Synthesis and antiviral activity of helioxanthin analogues

Article abstract of DOI:10.1021/jm034265a

A series of natural product analogues based on helioxanthin (2), with particular attention to modification of the lactone ring and methylenedioxy group, were synthesized and evaluated for their antiviral activities. Among them, lactam derivative 18 and helioxanthin cyclic hydrazide 28 exhibited significant in vitro antiviral activity against hepatitis B virus (EC ₅₀ = 0.08 and 0.03 μM, respectively). Compound 18 showed the most potent antiviral activity against hepatitis C virus (55% inhibition at 1.0 μM). Compound 12, an acid-hydrolyzed product of helioxanthin cyclic imide derivative 9, was found to exhibit broad-spectrum antiviral activity against hepatitis B virus (EC₅₀ = 0.8 μM), herpes simplex virus type 1 (EC₅₀ = 0.15 μM) and type 2 (EC₅₀ < 0.1 μM), Epstein-Barr virus (EC₅₀ = 9.0 μM), and cytomegalovirus (EC ₅₀ = 0.45 μM). Helioxanthin lactam derivative 18 also showed marked inhibition of herpes simplex virus type 1 (EC₅₀ = 0.29 μM) and type 2 (EC₅₀ = 0.16 μM). The cyclic hydrazide derivative of helioxanthin 28 and its brominated product 42 exhibited moderately potent activities against human immunodeficiency virus (EC₅₀ = 2.7 and 2.5 μM, respectively). Collectively, these molecules represent a novel set of antiviral compounds with unique structural features.

Full text of DOI:10.1021/jm034265a

534
J. Med. Chem. 2005, 48, 534-546
Synthesis and Antiviral Activity of Helioxanthin Analogues
Hosup Yeo,†,‡,§ Ying Li,†,§ Lei Fu,† Ju-Liang Zhu,† Elizabeth A. Gullen,† Ginger E. Dutschman,† Yashang Lee,†
Raymond Chung,‡ Eng-Shang Huang,| David J. Austin,‡ and Yung-Chi Cheng*,†
Department of Pharmacology, Yale University School of Medicine, and Department of Chemistry, Yale University,
New Haven, Connecticut 06520, and Department of Medicine, University of North Carolina, School of Medicine,
Chapel Hill, North Carolina 27599
Received December 25, 2003
A series of natural product analogues based on helioxanthin (2), with particular attention to
modification of the lactone ring and methylenedioxy group, were synthesized and evaluated
for their antiviral activities. Among them, lactam derivative 18 and helioxanthin cyclic
hydrazide 28 exhibited significant in vitro antiviral activity against hepatitis B virus (EC50
)
0.08 and 0.03 µM, respectively). Compound 18 showed the most potent antiviral activity against
hepatitis C virus (55% inhibition at 1.0 µM). Compound 12, an acid-hydrolyzed product of
helioxanthin cyclic imide derivative 9, was found to exhibit broad-spectrum antiviral activity
against hepatitis B virus (EC50 ) 0.8 µM), herpes simplex virus type 1 (EC50 ) 0.15 µM) and
type 2 (EC50 < 0.1 µM), Epstein-Barr virus (EC50 ) 9.0 µM), and cytomegalovirus (EC50
)
0.45 µM). Helioxanthin lactam derivative 18 also showed marked inhibition of herpes simplex
virus type 1 (EC50 ) 0.29 µM) and type 2 (EC50 ) 0.16 µM). The cyclic hydrazide derivative of
helioxanthin 28 and its brominated product 42 exhibited moderately potent activities against
human immunodeficiency virus (EC50 ) 2.7 and 2.5 µM, respectively). Collectively, these
molecules represent a novel set of antiviral compounds with unique structural features.
Introduction
sive efforts in the search for effective antiviral agents
against drug-resistant HBV, a number of nucleotide
analogues have been developed and are currently under
clinical evaluation for the treatment of 3TC-resistant
HBV infections.16,17
Arylnaphthalene lignan lactones are natural product
molecules found in plant species, many exhibiting
diverse biological activities, such as phosphodiesterase
inhibition,1 leukotriene biosynthesis inhibition,2 hypo-
lipidemic,3 antitumoral,4 and antiviral activities.5,6 He-
lioxathin is an arylnaphthalene lignan lactone isolated
from the root of Heliopsis scabra Dunal (Compositae)7
and the whole plant of Taiwania cryptomerioides Haya-
ta (Taxodiaceae).8 The total synthesis of this molecule
has been carried out by both inter- and intramolecular
Diels-Alder reactions9-11 and a benzannulation strat-
egy.12
Recently, we have reported that helioxanthin and its
analogues exhibit significant in vitro antiviral activity
against hepatitis B virus (HBV) and flavivirus. It was
found that helioxanthin and its analogues decreased
cellular RNA levels of HBV and antigen expression as
well as selective inhibition of HBV replication in a cell
culture model.13 In the past, anti-HBV nucleotide
analogues such as (-)-(2R,5S)-1-[2-(hydroxymethyl)-
oxathiolan-5-yl]cytosine (3TC), 9-[2-(phosphonomethoxy)-
ethyl]adenine (PMEA), and 9-[4-hydroxy-3-(hydroxy-
methyl)but-1-yl]guanine (PCV) have been evaluated in
clinical trials. However, HBV-infected patients often
experience a recurrence of HBV after a period of
treatment with 3TC or PCV. This recurrence is com-
monly due to the emergence of viral resistance.14,15 Some
of the resistant viruses even gain cross resistance to the
other anti-HBV nucleotide analogues.16 With the inten-
We also have reported that helioxanthin and its
analogues unexpectedly exhibit exceptional anti-HBV
activity against 3TC-resistant HBV.13 Because HBV
replicates via the reverse transcription of a 3.5-kb
pregenomic RNA, the inhibitory action of helioxanthin
must be in an early stage of the viral life cycle.
Helioxanthin and its analogues have a unique mecha-
nism of antiviral action, different from those of the anti-
HBV nucleotide analogues that inhibit HBV only during
viral DNA synthesis. This class of compounds offers a
unique characteristic in anti-HBV chemotherapy. There-
fore, it was of interest to synthesize additional analogues
of helioxanthin for the evaluation of structure-activity
relationships and the development of more selective and
potent antiviral agents.
For the reasons stated above, we synthesized a series
of helioxanthin analogues, particularly through the
modification of the lactone ring and methylenedioxy
group of helioxanthin (2). The analogues were examined
on their antiviral activities against HBV, hepatitis C
virus (HCV), herpes simplex virus type 1 (HSV-1),
herpes simplex virus type 2 (HSV-2), Epstein-Barr
virus (EBV), cytomegalovirus (CMV), and human im-
munodeficiency virus (HIV). Herein, we report a full
account of the synthesis and biological evaluation of
helioxanthin analogues with significant antiviral activ-
ity.
* To whom correspondence should be addressed. Phone: 203-785-
7119. Fax: 203-785-7129. E-mail: cheng.lab@yale.edu.
† Department of Pharmacology, Yale University.
Chemistry
‡ Department of Chemistry, Yale University.
Helioxanthin (2) was synthesized using a previously
§ The first two authors contributed equally to this work.
| Department of Medicine, University of North Carolina.
described approach,11 hydrolyzed with alkali, and es-
10.1021/jm034265a CCC: $30.25 © 2005 American Chemical Society
Published on Web 12/23/2004

Synthesis and Antiviral Activity of Helioxanthin Analogues
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2 535
Scheme 1a
a Reagents and conditions: (a) HO(CH2)OH, p-toluenesulfonic acid, reflux; (b) n-BuLi, piperonal, -78 ×b0°C to room temperature; (c)
maleic anhydride, AcOH, Ac2O, CH2Cl2, 140 °C, 24 h; (d) NaBH4, THF, 0 °C, 3h; (g) NaOH-MeOH/H2O (4:1), 70°C, 1 h; (h) HO(CH2)3OBn
(for 6) or H2N(CH2)3OBn (for 8, DCC, DMAP (for 6) or 1-HOBt (for 8), CH2Cl2, 0 °C; (i) Pd/C, THF, H2, room temperature, 14 h.
terified with a mixture of alkali hydroxide and benzyl
bromide to yield compound 4. The benzyl ester group
of compound 4 was cleaved by alkaline hydrolysis to the
corresponding carboxylic acid and was coupled with
3-benzyloxy-1-propanol using 1,3-dicyclohexylcarbodi-
imide (DCC) and 4-(dimethylamino)pyridine (DMAP) to
afford compound 6. Similarly, the coupling of compound
5 to 3-(benzyloxy)propylamine in the presence of DCC
and 1-hydroxybenzotriazole hydrate (1-HOBt) in CH2-
Cl2 gave compound 8.
The cyclic imides 9 and 11, which exist as an imide/
imidol tautomers, respectively, were prepared by the
Diels-Alder reaction of the corresponding hydroxy-
acetals and maleimide, as depicted in Scheme 2. Com-
pounds 12 and 15, the acid-hydrolyzed products of
imides 9 and 11, were formed from the Diels-Alder
reaction products. Lactams 16, 18, and 22 were pre-
pared by the selective reduction of imides 9 and 11 with
zinc dust in glacial acetic acid. Compounds 12, 16, and
18 were further reacted with iodomethane in KOH/
DMSO to afford the N-methylated products 13, 14, 17,
and, 19. Similarly, the reaction of imide 9 with trim-
ethylsilyldiazomethane (TMSCHN2) gave the O-meth-
ylated product 23.
Mitsunobu reaction of benzyloxyalkyl alcohol with
imide 9 in the presence of diethyl azodicarboxylate
(DEAD) and triphenylphosphine (PPh3) in THF afforded
a N-(benzyloxyalkyl)imide 10, which was selectively
reduced with zinc dust in acetic acid to give the
corresponding lactam 20. Debenzylation of compound

536 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2
Yeo et al.
Scheme 2a
a Reagents and conditions: (a) HO(CH2)OH, p-toluenesulfonic acid, reflux; (b) n-BuLi, piperonal (for 9 and 12) or 3,4-dimethoxyben-
zaldehyde (for 11 and 15), -78 °C to room temperature; (c) maleimide, AcOH, Ac2O, CH2Cl2, 140 °C, 24 h; (d) HO(CH2)3OBn, PPh3,
DEAD, THF, 0 °C to room temperature; (e) KOH/DMSO, MeI, 24 h; (f) Zn/AcOH, 100 °C, 48 h; (g) KOH/DMSO, MeI, 1 h; (h) Pd/C, THF,
H2, room temperature, 20 h.
20 with Pd/C under hydrogen atmosphere provided
N-(hydroxyalkyl)lactam 21.
Anhydride 1 was reacted with TMSCHN2 in a metha-
nolic THF solution to give bis-ester 30, which was
hydrolyzed with KOH in MeOH to yield compounds 31
and 32 (Scheme 4). The hydroxyacetal 1a was subjected
to Diels-Alder addition with diethyl acetylenedicar-
boxylate (DEADC) to afford compound 33, which was
converted to lactone 34 by reduction with lithium
aluminum hydride (LAH). The conversion of imide 9 to
diamide 36 was achieved by treatment with a mixture
of concentrated ammonium hydroxide in THF at 40 °C.
The N-hydroxyimide 24 and N-(hydroxyalkyl)imide
29 were synthesized by reaction of anhydride 1 with the
respective hydroxyamine and hydroxyalkylamine, as
shown in Scheme 3. The reaction of anhydride 1 with
hydrazine hydrate in glacial acetic acid gave a N-
acetoimidoimide 25, which was converted to the cyclic
hydrazide product 28, as well as the lactams 26 and 27
by reaction with zinc dust in acetic acid.

Synthesis and Antiviral Activity of Helioxanthin Analogues
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2 537
Scheme 3a
a Reagents and conditions: (a) NH2OH‚HCl, N(Et)3, EtOH, reflux, 12 h; (b) NH2NH2‚H2O, AcOH, reflux, 24 h; (c) Zn/AcOH, 100 °C, 5
h; (d) H2N(CH2)3OH, toluene, reflux 3 h.
Compounds 2, 18, and 28 were treated with N-
halosuccinimides in the presence of a catalytic amount
of concentrated sulfuric acid to afford compounds 37-
43, which were selectively halogenated at the C-5
position (Scheme 5). The 5-halolactones 37-39 were
subsequently hydrolyzed with NaOH in MeOH to yield
compounds 44-46.
anti-HBV drugs with novel mechanisms of action are
desperately needed. Helioxanthin and its derivatives are
the first small molecules, described thus far, that have
the ability to decrease HBV RNA. This very unique
feature not only has clinical significance but also basic
research value, because an understanding of their
mechanism may lead to alternate therapies. Due to the
growing number of patients harboring lamivudine re-
sistant virus strains, new drugs with different mecha-
nisms are needed for inclusion in and development of
combination therapy regimens. However, this class of
compound may lead to a new area of RNA interference.
This may be the reason this class of compounds could
target more than one virus. The different structure of
these compounds may recognize, interact, and interfere
with different RNA secondary structure, which is the
subject of further investigation. For the reasons stated
Results and Discussion
Conservative estimates place the number of persons
chronically infected with hepatitis B virus (HBV) at
more than 300 million.15 Currently approved agents of
chronic HBV treatment include interferon-R and the
nucleoside analogues lamivudine18 and adefovir dipiv-
oxil.19 However, the side effects of interferon and the
viral resistance of nucleoside analogues make the cur-
rent treatment regimens far from satisfactory. New

538 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2
Yeo et al.
Scheme 4a
a Reagents and conditions: (a) maleic anhydride, AcOH, Ac2O, CH2Cl2, 140 °C, 24 h; (b) TMSCHN2, MeOH/THF (1:2), room temperature,
12 h; (c) KOH/MeOH, reflux 2-24 h; (d) DEADC, AcOH, CH2Cl2, 140 °C, 24 h; (e) LAH, THF, 0 °C to room temperature, 2 h; (f) maleimide,
AcOH, Ac2O, CH2Cl2, 140 °C, 24 h; (g) NH4OH, THF, 40 °C, 72 h. ×b0
above and to achieve an optimal therapeutic window for
this novel structure, the synthesis and biological inves-
tigation of additional helioxanthin derivatives were
undertaken.
and 80% inhibition at 3.0 µM, respectively) as well as
HBV (EC50 ) 0.8 and 0.9 µM, respectively). The most
potent anti-HSV compounds were 12 and 18, which
showed marked inhibition of HSV-1 (EC50 ) 0.15 and
0.29 µM, respectively) and HSV-2 (EC50 < 0.1 and 0.16
µM, respectively). Compound 12 was also found to
exhibit broad-spectrum antiviral activity against HSV-1
(EC50 ) 0.15 µM), HSV-2 (EC50 < 0.1 µM), EBV (EC50
) 9.0 µM), and CMV (EC50 ) 0.45 µM). This compound
was about 140 and 210 times more potent than the
reference drug acylclovir (EC50 ) 21 µM) against HSV-1
and HSV-2, respectively. The cyclic hydrazide 28 and
its brominated product 42 showed moderately potent
anti-HIV activities (EC50 ) 2.7 and 2.5 µM, respec-
tively).
Of these analogues, the lactam 18 and the cyclic
hydrazide 28 derivatives of helioxanthin (2) exhibited
significant in vitro anti-HBV activity (EC50 ) 0.08 and
0.03 µM, respectively), with compound 18 showing the
most potent anti-HCV activity (55% inhibition at 1.0
µM). Compound 12, the acid-hydrolyzed product of the
cyclic imide 9, was also more active than helioxanthin
against HBV (EC50 ) 0.8 µM). Compounds 15 and 22,
containing dimethoxy moieties instead of methylene-
dioxy groups in the C ring of compounds 12 and 18,
displayed potent antiviral activities against HCV (64

Synthesis and Antiviral Activity of Helioxanthin Analogues
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2 539
Scheme 5a
a Reagents and conditions: (a) N-chlorosuccinimide (for 37 and 41), N-bromosuccinimide (for 38 and 42), or N-iodosuccinimide (for 39
and 43), CH3CN or THF, conc H2SO4 (cat.), room temperature or reflux, 20-48 h; (b) aqueous NaOH, MeOH, 70 °C, 1-3 h.
We have previously reported that helioxanthin (2)
exhibited antiviral activity against HBV, whereas retro-
helioxanthin was much less active.13 Alkaline hydrolysis
of the lactone ring in helioxanthin, followed by coupling
with alkyl chains (3-7), resulted in a large decrease in
antiviral potency. In addition, the introduction of halo-
gen atoms at the C-5 position of helioxanthin (2) and
its alkaline-hydrolyzed derivative 3 both produced a
significant loss in activity, as seen in compounds 37-
39 and 44-46. Therefore, it is likely that the introduc-
tion of substituents at the C-5 position is not desirable
for improving the antiviral potency of helioxanthin.
We found that compound 12, the acid-hydrolyzed
product of cyclic imide 9, exhibited potent antiviral
activities against HBV and CMV as well as HSV.
However, it is interesting to note that modifications of
the carboxylic acid and amide groups in compound 12,
by dicarboxylic acid and diamide substituents, resulted
in a significant loss of activity as seen in compounds
12, 32, and 36.
in compounds 19-21 and 26. Therefore, these findings
indicate that the presence of a free NH group at this
position is critical for antiviral activity.
The cyclic hydrazide 28 showed the most potent anti-
HBV activity among those helioxanthin analogues
tested. In addition, compound 28 exhibited moderately
potent activity against HIV. It would therefore be
promising to study helioxanthin analogues that contain
a six-membered ring instead of the five-membered ring
found in the lactam.
Helioxanthin is an interesting antiviral natural prod-
uct with a potentially novel mode of action, as suggested
by its unique ability to lower cellular RNA levels. The
structurally novel helioxanthin analogues described
herein are a promising class of anti-viral compounds
that exhibit a wide spectrum of activity. Current and
future efforts involve the development of more specific
and potent derivatives for anti-viral drug therapy.
Experimental Section
The reduction of imide 9 yielded a lactam 18 and a
retro-lactam 16. The lactam 18 was more potent than
compound 12 against HBV and HCV and as potent as
compound 12 against HSV. In contrast, the retro-lactam
16 was not active at all. This finding indicates that the
“up” carbonyl group of the lactam 18 is an important
feature for the antiviral activity.
Comparing the antiviral activities of compounds 15
and 22 with those of compounds 12 and 18, respectively,
we found that the replacement of a methylenedioxy
group by two methoxy substituents in the C ring
exhibited more or less decreased activities. It would
appear that the introduction of a substituent larger than
the methylenedioxy group is not desirable for increased
potency.
General Methods. All of the solvents and reagents were
obtained from commercial suppliers and were used without
purification. Unless otherwise specified, reactions were per-
formed under a nitrogen atmosphere with exclusion of mois-
ture. All of the reaction mixtures were magnetically stirred
and monitored by thin-layer chromatography (TLC) using
Si250F precoated plates from J. T. Baker (0.25 mm). Flash
column chromatography was performed on 32-63 D 60 Å silica
gel from ICN SiliTech (ICN Biomedicals GmbH). Melting
points were determined with an electrothermal capillary
melting point apparatus and are uncorrected. 1H and 13C NMR
spectra were recorded on a Bruker AM-400 (400 MHz) or GE
QE-plus 300 (300 MHz) spectrometer, chemical shifts (δ) are
reported in parts per million (ppm) using chloroform-d (δ 7.24
1
ppm for H and δ 77.23 ppm for 13C) or DMSO-d6 (2.50 ppm
for 1H and δ 39.43 ppm for 13C) as internal references
(Cambridge Isotope Labs, Inc.), and signals are reported as s
(singlet), d (doublet), t (triplet), q (quartet), m (multiplet), or
br s (broad singlet). Mass spectra were conducted at the Mass
Spectrometry Laboratory of the University of Illinois.
Compounds 10, 13, and 14, the alkylated products of
compounds 9 and 12, turned out to be inactive. More-
over, modifications of the NH group in the lactam 18
resulted in the reduction of antiviral activities as shown
10-Benzo[1,3]dioxol-5-yl-9H-furo[3′,4′:6,7]naphtho[1,2-
d][1,3]dioxol-7-one (2). 10-Benzo[1,3]dioxol-5-yl-furo[3′,4′:

540 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2
Yeo et al.
Table 1. Antiviral Activities of Helioxanthin and Helioxanthin Analogues
antiviral activities
cytotoxicity
(ID50, µM)
(EC50, µM)
compd
HBV
HCVa
>10
3(64)
10(25)
10(71)
>10
10(55)
>10
>10
ND
10(62)
ND
3(58)
>10
>10
3(64)
>10
3(29)
1(55)
>3
HSV-1
HSV-2
EBV
CMV
HIVb
MT-2
CEM
1
2
3
4
5
6
7
8
>10
1.0
>50
2
9
>50
35
25
>20
>20
>20
>20
>20
>20
>15
>15
ND
17.6
7.3
>100
>2.5(T)
>10(T)
>100
>48(T)
>100
>10(T)
>100
ND
>100
2.5
10
>100
48
>100
10
>50
31
30
3.4 >10
>10
>10
>23
>10
ND
>10
ND
0.8
>20
>10
0.8
>10
>10
0.08
1.6
>20
>20
0.9
>10
>5
2.5
>50
>25
>50
>25
>25
ND
>50
ND
0.15
12
>50
0.8
>50
14
0.29
0.67
13
5
0.6
>50
>30
>40
5
17
1.4
>30
>50
>50
>50
>50
23
>50
>50
23
>50
>25
6.5
7
16
>40
>50
>50
>50
8
ND
ND
ND
>50
>25
>50
>25
>25
ND
>50
ND
<0.1
>25
>50
>3
>50
14
0.16
1
>20
7
0.5
NDc
ND
ND
ND
3.7
>50
>50
>50
46
>100
ND
>100
ND
5
10
9d
ND
ND
ND
0.45
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
4.1
ND
ND
ND
ND
8.1
ND
ND
ND
ND
ND
ND
ND
8.8
ND
ND
ND
ND
ND
ND
>20
>20
>20
ND
ND
ND
ND
ND
>100
ND
8.4
29
10
>5
>100
ND
11d
12
ND
9
>5(T)
>26(T)
>70(T)
>10(T)
>100
>26(T)
>4(T)
>8(T)
>28(T)
5
>16(T)
>100
>16(T)
>100
>7(T)
>25(T)
15(T)
>22(T)
>28(T)
>90(T)
>100
>15(T)
>13(T)
>24(T)
>100
>50(T)
>100
>80(T)
>54(T)
>30(T)
6
13
>20
>20
>20
>20
>20
11
26
14
70
76
15
10
3
16
>100
26
90
17
27
18
4
8
4.5
6
19
>20
>20
>20
>20
>20
>5
>20
13
>20
>25
>5
20
10(85)
10(58)
3(80)
>10
28
67
21
22
22
22
16
5
23
>50
>30
>40
10
40
1.4
>100
16
>100
17
24
>10
1
>20
0.03
>5
>10
25
>10
>100
7
93
26
>10
40
27
10(25)
10(74)
>10
25
32
28
16
50
29
>20
>20
>20
>10
>10
>20
>20
>10
>60
>40
>20
>10
>20
>10
>10
>10
>18
ND
>30
>50
>50
>50
>50
28
>50
>50
>25
>50
>25
>20
>40
>20
>40
>50
>50
>50
21
22
27
30
10(93)
>10
>10
10(62)
>10
>20
>20
>20
>10
>10
>20
>20
>20
>15
>10
>20
>20
>20
>20
>20
>20
>20
ND
28
50
31
90
74
32
>100
15
>100
39
33
34
13
24
>100
50
>100
80
54
30
31
35
10(60)
>10
>100
>100
27
36
37
>10
38
>10
100
70
38
>100
28
40
39
>10
40
10(32)
10(60)
3(45)
10(52)
>10
41
42
>100
35
43
2
44
>60(T)
>50(T)
>80(T)
ND
60
>100
46.5
>100
ND
ND
5
45
ND
10(36)
ND
ND
ND
10u/ml (90)
50
46
80
ACV
3TC
ddC
Interferon
0.02
ND
ND
ND
ND
70
ND
ND
ND
0.4
ND
ND
0.8
ND
ND
ND
ND
a The values in parentheses are percent inhibition. b (T) indicates toxicity. c Not determined. d Low solubility.
6,7]naphtho[1,2-d][1,3]dioxole-7,9-dione (1) was synthesized
using a literature procedure.11 To a mixture of sodium boro-
hydride (218 mg, 5.8 mmol) in dry THF (100 mL) was added
dropwise anhydride 1 (1.90 g, 5.25 mmol) in dry THF (100 mL)
at 0 °C. The mixture was stirred at room temperature for 1 h
and then acidified to pH 1-2 with 10% aqueous HCl solution.
After being stirred for 1 h, the mixture was extracted with
ether (3 × 100 mL), concentrated in vacuo, and chromato-
graphed using CHCl3 to give a lactone 2 (1.44 g, 79%) as a
pale yellow powder. Mp: 242-244 °C. 1H NMR (DMSO-d6) δ:
8.56 (s, 1H, H4), 7.93 (d, 1H, H5, J ) 8.4 Hz), 7.50 (d, 1H, H6,
J ) 8.4 Hz), 7.01 (d, 1H, H2′, J ) 1.5 Hz), 6.95 (d, 1H, H5′, J
) 8.1 Hz), 6.87 (dd, 1H, H6′, J ) 1.5, 8.1 Hz), 6.08 (AB, 2H,
3′,4′-OCH2O-, ∆δ ) 15.6 Hz, J ) 0.9 Hz), 5.99 (AB, 2H, 7,8-
OCH2O-, ∆δ ) 6.0 Hz, J ) 0.9 Hz), 5.28 (s, 2H, lactone-CH2-
). MS (FAB, positive) m/z: 349 [M + H]+.
Aqueous NaOH solution (1 N, 2.9 mL) was added to a solution
of 2 (100 mg, 0.29 mmol) in MeOH (10 mL). The mixture was
stirred at 70 °C for 1 h. The solvent was evaporated to give a
crude product, which was purified by silica gel column chro-
matography using CH2Cl2/MeOH (3:1, v/v) to afford 3 (110 mg,
1
98%) as a white powder. Mp: 128-130 °C. H NMR (DMSO-
d6) δ: 8.16 (s, 1H, H4), 7.52 (d, 1H, H5, J ) 8.7 Hz), 7.24 (d,
1H, H6, J ) 8.7 Hz), 6.88 (d, 1H, H5′, J ) 8.4 Hz), 6.73 (s, 1H,
H2′), 6.64 (d, 1H, H6′, J ) 8.4 Hz), 6.05 (AB, 2H, 3′,4′-OCH2O-,
∆δ ) 18.9 Hz), 5.79 (AB, 2H, 7,8-OCH2O-, ∆δ ) 8.4 Hz), 4.16
(s, 2H, 2-CH2OH).
9-Benzo[1,3]dioxol-5-yl-8-benzyloxymethyl-naphtho-
[1,2-d][1,3]dioxole-7-carboxylic Acid Benzyl Ester (4). A
mixture of 3 (78 mg, 0.2 mmol), benzyl bromide (0.38 mL, 3.2
mmol), and powdered KOH (168 mg) was heated at 140 °C for
3 h and then cooled to room temperature. The mixture was
diluted with water (100 mL) and extracted with EtOAc (3 ×
100 mL). The extract was washed with water (3 × 100 mL),
9-Benzo[1,3]dioxol-5-yl-8-hydroxymethyl-naphtho[1,2-
d][1,3]dioxole-7-carboxylic Acid Monosodium Salt (3).

Synthesis and Antiviral Activity of Helioxanthin Analogues
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2 541
dried over MgSO4, and concentrated in vacuo. The residue was
purified by column chromatography on silica gel using CH2-
Cl2 to give 4 (56 mg, 51%) as a colorless liquid. 1H NMR
(CDCl3) δ: 8.27 (s, 1H, H4), 7.51 (d, 1H, H5, J ) 8.4 Hz), 7.23-
7.44 (m, 10H, 2 × OCH2Ph), 7.22 (d, 1H, H6, J ) 8.4 Hz), 6.82
(d, 1H, H5′, J ) 7.8 Hz), 6.77 (d, 1H, H2′, J ) 1.5 Hz), 6.71
(dd, 1H, H6′, J ) 1.5, 7.8 Hz), 6.05 (AB, 2H, 3′,4′-OCH2O-,
∆δ ) 10.2 Hz, J ) 1.2 Hz), 5.84 (AB, 2H, 7,8-OCH2O-, ∆δ )
4.8 Hz, J ) 1.2 Hz), 5.34 (s, 2H, 3-COOCH2Ph), 4.67 (s, 2H,
2-CH2OCH2Ph), 4.32 (s, 2H, 2-CH2OBn). MS (EI) m/z: 546
[M]+.
9-Benzo[1,3]dioxol-5-yl-8-benzyloxymethyl-naphtho-
[1,2-d][1,3]dioxole-7-carboxylic Acid (5). A solution of 4 (56
mg, 0.1 mmol) and NaOH (16 mg, 0.4 mmol) in MeOH/H2O
(4:1, 2 mL) was heated at 70 °C for 12 h. The solvent was
evaporated to dryness, and the residue was dissolved in water.
The aqueous solution was acidified to pH 1-2 with 10%
aqueous HCl solution and extracted with ether (3 × 50 mL).
The extract was washed with water and brine and dried over
MgSO4. The evaporation of solvent yielded 5 (32 mg, 70%) as
a white powder. Mp: 219-221 °C. 1H NMR (DMSO-d6) δ: 8.27
(s, 1H, H4), 7.70 (d, 1H, H5, J ) 8.7 Hz), 7.38 (d, 1H, H6, J )
8.7 Hz), 7.17-7.25 (m, 5H, OCH2Ph), 6.89 (d, 1H, H5′, J ) 8.1
Hz), 6.79 (d, 1H, H2′, J ) 1.5 Hz), 6.65 (dd, 1H, H6′, J ) 1.5,
8.1 Hz), 6.06 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 18.0 Hz, J ) 0.6
Hz), 5.85 (AB, 2H, 7,8-OCH2O-, ∆δ ) 9.3 Hz, J ) 0.9 Hz),
4.53 (s, 2H, 2-CH2OCH2Ph), 4.24 (s, 2H, 2-CH2OBn). MS (FAB,
positive) m/z: 457 [M + H]+.
9-Benzo[1,3]dioxol-5-yl-8-benzyloxymethyl-naphtho-
[1,2-d][1,3]dioxole-7-carboxylic Acid 3-Benzyloxy-propyl
Ester (6). To a stirred solution of 3-benzyloxy-1-propanol (16.6
mg, 0.1 mmol), 1,3-dicyclohexylcarbodiimide (31 mg, 0.15
mmol), and 4-(dimethylamino)pyridine (14.6 mg, 0.12 mmol)
in dry CH2Cl2 (1 mL) was added dropwise compound 5 (54.8
mg, 0.12 mmol) in CH2Cl2 (2 mL) at 0 °C. The mixture was
stirred for 4 h at room temperature and concentrated in vacuo.
The residue was chromatographed over silica gel using CH2-
Cl2/MeOH (50:1, v/v) to give 6 (61.2 mg, 84%) as a yellow liquid.
1H NMR (CDCl3) δ: 8.16 (s, 1H, H4), 7.47 (d, 1H, H5, J ) 8.7
Hz), 7.20-7.45 (m, 11H, H6 + 2 × OCH2Ph), 6.82 (d, 1H, H5′,
J ) 7.8 Hz), 6.76 (d, 1H, H2′, J ) 1.5 Hz), 6.70 (dd, 1H, H6′,
J ) 1.5, 7.8 Hz), 6.06 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 9.9 Hz, J
) 1.5 Hz), 5.84 (AB, 2H, 7,8-OCH2O-, ∆δ ) 4.5 Hz, J ) 1.5
Hz), 4.65 (s, 2H, OCH2Ph), 4.53 (s, 2H, OCH2Ph), 4.42 (t, 2H,
3-COOCH2(CH2)2OBn, J ) 6.3 Hz), 4.35 (s, 2H, 2-CH2OBn),
3.62 (t, 2H, 3-COO(CH2)2CH2OBn, J ) 6.3 Hz), 2.06 (quintet,
2H, 3-COOCH2CH2CH2OBn, J ) 6.3 Hz). MS (EI) m/z: 604
[M]+.
9-Benzo[1,3]dioxol-5-yl-8-methyl-naphtho[1,2-d][1,3]-
dioxole-7-carboxylic Acid 3-Hydroxy-propyl Ester (7). A
mixture of 6 (48 mg, 0.079 mmol) and 10% Pd/C (12 mg) in
dry THF (5 mL) was stirred for 14 h at room temperature
under 1 atm of hydrogen. The mixture was filtered, and the
filtrate evaporated at reduced pressure. The residue was
purified by column chromatography on silica gel using CH2-
Cl2/MeOH (40:1, v/v) to yield 7 (30 mg, 93%) as a yellow oil.
1H NMR (CDCl3) δ: 8.32 (s, 1H, H4), 7.50 (d, 1H, H5, J ) 8.7
Hz), 7.18 (d, 1H, H6, J ) 8.7 Hz), 6.87 (d, 1H, H5′, J ) 7.8
Hz), 6.72 (d, 1H, H2′, J ) 1.5 Hz), 6.68 (dd, 1H, H6′, J ) 1.5,
7.8 Hz), 6.05 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 9.6 Hz, J ) 1.5
Hz), 5.83 (AB, 2H, 7,8-OCH2O-, ∆δ ) 1.5 Hz, J ) 1.5 Hz),
4.54 (t, 2H, 3-COOCH2(CH2)2OH, J ) 6.3 Hz), 3.83 (t, 2H,
3-COO(CH2)2CH2OH, J ) 6.3 Hz), 2.34 (s, 3H, 2-CH3), 2.06
(quintet, 2H, 3-COOCH2CH2CH2OH, J ) 6.3 Hz). MS (EI)
m/z: 408 [M]+.
between 1 N aqueous HCl solution and CH2Cl2. The aqueous
layer was alkalified to pH 10 with 10% aqueous NaOH solution
and extracted with CH2Cl2 (3 × 100 mL). The extract was dried
over MgSO4 and concentrated in vacuo. The residue was
purified by silica gel column chromatography using CH2Cl2/
MeOH (3:1 to 2:1, v/v) to give 3-(benzyloxy)propylamine (1.37
g, 8.3%) as a yellow oil. To a mixture of 5 (32 mg, 0.07 mmol)
and 3-(benzyloxy)propylamine (11.6 mg, 0.07 mmol), and
1-hydroxybenzotriazole hydrate (9.5 mg, 0.07 mmol) in CH2-
Cl2 (5 mL) was added dropwise 1,3-dicyclohexylcarbodiimide
(14.4 mg, 0.07 mmol) in CH2Cl2 (2 mL) at 0 °C. The reaction
mixture was stirred for 18 h at room temperature and
concentrated in vacuo. The residue was purified by silica gel
column chromatography using CH2Cl2/MeOH (30:1, v/v) to
afford 8 (36 mg, 85%) as a pale yellow liquid. 1H NMR (CDCl3)
δ: 8.05 (s, 1H, H4), 7.44 (d, 1H, H5, J ) 8.7 Hz), 7.19-7.28
(m, 11H, H6 + 2 × OCH2Ph), 6.78-6.82 (m, 3H, H2′ + H5′ +
H6′), 6.06 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 6.9 Hz, J ) 1.5 Hz),
5.84 (AB, 2H, 7,8-OCH2O-, ∆δ ) 4.2 Hz, J ) 1.5 Hz), 4.45 (s,
4H, 2 × OCH2Ph), 4.38 (s, 2H, 2-CH2OBn), 3.55 (m, 4H,
3-CONHCH2CH2CH2OBn), 1.87 (quintet, 2H, 3-CONHCH2CH2-
CH2OBn, J ) 6.3 Hz). MS (FAB, positive) m/z: 604 [M + H]+.
10-Benzo[1,3]dioxol-5-yl-1,3-dioxa-8-aza-dicyclopenta-
[a,g]naphthalene-7,9-dione (9) and 9-Benzo[1,3]dioxol-
5-yl-7-carbamoyl-naphtho[1,2-d][1,3]dioxole-8-carboxy-
lic Acid (12). The hydroxyacetal 1a (7.34 g, 21.3 mmol),
maleimide (2.07 g, 21.3 mmol), acetic anhydride (7 mL), CH2-
Cl2 (7 mL), and glacial acetic acid (3 mL) were heated at 140
°C for 24 h. The cooled mixture was diluted with CH2Cl2 (100
mL), washed with 5% NaHCO3 solution (3 × 100 mL), dried
over MgSO4, and concentrated under vacuum. The silica gel
column chromatography of the crude product using CH2Cl2/
acetone (30:1 to 3:1, v/v) gave two fractions. The first fraction
eluted with CH2Cl2/acetone (30:1, v/v) gave a yellow solid that
was then recrystallized from acetone to give an imide 9 (1.33
g, 17%). Mp: 306-308 °C. 1H NMR (DMSO-d6) δ: 8.61 (s, 1H,
H4), 7.98 (d, 1H, H5, J ) 8.7 Hz), 7.62 (d, 1H, H6, J ) 8.7
Hz), 6.93 (d, 1H, H2′, J ) 1.5 Hz), 6.92 (d, 1H, H5′, J ) 7.8
Hz), 6.79 (dd, 1H, H6′, J ) 1.5, 7.8 Hz), 6.09 (AB, 2H, 3′,4′-
OCH2O-, ∆δ ) 5.7 Hz), 5.99 (AB, 2H, 7,8-OCH2O-, ∆δ ) 4.5
Hz). MS (FAB, positive) m/z: 362 [M + H]+.
The second fraction eluted with CH2Cl2/acetone (3:1, v/v)
afforded a pale yellow solid (12, 1.66 g, 21%) that was identified
as the acid hydrolysis product of imide 9. Mp: 207-209 °C.
1H NMR (CDCl3) δ: 8.31 (s, 1H, H4), 7.62 (s, 1H, 2-COOH),
7.60 (d, 1H, H5, J ) 8.4 Hz), 7.27 (d, 1H, H6, J ) 8.4 Hz),
6.87-6.92 (m, 3H, H2′ + H5′ + H6′), 6.03 (s, 2H, 3′,4′-OCH2O-
), 5.97 (s, 2H, 7,8-OCH2O-). 13C NMR (DMSO-d6) δ: 169.40,
146.52, 146.46, 145.13, 140.95, 138.70, 130.88, 130.08, 129.13,
128.45, 124.63, 123.35, 122.72, 119.83, 110.95, 109.85, 107.61,
100.91, 79.11, 44.28. MS (FAB, positive) m/z: 336 [M - CONH2
+ H]+. Regiochemical assignment of the carboxylate and
carboxamide groups for compound 12 was carried out by direct
comparison with the chemical shifts for H-4, H-5, and H-6 in
compound 32. The chemical shits of H-4 (8.61 ppm), H-5 (7.98
ppm), and H-6 (7.62 ppm) in compound 12 are downfield
shifted compared with the chemical shifts of H-4 (8.25 ppm),
H-5 (7.53 ppm), and H-6 (7.24 ppm) in compound 32, indicating
that they are adjacent to the carboxamide in compound 12,
rather than the carboxylate as in compound 32.
10-Benzo[1,3]dioxol-5-yl-8-(3-benzyloxy-propyl)-1,3-di-
oxa-8-aza-dicyclopenta[a,g]naphthalene-7,9-dione (10).
A solution of diethyl azodicarboxylate (52 mg, 0.3 mmol) in
dry THF (3 mL) was added dropwise to a stirred solution of 9
(108 mg, 0.3 mmol), 3-benzyloxy-1-propanol (50 mg, 0.3 mmol),
and triphenylphosphine (79 mg, 0.3 mmol) in dry THF (6 mL)
at 0 °C over 30 min. The mixture was stirred at room
temperature for 30 h and then concentrated under reduced
pressure. The residue was purified by column chromatography
on silica gel, eluting with n-hexane/EtOAc (2:1, v/v) to give 10
9-Benzo[1,3]dioxol-5-yl-8-benzyloxymethyl-naphtho-
[1,2-d][1,3]dioxole-7-carboxylic Acid (3-Benzyloxy-pro-
pyl)-amide (8). To a stirred solution of 3-amino-1-propanol
(7.51 g, 0.1 mol) in THF (150 mL) was added 60% sodium
hydride dispersion in mineral oil (4 g, 0.1 mol) in small portions
at room temperature. The mixture was stirred for 30 min
under nitrogen, and benzyl bromide (11.9 mL, 0.1 mol) was
added. The mixture was stirred for 10 h at room temperature
and concentrated in vacuo. The residue was partitioned
1
(56 mg, 37%) as a yellow powder. Mp: 153-155 °C. H NMR
(CDCl3) δ: 8.24 (s, 1H, H4), 7.66 (d, 1H, H5, J ) 8.4 Hz), 7.35
(d, 1H, H6, J ) 8.4 Hz), 7.24-7.26 (m, 5H, OCH2Ph), 6.78-
6.91 (m, 3H, H2′ + H5′ + H6′), 6.07 (AB, 2H, 3′,4′-OCH2O-,

542 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2
Yeo et al.
∆δ ) 15.3 Hz, J ) 1.5 Hz), 5.95 (AB, 2H, 7,8-OCH2O-, ∆δ )
5.4 Hz, J ) 1.2 Hz), 4.45 (s, 2H, OCH2Ph), 3.80 (t, 2H,
NCH2(CH2)2OBn, J ) 6.0 Hz), 3.54 (t, 2H, N(CH2)2CH2OBn,
J ) 6.0 Hz), 2.01 (quintet, 2H, NCH2CH2CH2OBn, J ) 6.0 Hz).
MS (EI) m/z: 509 [M]+.
activated zinc dust (328 mg) was added thereto and then
heated in an oil bath at 100 °C for 48 h. The insoluble solid
was filtered off, and the majority of acetic acid was removed
with a rotary evaporator. The obtained residue was neutralized
to pH 7 with 10% aqueous NaOH solution and extracted with
CHCl3 (3 × 100 mL). The extract was washed with water, dried
over MgSO4, and concentrated in vacuo. The crude product
was purified by column chromatography on silica gel, eluting
with CH2Cl2/acetone (3:1 to 2:1, v/v) to give two fractions. The
first (minor) and the second (major) fractions afforded a retro-
lactam 16 (12 mg, 7%) and a lactam 18 (56 mg, 32%) as pale
yellow solids, respectively. 16. Mp: 267-269 °C. 1H NMR
(DMSO-d6) δ: 8.48 (s, 1H, NH), 7.99 (s, 1H, H4), 7.64 (d, 1H,
H5, J ) 8.7 Hz), 7.42 (d, 1H, H6, J ) 8.7 Hz), 6.83 (d, 1H,
H5′, J ) 7.8 Hz), 6.80 (d, 1H, H2′, J ) 1.5 Hz), 6.66 (dd, 1H,
H6′, J ) 1.5, 7.8 Hz), 6.04 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 3.9
Hz), 5.86 (AB, 2H, 7,8-OCH2O-, ∆δ ) 5.4 Hz), 4.38 (br s, 2H,
lactam-CH2-). MS (FAB, positive) m/z: 348 [M + H]+. 18.
10-(3,4-Dimethoxy-phenyl)-1,3-dioxa-8-aza-dicyclopen-
ta[a,g]naphthalene-7,9-dione (11) and 7-Carbamoyl-9-
(3,4-dimethoxy-phenyl)-naphtho[1,2-d][1,3]dioxole-8-car-
boxylic Acid (15). The acetal (2.25 g, 11.6 mmol) of piperonal
was dissolved in dry THF (40 mL) under nitrogen and cooled
to -78 °C, and n-butyllithium (1.6 M in hexanes, 7.98 mL,
12.8 mmol) was added dropwise over 30 min. The mixture was
stirred for 15 min and then at 0 °C for 20 min. The mixture
was again cooled to -78 °C, followed by dropwise addition of
3,4-dimethoxybenzaldehyde (1.93 g, 11.6 mmol) in THF (15
mL). After being stirred for 20 min, the solution was gradually
warmed to room temperature and stirred for another 1.5 h,
followed by the addition of water (100 mL). The resulting
mixture was extracted with ether (3 × 100 mL), dried over
MgSO4, and concentrated to provide a crude hydroxyacetal 1b
(4.18 g). The crude product was employed in the following
reaction without further purification.
The hydroxyacetal 1b (4.18 g, 11.6 mmol), maleimide (1.13
g, 11.6 mmol), acetic anhydride (4 mL), CH2Cl2 (4 mL), and
glacial acetic acid (1.8 mL) were heated at 140 °C for 24 h.
The cooled mixture was diluted with CH2Cl2 (100 mL), washed
with 5% NaHCO3 solution (3 × 100 mL), dried over MgSO4,
and concentrated in vacuo. The silica gel column chromatog-
raphy of the crude product using CH2Cl2/acetone (30:1 to 3:1,
v/v) gave two fractions. The first fraction eluted with CH2Cl2/
acetone (30:1, v/v) gave a yellow solid, which was then
recrystallized from acetone to give imide 11 (800 mg, 18%).
Mp 288-290 °C. 1H NMR (DMSO-d6) δ: 8.60 (s, 1H, H4), 7.98
(d, 1H, H5, J ) 8.7 Hz), 7.62 (d, 1H, H6, J ) 8.7 Hz), 6.88-
6.96 (m, 3H, H2′ + H5′ + H6′), 5.98 (AB, 2H, 7,8-OCH2O-,
∆δ ) 3.3 Hz), 3.81, 3.68 (each s, 2 × 3H, 3′-OCH3 + 4′-OCH3).
MS (FAB, positive) m/z: 378 [M + H]+.
1
Mp: 252-254 °C. H NMR (DMSO-d6) δ: 8.59 (s, 1H, NH),
8.27 (s, 1H, H4), 7.83 (d, 1H, H5, J ) 8.7 Hz), 7.41 (d, 1H, H6,
J ) 8.7 Hz), 6.98 (s, 1H, H2′), 6.94 (d, 1H, H5′, J ) 7.8 Hz),
6.84 (d, 1H, H6′, J ) 7.8 Hz), 6.07 (AB, 2H, 3′,4′-OCH2O-, ∆δ
) 14.4 Hz), 5.93 (AB, 2H, 7,8-OCH2O-, ∆δ ) 6.0 Hz), 4.17 (br
s, 2H, lactam-CH2-). 13C NMR (DMSO-d6) δ: 169.83, 146.98,
146.91, 145.58, 141.40, 139.14, 131.33, 130.53, 129.59, 128.90,
125.07, 123.79, 123.16, 120.28, 111.38, 110.28, 108.04, 101.35,
79.55, 44.71. MS (FAB, positive) m/z: 348 [M + H]+.
10-Benzo[1,3]dioxol-5-yl-8-methyl-7,8-dihydro-1,3-dioxa-
8-aza-dicyclopenta[a,g]naphthalen-9-one (17). Powdered
KOH (11.2 mg, 0.2 mmol) was added to DMSO (1 mL). After
the mixture was stirred for 5 min, compound 16 (18 mg, 0.05
mmol) was added, followed immediately by iodomethane (0.006
mL, 0.1 mmol). The mixture was stirred for 1 h and poured
into water (15 mL), then the product was extracted with CH2-
Cl2 (3 × 20 mL). The combined organic extract was washed
with water (5 × 20 mL), dried over MgSO4, and concentrated
in vacuo. The residue was purified by column chromatography
on silica gel using CH2Cl2/acetone (10:1, v/v) to provide 17 (12
mg, 66%) as a pale yellow powder. Mp: 242-244 °C. 1H NMR
(CDCl3) δ: 7.79 (s, 1H, H4), 7.50 (d, 1H, H5, J ) 8.4 Hz), 7.29
(d, 1H, H6, J ) 8.4 Hz), 6.83-6.88 (m, 3H, H2′ + H5′ + H6′),
6.04 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 21.6 Hz, J ) 1.5 Hz), 5.89
(AB, 2H, 7,8-OCH2O-, ∆δ ) 2.4 Hz), 4.46 (s, 2H, lactam-CH2-
), 3.14 (s, 3H, NCH3). MS (FAB, positive) m/z: 362 [M + H]+.
10-Benzo[1,3]dioxol-5-yl-8-methyl-8,9-dihydro-1,3-dioxa-
8-aza-dicyclopenta[a,g]naphthalen-7-one (19). Powdered
KOH (11.2 mg, 0.2 mmol) was added to DMSO (1 mL). After
the mixture was stirred for 5 min, compound 18 (18 mg, 0.05
mmol) was added, followed immediately by iodomethane (0.006
mL, 0.1 mmol). The mixture was stirred for 1 h and poured
into water (15 mL), then the product was extracted with CH2-
Cl2 (3 × 20 mL). The combined organic extract was washed
with water (5 × 20 mL), dried over MgSO4, and concentrated
in vacuo. The residue was purified by column chromatography
on silica gel using CH2Cl2/acetone (10:1, v/v) to give 19 (12
mg, 66%) as a pale yellow powder. Mp: 234-236 °C. 1H NMR
(CDCl3) δ: 8.30 (s, 1H, H4), 7.66 (d, 1H, H5, J ) 8.4 Hz), 7.26
(d, 1H, H6, J ) 8.4 Hz), 6.81-6.91 (m, 3H, H2′ + H5′ + H6′),
6.06 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 8.4 Hz, J ) 1.2 Hz), 5.92
(AB, 2H, 7,8-OCH2O-, ∆δ ) 7.8 Hz, J ) 1.5 Hz), 4.26 (q, 2H,
lactam-CH2-, J ) 6.3 Hz), 3.18 (s, 3H, NCH3). MS (EI) m/z:
361 [M]+.
10-Benzo[1,3]dioxol-5-yl-8-(3-benzyloxy-propyl)-8,9-di-
hydro-1,3-dioxa-8-aza-dicyclopenta[a,g]naphthalen-7-
one (20). Compound 10 (40 mg, 0.08 mmol) was dissolved in
glacial acetic acid (3 mL), the freshly activated zinc dust (206
mg) was added thereto, and then the mixture was heated in
an oil bath at 100 °C for 48 h. The insoluble solid was filtered
off, and the majority of acetic acid was removed with a rotary
evaporator. The obtained residue was neutralized to pH 7 with
10% aqueous NaOH solution and extracted with CHCl3 (3 ×
50 mL). The combined organic extract was washed with water
(2 × 100 mL), dried over MgSO4, and concentrated in vacuo.
The crude product was chromatographed with n-hexane/EtOAc
The second fraction eluted with CH2Cl2/acetone (3:1, v/v)
afforded a white solid (15, 213 mg, 5%), which was identified
as the acid hydrolysis product of imide 11. Mp: 240-242 °C.
1H NMR (DMSO-d6) δ: 8.42 (s, 1H, H4), 7.70 (d, 1H, H5, J )
8.7 Hz), 7.41 (d, 1H, H6, J ) 8.7 Hz), 6.96-7.00 (m, 3H, H2′
+ H5′ + H6′), 5.98 (s, 2H, 7,8-OCH2O-), 3.79, 3.74 (each s, 2 ×
3H, 3′-OCH3 + 4′-OCH3). MS (FAB, positive) m/z: 352 [M -
CONH2 + H]+.
9-Benzo[1,3]dioxol-5-yl-7-methylcarbamoyl-naphtho-
[1,2-d][1,3]dioxole-8-carboxylic Acid (13) and 9-Benzo-
[1,3]dioxol-5-yl-7-dimethylcarbamoyl-naphtho[1,2-d][1,3]-
dioxole-8-carboxylic Acid (14). To DMSO (3 mL) was added
powdered KOH (64 mg, 1.1 mmol). After the mixture was
stirred for 5 min, compound 12 (108 mg, 0.28 mmol) was
added, followed immediately by iodomethane (0.035 mL, 0.57
mmol). The mixture was stirred for 24 h and poured into water
(30 mL), and then the product was extracted with CH2Cl2 (3
× 30 mL). The combined organic extract was washed with
water (5 × 30 mL), dried over MgSO4, and concentrated in
vacuo. The resulting product was purified by column chroma-
tography on silica gel using CH2Cl2/acetone (10:1, v/v) to yield
13 (20 mg, 18%) as a pale yellow powder and 14 (80 mg, 71%)
as a pale yellow oil, respectively. 13. Mp: 223-225 °C. 1H
NMR (CDCl3) δ: 8.26 (s, 1H, H4), 7.60 (d, 1H, H5, J ) 8.7
Hz), 7.57 (s, 1H, 2-COOH), 7.25 (d, 1H, H6, J ) 8.7 Hz), 6.87-
6.92 (m, 3H, H2′ + H5′ + H6′), 6.04 (s, 2H, 3′,4′-OCH2O-),
5.97 (s, 2H, 7,8-OCH2O-), 3.07 (d, 3H, 3-CONHCH3, J ) 4.8
Hz). 14. 1H NMR (CDCl3) δ: 7.85 (s, 1H, H4), 7.52 (d, 1H, H5,
J ) 8.7 Hz), 7.32 (s, 1H, 2-COOH), 7.25 (d, 1H, H6, J ) 8.7
Hz), 6.86-6.92 (m, 3H, H2′ + H5′ + H6′), 6.03 (s, 2H, 3′,4′-
OCH2O-), 5.95 (s, 2H, 7,8-OCH2O-), 3.12 (s, 6H, 3-CON-
(CH3)2).
10-Benzo[1,3]dioxol-5-yl-7,8-dihydro-1,3-dioxa-8-aza-
dicyclopenta[a,g]naphthalen-9-one (16) and 10-Benzo-
[1,3]dioxol-5-yl-8,9-dihydro-1,3-dioxa-8-aza-dicyclopenta-
[a,g]naphthalen-7-one (18). Compound 9 (181 mg, 0.5 mmol)
was dissolved in glacial acetic acid (5 mL), and the freshly

Synthesis and Antiviral Activity of Helioxanthin Analogues
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2 543
1
(2:1 to 1:1, v/v) to afford 20 (26 mg, 66%) as a yellow oil. H
N-(10-Benzo[1,3]dioxol-5-yl-7,9-dioxo-7,9-dihydro-1,3-
dioxa-8-aza-dicyclopenta[a,g]naphthalen-8-yl)-acet-
amide (25). A solution of anhydride 1 (145 mg, 0.4 mmol) in
glacial acetic acid (10 mL) was refluxed with hydrazine hydrate
(0.023 mL, 0.48 mmol) for 24 h under nitrogen and then
poured, after cooling, into ice water. The resulting precipitate
was filtered and dried under reduced pressure. The residue
was purified by column chromatography on silica gel using
CH2Cl2/MeOH (30:1 to 20:1, v/v) to give 25 (143 mg, 86%) as
NMR (CDCl3) δ: 8.30 (s, 1H, H4), 7.66 (d, 1H, H5, J ) 8.4
Hz), 7.28 (d, 1H, H6, J ) 8.4 Hz), 7.25 (br s, 5H, OCH2Ph),
6.77-6.90 (m, 3H, H2′ + H5′ + H6′), 6.06 (AB, 2H, 3′,4′-
OCH2O-, ∆δ ) 9.6 Hz, J ) 1.2 Hz), 5.92 (AB, 2H, 7,8-OCH2O-,
∆δ ) 4.8 Hz, J ) 1.2 Hz), 4.47 (s, 2H, OCH2Ph), 4.25 (q, 2H,
q, lactam-CH2-, J ) 6.6 Hz), 3.73 (t, 2H, NCH2(CH2)2OBn, J
) 6.0 Hz), 3.56 (t, 2H, N(CH2)2CH2OBn, J ) 6.0 Hz), 1.98
(quintet, 2H, NCH2CH2CH2OBn, J ) 6.0 Hz). MS (EI) m/z:
495 [M]+.
1
a yellow solid. Mp: 281-283 °C. H NMR (CDCl3) δ: 8.34 (s,
10-Benzo[1,3]dioxol-5-yl-8-(3-hydroxy-propyl)-8,9-di-
hydro-1,3-dioxa-8-aza-dicyclopenta[a,g]naphthalen-7-
one (21). The mixture of 20 (16 mg, 0.032 mmol) and 10%
Pd/C (4 mg) in dry THF (3 mL) was stirred for 20 h at room
temperature under 1 atm of hydrogen. The Pd/C was removed
by filtration and the solvent evaporated under reduced pres-
sure. The residue was purified by column chromatography on
silica gel using CH2Cl2/acetone (3:1 to 2:1, v/v) to yield 21 (9
mg, 69%) as a white solid. Mp: 213-215 °C. 1H NMR (CDCl3)
δ: 8.31 (s, 1H, H4), 7.67 (d, 1H, H5, J ) 8.4 Hz), 7.28 (d, 1H,
H6, J ) 8.4 Hz), 6.82-6.92 (m, 3H, H2′ + H5′ + H6′), 6.07
(AB, 2H, 3′,4′-OCH2O-, ∆δ ) 8.7 Hz, J ) 1.2 Hz), 5.93 (AB,
2H, 7,8-OCH2O-, ∆δ ) 4.8 Hz, J ) 1.2 Hz), 4.28 (q, 2H,
lactam-CH2-, J ) 4.8 Hz), 3.77 (t, 2H, NCH2(CH2)2OH, J )
4.8 Hz), 3.59 (t, 2H, N(CH2)2CH2OH, J ) 4.8 Hz), 2.65 (br s,
1H, OH), 1.81 (quintet, 2H, NCH2CH2CH2OH, J ) 4.8 Hz).
MS (EI) m/z: 405 [M]+.
10-(3,4-Dimethoxy-phenyl)-8,9-dihydro-1,3-dioxa-8-aza-
dicyclopenta[a,g]naphthalen-7-one (22). Compound 11
(400 mg, 1.06 mmol) was dissolved in glacial acetic acid (10
mL), and freshly activated zinc dust (695 mg) was added
thereto, then heated in an oil bath at 100 °C for 48 h. The
insoluble solid was filtered off, and the majority of acetic acid
was removed with a rotary evaporator. The obtained residue
was neutralized to pH 7 with 10% aqueous NaOH solution and
then extracted with CHCl3 (3 × 100 mL). The extract was
washed with water, dried over MgSO4, and concentrated in
vacuo. The crude product was purified by column chromatog-
raphy on silica gel, eluting with CH2Cl2/acetone (3:1 to 2:1,
v/v) to give 22 (95 mg, 25%) as a pale yellow solid. Mp: 258
°C (dec). 1H NMR (CDCl3) δ: 8.36 (s, 1H, H4), 7.69 (d, 1H,
H5, J ) 8.7 Hz), 7.29 (d, 1H, H6, J ) 8.7 Hz), 6.86-6.95 (m,
3H, H2′ + H5′ + H6′), 5.90 (s, 2H, 7,8-OCH2O-), 4.35 (q, 2H,
lactam-CH2-, J ) 22.8 Hz), 3.99, 3.88 (each s, 2 × 3H, 3′-
OCH3 + 4′-OCH3). MS (FAB, positive) m/z: 364 [M + H]+.
10-Benzo[1,3]dioxol-5-yl-7-methoxy-1,3-dioxa-8-aza-di-
cyclopenta[a,g]naphthalen-9-one (23). Compound 9 (29
mg, 0.08 mmol) was dissolved in a mixture of MeOH (3 mL)
and THF (6 mL). To the solution was added trimethylsilyl-
diazomethane (2 M in hexanes, 0.2 mL, 0.4 mmol). The
mixture was stirred for 18 h at room temperature and
concentrated in vacuo. The crude material was purified by
column chromatography on silica gel using CH2Cl2/MeOH (30:
1, v/v) to provide 23 (22 mg, 73%) as a yellow powder. Mp:
306-308 °C. 1H NMR (CDCl3) δ: 8.27 (s, 1H, H4), 7.67 (d,
1H, H5, J ) 8.4 Hz), 7.35 (d, 1H, H6, J ) 8.4 Hz), 6.83-6.92
(m, 3H, H2′ + H5′ + H6′), 6.07 (AB, 2H, 3′,4′-OCH2O-, ∆δ )
15.6 Hz, J ) 1.5 Hz), 5.96 (AB, 2H, 7,8-OCH2O-, ∆δ ) 4.2 Hz,
J ) 1.5 Hz), 3.15 (s, 3H, OCH3). MS (EI) m/z: 375 [M]+.
10-Benzo[1,3]dioxol-5-yl-8-hydroxy-1,3-dioxa-8-aza-di-
cyclopenta[a,g]naphthalene-7,9-dione (24). Hydroxyamine
hydrochloride (20.9 mg, 0.3 mmol) and triethylamine (0.04 mL,
0.3 mmol) were dissolved in EtOH (30 mL). After the mixture
was stirred for 10 min, anhydride 1 (109 mg, 0.3 mmol) was
added. The mixture was refluxed overnight and concentrated
in vacuo. The resulting product was purified by silica gel
column chromatography using CH2Cl2/acetone (2:1, v/v) to
afford 24 (16 mg, 15%) as a yellow powder. Mp: 255 °C (dec).
1H NMR (DMSO-d6) δ: 10.78 (s, 1H, OH), 8.40 (s, 1H, H4),
7.89 (d, 1H, H5, J ) 8.7 Hz), 7.54 (d, 1H, H6, J ) 8.7 Hz),
6.94 (s, 1H, H2′), 6.90 (d, 1H, H5′, J ) 7.8 Hz), 6.79 (d, 1H,
H6′, J ) 7.8 Hz), 6.08 (s, 2H, 3′,4′-OCH2O-), 5.96 (AB, 2H,
7,8-OCH2O-, ∆δ ) 5.7 Hz). MS (FAB, positive) m/z: 378 [M
+ H]+.
1H, H4), 7.69 (d, 1H, H5, J ) 8.7 Hz), 7.46 (s, 1H, NHAc),
7.38 (d, 1H, H6, J ) 8.7 Hz), 6.84-6.87 (m, 3H, H2′ + H5′ +
H6′), 6.06 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 16.5 Hz, J ) 1.5 Hz),
5.98 (AB, 2H, 7,8-OCH2O-, ∆δ ) 5.4 Hz, J ) 1.2 Hz), 2.17 (s,
3H, NHCOCH3). MS (EI) m/z: 418 [M]+.
N-(10-Benzo[1,3]dioxol-5-yl-7-oxo-7,9-dihydro-1,3-dioxa-
8-aza-dicyclopenta[a,g]naphthalen-8-yl)-acetamide (26),
N-(10-Benzo[1,3]dioxol-5-yl-9-oxo-7,9-dihydro-1,3-dioxa-
8-aza-dicyclopenta[a,g]naphthalen-8-yl)-acetamide (27),
and 11-Benzo[1,3]dioxol-5-yl-8,9-dihydro-1,3-dioxa-8,9-
diaza-cyclopenta[a]anthracene-7,10-dione (28). Com-
pound 25 (113 mg, 0.27 mmol) was dissolved in glacial acetic
acid (2 mL), the freshly activated zinc dust (196 mg) was added
thereto, then heated in an oil bath at 100 °C for 5 h. The
insoluble solid was filtered off, and the majority of acetic acid
was removed with a rotary evaporator. The obtained residue
was neutralized to pH 7 with 10% aqueous NaOH solution,
and then the mixture was extracted with CHCl3 (3 × 100 mL).
The extract was washed with water, dried over MgSO4, and
concentrated in vacuo. The residue was chromatographed on
silica gel using CH2Cl2/acetone (7:1 to 1:1, v/v) to afford a
lactam 26 (52 mg, 48%, pale yellow powder), a retro-lactam
27 (16 mg, 15%, yellow powder), and a hydrazino compound
28 (20 mg, 20%, yellow powder), respectively. 26. Mp: 274-
1
276 °C. H NMR (CDCl3) δ: 8.51 (s, 1H, NHAc), 8.34 (s, 1H,
H4), 7.64 (d, 1H, H5, J ) 8.7 Hz), 7.28 (d, 1H, H6, J ) 8.7
Hz), 6.78-6.89 (m, 3H, H2′ + H5′ + H6′), 6.06 (AB, 2H, 3′,4′-
OCH2O-, ∆δ ) 11.1 Hz, J ) 1.2 Hz), 5.94 (AB, 2H, 7,8-
OCH2O-, ∆δ ) 5.1 Hz, J ) 1.2 Hz), 4.54 (m, 2H, lactam-CH2-
), 2.14 (s, 3H, NHCOCH3). MS (EI) m/z: 404 [M]+. 27. Mp:
278-280 °C. 1H NMR (CDCl3) δ: 8.44 (s, 1H, NHAc), 7.79 (s,
1H, H4), 7.50 (d, 1H, H5, J ) 8.7 Hz), 7.30 (d, 1H, H6, J ) 8.7
Hz), 6.74-6.84 (m, 3H, H2′ + H5′ + H6′), 6.02 (AB, 2H, 3′,4′-
OCH2O-, ∆δ ) 18.3 Hz, J ) 0.9 Hz), 5.89 (AB, 2H, 7,8-
OCH2O-, ∆δ ) 1.2 Hz), 4.72 (s, 2H, lactam-CH2-), 1.99 (s,
3H, NHCOCH3). MS (EI) m/z: 404 [M]+. 28. Mp: 318-320
°C. 1H NMR (CDCl3) δ: 9.71(s, 1H, NH), 8.98 (s, 1H, NH), 7.93
(s, 1H, H4), 7.81 (d, 1H, H5, J ) 8.7 Hz), 7.43 (d, 1H, H6, J )
8.7 Hz), 6.93 (d, 1H, H5′, J ) 7.8 Hz), 6.86 (d, 1H, H2′, J ) 1.2
Hz), 6.82 (dd, 1H, H6′, J ) 1.2, 7.8 Hz), 6.11 (AB, 2H, 3′,4′-
OCH2O-, ∆δ ) 9.4 Hz, J ) 1.2 Hz), 5.97 (AB, 2H, 7,8-
OCH2O-, ∆δ ) 6.3 Hz, J ) 1.2 Hz). 13C NMR (DMSO-d6) δ:
159.84, 147.38, 147.01, 146.49, 141.94, 136.78, 133.32, 130.46,
130.18, 128.25, 125.61, 125.49, 124.29, 122.29, 121.29, 113.97,
111.28, 107.96, 102.00, 101.55. MS (EI) m/z: 376 [M]+.
10-Benzo[1,3]dioxol-5-yl-8-(3-hydroxy-propyl)-1,3-dioxa-
8-aza-dicyclopenta[a,g]naphthalene-7,9-dione (29). To a
stirred solution of anhydride 1 (109 mg, 0.3 mmol) in toluene
(40 mL) was added dropwise 3-amino-1-propanol (27 mg, 0.36
mmol) in toluene (5 mL) at 0 °C. The mixture was stirred at
room temperature for 1 h and then heated under a Dean-
Stark trap for 3 h. After water ceased to distill, the reaction
mixture was cooled, washed successively with water (2 × 50
mL), 5% aqueous NaHCO3 solution (2 × 50 mL), and water (2
× 50 mL), and then dried over MgSO4. The solvent was
removed in vacuo, and the resulting product was purified by
column chromatography on silica gel using CH2Cl2/acetone (3:1
to 1:1, v/v) to provide 29 (10 mg, 11%) as a pale yellow powder.
1
Mp: 150-152 °C. H NMR (CDCl3) δ: 8.27 (s, 1H, H4), 7.56
(d, 1H, H5, J ) 8.4 Hz), 7.26 (d, 1H, H6, J ) 8.4 Hz), 6.86-
6.91 (m, 3H, H2′ + H5′ + H6′), 6.04 (s, 2H, 3′,4′-OCH2O-),
5.97 (s, 2H, 7,8-OCH2O-), 3.69-3.76 (m, 4H, NCH2CH2CH2-
OH), 1.83 (m, 2H, NCH2CH2CH2OH).

544 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2
Yeo et al.
9-Benzo[1,3]dioxol-5-yl-naphtho[1,2-d][1,3]dioxole-7,8-
dicarboxylic Acid Dimethyl Ester (30). Compound 1 (108.6
mg, 0.3 mmol) was dissolved in a mixture of MeOH (4 mL)
and THF (8 mL). To the solution was added trimethylsilyl-
diazomethane (2 M in hexanes, 1.0 mL, 2.0 mmol). The
mixture was stirred for 12 h at room temperature and then
concentrated in vacuo. The residue was purified by chroma-
tography on silica gel using n-hexane/EtOAc (2:1, v/v) to afford
30 (67 mg, 55%) as a pale yellow powder. Mp: 157-159 °C.
1H NMR (CDCl3) δ: 8.53 (s, 1H, H4), 7.58 (d, 1H, H5, J ) 8.7
Hz), 7.27 (d, 1H, H6, J ) 8.7 Hz), 6.79-6.82 (m, 3H, H2′ +
H5′ + H6′), 6.03 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 10.2 Hz, J )
1.5 Hz), 5.89 (AB, 2H, 7,8-OCH2O-, ∆δ ) 7.2 Hz, J ) 1.5 Hz),
3.94, 3.66 (each s, 2 × 3H, 2 × OCH3). MS (EI) m/z: 408 [M]+.
0.9 Hz), 5.32 (s, 2H, lactone-CH2-). MS (FAB, positive) m/z:
365 [M + H]+.
9-Benzo[1,3]dioxol-5-yl-6-methoxy-naphtho[1,2-d][1,3]-
dioxole-7,8-dicarboxylic Acid Diethyl Ester (35). Com-
pound 33 (95 mg, 0.21 mmol) was dissolved in a mixture of
MeOH (3 mL) and THF (6 mL). To the solution was added
(trimethylsilyl)diazomethane (2 M in hexanes, 0.6 mL, 1.2
mmol). The mixture was stirred for 12 h at room temperature
and then concentrated in vacuo. The crude material was
purified by column chromatography on silica gel using CH2-
Cl2 to afford 35 (97 mg, 99%) as a yellow oil. 1H NMR (CDCl3)
δ: 7.86 (d, 1H, H5, J ) 8.7 Hz), 7.26 (d, 1H, H6, J ) 8.7 Hz),
6.75-6.82 (m, 3H, H2′ + H5′ + H6′), 6.00 (AB, 2H, 3′,4′-
OCH2O-, ∆δ ) 11.7 Hz, J ) 1.2 Hz), 5.87 (AB, 2H, 7,8-
OCH2O-, ∆δ ) 9.0 Hz, J ) 1.2 Hz), 4.39 (q, 2H, OCH2CH3, J
) 7.2 Hz), 4.06 (s, 3H, 4-OCH3), 4.03 (q, 2H, OCH2CH3, J )
7.2 Hz), 1.38, 1.04 (each t, 2 × 3H, 2 × OCH2CH3, J ) 7.2
Hz); MS (EI) m/z: 466 [M]+.
9-Benzo[1,3]dioxol-5-yl-naphtho[1,2-d][1,3]dioxole-7,8-
dicarboxylic Acid Diamide (36). Compound 9 (72 mg, 0.2
mmol) was added to a mixture of concentrated ammonium
hydroxide (2 mL) and THF (2 mL). The suspension was stirred
at 40 °C for 72 h and concentrated in vacuo. Silica gel column
chromatography of the crude product with CH2Cl2/MeOH (4:1
to 1:1, v/v) provided 36 (23 mg, 30%) as a pale yellow powder.
Mp: 298 °C (dec). 1H NMR (CD3OD) δ: 8.18 (s, 1H, H4), 7.55
(d, 1H, H5, J ) 8.4 Hz), 7.21 (d, 1H, H6, J ) 8.4 Hz), 6.72-
6.86 (m, 3H, H2′ + H5′ + H6′), 5.93 (AB, 2H, 3′,4′-OCH2O-,
∆δ ) 13.2 Hz, J ) 0.9 Hz), 5.80 (AB, 2H, 7,8-OCH2O-, ∆δ )
7.2 Hz, J ) 0.9 Hz). MS (FAB, positive) m/z: 402 [M + H +
Na]+.
10-Benzo[1,3]dioxol-5-yl-5-chloro-9H-furo[3′,4′:6,7]naph-
tho[1,2-d][1,3]dioxol-7-one (37). A stirred solution of 2 (104
mg, 0.3 mmol), N-chlorosuccinimide (80 mg, 0.6 mmol), and
concentrated H2SO4 (10 µL) in THF (5 mL) was heated to
reflux for 24 h and then diluted with CHCl3 (50 mL). The
reaction mixture was washed with 10% aqueous Na2S2O3
solution (50 mL) and water (2 × 50 mL), dried over MgSO4,
and concentrated in vacuo. The product was purified by column
chromatography on silica gel eluting with CHCl3 to afford 37
(56 mg, 49%) as a brown solid. Mp: 267 °C (dec). 1H NMR
(CDCl3) δ: 8.91 (s, 1H, H4), 7.47 (s, 1H, H6), 6.76-6.91 (m,
3H, H2′ + H5′ + H6′), 6.08 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 8.7
Hz, J ) 1.5 Hz), 5.97 (AB, 2H, 7,8-OCH2O-, ∆δ ) 8.7 Hz, J )
1.5 Hz), 5.22 (q, 2H, lactone-CH2-, J ) 8.7 Hz). MS (EI) m/z:
384 [M + 2]+, 382 [M]+.
10-Benzo[1,3]dioxol-5-yl-5-bromo-9H-furo[3′,4′:6,7]naph-
tho[1,2-d][1,3]dioxol-7-one (38). To a solution of 2 (15.4 mg,
0.044 mmol) in THF (1 mL) were added N-bromosuccinimide
(10.7 mg, 0.06 mmol) and concentrated H2SO4 (5 µL). The
solution was stirred at room temperature for 20 h and then
diluted with EtOAc (30 mL). The same workup and purifica-
tion procedure as described for the isolation of 37 gave product
38 (12 mg, 64%) as a pale yellow powder. Mp: 256 °C (dec).
1H NMR (CDCl3) δ: 8.89 (s, 1H, H4), 7.65 (s, 1H, H6), 6.76-
6.91 (m, 3H, H2′ + H5′ + H6′), 6.08 (AB, 2H, 3′,4′-OCH2O-,
∆δ ) 8.7 Hz, J ) 1.5 Hz), 5.97 (AB, 2H, 7,8-OCH2O-, ∆δ )
7.8 Hz, J ) 1.5 Hz), 5.22 (q, 2H, lactone-CH2-, J ) 8.4 Hz).
MS (EI) m/z: 428 [M + 2]+, 426 [M]+.
9-Benzo[1,3]dioxol-5-yl-naphtho[1,2-d][1,3]dioxole-7,8-
dicarboxylic Acid 8-Methyl Ester (31). Compound 30 (20
mg, 0.05 mmol) was refluxed with a 1 M solution of KOH in
MeOH (10 mL) for 2 h. The solution was cooled, and the solvent
was removed under reduced pressure. The remaining solid was
dissolved in water (10 mL) and acidified to pH 1-2 with 10%
aqueous HCl solution. The precipitate was collected by filtra-
tion, washed with water, and dried. The product was purified
by column chromatography on silica gel using CH2Cl2/MeOH
(20:1 to 10:1, v/v) to give 31 (11 mg, 56%) as a pale yellow
powder. Mp: 273-275 °C. 1H NMR (CDCl3) δ: 8.54 (s, 1H,
H4), 7.49 (d, 1H, H5, J ) 8.1 Hz), 7.20 (d, 1H, H6, J ) 8.1
Hz), 6.76-6.82 (m, 3H, H2′ + H5′ + H6′), 6.03 (AB, 2H, 3′,4′-
OCH2O-, ∆δ ) 11.1 Hz), 5.88 (AB, 2H, 7,8-OCH2O-, ∆δ )
7.2 Hz), 3.62 (s, 3H, OCH3). MS (FAB, positive) m/z: 395 [M
+ H]+.
9-Benzo[1,3]dioxol-5-yl-naphtho[1,2-d][1,3]dioxole-7,8-
dicarboxylic Acid (32). Compound 30 (20 mg, 0.05 mmol)
was refluxed with 1 M solution of KOH in MeOH (10 mL) for
24 h. Completion of the reaction, followed by a workup as
described for the isolation of 31, gave a residue that was
purified by silica gel column chromatography. Elution with
CH2Cl2/MeOH (2:1, v/v) as eluent yielded 32 (12 mg, 63%) as
a yellow powder. Mp: 253 °C (dec). 1H NMR (DMSO-d6) δ:
8.25 (s, 1H, H4), 7.53 (d, 1H, H5, J ) 8.7 Hz), 7.24 (d, 1H, H6,
J ) 8.7 Hz), 6.72-6.82 (m, 3H, H2′ + H5′ + H6′), 5.99 (AB,
2H, 3′,4′-OCH2O-, ∆δ ) 18.9 Hz), 5.81 (AB, 2H, 7,8-OCH2O-,
∆δ ) 6.0 Hz). MS (FAB, positive) m/z: 381 [M + H]+.
9-Benzo[1,3]dioxol-5-yl-6-hydroxy-naphtho[1,2-d][1,3]-
dioxole-7,8-dicarboxylic Acid Diethyl Ester (33). Hy-
droxyacetal 1a (3.44 g, 10 mmol), diethyl acetylenedicarbox-
ylate (1.70 g, 10 mmol), CH2Cl2 (4.5 mL), and glacial acetic
acid (3 mL) were heated at 140 °C for 24 h. The cooled mixture
was diluted with CH2Cl2 (100 mL), washed with 5% NaHCO3
solution (3 × 100 mL), dried over MgSO4, and concentrated
under vacuum. The residue was chromatographed over silica
gel using n-hexane/EtOAc/triethylamine (3:1:0.1, v/v/v), fol-
lowed by crystallization from ether to afford 33 (741 mg, 16%)
as a white powder. Mp: 192-194 °C. 1H NMR (CDCl3) δ: 12.76
(s, 1H, 4OH), 8.15 (d, 1H, H5, J ) 8.7 Hz), 7.21 (d, 1H, H6, J
) 8.7 Hz), 6.77-6.81 (m, 3H, H2′ + H5′ + H6′), 6.01 (AB, 2H,
3′,4′-OCH2O-, ∆δ ) 13.5 Hz, J ) 1.5 Hz), 5.86 (AB, 2H, 7,8-
OCH2O-, ∆δ ) 5.7 Hz, J ) 1.5 Hz), 4.41, 4.01 (each q, 2 ×
2H, 2 × OCH2CH3, J ) 7.2 Hz), 1.37, 1.06 (each t, 2 × 3H, 2
× OCH2CH3, J ) 7.2 Hz). MS (EI) m/z: 452 [M]+.
10-Benzo[1,3]dioxol-5-yl-5-iodo-9H-furo[3′,4′:6,7]naph-
tho[1,2-d][1,3]dioxol-7-one (39). To a solution of 2 (14 mg,
0.04 mmol) in acetonitrile (1 mL) were added N-iodosuccin-
imide (13.6 mg, 0.06 mmol) and concentrated H2SO4 (5 µL).
The mixture was stirred at room temperature for 36 h,
concentrated at reduced pressure, and diluted with ether (30
mL). The same workup and purification procedure as described
for the isolation of 37 afforded product 39 (10.5 mg, 55%) as a
yellow powder. Mp: 255 °C (dec). 1H NMR (CDCl3) δ: 8.78 (s,
1H, H4), 7.93 (s, 1H, H6), 6.75-6.90 (m, 3H, H2′ + H5′ + H6′),
6.08 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 8.7 Hz, J ) 1.5 Hz), 5.97
(AB, 2H, 7,8-OCH2O-, ∆δ ) 7.8 Hz, J ) 1.5 Hz), 5.23 (q, 2H,
lactone-CH2-, J ) 8.7 Hz). MS (EI) m/z: 474 [M]+.
10-Benzo[1,3]dioxol-5-yl-6-hydroxy-7H-furo[3′,4′:6,7]-
naphtho[1,2-d][1,3]dioxol-9-one (34). A solution of 33 (45.2
mg, 0.1 mmol) in THF (1 mL) was added dropwise to a
suspension of lithium aluminum hydride (7.6 mg, 0.2 mmol)
in THF (1 mL) at 0 °C. The mixture was stirred at room
temperature for 2 h, quenched with aqueous saturated Na2-
SO4 solution, and extracted with CHCl3 (2 × 30 mL). After
evaporation of organic solvent, the residue was purified by
column chromatography on silica gel using CH2Cl2/MeOH (20:
1, v/v) to give 34 (36 mg, 99%) as a yellow powder. Mp: 257
1
°C (dec). H NMR (DMSO-d6) δ: 10.67 (s, 1H, 4OH), 7.94 (d,
1H, H5, J ) 9.0 Hz), 7.44 (d, 1H, H6, J ) 9.0 Hz), 6.84 (d, 1H,
H5′, J ) 8.1 Hz), 6.79 (d, 1H, H2′, J ) 1.5 Hz), 6.66 (dd, 1H,
H6′, J ) 1.5, 8.1 Hz), 6.04 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 6.0
Hz, J ) 0.6 Hz), 5.88 (AB, 2H, 7,8-OCH2O-, ∆δ ) 6.3 Hz, J )
10-Benzo[1,3]dioxol-5-yl-5-bromo-8,9-dihydro-1,3-dioxa-
8-aza-dicyclopenta[a,g]naphthalen-7-one (40). To a solu-

Synthesis and Antiviral Activity of Helioxanthin Analogues
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 2 545
tion of 18 (14 mg, 0.04 mmol) in THF (5 mL) were added
N-bromosuccinimide (11 mg, 0.06 mmol) and concentrated H2-
SO4 (10 µL). The solution was stirred at room temperature
for 24 h and then diluted with EtOAc (30 mL). Completion of
the reaction, followed by the workup as described for the
isolation of 37, gave a residue that was purified by silica gel
column chromatography. Elution with CH2Cl2/acetone (10:1
to 5:1, v/v) as eluent yielded 40 (12 mg, 70%) as a pale brown
solid. Mp: 285 °C (dec). 1H NMR (CDCl3) δ: 8.81 (s, 1H, H4),
7.63 (s, 1H, H6), 6.77-6.91 (m, 3H, H2′ + H5′ + H6′), 6.07
(AB, 2H, 3′,4′-OCH2O-, ∆δ ) 7.5 Hz, J ) 1.2 Hz), 5.93 (AB,
2H, 7,8-OCH2O-, ∆δ ) 6.0 Hz, J ) 1.2 Hz), 4.34 (m, 2H,
lactam-CH2-). MS (FAB, positive) m/z: 428 [M + 2]+, 426
[M]+.
(s, 2H, 2-CH2OH). MS (FAB, positive) m/z: 425 [M + H + 2]+,
423 [M + H]+.
9-Benzo[1,3]dioxol-5-yl-5-bromo-8-hydroxymethyl-naph-
tho[1,2-d][1,3]dioxole-7-carboxylic Acid Monosodium Salt
(45). Conversion of 38 (65 mg, 0.15 mmol) to 45 was ac-
complished using a procedure similar to that described for 44.
The residue obtained was purified by silica gel column chro-
matography using CH2Cl2/MeOH (3:1, v/v) to provide 45 (64
mg, 91%) as a yellow powder. Mp: 205 °C (dec), 1H NMR
(DMSO-d6) δ: 8.29 (s, 1H, H4), 7.69 (s, 1H, H6), 6.88 (d, 1H,
H5′, J ) 7.8 Hz), 6.72 (d, 1H, H2′, J ) 1.5 Hz), 6.62 (dd, 1H,
H6′, J ) 1.5, 7.8 Hz), 6.05 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 18.6
Hz), 5.81 (AB, 2H, 7,8-OCH2O-, ∆δ ) 8.4 Hz), 4.13 (s, 2H,
2-CH2OH). MS (FAB, positive) m/z: 469 [M + H + 2]+, 467
[M + H]+.
9-Benzo[1,3]dioxol-5-yl-8-hydroxymethyl-5-iodo-naph-
tho[1,2-d][1,3]dioxole-7-carboxylic Acid Monosodium Salt
(46). Conversion of 39 (64 mg, 0.135 mmol) to 46 was
accomplished using a procedure similar to that described for
44. The residue obtained was purified by silica gel column
chromatography using CH2Cl2/MeOH (3:1, v/v) to give 46 (62
mg, 89%) as a pale yellow powder. Mp: 212 °C (dec). 1H NMR
(DMSO-d6) δ: 8.27 (s, 1H, H4), 7.86 (s, 1H, H6), 6.88 (d, 1H,
H5′, J ) 7.8 Hz), 6.71 (d, 1H, H2′, J ) 1.2 Hz), 6.62 (dd, 1H,
H6′, J ) 1.2, 7.8 Hz), 6.04 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 18.3
Hz), 5.79 (AB, 2H, 7,8-OCH2O-, ∆δ ) 8.4 Hz), 4.13 (s, 2H,
2-CH2OH). MS (FAB, positive) m/z: 515 [M + H]+.
11-Benzo[1,3]dioxol-5-yl-5-chloro-8,9-dihydro-1,3-dioxa-
8,9-diaza-cyclopenta[a]anthracene-7,10-dione (41). To a
solution of 28 (39.5 mg, 0.11 mmol) in THF (1 mL) were added
N-chlorosuccinimide (28 mg, 0.21 mmol) and concentrated H2-
SO4 (10 µL). The solution was stirred at room temperature
for 48 h and then diluted with EtOAc (30 mL). Completion of
the reaction, followed by the workup as described for the
isolation of 37, gave a residue that was purified by silica gel
column chromatography. Elution with CH2Cl2/acetone (10:1,
v/v) as eluent afforded 41 (15.6 mg, 35%) as a yellow powder.
1
Mp: 316 °C (dec). H NMR (DMSO-d6) δ: 12.58 (s, 1H, NH),
9.10 (s, 1H, NH), 8.01 (s, 1H, H4), 7.73 (s, 1H, H6), 7.04 (d,
1H, H5′, J ) 7.8 Hz), 7.03 (d, 1H, H2′, J ) 1.5 Hz), 6.86 (dd,
1H, H6′, J ) 1.5, 7.8 Hz), 6.14 (AB, 2H, 3′,4′-OCH2O-, ∆δ )
23.1 Hz), 6.05 (AB, 2H, 7,8-OCH2O-, ∆δ ) 12.2 Hz).13C NMR
(DMSO-d6) δ: 159.09, 147.12, 146.63, 145.58, 141.48, 136.05,
134.10, 129.17, 126.21, 125.64, 125.44, 123.82, 123.40, 122.84,
121.12, 114.43, 110.75, 107.58, 102.29, 101.17. MS (EI) m/z:
396 [M - NH2 + 2]+, 394 [M - NH2]+.
In Vitro Antiviral Assays. The antiviral assays for HBV,18
HSV-1,20 HSV-2,20 EBV,21 CMV,22 and HIV23 were performed
according to the previously described procedures. Anti-HCV
activities were tested in the Huh-Luc/neo cell line, which was
kindly given to us by Dr. Bartenschlager of University of
Heidelberg, Germany. Cells were seeded into a 48-well plate
and grown until confluent. Varying concentrations of drug
were added into the media (DMEM, 10% dFBS), and the cells
were incubated for 3 days. At the end of the 3-day treatment,
the medium was removed, and 50 µL of Passive lysis buffer
(Promega) was added. The cell lysate was then shaken at room
temperature for 15 min. An aliquot of 30 µL/well cell lysate
was transferred to a 96-well plate, 100 µL/well of luciferase
activity assay substrate was added to each well, and the
activity on the plate was immediately read with a luminometer
(Amersham).
11-Benzo[1,3]dioxol-5-yl-5-bromo-8,9-dihydro-1,3-dioxa-
8,9-diaza-cyclopenta[a]anthracene-7,10-dione (42). To a
solution of 28 (13 mg, 0.035 mmol) in THF (1 mL) were added
N-bromosuccinimide (9.4 mg, 0.053 mmol) and concentrated
H2SO4 (5 µL). The solution was stirred at room temperature
for 48 h and then diluted with EtOAc (20 mL). The same
workup and purification procedure as described for the isola-
tion of 41 gave product 42 (9 mg, 57%) as a yellow powder.
1
Mp: 310 °C (dec). H NMR (DMSO-d6) δ: 12.54 (s, 1H, NH),
9.04 (s, 1H, NH), 8.13 (s, 1H, H4), 7.69 (s, 1H, H6), 7.00 (d,
1H, H5′, J ) 7.8 Hz), 6.99 (d, 1H, H2′, J ) 1.5 Hz), 6.82 (dd,
1H, H6′, J ) 1.5, 7.8 Hz), 6.11 (AB, 2H, 3′,4′-OCH2O-, ∆δ )
17.4 Hz, J ) 0.6 Hz), 6.02 (AB, 2H, 7,8-OCH2O-, ∆δ ) 9.3
Hz, J ) 0.9 Hz). MS (FAB, positive) m/z: 441 [M - NH2 + H
+ 2]+, 439 [M - NH2 + H]+.
Cell Cytotoxicity Assays. The cytotoxicity of test com-
pounds was determined on both MT-223 and CEM24 cell lines
according to the previously reported procedures.
Acknowledgment. The corresponding author is a
fellow of the National Foundation for Cancer Research.
Part of this work was supported by the National
Foundation for Cancer Research.
11-Benzo[1,3]dioxol-5-yl-5-iodo-8,9-dihydro-1,3-dioxa-
8,9-diaza-cyclopenta[a]anthracene-7,10-dione (43). To a
solution of 28 (13.3 mg, 0.035 mmol) in acetonitrile (1 mL) were
added N-iodosuccinimide (11.9 mg, 0.053 mmol) and concen-
trated H2SO4 (5 µL). The solution was stirred at room tem-
perature for 48 h and diluted with EtOAc (20 mL). The same
workup and purification procedure as described for the isola-
tion of 41 yielded 43 (9 mg, 51%) as a brown solid. Mp: 300
°C (dec). 1H NMR (DMSO-d6) δ: 12.59 (s, 1H, NH), 9.10 (s,
1H, NH), 8.38 (s, 1H, H4), 7.79 (s, 1H, H6), 7.10 (d, 1H, H5′,
J ) 7.8 Hz), 7.09 (d, 1H, H2′, J ) 1.7 Hz), 6.92 (dd, 1H, H6′,
J ) 1.7, 7.8 Hz), 6.22 (AB, 2H, 3′,4′-OCH2O-, ∆δ ) 22.8 Hz,
J ) 0.7 Hz), 6.10 (AB, 2H, 7,8-OCH2O-, ∆δ ) 13.5 Hz, J )
0.9 Hz). MS (EI): m/z 486 [M - NH2]+.
9-Benzo[1,3]dioxol-5-yl-5-chloro-8-hydroxymethyl-naph-
tho[1,2-d][1,3]dioxole-7-carboxylic Acid Monosodium Salt
(44). Aqueous NaOH solution (1.56 mL, 1 N) was added to a
solution of 37 (57 mg, 0.15 mmol) in MeOH (25 mL). The
mixture was stirred at 70 °C for 1 h. The solvent was
evaporated to give crude product, which was purified by silica
gel column chromatography using CH2Cl2/MeOH (3:1, v/v) to
afford 44 (55 mg, 87%) as a white powder. Mp: 220 °C (dec).
1H NMR (DMSO-d6) δ: 8.39 (s, 1H, H4), 7.54 (s, 1H, H6), 6.89
(d, 1H, H5′, J ) 8.7 Hz), 6.73 (d, 1H, H2′, J ) 1.5 Hz), 6.63
(dd, 1H, H6′, J ) 1.5, 8.7 Hz), 6.05 (AB, 2H, 3′,4′-OCH2O-,
∆δ ) 18.9 Hz), 5.81 (AB, 2H, 7,8-OCH2O-, ∆δ ) 8.1 Hz), 4.12
Supporting Information Available: HPLC chromato-
grams for helioxanthine, 12, 18, 28, and 42. This information
is available free of charge via the Internet at http://
pubs.acs.org.
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