Synthesis and antifungal activity of coumarins and angular furanocoumarins

Article abstract of DOI:10.1016/S0968-0896(99)00138-8

Angelicin, a naturally occurring furanocoumarin, that showed antifungal activity, was considered as a lead structure for a group of synthetic coumarins. Antifungal activities of the synthesized coumarins and angelicin derivatives were reported against Can

Full text of DOI:10.1016/S0968-0896(99)00138-8

Bioorganic & Medicinal Chemistry 7 (1999) 1933±1940
Synthesis and Antifungal Activity of Coumarins and Angular
Furanocoumarins
Soroush Sardari, a,* Yoki Mori, b Kiyoshi Horita, b Ronald G. Micetich, a,c
Sansei Nishibe b and Mohsen Daneshtalab a
aFaculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, T6G 2N8, Canada
bFaculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Japan 061-02
cSynPhar Laboratories Inc., No. 24, 4290-91A Street, Edmonton, Alberta, T6E 5V2, Canada
Received 4 January 1999; accepted 29 March 1999
AbstractÐAngelicin, a naturally occurring furanocoumarin, that showed antifungal activity, was considered as a lead structure for
a group of synthetic coumarins. Antifungal activities of the synthesized coumarins and angelicin derivatives were reported against
Candida albicans, Cryptococcus neoformans, Saccharomyces cerevisiae and Aspergillus niger. Human cell line cytotoxicity of several
coumarins was evaluated against KB cells. Angelicin and several potent antifungals showed to be non-toxic in this assay. # 1999
Elsevier Science Ltd. All rights reserved.
Introduction
diverse molecules. There are many antifungal com-
pounds of plant origin. These compounds may be con-
stitutive, which present in the plant tissue most of the
times, or induced, that are produced in plants only in
special circumstances such as infection. Coumarins can
be classi®ed in the latter group.3 According to our pre-
vious study, angelicin (1a) was isolated as the bioactive
component of Diplotaenia damavandica, a rare Iranian
native plant.4 This coumarin skeleton was considered as
the lead structure in the present study. To improve the
potency and antifungal pro®le of the lead structure,
di€erent modi®cations were considered. The antifungal
activities of the synthesized coumarins and angelicin
derivatives are discussed.
With the employment of modern chemotherapeutic
modalities in the 1960s, susceptible hosts were created
for several opportunists and with the advent of the
AIDS era in the 1980s, a broad range of opportunistic
pathogenic fungi are making their appearance in the
medical scene. Ranging from a 75% increase in small
hospitals to over 400% increase in some large care cen-
tres, Candida is now ranked as the third most common
causative agent of nosocomial blood stream infections
in most hospitals.1,2
The development of azoles has revolutionized the treat-
ment of many fungal infections, but still treatment of
many of them necessitates application of the highly
toxic drug, amphotericin B or a combination of drugs.
Emergence of new resistant species of fungi in addition
to the poor safety and pharmacokinetics pro®le, chal-
lenges the clinicians in their way to handle the fungal
infections.
Chemistry
The structures of several known compounds used in this
study are shown in Figure 1. Synthetic procedures for
the target compounds are summarized in Schemes 1 and
2. Compounds 1a, 6b and 7a,b were synthesized
according to Zubõa et al.5 To synthesize di€erent cou-
marins and furanocoumarins, umbellifreone (6a) and
esculin (9a) were used as the starting material. The 8-
substituted series of dihydroxycoumarins were prepared
through Claisen rearrangement of compound 9e.
To produce new generations of antifungal compounds,
natural products can be considered a rich source of
Key words: Coumarins; fungi; antifungal; cytotoxicity.
* Corresponding author at Department of Chemistry, 110 Science
Place, University of Saskatchewan, Saskatoon, SK S7N 5C9, Canada.
Tel.: +1-306-244-7583; fax: +1-306-966-4730; e-mail: ssardari@
hotmail.com
With a few modi®cations, compounds 11a and 11d were
prepared mainly by the procedure mentioned before.6,7
0968-0896/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(99)00138-8

1934
S. Sardari et al. / Bioorg. Med. Chem. 7 (1999) 1933±1940
Figure 1. Structure of some coumarins and other simple building blocks used in this study.
Scheme 1. Synthesis of compounds 1a, 7a,b and 8a±c. (a) I2, KI/H2O; (b) CHꢀCCOOEt, Cu2O/DMF, 110ꢁC; (c) NaOH/H2O; (d) Cu/quinoline; (e)
I. SOCl2; II. H2NR/THF, DMAP.
One of the major modi®cations applied to these sets of
reactions was the replacement of PPA (polyphosphoric
acid) with p-toluenesulfonic acid, which resulted in a
better yield and less by-products. Compound 11c, which
is reported for the ®rst time, has an interesting synthetic
procedure. The mechanism leading to the production of
11c could be a Fries-type rearrangement of the benzylic
group from position 6 to position 5.8 Our observation
suggests that time of the reaction works in favor of 11c
and against 11b, the longer the reaction, the larger the
yield of 11c. Compound 11e was a novel product of the
reaction `n' in Scheme 2. The reaction also led to
compound 11d as expected. The relative ratio of 11d:11e
was about 2:1.
furanocoumarins. Other compounds with phenolic hy-
droxyl group (4 and 6a), do not show promising activity
either.
Among the alkylamines (5a±c), there are some active
molecules. In the alkylamine series, hexadecylamine (5c)
possesses a very strong antifungal activity, especially
against Cryptococcus and Saccharomyces. It is possible
to mention that by increasing the chain length, the
activity in this group increases.
The carbonyl group was used to link di€erent moieties
to the furanocoumarin nucleus. Although the carboxyl
derivative 7a is not considered active, the ethyl ester
derivative 7b gained some activity. In simple fur-
anocoumarin derivatives, 1a and 7a±b, 1a shows con-
siderable activity. The activity found in 7b is extended
to the amide derivative 8a and is improved in 8b, but
stopped or reversed in 8c. Compounds 9a±g are 6,7 di-
substituted coumarins, which exhibit weak or no activ-
ity. In the case of esculin (9a), a naturally occurring
coumarin glycoside, protecting the phenolic hydroxyl to
make 9b does not improve the biological activity, and so
Results
The antifungal activity of di€erent coumarin derivatives
is shown in Table 1. Di€erent angular furanocoumarins
1a±d exhibit similar antifungal spectrum and potency.
The activity of individual segments (i.e. coumarin 2 and
benzofuran 3) are much less compared with the original

S. Sardari et al. / Bioorg. Med. Chem. 7 (1999) 1933±1940
1935
Scheme 2. Synthesis of compounds 9a±g, 10a±e, and 11a±i. (a) allyl bromide, K2CO3/DMF; (b) acetic anhydride, DMAP, NEt3/CH2Cl2; (c) H2SO4/
H2O; (d) benzyl bromide, K2CO3, NaI/DMF; (e) NaIO4, OsO4/THF, MeOH, H2O; (f) NMO, OsO4/THF, MeOH, H2O; (g) 215±225ꢁC, 1 mm Hg;
(h) H2, Pd±C/MeOH; (i) NMO, OsO4/acetone, EtOAc, H2O; (j) 10-camphorsulfonic acid/MeOH; (k) p-toluenesulfonic acid/C6H6 (total yield 82%);
(l) NaIO4/THF, MeOH, H2O; (m) H2, Pd(OH)2/EtOAc, MeOH; (n) (CH3)2SO4, K2CO3/MeOH (total yield 53%); (o) H2, Pd±C/EtOAc, MeOH.
does the protection of sugar hydroxyls by the acetyl
moiety (9c). The more polar derivative 9g is reasonably
more potent than 9e and 9f.
cytotoxicity to a great extent in 8b. Angelicin itself is
almost non-toxic to KB cells. Compound 11c with a free
hydroxyl group is also non-toxic.
In the series of 6,7,8 tri-substituted coumarin deriva-
tives, 10a±10e, compound 10b has the strongest and
broadest spectrum of activity. This compound is also
the only one in this group with a free 6-OH, which
probably contributes to its potency. Substitution of an
alkyl group at C-8 position of 10b results in the increase
of antifungal properties compared to 4. The 8-sub-
stituted derivative 10e is more active than the more
polar derivative, 10c.
Discussion
Coumarins have a variety of bioactivities including:
anticoagulant, estrogenic, dermal photosensitizing,
antimicrobial, vasodilator, molluscacidal, anthelmintic,
sedative and hypnotic, analgesic and hypothermic
activity.9 These compounds may also be considered as a
defense tool for plants against fungi.10 Although cou-
marin inhibits the germination of spores of Aspergillus
niger, Penicillium glaucum, and Rhizopus nigricans,
novobiocin and other 4-hydroxycoumarins are generally
ine€ective against fungi.11,12
Furanocoumarins with a substitution on position 6 were
also examined. In this group, 11f and 11i show the
strongest activity against Candida and Cryptococcus.
Among the compounds with a substituent replacing
hydrogen in 6-OH of 11a (i.e. 11b, 11d, 11f, 11g and 11h)
the strongest activity against Cryptococcus was exhibited
by 11f, which is in the range of 11a with the intact 6-OH.
A similar comparison among the 5-substituted com-
pounds in this series, 11c and 11i indicates that compound
11i with protected 6-OH is a stronger antifungal.
To determine the best skeleton for further modi®cation,
the antifungal activity of angelicin was compared with
1b±d. As shown in Table 1, there is not a big di€erence
among these compounds in terms of MIC and the
spectrum of activity. Angelicin (1a) and 1b, however,
show activity against Cryptococcus. Since angelicin is
exhibiting more activity against Candida than 1b, it was
selected for further molecular optimization.
The KB cell line toxicity of several compounds is
shown in Table 2. As can be seen, compound 5b has a
strong toxicity. On the other hand, the integration of
this moiety with the coumarin nucleus has reduced its
In a study by Dini et al.,13 several coumarins were isolated
and puri®ed from Cyperus incompletus. The antifungal

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S. Sardari et al. / Bioorg. Med. Chem. 7 (1999) 1933±1940
Table 1. In vitro antifungal activity of the coumarins and other compounds, expressed as MIC values (mg/mL): medium, RPMI 1640, inoculum
5Â104 CFU/mL, temperature 35ꢁC, incubation period 24±48 h
Compound
Candida albicans
ATCC 14053
Cryptococcus neoformans
KF-33
Saccharomyces cerevisiae
PLM 454
Aspergillus niger
PLM 1140
1a
1b
1c
1d
2
3
62.5
250
250
250
62.5
>250
>250
500
125
62.5
62.5
125
1000
500
62.5
62.5
62.5
62.5
Nta
Nt
>250
>1000
1000
500
4
5a
5b
5c
6a
7a
7b
8a
8b
8c
9a
9b
9c
9d
9e
>1000
125
<7.8
15.6
1000
>2000
1000
250
1000
62.5
<7.8
<1.9
500
2000
250
125
31.3
31.3
>1000
>1000
>1000
250
>1000
500
250
500
125
1000
125
125
250
125
250
500
1000
250
<7.8
<1.9
Nt
Nt
Nt
62.5
62.5
125
>1000
>1000
>1000
250
>1000
Nt
250
1000
62.5
1000
250
250
500
Nt
>500
15.6
7.8
500
2000
1000
>250
125
250
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
Nt
250
>250
>1000
>1000
>1000
>1000
>1000
1000
>500
>1000
250
9f
9g
10a
10b
10c
10e
11a
11b
11c
11d
11e
11f
11g
11h
11i
>1000
1000
250
500
500
500
>500
250
500
>500
62.5
500
Nt
500
250
250
250
125
62.5
500
250
Nt
Nt
Nt
500
Intraconazole
Fluconazole
51.2
12.8
0.8
25.6
0.8
6.4
Nt
10.0
a
Nt, not tested.
9b is indicative of this fact. It seems that as far as the
antifungal activity is concerned, a free 6-OH is essential,
while a protected 7-OH may or may not11 provide more
bioactivity.
Table 2. In vitro cyctotoxicity of selected compounds on KB cell line,
expressed as TD50 (mg/mL)
Compound
TD50
1a
5b
11c
8b
89.6
5.5
82.5
51.5
Antifungal activity of 6,7,8-tri-substituted coumarin
derivatives
Adriamycin
0.01
Substitution of position 8 of esculetin (4), which resul-
ted in compound 10b, has increased the antifungal
activity tremendously. Protection of 6-OH to yield 10a
is reducing the activity as it happened in the 6,7-di-sub-
stituted coumarins. Replacing position 8 with more
polar substituent like in 10c diminishes the activity,
while transforming the 8-substituent to a more non-
polar group like in 10e, regenerates the activity to a
great extent.
tests showed that an aromatic hydroxyl group and/or an
extra oxygenated functional group (ether or ester) in 6
and 7 positions of coumarin were necessary for the
activity. Alkylated derivatives of 7-hydroxycoumarin
may show both antifungal and antibacterial properties.
Antifungal activity of 6,7-di-substituted coumarin
derivatives
Antifungal activity of furanocoumarins carrying a long
chain hydrocarbon group at 20 position
Comparing the activities of 9d with 9e, and 10a with
10b, reveals that the compounds with free 6-OH have a
better activity. However, the same phenomenon is not
observed for 7-OH. The lack of activity in both 9a and
In the homologous series in which simple long chain
hydrocarbons are connected to the furanocoumarin
skeleton of angelicin, the activities are generally better

S. Sardari et al. / Bioorg. Med. Chem. 7 (1999) 1933±1940
1937
than other furanocoumarins. The long chain alkyla-
mines 5b and 5c themselves are potent antifungals. It
could be noticed that antifungal activities correlate
relatively well with the lipophilicity of these molecules.
spectra were recorded on either a JEOL JNM-GX270 or
Brucker AM-300 spectrometer, using tetramethylsilane
as an internal standard. High-resolution mass spectra
were determined on an AEI MS 50 spectrometer equip-
ped with a Mass Spectrometry Services MASPEC data
system. IR data were recorded on a NICOLET Magna
750 FT IR instrument equipped with a NICPLAN
microscope attachment. Silica gel column chromato-
graphy was carried out using Merck 7734 (60±200 mesh)
silica gel. The solid compounds synthesized here are
referred to as powder (amorphous), unless otherwise
mentioned to be crystalline.
Antifungal activity of 6-substituted furanocoumarins
In the furanocoumarin series, a simple comparison
among compounds 11a, 11b, 11d, 11g and 11h indicates
that the free hydroxyl group in the position 6 is impor-
tant for antifungal activity. Di€erent alkyl and aryl
groups attached to the oxygen at location 6 reduce the
activity to almost the same extent. Acetylation of the 6-
hydroxyl caused retention of activity in 11f compared to
11a. However, the same reaction on 11c yielded 11i with
improved overall activity.
Compounds 1b±d
These compounds were kindly provided by Dr T. Har-
ayama, whose synthesis was reported previously.16
Addition of a methoxyl group to position 5 imposed a
negative e€ect on the bioactivity in 11e compared to
11d. Providing position 5 with a benzyl moiety
decreased the activity. The generalization to these
observations could be that protection of 6-OH by
groups that change the electronic contribution of oxy-
gen 6 to the ring or changing polarity of the functional
groups to a favored pattern has an improving e€ect on
the antifungal activity of this group.
2H-Furo[2,3-h]-1-benzopyran-2-one-8-carboxylic acid
(7a). Compound 7b (50 mg, 0.2 mmol), was mixed with
5 mL of aqueous NaOH (20%) and the mixture was
re¯uxed for 24 h. After cooling and acidi®cation with
concd HCl, the mixture was vigorously stirred for 1 h
and the precipitate collected by ®ltration and washed
with CHCl3, EtOAc, MeOH, and water (20 mL each) to
a€ord 7a (40 mg, 0.17 mmol, 87%) as a white amor-
phous solid, mp >305ꢁC (decomposed). 1H NMR
(DMSO-d6) d 13.86 (1H, bs), 8.21 (1H, d, J=9.7), 7.86
(1H, s), 7.84 (1H, d, J=8.6), 7.73 (1H, d, J=8.5), 6.52
(1H, d, J=9.7). 13C NMR (DMSO-d6) d 159.5, 156.8,
148.6, 147.3, 145.1, 127.7, 121.2, 116.0, 114.4, 114.1,
109.8, 109.3. IR (microscope) 3611, 3080, 1750, 1710,
1562 cm 1. HR MS m/z 230.02109 (M+) (calcd for
C12H6O5: 230.02153).
Cytotoxicity
Safety of the coumarins is another issue to be con-
sidered for further development as a drug. Angular fur-
anocoumarins like angelicin are less likely to form
adducts with DNA during the photoreaction, since they
are monofunctional. However, bifunctional coumarins
like psoralen forms interstrand crosslinks with DNA.14
About a 6 times higher dose is needed to induce 50%
cytoplasmic `petit' mutations in the presence of angel-
icin than in the presence of psoralen.15 In general, intro-
duction of the methyl group increases anity towards
DNA, and addition of methyl to positions 5 and 9 seems
to be the most e€ective in this regard.14 Our cytotoxicity
studies indicate that angelicin, 8b and 11c are almost
non-toxic and can be considered for further development
in this regard. Alkylamine 5b, which shows strong anti-
fungal activity, is cytotoxic as well. This property indi-
cates lack of selectivity in its biological activity.
8-Carbamoyl[N-(1-hexadecane)]-2H-furo[2,3-h]-1-benzo-
pyran-2-one (8c). This compound was prepared from 7a
(100 mg, 0.4 mmol) and 5c (193 mg, 0.8 mmol) in a pro-
cedure similar to that described for 41. Chromato-
graphy (ether) a€orded 8c (34 mg, 0.07 mmol, 19%) as a
white powder, mp 65±67ꢁC. H NMR (CDCl3) d 7.81
1
(1H, d, J=9.7), 7.76 (1H, s), 7.50 (1H, d, J=8.6), 7.43
(1H, d, J=8.8), 6.63 (1H, bt, J=6.1), 6.43 (1H, d,
J=9.5), 3.45 (2H, m), 2.15 (2H, m), 1.25 (26H, bs), 0.88
(3H, t, J=6.7). IR (CHCl3 cast) 3315, 2918, 2850, 1731,
1638 cm 1. HR MS m/z 435.28780 (M+) (calcd for
C28H39NO4: 453.28790).
Conclusion
8-Carbamoyl[N-(1-decane)]-2H-furo[2,3-h]-1-benzopyran-
2-one (8b). This compound was prepared from 7a
(180 mg, 0.8 mmol) and 5b (160 mg, 1 mmol) in a proce-
dure similar to that described for 41. Chromatography
(ether) a€orded 8b (106 mg, 0.3 mmol, 36%) as a
brownish white powder, mp 139±143ꢁC. 1H NMR
(CDCl3) d 7.82 (1H, d, J=9.8), 7.76 (1H, d, J=0.9),
7.51 (1H, d, J=8.8), 7.44 (1H, dd, J=0.6, 8.6), 6.61
(1H, t, J=6.3), 6.45 (1H, d, J=9.8), 3.48 (2H, m), 1.65
(2H, m), 1.26 (14H, bs), 0.88 (3H, t, J=6.4). IR (CHCl3
cast) 3330, 2924, 1723, 1620 cm 1. HR MS m/z
369.19491 (M+) (calcd for C22H27NO4: 369.19400).
Angelicin, a naturally occurring furanocoumarin, which
showed antifungal activity, was considered as a lead
structure for a group of synthetic coumarins. In many
of the synthesized coumarins and angular fur-
anocoumarins, the free 6-OH was found to be impor-
tant for antifungal activity. The free hydroxyl group at
position 7 of the coumarin nucleus, however, is impor-
tant for antibacterial activity.13
Experimental
Melting points were determined on a Fischer melting
point apparatus and are uncorrected. The 1H NMR
8-Carbamoyl[N-(1-propane)]-2H-furo[2,3-h]-1-benzopyran-
2-one (8a). This compound was prepared from 7a

1938
S. Sardari et al. / Bioorg. Med. Chem. 7 (1999) 1933±1940
(100 mg, 0.4 mmol) and 5a (84 mg, 1 mmol, dried over
NaOH) in a procedure similar to that described for
41. Chromatography (ether) a€orded 8a (21.7 mg,
0.08 mmol, 19%) as a white powder, mp 203±207ꢁC. 1H
NMR (CDCl3) d 7.82 (1H, d, J=9.5), 7.77 (1H, d,
J=0.9), 7.51 (1H, d, J=8.6), 7.43 (1H, dd, J=0.9, 8.6),
6.62 (1H, bs), 6.45 (1H, d, J=9.8), 3.47 (2H, m), 1.69
(2H, hx, J=7.5), 1.03 (3H, t, J=7.5); 13C NMR
(CDCl3) d 160.2, 157.9, 149.9, 147.2, 143.9, 140.7, 126.1,
Na2S2O4. Chromatography (benzene:ether, 3:1) of dried
organic phase a€orded 9fꢁ(18 mg, 0.06 mmol, 70%) as a
(1H, s), 7.50 (1H, d, J=9.3), 7.31 (5H, m), 6.90 (1H, s),
6.69 (1H, s), 6.23 (1H, d, J=9.3), 5.11 (2H, s), 4.63 (2H,
s). IR (KBr) 2960, 2872, 1730, 1278 cm 1. HR MS m/z
310.08408 (M+) (calcd for C18H14O5: 310.08414).
1
white powder, mp 73±75 C. H NMR (CDCl3) d 9.80
6-Benzyloxy-7-[2,3-(dihydroxy)propoxy]-2H-1-benzopyran-
2-one (9g). Compound 9e (18 mg, 0.06 mmol), was
added to a stirring mixture of OsO4 (2 drops of 5%
solution in t-BuOH), THF (2 mL), MeOH (0.2 mL),
NMO (N-methylmorpholin oxide) (11 mg, 0.09 mmol)
at room temperature. After 5 h, water and CHCl3 were
added (20 mL each), and the aqueous phase was extrac-
ted two more times with CHCl3. Then the organic phase
was detoxi®ed by Na2S2O4 and chromatographed (10%
MeOH in CHCl3) to a€ord 9g (18 mg, 0.05 mmol, 90%)
as a pale-yellow powder, mp 170±172ꢁC. 1H NMR
(CD3OD) d 7.70 (1H,d, J=9.7), 7.37 (2H, d, J=6.8),
7.25 (3H, m), 7.06 (1H, s), 6.90 (1H, s), 6.16 (1H, d,
J=9.3), 5.06 (2H, s), 4.10 (1H, dd, J=4.2, 9.5), 4.01
(1H, dd, J=5.9, 9.3), 3.96 (1H, m), 3.62 (2H, m); 13C
NMR (CD3OD) d 163.5, 154.3, 151.2, 146.7, 145.5,
137.6, 129.4, 129.1 (2C), 128.9, 128.6 (2C), 113.6, 113.0,
102.1, 72.7, 71.6, 71.1, 63.9. IR (KBr) 3412, 2944, 1706,
1280 cm 1. HR MS m/z 342.11007 (M+) (calcd for
C19H18O6: 342.11035).
115.0, 114.1, 110.3, 108.8, 107.2, 41.3, 23.0, 11.5. IR
1
(CHCl3 cast) 3340, 2925, 2853, 1728, 1651 cm
.
6-[1-(ꢀ-D-(Glucopyranosyloxy)]-7-(3-allyloxy)-2H-1-
benzopyran-2-one (9b). This compound was prepared
from 9a (10 g, 27.2 mmol) by a procedure similar to that
described for 11g, except that the mixture was heated to
90ꢁC for 9 h, then EtOH (50 mL) and CHCl3 (150 mL)
were added and the ®ltrate a€ords 9b upon evapora-
tion (6.49 mg, 17.1 mmol, 62%) as a yellowish white
powder, mp 165±167ꢁC. 1H NMR (CD3OD) d 7.76 (1H,
d, J=9.3), 7.29 (1H, s), 6.88 (1H, s), 6.15 (1H, d,
J=9.3), 6.00 (1H, m), 5.63 (1H, m), 5.39 (1H, dt, J=17,
1.5), 5.22 (1H, ddd, J=1.5, 3.0, 10.7), 4.87 (1H, d,
J=7.3), 3.85 (1H, d, J=7.3), 3.81 (1H, dd, J=2.2,
11.9), 3.60 (1H, dd, J=5.6, 11.9), 3.37 (4H, m); 13C
NMR (CD3OD) d 163.5, 153.9, 152.0, 145.8, 145.4,
133.8, 118.8, 116.3, 113.9, 113.4, 102.9, 102.8, 78.3, 77.9,
74.9, 71.4, 67.4, 62.6. IR (KBr) 3404, 2928, 1758, 1728,
1282, 1076 cm 1. HR MS m/z 381.11781 (M++1)
(calcd for C18H20O9: 381.11856).
6,7-Dihydroxy-8-propyl-2H-1-benzopyran-2-one (10b).
Compound 10a (10 mg, 0.03 mmol) dissolved in metha-
nol (5 mL) and Pd-C (10%) powder (catalytic amount)
was added. The air in the container was replaced with
H2 by the help of consecutive vacuuming and re®lling
with hydrogen. After 30 min of stirring, the reaction
was terminated by letting air in. Then the solvent was
removed in vacuo and ®nally chromatography (10%
MeOH in CHCl3) a€orded 10b (4 mg, 0.02 mmol, 74%)
as a dark-yellow powder, mp 200±201ꢁC. 1H NMR
(CD3OD) d 7.51 (1H, d, J=9.3), 6.68 (1H, s), 6.12 (1H,
d, J=9.3), 2.75 (2H, t, J=7.6), 1.57 (2H, m), 1.19 (3H,
t, J=7.3); 13C NMR (CD3OD) d 165.1, 150.7, 147.1,
132.9, 130.4, 118.4, 112.9, 112.5, 110.6, 69.6, 14.8, 11.9.
IR (KBr) 3508, 2932, 1680, 1580, 1300 cm 1. HR MS
m/z 220.07298 (M+) (calcd for C12H12O4: 220.07356).
6-[1-[ꢀ-D-(2,3,4,6-Tetra-O-acetyl glucopyranosyloxy)]]-
7-(3-allyloxy)-2H-1-benzopyran-2-one (9c). Compound
9b (26 mg, 0.07 mmol), was dissolved in pyridine (5 mL),
DMAP (20 mg), and acetic anhydride (0.5 mL) were
added. After stirring for 10 h at room temperature, the
mixture was diluted with ether (50 mL) and washed with
HCl (3 N) (three times, 10 mL each), water (three times,
10 mL each) and brine. The organic layer was dried over
Na2SO4 and the solvent was removed in vacuo. Chro-
matography (hexane:EtOAc, 3:2) a€orded 9c (28 mg,
0.05 mmol, 78%) as a white powder, mp 147±150ꢁC. 1H
NMR (CDCl3) d 7.51 (1H, d, J=9.8), 7.16 (1H, s), 6.77
(1H, s), 6.22 (1H, d, J=9.8), 5.95 (1H, m), 5.39 (1H, dd,
J=1.2, 17.4), 5.28 (1H, dd, J=1.2, 10.5), 5.22 (2H, m),
5.10 (1H, m), 4.91 (1H, dd, J=2.4, 5.4), 4.54 (2H, d,
J=5.4), 4.21 (1H, dd, J=5.2, 12.2), 4.11 (1H, dd,
J=2.4, 12.2), 3.70 (1H, m), 2.00 (3H, s), 1.99 (3H, s),
1.97 (6H, s); 13C NMR (CDCl3) d 170.4, 170.2, 169.4,
169.3, 160.9, 153.2, 152.0, 143.0, 142.5, 131.8, 118.9,
118.7, 114.0, 111.7, 101.8, 100.5, 72.5, 72.1, 71.1, 69.9,
68.3, 61.8, 20.7 (2C), 20.6, 20.5. IR (KBr) 3480, 2928,
1756, 1740, 1232, 1046 cm 1. HR MS m/z 548.15333
(M+) (calcd for C26H28O13: 548.15302).
6-Benzyloxy-7-hydroxy-8-[2,2-(dimethoxy)ethyl]-2H-1-
benzopyran-2-one (10e). Compound 10d (3 mg,
0.01 mmol) and dl-10 camphorsulphonic acid (catalytic
amount), were added to anhydrous methanol (1 mL).
After 2 h of stirring at room temperature, NEt3 (2
drops) was added to quench the progression of the
reaction. Water and CHCl3 (5 mL each) were added and
the organic layer was washed with water (total three
times, 10 mL each). The organic phase was dried over
Na2SO4 and the solvent was evaporated. Chromato-
graphy (hexane:EtOAc, 1:1) yielded 10e (2 mg,
6-Benzyloxy-7-[2-(oxo)ethoxy]-2H-1-benzopyran-2-one
(9f). Compound 9e (26 mg, 0.08 mmol) was added to a
stirring mixture of NaIO4 (600 mg, 2.8 mmol), THF (2
mL), MeOH (0.2 mL), H2O (2 drops) and OsO4 (2
drops of 5% solution in t-BuOH) at room temperature.
After 5 h, water and chloroform (20 mL each) were
added and the aqueous phase was extracted two more
times with CHCl3. The organic phase was detoxi®ed by
0.006 mmol, 58%) as a yellow powder, mp 45±48ꢁC. H
1
NMR (CDCl3) d 7.48 (1H, d, J=9.3), 7.33 (5H, m), 7.19
(1H, s), 6.77 (1H, s), 6.17 (1H, d, J=9.3), 5.08 (2H, s),
4.68 (1H, t, J=4.9), 3.36 (6H, s), 3.18 (2H, d, J=4.9);
13C NMR (CDCl3) d 161.3, 149.5, 148.8, 144.0, 143.8,
136.0, 128.8 (2C), 128.4, 127.6 (2C), 113.0, 111.8, 111.3,

S. Sardari et al. / Bioorg. Med. Chem. 7 (1999) 1933±1940
1939
108.9, 103.8, 71.7, 53.8 (2C), 27.4. IR (KBr) 3376, 2932,
1724, 1580, 1296 cm 1. HR MS m/z 365.12585 (M+)
(calcd for C20H20O6: 365.12598).
HR MS m/z 246.05266 (M+) (calcd for C13H10O5:
246.05283).
6-Acetoxy-2H-furo[2,3-h]-1-benzopyran-2-one (11f). This
compound was prepared from 11a (4 mg, 0.02 mmol) by
a procedure similar to that described for 11i. Yield: 11f
(3 mg, 0.01 mmol, 62%) as a yellow powder, mp 134±
6-Hydroxy-2H-furo[2,3-h]-1-benzopyran-2-one (11a).
Pd(OH)2 (catalytic amount) was added to a solution of
11b (15 mg, 0.05 mmol), in MeOH:EtOAc (2:1), and
stirred for 1 h, in an atmosphere of H2. Chromato-
graphy (benzene:ether, 3:1) of the mixture a€orded 11a
(6 mg, 0.03 mmol, 59%) as a yellow powder, mp 220±
136ꢁC. H NMR (CDCl3) d 7.68 (1H, d, J=9.3), 7.63
1
(1H, d, J=2.2), 7.12 (1H, s), 7.10 (1H, d, J=2.2), 6.36
(1H, d, J=9.3), 2.10 (3H, s); 13C NMR (CDCl3) d
168.4, 160.4, 148.8, 146.6, 146.4, 144.3, 132.9, 119.3,
116.2, 115.2, 113.8, 105.1, 20.9. IR (KBr) 1774, 1732,
1306, 1210 cm 1. HR MS m/z 244.03758 (M+) (calcd
for C13H8O5: 244.03717).
222ꢁC. H NMR (CDCl3) d 7.67 (1H, d, J=9.3), 7.63
1
(1H, d, J=2.4), 7.06 (1H, d, J=2.4), 6.76 (1H, s), 6.31
1
(1H, d, J=9.3). IR (CHCl3 cast) 3315, 1716, 1698 cm
.
HR MS m/z 202.02617 (M+) (calcd for C11H6O4:
202.02661).
6-(3-Allyloxy)-2H-furo[2,3-h]-1-benzopyran-2-one (11g).
Compound 11a (8 mg, 0.04 mmol) was dissolved in dry
DMF (5 mL), which contained allylbromide (2.8 mg,
0.04 mmol), and K2CO3 (55.2 mg, 0.4 mmol). After
30 min of stirring at room temperature, ®rst CHCl3
then water (20 mL each) were added and the aqueous
phase was extracted two more times with CHCl3. The
organic phase was then washed three times with water
and chromatographed (benzene:ether, 3:1) to a€ord 11g
(7 mg, 0.03 mmol, 72%) as a yellow powder, mp 125±
127 C. H NMR (CDCl3) d 7.67 (1H, d, J=9.8), 7.64
(1H, d, J=2.4), 7.07 (1H, d, J=2.4), 6.74 (1H, s), 6.33
(1H, d, J=9.8), 6.06 (1H, m), 5.42 (1H, ddd, J=1.5, 3.0,
17.1), 5.29 (1H, ddd, J=1.2, 2.7, 10.7), 4.70 (2H, m);
13C NMR (CDCl3) d 162.5, 153.8, 148.9, 146.0, 144.3,
142.0, 132.4, 118.7, 117.1, 114.5, 113.6, 105.6, 104.6,
70.4. IR (KBr) 1706, 1582, 1344 cm 1. HR MS m/z
242.05703 (M+) (calcd for C14H10O4: 242.05791).
6-Hydroxy-2H-furo[2,3-h]-1-benzopyran-2-one (11a), 6-
benzyloxy-2H-furo[2,3-h]-1-benzopyran-2-one (11b) and
5-benzyl-6-hydroxy-2H-furo[2,3-h]-1-benzopyran-2-one
(11c). Compound 10d (15 mg, 0.05 mmol) and p-tol-
uenesulphonic acid (catalytic amount) were added to
benzene (5 mL). The stirring mixture was heated at
70ꢁC for 1 h. After this period, CHCl3 and NaHCO3
(1 M) (10 mL each) were added, and the chloroform
solution was washed two more times with alkaline. The
organic phase was evaporated and chromatography
(benzene:ether, 3:1) yielded 11a (4 mg, 0.02 mmol,
38%), 11b (3 mg, 0.01 mmol, 22%) and 11c (3 mg,
0.01 mmol, 22%). Compound 11b was separated as a
yellow powder, mp 95±97ꢁC. 1H NMR (CDCl3,
CD3OD) d 7.65 (1H, d, J=2.4), 7.64 (1H, d, J=8.8),
7.43 (2H, m), 7.33 (3H, m), 7.08 (1H, d, J=2.0), 6.77
(1H, s), 6.32 (1H, d, J=9.3), 5.2 (2H, s). IR (CHCl3
cast) 2930, 1724, 1579, 1307 cm 1. HR MS m/z
292.07348 (M+) (calcd for C18H12O4: 292.07355).
ꢁ
1
6-(1-Propyloxy)-2H-furo[2,3-h]-1-benzopyran-2-one (11h).
Five milligrams (0.031 mmol) of 11g were dissolved in
5 mL EtOAc with few drops of MeOH. A catalytic
amount of Pd-C (10%) was added and the mixture was
hydrogenated at atmospheric pressure. After 30 min, the
mixture was ®ltered. Chromatography (10% MeOH in
CHCl3) of the mixture a€orded 11h (5 mg, 0.02ꢁmmol,
Compound 11c was isolated as a dark-yellow powder,
mp 214±217ꢁC (decomposed). H NMR (CDCl3) d 7.87
1
(1H, d, J=9.8), 7.63 (1H, d, J=2), 7.16 (2H, m), 7.05
(1H, d, J=2), 7.01 (3H, m), 6.22 (1H, d, J=9.8), 5.31
(1H, s), 4.31 (2H, s); 13C NMR (CDCl3) d 161.6, 147.0,
145.2, 142.5, 140.1, 137.6, 128.4, 128.4, 127.9, 127.9,
125.9, 123.0, 118.5, 116.2, 115.2, 113.3, 104.5, 30.6. IR
(KBr) 3168, 2924, 1696, 1574, 1280 cm 1. HR MS m/z
292.07276 (M+) (calcd for C18H12O4: 292.07355).
1
73%) as a greenish-yellow powder, mp 141±143 C. H
NMR (CDCl3) d 7.68 (1H, d, J=9.5), 7.64 (1H, d,
J=2.0), 7.06 (1H, d, J=2.0), 6.72 (1H, s), 6.33 (1H, d,
J=9.5), 4.09 (2H, t, J=6.6), 1.87 (2H, hex, J=6.9), 1.04
(3H, t, J=7.4); 13C NMR (CDCl3) d 161.1, 147.2, 145.9,
144.4, 143.0, 142.5, 118.6, 114.4, 113.6, 104.8, 104.5,
71.1, 22.5, 10.4. IR (KBr) 2924, 2856, 1726, 1580,
1344 cm 1. HR MS m/z 244.07328 (M+) (calcd for
C14H12O4: 244.07356).
5,6-Dimethoxy-2H-furo[2,3-h]-1-benzopyran-2-one (11e).
Compound 11a (5 mg, 0.025 mmol) was added to a
mixture of dimethyl sulfate (7.3 mg, 0.06 mmol), K2CO3
(35 mg, 0.25 mmol), in MeOH (5 mL), and the mixture
was stirred for 5 h at room temperature. The reacting
materials were partitioned between water and chloro-
form (20 mL each), and the organic phase was extracted
two more times with CHCl3. Then the organic phase
was washed three times with water and chromato-
graphed (hexane:EtOAc, 2:1), to a€ord 11e (1 mg,
0.004 mmol, 16%) and 11d (2 mg, 0.009 mmol, 37%).
5-Benzyl-6-acetoxy-2H-furo[2,3-h]-1-benzopyran-2-one
(11i). A mixture of 11c (2 mg, 0.007 mmol), acetic
anhydride (0.5 mL), CH2Cl2 (5 mL), DMAP (dimethyl
amino pyridine) (catalytic amount), and NEt3 (0.7 mg,
0.007 mmol) was stirred for 30 min at room tempera-
ture. The reaction mixture was partitioned between
water and CHCl3 (20 mL each), followed by two more
extractions with CHCl3. The organic layer was then
washed three times with water, HCl (0.1 N) and ®nally
with 0.1 M solution of K2CO3. Chromatography (10%
MeOH in CHCl3) of the dried organic mixture a€orded
11i (2 mg, 0.005 mmol, 78%) as a yellow powder, mp
11e was obtained as a yellow powder, mp 83±85ꢁC. H
1
NMR (CDCl3) d 8.02 (1H, d, J=9.8), 7.59 (1H, d,
J=2.5), 7.02 (1H, d, J=2), 6.30 (1H, d, J=9.8), 4.08
(3H, s), 3.97 (3H, s); 13C NMR (CDCl3) d 165.5, 162.8,
158.0, 145.4, 140.5, 139.9, 128.5, 117.0, 114.5, 113.8,
1
104.3, 62.4, 61.2. IR (CHCl3 cast) 2922, 1731 cm
.

1940
S. Sardari et al. / Bioorg. Med. Chem. 7 (1999) 1933±1940
128±131ꢁC. H NMR (CDCl3) d 7.79 (1H, d, J=9.9),
7.61 (1H, d, J=2.0), 7.18 (2H, m), 7.09 (1H, d, J=2.2),
7.03 (3H, m), 6.25 (1H, d, J=9.9), 4.19 (2H, s), 2.32
(3H, s); 13C NMR (CDCl3) d 175.1, 168.2, 146.0, 145.3,
141.4, 138.8, 128.8 (2C), 127.9 (2C), 126.6, 125.5, 122.9,
117.4, 114.4, 113.0, 105.2, 104.8, 30.9, 20.3. IR (KBr)
1760, 1738, 1204 cm 1. HR MS m/z 344.08455 (M+)
(calcd for C20H14O5: 344.08414.)
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Acknowledgements
The authors wish to thank Dr. T. Harayama for pro-
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thank Ms. Bernadette Oreski and Ms. Kathy Koski for
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