Molecules 2016, 21, 955
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found to bind, the calculated binding energy was 1.1–1.8 kcal/mol lower for AChE compared to BChE.
These results are consistent with the slight selectivity for AChE compared to BChE that was observed
for three out of the four most active compounds in the inhibition studies.
3. Materials and Methods
3.1. General Information
All melting points were taken on a Stuart melting point apparatus SMP30 (Staffordshire, UK).
NMR spectra were obtained using Jeol ECA 400 (400 MHz) and EX 270 (270 MHz) NMR spectrometers
(Jeol Ltd., Akishima, Tokyo, Japan) with tetramethylsilane as the internal standard. All chemical
shifts are reported in ppm. MS analysis was performed on an Agilent 6500 series accurate mass
Q-TOF (Agilent Technologies, Santa Clara, CA, USA) Analytical thin-layer chromatography (TLC)
was carried out on pre-coated aluminum silica gel sheets (Kieselgel 60 F254) from Merck (Darmstadt,
Germany). Column chromatography was performed with silica gel 60 (230–400 mesh) from Merck.
Human recombinant AChE and equine BChE were purchased from Sigma-Aldrich (St. Louis, MO,
USA). All other chemicals were purchased from Sigma-Aldrich or Merck and were of analytical grade.
The Lipinski rule of five parameters of the synthesised compounds were determined using Discovery
Studio v3.1 (Accelrys Inc., San Diego, CA, USA).
3.2. Synthesis of Chalcones 1–14
A mixture of the corresponding acetophenone (1 equiv) and benzaldehyde (1 equiv) in EtOH
(5 mL/1 mmol of acetophenone) was stirred at room temperature for 30 min. Then, a solution of
50% w/w aqueous KOH (1 mL/1 mmol) was added. The reaction mixture was stirred at rt until all
benzaldehyde was consumed when monitored on TLC. Afterwards, the mixture was poured into
ice-water acidified with 3 N HCl. In cases in which the chalcones precipitated, they were filtered,
purified using column chromatography, and crystallised from ethanol (yields: 65%–90%).
1
˝
˝
2 -Hydroxychalcone (1). Yellow crystals, mp 89–90 C, lit. 89–90 C [29]; for NMR data see ref. [30].
1
˝
˝
2 -Hydroxy-4-methylchalcone (
2
) Yellow needles, mp 117–118 C, lit. 116–117 C [31]; for NMR data see
1
δ
˝ ˝
3
). Yellow needles, mp 138–139 C, lit. 138–139 C [32]; 1H-NMR (400 MHz,
4-Bromo-2 -hydroxychalcone (
CDCl3):
12.67 (s, 1H, OH), 7.80 (dd, J = 8.0, 1.5 Hz, 1H, H-61), 7.73 (d, J = 16.0 Hz, 1H, Hβ), 7.53 (d,
J = 16.0 Hz, 1H, Hα), 7.47 (d, J = 8.1 Hz, 2H, H-2, H-6), 7.41 (d, J = 7.8 Hz, 2H, H-3, H-5), 7.40 (m, 1H,
H-41), 6.94 (dd, J = 8.0, 1.5 Hz, 1H, H-31), 6.85 (m, 1H, H-51); 13C-NMR (100 MHz, CDCl3):
δ 193.44,
163.65, 143.96, 136.56, 133.53, 132.31, 129.97, 129.62, 125.27, 120.71, 119.94, 118.92, 118.70.
1
˝
˝
4-Chloro-2 -hydroxychalcone (
4
). Yellow needles, mp 145–146 C, lit. 148–151 C [29]; for NMR data see
21-Hydroxy-4-(dimethylamino)chalcone ( ). Orange powder, mp 170–171 ˝C, lit. 172 ˝C [33]; for NMR
5
21-Hydroxy-4-methoxychalcone ( ). Orange needles, mp 92–93 ˝C, lit. 92–94 ˝C [29]; for NMR data see
6
1
˝ ˝
2-Bromo-2 -hydroxychalcone (7 ,
). Yellow needles, mp 104–105 C, lit. 103–104 C [32]; 1H-NMR (400 MHz
1
CDCl3): δ 12.63 (s, 1H, OH), 8.12 (d, J = 15.3 Hz, 1H, Hβ), 7.77 (dd, J = 8.1, 1.8 Hz, 1H, H-6 ), 7.61 (dd,
J = 8.1, 1.8 Hz, 1H, H-3), 7.51 (dd, J = 8.2, 1.9 Hz, 1H, H-41), 7.44 (d, J = 15.4 Hz, 1H, Hα), 7.38 (m,
1H, H-5), 7.25 (t, J = 7.3 Hz, 1H, H-6), 7.13 (m, 1H, H-4), 6.90 (dd, J = 8.0, 1.8 Hz, 1H, H-31), 6.82 (m,
1H, H-51); 13C-NMR (100 MHz, CDCl3):
128.03, 127.81, 126.16, 122.93, 119.90, 118.97, 118.68.
δ 193.42, 163.66, 143.65, 136.61, 134.70, 133.67, 131.69, 129.78,