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82.48, 82.26, 74.24, 73.76. MS m/z 287 (M þ 1). ESI-HRMS calcd for 2-(4-((4-Chlorophenyl)buta-1,3-diyn-1-yl)benzylidene)hydrazine-1-
C18H15N4þ ([M þ H]þ) 287.1291; found: 287.1286.
carboximidamide (6g)
Off white solid, m.p. 202–205 ꢁC, yield 45%. 1H-NMR (DMSO-d6,
400 MHz): d 5.92 (s, 2H, NH2), 6.21 (s, 2H, NH2), 7.51–7.56 (m, 4H,
2-(4-((2-Fluorophenyl)buta-1,3-diyn-1-yl)benzylidene)hydrazine-1-
Ar-H), 7.64 (d, 2H, J ¼ 8.3 Hz, Ar-H), 7.74 (d, 2H, J ¼ 8.3 Hz, Ar-H),
7.99 (s, 1H, N¼CH). 13C-NMR (DMSO-d6, 100 MHz): d 159.84,
carboximidamide (6 b)
Off white solid, m.p. 218–220 ꢁC, yield 76%. 1H-NMR (DMSO-d6,
142.21, 137.82, 134.86, 134.18, 132.62, 129.19, 126.74, 119.44,
82.83, 81.22, 74.69, 74.33. MS m/z 321 (M þ 1). ESI-HRMS calcd for
400 MHz): d 5.83 (s, 2H, NH2), 6.17 (s, 2H, NH2), 7.27–7.71 (m, 6H,
C18H14ClN4þ ([M þ H]þ) 321.0902; found: 321.0909.
Ar-H), 7.75 (d, 2H, J ¼ 8.4 Hz, Ar-H), 7.99 (s, 1H, N¼CH). 13C-NMR
1
(DMSO-d6, 100 MHz): d 162.97 (d, Jc-f ¼ 249.6 Hz), 160.90, 141.72,
3
138.72, 134.35, 132.57, 132.25 (d, Jc-f ¼ 8.0 Hz), 126.37, 125.05 (d,
2-(4-((2-Bromophenyl)buta-1,3-diyn-1-yl)benzylidene)hydrazine-1-
carboximidamide (6h)
2
2
4Jc-f ¼ 3.5 Hz), 118.50, 115.92 (d, Jc-f ¼ 20.0 Hz), 109.14 (d, Jc-f
¼
15.2 Hz), 83.64, 78.40, 75.43, 73.85. MS m/z 305 (M þ 1). ESI-HRMS
calcd for C18H14FN4þ ([M þ H]þ) 305.1197; found: 305.1195.
Off white solid, m.p. 217–219 ꢁC, yield 72%. 1H-NMR (DMSO-d6,
400 MHz): d 5.69 (s, 2H, NH2), 6.06 (s, 2H, NH2), 7.39–7.78 (m, 6H,
Ar-H), 7.58 (d, 2H, J ¼ 8.4 Hz, Ar-H), 7.99 (s, 1H, N¼CH). 13C-NMR
(DMSO-d6, 100 MHz): d 161.68, 142.02, 139.40, 135.20, 133.14,
133.05, 131.99, 128.50, 126.78, 125.79, 123.23, 118.82, 84.56, 80.73,
78.13, 74.41. MS m/z 365 (M þ 1). ESI-HRMS calcd for
C18H14ClN4þ ([M þ H]þ) 365.0396; found: 365.0394.
2-(4-((3-Fluorophenyl)buta-1,3-diyn-1-yl)benzylidene)hydrazine-1-
carboximidamide (6c)
Off white solid, m.p. 186–190 ꢁC, yield 69%. 1H-NMR (DMSO-d6,
400 MHz): d 5.84 (s, 2H, NH2), 6.13 (s, 2H, NH2), 7.34–7.55 (m, 4H,
Ar-H), 7.58 (d, 2H, J ¼ 8.4 Hz, Ar-H), 7.74 (d, 2H, J ¼ 8.4 Hz, Ar-H),
1
7.99 (s, 1H, N¼CH). 13C-NMR (DMSO-d6, 100 MHz): d 161.79 (d, Jc-f
2-(4-((3-Bromophenyl)buta-1,3-diyn-1-yl)benzylidene)hydrazine-1-
carboximidamide (6i)
3
¼ 243.8 Hz), 161.08, 141.59, 138.82, 132.58, 131.14 (d, Jc-f
¼
¼
3
2
Off white solid, m.p. 196–198 ꢁC, yield 68%. 1H-NMR (DMSO-d6,
400 MHz): d 5.95 (s, 2H, NH2), 6.24 (s, 2H, NH2), 7.38–7.83 (m, 4H,
Ar-H), 7.56 (d, 2H, J ¼ 8.4 Hz, Ar-H), 7.75 (d, 2H, J ¼ 8.4 Hz, Ar-H),
7.99 (s, 1H, N¼CH). 13C-NMR (DMSO-d6, 100 MHz): d 160.70,
141.82, 138.57, 134.45, 132.94, 132.58, 131.50, 130.93, 126.43,
122.83, 121.81, 118.66, 83.21, 80.51, 74.95, 74.04. MS m/z 365
(M þ 1). ESI-HRMS calcd for C18H14ClN4þ ([M þ H]þ) 365.0396;
found: 365.0391.
8.8 Hz), 128.86, 126.35, 122.52 (d, Jc-f ¼ 9.8 Hz), 118.99 (d, Jc-f
2
23.2 Hz), 118.48, 117.43 (d, Jc-f ¼ 20.8 Hz), 83.12, 80.78, 74.58,
73.96. MS m/z 305 (M þ 1). ESI-HRMS calcd for C18H14FN4þ
([M þ H]þ) 305.1197; found: 305.1199.
2-(4-((4-Fluorophenyl)buta-1,3-diyn-1-yl)benzylidene)hydrazine-1-
carboximidamide (6d)
Off white solid, m.p. 206–210 ꢁC, yield 78%. 1H-NMR (DMSO-d6,
400 MHz): d 5.91 (s, 2H, NH2), 6.22 (s, 2H, NH2), 7.27–7.75 (m, 4H,
Ar-H), 7.54 (d, 2H, J ¼ 8.4 Hz, Ar-H), 7.74 (d, 2H, J ¼ 8.4 Hz, Ar-H),
2-(4-((4-Bromophenyl)buta-1,3-diyn-1-yl)benzylidene)hydrazine-1-
carboximidamide (6j)
1
7.99 (s, 1H, N¼CH). 13C-NMR (DMSO-d6, 100 MHz): d 162.70 (d, Jc-f
Off white solid, m.p. 227–230 ꢁC, yield 50%. 1H-NMR (DMSO-d6,
400 MHz): d 5.93 (s, 2H, NH2), 6.22 (s, 2H, NH2), 7.55–7.57 (m, 4H,
Ar-H), 7.65 (d, 2H, J ¼ 8.4 Hz, Ar-H), 7.74 (d, 2H, J ¼ 8.4 Hz, Ar-H),
8.00 (s, 1H, N¼CH). 13C-NMR (DMSO-d6, 100 MHz): d 161.12,
142.37, 138.92, 134.69, 132.99, 132.49, 126.92, 124.05, 120.25,
119.27, 83.47, 81.66, 75.30, 74.64. MS m/z 365 (M þ 1). ESI-HRMS
calcd for C18H14ClN4þ ([M þ H]þ) 365.0396; found: 365.0395.
3
¼ 248.3 Hz), 160.76, 141.86, 138.45, 134.95 (d, Jc-f ¼ 8.8 Hz),
4
2
132.51, 126.42, 118.90, 117.05(d, Jc-f ¼ 3.3 Hz), 116.34 (d, Jc-f
¼
22.2 Hz), 82.36, 81.29, 74.26, 73.54. MS m/z 305 (M þ 1). ESI-HRMS
calcd for C18H15FN4þ ([M þ H]þ) 305.1197; found: 305.1189.
2-(4-((2-Chlorophenyl)buta-1,3-diyn-1-yl)benzylidene)hydrazine-1-
carboximidamide (6e)
Off white solid, m.p. 207–210 ꢁC, yield 75%. 1H-NMR (DMSO-d6,
400 MHz): d 5.95 (s, 2H, NH2), 6.23 (s, 2H, NH2), 7.38–7.76 (m, 8H,
Ar-H), 8.00 (s, 1H, N¼CH). 13C-NMR (DMSO-d6, 100 MHz): d 161.31,
142.23, 139.12, 136.04, 135.02, 133.06, 131.85, 130.02, 128.01,
126.86, 121.01, 119.05, 84.51, 79.03, 78.81, 74.43. MS m/z
321(M þ 1). ESI-HRMS calcd for C18H14ClN4þ ([M þ H]þ) 321.0902;
found: 321.0906.
2-(4-(m-Tolylbuta-1,3-diyn-1-yl)benzylidene)hydrazine-1-carboximi-
damide (6k)
Off white solid, m.p. 202–204 ꢁC, yield 63%. 1H-NMR (DMSO-d6,
400 MHz): d 2.32 (s, 3H, CH3), 5.72 (s, 2H, NH2), 6.09 (s, 2H, NH2),
7.29–7.43 (m, 4H, Ar-H), 7.54 (d, 2H, J ¼ 8.2 Hz, Ar-H), 7.72 (d, 2H,
J ¼ 8.2 Hz, Ar-H), 7.98 (s, 1H, N¼CH). 13C-NMR (DMSO-d6, 100 MHz):
d 161.26, 142.30, 138.88, 138.83, 133.08, 132.94, 131.23, 129.99,
129.28, 126.85, 120.84, 119.42, 82.96, 82.73, 74.84, 73.91, 21.15. MS
m/z 301 (M þ 1). ESI-HRMS calcd for C19H16N4þ ([M þ H]þ)
301.1448; found: 301.1452.
2-(4-((3-Chlorophenyl)buta-1,3-diyn-1-yl)benzylidene)hydrazine-1-
carboximidamide (6f)
Off white solid, m.p. 198–201 ꢁC, yield 81%. 1H-NMR (DMSO-d6,
400 MHz): d 5.83 (s, 2H, NH2), 6.12 (s, 2H, NH2), 7.45–7.50 (m, 8H,
Ar-H), 7.99 (s, 1H, N¼CH). 13C-NMR (DMSO-d6, 100 MHz): d 161.09,
141.57, 138.83, 133.46, 132.57, 131.67, 131.15, 130.78, 130.08,
126.33, 122.58, 118.44, 83.23, 80.58, 74.88, 73.96. MS m/z 321
(M þ 1). ESI-HRMS calcd for C18H14ClN4þ ([M þ H]þ) 321.0902;
found: 321.0901.
Evaluation of antibacterial activity in vitro
Test bacteria were grown to mid-log phase in Mueller–Hinton
broth (MHB) or Tryptone Soya Broth (TSB) and diluted 1000-fold
in the same medium. Bacteria (105 CFU/mL) were inoculated into
MHB or TSB and dispensed at 0.2 ml/well into a 96-well microtiter
plate. As positive controls, gatifloxacin, moxifloxacin, norfloxacin,