic catalysis (10% NaOH) at 80 afforded 2-
1
1
ºC
aminonaphthyridine-3-carboxamide (
83%). Intermediate in
2
) in good yields (70-
1,1-dimethoxy-N,N-
2
dimehtylmethanamine (DMFDMA) was heated under
microwave at 110 C for 40 minutes at 150 psi to yield our
desired AAA system (75-85%), Scheme 1. The DDD system
employed was prepared as reported by Wang and
º
(4)
coworkers17 from p-methoxybenzaldehyde and ethyl 2-
amidinoacetate hydrochloride. The purity of all products was
corroborated by 1H NMR Spectroscopy and Liquid
Chromatography-Mass Spectrometry.
Single crystal X-ray diffraction confirmed the AAA display in
compound 3a. Such crystal was obtained by slow evaporation
from a saturated solution in chloroform. Compound 3a
belongs to the P 21/c space group (monoclinic) with four
molecules per unit cell. Table S1 show all crystal parameters of
this compound crystal structure. As expected, the
naphthyridine backbone that holds the three hydrogen
bonding acceptor sites can be considered planar since most
significant deviation from the least square plane of all heavy
atoms is no larger than 0.1 Å, Figure 1. Along the crystal lattice,
two types of hydrogen contacts were observed: a bifurcated
hydrogen contact between the oxygen atom with two C-H
moieties (O1∙∙∙H10A-C10 = 3.24 Å,
O1∙∙∙H11A-C11 = 3.44 Å, O∙∙∙H-C = 140.4
contacts between naphthyridine nitrogen atoms with aromatic
C-H moieties (N1∙∙∙H1A-C1 = 3.52 Å, N∙∙∙H-C = 145.8 and
N3∙∙∙H2A-C2 = 3.45 Å, N∙∙∙H-C = 139.8 ). Likewise, π−π
∠
O∙∙∙H-C = 159.9º and
∠
º); and, two N∙∙∙H-C
∠
º
∠
º
stacking between two symmetry-related molecules aligned in
an antiparallel fashion was observed (the distance between
least square planes of all heavy atoms is 3.48 Å), Figure S17.
As previously reported, compound
4 (DDD monomer) is
present as two tautomeric forms in solution: 1,4-dihydro and
3,4-dihydro with a 52:48 ratio in CDCl3 at 298 K, respectively.17
This tautomer’s distribution changed after the addition of 3a
;
wherein the 1,4-dihydro tautomer was favoured up to a ratio
greater than 99:1 when more than one equivalent was added,
Figure 2. The downfield shifts of the N-H protons in
4 were in
agreement with the formation of a hydrogen-bonded AAA-
DDD array as designed. These changes were highly noted
2 | Org. Biomol. Chem., 2018, 00, 1-3
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before one equivalent of 3a was added. After one equivalent with 1,6-diisocyanatohexane in the presence of dibutyltin
of 3a, changes in the chemical shifts were unnoticed. This dilaurate (DBTDL) as a catalyst, Scheme 2. On the other hand,
observation indicated
a
highly stable complex which
7 contained the DDD units, and it was characterized by a
complexation constant was unable to be calculated via 1H NMR trifurcate structure. This monomer was synthesized starting
titration, Figure 3.20
Fluorescence titration determined the association constant
of the 3a∙4 complex. Compound 3a in solution showed a high-
intensity fluorescence at 392 nm that decreased as
added, Figure 4. The 1:1 molar ratio of 3a and in the complex
structure was confirmed through a Job plot; wherein the
average molar fraction of the guest ( ) at the plot’s maximum
4 was
4
4
was 0.46 from three titration experiments, Figure S21.
Likewise, the data obtained from the fluorescence titrations
were submitted to an iterative fitting process with a 1:1
complexation model to calculate the 3a∙4 association constant
(Ka), as described in the following equation:
ꢀꢄꢅꢆ ꢇ ꢀꢂ
2ꢈꢉꢊꢋ
1
ꢎꢏ
ꢈ
ꢋ
ꢈ ꢋ
ꢀ ꢁ ꢀꢂ ꢃ
ꢌ ꢉꢊ ꢃ ꢍ ꢃ
ꢈꢐꢈ
ꢋꢓ/ꢒ
ꢉꢊ ꢃ ꢍ ꢃ 1/ꢎꢏ ꢇ 4ꢈꢉꢊꢋꢈꢍꢋ ꢔ
ꢋ
ꢈ ꢋ
ꢑꢒ
ꢇ
wherein:
I0 and I are the emission intensities of the complex at
a selected wavelength in the absence and presence of
4
,
from benzene-1,3,5-tricarbonyl trichloride that provided a
planar backbone wherefrom the DDD units were built.
respectively; and, Ilim is the limiting value of the emission
intensity in the presence of an excess of 4.22 The good
correlation between the experimental data and the
complexation model (r2 values of 0.99, 0.99 and 0.99 from
three parallel titration experiments) corroborated the
expected 1:1 ratio for this complex structure, Figure 5. The
association constant value obtained was 1.57 ± 0.48 x 107 M-1
in chloroform at room temperature; which corresponds to a
binding energy (∆G = 9.79 ± 0.21 kcal∙mol-1). According to
Schneider and Sartorius’ model (wherein the energetic
contributions from primary and secondary hydrogen bond
interactions are 1.9 and 0.7 kcal∙mol-1, respectively),23 the
AAA-DDD array herein presented should have a ∆G of -8.4
kcal∙mol-1. In other words, the AAA-DDD array presented was
more stable than expected. Hence, there is a high likelihood of
supramolecular polymerization using this system.
Synthesis of monomer
reaction with 4-(2-hydroxyethoxy)benzaldehyde followed by
the synthetic procedure employed in compound with ethyl
7 was achieved by a condensation
4
2-amidinoacetate hydrochloride under basic conditions,
Scheme 3. Based on the structural features of both blocks, the
mixture of
5 and 7 was expected to arrange in a polymeric
network as illustrated in Figure 6. The formation of such
network was corroborated through viscosity measurements of
equimolar mixtures of
different concentrations, Figure 7. The double-logarithmic plot
of specific viscosity versus concentration shows: 1)
relationship between both variables; and, 2) a sharp slope
change from 1.02 when [ ]+[ ] < 0.036 mM to 3.00 when
]+[7] >0.036 mM, Figure 8. Both features are distinctive of
5 and 7 in 1,2-dichloroethane at
a
5
7
[
5
the formation of a supramolecular network.24 Finally,
polymerization eye-naked proof was observed after adding
a
In order to demonstrate the application of our AAA-DDD in
5
supramolecular polymerization, blocks
synthesized, Figure 6. Monomer comprised two AAA units at
opposite sides linked by linear aliphatic chain. Such
5 and 7 were
(37.5 mg) to a solution of
7 (50 mg in 0.5 mL of chloroform :
5
methanol 10:1 v/v). The resulting mixture showed a red color,
not observed in any of the
a
compound was achieved by the condensation of compound 3b
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and
a UV-spectrophotometer Agilent 8401. Fluorescent
Spectrometer F-700 (Hitachi High Technologies) was used to
acquire fluorescence spectra. Mass spectra were recorded
using electron impact ionization on a MALDI-TOF Mass
spectrometer SYNAPT G2 (Waters Corporation). X-Ray
diffraction data were collected on Bruker APEX-II CCD
diffractometer using monochromatic Mo-K
α radiation (λ =
0.71073 Å). Viscosity measurements were carried out with a
micro-Ubbelohde dilution viscometer at 298 K.
Synthesis
previous solutions. Likewise, the resulting mixture displayed
high viscosity after the solvent volume was reduced to one half
Figure 9.
N-butyl-2-cyanoacetamide, 1a. In a 50 mL round bottom flask
n-butylamine (293 mg, 3.99 mmol) and ethyl cyanoacetate
(453 mg, 4.00 mmol) were added and dissolved in anhydrous
ethanol under Argon atmosphere. The reaction mixture was
heated up to 80 ºC for 3 hours. After the mixture was cooled
Conclusions
down to room temperature, the solvent was removed under
reduced pressure. The product was obtained after
recrystallization with cold dichloromethane. Solid was filtered
and rinsed with cold ethanol. Yield = 533 mg, 95%. 1H NMR
A
new readily functionalized AAA monomer was
synthesized from 2-aminonicotinaldehyde in two steps with
the aid of microwave synthesis. Single crystal X-ray structure
confirmed the disposition of its acceptor sites and the
planarity of its backbone. The molecular recognition between
this new AAA system with a known DDD unit was studied by 1H
NMR and fluorescence titrations; wherein the association
constant obtained was 1.57 ± 0.48 x107 M-1 in chloroform at
(400 MHz, DMSO-d6) δ (ppm) 8.18 (bs, 1H), 3.58 (s, 2H), 3.06
(m, 2H), 1.42-1.35 (m, 2H), 1.32-1.33 (m, 2H), 0.87 (t, 3H, J =
7.3 Hz). 13C NMR (100 MHz, DMSO-d6)
δ
(ppm) 162.3, 116.7,
39.2, 31.3, 25.7, 19.9, 14.0.
2-cyano-N-(3-hydroxypropyl)acetamide, 1b. Synthetic
procedure as performed by Proença and Costa.19 Yield = 610
room temperature (
these binding units into a supramolecular polymer was
assessed through the synthesis of block units and . The
ꢀ
G = 9.79 ± 0.21 kcal∙mol-1). Integration of
mg, 99%.
2-amino-N-butyl-1,8-naphthyridine-3-carboxamide,
2a.
5
7
Synthetic procedure as reported by Domling and coworkers.20
A mixture of N-butyl-2-cyanoacetamide 1a (421 mg, 3.00
mmol), 2-amino-3-pyridinecarbaldehyde (366 mg, 3.00 mmol)
and NaOH (12 mg, 0.3 mmol) were dissolved in absolute
dependency of the mixture’s viscosity corroborated the
formation of a supramolecular network.
Acknowledgment
ethanol. The reaction mixture was heated to 80 ºC until
starting material consumption. The product desired
precipitated as a yellow solid once reaction mixture is cooled
We wish to thank the National Natural Science Foundation
of China (no.21302232), Wuhan Science and Technology
Bureau (No. 2015011701011599), Program for Excellent Young
Innovative Research Team in the Higher Education Institutions
of Hubei Province (No. T201726) for funding this research.
down to 0
times with cold dichloromethane. Yield = 610 mg, 83%. 1H
NMR (400 MHz, DMSO-d6) (ppm) 8.78 (dd, 1H, J = 4.4, 2.0
ºC. The solid was filtered and washed at least three
δ
Hz), 8.76 (bs, 1H), 8.41 (s, 1H), 8.14 (dd, 1H, J = 7.9, 2.1 Hz)
7.43 (bs, 2H), 7.22 (dd, 1H, J = 7.8, 4.4 Hz), 3.28 (td, 2H, J = 7.0,
5.5 Hz), 1.53 (m, 2H), 1.36 (m, 2H), 0.91 (t, 3H, J = 7.3 Hz). 13C
Conflict of Interest
NMR (100 MHz, DMSO-d6)
δ (ppm) 167.2, 159.1, 157.2, 154.5,
There are no conflicts to declare.
138.8, 137.9, 118.4, 116.6, 116.4, 39.3, 31.5, 20.1, 14.2.
2-amino-N-(3-hydroxypropyl)-1,8-naphthyridine-3-
carboxamide, 2b. In a round bottom flask 2-cyano-N-(3-
hydroxypropyl)acetamide 1b (1.25 g, 8.8 mmol) and 2-amino-
3-pyridinecarbaldehyde (976 mg, 8.0 mmol) were dissolved in
20 mL of absolute ethanol. Once dissolved, piperidine (7 mL)
Experimental
Reagents and Apparatus
All chemical and solvents were of reagent grade, purchased
from commercial sources and used directly without any
further purification. Microwave-assisted reactions were
carried out in a Discover SP 909155 (CEM Corporation). 1H
(400 MHz) and 13C (100 MHz) NMR spectra were recorded
using AscendTM 400 MHz spectrometer (Bruker). 1H and 13C
NMR spectra were referenced relative to tetramethylsilane
(TMS) using the residual non-deuterated NMR solvent signal.
UV-Vis absorption spectra were obtained on a ZF-I UV-Visible
spectrometer (Shanghai Gu Village electro-optical instrument)
was added and the reaction mixture was heated to 80 ºC for 5
h. Reaction completion was monitored by thin layer
chromatography. After completion, the reaction mixture was
cooled down to room temperature and the precipitate was
vacuum filtered to yield a pale-yellow powder. Product was
purified by washing at least two times with ethyl acetate and
absolute ethanol. Yield = 1.38 g, 70%. 1H NMR (400 MHz,
DMSO-d6) δ (ppm) 8.78 (dd, 1H, J = 4.4, 2.0 Hz), 8.76 (bs, 1H),
8.41 (s, 1H), 8.12 (dd, 1H, J = 7.9, 2.1 Hz), 7.44 (bs, 2H), 7.22
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(dd, 1H, J = 7.8, 4.4 Hz), 4.51 (t, 1H), 3.50 (m, 2H), 3.34 (m, 2H), and the reaction mixture was heated to 60
1.71 (m, 2H). 13C NMR (100 MHz, DMSO-d6)
(ppm)δ 167.25, material consumption was corroborated by thin layer
159.03, 157.19, 154.48, 138.83, 137.96, 118.43, 116.59, chromatography. Solvent was removed under reduced
116.36, 59.02, 37.05, 32.63. pressure and the product was isolated by flash
ºC until starting
δ
3-butylpyrimido[4,5-b][1,8]naphthyridin-4(3H)-one, 3a. In a chromatography with ethyl acetate : methanol (8:1 v/v)
35 mL microwave reaction tube 2-amino-N-butyl-1,8- mixture as eluent. Yield = 632mg, 76%. 1H NMR (400 MHz,
naphthyridine-3-carboxamide 2a (488 mg, 2.00 mmol) and 2.5 DMSO-d6) δ (ppm) 9.42 (s, 2H), 9.26 (dd, 2H, J = 4.1, 2.1 Hz),
mL of N,N-dimethylformamide dimethyl acetal (DMFDMA) 8.74 (d, 2H, J = 8.3 Hz), 8.67 (s, 2H), 7.69 (ddd, 2H, J = 8.2, 4.2,
were mixed and heated to 110 ºC for 40-45 minutes at 150 psi. 1.7 Hz), 7.08 (m, 2H), 4.05 (m, 8H), 2.91 (d, 4H, J = 6.6 Hz), 2.05
Once the reaction mixture cooled down to room temperature (d, 4H, J = 6.6 Hz), 1.32-1.15 (m, 8H); 13C NMR (100 MHz,
5 mL of ethanol was added. The product, that precipitated as DMSO-d6) δ 161.34, 158.37, 157.77, 157.61, 156.52, 153.40,
pale yellow solid, was filtered and rinsed with ethanol. Yield = 141.33, 139.35, 122.78, 121.75, 117.46, 61.56, 44.19, 30.47,
1
432 mg, 85%. H NMR (400 MHz, DMSO-d6)
δ (ppm) 9.45 (s, 29.77, 28.47, 26.35. mp =211.4 ºC.
1H), 9.26 (dd, 1H, J = 4.2, 2.1 Hz), 8.76 (dd, 2H, J = 8.2, 2.0 Hz), Tris(2-(4-formylphenoxy)ethyl)benzene-1,3,5-tricarboxylate,
8.73 (s, 1H), 7.70 (dd, 1H, J = 8.2, 4.1 Hz), 4.01 (t, 2H, J = 7.3 . A mixture of triethylamine (404 mg, 4.0 mmol) and 4-(2-
Hz), 1.72 (m, 2H), 1.35 (m, 2H), 0.93 (t, 3H, J = 7.4 Hz). 13C NMR hydroxyethoxy)benzaldehyde (548 mg, 3.3 mmol) in 8 mL of
(100 MHz, DMSO-d6) (ppm) 161.2, 158.3, 157.9, 157.6, 153.4, ethyl acetate was prepared in a 25 mL round bottom flask and
6
δ
141.4, 139.3, 122.8, 121.7, 117.3, 46.3, 31.1, 19.8, 14.0.
cooled down to 0 ºC. A solution of benzene-1,3,5-tricarbonyl
3-(3-hydroxypropyl)pyrimido[4,5-b][1,8]naphthyridin-4(3H)-
trichloride (265 mg, 1 mmol) in ethyl acetate was added
dropwise to the reaction mixture. Starting material
one, 3b. Synthetic procedure as performed for compound 3a
Yield = 625 mg, 75%. 1H NMR (400 MHz, DMSO-d6)
.
δ
(ppm) consumption was monitored by thin layer chromatography.
9.45 (s, 1H), 9.26 (dd, 1H, J = 4.2, 2.0 Hz), 8.76 (dd, 1H, J = 8.2, After reaction completion, the reaction mixture was filtered.
2.0 Hz), 8.67 (s, 1H), 7.70 (dd, 1H, J = 8.2, 4.1Hz), 4.65 (t, 1H, J = The solvent was removed from the filtrate under reduced
5.0 Hz), 4.09 (t, 2H, J = 7.0 Hz), 3.50 (q, 2H, J = 5.5 Hz), 1.89 (p, pressure, and the crude was submitted to flash
2H, J = 6.5 Hz). 13C NMR (100 MHz, DMSO-d6)
157.9, 157.5, 157.2, 153.2, 140.9, 138.9, 122.3, 121.3, 117.0, as eluent. The product is a yellow powder. Yield = 226 mg,
δ (ppm) 160.8, chromatography with petroleum ether : ethyl acetate (4:1 v/v)
1
57.9, 43.9, 31.2.
85%. H NMR (400 MHz, DMSO-d6) δ (ppm) 9.87 (s, 3H), 8.70-
Diethyl 2,6-diamino-4-(4-methoxyphenyl)-1,4-dihydropyridi- 8.60 (m, 3H), 7.85 (dd, 6H, J = 9.1, 2.2 Hz), 7.18 (d, 6H, J = 8.7
ne-3,5-dicarboxylate, 4. Synthetic procedure as reported by Hz), 4.72 (dd, 6H, J = 5.2, 3.3 Hz), 4.51 (dd, 6H, J = 5.1, 3.6 Hz).
Wang and coworkers.17 p-methoxybenzaldehyde (1.50 g, 11.02 Tris(2-(4-(2,6-diamino-3,5-bis(ethoxycarbonyl)-1,4-dihydropy-
mmol), ethyl 2-amidinoacetate hydrochloride (3.8 g, 22.80 ridin-4-yl)phenoxy)ethyl)benzene-1,3,5-tricarboxylate,
mmol), K2CO3 (3.34 g, 24.17 mmol) and 6 mL of DMF were Compound (327 mg, 0.5 mmol), ethyl 2-amidinoacetate
added to a 50 mL round bottom flask under Argon. The hydrochloride (1.25 g, 7.5 mmol) and potassium carbonate
reaction mixture was heated to 80 C for 14 h. After (1.04 g, 7.5 mmol) were dissolved in 8 mL of DMF. The reaction
completion, the reaction mixture was poured into distilled mixture was heated to 85 C for 12 h. After completion, the
7.
6
º
º
water (50 mL) and then extracted with ethyl acetate (4 x 50 reaction mixture was poured in 20 mL of distilled water and
mL). The organic phase was dried over Na2SO4 and solvent was liquid-liquid extraction with ethyl acetate (5 x 20 mL). The
removed under reduced pressure. The product (white solid) combined organic phase was dried over Na2SO4 and the
was isolated by flash chromatography using ethyl acetate : solvent was removed under reduced pressure. The product
petroleum ether (3:1) as eluent. The product exhibited 1,4- was purified by flash chromatography with ethyl acetate :
dihydro (52%) and 3,4-dihydro (48%) tautomeric forms in methanol (10:1 v/v) as eluent. Yield = 266 mg, 40%. ESI-HRMS:
CDCl3, and thus, some hydrogen atoms in the structure could Calc. for C66H75N9O21: 1329.51, Found [M+H+]: 1330.55. 1H
not be integrated as integer numbers in the 1H NMR spectrum. NMR (400 MHz, DMSO-d6) 8.68 (s, 3H), 8.37 (s, 2H), 7.95 (s,
Yield = 3.58 g, 90%. HRMS (MALDI): m/z calcd for C18H22N3O5 1H), 7.03 (d, 6H, J = 7.6 Hz), 6.98-6.82 (m, 9H), 6.76 (d, 3H, J =
1
[M+H+]: 360.1554; found: 362.1553. H NMR (400 MHz, CDCl3) 7.8 Hz), 4.65 (s, 6H), 4.28 (d, 6H, J = 13.1 Hz), 3.90 (d, 12H, J =
δ
8.5 Hz), 6.18 (s, 0.67H), 4.53 (s, 0.61H), 4.43 (d, 0.49H, J = 6.9 NMR(100MHz, DMSO-d6)
(ppm) 7.10 (dd, 2H, J = 28.7, 8.4 Hz), 6.77 (dd, 2H, J = 25.0, 6.9 Hz), 2.89 (s, 2H), 2.73 (s, 2H) 1.34-0.89 (m, 18H); 13C
δ (ppm) 168.77, 164.53, 156.12,
Hz), 4.29-3.98 (m, 4H), 3.77 (t, 3H, J = 6.9 Hz), 3.26 (d, 0.59H, J 151.80, 143.87, 134.19, 131.47, 128.58, 114.71, 113.88, 79.49,
= 1.4 Hz), 1.24 ppm (m, 6H); 13C NMR (100 MHz, DMSO-d6) δ 66.01, 58.32, 35.86, 14.93. mp = 74.4
(ppm) 169.5 162.8, 158.2, 136.4, 128.3, 114.0, 61.2, 57.8, 55.4,
51.0, 15.2, 14.5.
ºC.
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