N-alkoxyphenylhydroxynaphthalenecarboxamides and their antimycobacterial activity

Article abstract of DOI:10.3390/molecules21081068

A series of nineteen N-(alkoxyphenyl)-2-hydroxynaphthalene-1-carboxamides and a series of their nineteen positional isomers N-(alkoxyphenyl)-1-hydroxynaphthalene-2-carboxamides were prepared and characterized. Primary in vitro screening of all the synthes

Full text of DOI:10.3390/molecules21081068

molecules
Article
N-Alkoxyphenylhydroxynaphthalenecarboxamides
and Their Antimycobacterial Activity
Tomas Gonec 1,*, Sarka Pospisilova 2, Tereza Kauerova 3, Jiri Kos 1, Jana Dohanosova 4,
Michal Oravec 5, Peter Kollar 3, Aidan Coffey 6, Tibor Liptaj 4, Alois Cizek 2 and
Josef Jampilek 7,
*
1
Department of Chemical Drugs, Faculty of Pharmacy, University of Veterinary and Pharmaceutical Sciences,
Palackeho 1, Brno 61242, Czech Republic; jurd@email.cz
2
3
4
Department of Infectious Diseases and Microbiology, Faculty of Veterinary Medicine,
University of Veterinary and Pharmaceutical Sciences, Palackeho 1, Brno 61242, Czech Republic;
sharka.pospisilova@gmail.com (S.P.); cizeka@vfu.cz (A.C.)
Department of Human Pharmacology and Toxicology, Faculty of Pharmacy,
University of Veterinary and Pharmaceutical Sciences, Palackeho 1, Brno 61242, Czech Republic;
tereza.kauerova@gmail.com (T.K.); kollarp@vfu.cz (P.K.)
Central Laboratories, Faculty of Chemical and Food Technology,
Slovak University of Technology in Bratislava, Radlinskeho 9, Bratislava 81237, Slovakia;
jana.dohanosova@stuba.sk (J.D.); tibor.liptaj@stuba.sk (T.L.)
Global Change Research Institute CAS, Belidla 986/4a, Brno 60300, Czech Republic; oravec.m@czechglobe.cz
Department of Biological Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland;
aidan.coffey@cit.ie
5
6
7
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Comenius University, Odbojarov 10,
Bratislava 83232, Slovakia
*
Correspondence: t.gonec@seznam.cz (T.G.); josef.jampilek@gmail.com (J.J.); Tel.: +420-541-562-938 (T.G.)
Academic Editor: Derek J. McPhee
Received: 27 July 2016; Accepted: 12 August 2016; Published: 16 August 2016
Abstract: A series of nineteen N-(alkoxyphenyl)-2-hydroxynaphthalene-1-carboxamides and a
series of their nineteen positional isomers N-(alkoxyphenyl)-1-hydroxynaphthalene-2-carboxamides
were prepared and characterized. Primary in vitro screening of all the synthesized compounds
was performed against Mycobacterium tuberculosis H37Ra, M. kansasii and M. smegmatis. Screening
of the cytotoxicity of the compounds was performed using human monocytic leukemia THP-1
cells. Some of the tested compounds showed antimycobacterial activity comparable with or higher
than that of rifampicin. For example, 2-hydroxy-N-(4-propoxyphenyl)-naphthalene-1-carboxamide
showed the highest activity (MIC = 12 µM) against M. tuberculosis with insignificant cytotoxicity.
N-[3-(But-2-yloxy)phenyl]- and N-[4-(but-2-yloxy)phenyl]-2-hydroxy-naphthalene-1-carboxamide
demonstrated high activity against all tested mycobacterial strains and insignificant cytotoxicity.
N-(Alkoxyphenyl)-1-hydroxynaphthalene-2-carboxamides demonstrated rather high effect against
M. smegmatis and M. kansasii and strong antiproliferative effect against the human THP-1 cell line.
Lipophilicity was found as the main physicochemical parameter influencing the activity. A significant
decrease of mycobacterial cell metabolism (viability of M. tuberculosis H37Ra) was observed
using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) assay. Structure-activity
relationships are discussed.
Keywords: hydroxynaphthalenecarboxamides; in vitro antimycobacterial activity; MTT assay;
lipophilicity; structure-activity relationships
Molecules 2016, 21, 1068; doi:10.3390/molecules21081068
www.mdpi.com/journal/molecules

Molecules 2016, 21, 1068
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1. Introduction
In spite of the approval of some new antituberculosis drugs, such as bedaquillin or delamanid [
tuberculosis (TB) now ranks alongside human immunodeficiency virus as a leading cause of deaths
worldwide [ ]. Despite the decrease in TB incidence since the 1950s due to the introduction of
1],
2
new antitubercular agents to clinical practice, morbidity and mortality have risen again since the
1980s; TB has again become a major bacterial cause of worldwide mortality, and thus it remains a
serious global problem. Based on the new World Health Organization tuberculosis report, TB killed
1.5 million people in 2014 worldwide; 9.6 million people are estimated to have fallen ill with TB in
2014. As estimated, 480,000 cases of multidrug-resistant TB (MDR-TB) occurred in 2014 [2]. The rate of
successful treatments has also decreased due to the emergence of drug resistant, cross-, multidrug-,
extensively- and totally-resistant strains. The increase in the number of new infections is also associated
with immunocompromised populations. In addition, more frequent occurrences of lethal complications
associated with immunocompromised populations include systemic infections caused by common,
initially non-pathogenic mycobacterial strains (e.g., M. kansasii, M. avium, M. smegmatis, etc.), which
cause difficult-to-treat or incurable diseases due to suppressed immunity. These non-tuberculous
mycobacteria (NTM) are now recognized as significant human pathogens and cause diseases (such as
pulmonary disease, lymphadenitis, skin and soft tissue disease, gastrointestinal and skeletal infections)
that result in significant morbidity. The emergence of MDR-TB and NTM makes the discovery of new
molecular scaffolds a priority to achieve effective control of both TB and NTM [3].
Hydroxynaphthalene-2-carboxanilides can be considered as cyclic analogues of salicylanilides that
have expressed promising results as potential antimicrobial and antimycobacterial agents [4–6] (and
refs. therein)]. Their antimicrobial effects are connected with the ability of vicinal hydroxyarylamides
to inhibit various enzymatic systems in bacteria [[4–6] (and refs. therein)]. In addition, the presence of
an amide group with a hydrophobic residue in its close vicinity is able, due to its electron properties, to
interact and bind with a number of enzymes/receptors and affect the biological response by means of
these target sites. The properties of the amide moiety can be easily modified by various substitutions [7].
Thus the presence of an amide-like moiety is characteristic for various antibacterial, antimycobacterial
or antiparasitic agents [4–15].
N-Aryl-2-hydroxynaphthalene-1-carboxamides and N-aryl-1-hydroxynaphthalene-2-carbox-amides
have shown activity against mycobacterial species [11,16]; therefore various alkoxy derivatives have
been designed from 2-hydroxynaphthalene-1-carboxylic acid and 1-hydroxynaphthalene-2-carboxylic
acid. The present work is focused on synthesis and investigation of the biological activity of
ring-substituted carboxamides of the above-mentioned acids as promising antimycobacterial agents.
2. Results and Discussion
2.1. Chemistry and Physicochemical Properties
The condensation of 2-hyroxynaphthalene-1-carboxylic acid or 1-hydroxynaphthalene-2-carboxylic
acid with appropriate alkoxy-substituted anilines using phosphorus trichloride in dry chlorobenzene
under microwave conditions yielded a series of nineteen N-substituted-2-hydroxy-naphthalene-1-
carboxamides
14c (series II), see Scheme 1. Alkoxy-substituted anilines (except commercially available o-, m-
and p-anisidine) were prepared from corresponding aminophenol and alkyl bromide according to
De Marco et al. [17] and were reported recently [18]. Compounds 2c 16] and 9c 11] have been
1–7c (series I) and nineteen N-substituted-1-hydroxynaphthalene-2-carboxamides
8
–
1
–
[
8–
[
already published by our team, nevertheless they are also mentioned here to complete the overview of
biological activities and structure-activity relationships.

Molecules 2016, 21, 1068
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Scheme 1.
Synthesis of N-(alkoxyphenyl)-2-hydroxynaphthalene-1-carboxamides 7c and
1
–
N-(alkoxyphenyl)-1-hydroxynaphthalene-2-carboxamides
chlorobenzene, microwave irradiation (MW).
8–
14c. Reagents and conditions: (a) PCl3,
Within structure-activity relationships, various parameters describing physicochemical properties
are investigated. Lipophilicity is a property that has a major effect on solubility, absorption, distribution
and biotransformation as well as pharmacological activity, because drugs cross biological membranes
through passive transport, which strongly depends on their lipophilicity. Lipophilicity was observed
as the most important descriptor affecting the antimycobacterial activity for both series, see below.
In the current investigation, the lipophilicity values expressed as log P were calculated using
ACD/Percepta ver. 2012. Log P values of both series as well as the used standards isoniazid (INH)
and rifampicin (RIF) can be compared in Table 1. In general, N-(alkoxyphenyl)-1-hydroxynaphthalene-
2-carboxamides
N-(alkoxyphenyl)-2-hydroxynaphthalene-1-carbox-amides
8
–
14c (series II) are characterized by slightly higher calculated lipophilicity than
7c (series I) with the exception of
1
–
compound 3c (R = 4-OC2H5) that has higher log P value than compound 10c. Within individual series,
the lipophilicity increases as follows: OCH3 < OC2H5 < OCH(CH3)2 < OC3H7 < OCH(CH3)CH2CH3
< OC4H9. The ortho-substituted derivatives showed the highest calculated log P values, while
para-substituted derivatives demonstrated the lowest log P values, except 11c (R = 4-OC3H7) and 12c
(R = 4-OC4H9) that have the same calculated lipophilicity values as the ortho-substituted derivatives.
In addition to lipophilicity, molar volume (MV) of substituents and electronic
substituents are largely employed in structure-activity relationship analysis. The corresponding
MV and values of phenyl ring substituents 14c are shown in Table 1 and were also predicted
σ parameters of
σ
1–
by ACD/Percepta.
2.2. In Vitro Antimycobacterial Evaluation
The evaluation of the in vitro antimycobacterial activity of the compounds was performed against
Mycobacterium tuberculosis H37Ra ATCC 25177 (MT), M. kansasii DSM 44162 (MK) and M. smegmatis
ATCC 700084 (MS), see Table 1. To lower risk and make manipulation in the laboratory easier, surrogate
model pathogens for M. tuberculosis can be used in laboratory studies. Avirulent M. tuberculosis strain
H37Ra is very closely related to and has similar pathology as human-infecting M. tuberculosis strains,
making it a good model for study especially because of the lower risk for laboratory workers [19].
M. kansasii, the most virulent of the NTM, causes nontuberculous mycobacterial lung infections,
which are now very common, and can be indistinguishable from tuberculosis [20]. M. smegmatis
is an ideal representative of a fast-growing nonpathogenic microorganism, particularly useful in
studying basic cellular processes of special relevance to pathogenic mycobacteria [21]. Therefore
additionally M. kansasii and M. smegmatis were chosen as model species for screening of prospective
antimycobacterial drugs to control mycobacterial diseases. The potency of the compounds was
expressed as the minimum inhibitory concentration (MIC) that is defined for mycobacteria as 90% or
greater (IC90) reduction of growth in comparison with the control.

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Table 1. Structures of discussed ring-substituted hydroxynaphthalenecarboxamides
values of log P, molar volume (MV (cm3)) of R substituents and electronic
1
–
14c; calculated
σ
parameters of R
substituents; in vitro antimycobacterial activity (MIC) of compounds in comparison with isoniazid
(INH) and rifampicin (RIF) standards; in vitro antiproliferative assay (IC50) of chosen compounds.
MIC (µM)
MV a
σ a
Compound
log P a
IC50 (µM)
R
MT
MS
MK
1
H
2-OCH3
3-OCH3
4-OCH3
2-OC2H5
3-OC2H5
4-OC2H5
2-OC3H7
3-OC3H7
4-OC3H7
2-OC4H9
3-OC4H9
4-OC4H9
4.49
4.54
4.51
4.30
4.88
4.83
4.76
5.22
5.14
5.21
5.53
5.49
5.54
5.15
5.06
5.04
5.47
5.40
5.40
0
0
94
852
852
852
26
813
26
37
46
12
745
23
745
31
486
873
218
436
832
416
832
796
398
398
763
381
763
796
398
796
763
12
15
873
109
218
832
208
104
99
199
99
763
190
95
>30
-
-
-
>30
-
>30
>30
2a
2b
2c
3a
3b
3c
4a
4b
4c
5a
5b
5c
6a
6b
6c
7a
7b
7c
37.15
37.15
37.15
53.66
53.66
53.66
70.16
70.16
70.16
86.67
86.67
86.67
70.54
70.54
70.54
87.05
87.05
87.05
−0.28
0.11
−0.27
−0.29
0.10
−0.29
−0.29
0.14
−0.28
−0.28
0.14
−0.28
−0.47
0.10
8.97 ± 0.34
>30
>30
>30
>30
>30
2-OCH(CH3)2
3-OCH(CH3)2
4-OCH(CH3)2
2-OCH(CH3)CH2CH3
3-OCH(CH3)CH2CH3
4-OCH(CH3)CH2CH3
99
199
99
95
47
778
25
44
23
23
8.84 ± 0.22
−0.45
−0.27
0.14
−0.27
>30
8.35 ± 1.25
>30
12
95
>30
MIC (µM)
MV a
σ a
Compound
log P a
IC50 (µM)
R
MT
MS
MK
8
9a
9b
H
2-OCH3
3-OCH3
4-OCH3
2-OC2H5
3-OC2H5
4-OC2H5
2-OC3H7
3-OC3H7
4-OC3H7
2-OC4H9
3-OC4H9
4-OC4H9
4.52
4.61
4.56
4.37
4.92
4.88
4.67
5.26
5.21
5.27
5.60
5.54
5.60
5.18
5.13
5.11
5.52
5.47
5.46
−0.63
2.24
0
0
97
852
852
852
813
813
813
778
24
778
745
23
745
778
389
778
745
23
243
873
873
873
832
832
832
796
199
796
763
190
763
796
796
796
763
12
15
873
873
873
832
52
832
24
49
>30
-
-
-
37.15
37.15
37.15
53.66
53.66
53.66
70.16
70.16
70.16
86.67
86.67
86.67
70.54
70.54
70.54
87.05
87.05
87.05
-
−0.28
0.11
9c
−0.27
−0.29
0.10
−0.29
−0.29
0.14
−0.28
−0.28
0.14
−0.28
−0.47
0.10
10a
10b
10c
11a
11b
11c
12a
12b
12c
13a
13b
13c
14a
14b
14c
INH
RIF
a
-
3.02 ± 0.96
-
-
1.37 ± 0.72
24
763
47
>30
-
1.80 ± 0.32
23
>30
2-OCH(CH3)2
3-OCH(CH3)2
4-OCH(CH3)2
2-OCH(CH3)CH2CH3
3-OCH(CH3)CH2CH3
4-OCH(CH3)CH2CH3
-
796
796
49
47
47
23
29
0.15
-
4.32 ± 0.74
9.39 ± 1.39
9.03 ± 1.18
1.17 ± 0.38
3.41 ± 0.41
>30
−0.45
−0.27
0.14
−0.27
745
58
10
12
117
19
-
-
-
-
>30
calculated using ACD/Percepta ver. 2012 (Advanced Chemistry Development, Inc., Toronto, ON, Canada,
2012); MT = M. tuberculosis H37Ra ATCC 25177, MS = Mycobacterium smegmatis ATCC 700084 and MK =
M. kansasii DSM 44162.

Molecules 2016, 21, 1068
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Compounds series I and II can be considered as positional isomers that differ from each other
by the electron density of carboxamide and phenolic moieties as well as by the steric properties
of the entire scaffolds. Nevertheless, in general, compounds
1–7c demonstrated higher potency
against M. tuberculosis, while compounds 14c showed higher effect against the two NTM strains.
8–
Unfortunately, compounds of series II showed higher antiproliferative effect on human cells, see
Table 1 and Section 2.3.
The dependences of the antitubercular activity of the compounds against M. tuberculosis expressed
as log (1/MIC (M)) on lipophilicity expressed as log P are illustrated in Figure 1A,B. Similar trends can
be observed also for dependences of activities on molar volume (MV) of R substituents; therefore they
are not illustrated. Based on Figure 1A, it can be stated that compounds of series I in the range of log P
values from ca. 4.8 to 5.5 showed potency against M. tuberculosis. The quasi-parabolic dependences
of activity on log P (with log P optimum ca. 5) for the ortho- and para-substituted derivatives can
be observed. The unexpected significant activity slump of both butoxy derivatives 5a and 5c can be
caused by a steric hindrance or limited solubility. On the other hand, for meta-substituted derivatives
of series I, the activity increased up to log P ca. 5.1 (4b, R = 3-OC3H7), see Figure 1B, and then only
insignificantly increased up to 5.49 (compound 5b) with increasing log P. It can be only speculated
whether the activity would remain constant or it would decrease with a further prolongation of the
alkoxy chain. Only 3-propoxy (11b), 3-butoxy (12b) and 3-sec-butoxy (14b) substituted compounds of
series II showed activity comparable with that of series I. In general, the meta-substituted derivatives
of series II demonstrated the same course of dependence (activity increase from log P ca. 5.2) as
the meta-substituted derivatives of series I, see Figure 1B. The ortho- and para-substituted derivatives
of series II expressed no effect; therefore they are not illustrated. It is important to note that the
dependence of the antitubercular activity of the ortho- and para-substituted derivatives on electronic
σ
parameters was not observed; the antitubercular activity of the meta-substituted derivatives of series I
and II is influenced by electron-donor properties of the substituents:
vs. σ ≈ 0.10 of the rest of ineffective C(3) substituted compounds.
σ = 0.14 (compounds 4b, 5b, 7b)
0
A
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
4.2
4.4
4.6
4.8
5.0
5.2
5.4
5.6
5.8
A
log P
H
ortho para
Figure 1. Relationships between in vitro antitubercular activity against M. tuberculosis log(1/MIC
(mol/L)) and lipophilicity expressed as log P of unsubstituted, ortho- and para-substituted derivatives
of series I (A) and meta-substituted derivatives of series I and II (B).
Additionally, a standard MTT assay was performed on the selected most effective compounds
against M. tuberculosis H37Ra, the MICs of which were previously determined through alamarBlue
assays, see Table 1. The MTT assay is a well-characterized method of assessing cell growth through
measurement of respiration. For the purpose of this assay, a positive result was recorded when the
MTT measured viability of M. tuberculosis H37Ra was less than 70% after exposure to the MIC of
each test compound. As such, a low level of cell viability may suggest inhibition of cell growth
through respiratory inhibition [22]. All the selected compounds, i.e., 3a (R = 2-OC2H5, 30.6%), 3c
(R = 4-OC2H5, 9.96%), 4c (R = 4-OC3H7, 5.90%), 5b (R = 3-OC4H9, 7.38%), 6c (R = 4-OCH(CH3)2,
8.96%), 7b (R = 3-OCH(CH3)CH2CH3, 7.38%), 7c (R = 4-OCH(CH3)CH2CH3, 8.86%), 11b (R = 3-OC3H7,

Molecules 2016, 21, 1068
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15.13%), 12b (R = 3-OC4H9, 9.96%) and 14b (R = 3-OCH(CH3)CH2CH3, 9.96%) showed less than 70%
viability of M. tuberculosis H37Ra at the tested concentration equal to MICs.
Unsubstituted compounds
1 and 8 showed the highest effect against M. kansasii, nevertheless, it
can be stated that in general, the compounds of series II expressed higher potency against M. kansasii
than compounds of series I. The bilinear dependence can be found for compounds of series I,
see Figure 2A, where relationships between the activity against M. kansasii and the lipophilicity
of compounds are illustrated. The activity increases with increasing lipophilicity to the optimum of
log P ca. 5.4, and then a significant activity decrease for butoxy derivatives can be found, similarly as
mentioned above. On the other hand, the effect of the meta- and para-substituted derivatives of series II
increases rapidly up to log P ca. 5, and then the activity is approximately linear, see Figure 2B. Similar
insignificant influences of meta- and para-substituents were observed also by Kos et al. [14,15]. Among
the ortho-substituted derivatives of series II, only 11a (R = 2-OC3H7) and 14a (R = 2-OCH(CH3)CH2CH3)
demonstrated an activity at log P ca. 5.3. The dependences of activities on the molar volume of R
substituents are not illustrated due to their similarity with dependences on lipophilicity.
Figure 2. Relationships between in vitro antimycobacterial activity against M. kansasii log (1/MIC
(mol/L)) and lipophilicity expressed as log P of compounds 1–7c (A) and compounds 8–14c (B).
The compounds of both series showed only moderate activity against M. smegmatis, except
0
0
derivatives substituted by a sec-butoxy chain in C(3) and C(4) positions (compounds 7b, 7c, 14b
and 14c). Because especially meta-substituted compounds 7b and 14b showed good activity against
M. tuberculosis and M. kansasii, it can be assumed that the physicochemical and geometrical properties
of the branched sec-butoxy chain are advantageous from the aspect of mycobacteria growth inhibition.
As mentioned above, the discussed compounds are cyclic analogues of salicylanilides. The phenolic
moiety spatially close to the amide group forms a hypothetic six-membered ring by H-bonds with amide
nitrogen, and thus a stable hydrophobic coplanar anionic form with a delocalized negative charge is
generated, which seems to be decisive in the proton motive force. This enables the molecule to penetrate
biological membranes not only as protonated neutral compound but also in the charged state. Thus
salicylanilides are able to induce the uncoupling of oxidative phosphorylation and photophosphorylation
in mitochondria, chloroplasts and other energy-transducing membranes [
the discussed structures could be considered as compounds that affect the proton motive force
across membranes (uncouplers) [ 25 28]. The ortho-substituted derivatives of series I showed
4,23–26]; therefore also
4, –
potency especially against M. tuberculosis. The broader antimycobacterial activity of the meta- and
para-substituted derivatives in comparison with the ortho-substituted compounds can be related to the
steric effect of the spatially close ortho-substituents [29]. A moiety in the ortho position results in a
change of the molecule planarity [30], and different electron densities at the carbonyl and consequently
at the phenolic moiety, which can break the formation of coplanar anionic form with a delocalized
negative charge (i.e., uncoupler effect) and influence the potential of binding of the carboxamide
and the phenolic groups to possible targets (sensitive enzymatic systems affecting proliferative
cell functions as mentioned in Introduction) in a mycobacterial cell. In the case of the meta- and

Molecules 2016, 21, 1068
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para-derivatives, the described secondary steric effect did not manifest [18
,
29,
30]. The para-substituted
as well as the meta-substituted derivatives should have practically a linear/planar structure as was, for
example, described for a similar type of molecule, where the structural analysis displayed a planar
structure [31
multitarget activity that should not be very different from that of other planar antimycobacterial
agents [ 24 30 35 37]. The lipophilicity of meta- and para-substituted derivatives was found as the
–34]. Thus, it seems that the mode of action of this type of compounds demonstrates
4,6, , , –
factor conducive to the activity of such structures. More lipophilic structures displayed relatively
higher efficiency, and simultaneously planar structures easier permeate through various types
of membranes.
2.3. In Vitro Antiproliferative Assay
The preliminary in vitro screening of the antiproliferative activity of the most effective
antimycobacterial compounds as well as both standards was performed using Water Soluble
Tetrazolium Salts-1 (WST-1) assay kit [38] and the human monocytic leukemia THP-1 cell line by
means of the method described recently [14]. The antiproliferative activity was evaluated as the IC50
value (compound concentration causing 50% inhibition of cell population proliferation), see Table 1.
A compound is considered as cytotoxic when it demonstrates a toxic effect on cells at the concentration
up to 10
µM [39], and the highest tested concentration that was used for the toxicity assay was 3-fold
this value.
As mentioned above, the compounds of series I showed lower antiproliferative effect than the
compounds of series II, see Table 1. The antiproliferative-efficient compounds inhibit mitochondrial
dehydrogenases (the principle of WST-1 assay kit), the activity of which directly correlates with
the number of metabolically active cells in the culture. All the compounds from series I effective
against M. tuberculosis showed IC50 > 30
µM, i.e., the treatment with this concentration did not lead
to significant antiproliferative effect on THP-1 cells, and compounds 3a
,
4c 5b 7b and 7c inhibited
,
,
selectively vital processes in M. tuberculosis. Based on these observations, it can be concluded that
the discussed amides can be considered as non-toxic agents for subsequent design of novel potential
antitubercular agents. Unfortunately, the potency of these compounds against NTM strains is medium
or moderate, except for compound 7b. The antimycobacterial potency of compounds from series II
is connected with their rather nonselective prokaryote and eukaryote antiproliferative effect; IC50
ranged from 1.2 to 9.4
was 0.16 ± 0.07 µM), except for compounds
IC50 > 30 M, see Table 1. These can be considered as compounds with noteworthy effect against
M. kansasii.
µM (for comparison, e.g., IC50 of camptothecin, assessed in this line formerly,
8
(R = H), 11c (R = 4-OC3H7) and 12c (R = 4-OC4H9) with
µ
3. Experimental Section
3.1. General Information
All reagents were purchased from Sigma-Aldrich (St. Louis, MO, USA) or Merck (Darmstadt,
Germany). Reactions were carried out in a StartSYNTH microwave labstation (Milestone, Sorisole,
Italy). Melting points were determined on a Kofler hot plate apparatus HMK (Franz Kustner Nacht
GK, Dresden, Germany) and left uncorrected. Column chromatography was performed on a 200 mL
column (Sigma-Aldrich) using Silica gel 60 (0.040–0.063 mm, Merck). Infrared (IR) spectra were
recorded on a Smart MIRacle
™ ATR ZnSe for Nicolet™ Impact 400 FT-IR spectrometer (Thermo Fisher
Scientific, West Palm Beach, FL, USA). All 1H- and 13C-NMR spectra were recorded on an Agilent
VNMRS 600 MHz system (600 MHz for 1H and 150 MHz for 13C, Agilent Technologies, Santa Clara,
CA, USA) equipped with a triple resonance HCN probe at 25 ◦C in DMSO-d6. Chemical shifts are
reported in ppm (δ) using the signal of the solvent (DMSO; δ δ
(1H) = 2.5 ppm, (13C) = 49.5 ppm)
for referencing. High-resolution mass spectra were measured using a high-performance liquid
chromatograph Dionex UltiMate® 3000 (Thermo Fisher Scientific) coupled with an LTQ Orbitrap

Molecules 2016, 21, 1068
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XL™ Hybrid Ion Trap-Orbitrap Fourier Transform Mass Spectrometer (Thermo Fisher Scientific) with
injection into HESI II in the positive mode.
3.2. Synthesis
3.2.1. General Procedure for Synthesis of N-(Alkoxyphenyl)-2-hydroxynaphthalene-1-carboxamides
1–7c and N-(Alkoxyphenyl)-1-hydroxynaphthalene-2-carboxamides 8–14c
2-Hydroxynaphthalene-1-carboxylic acid or 1-hydroxynaphthalene-2-carboxylic acid (5.30 mmol)
and appropriate alkoxyaniline (5.30 mmol) were suspended in 30 mL of dry chlorobenzene.
Phosphorous trichloride (2.65 mmol) was◦added dropwise, and reacting mixture was heated in
the microwave reactor for 15 min at 130 C using infrared flask-surface control of temperature.
Solvent was evaporated in vacuum; residue solid was washed with 2M HCl and crystallized from
aqueous ethanol. If necessary, column chromatography was used for further purification (mobile
phase DCM:MeOH 19:1).
2-Hydroxy-N-phenylnaphthalene-1-carboxamide (1, CAS 16670-63-6), 2-hydroxy-N-(2-methoxyphenyl)naphtha-
lene-1-carboxamide (2a, CAS 337955-96-1), 2-hydroxy-N-(3-methoxyphenyl)naphthalene-1-carboxamide (2b
,
CAS 1463483-65-9) and 2-hydroxy-N-(4-methoxyphenyl)naphthalene-1-carboxamide (2c, CAS 856062-47-0)
were synthesized and characterized recently [16].
N-(2-Ethoxyphenyl)-2-hydroxynaphthalene-1-carboxamide (3a, CAS 858031-71-7). Yield 62%; Mp 116 ◦C
◦
(155–157 C) [40]; IR (cm−1): 3318 (
ν
δ
NH), 1623 (
ν C=O), 1539 (δ NH), 1391 (δ COH), 1284 (ν CN), 1118
(ν
CArCO); 1H-NMR (DMSO-d6),
: 10.48 (br. s, 1H, OH), 9.43 (s, 1H, NH), 8.19 (d, J = 9.2 Hz, 1H,
ArHPhe), 8.15 (d, J = 9.2 Hz, 1H, ArHNaph), 7.88 (d, J = 8.4 Hz, 1H, ArHNaph), 7.84 (d, J = 7.0 Hz, 1H,
ArHNaph), 7.48 (td, J = 8.4 Hz, J = 1.1 Hz, 1H, ArHNaph), 7.34 (td, J = 8.1 Hz, J = 1.1 Hz, 1H, ArHNaph),
7.24 (d, J = 9.2 Hz, 1H, ArHNaph), 7.13–6.96 (m, 3H, ArHPhe), 4.10 (q, J = 7.0 Hz, 2H, CH2), 1.36 (t,
J = 7.0 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 165.06, 152.42, 148.91, 131.81, 131.05, 127.94, 127.73,
127.73, 126.85, 124.50, 124.12, 123.03, 121.74, 120.33, 118.25, 116.60, 112.21, 63.99, 14.57; HR-MS: for
C19H17NO3 [M + H]+ calculated 308.12812 m/z, found 308.12827 m/z.
N-(3-Ethoxyphenyl)-2-hydroxynaphthalene-1-carboxamide (3b). Yield 64%; Mp 133 ◦C; IR (cm−1): 3323 (
NH), 1623 ( C=O), 1536 ( NH), 1387 ( COH), 1284 ( CN), 1158 (
CArCO); 1H-NMR (DMSO-d6),
: 10.34 (s, 1H, NH), 10.05 (br. s, 1H, OH), 7.85 (d, J = 8.8 Hz, 2H, ArHNaph), 7.68 (d, J = 8.1 Hz, 1H,
ν
ν
δ
δ
ν
ν
δ
ArHNaph), 7.53 (t, J = 2.0 Hz, 1H, ArHPhe), 7.46 (td, J = 7.6 Hz, J = 1.3 Hz, 1H, ArHNaph), 7.36–7.19 (m,
4H, ArHNaph, ArHPhe), 6.66 (ddd, J = 7.9 Hz, J = 2.2 Hz, J = 0.7 Hz, 1H, ArHPhe), 4.02 (q, J = 7.0 Hz,
2H, CH2), 1.34 (t, J = 7.0 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 165.68, 158.73, 151.55, 140.74, 131.36,
130.04, 129.34, 127.87, 127.35, 126.85, 123.35, 122.91, 118.58, 118.31, 111.53, 109.19, 105.66, 62.87, 14.60;
HR-MS: for C19H17NO3 [M + H]+ calculated 308.12812 m/z, found 308.12869 m/z.
◦
2-Hydroxy-N-(2-propoxyphenyl)naphthalene-1-carboxamide (4a). Yield 80%; Mp 125 C; IR (cm−1): 3307 (
ν
NH), 1622 ( C=O), 1537 ( NH), 1390 ( COH), 1286 ( CN), 1117 ( δ:
ν
δ
δ
ν
ν
CArCO); 1H-NMR (DMSO-d6),
10.49 (s, 1H, OH), 9.40 (s, 1H, NH), 8.20 (d, J = 9.2 Hz, 1H, ArHPhe), 8.15 (d, J = 9.2 Hz, 1H, ArHNaph),
7.88 (d, J = 8.8 Hz, 1H, ArHNaph), 7.84 (d, J = 7.0 Hz, 1H, ArHNaph), 7.48 (td, J = 7.3 Hz, J = 1.3 Hz, 1H,
ArHNaph), 7.34 (td, J = 7.9 Hz, J = 1.1Hz, 1H, ArHNaph), 7.28 (d, J = 9.2 Hz, 1H, ArHNaph), 7.16–6.95
(m, 3H, ArHPhe), 4.00 (t, J = 6.4 Hz, 2H, CH2), 1.76 (sx, J = 6.8 Hz, 2H, CH2), 0.97 (t, J = 7.3 Hz, 3H,
CH3); 13C-NMR (DMSO-d6),
δ: 165.04, 152.45, 149.03, 131.81, 131.10, 127.96, 127.75, 127.63, 126.85,
124.52, 124.11, 123.04, 121.71, 120.27, 118.23, 116.53, 112.09, 69.76, 21.98, 10.35; HR-MS: for C20H19NO3
[M + H]+ calculated 322.14377 m/z, found 322.14438 m/z.
◦
2-Hydroxy-N-(3-propoxyphenyl)naphthalene-1-carboxamide (4b). Yield 87%; Mp 125 C; IR (cm−1): 3352 (
NH), 1629 ( C=O), 1538 ( NH), 1321 ( COH), 1276 ( CN), 1182 (
CArCO); 1H-NMR (DMSO-d6),
: 10.34 (s, 1H, NH), 10.10 (br. s, 1H, OH), 7.85 (d, J = 8.8 Hz, 2H, ArHNaph), 7.68 (d, J = 8.4 Hz, 1H,
ArHNaph), 7.55 (t, J = 1.3 Hz, 1H, ArHPhe), 7.46 (td, J = 7.1 Hz, J = 1.1 Hz, 1H, ArHNaph), 7.38–7.18 (m,
ν
ν
δ
δ
ν
ν
δ

Molecules 2016, 21, 1068
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4H, ArHNaph, ArHPhe), 6.67 (dd, J = 8.1 Hz, J = 2.2 Hz, 1H, ArHPhe), 3.92 (t, J = 6.6 Hz, 2H, CH2), 1.74
(sx, J = 7.0 Hz, 2H, CH2), 0.99 (t, J = 7.3 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
: 165.69, 158.91, 151.55,
δ
140.74, 131.36, 130.04, 129.33, 127.87, 127.35, 126.87, 123.35, 122.91, 118.58, 118.31, 111.50, 109.22, 105.70,
68.83, 21.98, 10.32; HR-MS: for C20H19NO3 [M + H]+ calculated 322.14377 m/z, found 322.14420 m/z.
◦
2-Hydroxy-N-(4-propoxyphenyl)naphthalene-1-carboxamide (4c). Yield 71%; Mp 153 C; IR (cm−1): 3328 (
NH), 1627 ( C=O), 1531 ( NH), 1435 ( COH), 1236 ( CN), 1169 (
CArCO); 1H-NMR (DMSO-d6),
: 10.23 (s, 1H, NH), 10.00 (br. s, 1H, OH), 7.84 (d, J = 8.4 Hz, 2H, ArHNaph), 7.71 (d, J = 8.8 Hz, 2H,
ν
ν
δ
δ
ν
ν
δ
ArHPhe), 7.68 (d, J = 7.0 Hz, 1H, ArHNaph), 7.45 (td, J = 7.0 Hz, J = 1.1 Hz, 1H, ArHNaph), 7.32 (td,
J = 8.0 Hz, J = 2.0 Hz, 1H, ArHNaph), 7.24 (d, J = 9.2 Hz, 1H, ArHNaph), 6.92 (d, J = 8.8 Hz, 2H, ArHPhe),
3.91 (t, J = 6.6 Hz, 2H, CH2), 1.73 (sx, J = 7.0 Hz, 2H, CH2), 0.99 (t, J = 7.3 Hz, 3H, CH3); 13C-NMR
(DMSO-d6), δ: 165.07; 154.62, 151.51, 132.75, 131.45, 129.89, 127.84, 127.37, 126.76, 123.45, 122.85, 120.71,
118.69, 118.32, 114.38, 69.09, 22.02, 10.32; HR-MS: for C20H19NO3 [M + H]+ calculated 322.14377 m/z,
found 322.14429 m/z.
N-(2-Butoxyphenyl)-2-hydroxynaphthalene-1-carboxamide (5a). Yield 70%; Mp 108 ◦C; IR (cm−1): 3301 (
NH), 1621 ( C=O), 1536 ( NH), 1392 ( COH), 1287 ( CN), 1115 ( δ:
CArCO); 1H-NMR (DMSO-d6),
ν
ν
δ
δ
ν
ν
10.45 (s, 1H, OH), 9.37 (s, 1H, NH), 8.17 (d, J = 8.4 Hz, 1H, ArHPhe), 8.12 (d, J = 9.5 Hz, 1H, ArHNaph),
7.88 (d, J = 8.8 Hz, 1H, ArHNaph), 7.84 (d, J = 7.0 Hz, 1H, ArHNaph), 7.47 (td, J = 7.0 Hz, J = 1.1 Hz, 1H,
ArHNaph), 7.34 (td, J = 7.9 Hz, J = 2.0 Hz, 1H, ArHNaph), 7.27 (d, J = 9.2 Hz, 1H, ArHNaph), 7.13–6.95 (m,
3H, ArHPhe), 4.04 (t, J = 6.4 Hz, 2H, CH2), 1.73 (qi, J = 6.9 Hz, 2H, CH2), 1.42 (sx, J = 7.4 Hz, 2H, CH2),
0.88 (t, J = 7.3 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 165.04, 152.42, 149.08, 131.75, 131.05, 127.94,
127.72, 127.61, 126.82, 124.55, 124.06, 123.03, 121.77, 120.27, 118.22, 116.62, 112.10, 67.95, 30.64, 18.58,
13.57; HR-MS: for C21H21NO3 [M + H]+ calculated 336.15942 m/z, found 336.15982 m/z.
N-(3-Butoxyphenyl)-2-hydroxynaphthalene-1-carboxamide (5b). Yield 46%; Mp 118 ◦C; IR (cm−1): 3350 (
NH), 1628 ( C=O), 1537 ( NH), 1321 ( COH), 1276 ( CN), 1182 (
CArCO); 1H-NMR (DMSO-d6),
: 10.33 (s, 1H, NH), 10.10 (br. s, 1H, OH), 7.85 (d, J = 8.8 Hz, 2H, ArHNaph), 7.67 (d, J = 8.1 Hz, 1H,
ν
ν
δ
δ
ν
ν
δ
ArHNaph), 7.54 (t, J = 1.8 Hz, 1H, ArHPhe), 7.46 (td, J = 7.2 Hz, J = 1.1 Hz, 1H, ArHNaph), 7.36–7.18 (m,
4H, ArHNaph, ArHPhe), 6.69–6,65 (m, 1H, ArHPhe), 3.96 (t, J = 6.4 Hz, 2H, CH2), 1.72 (qi, J = 7.3 Hz,
2H, CH2), 1.45 (sx, J = 7.5 Hz, 2H, CH2), 0.94 (t, J = 7.3 Hz, 3H, CH3); 13C-NMR (DMSO-d6), δ: 165.68,
158.91, 151.55, 140.72, 131.36, 130.02, 129.33, 127.87, 127.34, 126.85, 123.35, 122.89, 118.57, 118.31, 111.51,
109.21, 105.67, 67.01, 30.68, 18.67, 13.60; HR-MS: for C21H21NO3 [M + H]+ calculated 336.15942 m/z,
found 336.15963 m/z.
N-(4-Butoxyphenyl)-2-hydroxynaphthalene-1-carboxamide (5c). Yield 43%; Mp 158 ◦C; IR (cm−1): 3325 (
NH), 1619 ( C=O), 1532 ( NH), 1435 ( COH), 1238 ( CN), 1170 (
CArCO); 1H-NMR (DMSO-d6),
: 10.22 (s, 1H, NH), 10.07 (br. s, 1H, OH), 7.84 (d, J = 8.8 Hz, 2H, ArHNaph), 7.71 (d, J = 9.2 Hz,
ν
ν
δ
δ
ν
ν
δ
2H, ArHPhe), 7.68 (d, J = 7.3 Hz, 1H, ArHNaph), 7.46 (td, J = 7.3 Hz, J = 1.1 Hz, 1H, ArHNaph), 7.32
(td, J = 8.1 Hz, J = 1.1 Hz, 1H, ArHNaph), 7.24 (d, J = 9.2 Hz, 1H, ArHNaph), 6.92 (d, J = 9.2 Hz, 2H,
ArHPhe), 3.95 (t, J = 6.4 Hz, 2H, CH2), 1.70 (qi, J = 6.2 Hz, 2H, CH2), 1.44 (sx, J = 6.6 Hz, 2H, CH2),
0.94 (t, J = 7.1 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 165.07, 154.63, 151.51, 132.74, 131.45, 129.89,
127.84, 127.37, 126.76, 123.45, 122.85, 120.71, 118.69, 118.32, 114.38, 67.27, 30.75, 18.67, 13.62; HR-MS: for
C21H21NO3 [M + H]+ calculated 336.15942 m/z, found 336.15990 m/z.
2-Hydroxy-N-[2-(prop-2-yloxy)phenyl]naphthalene-1-carboxamide (6a). Yield 72%; Mp 141 ◦C; IR (cm−1):
1
3397 (
(DMSO-d6),
1H, ArHNaph), 7.89 (d, J = 8.8 Hz, 1H, ArHNaph), 7.85 (d, J = 8.1 Hz, 1H, ArHNaph), 7.48 (td, J = 7.5 Hz
ν
NH), 1624 (
ν
C=O), 1533 (
δ
NH), 1396 (
δ
COH), 1285 (
ν
CN), 1115 (
ν
CArCO); H-NMR
δ
: 10.57 (s, 1H, OH), 9.42 (s, 1H, NH), 8.25 (d, J = 8.1 Hz, 1H, ArHPhe), 8.20 (d, J = 8.8 Hz,
,
J = 1.5 Hz, 1H, ArHNaph), 7.36 (td, J = 7.0 Hz, J = 0.7 Hz, 1H, ArHNaph), 7.28 (d, J = 8.8 Hz, 1H, ArHNaph),
7.11 (d, J = 4.0 Hz, 2H, ArHPhe), 6.99 (td, J = 7.9 Hz, J = 3.7 Hz, 1H, ArHPhe), 4.68 (sep, J = 6.0 Hz, 1H,
CH), 1.29 (d, J = 6.2 Hz, 6H, CH3); 13C-NMR (DMSO-d6),
δ: 164.89, 152.57, 142.50, 131.84, 131.24, 128.64,

Molecules 2016, 21, 1068
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127.96, 127.79, 126.87, 124.26, 124.24, 123.04, 121.54, 120.36, 118.22, 116.23, 113.79, 70.67, 21.75; HR-MS:
for C20H19NO3 [M + H]+ calculated 322.14377 m/z, found 322.14432 m/z.
2-Hydroxy-N-[3-(prop-2-yloxy)phenyl]naphthalene-1-carboxamide (6b). Yield 44%; Mp 102 ◦C; IR (cm−1):
1
3352 (
ν
NH), 1628 (
ν
C=O), 1527 (
δ
NH), 1319 (
δ
COH), 1276 (
ν
CN), 1184 (
ν
CArCO); H-NMR
(DMSO-d6),
δ: 10.33 (s, 1H, NH), 10.11 (br. s, 1H, OH), 7.85 (d, J = 9.2 Hz, 2H, ArHNaph), 7.67 (d,
J = 8.0 Hz, 1H, ArHNaph), 7.49 (s, 1H, ArHPhe), 7.46 (td, J = 6.8 Hz, J = 1.7 Hz, 1H, ArHNaph), 7.36–7.17
(m, 4H, ArHNaph, ArHPhe), 6.65 (ddd, J = 8.1 Hz, J = 2.6 Hz, J = 1.6 Hz, 1H, ArHPhe), 4.57 (sep, J = 6.1 Hz,
1H, CH), 1.28 (d, J = 6.2 Hz, 6H, CH3); 13C-NMR (DMSO-d6),
δ: 165.71, 157.70, 151.61, 140.81, 131.39,
130.08, 129.40, 127.91, 127.37, 126.91, 123.39, 122.94, 118.58, 118.36, 111.45, 110.33, 106.85, 69.13, 21.84;
HR-MS: for C20H19NO3 [M + H]+ calculated 322.14377 m/z, found 322.14438 m/z.
2-Hydroxy-N-[4-(prop-2-yloxy)phenyl]naphthalene-1-carboxamide (6c). Yield 75%; Mp 133 ◦C; IR (cm−1):
1
3265 (
ν
NH), 1625 (
ν
C=O), 1534 (
δ
NH), 1435 (
δ
COH), 1236 (
ν
CN), 1179 (
ν
CArCO); H-NMR
(DMSO-d6),
δ: 10.22 (s, 1H, NH), 10.08 (br. s, 1H, OH), 7.84 (d, J = 8.8 Hz, 2H, ArHNaph), 7.70 (d,
J = 8.8 Hz, 2H, ArHPhe), 7.69 (d, J = 9.2 Hz, 1H, ArHNaph), 7.46 (td, J = 7.5 Hz, J = 1.1 Hz, 1H, ArHNaph),
7.32 (td, J = 7.3 Hz, J = 2.0 Hz, 1H, ArHNaph), 7.24 (d, J = 9.2 Hz, 1H, ArHNaph), 6.91 (d, J = 9.2 Hz, 2H,
ArHPhe), 4.57 (sep, J = 6.0 Hz, 1H, CH), 1.26 (d, J = 5.9 Hz, 6H, CH3); 13C-NMR (DMSO-d6),
δ: 165.06,
153.28, 151.49, 132.72, 131.43, 129.86, 127.81, 127.35, 126.75, 123.44, 122.83, 120.72, 118.69, 118.31, 115.84,
69.38, 21.78; HR-MS: for C20H19NO3 [M + H]+ calculated 322.14377 m/z, found 322.14426 m/z.
◦
N-[2-(But-2-yloxy)phenyl]-2-hydroxynaphthalene-1-carboxamide (7a). Yield 60%; Mp 48 C; IR (cm−1): 3398
NH), 1624 ( C=O), 1521 ( NH), 1396 ( COH), 1285 ( CN), 1112 (
CArCO); 1H-NMR (DMSO-d6),
: 10.56 (s, 1H, OH), 9.40 (s, 1H, NH), 8.26 (d, J = 8.1 Hz, 1H, ArHPhe), 8.19 (d, J = 8.4 Hz, 1H, ArHNaph),
(ν
ν
δ
δ
ν
ν
δ
7.89 (d, J = 9.2 Hz, 1H, ArHNaph), 7.84 (d, J = 8.1 Hz, 1H, ArHNaph), 7.48 (td, J = 7.9 Hz, J = 1.5 Hz,
1H, ArHNaph), 7.34 (td, J = 8.1 Hz, J = 1.1 Hz, 1H, ArHNaph), 7.27 (d, J = 8.8 Hz, 1H, ArHNaph), 7.10
(d, J = 4.0 Hz, 2H, ArHPhe), 6.98 (td, J = 8.2 Hz, J = 4.0 Hz, 1H, ArHPhe), 4.87 (sx, J = 6.0 Hz, 1H, CH),
1.70-1.56 (m, 2H, CH2), 1.24 (d, J = 6.2 Hz, 3H, CH3), 0.91 (t, J = 7.3 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ
: 164.94, 152.66, 147.72, 131.90, 131.31, 128.55, 128.02, 127.81, 126.91, 124.33, 124.23, 123.10, 121.54,
120.27, 118.28, 116.25, 113.47, 75.35, 28.50, 18.99, 9.47; HR-MS: for C21H21NO3 [M + H]+ calculated
336.15942 m/z, found 336.15982 m/z.
◦
N-[3-(But-2-yloxy)phenyl]-2-hydroxynaphthalene-1-carboxamide (7b). Yield 45%; Mp 85 C; IR (cm−1):
1
3284 (
(DMSO-d6),
1H, ArHNaph), 7.50 (t, J = 2.2 Hz, 1H, ArHPhe), 7.46 (td, J = 7.7 Hz, J = 1.5 Hz, 1H, ArHNaph), 7.36–7.17
ν
NH), 1627 (
ν
C=O), 1529 (
δ
NH), 1434 (
δ
COH), 1275 (
ν
CN), 1155 (
ν
CArCO); H-NMR
δ
: 10.33 (s, 1H, NH), 10.10 (s, 1H, OH), 7.85 (d, J = 9.2 Hz, 2H, ArHNaph), 7.68 (d, J = 8.4 Hz,
(m, 4H, ArHNaph, ArHPhe), 6.65 (ddd, J = 8.1 Hz, J = 1.1 Hz, J = 0.9 Hz, 1H, ArHPhe), 4.33 (sx, J = 6.0 Hz
,
1H, CH), 1.72-1.48 (m, 2H, CH2), 1.25 (d, J = 5.9 Hz, 3H, CH3), 0.94 (t, J = 7.3 Hz, 3H, CH3); 13C-NMR
(DMSO-d6), δ: 165.74, 158.06, 151.63, 140.84, 131.40, 130.10, 129.43, 127.93, 127.37, 126.93, 123.41,
122.97, 118.60, 118.37, 111.41, 110.36, 106.79, 74.14, 28.58, 19.09, 9.56; HR-MS: for C21H21NO3 [M + H]+
calculated 336.15942 m/z, found 336.15972 m/z.
N-[4-(But-2-yloxy)phenyl]-2-hydroxynaphthalene-1-carboxamide (7c). Yield 45%; Mp 139 ◦C; IR (cm−1):
1
3257 (
ν
NH), 1621 (
ν
C=O), 1505 (
δ
NH), 1401 (
δ
COH), 1232 (
ν
CN), 1136 (
ν
CArCO); H-NMR
(DMSO-d6),
δ: 10.23 (s, 1H, NH), 10.07 (s, 1H, OH), 7.84 (d, J = 8.8 Hz, 2H, ArHNaph), 7.70 (d, J = 9.2 Hz,
2H, ArHPhe), 7.69 (d, J = 7.0 Hz, 1H, ArHNaph), 7.46 (td, J = 7.0 Hz, J = 1.1 Hz, 1H, ArHNaph), 7.32 (td,
J = 7.5 Hz, J = 2.0 Hz, 1H, ArHNaph), 7.24 (d, J = 8.8 Hz, 1H, ArHNaph), 6.91 (d, J = 8.8 Hz, 2H, ArHPhe),
4.34 (sx, J = 5.9 Hz, 1H, CH), 1.72–1.48 (m, 2H, CH2), 1.22 (d, J = 5.9 Hz, 3H, CH3), 0.93 (t, J = 7.3 Hz,
3H, CH3); 13C-NMR (DMSO-d6),
δ: 165.13, 153.68, 151.57, 132.77, 131.49, 129.96, 127.91, 127.40, 126.84,
123.50, 122.92, 120.78, 118.73, 118.37, 115.90, 74.43, 28.53, 19.05, 9.50; HR-MS: for C21H21NO3 [M + H]+
calculated 336.15942 m/z, found 336.15974 m/z.

Molecules 2016, 21, 1068
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1-Hydroxy-N-phenylnaphthalene-2-carboxamide (8, CAS 13545-65-8), 1-hydroxy-N-(2-methoxyphenyl)naphtha-
lene-2-carboxamide (9a, CAS 26675-52-5), 1-hydroxy-N-(3-methoxyphenyl)naphthalene-2-carboxamide (9b
,
CAS 110677-79-7) and 1-hydroxy-N-(4-methoxyphenyl)naphthalene-2-carboxamide (9c, CAS 98621-48-8)
were synthesized and characterized recently [11].
N-(2-Ethoxyphenyl)-1-hydroxynaphthalene-2-carboxamide (10a, CAS 26639-37-2). Yield 55%; Mp 139 ◦C
(140–142 ◦C) [41]; IR (cm−1): 3424 (
ν
NH), 1621 (
ν C=O), 1538 (δ NH), 1388 (δ COH), 1288 (ν CN),
1117 (
ν
CArCO); 1H-NMR (DMSO-d6),
δ: 13.75 (s, 1H, OH), 10.27 (s, 1H, NH), 8.32 (d, J = 8.2 Hz, 1H,
ArHNaph), 8.07 (d, J = 8.8 Hz, 1H, ArHNaph), 7.91 (d, J = 8.1 Hz, 1H, ArHNaph), 7.73 (dd, J = 7.8 Hz,
J = 1.2 Hz, 1H, ArHPhe), 7.70–7.62 (m, 1H, ArHNaph), 7.62–7.54 (m, 1H, ArHNaph), 7.47 (d, J = 8.8 Hz,
1H, ArHNaph), 7.27–7.18 (m, 1H, ArHPhe), 7.15–7.08 (m, 1H, ArHPhe), 7.00 (t, J = 7.6 Hz, 1H, ArHPhe),
4.11 (q, J = 6.9 Hz, 2H, CH2), 1.34 (t, J = 6.9 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 168.30, 158.61,
151.43, 135.91, 128.82, 127.50, 126.49, 126.08, 125.82, 125.26, 124.85, 123.41, 123.04, 120.27, 118.32, 112.73,
108.78, 63.96, 14.57; HR-MS: for C19H17NO3 [M + H]+ calculated 308.12812 m/z, found 308.12875 m/z.
◦
N-(3-Ethoxyphenyl)-1-hydroxynaphthalene-2-carboxamide (10b). Yield 86%; Mp 130 C; IR (cm−1): 3436 (
NH), 1624 ( C=O), 1532 ( NH), 1387 ( COH), 1293 ( CN), 1174 (
CArCO); 1H-NMR (DMSO-d6),
: 14.00 (br. s, 1H, OH), 10.41 (s, 1H, NH), 8.31 (d, J = 8.3 Hz, 1H, ArHNaph), 8.12 (d, J = 9.0 Hz, 1H,
ν
ν
δ
δ
ν
ν
δ
ArHNaph), 7.92 (d, J = 7.9 Hz, 1H, ArHNaph), 7.67 (ddd, J = 8.1 Hz, J = 6.9 Hz, J = 1.3 Hz, 1H, ArHNaph),
7.62–7.54 (m, 1H, ArHNaph), 7.47 (d, J = 8.8 Hz, 1H, ArHNaph), 7.41–7.33 (m, 2H, ArHPhe), 7.32–7.26 (m,
1H, ArHPhe), 6.76 (ddd, J = 7.8 Hz, J = 2.4 Hz, J = 1.5 Hz, 1H, ArHPhe), 4.04 (q, J = 7.0 Hz, 2H, CH2),
1.35 (t, J = 7.0 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 169.41, 159.88, 158.62, 138.73, 135.94, 129.36,
129.07, 127.41, 125.85, 124.62, 123.00, 123.00, 117.73, 114.01, 110.77, 108.20, 107.55, 63.02, 14.57; HR-MS:
for C19H17NO3 [M + H]+ calculated 308.12812 m/z, found 308.12851 m/z.
N-(4-Ethoxyphenyl)-1-hydroxynaphthalene-2-carboxamide (10c, CAS 109883-65-0). Yield 56%; Mp 152 ◦C
(154–155 ◦C) [41]; IR (cm−1): 3436 (
ν
NH), 1621 (
CArCO); 1H-NMR (DMSO-d6),
: 14.21 (br. s, 1H, OH), 10.39 (s, 1H, NH), 8.30 (d, J = 8.3 Hz,
1H, ArHNaph), 8.11 (d, J = 9.0 Hz, 1H, ArHNaph), 7.91 (d, J = 8.1 Hz, 1H, ArHNaph), 7.71–7.52 (m, 4H,
ArHNaph, ArHPhe), 7.45 (d, J = 9.0 Hz, 1H, ArHNaph), 6.96 (d, J = 9.0 Hz, 2H, ArHPhe), 4.03 (q, J = 6.9 Hz
2H, CH2), 1.33 (t, J = 7.0 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
: 170.62, 161.37, 157.15, 137.35, 131.73,
ν C=O), 1536 (δ NH), 1389 (δ COH), 1299 (ν CN),
1146 (
ν
δ
,
δ
130.43, 128.90, 127.27, 126.15, 125.30, 124.48, 124.40, 119.14, 115.79, 108.90, 64.60, 16.07; HR-MS: for
C19H17NO3 [M + H]+ calculated 308.12812 m/z, found 308.12869 m/z.
1-Hydroxy-N-(2-propoxyphenyl)naphthalene-2-carboxamide (11a). Yield 55%; Mp 108 ◦C; IR (cm−1): 3440
(ν
NH), 1625 (
ν C=O), 1537 (δ NH), 1390 (δ COH), 1240 (ν CN), 1110 (ν
CArCO); 1H-NMR (DMSO-d6),
δ
: 13.83 (br. s, 1H, OH), 10.26 (s, 1H, NH), 8.35–8.28 (m, 1H, ArHNaph), 8.06 (d, J = 8.8 Hz, 1H, ArHNaph),
7.91 (d, J = 7.7 Hz, 1H, ArHNaph), 7.74–7.55 (m, 3H, ArHNaph, ArHPhe), 7.47 (d, J = 8.8 Hz, 1H, ArHNaph),
7.28–7.20 (m, 1H, ArHPhe), 7.15–7.09 (m, 1H, ArHPhe), 7.00 (td, J = 7.6 Hz, J = 1.4 Hz, 1H, ArHPhe),
4.00 (t, J = 6.4 Hz, 2H, CH2), 1.74 (sx, J = 7.0 Hz, 2H, CH2), 0.95 (t, J = 7.4 Hz, 3H, CH3); 13C-NMR
(DMSO-d6), δ: 168.49, 158.78, 151.86, 135.90, 128.84, 128.49, 126.68, 125.97, 125.80, 125.56, 124.80, 123.26,
123.03, 120.22, 118.25, 112.70, 108.53, 69.66, 22.01, 10.25; HR-MS: for C20H19NO3 [M + H]+ calculated
322.14377 m/z, found 322.14432 m/z.
◦
1-Hydroxy-N-(3-propoxyphenyl)naphthalene-2-carboxamide (11b). Yield 58%; Mp 95 C; IR (cm−1): 3436 (
ν
NH), 1627 ( C=O), 1533 ( NH), 1330 ( COH), 1292 ( CN), 1173 ( δ:
ν
δ
δ
ν
ν
CArCO); 1H-NMR (DMSO-d6),
14.00 (s, 1H, OH), 10.40 (s, 1H, NH), 8.31 (d, J = 8.2 Hz, 1H, ArHNaph), 8.12 (d, J = 9.0 Hz, 1H, ArHNaph),
7.92 (d, J = 8.1 Hz, 1H, ArHNaph), 7.67 (ddd, J = 8.1 Hz, J = 6.9 Hz, J = 1.3 Hz, 1H, ArHNaph), 7.62–7.54
(m, 1H, ArHNaph), 7.47 (d, J = 8.8 Hz, 1H, ArHNaph), 7.42–7.33 (m, 2H, ArHPhe), 7.33–7.25 (m, 1H,
ArHPhe), 6.80–6.73 (m, 1H, ArHPhe), 3.94 (t, J = 6.5 Hz, 2H, CH2), 1.75 (sx, J = 7.0 Hz, 2H, CH2), 0.99
(t, J = 7.3 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 169.41, 159.88, 158.81, 138.73, 135.94, 129.36, 129.05,
127.41, 125.85, 124.62, 123.00, 123.00, 117.73, 114.00, 110.78, 108.23, 107.55, 68.97, 21.96, 10.31; HR-MS:
for C20H19NO3 [M + H]+ calculated 322.14377 m/z, found 322.14426 m/z.

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1-Hydroxy-N-(4-propoxyphenyl)naphthalene-2-carboxamide (11c). Yield 65%; Mp 127 ◦C; IR (cm−1): 3415
NH), 1622 ( C=O), 1536 ( NH), 1389 ( COH), 1297 ( CN), 1151 (
CArCO); 1H-NMR (DMSO-d6),
: 14.21 (br. s, 1H, OH), 10.39 (s, 1H, NH), 8.30 (d, J = 8.4 Hz, 1H, ArHNaph), 8.11 (d, J = 9.0 Hz, 1H,
(ν
ν
δ
δ
ν
ν
δ
ArHNaph), 7.91 (d, J = 7.9 Hz, 1H, ArHNaph), 7.70–7.54 (m, 4H, ArHNaph, ArHPhe), 7.45 (d, J = 8.8 Hz,
1H, ArHNaph), 7.01–6.93 (m, 2H, ArHPhe), 3.93 (t, J = 6.5 Hz, 2H, CH2), 1.73 (sx, J = 7.1 Hz, 2H, CH2),
0.98 (t, J = 7.4 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 169.09, 159.85, 155.80, 135.83, 130.22, 129.92,
127.37, 125.76, 124.64, 123.77, 122.95, 122.88, 117.61, 114.32, 107.38, 69.06, 21.96, 10.28; HR-MS: for
C20H19NO3 [M + H]+ calculated 322.14377 m/z, found 322.14419 m/z.
◦
N-(2-Butoxyphenyl)-1-hydroxynaphthalene-2-carboxamide (12a). Yield 61%; Mp 112 C; IR (cm−1): 3443 (
NH), 1626 ( C=O), 1538 ( NH), 1390 ( COH), 1253 ( CN), 1111 (
CArCO); 1H-NMR (DMSO-d6),
: 13.82 (s, 1H, OH), 10.23 (s, 1H, NH), 8.31 (d, J = 8.2 Hz, 1H, ArHNaph), 8.05 (d, J = 9.0 Hz, 1H,
ν
ν
δ
δ
ν
ν
δ
ArHNaph), 7.92 (d, J = 7.9 Hz, 1H, ArHNaph), 7.73–7.63 (m, 2H, ArHNaph, ArHPhe), 7.62–7.55 (m, 1H,
ArHNaph), 7.47 (d, J = 8.8 Hz, 1H, ArHNaph), 7.28–7.20 (m, 1H, ArHPhe), 7.15–7.09 (m, 1H, ArHPhe),
7.00 (td, J = 7.6 Hz, J = 1.1 Hz, 1H, ArHPhe), 4.04 (t, J = 6.3 Hz, 2H, CH2), 1.70 (qi, J = 7.3 Hz, 2H, CH2),
1.41 (sx, J = 7.4 Hz, 2H, CH2), 0.86 (t, J = 7.3 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 168.50, 158.79,
151.86, 135.88, 128.81, 127.47, 126.67, 125.99, 125.79, 125.53, 124.82, 123.23, 123.01, 120.21, 118.20, 112.67,
108.52, 67.87, 30.64, 18.53, 13.52; HR-MS: for C21H21NO3 [M + H]+ calculated 336.15942 m/z, found
336.15994 m/z.
◦
N-(3-Butoxyphenyl)-1-hydroxynaphthalene-2-carboxamide (12b). Yield 58%; Mp 107 C; IR (cm−1): 3288 (
ν
NH), 1633 ( C=O), 1527 ( NH), 1389 ( COH), 1291 ( CN), 1170 ( δ:
ν
δ
δ
ν
ν
CArCO); 1H-NMR (DMSO-d6),
14.00 (s, 1H, OH), 10.40 (s, 1H, NH), 8.31 (dt, J = 8.2 Hz, J = 0.6 Hz, 1H, ArHNaph), 8.12 (d, J = 8.8 Hz, 1H,
ArHNaph), 7.92 (d, J = 7.9 Hz, 1H, ArHNaph), 7.71–7.63 (m, 1H, ArHNaph), 7.62–7.54 (m, 1H, ArHNaph),
7.47 (d, J = 8.8 Hz, 1H, ArHNaph), 7.42–7.33 (m, 2H, ArHPhe), 7.32–7.25 (m, 1H, ArHPhe), 6.76 (ddd,
J = 7.9 Hz, J = 2.5 Hz, J = 1.3 Hz, 1H, ArHPhe), 3.98 (t, J = 6.5 Hz, 2H, CH2), 1.72 (qi, J = 7.3 Hz, 2H,
CH2), 1.45 (sx, J = 7.4 Hz, 2H, CH2), 0.94 (t, J = 7.5 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 169.34,
159.88, 158.81, 138.72, 135.94, 129.34, 129.05, 127.41, 125.84, 124.62, 123.00, 123.00, 117.73, 114.00, 110.77,
108.23, 107.54, 67.15, 30.67, 18.67, 13.60; HR-MS: for C21H21NO3 [M+H]+ calculated 336.15942 m/z,
found 336.15990 m/z.
◦
N-(4-Butoxyphenyl)-1-hydroxynaphthalene-2-carboxamide (12c). Yield 57%; Mp 124 C; IR (cm−1): 3328 (
NH), 1633 ( C=O), 1532 ( NH), 1391 ( COH), 1296 ( CN), 1149 (
CArCO); 1H-NMR (DMSO-d6),
: 14.22 (br. s, 1H, OH), 10.39 (s, 1H, NH), 8.30 (d, J = 8.2 Hz, 1H, ArHNaph), 8.11 (d, J = 9.0 Hz, 1H,
ν
ν
δ
δ
ν
ν
δ
ArHNaph), 7.91 (d, J = 7.9 Hz, 1H, ArHNaph), 7.71–7.53 (m, 4H, ArHNaph, ArHPhe), 7.45 (d, J = 8.8 Hz,
1H, ArHNaph), 6.97 (d, J = 9.0 Hz, 2H, ArHPhe), 3.97 (t, J = 6.4 Hz, 2H, CH2), 1.70 (qi, J = 7.3 Hz, 2H,
CH2), 1.44 (sx, J = 7.4 Hz, 2H, CH2), 0.94 (t, J = 7.4 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ: 169.11, 159.87,
155.82, 135.85, 130.22, 128.93, 127.38, 125.77, 124.65, 123.77, 122.97, 122.98, 117.63, 114.32, 107.40, 67.27,
30.70, 18.65, 13.58; HR-MS: for C21H21NO3 [M + H]+ calculated 336.15942 m/z, found 336.15973 m/z.
1-Hydroxy-N-[2-(prop-2-yloxy)phenyl]naphthalene-2-carboxamide (13a). Yield 49%; Mp 123 ◦C; IR (cm−1):
1
3425 (
ν
NH), 1629 (
ν
C=O), 1538 (
δ
NH), 1391 (
δ
COH), 1289 (
ν
CN), 1115 (
ν
CArCO); H-NMR
(DMSO-d6),
δ: 13.59 (s, 1H, OH), 10.27 (s, 1H, NH), 8.33 (d, J = 8.4 Hz, 1H, ArHNaph), 8.06 (d, J = 9.0 Hz,
1H, ArHNaph), 7.92 (d, J = 7.9 Hz, 1H, ArHNaph), 7.81 (dd, J = 7.9 Hz, J = 1.5 Hz, 1H, ArHPhe), 7.67 (td,
J = 7.4 Hz, J = 1.5 Hz, 1H, ArHNaph), 7.63–7.55 (m, 1H, ArHNaph), 7.49 (d, J = 8.8 Hz, 1H, ArHNaph),
7.24–7.11 (m, 1H, ArHPhe), 7.16–7.11 (m, 1H, ArHPhe), 6.99 (td, J = 7.6 Hz, J = 1.6 Hz, 1H, ArHPhe), 4.63
(sep, J = 6.0 Hz, 1H, CH), 1.30 (d, J = 6.0 Hz, 6H, CH3); 13C-NMR (DMSO-d6),
δ: 167.94, 158.23, 150.13,
135.90, 128.76, 127.50, 127.20, 126.18, 125.79, 124.94, 124.86, 123.48, 123.04, 120.37, 118.46, 114.46, 109.16,
70.94, 21.82; HR-MS: for C20H19NO3 [M + H]+ calculated 322.14377 m/z, found 322.14430 m/z.
1-Hydroxy-N-[3-(prop-2-yloxy)phenyl]naphthalene-2-carboxamide (13b). Yield 77%; Mp 154 ◦C; IR (cm−1):
1
3301 (
ν
NH), 1633 (
ν
C=O), 1530 (
δ
NH), 1379 (
δ
COH), 1298 (
ν
CN), 1156 (
ν
CArCO); H-NMR
(DMSO-d6),
δ: 14.00 (s, 1H, OH), 10.39 (s, 1H, NH), 8.31 (d, J = 7.9 Hz, 1H, ArHNaph), 8.12 (d, J = 9.0 Hz,

Molecules 2016, 21, 1068
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1H, ArHNaph), 7.92 (d, J = 7.9 Hz, 1H, ArHNaph), 7.67 (ddd, J = 8.1 Hz, J = 6.9 Hz, J = 1.5 Hz, 1H,
ArHNaph), 7.62–7.55 (m, 1H, ArHNaph), 7.47 (d, J = 9.0 Hz, 1H, ArHNaph), 7.39–7.25 (m, 3H, ArHPhe),
6.77–6.72 (m, 1H, ArHPhe), 4.60 (sep, J = 6.0 Hz, 1H, CH), 1.30 (d, J = 6.0 Hz, 6H, CH3); 13C-NMR
(DMSO-d6), δ: 169.40, 159.87, 157.58, 138.75, 135.93, 129.36, 129.05, 127.41, 125.85, 124.62, 123.00,
123.00, 117.71, 113.94, 111.97, 109.39, 107.51, 69.30, 21.78; HR-MS: for C20H19NO3 [M + H]+ calculated
322.14377 m/z, found 322.14438 m/z.
1-Hydroxy-N-[4-(prop-2-yloxy)phenyl]naphthalene-2-carboxamide (13c). Yield 66%; Mp 173 ◦C; IR (cm−1):
1
3360 (
(DMSO-d6),
1H, ArHNaph), 7.91 (d, J = 8.1 Hz, 1H, ArHNaph), 7.71–7.53 (m, 4H, ArHNaph, ArHPhe), 7.45 (d, J = 8.8 Hz
ν
NH), 1623 (
ν
C=O), 1528 (
δ
NH), 1379 (
δ
COH), 1300 (
ν
CN), 1157 (
ν
CArCO); H-NMR
δ: 14.22 (s, 1H, OH), 10.38 (s, 1H, NH), 8.30 (d, J = 8.1 Hz, 1H, ArHNaph), 8.11 (d, J = 8.8 Hz
,
,
1H, ArHNaph), 6.95 (d, J = 9.0 Hz, 2H, ArHPhe), 4.59 (sep, J = 6.0 Hz, 1H, CH), 1.27 (d, J = 6.0 Hz, 6H,
CH3); 13C-NMR (DMSO-d6),
δ: 169.11, 159.85, 154.56, 135.85, 130.16, 128.93, 127.38, 125.79, 124.65,
123.83, 122.97, 122.89, 117.64, 115.61, 107.40, 69.38, 21.76; HR-MS: for C20H19NO3 [M + H]+ calculated
322.14377 m/z, found 322.14422 m/z.
N-[2-(But-2-yloxy)phenyl]-1-hydroxynaphthalene-2-carboxamide (14a). Yield 56%; Mp 60 ◦C; IR (cm−1):
1
3418 (
ν
NH), 1627 (
ν
C=O), 1540 (
δ
NH), 1389 (
δ
COH), 1289 (
ν
CN), 1112 (
ν
CArCO); H-NMR
(DMSO-d6),
δ
: 13.66 (s, 1H, OH), 10.26 (s, 1H, NH), 8.35–8.29 (m, 1H, ArHNaph), 8.05 (d, J = 9.0 Hz, 1H,
ArHNaph), 7.92 (d, J = 7.5 Hz, 1H, ArHNaph), 7.77 (dd, J = 7.9 Hz, J = 1.5 Hz, 1H, ArHPhe), 7.70–7.63 (m,
1H, ArHNaph), 7.62–7.55 (m, 1H, ArHNaph), 7.48 (d, J = 8.6 Hz, 1H, ArHNaph), 7.25–7.18 (m, 1H, ArHPhe),
7.15–7.09 (m, 1H, ArHPhe), 6.98 (td, J = 7.6 Hz, J = 1.5 Hz, 1H, ArHPhe), 4.43 (sx, J = 6.0 Hz, 1H, CH),
1.76–1.51 (m, 2H, CH2), 1.25 (d, J = 6.0 Hz, 3H, CH3), 0.90 (t, J = 7.4 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ
: 168.09, 158.40, 150.52, 135.88, 128.76, 127.49, 127.08, 126.32, 125.77, 125.21, 124.85, 123.39, 123.04,
120.25, 118.37, 114.29, 108.98, 75.54, 28.53, 18.85, 9.22; HR-MS: for C21H21NO3 [M + H]+ calculated
336.15942 m/z, found 336.15982 m/z.
N-[3-(But-2-yloxy)phenyl]-1-hydroxynaphthalene-2-carboxamide (14b). Yield 59%; Mp 97 ◦C; IR (cm−1):
1
3324 (
ν
NH), 1602 (
ν
C=O), 1526 (
δ
NH), 1329 (
δ
COH), 1296 (
ν
CN), 1153 (
ν
CArCO); H-NMR
(DMSO-d6),
δ
: 14.00 (s, 1H, OH), 10.38 (s, 1H, NH), 8.35–8.28 (m, 1H, ArHNaph), 8.12 (d, J = 9.0 Hz, 1H,
ArHNaph), 7.92 (d, J = 7.9 Hz, 1H, ArHNaph), 7.67 (ddd, J = 8.1 Hz, J = 6.8 Hz, J = 1.4 Hz, 1H, ArHNaph),
7.62–7.54 (m, 1H, ArHNaph), 7.47 (d, J = 9.0 Hz, 1H, ArHNaph), 7.40–7.31 (m, 2H, ArHPhe), 7.31–7.24 (m
1H, ArHPhe), 6.75 (ddd, J = 7.8 Hz, J = 2.4 Hz, J = 1.3 Hz, 1H, ArHPhe), 4.38 (sx, J = 6.0 Hz, 1H, CH),
1.77-1.52 (m, 2H, CH2), 1.26 (d, J = 6.0 Hz, 3H, CH3), 0.94 (t, J = 7.4 Hz, 3H, CH3); 13C-NMR (DMSO-d6),
δ
: 169.40, 159.88, 157.93, 138.78, 135.93, 129.37, 129.05, 127.41, 125.84, 124.62, 123.00, 123.00, 117.72,
113.94, 111.97, 109.40, 107.55, 74.28, 28.52, 18.99, 9.44; HR-MS: for C21H21NO3 [M + H]+ calculated
336.15942 m/z, found 336.15980 m/z.
N-[4-(But-2-yloxy)phenyl]-1-hydroxynaphthalene-2-carboxamide (14c). Yield 59%; Mp 149 ◦C; IR (cm−1):
1
3359 (
ν
NH), 1623 (
ν
C=O), 1525 (
δ
NH), 1386 (
δ
COH), 1302 (
ν
CN), 1158 (
ν
CArCO); H-NMR
(DMSO-d6),
δ
: 14.22 (s, 1H, OH), 10.38 (s, 1H, NH), 8.34–8.26 (m, 1H, ArHNaph), 8.11 (d, J = 9.0 Hz, 1H,
ArHNaph), 7.91 (d, J = 7.9 Hz, 1H, ArHNaph), 7.66 (ddd, J = 8.1 Hz, J = 6.9 Hz, J = 1.5 Hz, 1H, ArHNaph),
7.63–7.53 (m, 3H, ArHNaph, ArHPhe), 7.45 (d, J = 8.8 Hz, 1H, ArHNaph), 6.99–6.91 (m, 2H, ArHPhe),
4.37 (sx, J = 6.0 Hz, 1H, CH), 1.75–1.49 (m, 2H, CH2), 1.23 (d, J = 6.0 Hz, 3H, CH3), 0.93 (t, J = 7.4 Hz,
3H, CH3); 13C-NMR (DMSO-d6),
δ: 169.11, 159.87, 154.91, 135.85, 130.14, 128.93, 127.38, 125.77, 124.65,
123.85, 122.97, 122.89, 117.63, 115.64, 107.40, 74.37, 28.48, 18.97, 9.41; HR-MS: for C21H21NO3 [M + H]+
calculated 336.15942 m/z, found 336.15990 m/z.
3.3. In Vitro Antimycobacterial Evaluation
Mycobacterium tuberculosis H37Ra ATCC 25177 was grown in Middlebrook broth (MB),
supplemented with Oleic-Albumin-Dextrose-Catalase (OADC) supplement (Becton, Dickinson &
Comp., Franklin Lakes, NJ, USA) and mycobactin J (2 µg/mL). At log phase growth, a culture sample

Molecules 2016, 21, 1068
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(10 mL) was centrifuged at 15,000 rpm/20 min using a bench top centrifuge (Model CR 4-12, Jouan
Inc., Winchester, VA, USA). Following the removal of the supernatant, the pellet was washed in fresh
Middlebrook 7H9GC broth and re-suspended in fresh, ODAC-supplemented MB (10 mL). The turbidity
was adjusted to match McFarland standard No. 1 (3
of the culture was then performed in MB broth. The antimicrobial susceptibility of M. tuberculosis
was investigated in a 96-well plate format. In these experiments, sterile deionised water (300 L)
was added to all outer-perimeter wells of the plates to minimize evaporation of the medium in the
test wells during incubation. Each evaluated compound (100 L) was incubated with M. tuberculosis
(100 L). Dilutions of each compound were prepared in duplicate. For all synthesized compounds,
final concentrations ranged from 1000 g/mL to 8 g/mL. All compounds were dissolved in DMSO,
×
108 cfu) with MB broth. A further 1:20 dilution
µ
µ
µ
µ
µ
and subsequent dilutions were made in supplemented MB. The plates were sealed with parafilm and
◦
incubated at 37 C for 7 days. Following incubation, a 10% addition of alamarBlue (AbD Serotec,
Kidlington, UK) was mixed into each well, and readings at 570 nm and 600 nm were taken, initially
for background subtraction and subsequently after 24 h re-incubation. The background subtraction is
necessary for strongly coloured compounds, where the colour may interfere with the interpretation of
any colour change. For non-interfering compounds, a blue colour in the well was interpreted as the
absence of growth, and a pink colour was scored as growth.
The evaluation of the in vitro antimycobacterial activity of the compounds was additionally
performed against Mycobacterium kansasii DSM 44162 and M. smegmatis ATCC 700084. The broth
dilution micro-method in Middlebrook 7H9 medium (Difco, Lawrence, KS, USA) supplemented with
ADC Enrichment (Becton, Dickinson & Comp.) was used to determine the minimum inhibitory
concentration (MIC) as previously described [42]. The compounds were dissolved in DMSO
(Sigma-Aldrich), and the final concentration of DMSO did not exceed 2.5% of the total solution
composition. The final concentrations of the evaluated compounds ranging from 256
µg/mL to
0.125 g/mL were obtained by twofold serial dilution of the stock solution in microtiter plate with
µ
sterile medium. Bacterial inocula were prepared by transferring colonies from culture to sterile water.
The cell density was adjusted to 0.5 McFarland units using a densitometer (Densi-La-Meter, LIAP,
Riga, Latvia). The final inoculum was made by 1:1000 dilution of the suspension with sterile water.
Drug-free controls, sterility controls and controls consisted of medium and DMSO alone were included.
The determination of results was performed visually after 3 days of static incubation in the darkness at
◦
37 C in an aerobic atmosphere for M. smegmatis and after 7 days of static incubation in the darkness at
37 ◦C in an aerobic atmosphere for M. kansasii.
The minimum inhibitory concentration (MIC) was defined as the lowest concentration of the
compound at which no visible bacterial growth was observed, i.e., the MIC is the lowest concentration
that prevented a visual colour change from blue to pink. MIC is defined for mycobacteria as 90% or
greater (IC90) reduction of growth in comparison with the control. The MIC/IC90 value is routinely
and widely used in bacterial assays and is a standard detection limit according to the Clinical and
Laboratory Standards Institute (CLSI, www.clsi.org). Rifampicin and isoniazid (Sigma-Aldrich) were
used as the standards as they are clinically used antimycobacterial drugs. The results are summarized
in Table 1.
3.4. MTT Assay
For the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the outer wells
of a 96-well plate were filled with 200 µL of sterile water, and the inner wells were filled with 100 µL
of the tested compound at the MIC to be examined. Compounds were prepared as previously stated
and diluted in Middlebrook media to achieve the desired concentration. Mycobacterium tuberculosis
H37Ra ATCC 25177 was suspended in ODAC supplemented Middlebrook broth at a MacFarland
standard of 1.0 and then diluted 1:20, using Middlebrook broth as a diluent. The diluted mycobacteria
(100
µL) were added to each well containing the compound to be tested. A negative growth control
was composed of 100
µ
L of DMSO and 100 L of the media, and the diluted mycobacteria in broth
µ

Molecules 2016, 21, 1068
15 of 18
absent of inhibiting compounds were used as a positive growth control. All compounds and controls
◦
were prepared in triplicate. Plates were incubated at 37 C for 7 days. After the incubation period, 10%
well volume of MTT reagent was mixed into each well and incubated at 37 ◦C for 24 h. The reagent
and media were then aspirated from the wells, to which 50 µL 99% isopropanol was then added,
and the plates were read at 570 nm. The absorbance readings from the cells, grown in the presence
of the tested compounds, were compared with uninhibited cell growth (using DMSO as the blank)
to determine the relative percent viability. The percent viability was determined through the MTT
assay. The percent viability is calculated through comparison of a measured value against that of
the uninhibited control: %viability = OD570E/OD570
compound-exposed cells, while OD570P is the reading from the uninhibited cells (positive control).
Cytotoxic potential is determined by a percent viability of <70%.
P
×
100, where OD570E is the reading from the
3.5. In Vitro Antiproliferative Assay
Human monocytic leukemia THP-1 cells were used for in vitro antiproliferative assay. Cells were
obtained from the European Collection of Cell Cultures (ECACC, Salisbury, UK) and routinely cultured
in RPMI 1640 medium supplemented with 10% fetal bovine serum, 2% L-glutamine, 1% penicillin
and streptomycin at 37 ◦C with 5% CO2. Cells were passaged at approximately one-week intervals.
Antiproliferative activity of the compounds was determined using a Water Soluble Tetrazolium
Salts-1 (WST-1, 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium) assay kit
(Roche Diagnostics, Mannheim, Germany) according to the manufacturer’s instructions. The tested
compounds were dissolved in DMSO and added in five increasing concentrations (0.37, 1.1, 3.3, 10
and 30
µ
M) to the cell suspension in the culture RPMI 1640 medium. The maximum concentr◦ation of
DMSO in the assays never exceeded 0.1%. Subsequently, the cells were incubated for 24 h at 37 C with
5% CO2. For WST-1 assays, cells were seeded into 96-well plates (5
medium) in triplicate in serum-free RPMI 1640 medium, and measurements were taken 24 h after
the treatment with the compounds. The median inhibition concentration values, IC50, were deduced
through the production of a dose-response curve. All data were evaluated using GraphPad Prism 5.00
software (GraphPad Software, San Diego, CA, USA). The results are summarized in Table 1.
×
104 cells/well in 100
µL culture
4. Conclusions
Series of nineteen N-(alkoxyphenyl)-2-hydroxynaphthalene-1-carboxamides (
nineteen positional isomers N-(alkoxyphenyl)-1-hydroxynaphthalene-2-carboxamides (
1
–
7c) and their
14c) were
8
–
prepared by means of microwave synthesis and subsequently characterized. All the compounds
were tested for their in vitro antimycobacterial activity against M. tuberculosis, M. smegmatis and
M. kansasii. The most effective compounds were also tested for their in vitro antiproliferative effect
against the THP-1 cells. Lipophilicity was found as the main physicochemical parameter influencing
the activity, and more lipophilic compounds expressed higher potency. In general, N-(alkoxyphenyl)-
2-hydroxynaphthalene-1-carboxamides showed higher activity against M. tuberculosis, while
N-(alkoxyphenyl)-1-hydroxynaphthalene-2-carboxamides demonstrated higher effect against
M. smegmatis and M. kansasii, but also stronger antiproliferative effect against the human THP-1
cell line. 2-Hydroxy-N-(4-propoxyphenyl)naphthalene-1-carboxamide (4c) showed the highest activity
(MIC = 12 µM) against M. tuberculosis with insignificant toxicity, while N-[3-(but-2-yloxy)phenyl]- (7b)
and N-[4-(but-2-yloxy)phenyl]-2-hydroxynaphthalene-1-carboxamide (7c) demonstrated high activity
against all three mycobacterial strains and insignificant toxicity. Their potency is comparable with that
of rifampicin. The performed MTT assay of the selected most efficient compounds showed that they
cause a decrease of mycobacterial cell metabolism. Based on the presented results it can be concluded
that some of the discussed amides can be considered as promising agents for subsequent design of
novel antimycobacterial agents.

Molecules 2016, 21, 1068
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Acknowledgments: This study was supported by IGA VFU Brno 311/2016/FaF and 323/2015/FaF, the Slovak
Grant Agency VEGA 1/0770/15, the Slovak Research and Development Agency (Grant No. APVV-0516-12)
and by the Irish Department of Agriculture Fisheries and Food (FIRM): Refs 08RDCIT601 & 08RDCIT617. The
HPLC/HRMS system forms a part of the National Infrastructure CzeCOS (LM2015061); Michal Oravec was
supported by the National Sustainability Program (NPU I; Grant No. LO1415 POLYMAT).
Author Contributions: Tomas Gonec, Jiri Kos, Josef Jampilek—design, synthesis of the compounds, SAR, writing
of the paper. Michal Oravec, Jana Dohanosova, Tibor Liptaj—analysis/characterization of the compounds.
Sarka Pospisilova, Alois Cizek, Aidan Coffey—antimicrobial evaluation. Tereza Kauerova, Peter Kollar—
cytotoxicity assay.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
Working Group on New TB Drugs 2016. Available online: http://www.newtbdrugs.org/blog/category/tb-
news/ (accessed on 1 July 2016).
2.
3.
World Health Organization. Global Tuberculosis Report 2015; WHO Press: Geneva, Switzerland, 2015.
Ioachimescu, O.C.; Tomford, J.W. Nontuberculous mycobacterial disorders. In Disease Management Project;
Carey, W., Ed.; Cleveland Clinic—Centre for Continuing Education: Cleveland, OH, USA, 2015; Available
online: http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/infectious-disease/
nontuberculous-mycobacterial-disorders/Default.htm (accessed on 1 July 2016).
4.
5.
Kratky, M.; Vinsova, J. Salicylanilide ester prodrugs as potential antimicrobial agents—A review. Curr. Pharm.
Des. 2011, 17, 3494–3505. [CrossRef] [PubMed]
Zadrazilova, I.; Pospisilova, S.; Pauk, K.; Imramovsky, A.; Vinsova, J.; Cizek, A.; Jampilek, J. In vitro
bactericidal activity of 4- and 5-chloro-2-hydroxy-N-(1-oxo-1-(phenylamino)alkan-2-yl)benzamides against
MRSA. BioMed. Res. Int. 2015, 2015, 349534. [CrossRef] [PubMed]
6.
Zadrazilova, I.; Pospisilova, S.; Masarikova, M.; Imramovsky, A.; Monreal-Ferriz, J.; Vinsova, J.; Cizek, A.;
Jampilek, J. Salicylanilide carbamates: Promising antibacterial agents with high in vitro activity against
methicillin-resistant Staphylococcus aureus. Eur. J. Pharm. Sci. 2015, 77, 197–207. [CrossRef] [PubMed]
Pattabiraman, V.R.; Bode, J.W. Rethinking amide bond synthesis. Nature 2011, 480, 471–479. [CrossRef]
[PubMed]
Imramovsky, A.; Vinsova, J.; Monreal-Ferriz, J.; Dolezal, R.; Jampilek, J.; Kaustova, J.; Kunc, F.
New antituberculotics originated from salicylanilides with promising in vitro activity against atypical
mycobacterial strains. Bioorg. Med. Chem. 2009, 17, 3572–3579. [CrossRef] [PubMed]
Zumla, A.; Nahid, P.; Cole, S.T. Advances in the development of new tuberculosis drugs and treatment
regimens. Nat. Rev. Drug Discov. 2013, 12, 388–404. [CrossRef] [PubMed]
7.
8.
9.
10. Zucca, M.; Scutera, S.; Savoia, D. New chemotherapeutic strategies against malaria, leishmaniasis and
trypanosomiases. Curr. Med. Chem. 2013, 20, 502–526. [CrossRef] [PubMed]
11. Gonec, T.; Kos, J.; Zadrazilova, I.; Pesko, M.; Keltosova, S.; Tengler, J.; Bobal, P.; Kollar, P.; Cizek, A.;
Kralova, K.; et al. Antimycobacterial and herbicidal activity of ring-substituted 1-hydroxynaphthalene-
2-carboxanilides. Bioorg. Med. Chem. 2013, 21, 6531–6541. [CrossRef] [PubMed]
12. Pauk, K.; Zadrazilova, I.; Imramovsky, A.; Vinsova, J.; Pokorna, M.; Masarikova, M.; Cizek, A.; Jampilek, J.
New derivatives of salicylamides: Preparation and antimicrobial activity against various bacterial species.
Bioorg. Med. Chem. 2013, 21, 6574–6581. [CrossRef] [PubMed]
13. Jampilek, J. Recent advances in design of potential quinoxaline anti-infectives. Curr. Med. Chem. 2014, 21,
4347–4373. [CrossRef] [PubMed]
14. Kos, J.; Nevin, E.; Soral, M.; Kushkevych, I.; Gonec, T.; Bobal, P.; Kollar, P.; Coffey, A.; O´Mahony, J.; Liptaj, T.;
et al. Synthesis and antimycobacterial properties of ring-substituted 6-hydroxynaphthalene-2-carboxanilides.
Bioorg. Med. Chem. 2015, 23, 2035–2043. [CrossRef] [PubMed]
15. Kos, J.; Zadrazilova, I.; Nevin, E.; Soral, M.; Gonec, T.; Kollar, P.; Oravec, M.; Coffey, A.; O´Mahony, J.;
Liptaj, T.; et al. Ring-substituted 8-Hydroxyquinoline-2-carboxanilides as potential antimycobacterial agents.
Bioorg. Med. Chem. 2015, 23, 4188–4196. [CrossRef] [PubMed]
16. Gonec, T.; Kos, J.; Zadrazilova, I.; Pesko, M.; Govender, R.; Keltosova, S.; Kollar, P.; Imramovsky, A.;
O´Mahony, J.; Coffey, A.; et al. Antibacterial and herbicidal activity of ring-substituted 2-hydroxynaphthalene-
1-carboxanilides. Molecules 2013, 18, 9397–9419. [CrossRef] [PubMed]

Molecules 2016, 21, 1068
17 of 18
17. De Marco, A.; de Candia, M.; Carotti, A.; Cellamare, S.; de Candia, E.; Altomare, C. Lipophilicity-related
inhibition of blood platelet aggregation by nipecotic acid anilides. Eur. J. Pharm. Sci. 2004, 22, 153–164.
[CrossRef] [PubMed]
18. Gonec, T.; Zadrazilova, I.; Nevin, E.; Kauerova, T.; Pesko, M.; Kos, J.; Oravec, M.; Kollar, P.; Coffey, A.;
O´Mahony, J.; et al. Synthesis and biological evaluation of N-alkoxyphenyl-3-hydroxynaphthalene-2-
carboxanilides. Molecules 2015, 20, 9767–9787. [CrossRef] [PubMed]
19. Zheng, H.; Lu, L.; Wang, B.; Pu, S.; Zhang, X.; Zhu, G.; Shi, W.; Zhang, L.; Wang, H.; Wang, S.; et al. Genetic
basis of virulence attenuation revealed by comparative genomic analysis of Mycobacterium tuberculosis strain
H37Ra versus H37Rv. PLoS ONE 2008, 3, e2375. [CrossRef] [PubMed]
20. Matveychuk, A.; Fuks, L.; Priess, R.; Hahim, I.; Shitrit, D. Clinical and radiological features of
Mycobacterium kansasii and other NTM infections. Resp. Med. 2012, 106, 1472–1477. [CrossRef] [PubMed]
21. Acharya, N.; Varshney, U. Biochemical properties of single-stranded DNA-binding protein from
Mycobacterium smegmatis, a fast-growing Mycobacterium and its physical and functional interaction with
uracil DNA glycosylases. J. Mol. Biol. 2002, 318, 1251–1264. [CrossRef]
22. Bueno, J. Antitubercular in vitro drug discovery: Tools for begin the search. In Understanding Tuberculosis-New
Approaches to Fighting against Drug Resistance; Cardona, P.J., Ed.; InTech: Rijeka, Croatia, 2012; pp. 147–168.
23. Terada, H. Uncouplers of oxidative phosphorylation. Environ. Health Perspect. 1990, 87, 213–218. [CrossRef]
[PubMed]
24. Feng, X.; Zhu, W.; Schurig-Briccio, L.A.; Lindert, S.; Shoen, C.; Hitchings, R.; Li, J.; Wang, Y.; Baig, N.;
Zhou, T.; et al. Antiinfectives targeting enzymes and the proton motive force. Proc. Natl. Acad. Sci. USA
2015, 112, E7073–E7082. [CrossRef] [PubMed]
25. Imramovsky, A.; Pesko, M.; Monreal-Ferriz, J.; Kralova, K.; Vinsova, J.; Jampilek, J. Photosynthesis-inhibiting
efficiency of 4-chloro-2-(chlorophenylcarbamoyl)phenyl alkyl-carbamates. Bioorg. Med. Chem. Lett. 2011, 21,
4564–4567. [CrossRef] [PubMed]
26. Kralova, K.; Perina, M.; Waisser, K.; Jampilek, J. Structure-activity relationships of N-benzylsalicylamides for
inhibition of photosynthetic electron transport. Med. Chem. 2015, 11, 156–164. [CrossRef] [PubMed]
27. Terada, H.; Goto, S.; Yamamoto, K.; Takeuchi, I.; Hamada, Y.; Miyake, K. Structural requirements of
salicylanilides for uncoupling activity in mitochondria: Quantitative analysis of structure-uncoupling
relationships. Biochim. Biophys. Acta. 1988, 936, 504–512. [CrossRef]
28. Parasitipedia.net. Salicylanilides: Anthelmintics for Veterinary Use on Cattle, Sheep, Goats, Pigs, Poultry,
Horses, Dogs and Cats against Parasitic Worms. Available online: http://parasitipedia.net/index.php?
option=com_content&view=article&id=2447&Itemid=2714 (accessed on 4 August 2016).
29. Arjunan, V.; Santhanam, R.; Rani, T.; Rosi, H.; Mohan, S. Conformational, vibrational, NMR and DFT studies
of N-methylacetanilide. Spectrochim. Acta A Mol. Biomol. Spectrosc. 2013, 104, 182–196. [CrossRef] [PubMed]
30. Malik, I.; Bukovsky, M.; Andriamainty, F.; Galisinova, J. Anti-microbial activity of meta-alkoxyphenylcarbamates
containing substituted N-phenylpiperazine fragment. Braz. J. Microbiol. 2012, 43, 959–965. [PubMed]
0
0
31. Sindt, A.; Mackay, M. Flukicides. IV. Crystal and molecular structure of 3 -chloro-4 -(p-chlorophenoxy)-3,5-
diiodosalicylanilide (rafoxanide). Aust. J. Chem. 1980, 33, 203–207. [CrossRef]
32. Li, D.D.; Qin, Y.J.; Sun, J.; Li, J.R.; Fang, F.; Du, Q.R.; Qian, Y.; Gong, H.B.; Zhu, H.L. Optimization
of substituted 6-salicyl-4-anilinoquinazoline derivatives as dual EGFR/HER2 tyrosine kinase inhibitors.
PLoS ONE 2013, 8, e69427. [CrossRef] [PubMed]
33. Musiol, R.; Jampilek, J.; Buchta, V.; Niedbala, H.; Podeszwa, B.; Palka, A.; Majerz-Maniecka, K.; Oleksyn, B.;
Polanski, J. Antifungal properties of new series of quinoline derivatives. Bioorg. Med. Chem. 2006, 14,
3592–3598. [CrossRef] [PubMed]
34. Bobal, P.; Sujan, J.; Otevrel, J.; Imramovsky, A.; Padelkova, Z.; Jampilek, J. Microwave-assisted synthesis of
new substituted anilides of quinaldic acid. Molecules 2012, 17, 1292–1306. [CrossRef] [PubMed]
35. Li, K.; Schurig-Briccio, L.A.; Feng, X.; Upadhyay, A.; Pujari, V.; Lechartier, B.; Fontes, F.L.; Yang, H.; Rao, G.;
Zhu, W.; et al. Multitarget drug discovery for tuberculosis and other infectious diseases. J. Med. Chem. 2014
57, 3126–3139. [CrossRef] [PubMed]
,
36. Hoagland, D.T.; Liu, J.; Lee, R.B.; Lee, R.E. New agents for the treatment of drug-resistant
Mycobacterium tuberculosis. Adv. Drug Deliv. Rev. 2016, 102, 55–72. [CrossRef] [PubMed]
37. Thannaa, S.; Sucheck, S.J. Targeting the trehalose utilization pathways of Mycobacterium tuberculosis.
Med. Chem. Commun. 2016, 7, 69–85. [CrossRef] [PubMed]

Molecules 2016, 21, 1068
18 of 18
38. ROCHE. Cell Proliferation Reagent WST-1. Roche Diagnostics GmbH: Mannheim, Germany, 2011.
Available online: http://www.molecularinfo.com/MTM/J/J2/J2--2/J2--2.pdf (accessed on 1 July 2016).
39. Suffness, M.; Douros, J. Current status of the NCI plant and animal product program. J. Nat. Prod. 1982, 45,
1–14. [CrossRef] [PubMed]
40. Weiss, R.H.; Wintringham, A.C.; American Cyanamid Co. N-Substituted Amides of Aromatic ortho-Hydroxy
Carboxylic Acids. US 2,410,397, 29 October 1946.
41. Jadhav, G.V.; Rao, S.N.; Hirwe, N.W. Derivatives of 1-hydroxy-2-naphthoic acid. Part III. Arylamides and
their bromination products. J. Univ. Bombay B 1936, 5, 137–141.
42. Schwalbe, R.; Steele-Moore, L.; Goodwin, A.C. Antimicrobial Susceptibility Testing Protocols; CRC Press:
Boca Raton, FL, USA, 2007.
Sample Availability: Samples of compounds are available from authors T. Gonec, J. Kos, J. Jampilek.
©
2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC-BY) license (http://creativecommons.org/licenses/by/4.0/).