Synthesis of biscoumarin and dihydropyran derivatives as two novel classes of potential anti-…
X-ray crystallography
11.520 (s, 1H), 11.305 (s, 1H), 8.035–8.077 (d, 2H),
7.624–7.667 (m, 2H), 7.419–7.440 (d, 4H), 7.126–7.146
(d, 2H), 6.854–6.876 (d, 2H), 6.069 (s, 1H), 4.014–4.066
(q, 2H), 1.406–1.440 (t, 3H). HRMS (ESI?): m/z: calcd
for [C27H20O7?Na?]: 479.1101; found: 479.1129.
Dihydropyran derivatives (5–8) were also synthesized ac-
cording to a reported procedure (Eshghi et al. 2012). A mixture
of 3,5-cyclohexanedione (or 1,1-dimethyl-3,5-cyclohexane-
dione) (10 mmol), 4-methylsulfanylbenzaldehyde (or 4-ni-
trobenzaldehyde, 4-isopropylbenzaldehyde, 3-bromo-4-
fluorobenzaldehyde) (10 mmol), malononitrile (10 mmol) and
4-(dimethylamino)pyridine (DMAP) (1 mmol) in ethanol
(100 mL) was refluxed for 2–3 h and then cooled to room
temperature. After filtering the precipitates, they were se-
quentially washed with ice-cooled water and ethanol and then
dried under a vacuum.
For X-ray diffraction experiments, single crystals of com-
pounds 1, 5 and 7 were both grown from methanol. The X-ray
diffraction data were collected on a Bruker SMART APEX II
CCD diffractometer equipped with a graphite monochromated
˚
Mo Ka radiation (k = 0.71073 A) by using the x-2h scan
technique at room temperature. The structure was solved by
direct methods using SHELXS-97 (Sheldrick 1997) and re-
fined using the full-matrix least squares method on F2 with
anisotropic thermal parameters for all non-hydrogen atoms by
using SHELXL-97. Hydrogen atoms were generated geomet-
rically. The crystal data and details concerning data collection
and structure refinement are given in Table 1. Molecular il-
lustrations were prepared using the XP package. Parameters in
CIF format are available as electronic supplementary publi-
cation from Cambridge Crystallographic Data Centre.
2-Amino-4-(4-methylsulfanylphenyl)-5-oxo-5,6,7,8-te-
trahydro-4H-chromene-3-carbonitrile (5): m.p. 224–
225 °C. IR (KBr pellet cm-1): 1681 (CO), 1651 (C=C),
Quantum chemical calculations
1
1214 (–O–). H NMR (DMSO-d6, d, ppm): 7.169–7.190
All calculations were carried out using the Gaussian 09
package (Frisch et al. 2009). Density functional theory
(DFT) (Kohn and Sham 1965), Becke’s three-parameter
hybrid function (B3LYP) (Becke 1993), and LYP correla-
tion function (Lee et al. 1988; Miehlich et al. 1989) were
used to fully optimize all the geometries on the energy
surface without constraints. To obtain precise results that are
in conjunction with experimental results, three basis sets,
namely 6-31G*, 6-31 ? G**, and 6-311G*, were tested.
Frequency calculations at the B3LYP (with basis sets
6-31G*) level of theory were carried out to confirm sta-
tionary points as minima and to obtain the zero-point en-
ergies and the thermal correlation data at 1 atm and 298 K.
(t, 2H), 7.087–7.107 (d, 2H), 7.029 (s, 2H), 4.149 (s, 1H),
2.590–2.621 (q, 2H), 2.499–2.516 (m, 3H), 2.216–2.311
(m, 2H), 1.864–1.981 (m, 2H). HRMS (ESI?): m/z: calcd
for [C17H16N2O2S?Na?]: 335.0825; found: 335.0832.
2-Amino-4-(4-nitrophenyl)-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carbonitrile (6): m.p. 234–235 °C. IR (KBr pel-
1
let cm-1): 1682 (CO), 1590 (C=C), 1209 (–O–). H NMR
(DMSO-d6, d, ppm): 8.156–8.178 (d, 2H), 7.454–7.475 (d,
2H), 7.199 (s, 2H), 4.366 (s, 1H), 2.624–2.654 (t, 2H),
2.255–2.330 (m, 2H), 1.913–1.978 (m, 2H). HRMS (ESI?):
m/z: calcd for [C16H13N3O4?Na?]: 334.0789; found:
334.0233.
2-Amino-4-(4-isopropylphenyl)-3-cyano-7,7-dimethyl-
5-oxo-4H-5,6,7,8-tetrahydrobenzo[b]pyran (7): m.p.
210–211 °C. IR (KBr pellet cm-1): 1675 (CO), 1606
(C=C), 1213 (–O–). 1H NMR (DMSO-d6, d, ppm):
7.149–7.169 (d, 2H), 7.037–7.057 (d, 2H), 6.964 (s, 2H),
4.135 (s, 1H), 2.822–2.856 (t, 1H), 2.503–2.521 (m, 1H),
2.237–2.277 (d, 1H), 2.139 (s, 1H), 2.092 (s, 1H), 1.191
(s, 3H), 1.174 (s, 3H), 1.046 (s, 3H), 0.977 (s, 3H). HRMS
(ESI?): m/z: calcd for [C21H24N2O2?Na?]: 359.1730;
found: 359.1788.
Minimal inhibitory concentration (MIC) assay
Based on the CLSI broth microdilution method, the deter-
mination of minimum inhibitory concentrations (MICs) via
microdilution assay was performed in sterilized 96-well
polypropylene microtiter plates (Sigma-Aldrich) in a final
volume of 200 lL. Bacteria were grown overnight in nutrient
broth. Mueller-Hinton (MH) broth (100 lL) containing bac-
teria (5 9 105 CFU/mL) was added to 100 lL of the culture
medium containing the test compound (0.12 lg/mL to
256 lg/mL in serial twofold dilutions). The plates were in-
cubated at 37 °C for 20 h in an incubator. About 50 lL of
0.2 % triphenyl tetrazolium chloride (TTC), a colorimetric
indicator, was added to each well of microtiter plates and
incubated at 35 °C for 1.5 h. The TTC-based MIC was de-
termined as the lowest concentration of oxacillin that showed
no red color change indicating complete growth inhibition.
2-Amino-4-(3-bromo-4-fluorophenyl)-3-cyano-7,7-dime-
thyl-5-oxo-4H-5,6,7,8-tetrahydrobenzo[b]pyran (8): m.p.
228–229 °C. IR (KBr pellet cm-1): 1683 (CO), 1601
(C=C), 1215 (–O–). 1H NMR (DMSO-d6, d, ppm):
7.431–7.453 (q, 1H), 7.291–7.334 (t, 1H), 7.187–7.221 (m,
1H), 7.109 (s, 2H), 4.247 (s, 1H), 2.527–2.530 (d, 2H),
2.233–2.73 (d, 1H), 2.114–2.154 (d, 1H), 1.039 (s, 3H),
0.963 (s, 3H). HRMS (ESI?): m/z: calcd for [C18H16-
BrFN2O2?Na?]: 413.0271; found: 413.0289.
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