Synthesis and cytotoxicity of 1,2-disubstituted naphth[2,3-d]imidazole-4,9-diones and related compounds

Article abstract of DOI:10.1021/jm950247k

As part of our continuing search for potential anticancer drug candidates that are selective against slowly growing solid tumors, we have synthesized several series of 1- and 2-substituted derivatives of the lead structure, 1-ethyl-2-methylnaphth[2,3-d]midazole-4,9-dione (5). Their cytotoxic activity in the National Cancer Institute's in vitro cancer cell line panel is reported. In general, substitution of various alkyl, phenyl, or benzyl moieties did not improve activity, and compound 5 remains the most active naphth[2,3-d]imidazole-4,9-dione derivative. However, high levels of activity and selectivity were found with several related 2-(acylamino)-3-chloro1,4-naphthoquinones (2f-j). Compound 2i, 2-[(2-fluorophenyl)acetamido]-3-chloro-1,4-naphthoquinone, has been selected for further in vivo testing and as an additional lead compound for further structural modification.

Full text of DOI:10.1021/jm950247k

J . Med. Chem. 1996, 39, 1447-1451
1447
Syn th esis a n d Cytotoxicity of 1,2-Disu bstitu ted
Na p h th [2,3-d ]im id a zole-4,9-d ion es a n d Rela ted Com p ou n d s
Sheng-Chu Kuo,*,† Toshiro Ibuka,‡ Li-J iau Huang,† J in-Cherng Lien,† Shyue-Ren Yean,† Shung-Chieh Huang,†
Daniel Lednicer,§ Susan Morris-Natschke,‡ and Kuo-Hsiung Lee*,‡
Graduate Institute of Pharmaceutical Chemistry, China Medical College, Taichung 400, Taiwan, Republic of China,
Drug Synthesis and Chemistry Branch, Developmental Therapeutics Program, Division of Cancer Treatment,
National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, and Natural Products Laboratory,
Division of Medicinal Chemistry and Natural Products, School of Pharmacy, University of North Carolina,
Chapel Hill, North Carolina 27599
Received April 3, 1995X
As part of our continuing search for potential anticancer drug candidates that are selective
against slowly growing solid tumors, we have synthesized several series of 1- and 2-substituted
derivatives of the lead structure, 1-ethyl-2-methylnaphth[2,3-d]imidazole-4,9-dione (5). Their
cytotoxic activity in the National Cancer Institute’s in vitro cancer cell line panel is reported.
In general, substitution of various alkyl, phenyl, or benzyl moieties did not improve activity,
and compound 5 remains the most active naphth[2,3-d]imidazole-4,9-dione derivative. However,
high levels of activity and selectivity were found with several related 2-(acylamino)-3-chloro-
1,4-naphthoquinones (2f-j). Compound 2i, 2-[(2-fluorophenyl)acetamido]-3-chloro-1,4-naph-
thoquinone, has been selected for further in vivo testing and as an additional lead compound
for further structural modification.
In tr od u ction
Ch em istr y
Scheme 1 shows two routes to 1-ethyl-2-methyl-
naphth[2,3-d]imidazole-4,9-dione (5) and related com-
pounds; 2-amino-3-chloro-1,4-naphthoquinone (1) was
used as the common starting material. In route A, 1
underwent N-acylation with acetic anhydride in the
presence of H2SO4 to give 2-acetamido-3-chloro-1,4-
naphthoquinone (2a ). Amination of intermediate 2a
with gaseous NH3 gave 2-acetamido-3-amino-1,4-naph-
thoquinone (3a , route A). Cyclization with NaOH or Zn/
AcOH afforded 2-methyl-1H-[2,3-d]imidazole-4,9-dione
(4a ). Reaction of 4a with NaOH and ethyl iodide gave
1-ethyl-2-methylnaphth[2,3-d]imidazole-4,9-dione (5).
The structure of this known compound was confirmed
The quinone moiety is involved in a wide variety of
biochemical processes1 including electron transport and
oxidative phosphorylation. Biological activities that
have been reported for quinones and quinone deriva-
tives include enzyme inhibition2 and antibacterial,3
antifungal,4 and anticancer activities.5,6 Numerous
structurally diverse quinone derivatives have been
synthesized and investigated; one class of such com-
pounds is the heterocyclic quinones, including imidazole
derivatives of 1,4-naphthoquinones.7,8 Naphth[2,3-d]-
imidazole-4,9-dione9 and its 1-â-D-ribofuranosyl deriva-
tive10 were prepared in a study of naphthoquinone
heterocycles and were found to be effective inhibitors
of hypoxanthine phosphoribosyltransferase,10 which is
involved in an initial step in purine nucleotide biosyn-
thesis. In addition, the naphthoquinone psychorubrin
was isolated as a cytotoxic natural product from Psy-
chotria rubra (Chiou Chie Mu) (Rubiaceae) by this
laboratory. Synthetic modification of this compound led
to more cytotoxic derivatives.11
1
by IR, H- and 13C-NMR, MS, and elemental analysis
data.
Compound 5 was also prepared by a literature pro-
cedure (route B). First, 2a was reacted with ethylamine
to give 2-acetamido-3-(ethylamino)-1,4-naphthoquinone
(29), which was then cyclized with NaOH, affording 5.
Route B gives better yields of 1,2-substituted naphth-
[2,3-d]imidazole-4,9-diones and easier workup proce-
dures than does route A. Also, since we wanted to study
the cytotoxicity of the 2-(acylamino)-3-(alkylamino)-1,4-
naphthoquinone intermediates, most of the final com-
pounds were synthesized by route B. Accordingly, the
1-substituted-2-methylnaphth[2,3-d]imidazole-4,9-di-
ones 6-16, 18, and 20-21 were prepared in two steps
from 2a and the appropriate alkylamine through the
corresponding 2-(acylamino)-3-(alkylamino)-1,4-naph-
thoquinones 30-43. Compounds 17, 19, and 20 were
prepared using route A from 4a and the appropriate
alkyl halide.
As an extension of our synthesis of cytotoxic antitu-
mor analogs related to psychorubrin derivatives and as
part of our continuing search for cytotoxic agents that
are selective against slowly growing solid tumors,12
1-ethyl-2-methylnaphth[2,3-d]imidazole-4,9-dione (5) was
synthesized and exhibited potent cytotoxicity against
ovarian cancer cell lines. Therefore, several series of
1- and 2-substituted naphth[2,3-d]imidazole-4,9-dione
derivatives were synthesized and evaluated for cytotoxic
activity. This paper describes both the synthesis and
cytotoxicity of these derivatives in the National Cancer
Institute’s (NCI) in vitro cancer cell line panel.
Evaluation of the cytotoxicity of these 1-substituted-
2-methylnaphth[2,3-d]imidazole-4,9-dione derivatives
(5-21) showed that the N-ethyl analog (5) displays
strong cytotoxicity. Therefore, we prepared a series of
1-ethyl-2-substituted-naphth[2,3-d]imidazole-4,9-di-
ones (22-28) where the N-1 substituent was fixed as
* To whom correspondence should be addressed.
† China Medical College.
‡ School of Pharmacy, University of North Carolina.
§ Drug Synthesis and Chemistry Branch, NCI.
X Abstract published in Advance ACS Abstracts, March 1, 1996.
0022-2623/96/1839-1447$12.00/0 © 1996 American Chemical Society

1448 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 7
Kuo et al.
Sch em e 1
an ethyl group. The 2-alkyl compounds (22-24) were
readily prepared in two steps from 2b-d as shown
above in route B. However, the 2-(benzoylamino)-3-
chloro-1,4-naphthoquinone intermediates (2e-h ) needed
for the synthesis of the 2-aryl derivatives (25-28) could
not be prepared under the strongly acidic conditions
used in the synthesis of 2a -d . (The failure of benzoyl
chloride and 1 to react under these conditions has been
previously reported by Hoover.3) Increasing the heating
time also failed to give any 2-benzoylamino intermediate
(2e). We then tried strongly basic conditions; compound
1 was treated first with an equimolar ratio of NaH and
then with benzoyl chloride. Under these conditions,
N-acylation occurred readily, giving an 80% yield of

Disubstituted Naphth[2,3-d]imidazole-4,9-diones
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 7 1449
Ta ble 1. Inhibition of in Vitro Cancer Cell Lines by
Compounds 2i, 5, and 50
2-(benzoylamino)-3-chloro-1,4-naphthoquinone (2e). The
substituted benzoyl compounds (2f-h ) could also be
prepared using the same reaction conditions. Reaction
of these 2-benzoylamino intermediates with the ap-
propriate reagents then proceeded normally to give the
expected products 25-28 using route B.
Naphth[2,3-d]imidazole-4,9-diones 4b and 4c, which
contain fluorinated benzyl groups at the C-2 position
and hydrogen at the N-1 position, were prepared from
intermediates 2i and 2j using route A. Compounds 51-
62, which contain a terminal carboxylic acid or ester
functionality in the acylamino or C-2 substitution, were
prepared from intermediates 2k and 2l using route B.
Reaction of compounds 4b and 4c with an equimolar
ratio of both NaH and ethyl iodide resulted in ethylation
at N-1 giving compounds 63 and 66, respectively. The
use of 2 molar equiv of NaH and excess ethyl iodide
resulted in compounds 64 and 65, which contain a
second ethyl group at the benzyl carbon as confirmed
by mass spectral and NMR analysis.
cytotoxicity log GI50 (M)a,b
cell line
ovarian
IGROV1
OVCAR-3
non small cell lung
HOP-92
HCI-H522
CNS
2i
5
50
-6.17
-6.03
-5.69
-7.30
-5.81
-6.28
-5.96
-6.67
-5.79
-6.62
-5.95
-6.43
SF-539
U-251
-6.62
-6.48
-5.57
-5.72
-5.72
-6.28
melanoma
MALME-3M
UACC-62
colon
-5.77
-6.48
-5.60
-5.31
-6.11
-6.45
COLO-205
HCT-116
leukemia
HL-60(TB)
K-562
prostate
PC-3
DU-145
-5.72
-6.37
-6.45
-5.91
-5.46
-6.38
-6.55
-6.53
-4.78
-5.78
-6.39
-6.31
NT
NT
NT
NT
-6.42
-5.57
Resu lts a n d Discu ssion
small cell lung
DMS 114
DMS 273
breast
-6.76
-5.89
-6.56
-5.78
NT
NT
The lead compound, 1-ethyl-2-methylnaphth[2,3-d]-
imidazole-4,9-dione (5), was assayed for in vitro cyto-
toxicity against KB cell growth (at the University of
North Carolina) and showed good activity with an ED50
value of <0.4 µg/mL. This compound was then submit-
ted to NCI for testing against a panel of 53 tumor cell
lines including leukemia, non small cell and small cell
lung, colon, central nervous system (CNS), ovarian, and
renal cancers and melanoma. The assay results are
reported both as dose-response curves and pictographi-
cally as “mean graphs”. Compound 5 showed good
activity and high selectivity in four ovarian cancer cell
lines (log GI50 values ranging from -6.1 to -7.3 in
OVCAR-3, -4, -5, and -8 cell lines, GI50 ) compound
concentration that inhibits 50% cell growth). Selectivity
was also found in the small cell lung cancer cell line
DMS-114 (log GI50 ) -6.56). Compound 5 has been
selected by NCI for testing in an in vivo tumor xenograft
model.
On the basis of this promising activity, several series
of 1- and 2-substituted naphth[2,3-d]imidazole-4,9-dione
derivatives were synthesized and evaluated for cytotoxic
activity. log GI50 values were determined for all final
products and their parent 2-(acylamino)-3-chloro and
2-(acylamino)-3-amino compounds in ovarian cancer,
non small cell lung cancer, CNS cancer, melanoma,
colon cancer, leukemia, prostate cancer, small cell lung
cancer, breast cancer, and renal cancer cell lines.
Compounds were considered active only if their log GI50
values were less than -4. Certain cell lines including
OVCAR-3 ovarian cancer, NCI-H522 non small cell lung
cancer, several melanomas, HCT-116 colon cancer, and
HL-60 leukemia showed significant sensitivity to these
compound classes. Experimental data for selected
compounds from each compound class in representative
cell lines are shown in Table 1.
MCF-7
MDA-N
NT
NT
-6.17
NT
-6.43
-6.92
renal
ACHN
RXF-393
-6.32
-6.78
NT
-4.56
-6.01
-6.49
c
mean value
-6.08
-5.63
-5.80
a
Data obtained from NCI’s in vitro disease-oriented tumor cells
screen (see refs 17 and 18 for details). NT ) not tested. c Mean
value over all cell lines tested.
b
cell lines), compounds 6-14 showed decreased activities
with log GI50 values generally in the range of -4 to -5
in ovarian, non small cell lung, CNS, colon, and small
cell lung cancer cells. Activities for 6-14 were similar
for melanoma and leukemia cancer cells; however, in
these lines, 5 did not show activity in the range of <-4.
Compounds 15, 16, and 21 contain N-1 ethyl groups
substituted at the â position with polar moieties (di-
methylamino, hydroxy, or chloro, respectively). The
activities of these compounds are on the same order as
compounds 6-14. Four N-1 parasubstituted benzyl
compounds (17, p-methylbenzyl; 18, p-methoxybenzyl;
19, p-fluorobenzyl; 20, p-chlorobenzyl) showed slightly
higher activity (log GI50 values of -5 to -6) in non small
cell lung, CNS, colon, leukemia, small cell lung, and
renal cancer and melanoma cell lines.
Naphth[2,3-d]imidazole-4,9-dione derivatives that con-
tain a fixed N-1 ethyl substituent and different C-2
substituents were also synthesized. Compounds with
ethyl (23), propyl (24), phenyl (25), p-fluorophenyl (26),
p-methoxyphenyl (27), and 3,5-dimethoxyphenyl (28)
groups were, in general, less active (log GI50 values
around -5) or inactive in the cell line panel. Compound
22, which contains a chloromethyl group at C-2 and a
N-1 ethyl group, was more cytotoxic with log GI50 values
ranging from -6 to -6.8.
The 2-(acylamino)-3-(alkylamino)-1,4-naphthoquinone
intermediates (29-50) prepared by synthetic route B
were also tested for their cytotoxic activity. In this
series, compound 50 with a dimethoxybenzoyl group
showed significant activity in all cancer cell lines (log
The 1,2 substituted naphth[2,3-d]imidazole-4,9-dione
derivatives contained various alkyl, benzyl, or phenyl
groups at the C-2 or N-1 positions. When the C-2
substituent was fixed as a methyl group, larger and
more branched alkyl groups were inserted at the N-1
position. When compared with compound 5 (which
showed log GI50 values in the range of -6 to -7 in most

1450 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 7
Kuo et al.
temperature for 20 min and then filtered. The precipitate was
washed with Et2O and recrystallized from EtOH, giving golden
needle crystals (mp 219-220 °C) of 2a in a 98% yield: 1H NMR
(CDCl3) δ 2.31 (s, 3H, COCH3), 7.71 (br, 1H, NH), 7.73-7.82
(m, 2H, H-6,7), 8.10-8.13 (m, 2H, H-5), 8.18-8.20 (m, 2H,
H-8); MS m/z 249.5 (M+).
GI50 values less than -6) tested except for small cell
lung cancer cells.
Biological evaluation of the starting 2-(acylamino)-3-
chloro-1,4-naphthoquinones resulted in the discovery of
additional promising compounds. While the 2-benzo-
ylamino compound, 2e, showed low activity in the
cancer cell line panel (log GI50 values ranging from -4
to -5), addition of a p-fluoro (2f) or a p-methoxy (2g)
group increased activity (log GI50 values generally
around -6) in most cell lines. The 3,5-dimethoxy-
substituted compound, 2h , showed similar activity.
Compounds 2i and 2j contain phenylacetamido groups
fluorinated at the ortho and para positions, respectively.
Both of these compounds showed high activity in many
cell lines with log GI50 values ranging from -5.6 to -7.6.
Replacement of the 3-chloro group of 2i and 2j with
an NH2 group following synthetic pathway A gave
compounds 3b and 3c; cyclization then gave the tricyclic
imidazole compounds 4b and 4c. These compounds
showed greatly reduced cytotoxicity (3b and 3c were
inactive in all cell lines and 4b and 4c had no log GI50
values less than -5.3) compared with the parent chloro
compounds.
In general, compounds 51-62, which contain terminal
carboxylic groups, showed cytotoxicity similar to that
of the naphth[2,3-d]imidazole-4,9-diones without these
polar functionalities.
Compounds 63 and 66, which contain fluorinated
benzyl groups at the C-2 position, and compounds 64
and 65, which are ethylated at the benzyl carbon,
showed activity profiles similar to those of the other
naphth[2,3-d]imidazole-4,9-diones.
In summary, the promising activity of the lead
compound, 5, in the NCI in vitro cancer panel prompted
synthesis of 33 1,2-disubstituted naphth[2,3-d]imida-
zole-4,9-diones and 45 related compounds. One 2-(ac-
ylamino)-3-(alkylamino)-1,4-naphthoquinone, 50, showed
activity and selectivity, and high levels of activity were
found with several 2-(acylamino)-3-chloro-1,4-naphtho-
quinones, 2f-j. Compound 2i, 2-[(2-fluorophenyl)ac-
etamido]-3-chloro-1,4-naphthoquinone, has been se-
lected for further in vivo testing. Compound 5 with an
ethyl group at N-1 and a methyl group at C-2 remains
the most active naphth[2,3-d]imidazole-4,9-dione de-
rivative. Substitution of other alkyl groups or phenyl
or benzyl moieties did not improve activity. Further
work will be done to optimize the lead structures found
in this data set.
Compounds 2c and 2d were also prepared by this method
from 1 and the appropriate acid anhydride.
2-(Ch lor oacetam ido)-3-ch lor o-1,3-n aph th oqu in on e (2b).
To a suspension of 2-amino-3-chloro-1,4-naphthoquinone (1)
(10.4 g, 0.05 mol) in anhydrous xylene (100 mL) were added
50 mL of chloroacetyl chloride and dry HCl. After a 40 min
reflux, the reaction mixture cooled to room temperature for 6
h. An equal amount of Et2O was added, and the solution sat
for 1 day. The solution was then filtered, and the precipitate
was recrystallized from benzene to give 2b as light yellow
needle crystals (mp 167-169 °C) in an 85% yield: 1H NMR
(CDCl3) δ 4.24 (s, 2H, COCH2Cl), 7.24-7.78 (m, 2H, H-6,7),
8.09-8.12 (m, 1H, H-5), 8.13-8.18 (m, 1H, H-8); MS m/z 284
(M+).
Compounds 2k and 2l were also prepared by this method
from 1 and the appropriate acid chloride.
2-(Ben zoyla m in o)-3-ch lor o-1,4-n a p h t h oq u in on e (2e).
To a solution of 2-amino-3-chloro-1,4-naphthoquinone (1) (1.0
g, 4.8 mmol) in THF (50 mL) was added 0.2 g NaH at room
temperature, and the reaction mixture was stirred for 30 min.
Then, 1 g of benzoyl chloride was added and stirring continued
for 5 min. The reaction mixture was then poured into ice
water, extracted with CHCl3, and evaporated. The residue was
chromatographed on silica gel with benzene as eluent to give
2e (mp 254-256 °C) in an 80% yield: 1H NMR (CDCl3) δ 7.25-
7.45 (m, 5H, aromatic protons), 7.71-7.83 (m, 2H, H-6,7),
8.02-8.20 (m, 2H, H-5,8); MS m/z 311.5 (M+).
Compounds 2f-h were prepared in an analogous manner
from 1 and the appropriate acid chlorides.
2-[(2-F lu or op h en yl)a ceta m id o]-3-ch lor o-1,4-n a p h th o-
qu in on e (2i). This compound was prepared by modification
of the procedure of Hoover and Day.3 To a stirred mixture of
2-amino-3-chloro-1,4-naphthoquinone (1) (16.6 g, 0.080 mol)
and 2-fluorophenylacetyl chloride (17.2 g, 0.1 mol) was added
3 mL of BF3‚Et2O, and the mixture was heated under reflux
for 24 h. The mixture was then concentrated under reduced
pressure to give a semisolid. Acetone (50 mL) was added, and
stirring was continued for 20 min under reflux. After cooling,
the precipitate was collected by filtration and washed with
acetone. Recrystallization from DMF:acetone (1:1) gave 18 g
(66% yield) of 2i as yellow crystals (mp 232 °C): 1H NMR
(CDCl3) δ 3.88 (s, 2H, COCH2), 7.17 (t, 2H, H-3′,5′), 7.29-7.36
(m, 1H, H-4′), 7.40-7.46 (m, 1H, H-6′), 7.86-7.92 (m, 2H,
H-6,7), 8.01-8.10 (m, 2H, H-5,8); MS m/z 343 (M+).
Compound 2j was synthesized using the same method.
2-Aceta m id o-3-a m in o-1,4-n a p h th oqu in on e (3a ). Com-
pound 2a (8.5 g, 0.34 mol) was dissolved in anhydrous
nitrobenzene (300 mL), dry NH3 gas was added, and the
reaction mixture was heated at reflux for 1 h. After cooling,
the precipitate was filtered and recrystallized from EtOH to
give dark red needle crystals (mp 233-234 °C) of 3a in a yield
of 92%: 1H NMR (CDCl3) δ 2.04 (s, 3H, COCH3), 6.78 (br s,
2H, NH2), 7.69-7.84 (m, 2H, H-6,7), 7.93-7.99 (m, 2H, H-5,8),
9.58 (br s, 1H, NHCO); MS m/z 230 (M+).
Exp er im en ta l Section
All melting points are uncorrected. IR spectra were re-
corded on a Shimadzu IR-440 spectrometer as KBr pellets.
NMR spectra were obtained on J EOL FX-90Q and Varian
VXR-300 FT NMR spectrometers in CDCl3 (or DMSO-d6 when
so noted in Tables 1-3 in the Supporting Information) with
tetramethylsilane (TMS) as an internal standard. The fol-
lowing abbreviations are used: s ) singlet, d ) doublet, t )
triplet, q ) quartet, m ) multiplet, and br ) broad. Mass
spectra (MS) were measured with an HP 5995 GC-MS instru-
ment. The UV spectra were recorded on a Shimadzu UV-160A
UV-visible recording spectrophotometer in EtOH. Elemental
analyses were performed by National Cheng Kung University
and National Chung Hsing University, Taiwan. Results
obtained were within (0.4% of the theoretical value.
Compounds 3b and 3c were prepared in an analogous
manner from 2i and 2j, respectively.
2-Met h yl-1H -n a p h t h [2,3-d ]im id a zole-4,9-d ion e (4a ).
Meth od 1. To a solution of 3a (4.0 g, 0.017 mol) in EtOH (50
mL) was added 2 N NaOH (20 mL). The reaction mixture was
heated to reflux for 24 h, then cooled, and filtered. The
precipitate was recrystallized from EtOH to give 4a as a dark
brown powder (mp 360-370 °C) in a 98% yield: 1H NMR
(CDCl3) δ 2.28 (s, 3H, CH3), 7.61-7.64 (m, 2H, H-6,7), 7.89-
7.93 (m, 2H, H-5,8); MS m/z 212 (M+).
Compounds 4b and 4c were synthesized in the same
manner from 3b and 3c.
2-Aceta m id o-3-ch lor o-1,4-n a p h th oqu in on e (2a ). To a
suspension of 2-amino-3-chloro-1,4-naphthoquinone (1) (52 g,
0.25 mol) in acetic anhydride (75 mL) was added 5 drops of
concentrated H2SO4. The reaction mixture was stirred at room
Meth od 2. A solution of 3a (2.0 g, 0.0009 mol) and Zn (1.0
g) in glacial HOAc (50 mL) was refluxed for 24 h. A small
amount of active charcoal was added, and the solution was
filtered. The filtrate was poured into a 4-fold excess of H2O,

Disubstituted Naphth[2,3-d]imidazole-4,9-diones
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 7 1451
the pH was adjusted to 8 with NaHCO3 solution, and the
solution was filtered. The precipitate was recrystallized from
EtOH to give a dark brown powder (4a ).
By a procedure identical with that described for the syn-
thesis of 63, 4c was converted to 66. Compounds 64 and 65
were prepared in a similar manner from 4b and 4c, respec-
tively, but using 2 molar equiv of NaH and excess EtI.
1-Eth yl-2-m eth yln a p h th [2,3-d ]im id a zole-4,9-d ion e (5).
Meth od 1 (Rou te A). A solution of 4a (2.0 g, 9.4 mmol) in a
small amount of DMF was heated to 40-50 °C; 1.0 g of NaOH
was added, and the heating was continued until the NaOH
had dissolved. After cooling to room temperature, an equimo-
lar amount of EtI was added, and stirring was continued for
1 h. The reaction mixture was then poured into ice water,
filtered, and purified with column chromatography (CHCl3,
silica gel). Recrystallization of the product (5) from EtOH gave
yellow crystals (mp 185-186 °C, 66% yield): 1H NMR (CDCl3)
δ 1.45 (t, 3H, CH2CH3), 2.58 (s, 3H, CH3), 4.44 (q, 2H, CH2),
7.69-7.72 (m, 2H, H-6,7), 8.07-8.09 (m, 1H, H-5), 8.17-8.20
(m, 1H, H-8); MS m/z 240 (M+).
Ack n ow led gm en t. This work was supported by
grants from the National Science Council of the Republic
of China (S.C.K.) and the U.S. National Cancer Institute
CA 17625 (K.H.L.).
Su p p or tin g In for m a tion Ava ila ble: Yields and complete
physical and spectral data for compounds 2-66 and data
tables (log GI50 values) from the NCI screen for compounds
2-66 (25 pages). Ordering information is given on any current
masthead page.
Compounds 17, 19, and 20 were also prepared from 4a using
an analogous procedure.
Refer en ces
Meth od 2 (Rou te B). To a solution of 29 (4.0 g, 0.017 mol,
synthesis given below) in EtOH (50 mL) was added 2 N NaOH.
The reaction mixture was heated to reflux for 30 min, then
cooled, and filtered. The precipitate was washed with H2O,
dried, and recrystallized from EtOH:CHCl3 to afford the same
product (5) as obtained in method 1 in a 75% yield.
Compounds 6-16, 18, and 20 were prepared similarly in
two steps from 2a and the appropriate alkylamine through
intermediates 30-42. Compounds 57-62 were also prepared
similarly from 51-56.
1-(2′-Ch lor oeth yl)-2-m eth yln a p h th [2,3-d ]im id a zole-4,9-
d ion e (21). A solution of 43 (5 g, 0.02 mol, prepared from 2a
and 2-chloroethylamine in an analogous manner to that of 29
given below) in formic acid (50 mL) was refluxed for 1 h and
then concentrated. Purification by column chromatography
(CHCl3, silica gel) followed by recrystallization from benzene
gave 21 as yellow crystals (mp 200-202 °C, 67% yield): 1H
NMR (CDCl3) δ 2.64 (s, 3H, CH3), 3.95 (t, 2H, CH2Cl), 4.66 (t,
2H, NCH2), 7.68-7.72 (m, 2H, H-6,7), 8.06-8.09 (m, 1H, H-5),
8.18-8.22 (m, 1H, H-8); MS m/z 274 (M+).
Compounds 22-28 were synthesized by the same method
from 2b-h and ethylamine through intermediates 44-50.
2-Aceta m id o-3-(eth yla m in o)-1,4-n a p h th oqu in on e (29).
To a suspension of 2a (5.0 g, 0.02 mol) in toluene (100 mL)
was added an excess of ethylamine. The reaction mixture was
stirred for 30 min at room temperature and then filtered. The
precipitate was recrystallized from EtOH giving dark red
crystals of 29 (mp 198-200 °C, 88% yield): 1H NMR (CDCl3)
δ 1.27 (t, 3H, CH2CH3), 2.24 (s, 3H, COCH3), 3.46 (q, 2H, CH2),
7.58-7.72 (m, 2H, H-6,7), 8.02-8.08 (m, 2H, H-5,8); MS m/z
258 (M+).
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Compounds 30-43 were prepared from 2a and the ap-
propriate amine using the same method. Compounds 44-56
were prepared in an analogous manner from 2b-h , 2k , and
2l.
1-Eth yl-2-[(2′-flu or op h en yl)m eth yl]n a p h th [2,3-d ]im id -
a zole-4,9-d ion e (63). To a stirred suspension of 28.8 mg (1.2
mmol) of NaH in 1 mL of DMF was added a solution of 306
mg (1 mmol) of 4b in 3 mL of DMF at 0 °C, and the mixture
was stirred for 15 min. Ethyl iodide (0.3 mL) was added to
the above mixture, and the mixture was stirred for 3 h at room
temperature. Ice-water (2 mL) was added, and the mixture
was extracted with CHCl3. The extract was washed with
water, dried over MgSO4, and concentrated under reduced
pressure to leave a brown oil, which was purified by flash
chromatography over silica gel with n-hexane: EtOAc (4:1) to
yield 240 mg (72%) of the title compound. Recrystallization
from a mixture of CHCl3:Me2CO (1:5) gave yellow crystals: mp
1
176 °C; H NMR (CDCl3) δ 1.29 (t, 3H, CH2CH3), 4.31 (s, 2H,
CH2C6H4F), 4.47 (q, 2H, CH2CH3), 7.18-7.27 (m, 2H, H-3′,5′),
7.34-7.41 (m, 2H, H-4′,6′), 7.81-7.85 (m, 2H, H-6,7), 8.02-
8.07 (m, 2H, H-5,8); MS m/z 334 (M+).
J M950247K