Synthesis and evaluation of a class of new coumarin triazole derivatives as potential antimicrobial agents

Article abstract of DOI:10.1016/j.bmcl.2010.12.059

A series of new coumarin-based 1,2,4-triazole derivatives were designed, synthesized and evaluated for their antimicrobial activities in vitro against four Gram-positive bacteria (Staphylococcus aureus, MRSA, Bacillus subtilis and Micrococcus luteus), fou

Full text of DOI:10.1016/j.bmcl.2010.12.059

Bioorganic & Medicinal Chemistry Letters 21 (2011) 956–960
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and evaluation of a class of new coumarin triazole derivatives
as potential antimicrobial agents
⇑
Yuan Shi, Cheng-He Zhou
Laboratory of Bioorganic & Medicinal Chemistry, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of new coumarin-based 1,2,4-triazole derivatives were designed, synthesized and evaluated for
their antimicrobial activities in vitro against four Gram-positive bacteria (Staphylococcus aureus, MRSA,
Bacillus subtilis and Micrococcus luteus), four Gram-negative bacteria (Escherichia coli, Proteus vulgaris, Sal-
monella typhi and Shigella dysenteriae) as well as three fungi (Candida albicans, Saccharomyces cerevisiae
and Aspergillus fumigatus) by two-fold serial dilution technique. The bioactive assay showed that some
synthesized coumarin triazoles displayed comparable or even better antibacterial and antifungal efficacy
in comparison with reference drugs Enoxacin, Chloromycin and Fluconazole. Coumarin bis-triazole com-
pounds exhibited stronger antibacterial and antifungal efficiency than their corresponding mono-triazole
derivatives.
Received 15 September 2010
Revised 25 November 2010
Accepted 9 December 2010
Available online 16 December 2010
Keywords:
Coumarin
1,2,4-Triazole
Antibacterial
Antifungal
Ó 2010 Elsevier Ltd. All rights reserved.
Coumarins and their derivatives have attracted considerable
attention due to their extensively biological activities such as anti-
bacterial, antifungal, antiviral, anti-tubercular, anti-malarial, anti-
coagulant, anti-inflammatory, anticancer, antioxidant properties
and so on. Numerous efforts, including the separation and purifica-
tion of naturally occurring coumarins from a variety of plants as
well as artificial synthesis of coumarin compounds with novel
structures and properties, have been focusing on the research
and development of coumarins as potential drugs. So far some cou-
marins, for example, Warfarin, Acenocoumarol, Armillarisin A,
Hymecromone and Carbochromen have been approved for thera-
peutic purposes in clinic. More importantly, an increasing number
of coumarin compounds have displayed great potency in the treat-
ment of various types of diseases.1–3
Coumarin compounds, containing 1,2-benzopyrone skeleton
structurally similar to clinical anti-infective quinolone drugs with
benzopyridone backbone, as a new type of antibiotics have re-
ceived specific interest along with the dramatically rising preva-
lence of multi-drug resistant microbial infections. It is well
known that the quinolone anti-infectives are of wholly synthetic
origin and not modeled knowingly after any natural antibiotics.
Of all the totally synthetic antimicrobial agents, the quinolones
have proved to be most successful economically and clinically. As
predominant antibacterial drugs, quinolones have been widely
used in clinic with orally and parenterally active properties, broad
antimicrobial spectrum including many frequently encountered
pathogens, and bactericidal behavior in clinically achievable doses.
Clearly, quinolone anti-infectives have been playing important
roles in the past fifty years in the unending struggles against mor-
bidity and mortality caused by microbial pathogens.4 However, the
prevalently clinical use of this class of anti-infectives has led to
increasingly worrisome resistance at a disturbing rate, which has
posed serious problems in the treatment of infectious diseases.5
This trend has highlighted the urgent need for designing and devel-
oping powerful antimicrobial compounds, especially for the explo-
ration of new quinolone-like compounds. Reasonably, a great deal
of work has recently directed towards coumarin compounds which
have similar structural framework to quinolones. Some naturally
occurring coumarins such as Novobiocin, Coumermycin A1 and
Chlorobiocin have been found to be an unprecedented class of anti-
biotics, but they are not used in clinic owing to their relatively
weak activity towards Gram-negative bacteria, poor water solubil-
ity and side effects.6 However, wholly synthetic coumarin com-
pounds have drawn renewed attention because of their
prominent antibacterial properties, specifically against methicil-
lin-resistant Staphylococcus aureus (MRSA).1–3 In recent years,
some works have manifested that coumarin backbone in combina-
tion with some nitrogen-containing heterocyclic moieties such as
azetidine, thiazolidine, thiazole and so on could significantly in-
crease the antimicrobial efficiency and broaden their antimicrobial
spectrum.7 In this work, we would like to introduce 1,2,4-triazolyl
ring into coumarin.
As important aromatic nitrogen-containing heterocycle, 1,2,4-
triazole compounds have aroused special interest due to their
excellent pharmacokinetic characteristics, favorable safety profile,
as well as the latent ability for the formation of hydrogen bonds
⇑
Corresponding author. Tel./fax: +86 23 68254967.
E-mail address: zhouch@swu.edu.cn (C.-H. Zhou).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.12.059

Y. Shi, C.-H. Zhou / Bioorg. Med. Chem. Lett. 21 (2011) 956–960
957
with other active molecules. A number of triazole drugs including
Fluconazole, Itraconazole and Voriconazole have been prevalently
used in the anti-infective therapy.8,9 Recently, some triazole deriv-
atives have been reported to exhibit good anti-MRSA potency.10
Although the extensively clinical use of triazole anti-infective
agents has ever revolutionized the treatment of many infectious
diseases, some of them are still limited by poor activities towards
intractable fungi, high frequency of renal toxicity and several ad-
verse effects. Therefore, these situations have been served as impe-
tus for developing new triazole antimicrobial agents.
Prompted by above observations and in continuation of our on-
going interest in the development of new antimicrobial agents,10–12
herein we designed and synthesized a class of new coumarin tria-
zole compounds and evaluated their antibacterial and antifungal
activities in vitro. In order to investigate the effect of heterocyclic
triazole moiety on antimicrobial activity, coumarin bis-triazoles
7a–d, mono-triazoles 6a–d as well as non-triazole bis-coumarins
10a–d and coumarin bromides 4–5 were prepared. A lot of re-
searches have provided evidences that the linkers could modulate
the physicochemical properties of the whole molecule and thereby
affect biological activities.13,14 Based on this, and with the aim of
better understanding of structure–activity relationship, various
types of linkers including alkyl and aralkyl ones, as well as the
spacers with different lengths of aliphatic chains were introduced
into the target compounds. Recent studies also found that the
transformation of azoles into their corresponding salts could en-
hance antimicrobial efficacy remarkably due to the improvement
of water solubility and membrane permeability.13–15 Thus, some
representative coumarin mono-triazoles 6a and 6d as well as bis-
triazoles 7a and 7d were converted into the corresponding hydro-
chlorides 8a–b and 9a–b.
marin triazoles 6–7 in satisfactory yields ranging from 71% to 83%.
The treatment of coumarin mono-triazoles 6a and 6d as well as
bis-triazoles 7a and 7d with hydrochloric acid were almost quan-
titatively transformed into corresponding hydrochlorides 8a–b
and 9a–b. The coupling of coumarin halides 4a–d with hydroxy-
coumarin 2 generated bis-coumarins 10a–d with yields of 81–
83%. All new compounds were characterized by 1H NMR, 13C NMR,
IR, MS, HRMS spectra and elemental analyses.16
These synthesized compounds were screened for their antimi-
crobial activities in vitro against four Gram-positive bacteria (S.
aureus ATCC 25923, S. aureus N 315, B. subtilis ATCC 6633 and M.
luteus ATCC 4698), four Gram-negative bacteria (E. coli ATCC
25922, P. vulgaris ATCC 6896, S. typhi ATCC 9484 and S. dysenteriae
ATCC 49550) as well as three fungi (C. albican ATCC 76615, S. cere-
visiae ATCC 9763 and A. fumigatus ATCC 96918) using two-fold
broth dilution method in 96-well micro-test plates recommended
by National Committee for Clinical Laboratory Standards
(NCCLS).17 Clinically antimicrobial drugs Enoxacin, Chloromycin
and Fluconazole were used as the positive control. The obtained re-
sults, depicted in Table 1, revealed that these prepared coumarin
compounds 2–10 could effectively, to some extent, inhibit the
growth of all tested strains in vitro, except for bis-coumarin 10d
with an aralkyl spacer, which had poor water solubility. The pre-
pared coumarin triazole compounds 6–9 demonstrated moderate
to excellent antimicrobial activities towards the tested microor-
ganisms, including methicillin-resistant S. aureus and Fluconaz-
ole-insensitive A. fumigatus, which showed broad antimicrobial
spectrum. Noticeably, some triazole derivatives gave comparable
or superior MIC values to standard drugs Chloromycin, Enoxacin
and Fluconazole. Especially, bis-triazole 7a and its corresponding
hydrochloride 9a gave quite low inhibitory concentrations (1–
The desired coumarin compounds were prepared from com-
mercially available phenols, and the synthetic route was outlined
in Scheme 1. The cyclization of resorcinol and phloroglucinol,
respectively, with ethyl acetoacetate in the presence of oxalic acid
formed the corresponding 7-hydroxy-coumarin 2 with excellent
yield of 92% and 5,7-dihydroxy-coumarin 3 in 90% yield. Hydro-
xyl-coumarin 2 or 3 reacted with alkyl or aralkyl dibromides sep-
arately in acetone using potassium carbonate as base to produce
intermediate coumarin bromides 4–5 in good yields (73–85%).
The N-alkylation of compounds 4–5 with 1,2,4-triazole, respec-
tively, in the presence of potassium carbonate gave the target cou-
4
l
g/mL), which suggested that they were potential as antimicro-
bial agents in comparison with clinical drugs Chloromycin
(MIC = 4–16 g/mL), Enoxacin (MIC = 1–4 g/mL) and Fluconazole
(MIC = 1–128 g/mL). It was also observed that Gram-positive
l
l
l
microorganisms were more sensitive than Gram-negative bacteria
to hydroxyl-coumarins 2–3, bromides 4–5, bis-coumarins 10a–c as
well as mono-triazoles 6a–d and 8a–b. Furthermore, MRSA was
known to be the most distraught and virulent organism that
caused a broad array of problems to hospitalized and commu-
nity-acquired patients, and showed multi-drug resistance to
numerous currently available agents including the standard drugs
3 O R2
R2
O
CH3 O
O
CH
N N
N N
N
R2
R2 Br
CH3 OH
CH3 O
(b)
(c)
O
(d)
N
R2
2 HCl
•
O
O
O
O
N N
N
N N
N
R2 Br
O
O
OH
O
O
O
3
7a-d
9a-b
5a-d
R1 = OH
OH
(a)
R2 Br
O
O
R2
O
O
R1
O
OH
O
O
O
O
O
(e)
(a)
R1 = H
(b)
O
1
2
4a-d
10a-d
CH3
CH3
OH
CH3
(c)
CH3
4-7, 10: a, R2 =
8, 9: a, R2 =
b, R2 =
(CH2)2
(CH2)3
(CH2)2
O
R2 N N
N
O
O
R2 N N
O
O
2
b
, R =
(d)
N
c, R2 =
d, R2 =
(CH2)4
•
HCl
6a-d
8a-b
CH3
CH3
Scheme 1. Reagents and conditions: (a) ethyl acetoacetate, oxalic acid, 90–100 °C, 10–16 h; (b) alkyl or aralkyl dibromide, K2CO3, acetone, reflux, 10–14 h; (c) 1,2,4-triazole,
K2CO3, CH3CN, rt, 14–22 h; (d) 4 mol/L HCl, ethyl ether/chloroform, rt, 10–14 h; (e) compound 2, NaOH, CH3CN, 50 °C, 8–12 h.

958
Y. Shi, C.-H. Zhou / Bioorg. Med. Chem. Lett. 21 (2011) 956–960
Table 1
In vitro antimicrobial activities for some synthetic coumarin compounds 2–10 expressed as MIC (
l
g/mL)
Compds
Gram-positive bacteria
Gram-negative bacteria
Fungi
S. aureus
MRSA
B. subtilis
M. luteus
E. coli
P. vulgaris
S. typhi
S. dysenteriae
C. albicans
S. cerevisiae
A. fumigatus
2
3
4a
4b
4c
4d
5a
5b
32
32
128
128
64
256
256
128
256
256
2
64
64
32
64
128
128
128
256
128
128
128
128
2
32
64
128
256
64
256
256
128
128
256
4
128
128
256
512
512
512
512
512
512
512
8
256
128
256
512
256
512
256
256
512
512
16
128
256
256
512
256
512
256
256
512
256
16
512
256
512
256
512
512
256
256
512
512
16
64
64
128
128
256
256
128
128
128
256
2
128
256
256
512
256
256
256
256
128
256
4
128
256
512
256
512
256
256
128
128
256
16
256
256
256
512
512
256
512
512
8
5c
5d
6a
6b
4
16
4
8
32
32
16
32
8
16
16
6c
6d
7a
8
32
1
16
64
2
8
32
2
8
32
1
32
64
1
32
64
2
32
64
1
32
64
1
16
32
1
32
64
2
32
64
4
7b
2
8
4
4
8
4
4
4
2
4
32
7c
8
16
4
8
8
8
16
8
4
4
32
7d
8a
32
2
64
8
64
2
64
2
64
4
32
8
32
16
64
16
32
2
32
4
64
8
8b
8
16
8
8
16
16
16
16
8
16
16
9a
1
2
1
1
1
2
1
1
1
2
2
9b
10a
10b
10c
8
16
16
128
256
128
>512
1
16
128
128
128
>512
1
8
16
16
16
8
16
16
128
128
256
>512
1
512
256
512
>512
4
256
256
256
>512
1
256
512
256
>512
1
256
512
512
>512
2
512
512
512
>512
1
512
512
512
>512
—
256
256
256
512
—
512
512
512
>512
—
10d
Enoxacin
Chloromycin
Fluconazole
4
16
8
4
8
8
4
4
—
—
—
—
—
—
—
—
—
—
—
1
2
128
Chloromycin and Enoxacin. Unexpectedly, in our work, coumarin
that, among these tested bis-triazoles, compound 7a with a
triazole compounds 6a–c, 7a–c, 8a–b and 9a–b demonstrated good
(CH2)4 linker possessed the strongest antimicrobial activities, and
anti-MRSA activity with MIC values in the range of 2–16
Among all tested compounds including the positive control Fluco-
nazole, only coumarin trizoles could significantly inhibit the
l
g/mL.
it gave the best anti-MRSA efficacy with MIC value of 2
which was two-fold and eight-fold more active than Enoxacin
(MIC = 4 g/mL) and Chloromycin (MIC = 16 g/mL), respectively.
lg/mL,
l
l
growth of A. fumigatus (MIC = 2–64
coumarin triazoles were potential as new antimicrobial agents to-
wards all these tested bacterial and fungal strains.
Mono-hydroxyl-coumarin 2 and dihydroxy-coumarin 3 showed
moderate activities against C. albicans and Gram-positive bacteria
with MIC values of 32–64 lg/mL. However, the incorporation of
bromoalkyl or bromoaralkyl groups into coumarins resulted in dra-
matic decrease in inhibiting the growth of the tested strains in cou-
marin bromides 4a–b, 4d and 5a–d (MIC = 128–512 lg/mL), this
l
g/mL). These implied that
These results further indicated that triazole moiety was specifically
favorable for antimicrobial activities, which could not only broaden
the antimicrobial spectrum, but also increase the bioactivity signif-
icantly. It was also suggested that coumarin bis-triazole 7a was
worthy for further investigations as potential antimicrobial agent.
For tested coumarin mono-triazoles 6a–d and bis-triazoles 7a–
d, the structural parameters of spacers including the types of link-
ers and the lengths of aliphatic chains markedly influenced their
antimicrobial efficacy. Alkyl compounds 6a–c and 7a–c were more
suggested that these bromoalkyl and bromoaralkyl moieties were
not beneficial for antimicrobial efficacy.
active (MIC = 1–32
zoles 6d and 7d (MIC = 32–64
l
g/mL) than their corresponding aralkyl tria-
g/mL). Moreover, the antimicrobial
l
Surprisingly, the introduction of triazole ring instead of bromo
moiety in coumarin bromides 4a–d, which yielded corresponding
coumarin mono-triazole compounds 6a–d, contributed to an unex-
pected enhancement for antimicrobial efficiency. Mono-triazoles
6a–d exhibited better activities than their precursor coumarin bro-
mides 4a–d as well as hydroxyl-coumarin 2. Particularly, com-
pound 6a could efficiently inhibit the growth of all tested Gram-
potency for triazoles 6a–c and 7a–c depended on the lengths of ali-
phatic chains, and the activities seemed to decrease with the in-
crease of aliphatic chain length. Obviously, the bridged linkers
have large effect on their antimicrobial efficiency, and further
works are essential in order to deduce the structure–activity
relationship.
It was also observed that coumarin triazole hydrochlorides 8b
and 9b displayed stronger antibacterial and antifungal efficacy in
comparison with their poor water-soluble aralkyl triazole precur-
sors 6d and 7d. The result was consistent with the literatures. This
transformation of triazole compounds into their hydrochlorides
might modulate the lipid/water partition coefficient, affect their
diffusion in bacterial cells as well as interaction with bacterial cells
and tissues, and thereby improve the pharmacological properties.
Further studies were reasonable to understand their mechanism.
In summary, a series of coumarin triazoles were successfully
synthesized through an easy, convenient and economic synthetic
procedure starting from commercially available resorcinol and
phloroglucinol, and were confirmed by 1H NMR, 13C NMR, IR, MS,
positive bacteria at the concentrations of 2–8
more effective than Chloromycin (4–16 g/mL) and almost equipo-
tent to Enoxacin (MIC = 1–4 g/mL), and its antifungal potency
against C. albicans and S. cerevisiae (MIC = 2–4 g/mL) was also
comparable to positive control Fluconazole (MIC = 1 g/mL). Nev-
lg/mL, which was
l
l
l
l
ertheless, the substitution of triazolyl group in mono-triazoles
6a–d by coumarin ring caused remarkable decrease or total loss
of antimicrobial properties for bis-coumarins 10a–d. These showed
that nitrogen-containing heterocyclic 1,2,4-triazole moiety exerted
important influence on antimicrobial activities. Furthermore, bis-
triazoles 7a–d displayed much stronger antimicrobial efficacy in
contrast to mono-triazoles 6a–d. It was particularly pointed out

Y. Shi, C.-H. Zhou / Bioorg. Med. Chem. Lett. 21 (2011) 956–960
959
temperature, and then compound 4d (1.79 g, 5 mmol) was added. The
resulting mixture was stirred at room temperature for 16 h (monitored by
TLC, eluent, chloroform/acetone, 3/1, V/V). The solvents were evaporated under
reduced pressure, and the residue was treated with water (50 mL) and
extracted with chloroform (3 Â 50 mL). The organic layers were combined,
dried with anhydrous Na2SO4, and concentrated under reduced pressure. The
crude product was purified via silica gel column chromatography (eluent,
chloroform/acetone, 3/1, V/V) and recrystallized from the mixture solvent of
chloroform/petroleum ether (1/2, V/V) to afford compound 6d (1.40 g) as white
HRMS spectra and elemental analyses. The in vitro antibacterial and
antifungal evaluation showed that most synthesized coumarin
compounds could effectively inhibit the growth of all tested bacte-
ria and fungi including methicillin-resistant S. aureus and Fluconaz-
ole-insensitive A. fumigatus, and some coumarin triazoles displayed
excellent antimicrobial activities in contrast to their positive con-
trol. Particularly, bis-triazole 7a and its hydrochloride 9a containing
solid. Yield 81%; mp 156–157 °C; IR (KBr)
(CH2), 1704 (C@O), 1619, 1573, 1511, 1506 (aromatic frame), 1389, 1370, 1296,
1150, 1006, 990, 940, 870, 827, 786, 712 cmÀ1 1H NMR (400 MHz, CDCl3) d:
m: 3115, 3067 (Ar-H), 2976, 2957
a
(CH2)4 linker gave the most potent antimicrobial efficacy
(MIC = 1–4 g/mL) among these tested substances including the
l
;
standard drugs. Moreover, the anti-MRSA activity for coumarin tri-
azole compounds 6a–c, 7a–c, 8a–b and 9a–b were comparable or
superior to currently clinical antibacterial drugs Enoxacin and Chlo-
romycin, which suggested that further investigations are necessary
to optimize these potentially leading compounds as more effica-
cious antibacterial agents. Compared to antifungal drug Fluconaz-
ole, all title compounds displayed much stronger inhibition
towards A. fumigatus, which should be a good starting point for fur-
ther extension of triazole derivatives as anti-A. fumigatus drugs.
These results confirmed that the incorporation of 1,2,4-triazole moi-
ety was greatly helpful for the antimicrobial activities, which could
not only increase the inhibition remarkably, but also broaden their
antimicrobial spectrum. Other related works, including the in vivo
bioactive evaluation along with toxicity investigation, the effect fac-
tors on antimicrobial activities such as other heterocyclic azole
rings (benzotriazole, imidazole, benzimidazole and their deriva-
tives, etc.) as well as spacers with different types of linkers (alkyl,
aralkyl, aryl and heterocyclic types and their lengths of chains) are
active in progress. All these will be discussed in the future paper.
8.07 (s, 1H, triazole 3-H), 7.83 (s, 1H, triazole 5-H), 7.53–7.50 (d, 1H, coumarin
5-H), 7.18–7.00 (m, 4H, Ar-H), 6.92–6.91 (d, 1H, coumarin 6-H), 6.66 (s, 1H,
coumarin 8-H), 6.13 (s, 1H, coumarin 3-H), 5.15 (s, 2H, coumarin-OCH2), 4.99
(s, 2H, triazole-CH2), 2.40 (s, 3H, coumarin-CH3) ppm; 13C NMR (100 MHz,
DMSO-d6) d: 161.4 (coumarin 2-C), 161.1 (coumarin 7-C), 155.2 (coumarin 9-
C), 152.5 (coumarin 4-C), 151.8 (triazole 3-C), 145.8 (triazole 5-C), 136.0
(OCH2Ph 1-C), 135.1 (OCH2Ph 4-C), 131.7 (OCH2Ph 3,5-C), 131.0 (OCH2Ph 2,6-
C), 128.8 (coumarin 5-C), 115.5 (coumarin 3-C), 114.9 (coumarin 10-C), 114.0
(coumarin 6-C), 104.6 (coumarin 8-C), 73.8 (coumarin-OCH2), 54.6 (triazole-
CH2), 20.4 (coumarin-CH3) ppm; MS (m/z): 347 [M]+; HRMS (TOF) calcd for
C
20H18N3O3 [M+H]+, 348.1348; found, 348.1352; Anal. Calcd for C20H17N3O3: C,
69.15; H, 4.93; N, 12.10. Found: C, 69.19; H, 4.89; N, 12.07.
Synthesis of 5,7-bis(4-(1H-1,2,4-triazol-1-yl)butoxy)-4-methyl-2H-chromen-2-
one (7a). Prepared according to the procedure described for the preparation
of compound 6d, starting from compound 5a (2.38 g, 5 mmol), triazole (0.83 g,
12 mmol), potassium carbonate (1.67 g, 12 mmol) and CH3CN (30 mL), the
crude product was obtained and further purification by chromatography
(chloroform/methanol, 6/1, V/V) produced bis-triazole 7a (1.67 g) as white
solid. Yield 77%; mp 121–123 °C; IR (KBr)
(CH2), 1707 (C@O), 1633, 1600, 1543, 1477 (aromatic frame), 1306, 1220, 1190,
1084, 1002, 848, 804, 731, 715 cmÀ1 1H NMR (300 MHz, CDCl3) d: 8.10 (s, 2H,
m: 3118, 3076 (Ar-H), 2987, 2944
;
triazole 3-H), 7.94 (s, 2H, triazole 5-H), 6.36 (s, 1H, coumarin 6-H), 6.20 (s, 1H,
coumarin 8-H), 5.91 (s, 1H, coumarin 3-H), 4.28–4.23 (t, 4H,coumarin-OCH2),
4.00–3.96 (t, 4H, triazole-CH2), 2.47 (s, 3H, coumarin-CH3), 2.14–2.07 (m, 4H,
coumarin-OCH2CH2), 1.89–1.75 (m, 4H, triazole-OCH2CH2) ppm; 13C NMR
(75 MHz, DMSO-d6) d: 160.8 (coumarin 2-C), 159.0 (coumarin 7-C), 157.0
(coumarin 5-C), 155.3 (coumarin 9-C), 153.0 (coumarin 4-C), 150.0 (2C, triazole
5-C), 142.0 (2C, triazole 3-C), 109.4 (coumarin 3-C), 102.9 (coumarin 10-C),
94.6 (coumarin 6-C), 92.3 (coumarin 8-C), 67.4 (2C, coumarin-OCH2), 47.7 (2C,
triazole-CH2), 28.1 (2C, coumarin-OCH2CH2), 27.2 (2C, triazole-CH2CH2), 22.9
(coumarin-CH3) ppm; MS (m/z): 461 [M+Na]+, 439 [M+H]+; HRMS (TOF) calcd
Acknowledgments
This work was partially supported by Natural Science Founda-
tion of Chongqing (CSCT: 2009BB5296, 2007BB5369) and South-
west University (SWUB2006018, XSGX0602).
for
22H26N6O4: C, 63.26; H, 5.98; N, 19.17. Found: C, 63.18; H, 5.99; N, 19.16.
C
22H27N6O4 [M+H]+, 439.2088; found, 439.2083; Anal. Calcd for
C
Synthesis of 5,7-bis(6-(1H-1,2,4-triazol-1-yl)hexyloxy)-4-methyl-2H-chromen-2-
one (7c). Compound 7c was prepared according to the experimental procedure
for compound 6d. Starting from compound 5c (2.58 g, 5 mmol), triazole
(0.83 g, 12 mmol), potassium carbonate (1.67 g, 12 mmol) and CH3CN (30 mL),
the crude product was obtained and purified by chromatography (chloroform/
methanol, 6/1, V/V) to give compound 7c (1.95 g) as white solid. Yield 79%; mp
References and notes
1. Wu, L.; Wang, X.; Xu, W.; Farzaneh, F.; Xu, R. Curr. Med. Chem. 2009, 16, 4236.
2. (a) Riveiro, M. E.; Kimpe, N. D.; Moglioni, A.; Vazquez, R.; Monczor, F.; Shayo, C.;
Davio, C. Curr. Med. Chem. 2010, 17, 1325; (b) Kulkarni, M. V.; Kulkarni, G. M.;
Lin, C. H.; Sun, C. M. Curr. Med. Chem. 2006, 13, 2795; (c) Curini, M.; Cravotto,
M.; Epifano, F.; Giannone, G. Curr. Med. Chem. 2006, 13, 199.
3. Borges, F.; Roleira, F.; Milhazes, N.; Santana, L.; Uriarte, E. Curr. Med. Chem.
2005, 12, 887.
4. (a) Bradbury, B. J.; Pucci, M. J. Curr. Opin. Pharmacol. 2008, 8, 574; (b) Mitscher,
L. A. Chem. Rev. 2005, 105, 559.
79–80 °C; IR (KBr)
1602, 1512, 1490 (aromatic frame), 1249, 1225, 1208, 1145, 1116, 879, 860,
848, 842, 804, 745, 646 cmÀ1 1H NMR (300 MHz, CDCl3) d: 8.07 (s, 2H, triazole
m: 3121, 3090 (Ar-H), 2983, 2957 (CH2), 1709 (C@O), 1620,
;
3-H), 7.94 (s, 2H, triazole 5-H), 6.36 (s, 1H, coumarin 6-H), 6.20 (s, 1H, coumarin
8-H), 5.93 (s, 1H, coumarin 3-H), 4.23–4.19 (t, 4H,coumarin-OCH2), 3.96–3.94
(t, 4H, triazole-CH2), 2.47 (s, 3H, coumarin-CH3), 1.97–1.92 (m, 4H, coumarin-
OCH2CH2), 1.88–1.82 (m, 4H, triazole-OCH2CH2), 1.51–1.47 (m, 8H, coumarin-
OCH2CH2CH2CH2) ppm; 13C NMR (75 MHz, CDCl3) d: 162.2 (coumarin 2-C),
161.0 (coumarin 7-C), 158.2 (coumarin 5-C), 156.8 (coumarin 9-C), 154.2
(coumarin 4-C), 151.9 (2C, triazole 5-C), 142.9 (2C, triazole 3-C), 111.3
(coumarin 3-C), 104.6 (coumarin 10-C), 96.1 (coumarin 6-C), 93.8 (coumarin
8-C), 68.5 (2C, coumarin-OCH2), 49.2 (2C, triazole-CH2), 29.1 (2C, coumarin-
OCH2CH2), 28.6 (2C, triazole-CH2CH2), 24.3 (2C, coumarin-OCH2CH2CH2), 23.2
(2C, triazole-CH2CH2CH2), 22.9 (coumarin-CH3) ppm; MS (m/z): 517 [M+Na]+,
495 [M+H]+; HRMS (TOF) calcd for C26H35N6O4 [M+H]+, 495.2720; found,
495.2724; Anal. Calcd for C26H34N6O4: C, 63.14; H, 6.93; N, 16.99. Found: C,
63.22; H, 4.89; N, 16.86.
5. Drlica, K.; Hiasa, H.; Kerns, R.; Malik, M.; Mustaev, A.; Zhao, X. Curr. Top. Med.
Chem. 2009, 9, 981.
6. Patrick, L.; Ferroud, D.; Klich, M.; Dupuis-Hamelin, C.; Mauvais, P.; Lassaigne,
P.; Bonnefoy, A.; Musicki, B. Bioorg. Med. Chem. Lett. 1999, 9, 2079.
7. (a) Ronad, P. M.; Noolvi, M. N.; Sapkal, S.; Dharbhamulla, S.; Maddi, V. S. Eur. J.
Med. Chem. 2010, 45, 85; (b) Keri, R. S.; Hosamani, K. M.; Shingalapur, R. V.;
Reddy, H. R. S. Eur. J. Med. Chem. 2009, 44, 5123; (c) Raghu, M.; Nagaraj, A.;
Reddy, C. S. J. Heterocycl. Chem. 2009, 46, 261.
8. Mi, J. L.; Zhou, C. H.; Bai, X. Chin. J. Antibiot. 2007, 32, 587 (in Chinese).
9. Bai, X.; Zhou, C. H.; Mi, J. L. Chem. Res. Appl. 2007, 19, 721 (in Chinese).
10. Fang, B.; Zhou, C. H.; Rao, X. C. Eur. J. Med. Chem. 2010, 45, 4388.
11. Wang, X. L.; Wan, K.; Zhou, C. H. Eur. J. Med. Chem. 2010, 45, 4631.
12. Wan, K.; Zhou, C. H. Bull. Korean Chem. Soc. 2010, 31, 2003.
13. Zhang, F. F.; Gan, L. L.; Zhou, C. H. Bioorg. Med. Chem. Lett. 2010, 20, 1881.
14. Luo, Y.; Lu, Y. H.; Gan, L. L.; Zhou, C. H.; Wu, J.; Geng, R. X.; Zhang, Y. Y. Arch.
Pharm. 2009, 342, 386.
Synthesis of 7-(4-(1H-1,2,4-triazol-1-yl)butoxy)-4-methyl-2H-chromen-2-one
hydrochloride (8a). To a solution containing compound 6a (0.60 g, 2 mmol) in
ethyl ether/chloroform (4/1, V/V, 10 mL), diluted hydrochloric acid (4 mol/L)
was added dropwise until no more precipitate formed. The precipitate was
filtered and washed with chloroform to afford hydrochloride 8a (0.67 g) as
15. Emami, S.; Foroumadi, A.; Falahati, M.; Lotfali, E.; Rajabalian, S.; Soltan-Ahmed,
E.; Farahyar, S.; Shafiee, A. Bioorg. Med. Chem. Lett. 2008, 18, 141.
16. Experimental: Melting points are uncorrected and were determined on X-6
melting point apparatus. IR spectra were determined on a Bio-Rad FTS-185
white solid. Yield 99%; mp 152–154 °C; IR (KBr)
2794 (CH2), 1711 (C@O), 1607, 1566, 1543 (aromatic frame), 1349, 1269, 1204,
1158, 1045, 907, 849, 812, 804, 750, 646, 623 cmÀ1 1H NMR (400 MHz, DMSO-
m: 3088, 3026 (Ar-H), 2919,
;
d6) d: 8.77 (s, 1H, triazole 3-H), 8.17 (s, 1H, triazole 5-H), 7.69–7.67 (d, 1H,
coumarin 5-H), 6.95–6.93 (d, 1H, coumarin 6-H), 6.91 (s, 1H, coumarin 8-H),
6.21 (s, 1H, coumarin 3-H), 4.41–4.38 (t, 2H, coumarin-OCH2), 4.09–4.06 (t, 2H,
triazole-CH2), 2.38 (s, 3H, coumarin-CH3), 2.26–2.22 (d, 2H, coumarin-
OCH2CH2), 2.19–2.14 (d, 2H, triazole-CH2CH2) ppm; 13C NMR (100 MHz,
DMSO-d6) d: 162.4 (coumarin 2-C), 159.3 (coumarin 7-C), 155.7 (coumarin 9-
C), 154.7 (coumarin 4-C), 152.0 (triazole 3-C), 143.6 (triazole 5-C), 127.9
(coumarin 5-C), 113.4 (coumarin 3-C), 112.8 (coumarin 10-C), 112.1 (coumarin
6-C), 108.2 (coumarin 8-C), 68.7 (coumarin-OCH2), 45.9 (triazole-CH2), 33.1
(coumarin-OCH2CH2), 30.8 (triazole-CH2CH2), 20.2 (coumarin-CH3) ppm; MS
spectrophotometer in the range of 400–4000 cmÀ1 1H NMR and 13C NMR
.
spectra were recorded on a Bruker AV 300 or Varian 400 spectrometer using
TMS as an internal standard. The mass spectra were confirmed on FINIGAN
TRACE GC/MS and HRMS. Elemental analyses were carried out on Carlo Erba
model EA 1106 elemental analyzer. Some characteristics were given for some
representative compounds.
Synthesis of 7-(4-((1H-1,2,4-triazol-1-yl)methyl) benzyloxy)-4-methyl-2H-
chromen-2-one (6d). A mixture of triazole (0.42 g, 6 mmol) and potassium
carbonate (0.83 g, 6 mmol) in CH3CN (20 mL) was stirred for 1 h at room

960
Y. Shi, C.-H. Zhou / Bioorg. Med. Chem. Lett. 21 (2011) 956–960
(m/z): 299 [MÀHCl]+; HRMS (TOF) calcd for C16H18ClN3O3 [MÀHCl]+, 299.1270;
DMSO-d6) d: 161.2 (coumarin 2-C), 158.8 (coumarin 7-C), 156.1 (coumarin 5-
C), 154.9 (coumarin 9-C), 152.7 (coumarin 4-C), 150.8 (2C, triazole 5-C), 141.7
(2C, triazole 3-C), 109.2 (coumarin 3-C), 103.0 (coumarin 10-C), 94.5 (coumarin
6-C), 92.0 (coumarin 8-C), 68.1 (2C, coumarin-OCH2), 47.5 (2C, triazole-CH2),
27.9 (2C, coumarin-OCH2CH2), 27.4 (2C, triazole-CH2CH2), 22.9 (coumarin-CH3)
ppm; MS (m/z): 438 [MÀ2HCl]+; HRMS (TOF) calcd for C22H28Cl2N6O4
[MÀ2HCl]+, 438.2016; found, 438.2018; Anal. Calcd for C22H28Cl2N6O4: C,
51.67; H, 5.52; N, 16.43. Found: C, 51.54; H, 5.48; N, 16.49.
found, 299.1269; Anal. Calcd for C16H18ClN3O3: C, 57.23; H, 5.40; N, 10.56.
Found: C, 57.28; H, 5.36; N, 10.59.
Synthesis of 5,7-bis(4-(1H-1,2,4-triazol-1-yl)butoxy)-4-methyl-2H-chromen-2-
one dihydrochloride (9a). According to the synthetic procedure of compound
8a, hydrochloride 9a was prepared starting from bis-triazole 7a (0.88 g,
2 mmol). The hydrochloride 9a (1.00 g) was obtained as white solid. Yield 98%;
mp 220–222 °C; IR (KBr)
1643, 1610, 1509, 1487 (aromatic frame), 1356, 1208, 1100, 1001, 911, 833,
796, 731, 698 cmÀ1 1H NMR (300 MHz, DMSO-d6) d: 8.91 (s, 2H, triazole 3-H),
m: 3099, 3021 (Ar-H), 2926, 2875 (CH2), 1706 (C@O),
17. National Committee for Clinical Laboratory Standards Approved standard
Document. M27-A2, Reference Method for Broth Dilution Antifungal
Susceptibility Testing of Yeasts, National Committee for Clinical Laboratory
Standards, Wayne, PA, 2002.
;
8.24 (s, 2H, triazole 5-H), 6.89 (s, 1H, coumarin 6-H), 6.52 (s, 1H, coumarin
8-H), 6.11 (s, 1H, coumarin 3-H), 4.68–4.63 (t, 4H,coumarin-OCH2), 4.22–4.16
(t, 4H, triazole-CH2), 2.50 (s, 3H, coumarin-CH3), 2.20–2.16 (m, 4H, coumarin-
OCH2CH2), 2.09–2.03 (m, 4H, triazole-OCH2CH2) ppm; 13C NMR (75 MHz,