6
J. Wang et al. / Bioorg. Med. Chem. Lett. xxx (2016) xxx–xxx
exhibited a broad array of potentiating efficacy. Compounds 9s,
0e and 10f were capable of enhancing the effect of TMZ in A549
cell line by the PF50 values of 1.9, 2.3 and 1.6, respectively.
In summary, a series of novel 5-fluorine-benzimidazole-4-car-
boxamide derivatives were designed, synthesized and biologically
evaluated as potent PARP-1 inhibitors. Representative compounds
temperature. The pH was adjusted to 6 with 30% sodium hydroxide solution,
then filtered and the filtrate was extracted with ethyl acetate (100 mL ꢁ 3),
and washed with brine (150 mL ꢁ 2). The organic layer was dried and
concentrated in vacuo to give the intermediate 3 as yellow solid in 91.40%
yield. (iii) To a solution of 2,6-difluoro-3-nitrobenzamide (0.25 mol) in ethanol
1
(
300 mL) was added ammonium hydroxide (25 mL). The reaction mixture was
stirred at room temperature overnight and the precipitate was collected by
filtration, washed with isopropanol and dried in vacuum to give 4 31.5 g as
1
0e and 11f displayed potent in vitro PARP-1 enzymatic inhibition
yellow solid, yield 77.6%. (iv) A suspension of 2-amino-6-fluoro-3-
nitrobenzamide (0.05 mol) in ethanol (100 mL) was reduced by hydrogen in
the presence of palladium on carbon (10%, 1.00 g). After stirring at room
temperature for 12 h, the reaction mixture was filtered. Solvent was removed
under reduced pressure and the residue was subjected to silica gel column
chromatography using dichloromethane/methanol (3:1) as eluent to give 5
and potent enhancement of cellular growth inhibition. More
importantly, Compound 10f exhibited a significant IC50 value of
7
synergic efficacy combined with temozolomide with PF50 values
of 1.6 against A549 cell line. Further pharmacokinetic evaluation
is ongoing and will be reported in the near future.
.4 nM in cellular assay against HCT116 cell line and a profound
5.00 g as light yellow solid, yield 58.9%. (v) To a solution of 3-pipecolinic acid
(
0.06 mol) and 2,3-diamino-6-fluorobenzamide (0.06 mol) in DMF (100 mL)
was treated with PyBOP (0.06 mol) and N,N-diisopropylethylamine (0.18 mol).
The reaction mixture was stirred at room temperature overnight. The solvent
was removed using high vacuum. The residue was subjected to flash column
chromatography using methylene chloride/methanol (30:1) to give the
intermediate 6 as a white solid. The intermediate 6 was dissolved in glacial
acetic acid (30 mL) and refluxed for 4 h until the reaction was complete
Acknowledgments
This work was supported by the National Natural Science
Foundation of China (Grant No. 81502928), Outstanding Scientific
and Technological Innovation Team of Jiangsu Province of
China in 2015 and Fundamental Research Funds for the Central
Universities (No. 2015PY015).
(
monitoring by TLC). The solvent was removed and the solid residue was
purified by column chromatography using methylene chloride/methanol
80:1) as eluent to give pure 7a–7e in 50–72% yield. (vi) A solution of 7a–7e
(
(25 mmol) in methanol (100 mL) was reduced with hydrogen in the presence
of palladium on carbon (10%, 1.00 g). After stirring at room temperature for
12 h, the reaction mixture was filtered, and the filtrate was concentrated to
give pure target compounds 8a–8e in 52–80% yield.
References and notes
17. General procedure for the synthesis of the target compounds 9a–9y: (i) A solution
of 8a–8e (2 mmol) in MeOH (10 mL) was stirred with formaldehyde, acetone or
propionaldehyde at room temperature overnight. Sodium cyanoborohydride
was added and the solution stirred at room temperature for 3 h. After
concentration, the residue was purified by column chromatography using
methylene chloride/methanol (80:1 to 20:1) as eluent to give the target
compounds 9a–9t in 60–94% yield. (ii) To a solution of 8a–8e (2 mmol) in
dichloromethane (10 mL) was added trimethylamine and acetylchloride at
1
2
3
.
.
.
4
5
.
.
0
°C. The mixture was stirred at room temperature for 2 h and purified by
column chromatography using methylene chloride/methanol (80:1 to 20:1) as
eluent to give the target compounds 9u–9y in 82–90% yield.
6.
7.
8.
9.
18. General procedure for the synthesis of the target compounds 10a–10f: (i) To a
solution of 2,3-diamino-6-fluorobenzamide (8.80 mmol) in methanol was
added the intermediate aromatic aldehyde (8.80 mmol) and NaHSO
8.80 mmol). The mixture was stirred at reflux temperature for 12 h, the
3
(
solid was collected by filtration and washed with methanol to give the target
compounds 10a–10e in 40–67% yield. (ii) To a solution of 5 (8.87 mmol) in
methanol (20 mL) was added the intermediate 4-(N-Boc-piperidine)
1
benzaldehyde (8.87 mmol) and NaHSO
3
(8.87 mmol). The mixture was
1
stirred at reflux temperature for 12 h, the solid was collected by filtration
and washed with methanol to give intermediate 11 in 64% yield. A solution of
11 (5.69 mmol) in a mixture of THF (10 mL) and methanol (10 mL) was treated
1
with concentrated HCl (5 mL) and stirred at room temperature for 2 h. The
resulting precipitate was collected by filtration and dried to give target
compound 10f in 62.5% yield.
1
1
9. Analytical data for selected final compound 8b: Mp: 226–228 °C. 1H-NMR
1
(
1
3
300 MHz, DMSO-d
6
) d (ppm): 1.52 (s, 3H, –CH
.73–1.81 (m, 2H, –CH –), 2.33–2.39 (m, 1H, –CH–), 2.79–2.83 (m, 1H, NCH–),
.02–3.08 (m, 1H, –NCH–), 7.05 (dd, J = 12.09, 8.81 Hz, 1H, ArH), 7.60 (q,
3
), 1.60–1.62 (m,1H, –CH–),
1
2
1
6. General procedure for the synthesis of the target compounds 8a–8e: (i) A solution
of 2,6-difluorobenzoic acid (0.32 mol) in thionyl chloride (100 mL) was heated
to reflux for 2 h. The resulting solution was concentrated and acid chloride
intermediate was used in the next step without additional purification. To a
solution of the acid chloride in anhydrous THF (100 mL) was added ammonium
hydroxide (79 mL) at 0 °C. After stirring at room temperature for 0.5 h, the
reaction mixture was concentrated under reduced pressure. Then the reaction
mixture was poured into cooled water (50 mL), extracted with ethyl acetate
13
2 6
J = 4.35 Hz, 1H, ArH), 7.70 (s, 1H, –CONH ). C NMR (75 MHz, DMSO-d ) d
(
1
2
ppm): 22.08, 22.97, 36.43, 43.83, 64.97, 111.94, 118.14, 134.00, 136.64,
54.96, 155.09, 158.21, 163.78. HRMS-ESI m/z [M+H] : calcd for C13H16FN O:
4
63.1308, found: 263.1304.
+
2
0. Analytical data for selected final compound 10f: Mp: 232–234 °C. 1H NMR
(
7
1
300 MHz, DMSO-d
6
) d (ppm): 3.22 (s, 4H, –(CH
.23 (d, J = 9.06 Hz, 2H, ArH), 7.38 (t, J = 10.74 Hz, 1H, ArH), 7.81 (q, J = 4.32 Hz,
H, ArH), 8.04 (s, 1H, piperazine-H), 8.28 (d, J = 8.88 Hz, 2H, ArH), 8.35 (s, 1H,
2 2 2 2
) –), 3.67 (s, 4H, –(CH ) –),
(
100 mL ꢁ 3), and washed with brine (150 mL ꢁ 2). The organic layer was dried
and concentrated to give the intermediate 2 in 90% yield which used in next
step without purification. (ii) To solution of 2,6-difluorobenzamide
0.28 mol) in concentrated sulfuric acid (90 mL) was added fuming nitric
acid (12 mL) by dropwise under 0 °C. The mixture was stirred for 2 h at room
13
2 6
imidazole-H), 9.51 (s, 2H, CONH ). C NMR (75 MHz, DMSO-d ) d (ppm):
4
1
2.16, 43.56, 110.86, 111.17, 111.53, 113.82, 114.36, 115.98, 116.11, 128.93,
a
+
30.35, 151.24, 152.91, 154.66, 157.91, 162.55. HRMS-ESI m/z [M+H] : calcd
19FN O: 340.1574, found: 340.1541.
(
for C18
H
5