Protein Kinase CK2 Inhibitors
3-Hydroxy-8-methoxy-dibenzo[b,d]pyran-6-one (9):[33] A solution
of 24 (3.4 g, 0.015 mol), resorcinol (3.2 g, 0.029 mol) and NaOH
(1.2 g, 0.029 mol) in water (15 mL) was refluxed for 20 min. Then a
5% aqueous solution of CuSO4 (6.2 mL) was added to the mixture,
and the reaction was heated at reflux for an additional 1 h. Com-
pletion of the reaction was determined by TLC (CHCl3/MeOH, 9:1).
The suspension obtained was filtered, and the solid residue was
dried to give 9 (white solid, 1.8 g, 51%): 1H NMR (300 MHz,
(CD3)2SO): d=10.21 (s, 1H, OH), 8.21 (d, J=8.9 Hz, 1H, H10), 8.09
(d, J=8.4 Hz, 1H, H1), 7.60 (d, J=2.7 Hz, 1H, H7), 7.49 (dd, J=8.9,
2.7 Hz, 1H, H9), 6.83 (dd, J=8.4, 2.4 Hz, 1H, H2), 6.75 (d, J=2.4 Hz,
1H, H4), 3.89 ppm (s, 3H, OCH3); 13C NMR (300 MHz, (CD3)2SO): d=
160.4, 158.8, 158.4, 151.1, 128.4, 124.1, 123.9, 123.5, 119.9, 113.0,
110.7, 109.4, 102.7, 55.5 ppm; HRMS: m/z [M+H]ꢁ calcd for
C14H10O4: 241.0506, found: 241.0488.
residue was dried to give a mixture of 15 and 16. The two prod-
ucts were separated by column chromatography on silica gel
(CHCl3/MeOH, 9:1).
Compound 15 (yellow solid, 0.078 g, 13%): 1H NMR (300 MHz,
(CD3)2CO): d=8.81 (s, 1H, H1), 8.37 (d, J=8.9 Hz, 1H, H10), 7.62 (d,
J=2.8 Hz, 1H, H7), 7.53 (dd, J=8.9, 2.8 Hz, 1H, H9), 7.03 (s, 1H,
H4), 4.01 ppm (s, 3H, OCH3); 13C NMR (300 MHz, (CD3)2SO): d=
161.7, 161.6, 155.7, 155.0, 137,3, 128.9, 128.7, 126.0, 123.0, 122.8,
113.5, 112.5, 108.0, 57.9 ppm; HRMS: m/z [M+H]ꢁ calcd for
C14H9NO6: 286.0357, found: 286.0383.
Compound 16 (yellow solid, 0.41 g, 59%): 1H NMR (300 MHz,
(CD3)2CO): d=9.05 (s, 1H, H1), 8.45 (d, J=8.9 Hz, 1H, H10), 7.72 (d,
J=2.8 Hz, 1H, H7), 7.59 (dd, J=8.9, 2.8 Hz, 1H, H9), 4.01 ppm (s,
3H, OCH3); 13C NMR (300 MHz, (CD3)2SO): d=171.9, 159.2, 158.2,
151.6, 145.4, 135.8, 126.6, 124.5, 124.1, 121.3, 119.9, 111.3, 106.4,
55.6 ppm; HRMS: m/z [M+H]ꢁ calcd for C14H8N2O8: 331.0208,
found: 331.0195.
3,8-Dihydroxy-dibenzo[b,d]pyran-6-one (8): A suspension of 9
(1.8 g, 7.4 mmol) in an azeotropic mixture of HBr (40 mL) and
AcOH (80 mL) was refluxed for 11 h. Completion of the reaction
was determined by TLC (CHCl3/MeOH, 9:1). The mixture was put
into the ice (5 g) until complete precipitation of the desired prod-
uct, which was then isolated by filtration and dried (white solid,
1.25 g, 74%): 1H NMR (300 MHz, (CD3)2SO): d=8.11 (d, J=8.8 Hz,
1H, H10), 8.02 (d, J=8.7 Hz, 1H, H1), 7.51 (d, J=2.6 Hz, 1H, H7),
7.32 (dd, J=8.8, 2.6 Hz, 1H, H9), 6.81 (dd, J=8.7, 2.4 Hz, 1H, H2),
6.72 ppm (d, J=2.4 Hz, 1H, H4); 13C NMR (300 MHz, (CD3)2SO): d=
160.5, 158.5, 156.9, 150.8, 126.8, 124.1, 123.9, 123.2, 120.1, 113.4,
112.5, 109.7, 102.3 ppm; HRMS: m/z [M+H]ꢁ calcd for C13H8O4:
227.0350, found: 227.0334.
3,8-Dihydroxy-2,4-dinitro-6H-dibenzo[b,d]pyran-6-one (14):
A
50 mL flask was charged with excess pyridine chlorohydrate (0.7 g,
6 mmol) and 16 (0.2 g, 0.6 mmol), and the mixture was heated to
2108C to achieve complete solubilization of pyridine chlorohydrate
and then stirred at this temperature for 4 h. The reaction mixture
was cooled during which pyridine chlorohydrate resolidified. EtOAc
(20 mL) was added to the suspension, and the organic solution
was washed with water (5ꢁ20 mL) to removed excess pyridine
chlorohydrate. The organic phase was separated, dried (Na2SO4), fil-
tered and concentrated in vacuo. The crude was purified by
column chromatography on silica gel (CHCl3/MeOH, 9:1) to give 14
(yellow solid, 60 mg, 31%): 1H NMR (300 MHz, (CD3)2CO): d=8.96
(s, 1H, H1), 8.56 (d, J=8.9 Hz, 1H, H10), 7.69 (d, J=2.8 Hz, 1H, H7),
7.43 ppm (dd, J=8.9, 2.8 Hz, 1H, H9); 13C NMR (300 MHz,
(CD3)2SO): d=158.7, 157.4, 154.7, 149.4, 135.2, 131.1, 130.5, 130.0,
129.3, 127.6, 127.4, 121.7, 116.6 ppm; HRMS: m/z [M+H]ꢁ calcd for
C13H6N2O8: 317.2294, found: 317.2369.
3,8-Dimethoxy-dibenzo[b,d]pyran-6-one (10): K2CO3 (31 g, 0.225
mol) and dimethylsulfate (26.5 g, 0.21 mol) were added to a solu-
tion of 10 (0.5 g, 2.1 mmol) in acetone (300 mL). The reaction mix-
ture was refluxed for 40 min. Completion of the reaction was de-
termined by TLC (CHCl3/MeOH, 9:1). The solid salts were removed
by filtration, and the filtrate was concentrated in vacuo. The solid
residue was solubilized in EtOAc (30 mL) and washed with water
(3ꢁ50 mL). The organic phase was separated, dried (Na2SO4), fil-
tered and concentrated in vacuo (white solid, 0.102 g, 19%):
1H NMR (300 MHz, CDCl3): d=7.90 (d, J=8.9 Hz, 1H), 7.84 (d, J=
8.7 Hz, 1H), 7.74 (d, J=2.8 Hz, 1H), 7.35 (dd, J=8.9, 2.8 Hz, 1H),
6.88 (dd, J=8.7, 2.6 Hz, 1H), 6.84 (d, J=2.6 Hz, 1H), 3.95 (s, 3H),
3.87 ppm (s, 3H); 13C NMR (300 MHz, CDCl3): d=161.6, 160.7,
159.2, 151.7, 128.6, 124.5, 123.1, 122.8, 121.0, 112.4, 111.3, 111.0,
101.9, 55.7, 55.7 ppm; HRMS: m/z [M+H]+ calcd for C15H12O4:
257.0808, found: 257.0790
2-Nitro-resorcinol (25): Resorcinol (5 g, 0.05 mol) was dissolved in
hot H2SO4 (96%, 36 mL, 33.84 g, 0.35 mol). After 5 min, resorci-
nol·H2SO4 began to precipitate out of solution. The suspension was
cooled to RT with formation of a white precipitate. The suspension
was treated with HNO3 (65%, 2.84 g, 0.05 mol) and H2SO4 (9.05 g,
0.09 mol) under strong stirring until complete solubilization was
observed. Stirring was then suspended and ice (60 g per 100 g of
solution) was added slowly. The reaction mixture was refluxed, and
the product was obtained by distillation. The product was further
purified by crystallization from abs EtOH to give 25 as red needles
(3.8 g, 60%): 1H NMR (300 MHz, (CD3)2CO): d=7.40 (t, J=8.4 Hz,
1H, H5), 6.61 ppm (d, J=8.4 Hz, 2H, H4 and H6); 13C NMR
(300 MHz, (CD3)2SO): d=154.6, 154.6, 137.8, 122.9, 109.5,
109.5 ppm; HRMS: m/z [M+H]ꢁ calcd for C6H5NO4: 154.0146,
found: 154.0157.
3,8-Dihydroxy-2,4,7,9-tetranitro-6H-dibenzo[b,d]pyran-6-one
(19): A solution of 11 (0.5 g, 2.2 mmol) in AcOH (25 mL) was treat-
ed with HNO3 (65%, 0.83 g, 13.2 mmol) and heated at 508C for 4 h.
Completion of the reaction was determined by TLC (EtOAc/
n-hexane/MeOH, 7:2:1). Then the solvent was evaporated in vacuo,
and the residue was crystallized from AcOH (yellow solid, 0.2 g,
1
3-Hydroxy-4-nitro-dibenzo[b,d]pyran-6-one (17): A solution of 2-
bromo-benzoic acid (1 g, 0.005 mol), 2-nitro-resorcinol (1 g,
0.006 mol) and NaOH (0.4 g, 0.010 mol) in water (20 mL) was re-
fluxed for 30 min. Then a 10% aqueous solution of CuSO4 (0.5 mL)
was added to the mixture, and the reaction was refluxed for an ad-
dition 1 h. Completion of the reaction was determined by TLC
(CHCl3/acetone, 1:1). The suspension was filtered, and the solid res-
idue was dried in an oven at 308C. Purification by column chroma-
tography on silica gel (CHCl3/MeOH, 9:1) gave the title compound
22%): H NMR (300 MHz, (CD3)2CO): d=9.51 (s, 1H, H10), 9.49 ppm
(s, 1H, H1); 13C NMR (300 MHz, (CD3)2CO): d=154.9, 149.7, 149.0,
147.7, 142.6, 134.4, 126.8, 125.7, 124.5, 123.5, 122.4, 119.0,
112.0 ppm; HRMS: m/z [M+H]ꢁ calcd for C13H4N4O12: 407.0107,
found: 407.0173.
3-Hydroxy-8-methoxy-2-nitro-6H-dibenzo[b,d]pyran-6-one (15)
and 3-hydroxy-8-methoxy-2,4-dinitro-6H-dibenzo[b,d]pyran-6-
one (16): A solution of 10 (0.5 g, 2.1 mmol) in AcOH (12 mL) was
treated with HNO3 65% (0.27 g, 4.3 mmol) and heated at 508C for
4 h. Completion of the reaction was determined by TLC (CHCl3/
MeOH, 9:1). The suspension obtained was filtered, and the solid
1
(white solid, 0.2 g, 16%): H NMR (300 MHz, (CD3)2CO): d=8.16 (dd,
J=8.9, 2.7 Hz, 1H, H7), 7.82 (d, J=9.0 Hz, 1H, H1), 7.53–7.50 (m,
2H, H9, H10), 7.37–7.32 (m, 1H, H8), 6.96 ppm (d, J=9.0 Hz, 1H,
ChemMedChem 2011, 6, 2273 – 2286
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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