Perfluoroalkylsulfonyloxyisoflavones: Synthesis and anti-proliferation of HL-60

Article abstract of DOI:10.2174/157017809788681257

Isoflavonoids containing a perfluoroalkylsulfonyloxy group were synthesized by perfluoroalkylsulfonylation of hydroxyisoflavones. The reaction showed high regioselectivity. Inhibitory effects of the synthesized isoflavones against proliferation of HL-60 a

Full text of DOI:10.2174/157017809788681257

416
Letters in Organic Chemistry, 2009, 6, 416-418
Perfluoroalkylsulfonyloxyisoflavones: Synthesis and Anti-Proliferation of
HL-60
Hongqi Li* and Ye Jin
Key Laboratory of Science & Technology of Eco-Textile, Ministry of Education, College of Chemistry, Chemical
Engineering and Biotechnology, Donghua University, 2999 North Renmin Road, Shanghai 201620, China
Received October 09, 2008: Revised May 04, 2009: Accepted May 06, 2009
Abstract: Isoflavonoids containing a perfluoroalkylsulfonyloxy group were synthesized by perfluoroalkylsulfonylation of
hydroxyisoflavones. The reaction showed high regioselectivity. Inhibitory effects of the synthesized isoflavones against
proliferation of HL-60 and BEL-7402 cells were tested in vitro. Two isoflavones displayed strong inhibitory effect on HL-
60 cells.
Keywords: Isoflavone, perfluoroalkylsulfonate, regioselectivity, HL-60.
Isoflavones especially daidzein and genistein and their
derivatives have been found to exhibit anti-cancer activities
[1-4]. Recently Yoshikawa et al. reported moderate or
substantial anti-proliferative activities of isoflavones against
human leukemia U937 cells [5]. Yokosuka and colleagues
separated a new isoflavone with inhibitory effect on human
promyelocytic leukemia HL-60 cells [6]. Studies in our
laboratory and other research groups showed that
continuation of our previous work and in the light of the
work by Soidinsalo and Wähälä who reported the sulfation
of hydroxyisoflavonoids such as daidzein and genistein with
a pyridine sulfur trioxide complex made in situ from
pyridine and chlorosulfonic acid [8], we have designed a
series of novel isoflavones by introduction of
a
perfluoroalkylsulfonyloxy group onto 7- or 4ꢀ-position of
isoflavones in order to obtain lead compounds for anti-
RFO2SO
O
HO
O
O
K2CO3/DMF
RFSO2F
O
OMe
OMe
1a: RF = C4F9, 71%
1b: RF = C8F17, 51%
Scheme 1. Perfluoroalkylsulfonylation of 7-hydroxy-4ꢀ-methoxyisoflavone.
HO
O
HO
O
K2CO3/DMF
RFSO2F
O
O
R
R
OSO2RF
OH
2a: R = H, RF = C4F9, 36%
2b: R = H, RF = C8F17, 82%
3a: R = OH, RF = C4F9, 22%
3b: R = OH, RF = C8F17, 80%
daidzein: R = H
genistein: R = OH
Scheme 2. Perfluoroalkylsulfonylation of daidzein and genistein.
introduction of trifluoromethyl, difluoromethyl, methoxy,
and/or hydroxy groups into flavonoids or isoflavonoids
could enhance their anti-proliferative activities [3-7]. As a
cancer drugs. Herein we report synthesis and preliminary
study on inhibitory effects of perfluoroalkylsulfonyloxyiso-
flavones against proliferation of human leukemia cell HL-60
and human liver cancer cell BEL-7402.
7-Hydroxy-4ꢀ-methoxyisoflavone, daidzein, and genistein
[9], containing one, two or three hydroxy group(s), respec-
tively were sulfonylated with perfluoroalkyl fluorides in
*Address correspondence to this author at the Key Laboratory of Science &
Technology of Eco-Textile, Ministry of Education, College of Chemistry,
Chemical Engineering and Biotechnology, Donghua University, 2999 North
Renmin Road, Shanghai 201620, China; E-mail: hongqili@dhu.edu.cn
1570-1786/09 $55.00+.00
© 2009 Bentham Science Publishers Ltd.

Perfluoroalkylsulfonyloxyisoflavones
Letters in Organic Chemistry, 2009, Vol. 6, No. 5
417
anhydrous DMF in the presence of potassium carbonate at
70˚C as showed in Scheme 1 and Scheme 2.
5,7-Dihydroxy-4'-perfluorobutylsulfonyloxyisoflavone (3a):
yellow powder, mp >300˚C; 1H NMR (DMSO-d6) ꢁ = 12.74
(s, 1H, 5-OH), 10.96 (s, 1H, 7-OH), 8.52 (s, 1H, 2-H), 7.77
(d, 2H, 2'-H), 7.57 (d, 2H, 3'-H), 6.43 (s, 1H, 6-H), 6.26 (s,
1H, 8-H); 13C NMR (DMSO-d6) ꢁ = 182.27 (C=O), 167.41,
164.74, 160.39, 158.42, 151.80, 134.57, 134.06, 124.05,
123.54, 107.18, 102.07, 96.74; IR (KBr pellet) ꢂ = 3335,
3206, 1654, 1572, 1501, 1431 cmꢃ1; Anal. Calcd. for
C19H9F9O7S: C, 41.32; H, 1.64; Found: C, 41.41; H, 1.59.
5,7-Dihydroxy-4'-perfluorooctylsulfonyloxyisoflavone (3b):
yellow powder, mp >300˚C; 1H NMR (DMSO-d6) ꢁ = 12.69
(s, 1H, 5-OH), 10.92 (s, 1H, 7-OH), 8.47 (s, 1H, 2-H), 7.71
(d, 2H, 2'-H), 7.53 (d, 2H, 3'-H), 6.38 (s, 1H, 6-H), 6.21 (s,
1H, 8-H); 13C NMR (DMSO-d6) ꢁ = 179.21 (C=O), 164.47,
161.84, 157.41, 155.28, 148.75, 131.58, 130.97, 120.99,
120.53, 104.23, 99.14, 93.78; IR (KBr pellet) ꢂ = 3475,
1670, 1616, 1602, 1523, 1445 cmꢃ1; Anal. Calcd. for
C23H9F17O7S: C, 36.72; H, 1.21; Found: C, 36.61; H, 1.26.
While perfluoroalkylsulfonylation of the monohydroxy-
isoflavone afforded the expected isoflavone (1a) and (1b) in
50-70% yield (Scheme 1), reactions between daidzein or
genistein and perfluoroalkylsulfonyl fluorides proceeded
regioselectively to yield isoflavone (2a) and (2b) or (3a) and
(3b) (Scheme 2). Typical synthetic procedures and
spectroscopic data for the new compounds were as follows:
To a 50 mL dried three-necked flask containing 7-hydroxy-
4ꢀ-methoxyisoflavone (0.39 g, 1.5 mmol) was added
anhydrous DMF (15 mL). After the substrate was dissolved
anhydrous powder of K2CO3 (0.3 g) and perfluorooctyl-
sulfonyl fluoride (2.0 g, 4 mmol) were added under nitrogen
atmosphere. The mixture was heated to 70ꢀ and stirred for
7 h. After reaction the mixture was allowed to cool to
ambient temperature and poured into ice-water (100 mL).
The precipitate was filtered, washed with water, and dried in
vacuo to give a khaki powder which was recrystallized from
ethanol to afford the product 4'-methoxy-7-perfluorooctyl-
sulfonyloxyisoflavone (1b) as brown pellets (0.43 g, 51%),
When the molar ratio between perfluoroalkylsulfonyl
fluoride and daidzein or genistein was altered in the range of
1:1 to 5:1, monoperfluoroalkylsulfonylation products were
obtained exclusively. Moreover, perfluoroalkylsulfonylation
took place only at 4ꢀ-OH of daidzein or genistein. We
suggest that the steric bulk of perfluoroalkylsulfonyl
fluorides may account for the regioselective perfluoroalkyl-
sulfonylation of daidzein and genistein at 4ꢀ-position due to
its smaller steric hindrance relative to 7-position, though the
acidity of 7-OH (pKa ꢄ 7) on isoflavones is stronger than that
of 4ꢀ-OH (pKa ꢄ 11) [10].
1
mp 286-288˚C; H NMR (CD3OD) ꢁ = 8.39 (s, 1H, 2-H),
8.31 (s, 1H, 5-H), 7.70 (s, 1H, 6-H), 7.50 (d, 2H, 2'-H), 7.49
(s, 1H, 8-H), 6.99 (d, 2H, 3'-H), 3.82 (s, 3H, OCH3); 13C
NMR (CF3COOD): ꢁ = 182.81 (C=O), 161.51, 160.68,
159.90, 156.76, 133.29, 130.94, 125.21, 123.85, 122.76,
121.36, 117.39, 113.94, 57.64 (OCH3); IR (KBr pellet) ꢂ =
3530, 1648, 1618, 1507, 1444, 1425, 1206, 1156 cmꢃ1; MS
(EI, 70 eV): m/z (%) 750 (M+, 100), 267 (79); Anal. Calcd.
for C24H11F17O6S: C, 38.41; H, 1.48; Found: C, 38.57; H,
Inhibitory effects of the new isoflavones against
proliferation of human leukemia cell HL-60 and human liver
cancer cell BEL-7402 were tested in vitro by Methyl-
Thiazol-Tetrazolium (MTT) reduction method and Sulforho-
damine B (SRB) albumine coloration method, respectively.
The inhibition ratio data of these compounds against
proliferation of HL-60 and BEL-7402 cells at different
concentrations were listed in Table 1 and 2, respectively.
From the results several points were concluded: (1) The
inhibition ratio is dependent on the concentration of the
compounds and increased with the increase in the
concentration of the compounds. (2) Each isoflavone with a
perfluorobutylsulfonyloxy group (1a), (2a), and (3a)
exhibited stronger inhibitory effect than its perfluorooctyl-
sulfonyloxy group counterpart (1b), (2b), and (3b),
respectively. While isoflavones containing a perfluorooctyl-
sulfonyloxy group showed very weak anti-proliferative
activity, 2a and 3a with a perfluorobutylsulfonyloxy
substituent at 4ꢀ-O position displayed strong cytotoxity
against HL-60 cells. The later (3a) displayed an inhibition
ratio of 99.6% against HL-60 cells under a concentration of
10–8 M and also showed weak inhibitory effect on BEL-7402
cells. This is perhaps because the smaller perfluorobutyl-
sulfonates are more penetrating and easier to exert their
inhibitory effect. (3) The more hydroxy groups an isoflavone
bears, the stronger inhibitory effect it exhibited, suggesting
that a number of polyhydroxyisoflavones such as daidzein
and genistein and their derivatives exhibited substantial anti-
cancer activities [2.3]. Based on the above results we
conclude that 5- and 7-hydroxy and perfluorobutylsulfonyl
groups are very important to the anti-proliferative activity of
1.52.
4'-Methoxy-7-perfluorobutyl-sulfonyloxyisoflavone
1
(1a): khaki powder, mp >300˚C; H NMR (DMSO-d6) ꢁ =
8.20 (s, 1H, 2-H), 7.83 (d, 1H, J = 8.8 Hz, 5-H), 7.48 (d, 2H,
2'-H), 6.95 (d, 2H, 3'-H), 6.79 (dd, 1H, J = 8.8 and 2.4 Hz, 6-
H), 6.62 (d, 1H, J = 2.4 Hz, 8-H), 3.76 (s, 3H, OCH3); 13C
NMR (DMSO-d6): ꢁ = 177.34 (C=O), 167.56, 161.67,
160.52, 155.57, 132.83, 129.69, 127.26, 125.77, 118.86,
118.28, 116.37, 104.82, 57.94 (OCH3); IR (KBr pellet) ꢂ =
1670, 1616, 1602, 1523, 1445 cmꢃ1; Anal. Calcd. for
C20H11F9O6S: C, 43.65; H, 2.01; Found: C, 43.81; H, 2.07. 7-
Hydroxy-4'-perfluorobutylsulfonyloxyisoflavone (2a): white
1
powder, mp >300˚C; H NMR (DMSO-d6) ꢁ = 10.89 (s, 1H,
7-OH), 8.51 (s, 1H, 2-H), 7.99 (d, 1H, J = 8.8 Hz, 5-H), 7.77
(d, 2H, 2'-H), 7.57 (d, 2H, 3'-H), 6.98 (dd, 1H, J = 8.8 and
2.2 Hz, 6-H), 6.91 (d, 1H, J = 2.2 Hz, 8-H); 13C NMR
(DMSO-d6) ꢁ = 176.88 (C=O), 165.66, 160.29, 157.36,
151.63, 135.81, 133.95, 130.09, 124.74, 123.91, 119.29,
118.23, 105.04; IR (KBr pellet) ꢂ = 3431, 1648, 1615, 1578,
1513, 1425 cmꢃ1; MS (EI, 70 eV): m/z (%) 536 (M+, 18%),
254 (18%), 253 (100%), 242 (30%), 225 (19%), 89 (21%),
69 (21%); Anal. Calcd. for C19H9F9O6S: C, 42.55; H, 1.69;
Found: C, 42.41; H, 1.67. 7-Hydroxy-4'-perfluorooctylsulfo-
1
nyloxyisoflavone (2b): white powder, mp >300˚C; H NMR
(DMSO-d6) ꢁ = 10.86 (s, 1H, 7-OH), 8.74 (s, 1H, 2-H), 8.57
(d, 1H, J = 8.8 Hz, 5-H), 8.01 (d, 2H, 2'-H), 7.88 (d, 2H, 3'-
H), 7.56 (d, 1H, J = 8.8 Hz, 6-H), 6.90 (s, 1H, 8-H); 13C
NMR (CF3COOD) ꢁ = 168.09 (C=O), 163.32, 162.80,
162.89, 153.89, 134.36, 133.02, 131.12, 130.29, 125.06,
124.71, 121.93, 105.60; IR (KBr pellet) ꢂ = 3431, 1648,
1615, 1578, 1513, 1425, 1256, 1048 cmꢃ1; Anal. Calcd. for
C23H9F17O6S: C, 37.52; H, 1.23; Found: C, 37.61; H, 1.17.

418 Letters in Organic Chemistry, 2009, Vol. 6, No. 5
Li and Jin
Table 1. Inhibition Ratio of the New Compounds Against Proliferation of HL-60 cells (%)*
Inhibition Ratio (%) at Different Concentrations (M)
Compound
10–8
10–7
10–6
10–5
10–4
1a
1b
2a
2b
3a
3b
11.5
0
10.5
3.9
16.1
3.6
18.6
2.0
67.3
9.8
59.8
1.7
76.2
5.7
100
19.4
99.6
42.3
93.2
66.0
99.9
58.4
95.8
78.1
99.4
79.8
99.6
13.4
100
16.5
*Inhibitory effects of the new isoflavones against proliferation of human leukemia cell HL-60 were tested in vitro by Methyl-Thiazol-Tetrazolium (MTT) reduction method.
Table 2. Inhibition Ratio of the New Compounds Against Proliferation of BEL-7402 Cells (%)*
Inhibition Ratio (%) at Different Concentrations (M)
Compound
10–8
10–7
10–6
10–5
10–4
1a
1b
2a
2b
3a
3b
14.8
7.8
13.1
11.0
22.1
2.3
11.4
7.0
31.0
29.5
44.3
49.7
98.8
30.1
92.1
93.6
97.4
78.4
98.9
93.1
17.9
0
30.4
17.9
41.5
15.1
99.6
22.0
29.1
18.2
*Inhibitory effects of the new isoflavones against proliferation of human liver cancer cell BEL-7402 were tested in vitro by Sulforhodamine B (SRB) albumine coloration method.
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In summary, we have synthesized a series of novel
isoflavones by perfluoroalkylsulfonylation of hydroxyiso-
flavones. Perfluoroalkylsulfonylation of daidzein and
genistein showed high regioselectivity. The structures of the
1
synthesized isoflavones were characterized by H NMR, 13C
NMR, MS, FT-IR spectra, and elemental analysis. Inhibitory
effects of the new compounds against proliferation of HL-60
and BEL-7402 cells were tested in vitro. Two isoflavones
displayed strong inhibitory effect on HL-60 cells, suggesting
that hydroxy and perfluorobutylsulfonyloxy groups are
important to the anti-proliferative activity of isoflavonoids.
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ACKNOWLEDGEMENTS
Finantial support of the project by Program for
Changjiang Scholars and Innovative Research Team in
University (No. IRT0526) and Shanghai Municipal Natural
Science Foundation (No. 06ZR14001) was acknowledged.
We thank the National Center for Drug Screening for anti-
cancer activity screening.
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