C.-T. Yen et al. / Bioorg. Med. Chem. Lett. 22 (2012) 4018–4022
17. Mondal, M.; Puranik, V. G.; Argade, N. P. J. Org. Chem. 2006, 71, 4992.
4021
compounds, as well as diphenyleneiodonium (DPI) and phenyl-
1
8. Sittisombut, C.; Boutefnouchet, S.; Trinh Van-Dufat, H.; Tian, W.; Michel, S.;
Koch, M.; Tillequin, F.; Pfeiffer, B.; Pierre, A. Chem. Pharm. Bull. 2006, 54, 1113.
9. Yen, C.-T.; Nakagawa-Goto, K.; Hwang, T.-L.; Wu, P. C.; Morris-Natschke, S. L.;
Lai, W.-C.; Bastow, K. F.; Chang, F.-R.; Wu, Y.-C.; Lee, K.-H. Bioorg. Med. Chem.
Lett. 2010, 1037, 20.
methylsulfonyl fluoride (PMSF), included as positive controls for
superoxide anion generation and elastase release, respectively.
Xanthone 4 showed a selective inhibitory effect toward superox-
1
ide anion generation with an IC50 value of 5.84 lg/mL, while com-
2
0. Castanheiro, R. A. P.; Silva, A. M. S.; Campos, N. A. N.; Nascimento, M. S. J.; Pinto,
pounds 5 and 6 exhibited weak activity in both anti-inflammatory
assays. Among compounds 7–21, prenylxanthones 7–13 demon-
strated weaker effects than pyranoxanthones 14–21 in response
to superoxide anion generation and elastase release. Linear
pyranoxanthone 14 was the most active compound, with IC50 val-
ues of 0.46 and 0.64 lg/mL against superoxide anion generation
and elastase release, respectively, and angular pyranoxanthone 17
showed selective anti-inflammatory activity toward elastase re-
lease with an IC50 value of 0.49 lg/mL. Except for 16, 18, and 20,
M. M. M. Pharmaceuticals 2009, 2, 33.
21. (a) Hwang, T.-L.; Leu, Y.-L.; Kao, S.-H.; Tang, M.-C.; Chang, H.-L. Free Radical Biol.
Med. 2006, 41, 1433; (b) Babior, B. M.; Kipnes, R. S.; Curnutte, J. T. J. Clin. Invest.
1973, 52, 741; (c) Sklar, L. A.; McNeil, V. M.; Jesaitis, A. J.; Painter, R. G.;
Cochrane, C. G. J. Biol. Chem. 1982, 257, 5471.
22. General: Unless stated otherwise, the chemicals were acquired from
commercial sources and used without further purification. All chemicals
were purchased from ACROS and Aldrich. Melting points were measured with a
Fisher-John melting apparatus without correction. 1
H
NMR spectra were
measured on 300 MHz Varian Gemini 2000 spectrometer. The solvent was
CD OD or CDCl or DMSO. Mass spectra were measured on PECIEX API 3000
3
3
with turbo ion spray source, Agilent-1100 LC/MSD-Trap, or Shimadzu LCMS-IT-
TOF with ESI interface. Thin-layer chromatography (TLC) and preparative TLC
were performed on precoated silica GF plates purchased from Merck, Inc.
compounds 14–21 exhibited potent activity toward elastase release
and were over 15-fold more potent than the positive control PMSF.
In this investigation, we prepared a series of 1,3,6-substituted
xanthones (4–6), as well as prenyl- and pyrano-xanthone analogs
+
Biotage Flash or Isco Companion systems were used for flash chromatography.
Silica gel (200–400 mesh) from Aldrich, Inc. was used for column
chromatography.
2
2
(
7–21), and evaluated SAR for their cytotoxic and anti-inflamma-
1
,3,6-Trihydroxy-9H-xanthen-9-one (4): Eaton’s reagent (P
(10 mL) was added slowly to a mixture of 2,4-dihydroxybenzoic acid (1;
55 mg, 1 mmol) and phloroglucinol (3; 126 mg, 1 mmol). The resulting
2 5 3 3
O –CH SO H)
tory activities. In conclusion, among all screened compounds, pre-
nylxanthones 7–13 were less active than pyranoxanthones 14–21
in both anticancer and anti-inflammatory assays. Two angular
1
mixture was stirred for 1 h at 80 °C, cooled to rt, and poured onto ice. After
vigorous stirring at ambient temperature for 2 h, thin slurry formed. The solid
was collected by filtration, washed with water to adjust the pH to
approximately 6, and dried under vacuum at 50 °C. The residue was
chromatographed on silica gel and eluted successively with hexane–EtOAc
3
,3-dimethylpyranoxanthone analogs (16 and 20) showed notable
and selective activity against a multidrug resistant (MDR) cell line
KBvin) with much lower activity against the parent cells (KB). A
(
(
2:3) to give the desired product (225 mg, 92%) as a yellow solid. Mp: 158–
1
linear 3,3-dimethylpyranoxanthone compound (14) exhibited sig-
nificant potency in both anti-inflammatory assays, and an angular
3
160 °C; H NMR (CD OD, 300 MHz): d 6.13 (1H, d, J = 2.1 Hz), 6.26 (1H, d,
J = 2.4 Hz), 6.72 (1H, d, J = 2.4 Hz), 6.81 (1H, dd, J = 2.3, 8.9 Hz), 7.97 (1H, d,
J = 9.0 Hz).
3
-methyl-3-prenylpyranoxanthone compound (17) was 200-fold
1
,3-Dihydroxy-6-methoxy-9H-xanthen-9-one (5): Under similar conditions to
more potent than PMSF, the positive control, in the elastase release
assay.
those described for 4, phloroglucinol (3; 126 mg, 1 mmol) and 2,4-
dimethoxybenzoic acid (2; 182 mg, 1 mmol) afforded the desired product
1
(
245 mg, 95%) as a yellow solid, mp: 135–137 °C; H NMR (CD
3
OD, 300 MHz): d
3
.89 (3H, s), 6.21 (1H, d, J = 2.1 Hz), 6.28 (1H, d, J = 2.4 Hz), 6.70 (1H, d,
J = 2.4 Hz), 6.83 (1H, dd, J = 2.3, 8.9 Hz), 7.89 (1H, d, J = 9.0 Hz).
-Hydroxy-3,6-dimethoxy-9H-xanthen-9-one (6): Iodomethane
.59 mmol) was added to a solution of 4 (130 mg, 0.53 mmol) and K
183 mg, 1.33 mmol) in acetone. The resulting solution was stirred at 60 °C
Acknowledgments
1
1
(
(100
lL,
3
2
CO
This investigation was supported by Grant CA 17625-32 from
the National Cancer Institute, NIH, USA (K.H.L.), and by Grant
DOH101-TD-C-111-004 from the Department of Health, Executive
Yuan, Taiwan (Y.C.W.).
under reflux for 6 h. The cooled solution was filtered and concentrated in
vacuo. Purification on a flash column (n-hexane/EtOAc, 85/15) yielded the
1
desired compound (231 mg, 85%) as a yellow powder. Mp: 118–120 °C;
NMR (CDCl
3 Â 1H, each s), 6.91 (1H, d, J = 8.7 Hz), 8.11 (1H, d, J = 8.7 Hz), 12.99 (1H, s).
Prenylation of 1,3,6-trihydroxy-xanthen-9-one (4): Method 1: Prenyl bromide
243 L, 2 mmol) was added dropwise over 10 min to a solution of 4 (244 mg,
mmol) and KOH (112 mg, 2 mmol) in H O at 0 °C under N atmosphere. The
H
3
, 300 MHz): d 3.87 and 3.92 (2 Â 3H, each s), 6.31, 6.36, and 6.79
(
References and notes
(
1
l
1.
2.
3.
(a) Ollis, W. D.; Redman, B. T.; Sutherland, I. O.; Jewers, K. J. Chem. Soc. Chem.
Commun. 1969, 15, 879; (b) Kumar, P.; Baslas, R. K. Herba Hung. 1980, 19, 81.
Li, N. G.; You, Q. D.; Huang, X. F.; Wang, J. X.; Guo, Q. L.; Chen, X. G.; Li, Y.; Li, H.
Y. Chin. Chem. Lett. 2007, 18, 659.
Han, Q.-B.; Yang, N.-Y.; Tian, H.-L.; Qiao, C.-F.; Song, J.-Z.; Chang, D. C.; Chen, S.-
L.; Luo, K. Q.; Xu, H.-X. Phytochemistry 2008, 69, 2187.
2
2
resulting mixture was stirred at 0 °C for 24 h. During this time, a yellow solid
precipitated from the mixture. The reaction mixture was quenched with pH 1
(
HCl) solution and extracted with EtOAc. The combined organic layers were
washed with brine, dried over MgSO , filtered, and concentrated in vacuo.
Purification on a flash column yielded 7, 8, and 9 (n-hexane/EtOAc, 95/5)
successively.
4
4
5
.
.
Ollis, W. D.; Ramsay, M. V. J.; Sutherland, I. O. Tetrahedron 1965, 21, 1453.
(a) Guo, Q. L.; You, Q. D.; Wu, Z. Q.; Yuan, S. T.; Zhao, L. Acta Pharmacol. Sinica
1
,3,6-Trihydroxy-2,4-bis(3-methylbut-2-enyl)-9H-xanthen-9-one (7): Yield: 5.8%;
1
yellow oil; H NMR (CD
3
OD, 300 MHz): d 1.67 and 1.89 (2 Â 6H, each s), 3.34
2
004, 25, 769; (b) Liu, W.; Guo, Q. L.; You, Q. D.; Zhao, L.; Gu, H. Y.; Yuan, S. T.;
(
6
2H, s), 3.43 (2H, d, J = 7.2 Hz), 5.15–5.19 (2 Â 1H, m), 6.69 (1H, d, J = 2.1 Hz),
World, J. Gastroenterol 2005, 11, 3655; (c) Zhao, L.; Guo, Q. L.; You, Q. D.; Wu, Z.
Q.; Gu, H. Y. Biol. Pharm. Bull. 2004, 27, 998.
.78 (1H, dd, J = 2.4, 8.7 Hz), 7.93 (1H, d, J = 8.7 Hz).
1
,3,6-Trihydroxy-2-(3-methylbut-2-enyl)-9H-xanthen-9-one (8). Yield: 4.2%
6
7
.
.
Zhou, Z. T.; Wang, J. W. Chin. J. New Drugs 2007, 16, 79.
Thoison, O.; Fahy, J.; Dumontet, V.; Chiaroni, A.; Riche, C.; Tri, M. V.; Sevenet, T.
J. Nat. Prod. 2000, 63, 441.
1
yield; yellow solid; H NMR (CD
each s), 3.35 (2H, d, J = 6.9 Hz), 5.18–5.19 (1H, m), 6.14 (1H, s), 6.68 (1H, d,
J = 2.1 Hz), 6.76 (1H, dd, J = 2.1, 8.9 Hz), 7.89 (1H, d, J = 9.0 Hz).
3
OD, 300 MHz): d 1.65 and 1.84 (2 Â 3H,
8
.
.
Pedro, M.; Cerqueira, F.; Sousa, M. E.; Nascimento, M. S. J.; Pinto, M. Bioorg. Med.
Chem. 2002, 10, 3725.
Gonzalez, M. J.; Nascimento, M. S. J.; Cidade, H. M.; Pinto, M. M. M.; Kijjoa, A.;
Anantachoke, C.; Silva, A. M. S.; Herz, W. Planta Med. 1999, 65, 368.
1
,3,6-Trihydroxy-2,5-bis(3-methylbut-2-enyl)-9H-xanthen-9-one (9): Yield: 16%;
1
yellow solid; H NMR (CD
J = 4.2 Hz), 3.45 (2H, d, J = 6.3 Hz), 3.55 (2H, d, J = 6.3 Hz), 5.21–5.24 (2H, m),
.19 (1H, s), 6.83 (1H, d, J = 8.7 Hz), 7.84 (1H, d, J = 9.0 Hz).
Method 2: To a solution of 4 (244 mg, 1 mmol), KI (332 mg, 2 mmol), and KOH
3
OD, 300 MHz): d 1.67 (6H, s), 1.78 (2 Â 3H, d,
9
6
1
0. (a) Lu, Z. X.; Hasmeda, M.; Mahabusarakam, W.; Ternai, B.; Ternai, P. C.; Polya,
G. M. Chem. Biol. Interact. 1998, 114, 121; (b) Jinsart, W.; Ternai, B.;
Buddhasukh, D.; Polya, G. M. Phytochemistry 1992, 31, 3711.
(
112 mg, 2 mmol) in DMF at 0 °C under N
2
atmosphere, prenyl bromide
(
243 L, 2 mmol) was added dropwise over 10 min. The resulting mixture was
l
1
1
1. Ho, C. K.; Huang, Y. L.; Chen, C. C. Planta Med. 2002, 68, 975.
2. Nakatani, K.; Nakahata, N.; Arakawa, T.; Yasuda, H.; Ohizumi, Y. Biochem.
Pharmacol. 2002, 63, 73.
then treated under conditions similar to Method 1. Purification on a flash
column yielded a mixture of 10 + 11 + 12 (n-hexane/EtOAc, 95/5) and pure 13
(
n-hexane/EtOAc, 90/10). The components of the mixture were then separated
by preparative TLC (n-hexane/EtOAc, 4/1).
,6-Dihydroxy-3-(3-methylbut-2-enyloxy)-9H-xanthen-9-one (10): Yield: 4.2%;
1
3. Castanheiro, R. A. P.; Pinto, M. M. M.; Silva, A. M. S.; Cravo, S. M. M.; Gales, L.;
Damas, A. M.; Nazareth, N.; Nascimento, M. S. J.; Eaton, G. Bioorg. Med. Chem.
1
2
007, 15, 6080.
1
yellow oil; H NMR (CDCl
3
, 300 MHz): d 1.67 (2 Â 3H, each s), 3.30 (2H, s), 3.43
1
1
4. Finnegan, R. A.; Merkel, K. E.; Patel, J. K. J. Pharm. Sci. 1973, 62, 483.
5. (a) Grover, P. K.; Shah, G. D.; Shah, R. C. J. Chem. Soc. 1955, 3982; (b) Quillinan,
A. J.; Scheinmann, F. J. Chem. Soc., Perkin Trans. 1 1973, 1329.
(
2H, d, J = 7.2 Hz), 5.15–5.19 (1H, m), 6.13 (1H, d, J = 2.1 Hz), 6.26 (1H, d,
J = 2.4 Hz), 6.69 (1H, d, J = 2.1 Hz), 6.78 (1H, dd, J = 2.4, 8.7 Hz), 7.93 (1H, d,
J = 8.7 Hz).
1
6. (a) Zhou, T.; Shi, Q.; Chen, C.-H.; Huang, L.; Ho, P.; Morris-Natschke, S. L.; Lee,
K.-H. Eur. J. Med. Chem. 2012, 47, 86; (b) Moreau, S.; Varache-Lembège, M.;
Larrouture, S.; Fall, D.; Neveu, A.; Deffieux, G.; Deffieux, G.; Vercauteren, J.;
Nuhrich, A. Eur. J. Med. Chem. 2002, 37, 237.
1
9
-Hydroxy-2-(3-methylbut-2-enyl)-3,6-bis(3-methylbut-2-enyloxy)-9H-xanthen-
-one (11): Yield: 50%; yellow solid; 1H NMR (CDCl
, 300 MHz): d 1.77–1.82
3
(
12H, m), 1.85–1.90 (6H, m), 4.55–4.61 (6H, m), 5.49–5.51 (4H, m), 6.35 (1H, d,