A large-scale synthesis of the bioreductive drug 1,4-bis{[2-(dimethylamino)ethyl]amino}-5,8-dihydroxyanthracene-9,10-dione bis-N-oxide (AQ4N)

Article abstract of DOI:10.1039/a905611d

A large-scale synthesis of the bis-bioreductive drug 1,4-bis{[2-(dimethylamino)ethyl]amino}-5,8-dihydroxy-anthracene-9,10-dione bis-N-oxide (AQ4N) has been developed. This six-step synthesis provides AQ4N in 20% overall yield from readily available tetrachlorophthalic anhydride. The key step was a KF-NaF-mediated conversion of 3,6-dichlorophthalic anhydride to 3,6-difluorophthalic anhydride, which could be achieved in 77% yield on a 100 g scale. A trace impurity in AQ4N was determined (by LC-MS and independent synthesis) to be the mono-N-oxide 1-amino-4-[2-(dimethylamino)ethyl]amino-5,8-dihydroxyanthracene-9,10-dione N-oxide. This is formed spontaneously from AQ4N under a number of conditions, including during HPLC on reversed-phase columns. The Royal Society of Chemistry 1999.

Full text of DOI:10.1039/a905611d

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A large-scale synthesis of the bioreductive drug 1,4-bis{[2-(dimethyl-
amino)ethyl]amino}-5,8-dihydroxyanthracene-9,10-dione bis-N-
oxide (AQ4N)
Ho H. Lee and William A. Denny
Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences,
The University of Auckland, Private bag 92019, Auckland, New Zealand
Received (in Cambridge, UK) 12th July 1999, Accepted 12th August 1999
A large-scale synthesis of the bis-bioreductive drug 1,4-bis{[2-(dimethylamino)ethyl]amino}-5,8-dihydroxy-
anthracene-9,10-dione bis-N-oxide (AQ4N) has been developed. This six-step synthesis provides AQ4N in 20%
overall yield from readily available tetrachlorophthalic anhydride. The key step was a KF–NaF-mediated conversion
of 3,6-dichlorophthalic anhydride to 3,6-difluorophthalic anhydride, which could be achieved in 77% yield on a 100 g
scale. A trace impurity in AQ4N was determined (by LC-MS and independent synthesis) to be the mono-N-oxide 1-
amino-4-[2-(dimethylamino)ethyl]amino-5,8-dihydroxyanthracene-9,10-dione N-oxide. This is formed spontaneously
from AQ4N under a number of conditions, including during HPLC on reversed-phase columns.
Introduction
Results and discussion
1
,4-Bis{[2-(dimethylamino)ethyl]amino}-5,8-dihydroxyanthra-
Initial studies of the preparation of 2 from 1,4-diamino-5,8-
7,8
cene-9,10-dione bis-N-oxide 1 (AQ4N) is a bis-bioreductive
dihydroxyanthraquinone 4 by the method
of Scheme 1
agent developed as a potential hypoxia-selective cytotoxin for
showed that the leuco compound 5 is formed in low purity.
Because it is difficult to purify further due to significant instabil-
ity, it is usually converted directly to 2, which is purified by
extensive chromatography, followed by crystallisation. This
gives material of 90–97% purity in about 30% overall yield
from 3.
1,2
cancer therapy. It is a member of the general class of pro-
intercalators, where oxygen-inhibited cellular reduction of the
N-oxides demasks cationic amine functions, greatly increasing
DNA-binding affinity and thus cytotoxicity (the latter usually
3,4
4–6
through topoisomerase inhibition). Several studies
have
shown that 1 has activity against hypoxic cells in a number of
tumour models, and a clinical trial is planned. It has been pre-
pared by oxidation of the bisamine precursor 2 (AQ4), which in
turn has been prepared from either 3 or 4 by reduction to the
corresponding leuco derivative 5, reaction of this with excess of
N,N-dimethylethylenediamine, and reoxidation of the product
An alternative preparation of 2 from 1,4-difluoro-5,8-
dihydroxy derivative 8 has been reported (Scheme 2). We
9
7,8
(
usually by atmospheric oxygen) (Scheme 1). Because this
Scheme 2 Synthesis of anthraquinone 8. Reagents: i, Me N(CH ) -
2
2 2
NH ; ii, Me N(CH ) NH , pyridine; iii, various; iv, hydroquinone,
2
2
2
2
2
AlCl3.
evaluated the more readily available 1,4-dichloroanthraquinone
analogues 6 and 7, but these gave only trace amounts of
10
product. The only reported synthesis of 8 is from the expen-
sive difluorophthalic anhydride 9; it could not be prepared from
11
6
, although such an exchange has been reported for the corre-
sponding deoxy analogues. Synthesis of 9 has been reported in
Scheme
1
Literature synthesis of AQ4N. Reagents: i, NaOH,
six steps (overall 40% yield) from 2,5-difluorobenzoyl chloride,
Na S O , H O; ii, Me N(CH ) NH , EtOH; then air oxidation; iii,
2
2
4
2
2
2
2
2
10
MCPBA, CH Cl .
which is commercially available but relatively expensive.
A
2
2
five-step synthesis of the diacid precursor of 9 from 2,3-
dimethylaniline has also been reported, but the overall yield
was only 8%.
12
method, although direct, appeared to have limitations, we
report here the development of an alternative synthetic route,
able to provide 1 on a large scale.
We therefore chose to prepare 9 from the cheap and readily
J. Chem. Soc., Perkin Trans. 1, 1999, 2755–2758
This journal is © The Royal Society of Chemistry 1999
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Table 1 Cytotoxicities of AQ4 analogues and side products in murine
P388 leukaemia cells
Compound
IC50 (nM)
1
(AQ4N)
(AQ4)
330
6.6
880
2
6
7
1
1
>20 000
Scheme 3 Synthesis of anhydride 9. Reagents: i, Zn (5 wt-%), aq.
NaOH; ii, Zn (10 wt-%), NaOH; then azeotrope (toluene); iii, KF–NaF
melt; then sublime.
available tetrachlorophthalic anhydride 10 (Scheme 3). This
13
can be dechlorinated stepwise, first to 3,4,6-trichlorophthalic
acid 11 and then to 3,6-dichlorophthalic acid, which can be
14
dehydrated to give 3,6-dichlorophthalic anhydride 12 in 72%
overall yield. Separate and well defined conditions are required
to achieve a clean product in each reduction step, and combin-
15
ing these leads to less pure material. A critical step was con-
16
version of 12 to 9. This had been reported once on a very
small scale using a KF melt. Several modifications to this
method, including the use of a mixed KF–NaF reagent,
allowed conversion in up to 77% yield on a large scale (up to
1
00 g). The chlorofluoro anhydride 13 was a minor (<10%)
impurity; attempts to reduce the amount of this by longer
reaction times led to a significant decrease in the yield of 9.
Friedel–Crafts alkylation of 9 by modification of the
10
reported method gave 8 in 98% yield, suitable for direct use in
the next step, on a large scale. Compound 8 was treated with
N,N-dimethylethylenediamine (Aldrich, 95%) in pyridine at
room temperature for 58 h, and the crude product (on a 100 g
scale) was filtered through a short column of silica gel to separ-
ate the required AQ4 product 2 from a small amount of the
Scheme 5 (a) Synthesis of chloro impurity 17. Reagents: i, hydro-
quinone, NaCl, AlCl ; then H N(CH ) NMe ; ii, 3-phenyl-2-(phenyl-
3
2
2
2
2
4
-chloro monoamine 14, presumably derived from the corre-
sulfonyl)oxaziridine, CH Cl . (b) Synthesis of impurity 19. Reagents: i,
2
2
sponding chlorofluoro anhydride 13 (Scheme 4). The AQ4 so
NH3 (gas), pyridine; then H N(CH ) NMe ; ii, 3-phenyl-2-(phenyl-
2
2
2
2
sulfonyl)oxaziridine, CH Cl –MeOH.
2
2
Analysis of this material by LC-MS showed it contained
trace amounts of two impurities. The more polar (0.45%) had
the same retention time as the mixture of chloro bis-N-oxides
1
7 derived from the mixture of amines 16. The less polar
(
0.33%) was the 4-amino derivative 19, authenticated by
independent synthesis from 8 (Scheme 5b). Sequential fluorine
displacement with ammonia and N,N-dimethylethylenediamine
gave the 1-amino analogue 18, which was oxidised to give 19.
The precursor amine 18 was not observed in the samples of
AQ4 2, and mono-N-oxide 19 is suggested to arise from 1,
which is unstable under some conditions. A pure sample of 1
was prepared by collecting the major peak from HPLC, but
when this was re-injected, it was found to contain 1% of 19 (and
no 17). When the oxidation of 2 to give 1 was carried out for
longer times, larger amounts of 19 were seen.
Scheme 4 Synthesis of AQ4N 1. Reagents: i, H N(CH ) NMe ,
2
2
2
2
pyridine; ii, 3-phenyl-2-(phenylsulfonyl)oxaziridine, CH Cl –MeOH.
2
2
obtained was contaminated with a trace of a chloro diamine
analogue, presumably derived from 3,4,6-trichlorophthalic
anhydride (15) originally present in 12.
Reaction of authentic 15 (ref. 13) with hydroquinone as
above, and reaction of the crude product with N,N-diethylene-
diamine, gave a mixture of three isomers 16, barely resolved by
HPLC (Scheme 5a). The fact that three isomers were generated
suggests that the additional chlorine group activates the halo-
gens so that any two can be displaced by the amine. The isomer
mixture had the same retention time as the contaminant in
AQ4 2, but the exact composition of the latter could not be
determined. Oxidation of 2 with 3-phenyl-2-(phenylsulfonyl)-
oxaziridine in dichloromethane–methanol gave AQ4N 1, which
was converted to the dihydrochloride salt and recrystallised
from aq. ethanol.
The cytotoxicities of AQ4N 1, AQ4 2 and the trace impurity
17 (together with its amine precursor 16) were measured
4
in P388 cells (Table 1). As has been shown previously,
N-oxidation of 2 to give 1 results in very considerable loss
of cytotoxicity (6.6 to 330 nM in this cell line). The chloro
analogues 16 and 17, where the side chains may not be in the
preferred 1,4-arrangement, were even less cytotoxic.
In summary, the six-step synthesis 10 → 11 → 12 →
9 → 8 → 2 → 1 (Schemes 2–4) is a viable route for
large-scale preparation of high-purity 1 (AQ4N). It provided 1
in an overall yield of ≈20% from a cheap and available starting
material, and required only one straightforward filtration
2
756
J. Chem. Soc., Perkin Trans. 1, 1999, 2755–2758

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chromatography step near the end of the synthesis (to remove a
layer of 12 (100 g, 0.47 mol) over a layer of powdered mixed
small amount of the monochloro compound 14 from 2).
anhydrous KF (400 g) and NaF (80 g). This packing was not
disturbed, but dried in a vacuum oven at 130–140 ЊC at 20
mmHg for 7 h. The flask was transferred to an oil-bath such
that the oil level was about 1 cm above the solid layer. The flask
was evacuated again by a water-pump, and then filled with
nitrogen gas. The bath was then heated to 260–270 ЊC and held
at this temperature. After about 20 min, a considerable amount
of solid sublimed onto the top of the reaction flask, and the
flask was lowered gently into the oil-bath until the oil level
reached to the neck of the flask. When all the sublimed solid
melted and flowed back onto the solid layer, the flask was
returned to its original level in the oil-bath. This operation was
repeated at about 20 min intervals, until a light brown layer
of KF was observed (after 1.75–3 h). The reaction mix-
ture was then sublimed at 140–170 ЊC/0.3 mmHg in a Kugel-
rohr apparatus, giving a solid product that contained mainly
3,6-difluorophthalic anhydride 9 (≈90% by NMR) (65 g,
Experimental
Analyses were carried out in the Microchemical Laboratory,
University of Otago, Dunedin, NZ. Mps were determined on
an Electrothermal 2300 melting point apparatus and are uncor-
rected. NMR spectra were obtained on a Bruker DRX-400
spectrometer, and are referenced to Me Si. Thin-layer chrom-
4
atography was carried out on aluminium-backed silica gel
(
Merck 60 F254) or alumina plates. Column chromatography
was carried out on Merck silica gel (230–400 mesh). Petroleum
ether refers to the fraction boiling at 40–60 ЊC. Mass spectra
were determined using a VG 7070 spectrometer at nominal 5000
resolution. Purity of the final products AQ4 and AQ4N was
analysed by reversed-phase HPLC, with UV detection at 254
nm.
16
1
7
7%), mp 211–214 ЊC (from toluene) (lit., 212 ЊC). H NMR
spectrum identical with that of an authentic sample (Aldrich
Chemical).
The only significant impurity (≈5–10%) present in the sub-
limed product is considered to be the intermediate 3-chloro-6-
fluorophthalic anhydride 13. However, the above material was
used for the next step without further purification.
3
,4,6-Trichlorophthalic acid 11
This compound was prepared by modifications to a literature
method. A mixture of 3,4,5,6-tetrachlorophthalic anhydride
1
2
13
0 (Aldrich Chemicals) (200 g, 0.70 mol) and NaOH (100 g,
.50 mol) in water (2000 mL) was stirred at 50–60 ЊC (bath)
for 45 min under a nitrogen atmosphere. Zinc dust (140 g, 2.14
mol) was then added portionwise over a period of 10 min,
and the mixture was stirred at 70–80 ЊC for a further 6 h. The
reaction mixture was cooled to room temperature and filtered
through a bed of Celite, and the filter and residue were washed
1
,4-Difluoro-5,8-dihydroxyanthracene-9,10-dione 8
This compound was prepared by modifications to the liter-
10
ature method. A mixture of 9 (100 g, 0.55 mol), hydroquinone
63.7 g, 0.58 mol), NaCl (1270 g, 2.22 mol) and powdered
(
successively with 0.1 M NaOH (2 × 100 mL) and H O (2 × 100
2
anhydrous AlCl (830 g, 6.26 mol) was placed in a 5 L flask
mL). The combined filtrate was acidified with conc. HCl to
pH ≤ 1, and the colourless precipitate was collected by filtration
and washed with 0.1 M HCl (3 × 100 mL). The damp solid was
stirred with EtOAc (1200 mL) and acidified with conc. HCl
until all the solids had dissolved. The EtOAc layer was separ-
ated and the aqueous portion further extracted with the same
solvent (2 × 200 mL). The combined EtOAc solution was dried
3
equipped with a condenser. The reactants were well mixed by
shaking, then heated over a period of 1–2 h to 200 ± 5 ЊC (bath)
under a nitrogen atmosphere (there was very large gas evolution
during the heating process). After a further 2 h at 200 ± 5 ЊC,
the melt was poured onto ice, and conc. HCl (1600 mL) was
added. The mixture was stirred at room temperature over-
night and the reddish brown precipitate was collected, washed
with H O and dried to give crude 1,4-difluoro-5,8-dihydroxy-
anthracene-9,10-dione 8 (151 g, 98%), mp 301–304 ЊC (lit.,
318–319 ЊC). This crude product was virtually insoluble in all
solvents, and showed (by TLC in EtOAc–petroleum ether 1:3)
only one minor impurity (probably 1-chloro-4-fluoro-5,8-
dihydroxyanthracene-9,10-dione). The bulk material was used
for the next step without further purification.
(
Na SO ), filtered, and evaporated under reduced pressure to
2 4
give 3,4,6-trichlorophthalic acid 11 (189 g, 100%) as a colour-
2
10
13
less solid, mp (without recrystallisation) 150 ЊC (lit., 150–
1
1
53 ЊC); H NMR [(CD ) SO] δ 7.90 (s).
3 2
3
,6-Dichlorophthalic anhydride 12
This compound was prepared by modifications to the method
of ref. 14. Zinc dust (165 g, 2.52 mol) was added portionwise
(
over a period of 15 min) to a homogenous mixture of 11 (118
g, 0.437 mol) and NaOH (120 g) in water (1200 mL) stirred at
0 ЊC (bath) under a nitrogen atmosphere. The resulting hetero-
1,4-Bis{[2-(dimethylamino)ethyl]amino}-5,8-dihydroxy-
anthracene-9,10-dione 2 (AQ4)
9
9
This was prepared by modifications to the literature method.
geneous mixture was further stirred at 95–100 ЊC for 5 h, then
cooled to room temperature and filtered through a bed of
Celite. The filter and residue were washed with water (3 × 100
mL), and the combined filtrate was acidified with conc. HCl
A mixture of crude 8 (100 g, 0.36 mol) and N,N-dimethyl-
ethylenediamine (199 mL, 1.81 mol) in pyridine (1500 mL) was
stirred at room temperature under a nitrogen atmosphere for
5
8 h. The mixture was then poured into brine (3000 mL) and
(
250 mL) and extracted with EtOAc (2 × 300 mL). The com-
stirred at 0 ЊC for 2 h. The blue precipitate was collected by
bined EtOAc solution was dried (Na SO ), filtered and evapor-
2
4
filtration, washed with 1 M NH OH (5000 mL), and dried
4
ated under reduced pressure to give crude 3,6-dichlorophthalic
acid (100 g). Toluene (1000 mL) was added to this solid, and the
mixture was distilled until the distillate was clear (after about
under vacuum over KOH–silica for 15 h. This crude product
(
86.8 g) was dissolved in CH Cl and transferred to a short
2 2
silica gel filtration column. Elution with CH Cl –MeOH (99:1)
2
2
6
00 mL had been collected). The hot concentrate was gravity-
gave a pink impurity, mainly 1-chloro-4-{[2-(dimethylamino)-
ethyl]amino}anthracene-9,10-dione 14 (13.8 g, 10%), which was
filtered, and the residue was washed with hot toluene (3 × 50
mL). The combined filtrate was seeded and chilled to give 3,6-
dichlorophthalic anhydride 12 as a colourless solid (67.0 g,
1
purified by recrystallisation from CH Cl , mp 165–167 ЊC; H
2
2
14
1
NMR (CDCl
3
) δ 12.97 (s, 1 H, exchangeable with D O, OH),
2
7
2%), mp 187–190 ЊC (lit., 188–191 ЊC); H NMR [(CD ) SO]
3 2
1
2.92 (s, 1 H, exchangeable with D O, OH), 10.04 (s, 1 H,
2
δ 8.03 (s).
exchangeable with D O, NH), 7.50 (d, J 9.5 Hz, 1 H, H-3), 7.24
2
(
d, J 9.2 Hz, 1 H, H-6), 7.20 (d, J 9.2 Hz, 1 H, H-7), 6.98 (d,
3
,6-Difluorophthalic anhydride 9
J 9.5 Hz, 1 H, H-2), 3.40 (q, J 6.3 Hz, collapse to t after D O,
2
This compound was prepared as reported previously without
details, but well defined conditions and operating procedures
were developed. In a 1 L round-bottomed flask was placed a
2 H, NHCH ), 2.67 (t, J 6.3 Hz, 2 H, NHCH CH ), 2.35 (s, 6 H,
2
2
2
16
NCH ) (Found: C, 58.5; H, 4.7; N, 7.5. Calc. for C H -
3
18 17
ClN O ؒ½H O: C, 58.5; H, 4.9, N, 7.6%).
2
4
2
J. Chem. Soc., Perkin Trans. 1, 1999, 2755–2758
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Elution of the column with CH Cl –MeOH–Et N (90:10:1)
2.56 (t, J 6.1 Hz, 2 H, NHCH CH ), 2.24 [s, 6 H, N(CH ) ]
2 2 3 2
2
2
3
gave 1,4-bis{[2-(dimethylamino)ethyl]amino}-5,8-dihydroxy-
anthracene-9,10-dione 2 (63 g, 42%), 97% pure by HPLC; mp
(Found: C, 62.9; H, 5.2; N, 12.2. Calc. for C H N O : C, 63.3;
H, 5.6; N, 12.2%).
18 19 3 4
10
1
2
40–242 ЊC (without recrystallisation) (lit., 236–238 ЊC); H
NMR [(CD ) SO] δ 13.53 (s, 2 H, exchangeable with D O, OH),
1-Amino-4-{[2-(dimethylamino)ethyl]amino}-5,8-dihydroxy-
anthracene-9,10-dione N-oxide 19
3
2
2
1
0.42 (t, J 4.8 Hz, 2 H, exchangeable with D O, NH), 7.22 (s,
2
2
H, H-6, -7), 7.12 (s, 2 H, H-2, -3), 3.50 (br q, collapsed to t
A solution of 18 in CH Cl –MeOH (5:1; 12 mL) was treated
with a solution of 3-phenyl-2-(phenylsulfonyl)oxaziridine (0.19
2
2
after D O, J 6.5 Hz, 4 H, NHCH CH ), 2.67 (t, J 6.5 Hz, 4 H,
CHCH CH ), 2.35 (s, 12 H, CH ).
2
2
2
2
2
3
g, 0.55 mmol) in CH Cl (6 mL) at 0 ЊC for 1 h. The mixture was
2
2
then treated with anhydrous HCl and diluted with EtOAc, to
1
,4-Bis{[2-(dimethylamino)ethyl]amino}-5,8-dihydroxy-
anthracene-9,10-dione bis-N-oxide dihydrochloride 1
AQ4N.diHCl)
give a precipitate of 19 as the hydrochloride salt (80 mg, 37%),
1
mp 225 ЊC (decomp.); H NMR [(CD ) SO] δ 13.63 and 13.52
3
2
(
(
2 s, 2 H, exchangeable with D O, OH), 12.59 (s, 1 H, exchange-
2
A stirred solution of 2 (63.1 g, 0.15 mol) in CH Cl –MeOH
able with D O, HCl), 10.60 (t, J 5.5 Hz, 1 H, NH), 7.56 (d, J 9.8
2
2
2
(
3:1; 1600 mL) was treated dropwise over a period of 1 h with a
Hz, 1 H, H-6), 7.42 (d, J 9.8 Hz, 1 H, H-7), 7.20 (s, 2 H, H-2,
-3), 4.07 (q, J 5.5 Hz, collapse to t with D O, 2 H, NHCH ),
17
solution of 3-phenyl-2-(phenylsulfonyl)oxaziridine (84 g, 0.32
mol) in CH Cl (500 mL). After this addition, the mixture was
2
2
3.95 (t, J 5.5 Hz, 2 H, NHCH CH ), 3.54 [s, 6 H, N(CH ) ]
2
2
2
2
3 2
stirred at 0 ЊC in the dark for a further 60 min. Anhydrous HCl
gas was then passed through the solution at 0 ЊC until the pH
was ≈1. The mixture was then diluted with EtOAc (2000 mL)
and kept at 0 ЊC for a further 30 min. The resulting blue precipi-
tate was collected by filtration, washed with EtOAc–MeOH
(Found: C, 50.3; H, 4.8. Calc. for C H Cl N O : C, 50.2; H,
18 21 2 3 5
4.9%). The compound was only 76% pure by HPLC, but all
attempts to purify it futher by recrystallisation led to a lower
purity product. It co-eluted on HPLC with the less polar
minor impurity found in 1.
(
1:1; 4 × 100 mL), and dried under vacuum over silica gel to
give the crude dihydrochloride salt of 1 (70.6 g, 90%), 97.6%
pure by HPLC. Recrystallisation from EtOH–water (2:1; 600
mL) gave material of mp 243–245 ЊC (decomp.) (66 g, 84%), of
purity >99% (HPLC) (Found: C, 50.1; H, 6.1; N, 10.7; Cl, 13.1.
Calc. for C H N O ؒ2HClؒ0.5H O: C, 50.2; H, 5.9; N, 10.6;
Cell-line assay
Murine P388 leukaemia cells were obtained and cultured as
described previously. Growth inhibition assays were per-
formed by culturing cells at 4.5 × 10 cells per well in micro-
culture plates for three days in the presence of drug. Cell growth
18
3
22
28
4
6
2
Cl, 13.5%).
3
19
was determined by [ H]TdR uptake. IC -Values are the aver-
50
ages of at least duplicate determinations.
Synthesis of mixture of chlorodiamines 16
13
Reaction of 3,4,6-trichlorophthalic anhydride 15 with hydro-
quinone as above gave crude 4,5,8-trichloro-1,4-dihydroxy-
anthraquinone-9,10-dione. A mixture of this (1.0 g, 2.91 mmol)
and N,N-dimethylethylenediamine (5 mL) was stirred at 20 ЊC
for 6 days, and worked up as above. Chromatography of the
Acknowledgements
This work was carried out with funding from British Technol-
ogy Group Plc. We thank Professor Laurence Patterson for
helpful advice, Dr Brian Palmer for the LC–MS analysis, and
Professor Bruce Baguley for the IC50 data.
crude product on silica gel, and elution with CH Cl2 and
2
CH Cl –MeOH (20:1 → 10:1), gave a solid (410 mg) that
2
2
was a single spot on TLC, but by HPLC was resolved into three
very closely running peaks, suggested to be a mixture of
chlorodiamines 16 (Found: C, 59.1; H, 5.5. Calc. for C H -
References
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22
27
ClN O : C, 59.1; H, 6.1%).
4
4
Oxidation of the mixture 16 with 3-phenyl-2-(phenylsulfonyl)-
oxaziridine as above gave a mixture of the corresponding bis-N-
oxides 17, which co-eluted with the more polar minor impurity
detected in 1 (Found: C, 43.5; H, 5.1; N, 9.8; Cl, 20.8. Calc.
for C H ClN O ؒ2HClؒ0.5H O: C, 43.6; H, 5.6; N, 9.2; Cl,
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-Amino-4-{[2-(dimethylamino)ethyl]amino}-5,8-dihydroxy-
anthracene-9,10-dione 18
1
024.
Anhydrous NH gas was bubbled for 5 min through a solution
3
8
9
P. Chang and C. C. Cheng, Synth. Commun., 1995, 25, 1893.
A. P. Krapcho, Z. Getahun, K. L. Avery, K. J. Vargas and M. P.
Hacker, J. Med. Chem., 1991, 34, 2373.
of 8 (1.0 g, 3.62 mmol) in pyridine (55 mL), and the mixture
was then stirred in a bomb at 50–55 ЊC (bath temperature) for
5
h. The mixture was cooled to 20 ЊC, N,N-dimethylethylene-
10 A. P. Krapcho, Z. Getahun and K. L. Avery, Synth. Commun., 1990,
0, 2139.
2
diamine (4 mL) was added, and the mixture was stirred at 20 ЊC
in the open atmosphere for 90 h. The mixture was poured into a
mixture of brine (150 mL) and conc. NH OH (50 mL) at 0 ЊC,
and kept for 3 h. The resulting blue precipitate was collected,
washed several times with 1 M NH OH, and dried. Chroma-
tography of the crude material on silica gel, and elution with
CH Cl and CH Cl –MeOH (50:1 → 20:1) gave 18 (0.34 g,
1
1
1
1
1 A. P. Krapcho and Z. Getahun, Synth. Commun., 1985, 15, 907.
2 G. Valkanas, J. Chem. Soc., 1963, 5554.
3 N. J. O’Reilly, W. S. Derwin and H. C. Lin, Synlett, 1990, 339.
4 L. R. Caswell and G. Cavasos, J. Heterocycl. Chem., 1995, 32, 907.
4
4
15 L. B. Fertel, N. J. O’Reilly and K. M. Callaghan, J. Org. Chem.,
1993, 58, 261.
1
6 E. D. Bergmann, M. Bentov and A. Levy, J. Chem. Soc., 1964, 1194.
17 F. A. Davis and O. D. Stringer, J. Org. Chem., 1982, 47, 1775.
8 G. J. Finlay, K. M. Holdaway and B. C. Baguley, Oncol. Res., 1994,
, 33.
2
2
2
2
1
5
5%); mp 167–169 ЊC (from EtOAc–MeOH); H NMR [(CD ) -
3 2
1
SO] δ 13.66 and 13.64 (2 s, 2 H, exchangeable with D O, OH),
1
2
6
0.60 (t, J 5.0 Hz, 1 H, exchangeable with D O, NH), 7.47 (d,
2
19 E. S. Marshall, G. J. Finlay. J. H. L. Matthews, J. H. F. Shaw,
J 9.8 Hz, 1 H, H-6), 7.33 (d, J 9.8 Hz, 1 H, H-7), 7.15 (d, J 9.4
Hz, 1 H, H-3), 7.13 (d, J 9.4 Hz, 1 H, H-2), 3.53 (td, J 6.1, 5.0
Hz, 2 H, NHCH ), 3.38 (s, 2 H, exchangeable with D O, NH ),
J. Nixon and B. C. Baguley, J. Natl. Cancer Inst., 1992, 84, 340.
Paper 9/05611D
2
2
2
2
758
J. Chem. Soc., Perkin Trans. 1, 1999, 2755–2758