A new group of potential antituberculotics: N-(2-pyridylmethyl) salicylamides and N-(3-pyridylmethyl)salicylamides

Article abstract of DOI:10.2478/s11696-010-0084-9

As a part of our systematic study of antimycobacterially active derivatives of salicylamides, a series of nineteen derivatives of N-(2-pyridylmethyl) salicylamides and N-(3-pyridylmethyl)salicylamides was synthesised. The compounds exhibited in vitro activity against Mycobacterium tuberculosis and M. avium. Their lipophilicity, R_M, was measured by thin layer chromatography on silica gel impregnated with trioctadecylsilane and the logarithm of the partition coefficient (octanol-water), logP, was calculated. Both the parameters of lipophilicity correlated. The quantitative relationship between the structure and antimycobacterial activity was calculated. Antimycobacterial activity increased with an increase in lipophilicity. The N-(2-pyridylmethyl)salicylamide derivatives were more active than the derivatives of isomeric N-(3-pyridylmethyl)salicylamides. The geometry of compounds was calculated and the calculation was verified by measuring the length of the hydrogen bond between hydroxyl and carbonyl groups on the salicylic moiety.

Full text of DOI:10.2478/s11696-010-0084-9

Chemical Papers 65 (1) 52–59 (2011)
DOI: 10.2478/s11696-010-0084-9
ORIGINAL PAPER
A new group of potential antituberculotics:
-(2-pyridylmethyl)salicylamides and
-(3-pyridylmethyl)salicylamides
a
a
a
aEva Petrlíková*, Karel Waisser, Karel Palát, Jr., Jiří Kuneš,
bJarmila Kaustová
aDepartment of Inorganic and Organic Chemistry, Faculty of Pharmacy in Hradec Králové, Charles University in Prague,
Heyrovského 1203, CZ-50003 Hradec Králové, Czech Republic
bRegional Institute of Public Health, Partyzánské náměstí 7, CZ-70200 Ostrava, Czech Republic
Received 21 May 2010; Revised 5 September 2010; Accepted 6 September 2010
As a part of our systematic study of antimycobacterially active derivatives of salicylamides, a series
of nineteen derivatives of N-(2-pyridylmethyl)salicylamides and N-(3-pyridylmethyl)salicylamides
was synthesised. The compounds exhibited in vitro activity against Mycobacterium tuberculosis
and M. avium. Their lipophilicity, RM, was measured by thin layer chromatography on silica gel
impregnated with trioctadecylsilane and the logarithm of the partition coefficient (octanol–water),
logP, was calculated. Both the parameters of lipophilicity correlated. The quantitative relationship
between the structure and antimycobacterial activity was calculated. Antimycobacterial activity
increased with an increase in lipophilicity. The N-(2-pyridylmethyl)salicylamide derivatives were
more active than the derivatives of isomeric N-(3-pyridylmethyl)salicylamides. The geometry of
compounds was calculated and the calculation was verified by measuring the length of the hydrogen
bond between hydroxyl and carbonyl groups on the salicylic moiety.
c
ꢀ 2011 Institute of Chemistry, Slovak Academy of Sciences
Keywords: salicylamide, picoline, lipophilicity, TLC, QSAR, antimycobacterial activity
Introduction
tibacterial action of salicylanilides was probably dif-
ferent from the action of other antibacterial drugs,
and that salicylanilides could serve as bacterial two-
component system inhibitors (Hlasta et al., 1998;
Macielag et al., 1998) inspired our research team
to develop new potential antituberculotics. The re-
search was mainly focused on different modifications
of the salicylamide molecule. N-benzylsalicylamides,
N-benzylpicolinanilides, N-benzylpicolinamides, 2-sul-
phanylbenzanilides, and N-benzyl-2-sulphanylbenz-
amides have been prepared and tested against some
strains of mycobacteria (Waisser et al., 2003a).
Tuberculosis has always been a serious problem
in developing countries and the multi-drug resistant
strains of M. tuberculosis are being transferred by the
migration of people to Europe and North America.
The World Health Organization (2009) estimated that
there were 463500 new cases of tuberculosis in Europe
in 2007. The search for antituberculotics with a new
structure and new mechanism of action has long been
one of the major topics of medicinal chemistry. Sixty-
six new papers were published in the field of hetero-
cyclic compounds showing activity against mycobac-
teria in 2009 (according to The Chemical Abstracts).
The results of research carried out in New Jersey
which demonstrated that the mechanism of the an-
This paper is part of a comprehensive study dealing
with salicylamides. N-Benzylsalicylamides prepared
previously (Waisser et al., 2003b) possessed low sol-
ubility in water which in some cases caused problems
*Corresponding author, e-mail: eva.petrlikova@faf.cuni.cz

E. Petrlíková et al./Chemical Papers 65 (1) 52–59 (2011)
53
with biological testing. N-(3-Pyridylmethyl)salicyl-
Experimental
amides were prepared in order to increase the solu-
bility in water and in a medium.
Salicylic acid and its substituted derivatives, phe-
nol, phosphoryl chloride, dimethyl sulphoxide
(DMSO), pyridin-2-ylmethanamine, and pyridin-3-
ylmethanamine were purchased from Sigma–Aldrich
(Germany).
Since the QSAR analysis has frequently been used
successfully for the prediction of new antimycobacteri-
ally active derivatives (Nemeček et al., 2009; Revathi
et al., 2009), a further goal of this paper was the QSAR
analysis of newly prepared compounds. Because a cor-
relation exists between antimycobacterial activity and
lipophilicity expressed as logP (P denotes partition co-
efficient in octanol–water), it was necessary to verify
the accuracy of the calculated logP values with the
experimental data. As recommended in the literature
(Kaliszan, 1984), reverse phase thin layer chromatog-
raphy was employed for this purpose.
A quantum-chemical calculation of the optimum
geometry for these molecules was performed. Measure-
ment of the length of the hydrogen bond between the
hydroxyl and the carbonyl groups of the salicylic moi-
ety by infrared spectroscopy completed this research.
The melting points were determined using Kofler
apparatus. The samples for the analyses and antimy-
cobacterial tests were dried over P2O5 at 61◦C and 66
Pa for 24 h. Elemental analyses (C, H, N) were per-
formed on a CHNS-O CE elemental analyser (Fisions
EA 1110, Milan, Italy) and were within 0.4 % of the
theoretical values. The standard IR spectra (in KBr
pellets) were measured using a Nicolet Impact 400 ap-
paratus. Infrared absorption spectra for the study of
hydrogen bonds between the hydrogen atom of the
phenol OH group and the oxygen atom of the carbonyl
group were recorded in tetrachloromethane (dried over
P2O5 and purified by distillation) solutions (c =
2 × 10−4 mol L−1) using a Nicolet 6700 FTIR spec-
trometer purged with dried and purified air (128 scans,
Theoretical
resolution 4 cm−1, detector DTGS, 4000–3000 cm−1
)
All regression calculations were set up using the
Linreg and Multireg programs for Microsoft Excel.
Quantum-chemical calculations were performed using
the Gaussian 03W program, version 6.1, revision-E.01
(Gaussian, Inc.). The geometry of the molecules was
optimised using the B3LYP/6-311+G(d,p) method.
Possible initial conformations for the optimisations
based on the density functional theory (DFT) level
were sought by simulated heating (from 0 K to 800 K),
using molecular dynamics with the RM1 descriptors.
The software HyperChem 8.0.4 (HyperCube, Inc.) was
employed for these calculations. Models were visu-
alised by GaussView software, version 4.1.2 (Gaussian,
Inc.).
using a 5 cm quartz cell. The spectra were measured
against air as a background, and then the spectra
of solvents were subtracted manually. The 1H and
13C NMR spectra were recorded in DMSO-d6 solu-
tions at room temperature using a Varian Mercury-
Vx BB 300 spectrometer operating at 300 MHz for
1H NMR and 75 MHz for 13C NMR. Tetramethylsi-
lane was used as a standard. TLC was performed on
silica gel plates pre-coated with a fluorescent indicator
Silufol UV 254 (RP-18 F254s, Merck, Germany) and
impregnated with trioctadecylsilane. Aqueous acetone
(60 mass %) was used as the mobile phase.
The antimycobacterial activity was determined in
the routinely used Šula semisynthetic medium con-
taining bovine serum (SEVAC, Prague, Czech Re-
public). The compounds were added to the medium
as DMSO solutions. The final concentrations were
1000 µmol L−1, 500 µmol L−1, 250 µmol L−1, 125
Calculations of all regressions in the study of
lipophilicity were performed using the Linreg and
Multireg programs in Microsoft Excel. Logarithms of
the partition coefficient (logP) were calculated using
the ChemBioOffice.
µmol L−1, 62.5 µmol L−1, 31 µmol L−1, 16 µmol L−1
,
O
6
N
5
6'
5'
N
H
1
2'
3'
N
NH2
4
2
OH
3
6
4'
OH
R
COOH
OH
O
O
II
O
OH
+
2'
5'
N
NH2
5
N
H
N
R
1
3'
4'
4
6'
R
2
OH
I
3
R
III
Fig. 1. Synthesis of N-(2-pyridylmethyl)salicylamides and N-(3-pyridylmethyl)salicylamides.

54
E. Petrlíková et al./Chemical Papers 65 (1) 52–59 (2011)
Table 1. Characteristics of the compounds prepared
wi(calc.)/mass %
wi(found)/mass %
—
Yield
%
M.p.
◦C
ν(C O)
—
Compound
R
Formula
Mr
C
H
N
cm−1
Ia
Ib
Ic
Id
Ie
If
H
C13H10O3
C14H12O3
214.22
228.25
244.24
228.25
244.24
248.66
232.21
248.66
293.12
283.11
372.01
242.28
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
70
64
64
65
65
75
76
78
84
75
82
47
42–43a
42.5–43
66.5–69
43–43.5
57
–
3-CH3
3-OCH3
4-CH3
4-OCH3
4-Cl
1685
1684
1685
1672
1672
1679
1685
1692
1700
1686
1636
C14H12O4
C14H12O3
C14H12O4
C13H9ClO3
C13H9FO3
C13H9ClO3
C13H9BrO3
C13H8Cl2O3
C13H8Br2O3
C14H14N2O2
49–52
Ig
Ih
Ii
5-F
84–85
5-Cl
95–97.5
112–113
112–113
126–127
145–146b
5-Br
Ij
3,5-Cl2
3,5-Br2
3-CH3
Ik
IIb
69.41
69.99
65.11
64.81
69.41
68.99
59.44
59.25
63.41
63.11
59.44
59.22
50.84
50.87
40.45
39.93
68.41
68.27
69.41
69.09
65.11
64.94
69.41
69.52
65.11
64.72
59.44
59.44
63.41
63.17
59.44
60.38
50.84
50.67
52.55
52.29
40.45
40.32
5.82
5.99
5.46
5.61
5.82
6.01
4.22
4.22
4.50
4.52
4.22
4.39
3.61
3.63
2.61
2.48
5.30
5.23
5.82
5.77
5.46
5.49
5.28
5.71
5.46
5.40
4.22
4.29
4.50
4.47
4.22
4.43
3.61
3.50
3.39
3.29
2.61
2.56
11.56
11.74
10.85
10.87
11.56
11.63
10.66
10.37
11.38
11.13
10.66
10.62
9.12
IIc
IId
3-OCH3
4-CH3
4-Cl
C14H14N2O3
C14H14N2O2
258.28
242.28
262.70
246.24
262.70
307.15
19
20
48
31
46
80
53
64
66
66
52
51
70
81
95
84
86
48
125–126
133–134
132–134
119–121
160–161c
178–179
170–171
167–170
122–124
110–111
168–171
137–138
181–184
213–217
178
1638
1650
1645
1653
1628
1651
1640
1638
1637
1642
1644
1651
1637
1648
1636
1643
1642
1640
IIf
C13H11ClN2O2
C13H11FN2O2
C13H11ClN2O2
C13H11BrN2O2
IIg
5-F
IIh
5-Cl
IIi
5-Br
8.85
IIk
3,5-Br2
H
C13H10Br2N2O2 386.04
7.26
6.97
IIIa
IIIb
IIIc
IIId
IIIe
IIIf
IIIg
IIIh
IIIi
IIIj
IIIk
C13H12N2O2
C14H14N2O2
C14H14N2O3
C14H14N2O2
C14H14N2O3
C13H11ClN2O2
C13H11FN2O2
C13H11ClN2O2
C13H11BrN2O2
228.25
242.28
258.28
242.28
258.28
262.70
246.24
262.70
307.15
12.27
12.17
11.56
11.37
10.85
10.55
11.56
11.55
10.85
10.53
10.66
10.26
11.38
11.08
10.66
10.16
9.12
3-CH3
3-OCH3
4-CH3
4-OCH3
4-Cl
5-F
5-Cl
5-Br
166–168
174–175
177–179
8.87
3,5-Cl2
3,5-Br2
C13H10Cl2N2O2 297.14
C13H10Br2N2O2 386.04
9.43
9.22
7.26
6.92
a) 42–43◦C (Allen & vanAllan, 1946), b) 140–142◦C (Bayer AG, 1975), c) 158–160◦C (Bayer AG, 1975).
8 µmol L−1, 4 µmol L−1, and 2 µmol L−1. The
minimum inhibitory concentrations (MIC) were de-
termined after incubation at 37◦C for 14 days and
21 days, respectively. The evaluation was repeated
three times. The mycobacterial strains: Mycobac-
terium tuberculosis CNCTC My 331/88 (identical
with H37RV and ATCC 27294) and Mycobacterium
avium CNCTC My 330/88 (identical with ATCC

E. Petrlíková et al./Chemical Papers 65 (1) 52–59 (2011)
55
Table 2. NMR spectral data of N-(2-pyridylmethyl)salicylamides (II) and N-(3-pyridylmethyl)salicylamides (III)
Compound
NMR spectral dataa
IIb
1H NMR (DMSO-d6), δ: 13.07 (bs, 1H, OH), 9.50 (t, 1H, J = 5.9 Hz, NH), 8.54–8.49 (m, 1H, H-6ꢀ), 7.82–7.71 (m,
2H, H-6, H-4ꢀ), 7.36–7.22 (m, 3H, H-4, H-3ꢀ, H-5ꢀ), 6.80 (t, 1H, J = 7.6 Hz, H-5), 4.59 (d, 2H, J = 5.9 Hz, CH2),
2.15 (s, 3H, CH3)
13C NMR (DMSO-d6), δ: 170.6, 159.5, 158.1, 149.1, 137.0, 134.8, 126.2, 124.8, 122.4, 121.2, 118.0, 113.6, 44.5, 15.6
IIc
1H NMR (DMSO-d6), δ: 12.49 (bs, 1H, OH), 9.42 (t, 1H, J = 5.7 Hz, NH), 8.53–8.49 (m, 1H, H-6ꢀ), 7.76 (dt, 1H,
J = 7.6 Hz, J = 1.8 Hz, H-4ꢀ), 7.50 (dd, 1H, J = 8.1 Hz, J = 1.2 Hz, H-6), 7.33 (d, 1H, J = 8.1 Hz, H-4), 7.30–7.23
(m, 1H, H-3ꢀ), 7.15–7.08 (m, 1H, H-5ꢀ), 6.84 (t, 1H, J = 8.1 Hz, H-5), 4.59 (d, 2H, J = 5.7 Hz, CH2), 3.78 (s, 3H,
OCH3)
13C NMR (DMSO-d6), δ: 169.5, 158.1, 150.7, 149.1, 148.6, 137.0, 122.4, 121.3, 119.1, 118.2, 115.7, 115.4, 56.0, 44.5
IId
IIf
1H NMR (DMSO-d6), δ: 12.33 (bs, 1H, OH), 9.36 (t, 1H, J = 5.7 Hz, NH), 8.53–8.49 (m, 1H, H-6ꢀ), 7.81 (d, 1H,
J = 8.2 Hz, H-6), 7.75 (td, 1H, J = 7.6 Hz, J = 1.8 Hz, H-4ꢀ), 7.33 (d, 1H, J = 7.6 Hz, H-3ꢀ), 7.30–7.23 (m, 1H,
H-5ꢀ), 6.76–6.69 (m, 2H, H-3, H-5), 4.59 (d, 2H, J = 5.7 Hz, CH2), 2.27 (s, 3H, CH3)
13C NMR (DMSO-d6), δ: 169.2, 160.1, 158.2, 149.1, 144.4, 136.9, 128.0, 122.4, 121.3, 119.9, 117.7, 112.8, 44.5, 21.2
1H NMR (DMSO-d6), δ: 12.63 (bs, 1H, OH), 9.46 (t, 1H, J = 5.4 Hz, NH), 8.51 (d, 1H, J = 4.7 Hz, H-6ꢀ), 7.94 (d,
1H, J = 8.0 Hz, H-6), 7.76 (td, 1H, J = 8.0 Hz, J = 1.8 Hz, H-4ꢀ), 7.34 (d, 1H, J = 8.0 Hz, H-3ꢀ), 7.30–7.23 (m,
1H, H-5ꢀ), 7.03–6.95 (m, 2H, H3, H-5), 4.61 (d, 2H, J = 5.4 Hz, CH2)
13C NMR (DMSO-d6), δ: 167.8, 160.4, 157.9, 149.2, 137.8, 137.0, 130.3, 122.5, 121.4, 119.3, 117.2, 115.2, 44.6
IIg
1H NMR (DMSO-d6), δ: 12.08 (bs, 1H, OH), 9.46 (t, 1H, J = 5.4 Hz, NH), 8.55–8.49 (m, 1H, H-6ꢀ), 7.81–7.71 (m,
2H, H-6, H-4ꢀ), 7.40–7.22 (m, 3H, H-4, H-3ꢀ, H-5ꢀ), 6.99–6.91 (m, 1H, H-3), 4.62 (d, 2H, J = 5.4 Hz, CH2)
13C NMR (DMSO-d6), δ: 167.4 (d, J = 2.3 Hz), 157.9, 155.8 (d, J = 1.1 Hz), 154.9 (d, J = 234.9 Hz), 149.2, 137.1,
122.5, 121.5, 121.2 (d, J = 32.3 Hz), 118.9 (d, J = 8.1 Hz), 116.6 (d, J = 6.3 Hz), 114.2 (d, J = 24.1 Hz), 44.7
IIh
IIi
1H NMR (DMSO-d6), δ: 12.18 (bs, 1H, OH), 9.33 (t, 1H, J = 5.4 Hz, NH), 8.38–8.33 (m, 1H, H-6ꢀ), 7.83 (d, 1H, J
= 2.3 Hz, H-6), 7.60 (td, 1H, J = 7.6 Hz, J = 1.8 Hz, H-4ꢀ), 7.28 (dd, 1H, J = 8.8 Hz, J = 2.3 Hz, H-4), 7.20 (d,
1H, J = 7.6 Hz, H-3ꢀ), 7.15–7.08 (m, 1H, H-5ꢀ), 6.80 (d, 1H, J = 8.8 Hz, H-5), 4.45 (d, 2H, J = 5.4 Hz, CH2)
13C NMR (DMSO-d6), δ: 167.3, 158.3, 157.8, 149.1, 137.0, 133.4, 128.0, 122.7, 122.5, 121.4, 119.4, 117.5, 44.7
1H NMR (DMSO-d6), δ: 12.38 (bs, 1H, OH), 9.49 (t, 1H, J = 5.7 Hz, NH), 8.54–8.48 (m, 1H, H-6ꢀ), 8.11 (d, 1H, J
= 2.3 Hz, H-6), 7.81–7.72 (m, 1H, H-4ꢀ), 7.59–7.52 (m, 1H, H-4), 7.36 (d, 1H, J = 9.0 Hz, H-3ꢀ), 7.32–7.24 (m, 1H,
H-5ꢀ), 6.91 (d, 1H, J = 8.8 Hz, H-3), 4.60 (d, 2H, J = 5.7 Hz, CH2)
13C NMR (DMSO-d6), δ: 167.3, 158.7, 157.8, 149.2, 137.1, 136.3, 130.9, 122.5, 121.5, 119.9, 118.0, 110.1, 44.7
IIk
1H NMR (DMSO-d6), δ: 9.81 (t, 1H, J = 5.7 Hz, NH), 8.51 (dd, 1H, J = 4.7 Hz, J = 1.8 Hz, H-6ꢀ), 8.23 (d, 1H, J
= 2.3 Hz, H-6), 7.99 (d, 1H, J = 2.3 Hz, H-4), 7.77 (td, 1H, J = 7.6 Hz, J = 1.8 Hz, H-4ꢀ), 7.37 (d, 1H, J = 7.6 Hz,
H-3ꢀ), 7.29 (dd, 1H, J = 7.6 Hz, J = 4.7 Hz, H-5ꢀ), 4.60 (d, 2H, J = 5.7 Hz, CH2)
13C NMR (DMSO-d6), δ: 168.5, 157.5, 157.3, 149.2, 138.8, 137.1, 129.4, 122.6, 121.6, 117.0, 112.4, 109.8, 44.8
IIIa
IIIb
IIIc
1H NMR (DMSO-d6), δ: 12.38 (bs, 1H, OH), 9.38 (bs, 1H, NH), 8.57 (s, 1H, H-2ꢀ), 8.46 (d, 1H, J = 4.7 Hz, H-6ꢀ),
7.87 (d, 1H, J = 8.0 Hz, H-6), 7.73 (d, 1H, J = 7.7 Hz, H-4ꢀ), 7.45–7.31 (m, 2H, H-4, H-5ꢀ), 6.96–6.84 (m, 2H, H-3,
H-5), 4.53 (d, 2H, J = 5.8 Hz, CH2)
13C NMR (DMSO-d6), δ: 169.2, 160.1, 149.1, 148.4, 135.4, 134.7, 134.0, 128.1, 123.7, 118.9, 117.6, 115.4, 40.4
1H NMR (DMSO-d6), δ: 13.03 (bs, 1H, OH), 9.46 (t, 1H, J = 5.7 Hz, NH), 8.56 (d, 1H, J = 1.8 Hz, H-2ꢀ), 8.46 (d,
1H, J = 4.7 Hz, H-6ꢀ), 7.77–7.67 (m, 2H, H-6, H-4ꢀ), 7.40–7.26 (m, 2H, H-4, H-5ꢀ), 6.79 (t, 1H, J = 7.6 Hz, H-5),
4.52 (d, 2H, J = 5.7 Hz, CH2), 2.14 (s, 3H, CH3)
13C NMR (DMSO-d6), δ: 170.5, 159.6, 149.1, 148.5, 135.4, 134.9, 134.6, 126.3, 124.8, 123.8, 118.1, 113.4, 40.5, 15.7
1H NMR (DMSO-d6), δ: 12.50 (bs, 1H, OH), 9.37 (t, 1H, J = 5.7 Hz, NH), 8.55 (d, 1H, J = 1.5 Hz, H-2ꢀ), 8.46 (dd,
1H, J = 4.7 Hz, J = 1.5 Hz, H-6ꢀ), 7.76–7.69 (m, 1H, H-4ꢀ), 7.43 (dd, 1H, J = 8.2 Hz, J = 1.2 Hz, H-6), 7.38–7.32
(m, 1H, H-5ꢀ), 7.13–7.07 (m, 1H, H-4), 6.82 (t, 1H, J = 8.2 Hz, H-5), 4.51 (d, 2H, J = 5.7 Hz, CH2), 3.77 (s, 3H,
OCH3)
13C NMR (DMSO-d6), δ: 169.7, 150.8, 149.1, 148.7, 148.4, 135.4, 134.6, 123.7, 118.9, 118.2, 115.7, 115.1, 56.0, 40.5
IIId
IIIe
IIIf
1H NMR (DMSO-d6), δ: 12.42 (1H, bs, OH), 9.29 (t, 1H, J = 5.7 Hz, NH), 8.55 (d, 1H, J = 1.5 Hz, H-2ꢀ), 8.46
(dd, 1H, J = 4.7 Hz, J = 1.5 Hz, H-6ꢀ), 7.80–7.67 (m, 2H, H-6, H-4ꢀ), 7.35 (dd, 1H, J = 7.7 Hz, J = 4.7 Hz, H-5ꢀ),
6.75–6.67 (m, 2H, H-3, H-5), 4.50 (d, 2H, J = 5.7 Hz, CH2), 2.26 (s, 3H, CH3)
13C NMR (DMSO-d6), δ: 169.4, 160.4, 149.1, 148.4, 144.6, 135.4, 134.8, 127.8, 123.7, 119.9, 117.7, 112.5, 40.5, 21.3
1H NMR (DMSO-d6), δ: 12.85 (bs, 1H, OH), 9.22 (t, 1H, J = 5.9 Hz, NH), 8.58–8.52 (m, 1H, H-2ꢀ), 8.49–8.42 (m,
1H, H-6ꢀ), 7.80 (d, 1H, J = 9.4 Hz, H-6), 7.75–7.68 (m, 1H, H-4ꢀ), 7.35 (dd, 1H, J = 7.6 Hz, J = 4.7 Hz, H-5ꢀ),
6.51–6.39 (m, 2H, H-3, H-5), 4.50 (d, 2H, J = 5.9 Hz, CH2), 3.76 (s, 3H, OCH3)
13C NMR (DMSO-d6), δ: 169.5, 163.9, 162.8, 149.1, 148.4, 135.4, 134.9, 129.1., 123.8, 107.8, 106.4, 101.4, 55.6, 44.2
1H NMR (DMSO-d6), δ: 12.63 (bs, 1H, OH), 9.37 (t, 1H, J = 5.7 Hz, NH), 8.56 (s, 1H, H-2ꢀ), 8.46 (d, 1H, J =
4.1 Hz, H-6ꢀ), 7.88 (d, 1H, J = 8.5 Hz, H-6), 7.76–7.69 (m, 1H, H-4ꢀ), 7.35 (dd, 1H, J = 7.7 Hz, J = 4.1 Hz, H-5ꢀ),
7.02–6.93 (m, 2H, H-3, H-5), 4.52 (d, 2H, J = 5.7 Hz, CH2)
13C NMR (DMSO-d6), δ: 168.1, 160.7, 149.1, 148.5, 137.9, 135.5, 134.6, 130.0, 123.8, 119.2, 117.2, 114.9, 40.4

56
E. Petrlíková et al./Chemical Papers 65 (1) 52–59 (2011)
Table 2. (continued)
Compound
NMR spectral dataa
IIIg
1H NMR (DMSO-d6), δ: 12.08 (bs, 1H, OH), 9.35 (t, 1H, J = 5.6 Hz, NH), 8.56 (s, 1H, H-2ꢀ), 8.49–8.43 (m, 1H,
H-6ꢀb), 7.79–7.63 (m, 2H, H-6, H-4ꢀ), 7.42–7.20 (m, 2H, H-4, H-5ꢀ), 6.94 (dd, 1H, J = 8.8 Hz, J = 4.7 Hz, H-3), 4.52
(d, 2H, J = 5.6 Hz, CH2)
13C NMR (DMSO-d6), δ: 167.8 (d, J = 2.3 Hz), 156.4, 154.8 (d, J = 234.4 Hz), 149.2, 148.5, 135.5, 134.6, 123.8,
121.0 (d, J = 23.6 Hz), 119.0 (d, J = 7.5 Hz), 116.2 (d, J = 6.9 Hz), 114.0 (d, J = 24.8 Hz), 40.5
IIIh
IIIi
IIIj
IIIk
1H NMR (DMSO-d6), δ: 12.38 (bs, 1H, OH), 9.40 (t, 1H, J = 5.7 Hz, NH), 8.58 (s, 1H, H-2ꢀ), 8.45 (d, 1H, J = 4.5
Hz, H-6ꢀ), 7.95 (d, 1H, J = 2.5 Hz, H-6), 7.70 (d, 1H, J = 7.7 Hz, H-4ꢀ), 7.50 (dd, 1H, J = 8.8 Hz, J = 2.5 Hz, H-4),
7.25 (dd, 1H, J = 7.7 Hz, J = 4.5 Hz, H-5ꢀ), 6.90 (d, 1H, J = 8.8 Hz, H-3), 4.52 (d, 2H, J = 5.7 Hz, CH2)
13C NMR (DMSO-d6), δ: 167.7, 158.5, 149.2, 148.5, 135.5, 134.5, 133.5, 127.7, 123.7, 122.6, 119.5, 117.1, 40.5
1H NMR (DMSO-d6), δ: 12.38 (bs, 1H, OH), 9.39 (t, 1H, J = 5.7 Hz, NH), 8.56 (s, 1H, H-2ꢀ), 8.47 (d, 1H, J = 4.5
Hz, H-6ꢀ), 8.05 (d, 1H, J = 2.5 Hz, H-6), 7.73 (d, 1H, J = 7.7 Hz, H-4ꢀ), 7.54 (dd, 1H, J = 8.8 Hz, J = 2.5 Hz, H-4),
7.36 (dd, 1H, J = 7.7 Hz, J = 4.5 Hz, H-5ꢀ), 6.90 (d, 1H, J = 8.8 Hz, H-3), 4.52 (d, 2H, J = 5.7 Hz, CH2)
13C NMR (DMSO-d6), δ: 167.6, 159.0, 149.2, 148.5, 136.4, 135.5, 134.5, 130.6, 123.8, 119.9, 117.7, 110.0, 40.5
1H NMR (DMSO-d6), δ: 13.52 (bs, 1H, OH), 9.73 (t, 1H, J = 5.4 Hz, NH), 8.58 (s, 1H, H-2ꢀ), 8.48 (d, 1H, J = 4.7
Hz, H-6ꢀ), 8.01 (d, 1H, J = 2.1 Hz, H-6), 7.76 (d, 1H, J = 2.1 Hz, H-4), 7.79–7.72 (m, 1H, H-4ꢀ), 7.37 (dd, 1H, J =
7.6 Hz, J = 4.7 Hz, H-5ꢀ), 4.53 (d, 2H, J = 5.4 Hz, CH2)
13C NMR (DMSO-d6), δ: 168.5, 155.9, 149.2, 148.6, 135.7, 133.9, 133.4, 125.9, 123.8, 122.6, 122.2, 116.5, 40.7
1H NMR (DMSO-d6), δ: 13.68 (bs, 1H, OH), 9.74 (t, 1H, J = 5.7 Hz, NH), 8.57 (s, 1H, H-2ꢀ), 8.48 (d, 1H, J = 4.7
Hz, H-6ꢀ), 8.16 (d, 1H, J = 2.1 Hz, H-6), 7.97 (d, 1H, J = 2.1 Hz, H-4), 7.75 (d, 1H, J = 7.6 Hz, H-4ꢀ), 7.37 (dd,
1H, J = 7.6 Hz, J = 4.7 Hz, H-5ꢀ), 4.53 (d, 2H, J = 5.7 Hz, CH2)
13C NMR (DMSO-d6), δ: 168.4, 157.3, 149.2, 148.6, 138.8, 135.7, 133.9, 129.3, 123.8, 116.8, 112.4, 109.8, 40.7
a) Atom numbering corresponds to the numbering in Fig. 1.
25291) were obtained from the Czech National Collec-
tion of Type Cultures (CNCTC), National Institute of
Public Health, Prague, Czech Republic.
for the preparation of salicylamides from salicylic acid,
phenylmethylamine, and phosphorus trichloride failed
(Waisser et al., 2001). N-(Pyridylmethyl)salicylamides
were prepared by the treatment of phenyl sali-
cylate (or substituted phenyl salicylates) with 2-
picolinylamine and 3-picolinylamine, respectively. The
phenyl salicylates were prepared by a modification of
the known method (Gaylord & Kamath, 1952). Char-
acterisation and spectral data of the compounds pre-
pared are summarised in Tables 1 and 2.
General procedure for the synthesis of phenyl
salicylates, N-(2-pyridylmethyl)salicylamides,
and N-(3-pyridylmethyl)salicylamides
A mixture of substituted salicylic acid (1 mol) and
phenol (1 mol) was heated in the presence of phospho-
ryl chloride (0.38 mol) at 75–80◦C for 4 h under re-
flux. The volume of the reaction mixture was reduced
during this heating and the obtained molten mass was
slowly poured into a 5 % solution of sodium carbonate
(100 mL) and stirred continuously. The phenyl salicy-
late precipitated was filtered off, washed with water
(4 × 20 mL) and crystallised from ethanol.
The structural assignment of the compounds is
1
based on H NMR, 13C NMR (Table 2), IR spectral
data and elemental analysis (Table 1). In the IR spec-
—
tra, ν(C O) vibrations were observed in the region of
—
1642–1692 cm−1 and 1628–1653 cm−1 for phenyl sal-
icylates and N-(pyridylmethyl)salicylamides, respec-
tively.
A mixture of amine (1 g) and phenyl salicy-
late (1.2 equivalents) was melted at 70–90◦C for
3 h and then heated under reflux with 96 %
ethanol (50–100 mL) for 10 min. The crude prod-
uct was filtered off and crystallised from 96 %
ethanol to give pure N-(2-pyridylmethyl)salicylamide.
N-(3-Pyridylmethyl)salicylamides were prepared anal-
ogously by melting a mixture of amine (1 g) and
phenyl salicylate (1.2 mole equivalents) at 190–210◦C
for 1.5 h.
The N-(pyridylmethyl)salicylamides were screened
for their in vitro antimycobacterial activity against
mycobacterial strains Mycobacterium tuberculosis
CNCTC My 331/88 (identical with H37RV and ATCC
27294) and Mycobacterium avium CNCTC My 330/
88 (identical with ATCC 25291). The mycobacterioses
caused by M. avium are rare but usually fatal. The re-
sults are summarised in Table 3.
The lipophilicity of compounds II and III was cal-
culated (logP in octanol–water) and also measured
using reverse phase thin layer chromatography (ex-
pressed by retention data values, RM, calculated ac-
cording to the equation RM = log(1/RF − 1)) in
order to verify the predicted values of the calculated
logP. The values of RM and logP are summarised
in Table 3. For comparison, the values of logP and
Results and discussion
A series of nineteen derivatives of N-(2-pyridyl-
methyl)salicylamide and N-(3-pyridylmethyl)salicyl-
amide was synthesised (Fig. 1, Table 1). The method

E. Petrlíková et al./Chemical Papers 65 (1) 52–59 (2011)
57
Table 3. Lipophilicity (logP and RM) and minimum inhibitory concentration (MIC) of compounds II, III, and IV
O
O
O
N
N
H
N
H
N
N
H
OH
OH
OH
R
R
R
II
III
IV
a
MIC/(µmol L−1
)
Compound
R
logP
RM
M. tuberculosis
M. avium
IIb
IIc
IId
IIf
IIg
IIh
IIi
IIk
3-CH3
3-OCH3
4-CH3
4-Cl
5-F
5-Cl
5-Br
3,5-Br2
H
3-CH3
3-OCH3
4-CH3
4-OCH3
4-Cl
5-F
5-Cl
5-Br
3,5-Cl2
3,5-Br2
H
3-OCH3
4-OCH3
4-Cl
2.09
1.48
2.09
2.16
1.76
2.16
2.43
3.26
1.18
1.67
1.06
1.67
1.06
1.74
1.34
1.74
2.01
2.30
2.84
2.52
2.39
2.39
3.08
3.08
3.53
3.64
4.18
–
0.25
−0.12
0.12
0.31
0.10
0.23
0.29
0.55
0.02
0.23
−0.16
0.12
−0.03
0.23
0.11
0.23
0.21
0.39
0.50
0.42
0.31
0.42
0.65
0.65
0.65
1.05
0.95
–
62.5/62.5
250/250
62.5/125
125/250
500/1000
125/250
250/500
125/250
500/500
250/250
250/500
250/500
500/500
125/250
ndb
125/250
1000/1000
250/500
500/500
500/1000
125/250
250/250
ndb
IIIa
IIIb
IIIc
IIId
IIIe
IIIf
IIIg
IIIh
IIIi
IIIj
IIIk
IVa
IVc
IVe
IVf
IVh
IVi
IVj
IVk
INHc
500/500
500/500
1000/1000
500/1000
1000/1000
250/250
ndb
500/500
125/125
250/500
125/250
ndb
ndb
ndb
ndb
1000/1000
125/125
ndb
125/ndb
62/62
ndb
ndb
125/125
125/125
>250/>250
ndb
125/ndb
62/62
5-Cl
5-Br
3,5-Cl2
3,5-Br2
–
62/ndb
ndb
32/62
32/32
1/1
a) Values given for 14 days/21 days of incubation; b) nd – not determined due to low solubility of the compound; c) isoniazid
(isonicotinohydrazide), used as a reference drug.
RM as well as MIC values (taken from Waisser et
al. (2003a)) for N-benzylsalicylamides (IV ), are also
given.
We sought a correlation between the values of RM
and logP using the Linreg program. According to Eq.
(1), it is possible to state that both parameters of
lipophilicity correlated with each other (Fig. 2)
log P = 2.64( 0.17)RM + 1.41( 0.075)
(1)
(r = 0.95, s = 0.260, n = 27, where r is the correlation
coefficient, s is the standard deviation, and n is the
number of compounds used for the calculation).
The Hansch approach was carried out in order to
study the relationship between the structure and an-
timycobacterial activity. The indicator parameter I1
was used for N-(2-pyridylmethyl)salicylamide deriva-
tives, while the indicator parameter I2 was used for
N-(3-pyridylmethyl)salicylamide derivatives. Another
Fig. 2. Correlation between logP and RM
.
parameter was lipophilicity expressed as RM or logP.
As both MICs corresponding to 14 days and 21 days

58
E. Petrlíková et al./Chemical Papers 65 (1) 52–59 (2011)
of incubation correlated, only the MIC values for the
14-day incubation experiments were used for calcula-
tions.
We found Eqs. (2) and (3) for the relation-
ships between structure and antimycobacterial activ-
ity against M. tuberculosis (14 days of incubation).
The statistical significance of these calculated equa-
tions for both parameters of lipophilicity (RM and
logP) was similar.
Table 4. Valence vibrations (ν(OH)) and calculated length (λ)
of hydrogen bond
˚
λ/A
Compound
ν(OH)/cm−1
∆ν(OH)/cm−1
IIb
IIc
IId
IIf
IIg
IIh
IIi
IIk
IIIa
IIIb
IIIc
IIId
IIIe
IIIf
IIIg
IIIh
IIIi
IIIj
IIIk
Phenol
3406
3406
3407
3399
3397
3395
3395
3389
3468
3468
3468
3469
3469
3466
3467
3466
3465
3464
3464
3611
205
205
204
212
214
216
216
222
143
143
143
142
142
145
144
145
146
147
147
–
1.64417
1.64684
1.66071
1.64788
1.65933
1.65586
1.65527
1.62770
1.67309
1.66326
1.66451
1.66884
1.67028
1.66280
1.67638
1.67403
1.67642
1.65312
1.64792
–
log (MIC) = −0.688( 0.254)RM + 0.072( 0.190)I1 +
+ 0.269( 0.194)I2 + 2.249( 0.216)
(2)
(r = 0.80, s = 0.236, n = 23, F = 11.13; F is the
Fischer–Snedecor distribution, F-test)
log (MIC) = −0.267( 0.089) logP+0.141( 0.163)I1+
+ 0.246( 0.187)I2 + 2.613( 0.310)
(3)
(r = 0.81, s = 0.229, n = 23, F = 12.17)
Similar equations were also found for the relation-
ship between the structure and antimycobacterial ac-
tivity against M. avium (14 days of incubation) (see
Eqs. (4) and (5)).
derivatives of N-(2-pyridylmethyl)salicylamides are
more suitable for the development of new antitubercu-
lotics than the corresponding N-(3-pyridylmethyl)sa-
licylamide derivatives.
log (MIC) = −0.187( 0.275)RM + 0.385( 0.198)I1 +
+ 0.643( 0.217)I2 + 2.166( 0.224)
(4)
The intramolecular hydrogen bonds between the
hydrogen atom of the phenol OH group and the oxy-
gen atom of the carbonyl group were studied using
diluted tetrachloromethane solutions (c = 2 ×10−4
mol L−1). At this level of dilution, intermolecular
bonds do not exist, and only monomers are observed.
A shift of ν(OH) band of the phenolic molecules (Ta-
ble 4) is observed depending on the position and na-
ture of the substituent(s). The shift ∆ν(OH) calcu-
lated for phenol as the reference molecule is in the
range of 204–222 cm−1 for 2-pyridyl derivatives and
142–185 cm−1 for 3-pyridyl analogues. These differ-
(r = 0.78, s = 0.258, n = 20, F = 8.36)
log (MIC) = −0.025( 0.102) logP+0.450( 0.180)I1+
+ 0.709( 0.221)I2 + 2.116( 0.344)
(5)
(r = 0.78, s = 0.262, n = 20, F = 8.03)
Eqs. (2)–(5) which show increasing antimycobacte-
rial activity with lipophilicity have a significance level
lower than 0.05. The significance level of Eq. (1) is
lower than 0.001. It is possible to conclude that the
Table 5. Calculated total energy (Eh) and length (λ) of possible hydrogen bonds in compounds IId and IIc
O
O
H
O
H
O
H
O
O
O
O
O
H
H
O
O
O
O
H
O
Conformer
H
O
O
O
O
H
N
H
N
N
H
N
N
H
N
N
H
N
N
H N
H
N
N
N
N
IIdB
IIcB
IId
IIdA
IIcA
IIcC
IIc
Eh/(kJ mol−1
)
−2105992.17 −2105958.36 −2105958.81 −2303487.47 −2303476.49 −2303476.73 −2303457.60
1.66071a
2.13908b
1.93131c
1.97334c
2.23179b
1.64684a
2.13788b
2.01384d
1.92950c
2.23725b
2.02460d
1.97948c
2.06871d
2.18585b
˚
λ/A
—
a) OH· · ·O C hydrogen bond; b) NH· · ·NC5H4 hydrogen bond; c) HO· · ·HN hydrogen bond; d) CH3O· · ·HO hydrogen bond.
—

E. Petrlíková et al./Chemical Papers 65 (1) 52–59 (2011)
59
Fig. 3. 3D models of compounds IId (left) and IIId (right).
ences correspond to the length of the hydrogen bond
in the 3D models calculated. A shorter distance be-
tween hydrogen and oxygen atoms indicates a stronger
interaction which leads to a higher shift of the band in
the IR spectrum. The IR spectral values for the intra-
molecular hydrogen bond and the calculated length, λ,
Republic and was financially supported by grant no. SVV-2010-
261-001.
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Acknowledgements. This study is part of research project
no. MSM0021620822 of the Ministry of Education of the Czech