Y.P. Subedi et al. / European Journal of Medicinal Chemistry 203 (2020) 112602
5
a selectivity that is opposite to that of the parental compound
kanamycin. The results show the importance of substitutions at
positions 60 and 600 of kanamycin for the differential inhibition of
Cx26 and Cx43 HCs. Based on the correlation between Cx43 HC
inhibitory potency and hydrophobicity, it seems possible to
enhance the selectivity of AKs toward Cx43 by increasing the hy-
drophobicity at position 600 without inducing steric hindrance, and
at position 60 by increasing hydrophobicity. Compound 12i seems
the most promising lead as Cx43 HC inhibitor because of its good
selectivity, and the simplicity and affordability of its production,
since it can be synthesized on a large scale without a need for
column purifications.
4.1e4.2 (m, 3H), 3.7e4.0 (m, 5H), 3.6e3.7 (m, 2H), 3.4e3.6 (m, 4H),
3.2e3.4 (m, 2H), 3.0e3.1 (m, 1H), 2.4e2.5 (m, 1H), 1.8e1.9 (m, 1H);
13C NMR (125 MHz, D2O)
d 157.87, 129.92 (2C), 121.80, 114.79,
100.57, 96.33, 83.91, 78.37, 72.70, 72.06, 71.11, 70.80, 70.77, 68.61,
68.13, 66.09, 65.48, 54.93, 49.93, 47.88, 40.35, 27.84. ESI/APCI
calculated for
561.2764.
C
24H41N4Oþ11 [MH]þ: 561.2772; measured m/e:
4.5. 600-O-(4-chlorophenyl)kanamycin A (11d)
This compound was synthesized as
a
light-brown solid
7.29 (d,
following the general procedure. 1H NMR (500 MHz, D2O)
d
J ¼ 8.5 Hz, 2H), 6.93 (d, J ¼ 9.0 Hz, 2H), 5.52 (d, J ¼ 3.5 Hz, 1H), 5.07
(d, J ¼ 3.0 Hz, 1H), 4.1e4.2 (m, 3H), 3.8e4.0 (m, 5H), 3.6e3.8 (m,
3H), 3.4e3.6 (m, 3H), 3.3e3.4 (m, 2H), 3.0e3.2 (m, 1H), 2.4e2.5 (m,
4. Experiment
4.1. General procedure for the synthesis of compounds 11a-g
1H), 2.14 (s, 1H) 1.8e1.9 (m, 1H); 13C NMR (125 MHz, D2O)
d 156.64,
129.50 (2C), 125.96, 116.18 (2C), 100.65, 96.67, 83.99, 78.78, 72.81,
72.09, 71.07, 70.80, 70.67, 68.65, 68.15, 66.35, 65.40, 54þ.91, 49.97,
47.90, 40.26, 28.03. ESI/APCI calculated for C24H40N4O11 [MH]þ:
595.2382; measured m/e: 595.2377.
Two equiv (0.4 mmol) of substituted phenol and 0.055 g
(0.4 mmol, 2 equiv) of K2CO3 were added to 0.20 g (0.2 mmol, 1
equiv) of compound 9 dissolved in anhydrous dimethylformamide
(DMF) and the mixture was heated at 60 ꢁC for 24 h with vigorous
stirring. The solvent was removed under reduced pressure and the
residue was washed with 3 ꢂ 20 mL water. The washed reaction
mixture was dried and treated with 2 mL of trifluoroacetic acid
using 10 mL anhydrous dichloromethane (DCM) as solvent. The
reaction was stirred at room temperature for 6 h and the solvent
was removed by blowing air inside a hood. Ten mL of water was
added and the mixture was stirred for 15 min at room temperature.
4.6. 600-O-(4-nitrophenyl)kanamycin A (11e)
This compound was synthesized as
a
light-yellow solid
8.19 (d,
following the general procedure. 1H NMR (500 MHz, D2O)
d
J ¼ 9.0 Hz, 2H), 7.07 (d, J ¼ 9.0 Hz, 2H), 5.52 (d, J ¼ 3.0 Hz, 1H), 5.05
(d, J ¼ 3.5 Hz, 1H), 4.3e4.4 (b, 2H), 4.2e4.3 (m, 1H), 3.6e4.0 (m, 9H),
3.3e3.6 (m, 5H), 3.1e3.2 (m, 1H), 2.3e2.5 (m, 1H), 1.7e1.8 (m, 1H);
The reaction mixture in water was filtered through a 0.2-
mm sy-
13C NMR (125 MHz, D2O)
d 163.52, 141.52, 126.21 (2C), 114.83 (2C),
ringe filter and the water from the filtrate was removed by air
blowing. Then, the compound was purified using a CG50 cation
exchange resin (Amberlite), and the pure compound, obtained in
acetate form after the CG50-based purification, was converted to
the chloride form using IR410 (Clꢀ form) resin.
100.59, 97.26, 84.39, 79.78, 73.19, 72.11, 70.92, 70.83, 70.72, 68.60,
68.22, 66.59, 65.47, 54.91, 50.16, 48.16, 40.27, 29.01. ESI/APCI
calculated for C24H40N5Oþ13 [MH]þ: 606.2623; measured m/e:
606.2634.
4.7. 600-O-(4-(1,10-biphenyl))kanamycin A (11f)
4.2. 600-O-(4-methoxyphenyl)kanamycin A (11a)
This compound was synthesized as a white solid following the
This compound was synthesized as a white solid following the
general procedure. 1H NMR (500 MHz, D2O)
d 7.4e7.5 (m, 4H),
general procedure. 1H NMR (500 MHz, D2O)
d
6.9e7.0 (m, 4H), 5.51
7.2e7.4 (m, 3H), 6.94 (d, J ¼ 8.5 Hz, 2H), 5.51 (d, J ¼ 4.0 Hz, 1H), 5.06
(d, J ¼ 3.5 Hz, 1H), 4.1e4.3 (m, 3H), 3.8e4.0 (m, 5H), 3.6e3.8 (m,
2H), 3.4e3.6 (m, 4H), 3.2e3.4 (m, 2H), 3.0e3.1 (m, 1H), 2.4e2.5 (m,
(d, J ¼ 3.5 Hz, 1H), 5.05 (d, J ¼ 3.0 Hz, 1H), 4.1e4.2 (m, 3H), 3.9e4.0
(m, 2H), 3.8e3.9 (m, 2H), 3.6e3.8 (m, 7H), 3.3e3.5 (m, 5H), 3.1e3.2
(m, 1H), 2.3e2.5 (m, 1H), 1.7e1.8 (m, 1H); 13C NMR (125 MHz, D2O)
1H), 2.14 (s, 1H) 1.8e1.9 (m, 1H); 13C NMR (125 MHz, D2O)
d 157.57,
d
153.63, 152.32, 116.06 (2C), 115.17 (2C), 100.51, 96.82, 84.39, 79.60,
139.74, 133.73, 129.09 (2C), 128.11 (2C), 127.19, 126.43 (2C), 115.19
(2C), 100.56, 96.67, 83.92, 78.33, 73.03, 72.04, 71.17, 70.86, 70.80,
68.63, 68.14, 66.30, 65.59, 5þ4.98, 49.90, 48.02, 40.38, 27.96. ESI/APCI
calculated for C30H45N4O11 [MH]þ: 637.3085; measured m/e:
637.3085.
73.00, 72.15, 71.15, 70.87, 70.72, 68.59, 68.20, 66.91, 65.50, 55.87,
54.96, 50.07, 48.00, 40.27, 28.88. ESI/APCI calculated for
C
25H43N4Oþ12 [MH]þ: 591.2877; measured m/e: 591.2879.
4.3. 600-O-(4-methylphenyl)kanamycin A (11b)
4.8. 600-O-(4-(1H-benzo[d]imidazole-2-yl)phenyl)kanamycin A
(11g)
The compound was synthesized as a light-brown solid following
the general procedure. 1H NMR (500 MHz, D2O)
d
7.08 (d, J ¼ 8.5 Hz,
1H), 6.83 (d, J ¼ 8.5 Hz, 1H), 5.50 (d, J ¼ 3.5 Hz, 1H), 5.05 (d,
J ¼ 3.5 Hz, 1H), 3.8e4.0 (m, 5H), 3.6e3.8 (m, 2H), 3.4e3.6 (m, 4H),
3.2e3.4 (m, 2H), 3.0e3.1 (m, 1H), 2.4e2.5 (m, 1H), 2.14 (s, 1H)
4-(1H-benzo[d]imidazole-2-yl)phenol was synthesized by
refluxing 1,2-diaminobenzene with 4-hydroxybenzaldehyde in the
presence of sodium metabisulfite [37]. For this, 0.475 g (0.25 mmol,
1 equiv) of sodium metabisulfite was added to a solution of 0.27 g
(0.25 mmol, 1 equiv) 1,2-diaminobenzene and 0.30 g (0.25 mmol, 1
equiv) of 4-hydroxybenzaldehyde in 10 mL DMF. The reaction
mixture was refluxed at 150 ꢁC for 24 h, and the solvent was
removed under reduced pressure. The residue was washed with
2 ꢂ 10 mL water followed by 2 ꢂ 5 mL DCM. Compound 11g was
synthesized as a white solid following the general procedure using
4-(1H-benzo[d]imidazole-2-yl)phenol as the substituted phenol.
1.8e1.9 (m, 1H); 13C NMR (125 MHz, D2O)
d 155.73, 131.57, 130.20
(2C), 114.78 (2C), 100.59, 96.24, 83.83, 78.15, 72.65, 72.07, 71.18,
70.79, 70.77, 68.64, 68.12, 66.35, 65.47, 54.94,þ49.90, 47.84, 40.36,
27.63, 19.53. ESI/APCI calculated for C24H47N4O12 [MH]þ: 575.2928;
measured m/e: 575.2927.
4.4. 600-O-phenylkanamycin A (11c)
This compound was synthesized as a white solid following the
1H NMR (500 MHz, D2O)
d
7.83 (d, J ¼ 8.0 Hz, 2H), 7.5e7.7 (m, 2H),
general procedure. 1H NMR (500 MHz, D2O)
6.9e7.0 (m, 3H), 5.49 (d, J ¼ 4.0 Hz, 1H), 5.05 (d, J ¼ 4.0 Hz, 1H),
d
7.2e7.3 (m, 2H),
7.3e7.4 (m, 2H), 7.09 (d, J ¼ 8.5 Hz, 2H), 5.58 (d, J ¼ 4.0 Hz, 1H), 5.11
(d, J ¼ 3.5 Hz, 1H), 4.2e4.3 (m, 3H), 3.8e4.0 (m, 5H), 3.7e3.8 (m,