Synthesis of 2-alkenyl-3-hydroxyquinolin-4(1H)-ones as promising antimicrobial and fluorescent agents

Article abstract of DOI:10.1016/j.tet.2017.12.010

2-Alkenyl-3-hydroxyquinolin-4(1H)-ones were prepared by the rearrangement of anthranilic acid esters synthesized by two alternative methods. The prepared derivatives were screened for their antimicrobial activities against representative Gram-positive and

Full text of DOI:10.1016/j.tet.2017.12.010

Tetrahedron xxx (2017) 1e9
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Synthesis of 2-alkenyl-3-hydroxyquinolin-4(1H)-ones as promising
antimicrobial and fluorescent agents
a
b
b
b
ꢀ
ꢀ b
Radim Horak , Lubomír Kvapil , Kamil Motyka , Ludmila Slaninova , Martin Grepl ,
b
b
b
a, *
ꢁ
ꢀꢁ
Kamil Koristek , Miroslav Urbasek , Pavel Hradil , Miroslav Soural
Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University Olomouc, Hnevotínska 5, 779 00, Olomouc, Czech
a
ꢁ
ꢀ
Republic
b
ꢁ
Department of Organic Chemistry, Faculty of Science, Palacky University Olomouc, tr. 17. listopadu 12, 771 46, Olomouc, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
2-Alkenyl-3-hydroxyquinolin-4(1H)-ones were prepared by the rearrangement of anthranilic acid esters
synthesized by two alternative methods. The prepared derivatives were screened for their antimicrobial
activities against representative Gram-positive and Gram-negative bacteria, displaying notable minimum
inhibitory concentration values against specific strains. The emission spectra of the target quinolines
exhibited two well-separated emission bands, and the maximum excitation wavelengths of the selected
compounds were detected at relatively high values.
Received 25 October 2017
Received in revised form
28 November 2017
Accepted 5 December 2017
Available online xxx
© 2017 Elsevier Ltd. All rights reserved.
Keywords:
Anthranilates
Quinolinones
Rearrangement
Antibacterial
Fluorescence
1. Introduction
inhibitors with a resulting effect on mitosis.8 These specific 3HQs
also inhibited inosine monophosphate dehydrogenase (IMPDH)9
Quinolin-4(1H)-ones are pharmacologically attractive com-
pounds with a wide range of biological effects. In this regard, qui-
nolin-4(1H)-one-3-carboxylic acids are particularly attractive due
to their highly potent antimicrobial activities.1 A report on the
synthesis and screening of oxolinic acid and pefloxacin analogues,
which bear 3-hydroxy groups instead of carboxylic groups, toward
different bacterial strains revealed only negligible activity.2 This
indicated the negative influence of such structural modification,
and therefore, 3-hydroxy-4(1H)-quinolines (3HQs) have not been
considered promising antimicrobial agents for a long period.
Nevertheless, the discovery of a simple synthetic route for the
routine preparation of 2-phenyl-3HQs2,3 as flavonol isosteres
initiated a detailed investigation of their biological properties. To
and reverse transcriptase of human immunodeficiency viruses.10
In contrast, significant antibacterial properties of 3HQs have not
been reported to date.
In addition to biological effects, 2-aryl-3HQs exhibit interesting
fluorescent properties and have been suggested as compounds for
the labeling of molecules.6,11e14 This presumption was supported by
the fact that 3HQs typically exhibit two well-separated emission
bands, resulting in dual fluorescence. Dual fluorescent labels are
not dependent on concentration because the ratio of the intensities
of the two bands can be applied as a signal. This is advantageous in
complex biological systems, such as cells or tissues, in which the
local concentration of the label cannot be controlled easily because
of its inhomogeneous distribution.15,16 On the other hand, the
excitation of previously reported 2-aryl-3HQs requires relatively
low-wavelength light (usually approximately 350 nm),12,13 which is
not beneficial due to the interfering fluorescence of intrinsic fluo-
rophores as well as harmful effects of UV radiation. For this reason,
excitation with higher-wavelength light is considerably more ad-
vantageous with respect to possible biological applications.
In this paper, we focus on the preparation of novel 3HQs bearing
an alkenyl or alkyl moiety in the 2 position. The introduction of an
date,
a number of different 2-phenyl-3HQs with significant
cytotoxic4e6 and immunosuppressive effects7 have been reported.
Regarding their biomolecular targets, 2-phenyl-3HQs have been
shown to act as topoisomerase and microtubule polymerization
* Corresponding author.
E-mail address: miroslav.soural@upol.cz (M. Soural).
https://doi.org/10.1016/j.tet.2017.12.010
0040-4020/© 2017 Elsevier Ltd. All rights reserved.
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R. Horak et al. / Tetrahedron xxx (2017) 1e9
2
alkene conjugated with an additional aromatic ring was suggested
to produce a bathochromic shift of the absorption, thus possibly
increasing the excitation wavelength energy. Furthermore, 2-alkyl-
3HQs represent biologically relevant compounds, with 2-heptyl-3-
hydroxyquinolin-4(1H)-one (PQS, Pseudomonas quinolone signal)
being the most important derivative. PQS acts as a signaling
molecule used by resistant bacteria Pseudomonas aeruginosa in the
virulence regulatory system,17e19 which is one of the possible tar-
gets for treating diseases caused by resistant bacteria.20e22
2. Results and discussion
2.1. Synthesis
The synthetic approach leading to target compounds 4 was
inspired by a previously reported method for 2-aryl-3HQs.2
Nevertheless, the limited availability and stability of unsaturated
intermediates
2 or 7 in comparison to analogous a-hal-
oacetophenones required substantial modification. In the first
stage, the synthesis of key intermediates 3aeo was performed.
These esters were prepared by the alkylation of anthranilic acid
with
a-haloketones. Two alternative methods were developed
depending on the resulting substitution pattern. Method
A
(Scheme 1) was applicable for aryl (R1 ¼ Ar) or dialkyl (R1,2 ¼ CH3)
intermediates. It was based on the condensation of commercially
available aldehydes with acetone23 and subsequent bromination of
the resulting a,b-unsaturated ketones 1aei with phenyl trimethyl-
ammonium tribromide (PTT).24 Haloketone 2j was prepared from
commercially available mesityl oxide 1j using a similar procedure.
In contrast, the bromination of monoalkyl or pyridyl unsaturated
ketones prepared from aldehydes 6k-o, 6s, and 6t (see the structure
of aldehydes in Scheme 2) by method A was unsuccessful.
For this reason, intermediates 7k-o were synthesized by Method
B based on a Wittig reaction of phosphorane 5 with pyridine 2-
carboxaldehyde 6k25 or aliphatic aldehydes 6leo (Scheme 2).
However, reaction conditions to react
(pivaloyl aldehyde, isobutyraldehyde
a
-branched aldehydes 6per
or cyclo-
hexanecarboxaldehyde) or pyridyl aldehydes 4s and 4t with 5 were
not found. In contrast to stable compounds 3aek, anthranilates 3l-
o were prone to spontaneous dimerization during their prepara-
tion. We managed to suppress this side-reaction by decreasing the
reaction temperature from 25 ꢀC to ꢁ5 ꢀC and changing the base
(K2CO3 was used instead of triethylamine). Despite this fact, esters
3leo were obtained in limited purity (~70%, LCMS) and used
Scheme 2. Synthesis of hydroxyquinolones 4keo by method B.
immediately in the next reaction step without purification and
characterization.
The use of anthranilate 8 as an alternative intermediate for the
preparation of anthranilates 3 was also tested (Scheme 2). Never-
theless, its reaction with various aliphatic, aromatic or hetero-
aromatic aldehydes under the Wittig reaction conditions was
unsuccessful. To prepare the target 3HQs, the original conditions2
(using PPA or solvent-free cyclization) were initially applied.
However, the cyclization of anthranilates 3aeo failed or led to the
formation of inseparable impurities. On the other hand, 3HQs 4a-k
were prepared in good yields by the cyclization of the corre-
sponding anthranilates using trifluoroacetic acid.6 This method was
also applicable for products 4l-o, however with limited yields
7e12% (calculated after 3 steps).
To test the applicability of the reaction sequence for the prep-
aration of 2-alkyl-3HQs, two representative compounds 4a and 4h
were reduced using catalytic hydrogenation (Scheme 3). In both
cases, the hydrogenation yielded the corresponding target com-
pounds 9a and 9h.
2.2. Antibacterial activity
The prepared 3HQs were screened for antibiotic activity against
Scheme 1. Synthesis of 3HQs 4aej by method A.
representative Gram-positive (B. subtilis, ATCC 6633; M. luteus,
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3
Table 2
Spectroscopic properties of the studied 3HQs in MeOH.
lem,1 (nm)b
lem,2 (nm)c
I1/I2
4 (%)e
a
d
Entry
Compound
lex
1
2
3
4
5
6
7
8
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
444
446
445
446
454
449
e
484
482
482
492
494
490
e
563
561
553
e
0.14
2.01
0.15
e
8.24
8.50
9.34
8.28
3.81
8.81
e
570
574
e
1.67
1.92
e
Scheme 3. Preparation of 2-alkyl-3HQs.
470
457
392
456
407
411
409
407
512
503
438
501
436
439
438
439
e
e
5.26
5.05
19.49
6.81
22.96
24.06
22.09
24.13
9
e
e
10
11
12
13
14
15
530
594
520
528
529
532
0.39
2.21
0.36
0.30
0.31
0.27
ATCC 10240; M. vaccae, DSM 43514; S. aureus, CCM 2524) and
Gram-negative (P. aeruginosa, CCM 3955; E. coli, CCM 3954) bac-
teria using agar diffusion assays.26 Derivatives 4a, 4i, 4k and 4m
displayed noticeable antibacterial activities against M. luteus when
tested at 2 mM, as indicated by the large inhibition zones (Table 1)
they induced. M. vaccae was susceptible to derivatives 4i and 4k,
and S. aureus was susceptible to 4i. Derivatives with inhibition
zones ꢂ20 mm were subjected to further assays27 to determine
their minimum inhibitory concentrations (MIC). Notable MIC
a
lex, Excitation wavelength.
lem,1, Fluorescence emission maximum at lower wavelengths.
lem,2, Fluorescence emission maximum at higher wavelengths.
I1/I2, ratio of fluorescence maximum intensities.
4, Fluorescence quantum yield (determined with quinine sulfate in 0.5 M sul-
b
c
d
e
values were observed for 4a, 4i and 4k (3.13, 12.5 and 25.0
against M. luteus, respectively). Additionally, compound 4i exhibi-
ted promising inhibition of S. Aureus (25.0
mol Lꢁ1). The most
m
mol Lꢁ1
furic acid (4 ¼ 0.57726), used as a reference fluorescence standard).
m
active derivatives possessed a similar structural motif e an
unsubstituted aromatic scaffold (phenyl, thiophene and pyridine)
bonded to the 3-hydroxyquinolin-4(1H)-one skeleton through an
ethenyl group.
2-Alkyl 3HQs 9 were also tested for their antibiotic activities.
The reduction of the double bond in 4a led to derivative 9a with
noticeable activity against S. Aureus. In contrast, the activity against
M. luteus was diminished by the hydrogenation of derivative 4a.
Compound 4h with an elongated alkyl chain was inactive against all
tested strains.
2.3. Fluorescence properties
To determine the detailed fluorescence properties of the studied
compounds, the excitation and emission spectra, as well as quan-
tum yields, were measured. The excitation spectra (Table 2, Fig. 1)
showed that the maximum excitation wavelengths were obtained
in the range from 346 to 470 nm and exhibited several relatively
Fig. 1. Normalized fluorescence excitation and emission spectra of compounds 4d and
4l.
Table 1
Antibacterial activities of hydroxyquinolones 4 and 9.
narrow distinct local maxima (Fig. 1). In contrast to 2-aryl-3HQs
that are excited by relatively low-wavelength light (usually
approximately 350 nm),11,12 it was evident that excitation was
possible in a wider excitation wavelength range. Moreover, some
derivatives could be excited by light with relatively high wave-
lengths of approximately 450 nm. The difference (Stokes shift)
between the longer excitation wavelength and the closer emission
maximum wavelength remained sufficient to measure the fluo-
rescence intensity at the lower wavelength maximum of the
emission spectrum. The emission spectra primarily exhibited two
well-separated emission bands with various ratios of fluorescence
maximum intensities I1/I2 (Table 2). For derivatives 4d, 4h and 4i,
the emission spectra lost the dual fluorescence character, and only
emission spectra with one maximum or only a hint of the second
maximum were observed (Fig. 1). The quantum yields were
detected in units of percent. Higher quantum yields (20%) were
observed for derivatives with branched (4j) or linear alkenyl chains
(4l, 4m, 4n, and 4o) in the position 2 (see Table 2). To investigate
the effect of the double bond in the alkenyl chain on the
Cmpd Diameter of inhibition zone in agar diffusion assay (mm)/(MIC)
(m )
mol Lꢁ1
B. subtilis M. luteus M. vaccae S. aureus P. aeruginosa E. coli
4a
4b
4c
4d
4e
4f
4g
4h
4i
14
14
0
12
0
0
0
0
22/(3.13)
0
17
0
0
0
0
0
0
0
0
0
0
0
0
0
0
15
16
0
0
0
0
0
0
15
0
0
0
0
0
0
0
15
12
18
17
13
0
13
13
21/(12.5) 21/(25.0) 22/(25.0) 14
18
4j
0
0
0
18
0
0
4k
4l
15
0
12
13
0
15
0
26/(25.0) 25/(50.0)
14
22/(200) 17
0
0
18
17
0
0
21/(>200)
17
20/(>200)
16
0
18
0
0
4m
4n
4o
9a
9h
Stda
20/(>200)
15
13
18
0
15
13
17
0
0
0
0
0
0
20/(100)
0
20/(7.5)
18/(0.26) 27/(0.26) 20/(15.0) 15/(3.75)
18-20/(7.5)
a
Ciprofloxacin used as a standard.
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4
fluorescence properties of 2-alkenyl-3HQs, the quantum yields of
alkyl derivatives 9a and 9h were also determined. The quantum
yields of 9a and 9h were 64.18 and 69.84%, respectively. It was
apparent that the introduction of the alkenyl double bond led to a
substantially decreased quantum yield.
yields of the previously described 3-hydroxyquinolin-4(1H)-one
derivatives. Despite this fact, the fluorescence intensities of the
studied compounds were still sufficient for their potential appli-
cation as fluorescence probes.
It has been previously reported that the fluorescence activities
of 3-hydroxyquinolin-4(1H)-ones are highly dependent on the
pH.11e14 For this reason, the effect of pH on the fluorescence
properties of derivatives 4 in phosphate buffer was also investi-
gated. Derivatives 4l, 4m and 4n were chosen because of their high
fluorescence quantum yields. In the pH range from 2 to 8, the
fluorescence intensity was almost constant or increased slightly
(Fig. 2). However, in alkaline solution (pH 8e11), the fluorescence
intensity increased dramatically and then reached a plateau at pH
11e12. From the relationship between pH and fluorescence in-
tensity, it can be concluded that the studied compounds possessed
two forms in aqueous solution. A neutral form (that exhibited a
lower fluorescence intensity) of 2-alkenyl-3-hydroxyquinolin-
4(1H)-ones is expected under acidic and neutral conditions, and a
deprotonated anionic form is formed in strong alkaline solution.
The shape of the curve indicated that this transition occurred at pKa
values in the range from 9 to 10. The independence of fluorescence
intensity on pH in neutral conditions is an advantage for the
possible application of these compounds in biological systems.
4. Experimental
4.1. General
1,2-Dichloroethane for Wittig reactions was distilled from P2O5
and stored over molecular sieves. Other solvents were used in
common grade. Mesityl oxide 1j, benzylidene acetone 1a, alde-
hydes 6 and anthranilic acid were used commercially. Substituted
benzylidene acetones 1bei were prepared from commercially
available aromatic aldehydes and acetone according to the litera-
ture.23 Ylide 5 was prepared from commercially available 1,3-
dichloroacetone and triphenylphosphine according to the litera-
ture.25 Phenyl trimethylammonium tribromide was prepared ac-
cording to the literature24 from dimethyl aniline, dimethyl sulfate,
bromine, and hydrobromic acid.
4.2. Analytical methods
High resolution mass spectrometry (HRMS) analyses were
measured with a Thermo Exactive instrument (Thermo Scientific,
USA). The injection was performed by an apparatus Accela 1250
autosampler. The chromatographic separation parameters include
3. Conclusion
To conclude, we have developed a simple synthetic strategy for
the preparation of 2-alkenyl- and 2-alkyl-3-hydroxyquinolin-
4(1H)-ones using readily available starting materials. In contrast to
2-phenyl-3HQs that have been extensively studied, the 2-alkenyl
derivatives exhibited noticeable antibacterial activities, indicating
that 3HQs with specific substitution patterns are promising anti-
bacterial agents. Although a detailed structure-activity relationship
was not observed, two compounds exhibited high or medium MICs
against Micrococcus luteus and Staphylococcus aureus, and they can
be used as structural templates to further improve the inhibition
values. In contrast to previously reported 2-aryl-3HQs, the bath-
ochromic shifts of 2-alkenyl-3HQs resulted in their excitation by
light with higher wavelengths. On the other hand, the quantum
yields of 2-alkenyl-3HQs were lower in comparison to the quantum
column Luna C18, 3
mobile phase acetonitrile/water 70/30 with 0.1% formic acid, flow
rate of 200
L/min, and column temperature of 30 ꢀC. Sample
preparation was obtained using the following procedure: 1 mg of
sample was dissolved in 10 mL of a mixture of acetonitrile/water
m
m, 50 ꢃ 2mm i.d. column (Phenomenex, USA),
m
(7:3) with 0.1% of formic acid (1 min sonication) and then 50
this solution and 950 L of the same solution were added into vial
and mixed before injection of 5 l. High-resolution mass spec-
mL of
m
m
trometer Exactive based on orbitrap mass analyser was equipped
with heated electrospray ionization (HESI). The spectrometer was
tuned to obtain the maximum response for 75e700 m/z. The source
parameters were set to the following values: HESI temperature
50 ꢀC, spray voltage þ3.0 kV (positive mode), transfer capillary
temperature 300 ꢀC, and sheath gas/aux gas (nitrogen) flow rates
35/10.1H NMR, 13C NMR and 31P spectra were recorded at 23 ꢀC with
a Varian spectrometer (399.90 MHz for 1H, 100.56 MHz for 13C,
161.92 for 31P) in DMSO. The 1H and 13C chemical shifts were
referenced to the central signal of the solvent DMSO (
d
¼ 2.50 1H
and
d
¼ 39.43 13C). The assignment of resonances in the 1H and 13
C
NMR spectra was made by two-dimensional homonuclear and
heteronuclear shift correlation experiments. Melting points were
measured on a Kofler hot-stage microscope VEB Analytik Dresden
PHMK 76/1586 and were not corrected. IR spectra
(4000 ꢁ 400 cmꢁ1) were collected using Nicolet Avatar 370 FTIR
spectrometer.
4.3. Procedure for the preparation of anthranilates 3aej
Benzylidenacetone 1aej (0.05 mol) was dissolved in tetrahy-
drofuran (30 mL). Phenyl trimethyl ammonium tribromide
(0.05 mol, 11.3 g) was charged into the solution at 25 ꢀC. After
starting materials were consumed (45 min), the reaction mixture
was poured into ice-cold water (300 mL). The product was
extracted with diethylether (3 ꢃ 50 mL), and the combined organic
layers were washed with water, brine and dried over Na2SO4 and
evaporated under reduced pressure at room temperature. The
residue was dissolved in DMF (5 mL) and added drop wise over
5 min to a solution of anthranilic acid (0.05 mol; 6.9 g) and
Fig. 2. Dependence of the fluorescence intensity on pH for 4l, 4m and 4n (for exci-
tation and emission wavelengths, see Table 2; measured for the emission maxima at
higher wavelengths).
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5
triethylamine (0.05 mol; 7 mL) in DMF (50 mL). After starting
4.8. (E)-4-(3-Chlorophenyl)-2-oxobut-3-en-1-yl 2-amino-benzoate
(3e)
materials were consumed (TLC monitoring), the reaction mixture
was poured into water with crushed ice (500 mL), the resulting
suspension was filtered and the cake was thoroughly washed with
water and dried. Crude anthranilate was purified by the crystalli-
zation process.
Reaction time 18 h. Yield 3.6 g (23%), yellow solid, mp
117e120 ꢀC (toluene). nmax (neat) 3456, 3357, 2938, 1694, 1607,
15866, 1560, 1375, 1290, 1242 cmꢁ1 1H NMR (399.9 MHz, DMSO-
;
d6)
d
: 5.27 (2H, s), 6.56 (1H, ddd, J ¼ 8.1, 7.0, 1.1 Hz), 6.65 (2H, s), 6.80
(1H, dd, J ¼ 8.4, 0.8 Hz), 7.13 (1H, d, J ¼ 16.4 Hz), 7.29 (1H, ddd,
J ¼ 8.6, 7.0, 1.7 Hz), 7.46e7.53 (2H, m), 7.72 (2H, m), 7.80 (1H, dd,
J ¼ 8.1, 1.6 Hz), 7.87 (1H, t, J ¼ 1.7 Hz) ppm. 13C NMR (100.56 MHz,
4.4. (E)-2-Oxo-4-phenylbut-3-en-1-yl 2-aminobenzoate (3a)
Reaction time 1 h. Yield 3.4 g (24%), beige solid, mp 128e130 ꢀC
(EtOH). nmax (neat) 3482, 3361 3056, 2942, 1703, 1683, 1613, 1583,
DMSO-d6) d: 67.3, 108.1, 114.7, 116.5, 124.0, 127.1, 128.0, 130.3, 130.7,
133.7, 134.3, 136.4, 141.3, 151.5, 166.5, 193.0. HRMS (HESI) calcd for
1559, 1296, 1246, 1069 cmꢁ1
;
1H NMR (399.9 MHz, DMSO-d6)
d:
(C17H15ClNOþ3 ) [MþH]þ 316.07350, found 316.07345.
5.28 (2H, s), 6.58 (1H, ddd, J ¼ 8.1, 7.0, 1.1 Hz), 6.65 (2H, brs), 6.80
(1H, dd, J ¼ 8.4, 1.0 Hz), 7.03 (1H, d, J ¼ 16.5 Hz), 7.29 (1H, ddd,
J ¼ 8.6, 7.0, 1.7 Hz), 7.44e7.48 (3H, m), 7.74e7.77 (3H, m), 7.81 (1H,
4.9. (E)-4-(4-Chlorophenyl)-2-oxobut-3-en-1-yl 2-amino-benzoate
(3f)
dd, J ¼ 8.1, 1.6 Hz) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 67.2,
108.1, 114.7, 116.5, 122.6, 128.5,129.0,130.7, 130.8,134.1,134.3,143.0,
151.5,166.6,193.1 ppm. HRMS (HESI) calcd for (C17H16NOþ3 ) [MþH]þ
282.11247, found 282.11266.
Reaction time 5 h. Yield 4.1 g (26%), beige solid, mp 171e174 ꢀC
(toluene). nmax (neat) 3480, 3359, 2944, 1702, 1683, 1612, 1584,
1560, 1485, 1382, 1292, 1244, 1067 cmꢁ1 1H NMR (399.9 MHz,
;
DMSO-d6)
d
: 5.25 (2H, s), 6.56 (1H, ddd, J ¼ 8.1, 7.0, 1.1 Hz), 6.65 (2H,
s), 6.80 (1H, dd, J ¼ 8.4, 0.9 Hz), 7.05 (1H, d, J ¼ 16.4 Hz), 7.29 (1H,
ddd, J ¼ 8.5, 7.0, 1.7 Hz), 7.52 (1H, d, J ¼ 8.5 Hz), 7.74 (2H, d,
4.5. (E)-4-(4-Methoxyphenyl)-2-oxobut-3-en-1-yl 2-amino-
benzoate (3b)
J ¼ 16.4 Hz), 7.77e7.81 (3H, m). 13C NMR (100.56 MHz, DMSO-d6)
d:
67.3, 108.1, 114.7, 116.5, 123.3, 129.0, 130.2, 130.7, 133.1, 134.3, 135.3,
141.6, 151.5, 166.5, 193.0 ppm. HRMS (HESI) calcd for (C17H15ClNOþ3 )
[MþH]þ 316.07350, found 316.07365.
Reaction time 18 h. Yield 3.6 g (23%), beige solid, mp 125e127 ꢀC
(EtOH). nmax (neat) 3471, 3367, 2962, 1701, 1683, 1613, 1586, cmꢁ1
;
1H NMR (399.9 MHz, DMSO-d6)
d: 3.81 (3H, s), 5.24 (2H, s), 6.57
(1H, ddd, J ¼ 8.1, 7.0, 1.2 Hz), 6.65 (1H, s), 6.80 (2H, dd, J ¼ 8.4,
0.9 Hz), 6.89 (1H, d, J ¼ 16.4 Hz), 7.02 (2H, d, J ¼ 8.8 Hz), 7.28 (1H,
ddd, J ¼ 8.6, 7.0, 1.7 Hz), 7.69e7.73 (3H, m), 7.80 (1H, dd, J ¼ 8.1,
4.10. (E)-4-(4-Nitrophenyl)-2-oxobut-3-en-1-yl 2-aminobenzoate
(3g)
1.6 Hz) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 55.3, 67.1, 108.2,
Reaction time 1 h. Yield 5.2 g (23%), orange solid, mp 176e179 ꢀC
(2-methoxyethanol). nmax (neat) 3483, 3373, 2914, 1688, 1616, 1592,
114.5, 114.7, 116.5, 120.1, 126.6, 130.4, 130.7, 134.2, 143.0, 151.4, 161.4,
166.6, 192.8 ppm. HRMS (HESI) calcd for (C18H18NO4)þ) [MþH]þ
312.12303, found 312.12299.
1567, 1343, 1234,1104 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 5.31
(2H, s), 6.57 (1H, ddd, J ¼ 8.1, 7.0, 1.1 Hz), 6.65 (2H, s), 6.80 (1H, dd,
J ¼ 8.4, 0.8 Hz), 7.22 (1H, d, J ¼ 16.5 Hz), 7.29 (1H, ddd, J ¼ 8.5, 7.0,
1.7 Hz), 7.80 (1H, dd, J ¼ 8.1, 1.6 Hz), 7.85 (1H, d, J ¼ 16.5 Hz), 8.03
(2H, d, J ¼ 8.8 Hz), 8.29 (2H, d, J ¼ 8.9 Hz) ppm. 13C NMR
4.6. (E)-2-Oxo-4-(p-tolyl)but-3-en-1-yl 2-aminobenzoate (3c)
(100.56 MHz, DMSO-d6) d: 67.4, 108.0, 114.7, 116.5, 124.0, 126.3,
Reaction time 18 h. Yield 4 g (27%), beige solid, mp 137e141 ꢀC
(toluene). nmax (neat) 3480, 3359, 3023, 2942, 1701, 1684, 1614,
129.5,130.7,134.3,140.2,140.6,148.2,151.5,166.5,193.2 ppm. HRMS
(HESI) calcd for (C17H15N2O5þ) [MþH]þ 327.09729, found 327.09755.
1584, 1560, 1245 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 2.34 (3H,
s), 5.26 (2H, s), 6.56 (1H, ddd, J ¼ 8.1, 7.0, 1.1 Hz), 6.65 (2H, s), 6.80
(1H, dd, J ¼ 8.4, 0.8 Hz), 6.97 (1H, d, J ¼ 16.4 Hz), 7.26e7.31 (3H, m),
7.64 (2H, d, J ¼ 8.2 Hz), 7.71 (1H, d, J ¼ 16.4 Hz), 7.80 (1H, dd, J ¼ 8.1,
4.11. (3E,5E)-2-Oxo-6-phenylhexa-3,5-dien-1-yl 2-amino-benzoate
(3h)
1.6 Hz) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 21.0, 67.2, 108.1,
Reaction time 5 h. Yield 5.2 g (34%), yellow solid, mp 137e139 ꢀC
(toluene/EtOH). nmax (neat) 3458, 3352, 2947, 1698, 1680, 1611,
1600, 1588, 1567, 1461, 1324, 1268, 1072 cmꢁ1; 1H NMR (399.9 MHz,
114.7, 116.5, 121.6, 128.5, 128.5, 129.6, 130.7, 131.3, 134.3, 140.9, 143.1,
151.5, 166.6, 193.0 ppm. HRMS (HESI) calcd for (C18H18NOþ3 )
[MþH]þ 296.12812, found 296.12777.
DMSO-d6)
d
: 5.19 (2H, s), 6.46 (1H, d, J ¼ 15.6 Hz), 6.57 (1H, ddd,
J ¼ 8.1, 7.0, 1.2 Hz), 6.66 (2H, s), 6.80 (1H, dd, J ¼ 8.4, 0.8 Hz),
7.13e7.22 (2H, m), 7.29 (1H, ddd, J ¼ 8.5, 7.0, 1.7 Hz), 7.33e7.43 (3H,
m), 7.52 (1H, ddd, J ¼ 15.6, 7.6, 2.6 Hz), 7.55e7.62 (2H, m), 7.80 (1H,
4.7. (E)-4-(2-Chlorophenyl)-2-oxobut-3-en-1-yl 2-amino-benzoate
(3d)
dd, J ¼ 8.1, 1.6 Hz) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 67.1,
108.1, 114.7, 116.5, 125.5,126.9,127.3, 128.8,129.3,130.7, 134.3,135.7,
142.0, 143.7, 151.5, 166.6, 193,0 ppm. HRMS (HESI) calcd for
(C19H18NOþ3 ) [MþH]þ 308.12812, found 308.12828.
Reaction time 18 h. Yield 3.6 g (23%), yellow solid, mp
125e127 ꢀC (toluene). nmax (neat) 3483, 3370, 3063, 2917, 1708,
1689, 1608, 1593, 1296, 1246 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d
: 5.27 (2H, s), 6.56 (1H, ddd, J ¼ 8.1, 7.0, 1.1 Hz), 6.66 (2H, s), 6.80
4.12. (E)-2-Oxo-4-(thiophen-2-yl)but-3-en-1-yl 2-amino-benzoate
(3i)
(1H, dd, J ¼ 8.4, 0.9 Hz), 7.15 (1H, d, J ¼ 16.2 Hz), 7.29 (1H, ddd,
J ¼ 8.5, 7.0, 1.6 Hz), 7.43 (1H, dt, J ¼ 7.5, 1.4 Hz), 7.48 (1H, dt, J ¼ 7.8,
1.9 Hz), 7.57 (1H, dd, J ¼ 7.9, 1.4 Hz), 7.81 (1H, dd, J ¼ 8.1, 1.6 Hz), 7.93
(1H, d, J ¼ 16.2 Hz), 7.94e7.96 (1H, m) ppm. 13C NMR (100.56 MHz,
Reaction time 4 h. Yield 5.7 g (40%), beige solid, mp 127e130 ꢀC
(EtOH). nmax (neat) 3484, 3365, 2944, 1698, 1681, 1600, 1581, 1558,
DMSO-d6)
d: 67.7, 108.0, 114.7, 116.5, 124.9, 127.8, 128.2, 130.1, 130.7,
1412, 1243, 1160 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 5.22 (2H,
131.7, 132.1, 134.2, 134.3, 137.2, 151.5, 166.5, 193.0 ppm. HRMS (HESI)
s), 6.56 (1H, ddd, J ¼ 8.1, 7.0, 1.1 Hz), 6.65 (2H, s), 6.70 (1H, d,
calcd for (C17H15ClNOþ3 ) [MþH]þ 316.07350, found 316.07354.
J ¼ 16.0 Hz), 6.79 (1H, dd, J ¼ 8.4, 0.8 Hz), 7.19 (1H, dd, J ¼ 5.1,
ꢀ
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ꢀ
R. Horak et al. / Tetrahedron xxx (2017) 1e9
6
3.6 Hz), 7.28 (1H, ddd, J ¼ 8.5, 7.0, 1.7 Hz), 7.61 (1H, ddd, J ¼ 3.7, 0.6,
0.5 Hz), 7.78e7.80 (2H, m), 7.91 (1H, d, J ¼ 16.0 Hz) ppm. 13C NMR
DMSO-d6)
d
: 3.80 (1H, d, J ¼ 23.7 Hz), 4.65 (2H, s), 6.52 (1H, dt,
J ¼ 7.6, 1.1 Hz), 6.66 (2H, s), 6.76 (1H, dd, J ¼ 8.3, 0.9 Hz), 7.24 (1H, dt,
(100.56 MHz, DMSO-d6) d: 67.2, 108.1, 114.7, 116.5, 120.7, 128.7,
J ¼ 7.8, 1.8 Hz), 7.54e7.68 (15H, m), 7.77 (1H, dd, J ¼ 8.1, 1.8 Hz) ppm.
130.6, 130.7, 133.1, 134.3, 135.8, 139.1, 151.5, 166.5, 192.5 ppm. HRMS
(HESI) calcd for (C15H14NO3Sþ) [MþH]þ 288.06889, found
288.06920.
13C NMR (100.56 MHz, DMSO-d6)
d: 46.8 (d, J ¼ 110.2 Hz), 66.6 (d,
J ¼ 16.9 Hz), 109.0, 114.7, 116.4, 126.2 (d, J ¼ 90.7 Hz), 129.0 (d,
J ¼ 11.9 Hz), 130.6, 132.0, 132.6 (d, J ¼ 10.2 Hz), 133.9 (d, J ¼ 10.2 Hz),
151.2, 166.9, 185.0 ppm. 31P NMR (161.92 MHz, DMSO-d6)
d:
4.13. 4-Methyl-2-oxopent-3-en-1-yl 2-aminobenzoate (3j)
15.13 ppm. HRMS (HESI) calcd for (C28H25NO3Pþ) [MþH]þ
454.15666, found 454.15633.
Reaction time 3 h. Yield 1.2 g (10%), beige solid, mp 56e59 ꢀC
(Et2O/cyclohexane). nmax (neat) 3458, 3347, 2924, 1689, 1615, 1584,
4.17. Procedure for the preparation of quinolones 4aek
1565, 1239, 1102 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 1.91 (3H,
d, J ¼ 1.1 Hz), 2.11 (3H, d, J ¼ 1.0 Hz), 4.92 (2H, s), 6.21e6.22 (1H, m),
6.55 (1H, ddd, J ¼ 8.1, 7.0, 1.2 Hz), 6.63 (2H, s), 6.78 (1H, dd, J ¼ 8.4,
0.8 Hz), 7.27 (1H, ddd, J ¼ 8.5, 7.0,1.7 Hz), 7.77 (1H, dd, J ¼ 8.1,1.6 Hz)
Anthranilates 3aek (0.01 mol) was refluxed in trifluoroacetic
acid (25 mL) until initial anthranilates were consumed (TLC
monitoring). The reaction mixture was concentrated, and thick
residue was poured into ice-cold water (50 mL). The suspension
was filtered; filtration cake was thoroughly washed with water and
purified by crystallization.
ppm. 13C NMR (100.56 MHz, DMSO-d6) d: 20.6, 27.3, 68.6, 108.2,
114.7, 116.5, 119.2, 130.7, 134.2, 151.4, 157.4, 166.5, 193.0 ppm. HRMS
(HESI) calcd for (C13H16NOþ3 ) [MþH]þ 234.11247, found 216.10191.
4.14. Procedure for the preparation of chloroketone 7k
4.18. (E)-3-Hydroxy-2-styrylquinolin-4(1H)-one (4a)
Chloroketone 7k was prepared according to the literature:25
Ylide 5 and pyridine-2-carbaldehyde (15.1 mmol, 1.44 mL) were
stirred at room temperature in CH2Cl2 (30 mL). The reaction
mixture was concentrated, and the residue was dissolved in hot
EtOAc. Solution was filtered and cooled down to 0 ꢀC. The resulting
white crystalline solid was filtered off and the filtrate was
concentrated. The obtained residue was purified by column chro-
matography (petroleum ether: EtOAc 4:1). Yield 1.64 g, 60%, pale
yellow solid, mp 46e48 ꢀC (ref.25 gave 48e49 ꢀC).
Reaction time 14 h. Yield 2.2 g (83%), yellow solid, mp
281e284 ꢀC (DMF). nmax (neat) 3061, 2935, 1636, 1625, 1582, 1542,
1467, 1400,1370, 1221 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 7.23
(dt, 1H, J ¼ 7.5, 0.8 Hz), 7.36 (1H, tt, J ¼ 7.3, 1.9 Hz), 7.42e7.47 (m,
3H), 7.59 (1H, ddd, J ¼ 8.4, 6.9, 1.5 Hz), 7.64e7.68 (3H, m), 7.71 (1H,
d, J ¼ 8.4 Hz), 8.12 (1H, dd, J ¼ 8.2, 1.3). 8.85 (1H, brs), 11.30 (1H, s)
ppm. 13C NMR (100.56 MHz, DMSO-d6)
124.4, 126.8, 128.7, 128.8, 129.0, 130.8, 133.0, 136.1, 137.9, 138.9,
169.7. HRMS (HESI) calcd for (C17H14NOþ2 ) [MþH]þ 264.10245,
found 264.10202.
d
: 117.9 (2ꢃ), 121.5, 121.8,
4.15. Procedure for the preparation of (E)-2-oxo-4-(pyridin-2-yl)
but-3-en-1-yl 2-aminobenzoate (3k)
4.19. (E)-3-Hydroxy-2-(4-methoxystyryl)quinolin-4(1H)-one (4b)
Chloroketone 7k (1.35 g, 7.25 mmol) was dissolved in DMF
(5 mL) and added drop wise over 5 min to the solution of anthra-
nilic acid (7.25 mmol; 1.00 g) and triethylamine (7.25 mmol; 1 mL)
in DMF (10 mL) at room temperature. The resulting mixture was
stirred at room temperature for 24 h. The reaction mixture was
poured into water with crushed ice (150 mL), the resulting sus-
pension was filtered, and the cake was thoroughly washed with
water and dried. Crude anthranilate was purified by crystallization
with MeOH. Yield 1.23 g (60%), beige solid, mp 110 ꢀC. nmax (neat)
3472, 3361, 2934, 1689, 1669, 1614, 1580, 1562, 1372, 1214,
Reaction time 28 h. Yield 1.6 g (53%), solid, mp 285e289 ꢀC (2-
methoxyethanol). nmax (neat) 3306, 2776, 1648, 1626, 1587, 1544,
1509, 1484, 1469, 1368, 1297, 1245 cmꢁ1 1H NMR (399.9 MHz,
;
DMSO-d6)
d
: 3.8 (3H, s), 7.01 (2H, d, J ¼ 8.8 Hz), 7.20e7.24 (1H, m),
7.27 (1H, d, J ¼ 16.8 Hz), 7.56e7.62 (4H, m), 7.70 (1H, d, J ¼ 8.4 Hz),
8.10 (1H, dd, J ¼ 8.2, 1.3 Hz), 8.74 (1H, brs), 11.23 (1H, s) ppm. 13
C
NMR (100.56 MHz, DMSO-d6) d: 55.2, 114.5, 115.5, 117.8, 121.4, 121.8,
124.3, 128.3,128.7, 129.3, 130.6,132.8,137.8, 138.5,159.8,169.5 ppm.
HRMS (HESI) calcd for (C18H16NOþ3 ) [MþH]þ 294.11247, found
294.11263.
1106 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 5.31 (2H, s), 6.57 (1H,
ddd, J ¼ 7.7, 7.4, 1.0 Hz), 6.66 (2H, s), 6.80 (1H, dd, J ¼ 8.4, 0.6 Hz),
7.27e7.31 (1H, m), 7.30 (1H, d, J ¼ 16.0 Hz), 7.44 (1H, ddd, J ¼ 7.6,
4.8, 1.0 Hz), 7.72e7.81 (3H, m), 7.90 (1H, dt, J ¼ 7.7, 1.8 Hz), 8.68 (1H,
4.20. (E)-3-Hydroxy-2-(4-methylstyryl)quinolin-4(1H)-one (4c)
Reaction time 8 h. Yield 1.6 g (58%), yellow solid, mp 287e291 ꢀC
(DMF/EtOH). nmax (neat) 3373, 2840, 1646, 1625, 1593, 1542, 1511,
dd, J ¼ 4.7, 1.0 Hz) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 67.5,
108.0, 114.7, 116.5, 125.0, 125.3 (2ꢃ), 130.7, 134.3, 137.3, 141.9, 150.1,
151.5, 152.1, 166.5, 193.5 ppm. HRMS (HESI) calcd for (C16H15N2Oþ3 )
[MþH]þ 283.10772, found 283.10788.
1447, 1327, 1237, 1209 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 2.33
(3H, s), 7.21e7.25 (1H, m), 7.25e7.27 (2H, m), 7.37 (1H, d,
J ¼ 16.8 Hz), 7.54 (2H, d, J ¼ 8.1 Hz), 7.56e7.61 (1H, m), 7.62 (1H, d,
J ¼ 16.8 Hz), 7.70 (1H, d, J ¼ 8.3 Hz), 8.08 (1H, brs), 8.11 (1H, dd,
J ¼ 8.2, 1.4 Hz), 11.26 (1H, s) ppm. 13C NMR (100.56 MHz, DMSO-d6)
4.16. Procedure for the preparation of 2-oxo-3-(triphenyl-l5-
phosphanylidene)propyl 2-amino-benzoate (8)
d: 20.8, 116.9, 117.9, 121.4, 121.8, 124.3, 126.8, 126.8, 129.0, 129.6,
130.7, 133.0, 133.4, 137.8, 138.4, 138.7, 169.6 ppm. HRMS (HESI) calcd
Ylide 5 (0.172 mol, 60.6 g) was added into a solution of an-
thranilic acid (0.183 mol, 25.1 g) and triethylamine (0.183 mol,
25.2 mL) in DMF (400 mL). After stirring for 3.5 h at 95e100 ꢀC, the
reaction mixture was slowly poured into the water (2 L). After
30 min of stirring, the suspension was filtered and washed with
water and then thoroughly washed with EtOH (3ꢃ100 mL). Crys-
tallization from DMF gave pure anthranilate 8. Yield 42 g (54%),
beige solid, mp 224 ꢀC. nmax (neat) 3465, 3333, 2930, 1695, 1613,
for (C18H16NOþ2 ) [MþH]þ 278.11756, found 278.11803.
4.21. (E)-2-(2-Chlorostyryl)-3-hydroxyquinolin-4(1H)-one (4d)
Reaction time 8 h. Yield 1.9 g (64%), yellow solid, mp 283e288 ꢀC
(2-Methoxyethanol). nmax (neat) 3297, 2770, 1646, 1621, 1583, 1562,
1541, 1472, 1482 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 7.24 (1H,
ddd, J ¼ 8.0, 6.8, 1.0 Hz), 7.37e7.46 (2H, m), 7.43 (1H, d, J ¼ 16.6 Hz),
1569, 1540, 1462, 1319, 1232, 1102 cmꢁ1 1H NMR (399.9 MHz,
;
7.55 (1H, dd, J ¼ 7.8, 1.5 Hz), 7.60 (1H, ddd, J ¼ 8.5, 6.8, 1.5 Hz), 7.72
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7
(1H, d, J ¼ 8.4 Hz), 7.88 (1H, dd, J ¼ 7.7, 1.8 Hz), 7.97 (1H, d,
J ¼ 16.6 Hz), 8.12 (1H, dd, J ¼ 8.2, 1.4 Hz), 9.00 (1H, brs), 11.41 (1H, s)
J ¼ 7.7, 7.3 Hz), 7.36 (1H, d, J ¼ 3.3 Hz), 7.58 (1H, ddd, J ¼ 7.6, 6.9,
1.4 Hz), 7.62e7.67 (2H, m), 7.87 (1H, d, J ¼ 16.4 Hz), 8.10 (1H, dd,
J ¼ 8.2, 1.4 Hz), 8.88 (1H, brs), 11.27 (1H, s) ppm. 13C NMR
ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 118.0, 121.4, 121.6, 121.8,
124.4,127.1,127.8,128.2,128.8,129.9,130.1,130.9,132.6,134.3,137.9,
139.4, 169.9 ppm. HRMS (HESI) calcd for (C17H13ClNOþ2 ) [MþH]þ
298.06293, found 298.06277.
(100.56 MHz, DMSO-d6) d: 117.0,117.8, 121.5, 121.7, 124.4, 126.7,
127.1, 128.4 (2ꢃ), 128.5, 130.8, 137.8, 138.8, 141.5, 169.5 ppm. HRMS
(HESI) calcd for (C15H12NO2Sþ) [MþH]þ 270.05833, found
270.05817.
4.22. (E)-2-(3-Chlorostyryl)-3-hydroxyquinolin-4(1H)-one (4e)
4.27. 3-Hydroxy-2-(2-methylprop-1-en-1-yl)quinolin-4(1H)-one
(4j)
Reaction time 8 h. Yield 2.1 g (71%), yellow solid, mp 290e294 ꢀC
(2-Methoxyethanol). nmax (neat) 3350, 2897, 1646, 1626, 1549, 1509,
1482, 1466, 1421, 1263, 1238, 1205 cmꢁ1 1H NMR (399.9 MHz,
;
Reaction time 17 h. Yield 0.9 g (41%), almost white solid, mp
211e215 ꢀC (MeOH/Et2O). nmax (neat) 3281, 2913, 1634, 1583, 1547,
1486, 1459, 1442, 1418, 1366, 1244, 1099 cmꢁ1; 1H NMR (399.9 MHz,
DMSO-d6)
d
: 7.23 (1H, dd, J ¼ 7.6, 7.4 Hz), 7.40e7.50 (3H, m),
7.57e7.63 (3H, m), 7.66e7.72 (2H, m), 8.11 (1H, dd, J ¼ 8.2, 1.4 Hz),
8.96 (1H, brs), 11.28 (1H, s) ppm. 13C NMR (100.56 MHz, DMSO-d6)
DMSO-d6)
d
: 1.76 (3H, d, J ¼ 0.9 Hz), 1.95 (3H, d, J ¼ 1.2 Hz),
d
: 117.9, 119.8, 121.6, 121.8, 124.4, 125.6, 126.2, 128.3 (2ꢃ), 130.8,
6.19e6.21 (1H, m), 7.21 (1H, ddd, J ¼ 6.4, 6.0, 1.5 Hz), 7.49e7.58 (2H,
m), 8.10 (1H, dd, J ¼ 7.9, 1.1 Hz), 8.13 (1H, brs), 11.26 (1H, brs) ppm.
130.9, 131.5, 133.8, 137.9, 138.4, 139.2, 169.8. HRMS (HESI) calcd for
(C17H13ClNOþ2 ) [MþH]þ 298.06293, found 298.06298.
13C NMR (100.56 MHz, DMSO-d6)
d: 20.4, 25.7, 115.9, 117.9, 121.4,
121.8, 124.3, 130.1, 130.2, 137.4, 137.8, 142.1, 169.3 ppm. HRMS (HESI)
4.23. (E)-2-(4-Chlorostyryl)-3-hydroxyquinolin-4(1H)-one (4f)
calcd for (C13H14NOþ2 ) [MþH]þ 216.10191, found 216.10191.
Reaction time 8 h. Yield 2.4 g (80%), yellow solid, mp 315e319 ꢀC
(2-Methoxyethanol). nmax (neat) 3276, 2784, 1651, 1625, 1585, 1567,
1452, 1477, 1435, 1319, 1205, 1089, 1008 cmꢁ1; 1H NMR (399.9 MHz,
4.28. (E)-3-Hydroxy-2-(2-(pyridin-2-yl)vinyl)quinolin-4(1H)-one
(4k)
DMSO-d6)
d
: 7.23 (1H, ddd, J ¼ 7.8, 7.2, 0.8 Hz), 7.43 (1H, d,
Reaction time 7 h. Yield 1.74 g (66%), orange solid, mp
290e295 ꢀC (2-Methoxyethanol). nmax (neat) 3061, 2936, 1640,
1624, 1588, 1545, 1493, 1480, 1470, 1443, 1426, 1405, 1375, 1244,
J ¼ 16.7 Hz), 7.49 (2H, d, J ¼ 8.5 Hz), 7.57e7.70 (5H, m), 8.11 (1H, dd,
J ¼ 8.2, 1.3 Hz), 8.90 (1H, brs), 11.28 (1H, s) ppm. 13C NMR
(100.56 MHz, DMSO-d6) d: 117.9, 118.8, 121.5, 121.8, 124.4, 128.5
1202 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 7.24 (1H, ddd, J ¼ 8.0,
(2ꢃ),129.0,130.8,131.6,133.0,135.1,137.9,139.1,169.8. HRMS (HESI)
calcd for (C17H13ClNOþ2 ) [MþH]þ 298.06293, found 298.06303.
6.8, 1.0 Hz), 7.34 (1H, ddd, 7.6, 4.8, 1.0 Hz), 7.57e7.62 (2H, m),
7.70e7.75 (2H, m), 7.85 (1H, dt, J ¼ 7.7, 1.8 Hz), 7.97 (1H, d,
J ¼ 16.3 Hz), 8.11 (1H, dd, J ¼ 8.2, 1.3 Hz), 8.65 (1H, ddd, J ¼ 4.7, 0.9,
4.24. (E)-3-Hydroxy-2-(4-nitrostyryl)quinolin-4(1H)-one (4g)
0.6 Hz),11.38 (1H, s) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 117.9,
121.6, 121.7, 121.8, 123.2,123.2,124.4,128.1, 130.9,132.3,137.2, 138.0,
139.7, 149.8, 153.9, 169.9 ppm. HRMS (HESI) calcd for (C16H13N2Oþ3 )
[MþH]þ 265.09715, found 265.09727.
Reaction time 4 h. Yield 1.3 g (76%), orange solid, mp 326e331 ꢀC
(DMF). nmax (neat) 3111, 1592, 1542, 1509, 1483, 1470, 1420, 1333,
1276, 1232, 1207, 1104 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 7.24
(1H, ddd, J ¼ 8.1, 6.8, 1.1 Hz), 7.60e7.71 (3H, m), 7.74 (1H, d,
J ¼ 16.8 Hz), 7.91 (2H, d, J ¼ 8.9 Hz), 8.11 (1H, dd, J ¼ 8.2,1.4 Hz), 8.28
(2H, d, J ¼ 8.9 Hz), 11.32 (1H, s) ppm. 13C NMR (100.56 MHz, DMSO-
4.29. Procedure for the preparation of quinolones 4leo
d6)
d: 117.9, 121.6, 121.8, 122.4, 124.2 (2ꢃ), 124.4, 127.8, 127.8, 127.8,
Ylide 5 (14.2 mmol, 5 g) and aldehyde 6meo (28.4 mmol) were
refluxed in dry 1,2-dichloroethane (25 mL) under a nitrogen at-
mosphere until the disappearance of 5 (TLC monitoring). In the case
of 6l, excess of 6l (15 mL) was used as the solvent and the reaction
mixture was heated in a glass sealed tube at 35 ꢀC until complete
dissolution of 5 (11 h). The reaction mixture was concentrated, and
the obtained residue was dissolved in hot EtOAc. The solution was
filtered and cooled to 0 ꢀC. The resulting white crystalline solid was
filtered off, and the filtrate was concentrated. The residue was
vacuum distilled yielding chloroketone 7lem, which was used
immediately in the next reaction step.
Crude chloroketone 7lem was dissolved in DMF (5 mL), and the
solution was added drop wise over 30 min to the cold (ꢁ5 ꢀC)
suspension of potassium anthranilate (9.8 mmol) in DMF (10 mL)
prepared according to the literature.3 The reaction mixture was
further stirred at ꢁ5 ꢀC. After starting materials were consumed
(TLC monitoring), the reaction mixture was poured into ice-cold
water (150 mL) and extracted with diethylether (2 ꢃ 50 mL). The
combined organic layers were washed with cold water (2 ꢃ 50 mL)
and dried over Na2SO4 and rotavaped at 20 ꢀC. The residue was
immediately dissolved in trifluoroacetic acid (20 mL) and refluxed
until the disappearance of intermediate 3 (TLC monitoring). The
reaction mixture was concentrated, and the residue was diluted
with EtOAc and cooled to ꢁ15 ꢀC. The resulting suspension was
filtered and washed with cold EtOAc. Crude product was purified by
crystallization.
130.5, 131.1, 138.0, 139.8, 142.7, 146.8, 170.0 ppm. HRMS (HESI) calcd
for (C17H13N2Oþ4 ) [MþH]þ 309.08698, found 309.08728.
4.25. 3-Hydroxy-2-((1E,3E)-4-phenylbuta-1,3-dien-1-yl)-quinolin-
4(1H)-one (4h)
Reaction time 24 h. Yield 1.8 g (63%), yellow solid, mp
284e288 ꢀC (2-Methoxyethanol). nmax (neat) 3346, 2836, 1635,
1613, 1545, 1477, 1448, 1421, 1370, 1246 cmꢁ1; 1H NMR (399.9 MHz,
DMSO-d6)
d
: 6.88 (1H, d, J ¼ 16.6 Hz), 7.01 (1H, d, J ¼ 15.8 Hz),
7.2e7.31 (3H, m), 7.38 (2H, t, J ¼ 7.5 Hz), 7.52 (1H, dd, J ¼ 15.8,
10.7 Hz), 7.55e7.61 (3H, m), 7.69 (1H, d, J ¼ 8.4 Hz), 8.09 (1H, dd,
J ¼ 8.2, 1.3 Hz), 8.80 (1H, brs), 11.21 (1H, s) ppm. 13C NMR
(100.56 MHz, DMSO-d6) d: 117.8, 121.4, 121.7, 121.8, 124.3, 126.7
(2ꢃ), 128.2, 128.7 (2ꢃ), 128.9, 130.7, 134.2, 136.6, 137.9, 138.8,
169.5 ppm. HRMS (HESI) calcd for (C19H16NOþ2 ) [MþH]þ 290.11756,
found 290.11741.
4.26. (E)-3-Hydroxy-2-(2-(thiophen-2-yl)vinyl)quinolin-4(1H)-one
(4i)
Reaction time 18 h. Yield 1.0 g (36%), orange solid, mp
285e288 ꢀC (2-Methoxyethanol/EtOH). nmax (neat) 3332, 2787,
1630, 1613, 1583, 1542, 1468, 1445, 1428, 1400, 1233, 1207 cmꢁ1; 1H
NMR (399.9 MHz, DMSO-d6)
d: 7.11e7.15 (2H, m), 7.22 (1H, dd,
ꢀ
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R. Horak et al. / Tetrahedron xxx (2017) 1e9
8
4.30. (E)-3-Hydroxy-2-(prop-1-en-1-yl)quinolin-4(1H)-one (4l)
4.35. 3-Hydroxy-2-phenethylquinolin-4(1H)-one (9a)
Reaction time 11 h. Yield 343 mg (12%), pale yellow solid, mp
Yield 120 mg (60%), almost white solid, mp 249e253 ꢀC. nmax
284e288 ꢀC (MeOH). nmax (neat) 3300, 3054, 2967, 1652, 1626,
(neat) 3064, 2980, 1632, 1593, 1533, 1482, 1468, 1437, 1403, 1371,
1579, 1544, 1466, 1407, 1368, 1237 cmꢁ1
;
1H NMR (399.9 MHz,
1251 cmꢁ1
;
1H NMR (399.9 MHz, DMSO-d6)
d
: 2.95e3.05 (4H, m),
7.18e7.32 (6H, m), 7.51e7.57 (2H, m), 8.10 (1H, d, J ¼ 8.1 Hz), 8.18
(1H, brs), 11.48 (1H, s) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d:
DMSO-d6)
d
: 1.97 (3H, dd, J ¼ 6.4, 1.3 Hz), 6.69 (1H, dd, J ¼ 16.2,
1.4 Hz), 6.80 (1H, dq, J ¼ 16.2, 6.4 Hz), 7.20 (1H, ddd, J ¼ 8.1, 6.9,
1.0 Hz), 7.55 (1H, ddd, J ¼ 8.5, 6.8, 1.5 Hz), 7.66 (1H, d, J ¼ 8.4 Hz),
8.08 (1H, dd, J ¼ 8.2, 1.4 Hz), 11.09 (1H, s) ppm. 13C NMR
30.1, 33.4, 117.7, 121.5, 122.2, 124.4, 126.0, 128.1, 128.3, 130.0, 134.4,
137.3, 137.9, 140.7, 168.9 ppm. HRMS (HESI) calcd for (C17H16NOþ2 )
[MþH]þ 266.11756, found 266.11769.
(100.56 MHz, DMSO-d6) d: 18.8, 117.9, 121.0, 121.4, 121.7, 124.3,
129.0, 130.5, 132.2, 137.6 (2ꢃ), 169.6 ppm. HRMS (HESI) calcd for
(C12H12NOþ2 ) [MþH]þ 202.08626, found 202.08630.
4.36. 3-Hydroxy-2-(4-phenylbutyl)quinolin-4(1H)-one (9h)
Yield 163 mg (74%), almost white solid, mp 255e259 ꢀC. nmax
4.31. (E)-2-(But-1-en-1-yl)-3-hydroxyquinolin-4(1H)-one (4m)
(neat) 3287, 3023, 2791, 1638, 1599, 1557, 1488, 1448, 1414, 1368,
1237 cmꢁ1 1H NMR (399.9 MHz, DMSO-d6)
; d: 1.58e1.74 (4H, m),
Reaction time 8 h. Yield 306 mg (10%), pale yellow solid, mp
2.62 (2H, t, J ¼ 7.5 Hz), 2.77 (2H, t, J ¼ 7.2 Hz), 7.13e7.27 (6H, m),
274e276 ꢀC (MeOH). nmax (neat) 3259, 2970, 1652, 1626, 1580, 1544,
7.51e7.55 (2H, m), 8.09 (1H, d, J ¼ 7.9 Hz), 8.09 (1H, brs), 11.44 (1H,
1466,1400,1368, 1233 cmꢁ1; 1H NMR (399.9 MHz, DMSO-d6)
d: 1.11
s) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 27.4, 27.8, 30.8, 34.9,
(3H, t, J ¼ 7.4 Hz), 2.29e2.37 (2H, m), 6.67 (1H, td, J ¼ 16.3, 1.5 Hz),
6.85 (1H, td, J ¼ 16.3, 6.4 Hz), 7.21 (1H, ddd, J ¼ 8.0, 7.0, 1.0 Hz), 7.55
(1H, ddd, J ¼ 8.5, 6.9, 1.5 Hz), 7.67 (1H, d, J ¼ 8.3 Hz), 8.49 (1H, brs),
117.7, 121.4, 122.1, 124.4, 125.6, 128.2 (2ꢃ), 129.9, 135.2, 137.3, 137.8,
142.0 ppm. HRMS (HESI) calcd for (C19H20NOþ2 ) [MþH]þ 294.14886,
found 294.14859.
11.08 (1H, s) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 13.0, 25.9,
117.9, 118.8, 121.4, 121.7, 124.3, 128.9, 130.5, 137.7 (2ꢃ), 138.5,
169.6 ppm. HRMS (HESI) calcd for (C13H14NOþ2 ) [MþH]þ 216.10191,
found 216.10186.
4.37. Fluorescence properties
The absorbance, excitation and emission fluorescence spectra of
the studied compounds were measured with a UVevis spectro-
photometer Cary 300 (Agilent Technologies) and a fluorescence
spectrometer Cary Eclipse (Varian). The methanolic solution of an
4.32. (E)-3-Hydroxy-2-(pent-1-en-1-yl)quinolin-4(1H)-one (4n)
individual compound at a concentration of 100
measured.
mg/mL were
Reaction time 6 h. Yield 260 mg (8%), pale yellow solid, mp
244e248 ꢀC (MeOH/EtOAc). nmax (neat) 3239, 2951, 2865, 1655,
1627, 1581, 1547, 1476, 1401, 1369, 1233 cmꢁ1; 1H NMR (399.9 MHz,
4.38. Agar diffusion test
DMSO-d6)
d
: 0.96 (3H, t, J ¼ 7.4 Hz), 1.48e1.57 (2H, m), 2.26e2.32
(2H, m), 6.68 (1H, td, J ¼ 16.3, 1.2 Hz), 6.80 (1H, td, J ¼ 16.3, 6.7 Hz),
7.21 (1H, ddd, J ¼ 8.0, 6.9, 1.0 Hz), 7.55 (1H, ddd, J ¼ 8.5, 6.8, 1.5 Hz),
7.67 (1H, d, J ¼ 8.3 Hz), 8.08 (1H, dd, J ¼ 8.2, 1.3 Hz) ppm. 13C NMR
Overnight cultures of test organisms were grown in LB broth for
18e24 h, and standard suspensions of ~1.5 ꢃ 108 cfu/mL were
prepared in sterile saline solution (0.9% NaCl) according to a BaSO4
0.5 McFarland Standard. Of this standardized suspension, 0.1 mL
was added to 34 mL of sterile, melted, and tempered (47e50 ꢀC)
Mueller-Hinton No. 2 agar. After gentle mixing, the inoculated
melted agar was poured into a sterile petri dish (145 mm ꢃ 20 mm,
Greiner Bio-One) and allowed to solidify next to the flame with lids
slightly ajar. The wells of 9 mm diameter were cut from the petri
(100.56 MHz, DMSO-d6) d: 13.6, 21.6, 34.9, 117.8, 119.9, 121.4, 121.7,
124.3, 128.8, 130.5, 136.8, 137.7 (2Х), 169.6. HRMS (HESI) calcd for
(C14H16NOþ2 ) [MþH]þ 230.11756, found 230.11759.
4.33. (E)-2-(Hept-1-en-1-yl)-3-hydroxyquinolin-4(1H)-one (4o)
dish agar and filled with 50 mL of the test sample solution. The test
Reaction time 5 h. Yield 256 mg (7%), pale yellow solid, mp
208e212 ꢀC (EtOAc). nmax (neat) 3067, 2950, 2922, 2852,1655,1640,
1583, 1548, 1488, 1426, 1431, 1369, 1228 cmꢁ1; 1H NMR (399.9 MHz,
solutions were made at 20 mM in DMSO and diluted in MeOH to
obtain a final concentration of 2 mM. The petri dish was incubated
at 37 ꢀC for 18e24 h, and the inhibition zone diameters were
measured (mm) with an electronic caliper after 24e48 h.
DMSO-d6)
d
: 0.89 (3H, t, J ¼ 7.0 Hz), 1.29e1.37 (4H, m), 1.50 (2H, p,
J ¼ 7.1 Hz), 2.30 (2H, q, J ¼ 6.9 Hz), 6.67 (1H, d, J ¼ 16.3 Hz), 6.80 (1H,
td, J ¼ 16.1, 6.7 Hz), 7.20 (1H, dd, J ¼ 7.6, 7.4 Hz), 7.55 (1H, ddd,
J ¼ 7.7, 7.6, 1.2 Hz), 7.67 (1H, d, J ¼ 8.4 Hz), 8.49 (1H, brs), 11.06 (1H,
4.39. MIC determination
s) ppm. 13C NMR (100.56 MHz, DMSO-d6)
d: 13.8, 21.9, 28.0, 30.7,
Antibacterial activity of the compounds was determined by
measuring their MIC using the broth microdilution method. Each
well of a 96-well microtiter plate was filled with 50 mL of sterile iron
32.8, 117.8, 119.7, 121.4, 121.7, 124.3, 128.8, 130.5, 137.1, 137.6, 137.7,
169.6 ppm. HRMS (HESI) calcd for (C16H20NOþ2 ) [MþH]þ 258.14886,
found 258.14900.
deficient MH2 broth. Each test compound was dissolved in DMSO
making a 10 mM solution, and then diluted with sterile MH2 broth
4.34. Procedure for the preparation of 2-alkyl quinolones 9
to 800 mM. Exactly 50 mL of the compound solution was added to
the first well of the microtiter plate, and 2-fold serial dilutions were
made down each row of the plate. A pre culture of bacteria was
grown in Luria-Bertani broth overnight at 37 ꢀC. This was diluted to
A suspension of quinolone 4a or 4h (75 mmol) and 10% Pd/C
(50 mg) in 2-methoxyethanol (30 mL) was stirred vigorously under
hydrogen atmosphere at 40 ꢀC for 5 h. The reaction mixture was
filtered, and most of the solvent was evaporated. The resulting
suspension was diluted with EtOH and left in refrigerator over-
night. White crystals of 9 were filtered off, washed with small
amount of cold EtOH and dried in vacuum.
McFarland standard 0.5 (1.5 ꢃ 108 CFU) with saline. 100
bacterial suspension was further diluted with 14.9 mL of MH2
broth. Exactly 50
L of bacterial (IN BROTH) inoculum (1 ꢃ 106 CFU/
mL) was added to each well giving a total volume of 100 L/well,
5 ꢃ 105 CFU/mL and a compound concentration gradient of
mL of the
m
m
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Please cite this article in press as: Horak R, et al., Synthesis of 2-alkenyl-3-hydroxyquinolin-4(1H)-ones as promising antimicrobial and
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R. Horak et al. / Tetrahedron xxx (2017) 1e9
9
200e0.1 m
M. The plate was incubated at 37 ꢀC. After 18 h, each well
ꢀꢁ
ꢀꢁ
ꢁ ꢁ
ꢀ
7. Hradil P, Hlavac J, Soural M, Hajdúch M, Kolar M, Vecerova R. Mini Rev Med
Chem. 2009;9:696.
was examined visually for bacterial growth. The MIC was recorded
as the lowest compound concentration required to inhibit bacterial
growth as judged by turbidity relative to a row of wells diluted with
the solvent DMSO as a growth control. Ciprofloxacin was included
8. Li L, Wang HK, Kuo SC, et al. J Med Chem. 1994;37:3400.
9. Iwanowicz, E. J.; Watterson, S. H.; Dhar, T. G. M.; Pitts, W. J.; Gu, H. H.
US6919335 B2, July 19, 2005.
10. Loya S, Rudi A, Tal R, Kashman Y, Loya Y, Hizi A. Arch Biochem Biophys.
1994;309:315.
in a control row at a concentration gradient of 5 mg/mL-0.0025 mg/L.
ꢀꢁ
11. Motyka K, Hlavac J, Soural M, Funk P. Tetrahedron Lett. 2010;51:5060.
ꢀꢁ
12. Motyka K, Hlavac J, Soural M, et al. Tetrahedron Lett. 2011;52:715.
ꢁ
ꢀ
ꢀꢁ
13. Motyka K, Vankova B, Hlavac J, Soural M, Funk P. J Fluoresc. 2011;21:2207.
14. Kadric J, Motyka K, Dzubak P, Soural M. Tetrahedron Lett. 2014;55:3592.
15. Yushchenko DA, Bilokin MD, Pyvovarenko OV, Duportail G, Mely Y,
Pivovarenko VG. Tetrahedron Lett. 2006;47:905.
Acknowledgement
This work was supported by the Czech National Program for
Sustainability (project LO1304) and Ministry of Industry and Trade
(project FV20250).
16. Yushchenko DA, Shvadchak VV, Klymchenko AS, Duportail G, Mely Y,
Pivovarenko VG. New J Chem. 2006;30:774.
17. Hodgkinson JT, Galloway WRJD, Saraf S, et al. Org Biomol Chem. 2011;9:57.
18. Hodgkinson JT, Galloway WRJD, Welch M, Spring DR. Nat Protoc. 2012;7:1184.
19. Hodgkinson JT, Bowden SD, Galloway WRJD, Spring DR, Welch M. J Bacteriol.
2010;192:3833.
Appendix A. Supplementary data
20. Lu C, Kirsch B, Maurer CK, et al. Eur J Med Chem. 2014;79:173.
21. Lu C, Maurer CK, Kirsch B, Steinbach A, Hartmann RW. Angew Chem Int Ed.
2014;53:1109.
22. Lu C, Kirsch B, Zimmer C, et al. Chem Biol. 2012;19:381.
23. Hinkel LH, Avling EE, Dippy JF. J Chem Soc. 1935:539.
24. Jacques J, Marquet A. Org Synth Coll. 1988;6:175.
Supplementary data related to this article can be found at
https://doi.org/10.1016/j.tet.2017.12.010.
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Please cite this article in press as: Horak R, et al., Synthesis of 2-alkenyl-3-hydroxyquinolin-4(1H)-ones as promising antimicrobial and
fluorescent agents, Tetrahedron (2017), https://doi.org/10.1016/j.tet.2017.12.010