Antipsoriatic anthrones with modulated redox properties. 4. Synthesis and biological activity of novel 9,10-dihydro-1,8-dihydroxy-9-oxo-2- anthracenecarboxylic and -hydroxamic acids

Article abstract of DOI:10.1021/jm9701785

A novel series of carboxylic and hydroxamic acids based on 1,8- dihydroxy-9(10H)-anthracenone were synthesized from 8-hydroxy-1-methoxy- 9,10-anthracenedione as the key intermediate and evaluated both in the bovine polymorphonuclear leukocyte 5-lipoxygenase (5-LO) assay and in the HaCaT keratinocyte proliferation assay for their enzyme inhibitory and antiproliferative activity, respectively. The most potent inhibitors in both assays were the N-methylated hydroxamic acids 5d-8d with straight chain alkyl spacers. Incorporation of these structural features on the anthracenone pharmacophore resulted in increased inhibitory activity against 5-LO while the antiproliferative activity was retained. In addition, prooxidant properties as measured by deoxyribose degradation and cytotoxicity as assessed by LDH release were largely reduced as compared with the antipsoriatic anthralin. Contrary to anthralin, antioxidant properties were observed as documented by the reactivity of the novel compounds against free radicals and inhibition of lipid peroxidation in model membranes.

Full text of DOI:10.1021/jm9701785

2780
J . Med. Chem. 1997, 40, 2780-2787
An tip sor ia tic An th r on es w ith Mod u la ted Red ox P r op er ties. 4. Syn th esis a n d
Biologica l Activity of Novel 9,10-Dih yd r o-1,8-d ih yd r oxy-9-oxo-2-
a n th r a cen eca r boxylic a n d -h yd r oxa m ic Acid s1,†
Klaus Mu¨ller* and Helge Prinz
Institut fu¨r Pharmazeutische Chemie, Westfa¨lische Wilhelms-Universita¨t Mu¨nster, Hittorfstrasse 58-62,
D-48149 Mu¨nster, Germany
Received March 17, 1997X
A novel series of carboxylic and hydroxamic acids based on 1,8-dihydroxy-9(10H)-anthracenone
were synthesized from 8-hydroxy-1-methoxy-9,10-anthracenedione as the key intermediate and
evaluated both in the bovine polymorphonuclear leukocyte 5-lipoxygenase (5-LO) assay and in
the HaCaT keratinocyte proliferation assay for their enzyme inhibitory and antiproliferative
activity, respectively. The most potent inhibitors in both assays were the N-methylated
hydroxamic acids 5d -8d with straight chain alkyl spacers. Incorporation of these structural
features on the anthracenone pharmacophore resulted in increased inhibitory activity against
5-LO while the antiproliferative activity was retained. In addition, prooxidant properties as
measured by deoxyribose degradation and cytotoxicity as assessed by LDH release were largely
reduced as compared with the antipsoriatic anthralin. Contrary to anthralin, antioxidant
properties were observed as documented by the reactivity of the novel compounds against free
radicals and inhibition of lipid peroxidation in model membranes.
Ch a r t 1
Anthracenones such as anthralin (1) are among the
major topical remedies for the treatment of psoriasis.2
While these drugs are considered generally safe, like
most forms of therapy unpleasant effects do accompany
their topical administration. The most notable and
prevalent are the staining and irritation of the non-
affected skin.2 An encouraging trend has been to
elucidate the molecular origin of the proinflammatory
action of the anthrone class and, by appropriate chemi-
cal modification, to improve the therapeutic index.3
Thus, irritation of the nonaffected psoriatic skin caused
by anthracenones may be interpreted in terms of their
efficacy to produce oxygen radicals.4,5 As part of our
project aimed at providing improved antipsoriatic an-
thrones, we have synthesized analogs in which one or
both active methylene protons at C-10 were replaced
by suitable substituents (e.g., 2) which permit control
over the release of active oxygen species.6 As a result,
2 is currently undergoing clinical evaluation as a topical
treatment for psoriasis.
Sch em e 1. Iron-Dependent Production of Active Oxygen
Species by Anthralin
An alternative approach to the control of oxygen-
radical formation would be to chelate the transition
metal that facilitates the autoxidation of the anthra-
cenone molecule with the concomitant production of
oxygen radicals. In this context, several factors regard-
ing oxygen-radical generation by anthrones and the role
of iron have to be considered in the design of novel
derivatives.
requires the presence of transition metals, such as iron.8
Second, superoxide radical readily undergoes dismuta-
tion to form hydrogen peroxide and oxygen (eq 2), which
have only moderate reactivity and, therefore, cannot
account for the biological damage observed in systems
in which they are generated.9,10 It has been suggested,
therefore, that the observed damage to a target is due
to their conversion into the highly reactive hydroxyl
radical.9,10 Third, iron is an important catalyst of
hydroxyl-radical production, via the Haber-Weiss cycle
(eqs 3 and 4, a superoxide-driven Fenton reaction).11
Moreover, iron is the most likely candidate for stimulat-
ing hydroxyl-radical generation in vivo12 and has been
demonstrated to play a key role in the formation of these
The evidence is convincing that iron plays a role in
radical production by antipsoriatic anthrones in vivo
(Scheme 1). First, one-electron reduction of oxygen by
anthralin produces superoxide radical (eq 1).7 As the
direct reaction of oxygen with biomolecules is spin
forbidden, significant production of superoxide radical
† Dedicated to Prof. Dr. G. Wurm, Berlin, on the occasion of his 60th
birthday.
* To whom correspondence should be addressed. Phone: +49 251-
8333324. Fax: +49 251-8333310.
X Abstract published in Advance ACS Abstracts, August 1, 1997.
S0022-2623(97)00178-7 CCC: $14.00 © 1997 American Chemical Society

Antipsoriatic Anthrones with Modulated Redox Properties
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 17 2781
Sch em e 2a
species by anthralin.13,14 In support of this, the catalytic
function of iron in the enhancement of anthralin-
induced lipid peroxidation (LPO) has been documented.14
Finally, the importance of iron in mediating oxidative
damage by antipsoriatic anthrones is of particular
interest because the skin is a significant site of iron
excretion which is increased in psoriasis.15 On the basis
of the above information, we have designed synthetic
analogs combining an anthracenone chromophore and
a hydroxamic acid moiety, which has a high affinity for
iron,16 to suppress iron-dependent generation of oxygen
radicals. In addition to and independently of their iron-
chelating properties, hydroxamates act as free radical
scavengers.17
A second aspect of 1,8-dihydroxy-9(10H)-anthra-
cenones containing an iron-chelating functionality, such
as hydroxamic acid, results from the known role of iron
in the mechanism of 5-lipoxygenase (LO).18 Indeed,
since Corey’s disclosure19 that hydroxamic acid analogs
of arachidonic acid are effective inhibitors of the enzyme,
numerous attempts have been made to develop hydrox-
amic acid-based 5-LO inhibitors as therapeutic
agents.20-25 An example of a hydroxamate-based topical
antiinflammatory agent is bufexamac (3). Furthermore,
inhibitors of 5-LO could have therapeutic utility in a
number of inflammatory disease states including pso-
riasis.18,26
a
Reagents: (a) SnCl2, HCl, glacial acetic acid, 118 °C; (b)
MeOH, concentrated H2SO4; (c) NH(R)OH‚HCl (R ) H, Me), Na/
MeOH, N2, 0-5 °C.
Sch em e 3a
Although hydroxamic acid derivatives exhibit potent
5-LO inhibitory activity, this structural pattern per se
may not be sufficient for attaining antiproliferative
activity. With psoriasis as target for therapy, both the
inflammatory and hyperproliferative aspects of the
disease have to be resolved. Nevertheless, with the 1,8-
dihydroxy-9(10H)-anthracenone pharmacophore at-
tached to the hydroxamic acid moiety by proper side
chains, it is believed that compounds having desired
biological activity could be obtained.
In this paper we describe the synthesis and biological
activity of 1,8-dihydroxy-9(10H)-anthracenones (4-14,
a -d ), bearing various linked carboxylic and hydroxamic
acids in the 2-position. The N-methyl-substituted hy-
droxamates show reduced hydroxyl-radical generation
as compared to anthralin and are potent inhibitors of
enzymatic (5-LO-mediated) and nonenzymatic (free
radical-induced) lipid peroxidation (LPO). Furthermore,
these compounds exhibit high antiproliferative activity
against the keratinocyte cell line HaCaT.
a
Reagents: (a) Na2S2O4, NaOH, MeO(CH2)3CHO, N2, 90 °C;
(b) HBr (62%), glacial acetic acid, 118 °C; (c) HMPA/H2O, 128 °C;
(d) PDC, DMF, room temperature; (e) MeOH, concentrated H2SO4;
(f) NaCN, DMSO; (g) SnCl2, HCl, glacial acetic acid, 118 °C.
Ch em istr y
Introduction of the appropriate side chains onto the
2-position of the anthralin nucleus was achieved at the
anthracenedione stage, and reduction of the appropri-
ately 2-substituted 9,10-anthracenediones in glacial
acetic acid with SnCl2/HCl was envisioned as the last
step in the preparation of the desired 1,8-dihydroxy-
9(10H)-anthracenone carboxylic acids 4a -14a . Esteri-
fication of the acids with methanol gave the 2-substi-
tuted 1,8-dihydroxy-9(10H)-anthracenone methyl car-
boxylates 4b-14b. These were reacted with hydroxyl-
amine hydrochloride or N-methylhydroxylamine hydro-
chloride according to conventional methods to yield the
desired 2-substituted 1,8-dihydroxy-9(10H)-anthra-
cenone hydroxamic acids 4c-14c or N-methylhydrox-
amic acids 4d -14d , respectively (Scheme 2).
droxy-8-methoxy-9,10-anthracenedione28 (15) as the key
intermediate (Scheme 3). Alkylation of 15 with methyl
4-oxobutanoate gave only poor yields of the desired
anthracenedione 22, (Scheme 4). Therefore, an alterna-
tive method was developed. As outlined in Scheme 3,
alkylation of 15 with 4-methoxybutyraldehyde afforded
16, which was directly converted to bromide 17 with
hydrobromic acid. Replacement of the bromo with a
hydroxy function using sodium hydroxide was trouble-
some and resulted in intramolecular ether formation at
the 1-hydroxy group. However, an aqueous solution of
hexamethylphosphorous triamide provided a potent
source of nucleophilic oxygen29 for the conversion of 17
to the alcohol 18. Oxidation of 18 with pyridinium
dichromate gave the butyric acid 19 which was then
esterified to 20 and reduced to 6a . The homologous 7a
The requisite 2-substituted anthracenedione precur-
sors were obtained by Marschalk reaction27 from 1-hy-

2782 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 17
Mu¨ller and Prinz
Sch em e 4a
Sch em e 6a
a
Reagents: (a) Na2S2O4, NaOH, MeO2C(CH2)2CHO or
MeO2C(CH2)4CHO, N2, 90 °C; (b) MeOH, concentrated H2SO4; (c)
SnCl2, HCl, glacial acetic acid, 118 °C.
Sch em e 5a
a
Reagents: (a) Na2S2O4, NaOH, NCC6H5CHO, N2, 0-5 °C;
(b) PDC, DMF, room temperature; (c) SnCl2, HCl, HOAc, 118 °C;
(d) H2SO4/H2O, glacial acetic acid, 118 °C.
Since the mode of action and induction of side effects
of anthralin are related to its redox activity leading to
the production of oxygen radicals,4,5 the novel com-
pounds were further evaluated by the use of three test
systems specifically addressed to three aspects of redox
properties: reactivity against the stable free radical 2,2-
diphenyl-1-picrylhydrazyl (DPPH), inhibition of lipid
peroxidation in model membranes,14 and hydroxyl-
radical generation (prooxidant potential).
In h ibition of 5-Lip oxygen a se. 5-LO inhibitory
activity was determined by measuring production of
5-hydroxyeicosatetraenoic acid (5-HETE) and leuko-
triene B4 (LTB4) in bovine polymorphonuclear leuko-
cytes (PMNL), since potential antipsoriatic drugs are
evaluated for their ability to inhibit the production of
LTB4.25,32-34
a
Reagents: (a) MeOH, concentrated H2SO4; (b) Me2SO4, K2CO3,
acetone, 55 °C; (c) methyl, isopropyl, benzyl, or phenylethyl
bromide, NaH, DMSO; (d) SnCl2, HCl, HOAc, 118 °C.
was also obtained from 17 by displacement of bromide
with sodium cyanide in DMSO to give valeronitrile 21,
followed by direct reduction to the anthracenone stage.
In contrast to the synthesis of 22, alkylation of 15 with
methyl 6-oxohexanoate followed by esterification of the
corresponding acid afforded ester 23 in good yields,
which was then reduced to the hexanoic acid 8a (Scheme
4).
Anthracenone acetic and propionic acids 4a and 5a
were prepared as previously described.30 2-Propionic
acids 9a -11a were prepared from 24,30 which was
esterified (25) and protected as the methyl ether 26,
alkylated with the appropriate bromides (27-30), and
then reduced (Scheme 5).28
The benzyl-linked acid 13a was recently described,31
and the benzoyl-linked acid 14a was prepared as
illustrated in Scheme 6. Our recently reported synthe-
sis of an analogous compound involved a multistep
procedure from a benzyl precursor.31 However, con-
ducting the Marschalk reaction of 15 with 4-cyano-
benzaldehyde at low temperature, to avoid thermal
elimination of the hydroxyl group, directly afforded the
secondary alcohol 31. Oxidation of 31 with pyridinium
dichromate gave the ketone 32, which was selectively
reduced to the anthracenone 33 and hydrolyzed to yield
14a .
Among the hydroxamate analogs, there was a clear
pattern of greater inhibitory activity for those with
N-methyl substitution (type d ) than those with N-
unsubstituted hydroxamic acid groups (type c), as
already seen in other studies.21 Corresponding carbox-
ylic acids (type a ) were generally less active, and
compounds bearing ester functions were inactive (type
b). Within each class of analogs, the potency roughly
correlated with the overall lipophilicity, as already
described for hydroxamic acids and other compounds
(log P values are given in Table 2).21,35
The introduction of methylene units between the
anthracenone nucleus and the hydroxamate moiety
(4c-7c and 4d -8d ) slightly improved potency, and this
was also observed for the carboxylic acids 4a -8a .
Although the activity of carboxylic acid analogs with
branched chain alkyl spacers (10a -12a ) increased as
compared to straight chain spacers (4a -8a ), inverse
results were obtained with the N-methyl-substituted
hydroxamates (10d , 11d vs 4d -8d ).
Biologica l Eva lu a tion
The procedures used were exactly as those described
in our previous studies.1,6,31 Thus, inhibition of the 5-LO
pathway by the novel compounds was evaluated as a
measure of their potency to resolve the inflammatory
aspect of psoriasis, whereas antiproliferative action in
cell cultures may be critical in the management of the
proliferative nature of the disease. HaCaT keratino-
cytes were used as a model for highly proliferative
epidermis of psoriasis.
An tioxid a n t Deter m in a tion . Aside from eicosan-
oids, free radicals and end products derived from lipid
peroxidation are important components in inflammatory
diseases.36 As a measure of their potential to scavenge
free radicals, we determined the reactivities of the
compounds with the stable free radical DPPH.6 Car-
boxylic acid analogs and their corresponding esters gave
values (kDPPH ) 19-24 M-1 s-1) similar to that of
anthralin (24 ( 4.2 M-1 s-1),6 except for the 2-benzoyl

Antipsoriatic Anthrones with Modulated Redox Properties
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 17 2783
Ta ble 1. Deoxyribose Degradation, 5-LO Inhibition in Bovine PMNL, Antiproliferative Activity, and Cytotoxicity against HaCaT
Cells by 9,10-Dihydro-1,8-dihydroxy-9-oxo-2-anthracenecarboxylic and -hydroxamic Acids
IC50 (µM)
compda
4a
5a
6a
7a
8a
9a
10a
11a
12a
13a
14a
4b
5b
6b
7b
8b
Z
X
DD (•OH)b
5-LOc
AA
LDH (mU)e
CH2
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
3.74 ( 0.23
2.67 ( 0.23
2.61 ( 0.38
2.62 ( 0.41
2.29 ( 0.03
ND
3.58 ( 0.30
3.25 ( 0.45
2.47 ( 0.16
<0.15
1.34 ( 0.10
ND
22
19
18
13
10
17
2
1
2
2
2
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
>30
6
4
3
2
6
6
4
5
1
0.6
0.6
0.5
0.4
6
5
5
0.7
4
35
37
>5
>5
>5
>5
>5
>5
>5
>5
>5
2.6
>5
0.5
0.8
1.1
1.8
1.6
0.8
1.5
1.8
1.3
ND
1.8
1.8
1.3
1.5
2.0
2.0
1.5
1.5
1.1
0.8
0.6
0.6
0.8
0.7
1.5
1.5
0.9
0.9
1.8
>5
0.6
ND
ND
ND
ND
ND
ND
128f
ND
142f
ND
ND
ND
ND
ND
146f
142f
ND
ND
ND
142f
ND
ND
ND
ND
ND
135f
ND
192
ND
ND
150f
135f
181
124f
ND
142f
135f
ND
ND
ND
135f
294
(CH2)2
(CH2)3
(CH2)4
(CH2)5
CH3CH
(CH3)2CHCH
PhCH2CH
Ph(CH2)2CH
CH2Ph-4
COPh-4
CH2
(CH2)2
(CH2)3
(CH2)4
(CH2)5
CH3CH
(CH3)2CHCH
PhCH2CH
Ph(CH2)2CH
CH2Ph-4
COPh-4
CH2
(CH2)2
(CH2)3
(CH2)4
CH3CH
(CH3)2CHCH
PhCH2CH
CH2Ph-4
CH2
(CH2)2
(CH2)3
(CH2)4
(CH2)5
CH3CH
(CH3)2CHCH
PhCH2CH
CH2Ph-4
COPh-4
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
NHOH
NHOH
NHOH
NHOH
NHOH
ND
0.33 ( 0.03
0.62 ( 0.03
ND
9b
ND
10b
11b
12b
13b
14b
4c
5c
6c
7c
9c
10c
11c
13c
4d
5d
6d
7d
8d
9d
0.54 ( 0.01
<0.15
0.28 ( 0.03
<0.15
ND
1.89 ( 0.14
1.67 ( 0.31
1.46 ( 0.02
1.38 ( 0.09
1.30 ( 0.11
1.66 ( 0.08
1.04 ( 0.00
ND
1.67 ( 0.08
0.92 ( 0.03
1.50 ( 0.02
1.36 ( 0.05
ND
NHOH
NHOH
NHOH
N(CH3)OH
N(CH3)OH
N(CH3)OH
N(CH3)OH
N(CH3)OH
N(CH3)OH
N(CH3)OH
N(CH3)OH
N(CH3)OH
N(CH3)OH
1.57 ( 0.16
0.86 ( 0.01
1.68 ( 0.13
ND
10d
11d
13d
14d
bufexamac
anthralin
0.92 ( 0.08
2.89 ( 0.14
a
b
Compounds with the structural pattern 8c and 12c,d have not been prepared. Deoxyribose degradation as a measure of hydroxyl-
radical formation. Indicated values are µmol of malondialdehyde/mmol of deoxyribose released by 75 µM test compound (controls < 0.1,
values are significantly different with respect to control; P < 0.01). c Inhibition of 5-HETE and LTB4 biosynthesis in bovine PMNL. Inhibition
was significantly different with respect to that of the control; N ) 3 or more, P < 0.01. Standard errors average 10% of the indicated
d
values. Nordihydroguaiaretic acid (NDGA) was used as the standard inhibitor for 5-LO (IC50 ) 0.4 µM). Antiproliferative activity against
HaCaT cells. Inhibition of cell growth was significantly different with respect to that of the control; N ) 3, P < 0.01. e Activity of LDH
release in HaCaT cells after treatment with 2 µM test compound (N ) 3, SD < 10%). f Values are not significantly different with respect
to vehicle control. ND ) not determined.
derivatives 13a ,b (kDPPH > 100 M-1 s-1, data not
shown), which showed increased reactivity as a result
of their resonance-stabilized C-10 radicals. The reactiv-
ity of N-unsubstituted hydroxamic acid groups (type c)
was up to 3-fold enhanced (kDPPH ) 34-66 M-1 s-1, data
not shown). However, N-methyl-substituted analogs
(type d ) were throughout highly reactive (kDPPH > 100
M-1 s-1, data not shown), reflecting potent antioxidant
capability of the N-methyl hydroxamate group. These
observations confirm the action of hydroxamates as
radical scavengers,17 probably by acting as reducing
agents through their ability to donate hydrogen atoms
or electrons.
induced LPO in bovine brain phospholipid liposomes6
and may thus be helpful in preventing tissue injury. In
good agreement with the results of the DPPH test,
N-methyl-substituted hydroxamates were the most ac-
tive representatives of this series. For example, com-
pound 6d had an IC50 of 11 µM in this model, whereas
anthralin itself was not protective but rather stimulated
LPO both in vivo and in model membranes.7,14 Al-
though much attention has been focused on the iron-
catalyzed hydroxyl-radical generation as the important
step for induction of LPO,37 iron-catalyzed decomposi-
tion of lipid hydroperoxides may also be a driving force.
In either case, a central role for iron in LPO cannot be
questioned.38 As LPO was induced by an azo initiator
rather than by iron in our model, the inhibitory effect
Moreover, these compounds also protected against
2,2′-azobis(2-amidinopropane) hydrochloride (AAPH)-

2784 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 17
Mu¨ller and Prinz
Ta ble 2. Chemical Data of 9,10-Dihydro-1,8-dihydroxy-
9-oxo-2-anthracenecarboxylic and -hydroxamic Acids
of 6d may be the result of its action as a hydrogen atom
donor, consistent with its reactivity against DPPH.
Hyd r oxyl-Ra d ica l Gen er a tion . Further studies on
the redox behavior of the novel series were performed
using the deoxyribose assay.6 The release of malon-
dialdehyde (MDA) is indicative of hydroxyl-radical
generation. Table 1 shows that with the exception of
the carboxylic acid derivatives (type a ), generation of
hydroxyl radicals was substantially reduced with re-
spect to anthralin. In most cases, the release of MDA
decreased to about 50% of that induced by anthralin.
An tip r olifer a tive Activity. The antiproliferative
potential of this series was studied by evaluating the
ability of the compounds to inhibit the proliferation of
HaCaT cells, a rapidly multiplying human keratinocyte
cell line. Proliferation of the keratinocytes was deter-
mined directly by counting the dispersed cells under a
phase-contrast microscope after 48 h of treatment.
It is interesting to note that while the ester deriva-
tives (type b) were not active as 5-LO inhibitors, they
were active as inhibitors of cell growth. As both assays
use intact cell systems, the lack of activity could not
result from the inability of the compounds to cross the
cellular membrane. By contrast, the corresponding
acids showed activity in the 5-LO assay but did not
exhibit antiproliferative activity.
mp
(°C)
yield
(%)
compd
log Pa
formulab
solventc
4a
5a
6a
7a
8a
9a
10a
11a
12a
13a
14a
4b
5b
6b
7b
8b
3.10 (3.51) C16H12O5
220d,e
82 MC/M (9/1)
71 MC/M (9/1)
3.78 (3.97)
3.91 (4.51)
4.22 (5.05)
4.60 (5.59)
3.40 (3.92)
3.90 (4.87)
4.11 (5.34)
4.33 (5.88)
4.10
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
17H14O5
18H16O5
19H18O5
20H20O5
17H14O5
19H18O5
23H18O5
24H20O5
22H16O5
22H14O6
17H14O5
18H16O5
19H18O5
20H20O5
21H22O5
18H16O5
20H20O5
24H20O5
25H22O5
23H18O5
23H16O6
220d,e
201f
181
84
81
79
81
79
72
80
A
A
A
A
A
A
A
169
231g
224g
218g
134g
245d,h
240d
119
69 MC/E (7/3)
83
(5.10)
A
3.93 (3.93)
4.55 (4.36)
4.63 (4.90)
4.97 (5.44)
5.34 (5.98)
4.16 (4.34)
4.77 (5.29)
4.86 (5.89)
5.17 (6.43)
5.34
79 MC/M (9/1)
76 MC/M (9/1)
89 MC
86 MC
81 MC
71 MC
72 MC
80 MC
71 MC
101
123
90
102
143
173
178
112
9b
10b
11b
12b
13b
14b
4c
5c
6c
7c
9c
10c
11c
13c
4d
5d
6d
7d
8d
9d
181-182h 78 MC/H (4/1)
199
5.22 (5.35)
(2.40)
(2.75)
(3.29)
(3.83)
(2.81)
(3.76)
(4.23)
(4.57)
76 MC
16H13NO5 200d
17H15NO5 164d
18H17NO5 156d
19H19NO5 149d
29 MC/M (9/1)
21 MC/M (9/1)
29 MC/M (9/1)
21 MC/M (9/1)
19 MC/M (9/1)
17 MC/M (9/1)
23 MC/M (9/1)
28 MC/M (9/1)
39 MC/M (95/5)
31 MC/M (95/5)
36 MC/M (95/5)
30 MC/M (95/5)
43 MC/M (95/5)
34 MC/M (95/5)
34 MC/M (95/5)
15 MC/M (95/5)
39 MC/M (95/5)
36 MC/M (95/5)
17H15NO5 190d
i
19H19NO5 176d
23H19NO5 168d
The structure-activity relationship trend for the
antiproliferative activity of hydroxamate analogs fol-
lowed that seen with the 5-LO assay. Potency was
significantly improved by methyl substitution on the
hydroxamate nitrogen (type d ). Inserting methylene
groups between the anthracenone nucleus and the
hydroxamate function (4d -8d ) did not affect the po-
tency to any great extent. On the other hand, branched
chain alkyl spacers (10d , 11d ) were somewhat detri-
mental to potency.
22H17NO5 180d
j
(2.64)
(2.99)
(3.53)
(4.07)
(4.61)
(3.05)
(4.00)
(4.47)
17H15NO5 174d
18H17NO5 188d
19H19NO5 165d
20H21NO5 132d
21H23NO5 142d
18H17NO5 179d
20H21NO5 156d
24H21NO5 153d
23H19NO5 136d
23H17NO6 138d
10d
11d
13d
14d
(4.81)
(3.73)
LTB4 can effect keratinocyte proliferation,39,40 and
cultured HaCaT keratinocytes express the 5-LO gene.41
The keratinocyte 5-LO pathway may therefore play a
primary role in skin biology. However, the negative
results obtained with the ester analogs in the 5-LO
assay suggest a different mode of action for the strong
antiproliferative activity of compounds 4b and 5b.
Furthermore, the antiproliferative activity of 1,8-
dihydroxy-9(10H)-anthracenones is clearly independent
of their potency to generate hydroxyl radicals. Kera-
tinocytes were also tested for their susceptibility for the
action of the compounds on plasma membrane integrity.
Cytotoxicity of the cell cultures was assessed by the
activity of lactate dehydrogenase (LDH) released into
the culture medium.42 In contrast to anthralin, which
showed a 2-fold increase in LDH activity as compared
to controls, LDH release after treatment of HaCaT cells
with the most potent inhibitors of cell growth did not
exceed the control values. This further confirms that
appropriate structural modification of anthralin leads
to control of the release of oxygen radicals resulting in
reduced oxidative damage to membrane without sacri-
fice of biological activity.
a
Experimentally determined partition coefficients; values in
parentheses are calculated.48 All new compounds displayed 1H
b
NMR, FTIR, UV, and MS spectra consistent with the assigned
structure. Elemental analyses were within (0.4% of calculated
values. c A ) acetic acid; E ) ether; H ) hexane; M ) methanol;
MC ) methylene chloride. Decomposition. e Literature30 value.
d
f Literature49 mp 187-192 °C. Literature28 value. Literature31
g
h
i
j
value. C: calcd, 65.17; found, 64.53. C: calcd, 70.39; found,
68.84.
the pathogenesis of inflammatory skin disease has been
reported.43 Novel therapeutic strategies are based on
their removal by chelation of iron before formation of
the highly reactive hydroxyl radicals can occur.43
On the basis of this concept, a novel series of anthra-
cenone derivatives with modulated redox properties has
been synthesized, and a number were potent inhibitors
of 5-LO and the growth of keratinocytes in cellular
assays. Replacement of the carboxylic acid function
with the iron-chelating hydroxamic acid provided com-
pounds that had increased inhibitory activity against
5-LO and retained activity against the growth of kera-
tinocytes. N-Methylation appeared important for both
5-LO inhibition and antiproliferative activity and also
supplied antioxidant potential.
Compounds 5d -8d demonstrate that an antiprolif-
erative anthracenone pharmacophore can be modified
such that it contains both antiproliferative activity and
potency against the 5-LO enzyme combined with re-
duced toxicity.
Con clu sion s
Being rich in polyunsaturated fatty acids, the skin is
uniquely vulnerable to oxidative attack by oxygen
radicals, and a central role of these species and iron in

Antipsoriatic Anthrones with Modulated Redox Properties
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 17 2785
with 2 N HCl (pH control), and the resulting precipitate was
suction filtered, washed with water, and dried. The crude
product was purified by flash chromatography to afford a
Exp er im en ta l Section
Melting points were determined with a Bu¨chi 510 melting
point apparatus and are uncorrected. Chromatography refers
to column chromatography on silica gel (E. Merck, 70-230
mesh); eluants are given in Table 2. 1H NMR spectra were
recorded with a Varian EM 390 (90 MHz) or a Bruker
Spectrospin WM 250 (250 MHz) spectrometer, using tetra-
methylsilane as an internal standard. Fourier-transform IR
spectra (KBr) were recorded on a Nicolet 510M FTIR spec-
1
yellow powder (Table 2): FTIR 1623 cm-1 (CO); H NMR (90
MHz, DMSO-d6) δ 12.47 (s, 1H), 12.10 (s, 1H), 10.47 (s, 1H),
8.73 (s, 1H), 7.70-6.80 (m, 5H), 4.37 (s, 2H), 2.70-2.43 (m,
4H), 2.17-1.67 (m, 2H). Anal. (C18H17NO5) C, H, N.
Analogously, compounds 4c, 5c, 7c, 9c-11c, 13c, and 14c
were prepared from 4b, 5b, 7b, 9b-11b, 13b, and 14b,
respectively (Table 2).
trometer. UV spectra were recorded on
a Kontron 810
N-Hyd r oxy-N-m eth yl-4-(9,10-d ih yd r o-1,8-d ih yd r oxy-9-
oxo-2-a n t h r a cen e)b u t a n a m id e (6d ). According to the
method described above, 6b (0.30 g, 0.92 mmol) was treated
with N-methylhydroxylamine-HCl (5.01 g, 60 mmol). The
mixture was extracted with CH2Cl2 (2 × 50 mL), and the
organic phase was washed with cold water (3 × 50 mL), dried
over Na2SO4, and evaporated. The residue was purified by
chromatography, and the product was treated with a small
amount of petroleum ether (40-60) at 0 °C to induce precipita-
tion of yellow crystals (Table 2): FTIR 1619 cm-1 (CO); 1H
NMR (90 MHz, DMSO-d6) δ 12.50 (s, 1H), 12.13 (s, 1H), 9.77
(s, 1H), 7.70-6.80 (m, 5H), 4.37 (s, 2H), 3.10 (s, 3H), 2.73-
2.30 (m, 4H), 2.00-1.70 (m, 2H). Anal. (C19H19NO5) C, H, N.
Analogously, compounds 4d , 5d , 7d -11d , 13d , and 14d
were prepared from 4b, 5b, 7b-11b, 13b, and 14b, respec-
tively (Table 2).
1-Hyd r oxy-8-m eth oxy-4-[1-(4-m eth oxybu tyl)]-9,10-a n -
th r a cen ed ion e (16). To a solution of NaOH (12.0 g, 0.30 mol)
in water (600 mL) was added 1528 (10 g, 39.5 mmol), and the
solution was stirred for 15 min at 40 °C. A solution of Na2S2O4
(12 g, 68.9 mmol) in water (50 mL) was added under N2. The
solution was stirred and heated to 70 °C for 15 min. 4-Meth-
oxybutyraldehyde45 (10 g, 98.0 mmol) was added dropwise, and
the temperature was raised to 90 °C. The reaction mixture
was stirred for 12 h under N2, then cooled to room tempera-
ture, and aerated for 45 min. Water was added (500 mL); the
mixture was acidified by 2 N HCl until it turned orange and
extracted with CH2Cl2 (4 × 200 mL). The combined organic
phase was washed with water (4 × 400 mL) and dried over
Na2SO4. The solvent was evaporated and the residue purified
by chromatography using CH2Cl2/methanol (99-1) to provide
orange crystals (5.3 g, 40%): mp 139 °C; FTIR 1671 (CO), 1634
cm-1 (CO‚‚‚HO); 1H NMR (90 MHz, CDCl3) δ 13.43 (s, 1H),
8.07-7.27 (m, 5H), 4.08 (s, 3H), 3.53-3.25 (m, 2H), 3.32 (s,
3H), 2.88-2.65 (m, 2H), 1.85-1.57 (m, 4H). Anal. (C20H20O5)
C, H.
spectrometer. Mass spectra (EI, unless otherwise stated) were
obtained on a Varian MAT CH5 spectrometer (70 eV). HPLC
(Kontron 420, 735 LC UV detector) was performed on a 250-
× 4-mm column (4- × 4-mm precolumn) packed with LiChro-
spher 100 RP18 (5-µm particles; Merck, Darmstadt, Germany).
Data were recorded on a MacLab data acquisition system
(WissTech, Germany), and analysis was performed with the
software Peaks on an Apple Macintosh computer.
Compounds 4a and 5a ,30 9a -12a ,28 and 13a 31 were prepared
as described.
Gen er a l P r oced u r e for th e Red u ction of 9,10-An -
th r a cen ed ion es to 9(10H)-An th r a cen on es.44 4-(9,10-Di-
h yd r o-1,8-d ih yd r oxy-9-oxo-2-a n th r a cen e)bu ta n oic Acid
(6a ). To a suspension of 20 (0.30 g, 0.88 mmol) in HOAc (15
mL) heated to reflux was added, dropwise over 30 min, a
solution of SnCl2 (2.0 g, 8.86 mmol) in 37% HCl (10 mL). The
solution was refluxed for 6 h and then cooled, and the resulting
crystals were collected by filtration. Recrystallization from
HOAc provided a pale yellow powder (Table 2): FTIR 1694
(COOH), 1623 cm-1 (CO); 1H NMR (90 MHz, DMSO-d6) δ 12.38
(s, 1H), 12.00 (s, 1H), 7.63-6.77 (m, 5H), 4.32 (s, 2H), 2.70-
2.42 (m, 2H), 2.33-2.12 (m, 2H), 2.02-1.67 (m, 2H). Anal.
(C18H16O5) C, H.
Analogously, compounds 7a and 8a were prepared by
reduction of the anthracenones 21 and 23, respectively (Table
2).
4-[(9,10-Dih yd r o-1,8-d ih yd r oxy-9-oxo-2-a n th r a cen yl)-
ca r bon yl]ben zoic Acid (14a ). A suspension of 33 (0.20 g,
0.52 mmol) in water (15 mL), 96% H2SO4 (10 mL), and HOAc
(10 mL) was refluxed for 3 days (TLC control). Then the
mixture was cooled to room temperature, treated with water
(10 mL), and allowed to stand overnight. The violet precipitate
was filtered by suction, washed with water, and dried (Table
1
2): FTIR 1694 cm-1; H NMR (250 MHz, DMSO-d6) δ 12.62
(s, 1H), 11.89 (s, 1H), 8.11-6.89 (m, 9H), 4.59 (s, 2H). Anal.
(C22H14O6) C, H.
2-[1-(4-Br om obu tyl)]-1,8-d ih yd r oxy-9,10-a n th r a cen ed i-
on e (17). A suspension of 16 (5.00 g, 14.69 mmol) in glacial
acetic acid (100 mL) was heated to reflux. To the resulting
solution was added dropwise 62% HBr (50 mL), and the
solution was refluxed for 3 h. The solution was then cooled to
room temperature, and water (50 mL) was added. After 30
min the precipitate was filtered by suction and washed with
water (4 × 50 mL). The residue was dried under vacuum at
50 °C and purified by chromatography to afford orange-yellow
Gen er a l P r oced u r e for th e P r ep a r a tion of 2-Su bsti-
tu ted 1,8-Dih yd r oxy-9(10H)-a n th r a cen on e Meth yl Ca r -
boxyla tes. Meth yl 4-(9,10-Dih yd r o-1,8-d ih yd r oxy-9-oxo-
2-a n th r a cen e)bu ta n oa te (6b). A solution of 6a (0.5 g, 1.60
mmol) in absolute methanol (50 mL) and 96% H2SO4 (0.2 mL)
was refluxed for 6 h (TLC control). The solution was then
cooled to room temperature, treated with water (50 mL), and
extracted with CH2Cl2. The organic phase was washed with
water and dried over Na2SO4, and the solution was evaporated.
The residue was purified by chromatography, and the product
was treated with a small amount of hexane or petroleum ether
(40-60) to induce precipitation of a pale yellow powder (Table
crystals (4.7 g, 85%): mp 125 °C dec; FTIR 1669, 1621 cm-1
;
1H NMR (90 MHz, CDCl3) δ 12.40 (s, 1H), 12.02 (s, 1H), 7.85-
7.17 (m, 5H), 3.28 (t, J ) 6 Hz, 2H), 2.73 (t, J ) 6 Hz, 2H),
2.05-1.75 (m, 4H). Anal. (C18H15BrO4) C, H.
1
2): FTIR 1725 (CO2Me), 1631 cm-1 (CO); H NMR (90 MHz,
4-(9,10-Dih ydr o-1,8-dih ydr oxy-9,10-dioxo-2-an th r acen e)-
bu ta n -1-ol (18). 17 (4.50 g, 11.99 mmol) was suspended in a
solution of 15% water in HMPA (50 mL), and the temperature
was slowly raised to 130 °C. The mixture was stirred at 130
°C for 6 h (TLC control), then cooled to room temperature,
poured into water (1 L), and extracted with ether (3 × 200
mL). The combined organic phase was washed with water (3
× 400 mL), dried over Na2SO4, evaporated, and purified by
chromatography using ether to give orange crystals (3.0 g,
CDCl3) δ 12.60 (s, 1H), 12.32 (s, 1H), 7.57-6.73 (m, 5H), 4.27
(s, 2H), 3.65 (s, 3H), 2.80-2.60 (m, 2H), 2.48-2.27 (m, 2H),
2.15-1.85 (m, 2H). Anal. (C19H18O5) C, H.
Analogously, compounds 4b, 5b, and 7b-14b were prepared
from 4a , 5a , and 7a -14a , respectively (Table 2).
Gen er a l P r oced u r e for th e P r ep a r a tion of 2-Su bsti-
tu ted 1,8-Dih yd r oxy-9(10H)-a n th r a cen on e Hyd r oxa m ic
Acid s. N-Hyd r oxy-4-(9,10-d ih yd r o-1,8-d ih yd r oxy-9-oxo-
2-a n th r a cen e)bu ta n a m id e (6c). To a solution of Na (2.07
g, 90 mmol) in absolute methanol (40 mL) was added a solution
of hydroxylamine-HCl (4.17 g, 60 mmol) in methanol (40 mL)
at 0-5 °C, after which the mixture was suction filtered. The
filtrate was added dropwise to a suspension of 6b (0.30 g, 0.92
mmol) in absolute methanol (15 mL) at 0-5 °C under N2. The
clear, yellow-orange solution was stirred until the reaction was
completed (TLC control). The solution was then neutralized
1
81%): mp 149 °C; FTIR 3330, 1669, 1619 cm-1; H NMR (90
MHz, DMSO-d6) δ 11.57 (s, 2H), 7.80-7.17 (m, 5H), 4.40 (s,
1H), 3.57-3.35 (m, 2H), 2.70-2.42 (m, 2H), 1.77-1.32 (m, 4H).
Anal. (C18H16O5) C, H.
4-(9,10-Dih ydr o-1,8-dih ydr oxy-9,10-dioxo-2-an th r acen e)-
bu ta n oic Acid (19). A solution of 18 (2.0 g, 6.40 mmol) in
dry DMF (25 mL) and PDC (9.64 g, 25.61 mmol) was stirred
at room temperature for 6 h. The solution was poured into

2786 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 17
Mu¨ller and Prinz
water (500 mL), and the product was extracted with CH2Cl2
(4 × 100 mL). The combined organic phase was washed with
water (4 × 200 mL), dried over Na2SO4, and evaporated. The
resulting residue (60 mL) was treated with a small amount of
petroleum ether (40-60), shaken thoroughly, and allowed to
stand at 0 °C. The precipitate was filtered by suction, and
the crude product was used in the subsequent esterification
step.
temperature for 10 min. A solution of Na2S2O4 (12 g, 68.9
mmol) in water (50 mL) was added under N2, and the solution
turned yellow-brown. The solution was then cooled to 0-5
°C and stirred for 30 min. 4-Cyanobenzaldehyde (12 g, 91.51
mmol) in THF (50 mL) was added dropwise, and the reaction
mixture was allowed to stir at 0-5 °C for 12 h under nitrogen.
The mixture was aerated for 45 min, poured into water (500
mL), and acidified by 2 N HCl until it turned orange. The
product was extracted with CH2Cl2 (4 × 200 mL). The
combined organic phase was washed with water (3 × 500 mL),
dried over Na2SO4, and evaporated. The resulting residue was
purified by chromatography using CH2Cl2/methanol (99-1) to
give orange crystals (5.6 g, 37%): mp 223 °C; FTIR 3489, 2229,
1669, 1623 cm-1; 1H NMR (90 MHz, DMSO-d6) δ 13.43 (s, 1H),
8.03-7.43 (m, 9H), 6.33 (m, 1H), 6.17 (m, 1H), 3.92 (s, 3H).
Anal. (C23H15NO5) C, H, N.
Meth yl 4-(9,10-Dih yd r o-1,8-d ih yd r oxy-9,10-d ioxo-2-a n -
th r a cen e)bu ta n oa te (20). A suspension of 19 in methanol
(500 mL) and 96% H2SO4 (5 mL) was refluxed for 24 h. The
reaction mixture was cooled to room temperature, kept at 0
°C for 2 h, then filtered by suction, washed with precooled
methanol (100 mL), and dried under vacuum. The residue was
purified by chromatography to give orange crystals (1.3 g,
overall 59%): mp 139 °C; FTIR 1742, 1661, 1619 cm-1 1H
;
NMR (90 MHz, CDCl3) δ 12.38 (s, 1H), 12.00 (s, 1H), 7.85-
7.17 (m, 5H), 3.68 (s, 3H), 2.75 (m, 2H), 2.13-1.85 (m, 2H),
1.73-1.47 (m, 2H). Anal. (C19H16O6) C, H.
4-[(9,10-Dih yd r o-9,10-d ioxo-1-h yd r oxy-8-m et h oxy-2-
a n th r a cen yl)ca r bon yl]ben zon itr ile (32). A solution of 31
(2.00 g, 5.19 mmol) in dry DMF (25 mL) and PDC (7.81 g, 20.76
mmol) was stirred at room temperature for 1 h. The mixture
was poured into water (500 mL), and the product was extracted
with CH2Cl2 (3 × 100 mL). The combined organic phase was
washed with water (4 × 200 mL), dried over Na2SO4, and
evaporated. The resulting residue was purified by chroma-
tography using CH2Cl2/methanol (99-1) to give orange crystals
(1.7 g, 86%): mp 218 °C dec; FTIR 2232, 1671, 1631 cm-1; 1H
NMR (90 MHz, CDCl3) δ 13.38 (s, 1H), 8.02-7.26 (m, 9H), 4.08
(s, 3H). Anal. (C23H13NO5) C, H, N.
5-(9,10-Dih ydr o-1,8-dih ydr oxy-9,10-dioxo-2-an th r acen e)-
va ler on itr ile (21). NaCN (1.10 g, 22.5 mmol) was suspended
in dry DMSO (40 mL) and heated to 90 °C (oil bath). The oil
bath was removed, and to the resulting solution was added
slowly a solution of 17 (1.69 g, 4.50 mmol) in DMSO (15 mL).
The solution was stirred until the reaction was completed (TLC
control). The solution was poured into water (500 mL), and
the product was extracted with CH2Cl2 (3 × 50 mL). The
combined organic phase was washed with water (3 × 100 mL),
dried over Na2SO4, and evaporated. The resulting residue was
purified by chromatography to give orange crystals (0.9 g,
62%): mp 175 °C; FTIR 2244 (CN), 1667 (CO), 1621 cm-1
4-[(9,10-Dih yd r o-1,8-d ih yd r oxy-9-oxo-2-a n th r a cen yl)-
ca r bon yl]ben zon itr ile (33). According to the method de-
scribed for 6a , 32 (0.30 g, 0.78 mmol) was reduced to yield a
violet powder (0.26 g, 83%): mp 230 °C dec; FTIR 2231, 1665,
1
(CO‚‚‚OH); H NMR (90 MHz, CDCl3) δ 12.43 (s, 1H), 12.02
(s, 1H), 7.87-7.18 (m, 5H), 2.78 (m, 2H), 2.42 (m, 2H), 1.93-
1
1615 cm-1; H NMR (250 MHz, CDCl3) δ 12.91 (s, 1H), 11.98
1.70 (m, 4H). Anal. (C19H15NO4) C, H, N.
(s, 1H), 7.95-6.93 (m, 9H), 4.45 (s, 2H). Anal. (C22H13NO4)
Meth yl 4-Oxobu ta n oa te. To a suspension of PCC (30.0
g, 139.2 mmol) in dry CH2Cl2 (200 mL) was added in one
portion methyl 4-hydroxybutanoate46 (11.8 g, 100 mmol) in
CH2Cl2 (30 mL). The mixture was stirred at room temperature
for 3 h. Then the product was extracted with ether (4 × 200
mL), thoroughly shaken, and filtered through a short column
(SiO2, ether), and the solvent was removed in vacuo. The
crude product was used in the subsequent step: 1H NMR (90
MHz, CDCl3) δ 9.92 (s, 1H), 3.67 (s, 3H), 2.90-2.03 (m, 4H).
Met h yl 6-Oxoh exa n oa t e.47 ꢀ-Caprolactone (11.4 g, 100
mmol) in absolute methanol (200 mL) and concentrated H2SO4
(0.5 mL) was heated to reflux for 12 h. The mixture was then
cooled in an ice bath, and anhydrous NaHCO3 (1.5) was added.
The mixture was stirred for 20 min, and the solvent was
removed in vacuo. The product was oxidized directly with PCC
(30.0 g, 139.2 mmol) as described above without purification.
Meth yl 4-(9,10-Dih yd r o-9,10-d ioxo-1-h yd r oxy-8-m eth -
oxy-2-a n th r a cen e)bu ta n oa te (22). This compound was
prepared from 1528 and methyl 4-oxobutanoate according to
the method described for 16. The crude acid was used in the
subsequent esterification step, which was performed as de-
scribed for 6b to afford orange crystals (0.67 g, overall 12%):
C, H, N.
Biologica l Assa y Meth od s. Determination of the reducing
activity against 2,2-diphenyl-1-picrylhydrazyl,6 degradation of
2-deoxy-d-ribose,6 inhibition of lipid peroxidation,31 bovine
PMNL 5-LO assay,6 HaCaT keratinocyte proliferation assay,31
and LDH release1 were described previously in full detail.
Ack n ow led gm en t. We thank Dr. S. Dove, Regens-
burg, for his kind help in calculating partition coef-
ficients and Mrs. C. Braun for her excellent technical
assistance.
Refer en ces
(1) For part 3, see: Mu¨ller, K.; Huang, H.-S.; Wiegrebe, W. Anti-
psoriatic anthrones with modulated redox properties. 3. 10-Thio-
substituted 1,8-dihydroxy-9(10H)-anthracenones as inhibitors of
keratinocyte growth, 5-lipoxygenase, and the formation of 12(S)-
HETE in mouse epidermis. J . Med. Chem. 1996, 39, 3132-3138.
(2) Keme´ny, L.; Ruzicka, T.; Braun-Falco, O. Dithranol: a review
of the mechanism of action in the treatment of psoriasis vulgaris.
Skin Pharmacol. 1990, 3, 1-20.
(3) Wiegrebe, W.; Mu¨ller, K. Treatment of psoriasis with anthrones
- chemical principles, biochemical aspects, and approaches to the
design of novel derivatives. Skin Pharmacol. 1995, 8, 1-24.
(4) Mu¨ller, K. Antipsoriatic anthrones: aspects of oxygen radical
formation, challenges and prospects. Gen. Pharmacol. 1996, 27,
1325-1335.
(5) Mu¨ller, K. Antipsoriatic and proinflammatory action of anthra-
lin. Implications for the role of oxygen radicals. Biochem.
Pharmacol. 1997, 53, in press.
(6) Mu¨ller, K.; Gu¨rster, D.; Piwek, S.; Wiegrebe, W. Antipsoriatic
anthrones with modulated redox properties. 1. Novel 10-
substituted 1,8-dihydroxy-9(10H)-anthracenones as inhibitors of
5-lipoxygenase. J . Med. Chem. 1993, 36, 4099-4107.
(7) Mu¨ller, K.; Wiegrebe, W.; Younes, M. Formation of active oxygen
species by dithranol, III. Dithranol, active oxygen species and
lipid peroxidation in vivo. Arch. Pharm. (Weinheim, Ger.) 1987,
320, 59-66.
(8) Miller, D. M.; Buettner, G. R.; Aust, S. D. Transition metals as
catalysts of “autoxidation” reactions. Free Radical Biol. Med.
1990, 8, 95-108.
(9) Halliwell, B. The biological significance of oxygen-derived spe-
cies. In Active Oxygen in Biochemistry; Valentine, J . S., Foote,
C. S., Greenberg, A., Liebman, J . F., Eds.; Blackie Academic &
Professional: London, 1995; pp 313-335.
1
mp 144 °C; FTIR 1733, 1671, 1634 cm-1; H NMR (90 MHz,
CDCl3) δ 13.32 (s, 1H), 8.05-7.23 (m, 5H), 4.05 (s, 3H), 3.67
(s, 3H), 2.77 (m, 2H), 2.38 (m, 2H), 2.18-1.87 (m, 2H). Anal.
(C20H18O6) C, H.
Meth yl 6-(9,10-Dih yd r o-9,10-d ioxo-1-h yd r oxy-8-m eth -
oxy-2-a n th r a cen e)h exa n oa te (23). This compound was
prepared from 1528 and methyl 6-oxohexanoate according to
the method described for 16. The crude acid was used in the
subsequent esterification step, which was performed as de-
scribed for 6b to afford orange crystals (2.3 g, overall 31%):
1
mp 104 °C; FTIR 1731, 1665, 1631 cm-1; H NMR (90 MHz,
CDCl3) δ 13.43 (s, 1H), 8.17-7.28 (m, 5H), 4.12 (s, 3H), 4.03
(s, 3H), 2.91-2.65 (m, 2H), 2.52-2.23 (m, 2H), 1.90-1.40 (m,
6H). Anal. (C22H22O6) C, H.
Anthracenedione precursors 24-30 were prepared as de-
scribed.28
4-[(9,10-Dih yd r o-9,10-d ioxo-1-h yd r oxy-8-m et h oxy-2-
a n th r a cen yl)h yd r oxym eth yl]ben zon itr ile (31). To a solu-
tion of NaOH (12 g, 0.30 mol) in methanol (600 mL) was added
1528 (10 g, 39.5 mmol), and the solution was stirred at room

Antipsoriatic Anthrones with Modulated Redox Properties
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 17 2787
(10) Halliwell, B. Antioxidant characterization. Methodology and
mechanism. Biochem. Pharmacol. 1995, 49, 1341-1348.
(11) Winterbourn, C. C. Superoxide as an intracellular radical sink.
Free Radical Biol. Med. 1993, 14, 85-90.
(32) J ones, G. H.; Venuti, M. C.; Young, J . M.; Krishna Murthy, D.
V.; Loe, B. E.; Simpson, R. A.; Berks, A. H.; Spires, D. A.;
Maloney, P. J .; Kruseman, M.; Rouhafza, S.; Kappas, K. C.;
Beard, C. C.; Unger, S. H.; Cheung, P. S. Topical nonsteroidal
antipsoriatic agents: 1. 1,2,3,4-Tetraoxygenated naphthalene
derivatives. J . Med. Chem. 1986, 29, 1504-1511.
(33) Venuti, M. C.; Loe, B. E.; J ones, G. H.; Young, J . M. Topical
nonsteroidal antipsoriatic drugs. 2. 2,3-(Alkylidenedioxy)naph-
thalene analogues of lonapalene. J . Med. Chem. 1988, 31, 2132-
2136.
(34) Batt, D. G.; Maynard, G. D.; Petraitis, J . J .; Shaw, J . E.;
Galbraith, W.; Harris, R. R. 2-Substituted-1-naphthols as potent
5-lipoxygenase inhibitors with topical antiinflammatory activity.
J . Med. Chem. 1990, 33, 360-370.
(35) Hammond, M. L.; Zambias, R. A.; Chang, M. N.; J ensen, N. P.;
McDonald, J .; Thompson, K.; Boulton, D. A.; Kopka, I. E.; Hand,
K. M.; Opas, E. E.; Luell, S.; Bach, T.; Davies, P.; MacIntyre, D.
E.; Bonney, R. J .; Humes, J . L. Antioxidant-based inhibitors of
leukotriene biosynthesis. The discovery of 6-[1-[2-(hydroxy-
methyl)phenyl]-1-propen-3-yl]-2,3-dihydro-5-benzofuranol, a po-
tent topical antiinflammatory agent. J . Med. Chem. 1990, 33,
908-918.
(12) Halliwell, B.; Gutteridge, J . M. C. Role of free radicals and
catalytic metal ions in human disease: an overview. Methods
Enzymol. 1990, 186, 1-85.
(13) Mu¨ller, K.; Kappus, H. Hydroxyl radical formation by dithranol.
Biochem. Pharmacol. 1988, 37, 4277-4280.
(14) Mu¨ller, K.; Gu¨rster, D. Hydroxyl radical damage to DNA sugar
and model membranes induced by anthralin (dithranol). Bio-
chem. Pharmacol. 1993, 46, 1695-1704.
(15) Trenam, C. W.; Blake, D. R.; Morris, C. J . Skin inflammation:
reactive oxygen species and the role of iron. J . Invest. Dermatol.
1992, 99, 675-682.
(16) Hider, R. C.; Hall, A. D. Clinically useful chelators of tripositive
elements. Prog. Med. Chem. 1991, 28, 41-173.
(17) Green, E. S. R.; Evans, H.; Rice-Evans, P.; Davies, M. J .; Salah,
N.; Rice-Evans, C. The efficacy of monohydroxamates as free
radical scavenging agents compared with di- and trihydrox-
amates. Biochem. Pharmacol. 1993, 45, 357-366.
(18) Musser, J . H.; Kreft, A. F. 5-Lipoxygenase: properties, phar-
macology, and the quinolinyl(bridged)aryl class of inhibitors. J .
Med. Chem. 1992, 35, 2501-2524.
(19) Corey, E. J .; Cashman, J . R.; Kantner, S. S.; Wright, S. W.
Rationally designed, potent competitive inhibitors of leukotriene
biosynthesis. J . Am. Chem. Soc. 1984, 106, 1503-1504.
(20) Summers, J . B.; Mazdiyasni, H.; Holms, J . H.; Ratajczyk, J . D.;
Dyer, R. D.; Carter, G. W. Hydroxamic acid inhibitors of
5-lipoxygenase. J . Med. Chem. 1987, 30, 574-580.
(21) Summers, J . B.; Kim, K. H.; Mazdiyasni, H.; Holms, J . H.;
Ratajczyk, J . D.; Stewart, A. O.; Dyer, R. D.; Carter, G. W.
Hydroxamic acid inhibitors of 5-lipoxygenase: quantitative
structure-activity relationships. J . Med. Chem. 1990, 33, 992-
998.
(22) Huang, F.-C.; Shoupe, T. S.; Lin, C. J .; Lee, T. D. Y.; Chan, W.-
K.; Tan, J .; Schnapper, M.; Suh, J . T.; Gordon, R. J .; Sonnino,
P. A.; Sutherland, C. A.; Van Inwegen, R. G.; Coutts, S. M.
Differential effects of a series of hydroxamic acid derivatives on
5-lipoxygenase and cyclooxygenase from neutrophils and 12-
lipoxygenase from platelets and their in vivo effects on inflam-
mation and anaphylaxis. J . Med. Chem. 1989, 32, 1836-1842.
(23) Wright, S. W.; Harris, R. R.; Kerr, J . S.; Green, A. M.; Pinto, D.
J .; Bruin, E. M.; Collins, R. J .; Dorow, R. L.; Mantegna, L. R.;
Sherk, S. R.; Covington, M. B.; Nurnberg, S. A.; Welch, P. K.;
Nelson, M. J .; Magolda, R. L. Synthesis, chemical, and biological
properties of vinylogous hydroxamic acids: dual inhibitors of
5-lipoxygenase and IL-1 biosynthesis. J . Med. Chem. 1992, 35,
4061-4068.
(36) Winyard, P. G.; Morris, C. J .; Winrow, V. R.; Zaidi, M.; Blake,
D. R. Free radical pathways in the inflammatory response. New
Comp. Biochem. 1994, 28, 361-383.
(37) Braughler, J . M.; Duncan, L. A.; Chase, R. L. The involvement
of iron in lipid peroxidation. Importance of ferric to ferrous ratios
in initiation. J . Biol. Chem. 1986, 261, 10282-10289.
(38) Aust, S. D.; Miller, D. M.; Samokyszyn, V. M. Iron redox
reactions and lipid peroxidation. Methods Enzymol. 1990, 186,
457-463.
,
(39) Kragballe, K.; Desjarlais, L.; Voorhees, J . J . Leukotrienes B4
C4 and D4 stimulate DNA synthesis in cultured human epider-
mal keratinocytes. Br. J . Dermatol. 1985, 113, 43-52.
(40) Chan, C. C.; Duhamel, L.; Ford-Hutchinson, A. Leukotriene B4
and 12-hydroxyeicosatetraenoic acid stimulate epidermal pro-
liferation in vivo in the guinea pig. J . Invest. Dermatol. 1985,
85, 333-334.
(41) J anssen-Timmen, U.; Vickers, P. J .; Wittig, U.; Lehmann, W.
D.; Stark, H.-J .; Fusening, N. E.; Rosenbach, T.; Rådmark, O.;
Samuelsson, B.; Habenicht, A. J . R. Expression of 5-lipoxygenase
in differentiating human skin keratinocytes. Proc. Natl. Acad.
Sci. U.S.A. 1995, 92, 6966-6970.
(42) Bonnekoh, B.; Farkas, B.; Geisel, J .; Mahrle, G. Lactate dehy-
drogenase release as an indicator of dithranol-induced mem-
brane injury in cultured human keratinocytes. Arch. Dermatol.
Res. 1990, 282, 325-329.
(24) Ohemeng, K. A.; Appolina, M. A.; Nguyen, V. N.; Schwender, C.
F.; Singer, M.; Steber, M.; Ansell, J .; Argentieri, D.; Hageman,
W. Synthesis and 5-lipoxygenase inhibitory activities of some
novel 2-substituted 5-benzofuran hydroxamic acids. J . Med.
Chem. 1994, 37, 3663-3667.
(43) Trenam, C. W.; Dabbagh, A. J .; Blake, D. R.; Morris, C. J . The
role of iron in an acute model of skin inflammation induced by
reactive oxygen species. Br. J . Dermatol. 1992, 126, 250-256.
(44) Prinz, H.; Wiegrebe, W.; Mu¨ller, K. Synthesis of anthracenones.
1. Sodium dithionite reduction of peri-substituted anthracene-
diones. J . Org. Chem. 1996, 61, 2853-2856.
(45) Stetter, H.; Leinen, H. T. Addition von Aldehyden an aktivierte
Doppelbindungen, XXXIII. Synthesen und Reaktionen von ether-
und esterhaltigen γ-Diketonen. (Addition of aldehydes to acti-
vated double bonds, XXXIII. Syntheses and reactions of γ-dike-
tones containing ether- or ester groups.) Chem. Ber. 1983, 116,
254-263.
(46) Machleidt, H.; Cohnen, E.; Tschesche, R. Synthesen von D,L-
Mevalonsa¨ure-3,5-cyclophosphat und D,L-Mevalonsa¨ure-5-phos-
phat. (Syntheses of D,L-mevalonic acid 3,5-cyclophosphate and
D,L-mevalonic acid 5-phosphate.) Liebigs Ann. Chem. 1962, 655,
70-80.
(47) Fujita, I.; Tamura, Y.; Tani, H. ω-Formyl valerates. J apan Patent
70 72,338; Chem. Abstr. 1970, 72, 110817r.
(48) Leo, A. J . Methods of calculating partition coefficients. In
Comprehensive Medicinal Chemistry; Hansch, C., Sammes, P.
G., Taylor, J . B., Eds.; Pergamon Press: Oxford, 1990; Vol. 4,
pp 295-319.
(49) Takahashi, I.; Terashima, S. Studies on the synthesis of 4-[1,8-
dioxygenated-9,10-dioxoanthracen(or anthracen)-2-yl]butanoic
acid derivatives. Chem. Pharm. Bull. 1982, 30, 4539-4544.
(25) Hamer, R. R. L.; Tegeler, J . J .; Kurtz, E. S.; Allen, R. C.; Bailey,
S. C.; Elliot, M. E.; Hellyer, L.; Helsley, G. C.; Przekop, P.; Freed,
B. S.; White, J .; Martin, L. L. Dibenzoxepinone hydroxylamines
and hydroxamic acids: dual inhibitors of cyclooxygenase and
5-lipoxygenase with potent topical antiinflammatory activity. J .
Med. Chem. 1996, 39, 246-252.
(26) Brooks, C. D. W.; Summers, J . B. Modulators of leukotriene
biosynthesis and receptor activation. J . Med. Chem. 1996, 39,
2629-2654.
(27) Krohn, K. Synthesis of anthracyclinones by electrophilic and
nucleophilic addition to anthraquinones. Tetrahedron 1990, 46,
291-318.
(28) Prinz, H.; Mu¨ller, K. 2-Anthracenonyl acetic acids as 5-lipoxy-
genase inhibitors. Arch. Pharm. Pharm. Med. Chem. 1996, 329,
262-266.
(29) Hutchins, R. O.; Taffer, I. M. Aqueous polar aprotic solvents.
Efficient sources of nucleophilic oxygen. J . Org. Chem. 1983, 48,
1360-1362.
(30) Tanzer, H.; Seidel, M.; Wiegrebe, W. Hydrophilic derivatives of
dithranol. Arch. Pharm. (Weinheim, Ger.) 1988, 321, 447-449.
(31) Mu¨ller, K.; Leukel, P.; Ziereis, K.; Gawlik, I. Antipsoriatic
anthrones with modulated redox properties. 2. Novel derivatives
of chrysarobin and isochrysarobinsantiproliferative activity and
5-lipoxygenase inhibition. J . Med. Chem. 1994, 37, 1660-1669.
J M9701785