Synthesis and antibacterial activities of novel 4-hydroxy-7-hydroxy- and 3-carboxycoumarin derivatives

Article abstract of DOI:10.3390/molecules170910846

Coumarin derivatives are used as fluorescent dyes and medicines. They also have some notable physiological effects, including the acute hepatoxicity and carcinogenicity of certain aflatoxins, the anticoagulant action of dicoumarol, and the antibiotic activity of novobicin and coumerymycin A1. Because the number of drug resistant strains is increasing at present, the synthesis of new antibacterial compounds is one of the critical methods for treating infectious diseases. Therefore, a series of coumarinsubstituted derivatives, namely 4-hydroxy- and 7-hydroxycoumarins, and 3-carboxycoumarins were synthesized. 4-Hydroxycoumarin derivatives 4a-c underwent rearrangement reactions. Both 4- and 7-hydroxycoumarins were treated with activated aziridines which produced series of ring-opened products 7, 8, 10, and 11. 3-Carboxy-coumarin amide dimer derivatives 14-21 were prepared by reacting aliphatic alkylamines and alkyldiamines with PyBOP and DIEA. In this study, we use a new technique called modified micro-plate antibiotic susceptibility test method (MMAST), which is more convenient, more efficient, and more accurate than previous methods and only a small amount of the sample is required for the test. Some of the compounds were produced by reactions with acid anhydrides and demonstrated the ability to inhibit Gram-positive microorganisms. The dimer derivatives displayed lower antibacterial activities.

Full text of DOI:10.3390/molecules170910846

Molecules 2012, 17, 10846-10863; doi:10.3390/molecules170910846
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis and Antibacterial Activities of Novel
4-Hydroxy-7-hydroxy- and 3-Carboxycoumarin Derivatives
Pen-Yuan Lin 1, Kuang-Sheng Yeh 2, Chien-Ling Su 3, Shiow-Yunn Sheu 1, Tiffany Chen 4,
Keng-Liang Ou 5, Mei-Hsiang Lin 1 and Lin-Wen Lee 6,*
1
School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wuxing St.,
Taipei 11031, Taiwan
2
Department of Veterinary Medicine, School of Veterinary Medicine, College of Bioresources and
Agriculture, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan
3
School of Respiratory Therapy, Taipei Medical University, Taipei Medical University,
250 Wuxing St., Taipei 11031, Taiwan
4
Department of Biochemistry and Chemistry, University of Washington, 4311 11th Ave. NE,
Seattle, WA 98105-4068, USA
5
Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University,
250 Wuxing St., Taipei 11031, Taiwan
6
Department of Microbiology and Immunology, School of Medicine, College of Medicine,
Taipei Medical University, 250 Wuxing St., Taipei 11031, Taiwan
* Author to whom correspondence should be addressed; E-Mail: lucie@tmu.edu.tw;
Tel.: +886-227-361-661 (ext. 3917); Fax: +886-229-278-316.
Received: 29 June 2012; in revised form: 20 August 2012 / Accepted: 3 September 2012 /
Published: 10 September 2012
Abstract: Coumarin derivatives are used as fluorescent dyes and medicines. They also
have some notable physiological effects, including the acute hepatoxicity and
carcinogenicity of certain aflatoxins, the anticoagulant action of dicoumarol, and the
antibiotic activity of novobicin and coumerymycin A1. Because the number of drug
resistant strains is increasing at present, the synthesis of new antibacterial compounds is
one of the critical methods for treating infectious diseases. Therefore, a series of coumarin-
substituted derivatives, namely 4-hydroxy- and 7-hydroxycoumarins, and 3-carboxycoumarins
were synthesized. 4-Hydroxycoumarin derivatives 4a–c underwent rearrangement
reactions. Both 4- and 7-hydroxycoumarins were treated with activated aziridines which
produced series of ring-opened products 7, 8, 10, and 11. 3-Carboxy-coumarin amide
dimer derivatives 14–21 were prepared by reacting aliphatic alkylamines and

Molecules 2012, 17
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alkyldiamines with PyBOP and DIEA. In this study, we use a new technique called
modified micro-plate antibiotic susceptibility test method (MMAST), which is more
convenient, more efficient, and more accurate than previous methods and only a small
amount of the sample is required for the test. Some of the compounds were produced by
reactions with acid anhydrides and demonstrated the ability to inhibit Gram-positive
microorganisms. The dimer derivatives displayed lower antibacterial activities.
Keywords: 4-hydroxy-; 7-hydroxy-; 3-carboxycoumarin derivatives; antibacterial activities
1. Introduction
Coumarin is a lactone compound which is widely distributed in plants and can be extracted, among
others, from Anthoxanthum odoratum, Melilotus officinalis, Dipterix oppositifolia and Dipterix
oppositifolia [1]. Its derivatives are used as daylight fluorescent pigments [2], brighteners [3],
fluorescent dyes [4], fluorescent sensors [5], laser dyes [6], drug carriers [7], and drug delivery agents [8].
Recently, various medicinal effects, such as anticoagulant [9,10], analytical fluorescence indicator,
anti-inflammatory [11] and antioxidant [12–15] properties have been reported. Many authors have
reported the convenient and effective synthesis of the dimers from salicylaldehydes and by biomimetic
synthesis. Acetoxycoumarins, polycyclic 7-hydroxycoumarins and other coumarin derivatives
display anticarcinogenic properties [16–22]. Roma also reported that tricyclic or bicyclic coumarin
derivatives with amino groups showed antiplatelet activity [23]. 4-Heteroarylamino-, triazolopyridine,
imidazolopyridine, N-substituted-3-carboxamido- and other groups incorporate a coumarin moiety
displaying new coumarin derivative structures which showed antibacterial [24–29] and antifungal [30]
activities. Several novel coumarin analogs possess antimycobacterial activity [31–33]. Modification of
the chemical structure of the coumarin parent skeleton showed unit enzyme inhibition in vitro and
in vivo [34–37]. Coumarin also combines with sugar units to form C-glycosyl compounds. In this
study, we report the characteristics of several chemicals including 4-hydroxycoumarin derivatives 1a–c,
5, and 7-hydroxycoumarin 9 and 3-carboxycoumarin derivatives 12. By using acid anhydrides,
activated aziridines 6, benzotriazol-1-yloxtri-(pyrrolidinol)phosphonium hexafluorophosphate (PyBOP,
13), diisopropylethylethylamine (DIEA), dimethylformamide (DMF), alkylamines, and alkyldiamines
to react with 3-carboxycoumarin, instead of dicyclohexylcarbodiimide (DCC) as a coupling reagent
high yields of 3-carboxycoumarin amide dimers were obtained.
Microbiological trials using the minimal inhibitory concentration (MIC) on penicillin G, amikin and
the new modified micro-plate antibiotic susceptibility test (MMAST) were carried out on different
bacterial strains to test the activities of the new compounds [38].
2. Results and Discussion
Acylation of 1a–c with acid anhydride in a suitable solvent at ca. 150 °C caused the substitution to
produce 3a–c, 3a1–c1 and 3a2–c2. The acyl groups were removed via rearrangement to produce
compounds 4a–c, 4a1–c1, and 4a2–c2 under heating conditions. 4-Acyloxycoumarins experienced a

Molecules 2012, 17
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greater extent of rearrangement than 7-acyloxycoumarins. The effects might have been due to an
electron deficiency inductive effect plus the different distances between position 7-acyloxy and the
non-aromatic double-bond electron density at positions 3 and 4 of the 4-acyloxycoumarins. In this
study, only the aliphatic acid anhydride acylation of 4-hydroxycoumarin caused rearrangements, while
aromatic acid anhydrides failed to react. For 7-hydroxycoumarin, its acylation product was not
observed, even when aliphatic or aromatic acid anhydrides with NaOMe in methanol were used. When
7-hydroxycoumarin treated with base will become more resonance anion and more difficult to react
with anhydride by weak base MeOH and even by strong base NaOMe. Therefore both of bases are
unable to carry out the reaction. We also tried to use other diketone and amide compounds to react
with the hydroxycoumarins, unfortunately, the expected acylation rearrangement did not occur. This
might be explained by the greater number of methylene groups and the increase in the distance
between the two C=O bonds which makes it more difficult to attack the other carbonyl position.
Synthesis of coumarin derivatives via the ring-opening reaction with activated aziridines has not been
reported and characterized previously. The reaction of the coumarin anion with N-benzoyl- or
N-sulfonylaziridines 6 yielded amidoethylated 7- or 4-hydroxycoumarins 7, 8, 9 and 10. The final
results depend on the substitution of the N-acyl or N-sulfonyl groups on the acyl group, such as
benzoyl and the coumarin anions will attack from an abnormal position to provide the major products
7d–f, 10n, and 10q. Only trace amounts of products are produced from normal ring-openings of
aziridines. However, with the N-sulfonyl group, we obtained both products (in 4:1 ratio), but the main
products resulted from normal ring-opening of the activated aziridines 7h, 8i, 8j, 10k–l, and 11k. It
was assumed that compounds 7, 8, 10, 11, and their analogues were formed by the nucleophilic attack
of acylaziridines via an SN2-like ring opening mechanism. The comparison of the proton NMR of the
NH group in 7 and 8 revealed the cleavage of the ring position.
In our previous work [35], we reported that when PyBOP (13) was used as a coupling reagent to
synthesize natural amide dimers, relatively high yields was obtained. The reaction did not perturb the
formation of amide dimers even when a sugar moiety is attached to the parent compounds. In general,
for the formation of amide or dimer chains, the reaction temperatures had a great influence on the
structural conformation. From NMR spectroscopic analysis, the intermediate, coumarin-triazobenzene,
displayed rearranged characteristics. We hypothesize that it might depend on the two factors of the
solvent system introduced and the duration of the reaction. The reaction was carried out under mild
conditions, by mixing the reagents with DMF at ca. 0 °C, followed by the addition of DIEA. The
resulting solution was allowed to warm to room temperature for 1–3 days, then alkyldimines were
added dropwise to produce high yields of coumarin amide dimers.
All of the above synthetic products were further tested for their antibacterial effects. The MICs of
the compounds tested against the reference strains are shown in Table 1. The antimicrobial tests
performed on coumarin derivatives 3c, 3c1, 4a2, 4b, 4c, and 7f confirmed the better activities of these
compounds against Gram-positive rather than Gram-negative bacteria and some were especially active
against Bacillus subtilis and Staphylococcus aureus. Compound 7f was the most potent of the tested
compounds against B. subtilis, with an MIC value of 8 μg/mL. Compounds 3c, 3c1, 4a2, 4b, 4c, and 7d
only inhibit bacterial growth moderately, with lower MICs of 32, 16, and 64 μg/mL, respectively,
when compared to penicillin G. The MICs of coumarin amide dimers 14–21 ranged from 128 to 256.
Prior to these studies, the available information on coumarin-aziridins and the dimerization moiety of

Molecules 2012, 17
10849
SAR indicated that molecular recognition involved specific receptor interactions. We propose that the
various aziridines and dimer chain lengths might change the binding characteristics of ligands or the
conformational direction to their respective receptors and, thereby, improve the biological activities.
Table 1. MICs of compounds 3, 4, 7, 8, 10, 11, and 14–21 against the reference strains.
MIC (g/mL) a
Gram (+) bacteria b
Gram (−) bacteria b
P. a.
Compds.
3a
B. s.
S. a.
>256
>256
>256
>256
256
E. c.
>256
>256
>256
128
>256
>256
128
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>256
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
3a1
3a2
3b
128
3b1
3b2
3c
128
256
>256
32
>256
32
>256
>256
>256
>256
>256
>256
>256
256
3c1
3c2
4a
32
>256
>256
>256
>256
>256
128
>256
128
4a1
4a2
4b
>256
64
64
4b1
4b2
4c
>256
128
>256
>256
16
>256
>256
128
16
4c1
4c2
7d
>256
64
>256
32
>256
>256
>256
>256
>256
>256
>256
>256
>256
128
64
64
7e
>256
8
>256
8
7f
7g
>256
>256
>256
>256
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>256
>256
>256
>256
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
7h
8i
8j
10k
10l
10m
10n
10o
10p
10q
10r
11k
14
>128
128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
15
16
17

Molecules 2012, 17
10850
Table 1. Cont.
MIC (g/mL) a
Gram (+) bacteria b
Gram (−) bacteria b
Compds.
B. s.
>128
>128
>128
>128
8
S. a.
>128
>128
>128
>128
0.0625
-
E. c.
>128
>128
>128
>128
-
P. a.
>128
>128
>128
>128
-
18
19
20
21
PenicillinG c
Amikin
-
1
0.125
a
MIC, minimal inhibitory concentration .b Bacteria: B. s., Bacillus subtilis (BCRC 10029); S. a.,
Staphylococcus aureus (BCRC 11863); E. c., Escherichia coli (BCRC 11758); P. a., Pseudomonas
aeruginosa (BCRC 11733). c Penicillin G potassium salt, Sigma p8721, lot 102K0483, 1,589 units/mg.
2.1. Chemistry
Regarding the synthetic route applied to 4-hydroxycoumarin derivatives, 4-hydroxycoumarin and
its analogues 1a–c were used as starting materials to react with acid anhydrides, acetic anhydride, e.g.,
propionic anhydride, and benzoic anhydride, to produce the corresponding O-acyloxyl products 3a–c.
It was observed that a proton on the hydroxyl group of coumarin was substituted by an acyl group
when we elevated the temperature to ca. 150 °C. Similar conditions were adopted to produce the
O-acyloxyl and benzoyloxyl derivatives as the main reaction products. High yields were achieved
when methyl groups were introduced at the 6 and 7 positions of the parent coumarin structure (Scheme 1).
Scheme 1. 4-Hydroxycoumarin reacted with acid anhydride.
OH
OCOR
R1
O
O
R1
C
R
R
R
R
+
R
______1______2____________
C
3a
3b
3c
H
CH3
CH3 CH3
OCH3 CH3
O
R2
O
O
O
O
H
CH3
CH3
R2
3a1
3b1 CH3
H
OCH3 C2H5
C2H5
3c1 CH3 CH3 C2H5
3a2 OCH3 Ph
3b2 CH3
3c2 CH3 CH3
1a R1 = H, R2 = OCH3
1b R1 = CH3, R2 = H
1c R1 = CH3, R2 = CH3
2
R = CH3
R = Ph
R = C2H5
3
H
H
i
H
Ph
Ph
R
R
R
_____1_____2___________
OH
R1
`4a
4b
H
CH3
OCH3 CH3
CH3
COR
H
4c
CH3 CH3 CH3
4a1
4b1
4c1
4a2
4b2
4c2
H
CH3
OCH3 C2H5
C2H5
O
O
H
R2
CH3 CH3 C2H5
H
CH3
CH3 CH3
OCH3 Ph
4
H
Ph
Ph
Reaction Conditions: i. reflux.

Molecules 2012, 17
10851
The subsequent reaction involving heating over 170 °C in a sealed tube led to the rearrangement
products 4a–c in yields comparable to compounds 3a–c. Methyl group substitution produced greater
yields of 52%–64%. Excess acid anhydrides were finally removed by column chromatography on
silica gel. Furthermore, 4-hydroxy- and 7-hydroxycoumarin derivatives were found to undergo
ring-opening reactions with various activated aziridines (Schemes 2 and 3).
Scheme 2. 4-Hydroxycoumarin reacted with activated aziridines 6.
Reagents: i. NaOCH3/THF.
Scheme 3. Reactions of 7-hydroxycoumarin with activatived aziridines 6.
Reagents: i. K2CO3/acetone.

Molecules 2012, 17
10852
These new and convenient approaches to the synthesis of 4-hydroxy-, 7-hydroxycoumarins or other
hydroxycoumarin derivatives were apparently caused by the nucleophilic attack on the activated
aziridine rings. We used two hydroxycoumarins as starting materials in refluxing tetrahydrofuran (THF)
and acetone in the presence of a base (NaOCH3 or K2CO3) for 2–3 h to form “coumarin 5-O” and
“coumarin 9-O” [the anions of 4-hydroxycoumarin (5) and 7-hydroxycoumarin (9)], and then reacted
them with various activated aziridines. It was found that two isomers 7, 8 or 10, 11 were produced
from each hydroxycoumarin in yields of 28%–88%. The main products generated from
N-benzoylaziridines (X = C) were produced by abnormal regioselective ring-opening reactions
producing 7d–g, 10m–n, and 10q with strongly preferred cleavage of the N–CH2 bond. In the similar
reactions with tolylaziridines (X = SO), a mixture of normal regioselectivity ring-opening products 7h,
8i–j, 10k–l, and 11k were observed to predominate.
The syntheses of some coumarin dimers using Mn(III) or Fe(III) in the presence of a strong acid to
obtain high yields were reported. We reacted coumarin acid 12 with diamines (n = 3–12) in the
presence of PyBOP, DIEA, and dimethylformamide at room temperature or 60 °C with stirring for 18 h.
The excess solvent, DIEA, and alkyldiamines were removed by column chromatography on silica gel
to provide coumarin amide dimers 14–21 in excellent yields (82%–87%). The products were
recrystallized from ether and methanol (Scheme 4). The yields of dimers seem not to be affected by the
bulky PyBOP reagent and essentially no steric hindrance between diamines and coumarins was
observed. The chemical structures of these products were established using spectroscopic methods
1
13
including IR, H-, C-NMR, FAB-MS, HR-FAB-MS, and LC/MS/MS (ESI). The IR spectra of these
1
amide dimers showed the C=O absorption peaks around 1647–1665 cm−1. In the H-NMR (in CDCl3)
the amide N–H absorption appeared at δ 8.79–8.92 ppm as a broad singlet. The ethylene amide dimers
13
of coumarins revealed doublet of doublet signals at δ 3.47 ppm (–NH–CH2–). C-NMR showed the
amide (NH–C) signal at δ 161.4–161.8 ppm in the parent compounds.
Scheme 4. 3-Carboxycoumarin reactions with alkyldiamines.
Reagents: i, DIEA/THF; ii, 3-coumaric acid/THF, alkyldiamine.

Molecules 2012, 17
10853
2.2. Antibacterial Activity Test
Acyl coumarins 3a–4c, 4-hydroxy-, and 7-hydroxycoumarins 7–11 and coumaric amide dimers 14–21
were tested against reference strains of Bacillus subtilis (BCRC 10029), Staphylococcus aureus
(BCRC 11863), Escherichia coli (BCRC 11758), and Pseudomonas aeruginosa (BCRC 11733)
obtained from The Bioresources Collection & Research Center (BCRC), Taiwan. Penicillin G
potassium salt (CAS 113-98-4, USP grade) was used as a reference and purchased from Sigma-Aldrich
(St. Louis, MO, USA). Bacteria were grown overnight in Müller-Hinton broth (Difco, Detroit, MI,
USA) and trypticase soy broth (TSB, Oxoid, Basingstoke, Hampshire, UK).
The minimal inhibitory concentrations (MICs) of all synthesized compounds were determined using
the reference method of broth dilution measurements. Each test compound and penicillin G was
dissolved in DMSO/EtOH/phosphate buffer or phosphate buffer before a serial two-fold dilution to the
desired test concentration ranges. DMSO/EtOH/phosphate buffer and phosphate buffer were used for
the solvent control test. The seed was cultured with trypticase soy broth containing 107 colony forming
units (cfu)/mL. Müller-Hinton broth was sterilized by autoclaving at 120 °C for 15 min, and
microorganism were suspended in 96-well microplate. The final concentration of microorganism in
each well was 105 cfu/mL. Modified 96-well plates were used with a two-fold micro-dilution method
of the MTT assay in Müller-Hinton broth. Microorganism suspensions containing 105 cfu/mL were
inoculated onto the 96-well microplates and mixed with the test compounds. The MIC was defined as
the lowest concentration of test compounds, allowing no visible growth of test strain bacteria after
incubation at 37 °C for 3 h. Then SDS in 0.1 N HCl was added. The absorbance was measured by
ELISA reader (Bio-Tek Instruments, Microplate Autoreader, EL 311) at 595 nm.
3. Experimental
3.1. General
The IR spectra were recorded on a Thermo Mattson IR300 and Nicolet 510 PET spectrometers.
Optical rotations were measured with a JASCO p-1020 digital polarimeter. NMR spectra were
recorded at 500 (1H-NMR) and 125 MHz (13C-NMR) on a Bruker DRX-500 spectrometer in CDCl3 or
DMSO solution with respect to the corresponding solvent peak used as the internal standard. Mass
spectra were measured on a Finnigan/Thermo Quest NAT 95XL, JEOL JMX-HX 110, JEOL JMSHX
110 FAB-MS, and LC/MS/MS Micromass Quattro II. The compounds were prepared according to
similar procedures, and reactions took place in high-pressure tubes (Büchiglasuster, bursting disc,
0032). For the chromatographic analysis, Merck silica gel 60 was used. The chemical reagents used in
the synthesis were purchased from Sigma-Aldrich and Merck. The crude products were purified by
column chromatography and recrystallized using ether/methanol or n-hexane/methanol. Biological
data were recorded on a Microplate Autoreader EL 311.
3.2. Preparation of Acylcoumarins
4-Hydroxycoumarin and its derivatives 1a–c were added to a high-pressure tube (Bursting disc,
Büchiglasuster) containing of acid anydride 2. The solution was stirred for 2 h at 150 °C. The dried

Molecules 2012, 17
10854
mass was separated by column chromatography (CHCl3/EA/n-hexane = 8:1:1) to give compounds 3a–c.
Next the solution was stirred at 180 °C and purified by column chromatography to obtaine the
rearranged compounds 4a–c.
3.3. Preparation of 4-hydroxy-, and 7-hydroxycoumarin Derivatives via Ring Opening of Activated
Aziridines
Synthesis of 4-hydroxy-, and 7-hydroxycoumarin derivatives with activated aziridines are shown in
Schemes 2 and 3. Compound 5 was dissolved in dry acetone, CH3ONa and then added activated
aziridine. The mixture was stirred at 130 °C, and dry mass was purified by column chromatography
(CHCl3/EA = 9:1) for compounds 7 and 8. Compound 9 was dissolved in dry acetone then added
K2CO3 with same procedure for compounds 10 and 11.
3.4. Preparation of Coumarin Amide Dimers
Synthesis of the desired amide dimer derivatives of coumarin acid with alkyldiamines is shown in
scheme 4. The PyBOP coupling reagent was used to prepare a series of coumarin acid amide dimers
under mild conditions. Compound 12 was dissolved in dry dimethylformamide (DMF) then
added various alkyldiamines. When the mixtures were cooled PyBOP solution DMF and
diisopropylethylamine (DIEA) was added. After the mixture was allowed to warm to
room temperature and stirred for 18 h the residues were purified by column chromatography
(CHCl3/acetone = 10:1) for compounds 14–21.
4-O-Acetyl-7-methoxycoumarin (3a). M.p. 131~134 °C. 1H-NMR (CDCl3) δ: 2.40 (3H, s), 3.86 (3H, s),
6.82 (1H, d, J = 2.1 Hz), 6.84 (1H, dd, J = 7.6, 2.1 Hz), 7.47 (1H, d, J = 7.6 Hz), IR (KBr, cm−1) 1656
(C = O), 1721 (lactone).
4-O-Acetyl-6-methylcoumarin (3b). M.p. 128–130 °C. 1H-NMR (CDCl3) δ: 2.45 (3H, s), 2.47 (3H, s),
6.32 (1H, s), 7.26 (1H, d, J = 7.5 Hz), 7.46 (1H, dd, J = 7.5, 2.1 Hz), IR (KBr, cm−1) 1645, 1680 (C=O).
1
4-O-Acetyl-6,7-dimethylcoumarin (3c). M.p. 157–159 °C. H-NMR (CDCl3) δ: 2.35 (3H, s), 2.36
(3H, s), 2.42 (3H, s), 6.27 (1H, s), 7.13 (1H, s), 7.67 (1H, s). IR (KBr, cm−1) 1657, 1720 (C=O).
4-O-Propionyl-7-methoxycoumarin (3a1). M.p. 176–177 °C. 1H-NMR (CDCl3) δ: 1.53 (3H, t, J = 7.6 Hz),
2.45 (2H, q, J = 7.6 Hz), 3.86 (3H, s), 6.50 (1H, dd, J = 8.3, 2.4 Hz), 7.69 (1H, J = 8.3 Hz). IR (KBr)
1645, 1748 (C=O) cm−1.
4-O-Propionyl-6-methylcoumarin (3b1). M.p. 154–156 °C. 1H-NMR (CDCl3) δ: 1.22 (3H, t, J = 7.6 Hz),
2.43 (3H, s), 3.22 (2H, q, J = 7.6 Hz), 7.04 (1H, s), 7.20 (1H, d, J = 7.9 Hz), 7.47 (1H, dd, J = 7.9, 1.9 Hz),
7.84 (1H, s). IR (KBr, cm−1) 1634, 1701 (C=O).
1
4-O-Propionyl-6,7-dimethylcoumarin (3c1). M.p. 167–168 °C. H-NMR (CDCl3) δ: 1.32 (3H, t,
J = 7.5 Hz), 2.31 (3H, s), 2.35 (3H, s), 2.72 (2H, q, J = 7.5 Hz), 6.41 (1H, s), 7.14 (1H, s), 7.30 (1H, s).
IR (KBr, cm−1) 1646, 1711 (C=O). MS m/z (rel. int %): 246 (M)+ (14), 190 (51), 148 (78), 91 (20),
57 (100).

Molecules 2012, 17
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4-O-Benzoyl-7-methoxycoumarin (3a2). M.p. 147–148 °C. 1H-NMR (CDCl3) δ: 3.87 (3H, s), 6.42 (1H, s),
6.84 (1H, d, J = 2.2 Hz), 6.84 (1H, dd, J = 7.5, 2.2 Hz), 7.54 (1H, d, J = 7.5 Hz), 7.54 (2H, t, J = 7.5 Hz),
7.68 (1H, t, J = 7.5 Hz), 8.20 (2H, d, J = 7.5 Hz). IR (KBr, cm−1) 1640, 1710 (C=O). MS m/z (rel. int %):
296 (M)+ (2), 105 (1), 77 (40), 51 (20).
4-O-Benzoyl-6-methylcoumarin (3b2). M.p. 126–128 °C. 1H-NMR (CDCl3) δ: 2.41 (3H, s), 6.56 (1H, s),
7.29 (1H, d, J = 8.4 Hz), 7.39 (1H, dd, J = 8.4, 2.1 Hz), 7.44 (1H, d, J = 2.1 Hz), 7.58 (2H, t, J = 7.7 Hz),
7.72 (1H, t, J = 7.7 Hz), 8.24 (2H, d, J = 7.7 Hz). IR (KBr, cm−1) 1645, 1720 (C=O).
4-O-Benzoyl-6,7-dimethylcoumarin (3c2). M.p. 163–164 °C. 1H-NMR (CDCl3) δ: 2.26 (3H, d, J = 7.1 Hz),
2.33 (3H, d, J = 7.1 Hz), 6.46 (1H, s), 7.16 (1H, s), 7.35 (1H, s), 7.55 (2H, t, J = 7.9 Hz), 7.69 (1H, t,
J = 7.9 Hz), 8.21 (2H, d, J = 7.9 Hz). IR (KBr, cm−1) 1665, 1728 (C=O).
1
3-Acetyl-4-hydroxy-7-methoxycoumarin (4a). M.p. 194–196 °C. H-NMR (CDCl3) δ: 2.73 (3H, s),
3.89 (3H, s), 6.72 (1H, d, J = 2.1 Hz), 6.85 (1H, dd, J = 8.9, 2.1 Hz), 7.92 (1H, d, J = 8.9 Hz). IR
(KBr, cm−1) 1661, 1753 (C=O), 3442 (OH). LC/MS/MS (ESI) m/z, (rel. int. %): 234.9(M)+ (20), 217.3
(–OH, 100), 192.9 (–acetyl, 62), 151.1 (74).
3-Acetyl-4-hydroxy-6-methylcoumarin (4b). M.p. 156–159 °C. 1H-NMR (CDCl3) δ: 2.43 (3H, s), 2.78
(3H, s), 7.19 (1H, d, J = 8.4 Hz), 7.48 (1H, dd, J = 8.4, 1.5 Hz), 7.84 (1H, s). IR (KBr) 1661, 1753
(C=O), 3410 (OH). LC/MS/MS (ESI) m/z, (rel. int. %) 243.2 (M+Na) (80), 203.1 (M+Na−OH, 90), 135.1
(100).
1
3-Acetyl-4-hydroxy-6, 7-dimethylcoumarin (4c). M.p. 168–170 °C. H-NMR (CDCl3) δ: 2.36 (3H, s),
2.41 (3H, s), 2.79 (3H, s), 7.11 (1H, s), 7.50 (1H, s). IR (KBr, cm−1) 1631, 1723 (C=O), 3419 (OH).
LC/MS/MS (ESI) m/z, (rel. int. %) 233.2 (M+H) (30), 215.1 (M+H−H2O), (100), 149.2 (60).
1
3-Acetyl-4-hydroxy-7-methoxycoumarin (4a1). M.p. 197–199 °C. H-NMR (CDCl3) δ: 1.32 (3H, t,
J = 7.6 Hz), 2.72 (2H, q, J = 7.6 Hz), 3.86 (3H, s), 6.79 (1H, d, J = 2.2 Hz), 6.90 (1H, dd, J = 7.8, 2.2 Hz),
7.83 (1H, d, J = 7.8 Hz). IR (KBr, cm−1) 1653, 1763 (C=O), 3438 (OH). LC/MS/MS (ESI) m/z, (rel.
int. %) 287.0 (M+K) (60), 272.1 (M+K−CH), (100), 257.3 (M+K−OCH3) (33), 244.1 (M+K−C3H7)
(90).
1
3-Propionyl-4-hydroxy-6-methylcoumarin (4b1). M.p. 191–192 °C. H-NMR (CDCl3) δ: 1.37 (3H, t,
J = 7.5 Hz), 2.47 (3H, s), 2.77 (2H, q, J = 7.1 Hz), 7.46 (1H, dd, J = 7.1, 2.1 Hz), 7.73 (1H, s), IR
(KBr, cm−1) 1652, 1759 (C=O). LC/MS/MS (ESI) m/z, (rel. int. %) 271.2 (M+K)+ (40), 256.0
(M+K−CH3)+ (60), 203.2 (70), 135.0(100).
1
3-Propionyl-4-hydroxy-6,7-dimethylcoumarin (4c1). M.p. 201–202 °C. H-NMR (CDCl3) δ: 1.34 (3H,
t, J = 7.6 Hz), 2.35 (3H, s), 2.37 (3H, s), 2.74 (2H, q, J = 7.6 Hz), 7.12 (1H, s), 7.65 (1H, s). IR (KBr,
cm−1) 1652, 1730 (C=O), 3400 (OH). LC/MS/MS (ESI) m/z, (rel. int. %) 285.1 (M+K)+ (80), 270.3
(M+K−CH3)+, 255.1 (23), 227.0 (18), 217.2 (70), 149.1 (100), 105.0 (18).

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1
3-Benzoyl-4-hydroxy-7-methoxycoumarin (4a2). M.p. 182–183 °C. H-NMR (CDCl3) δ: 3.89 (3H, s),
6.86 (1H, d, J = 2.3 Hz), 6.88 (1H, dd, J = 7.7, 2.3 Hz), 7.56 (1H, t, J = 7.7 Hz), 7.54 (2H, t, J = 7.8 Hz),
7.72 (1H, t, J = 7.8 Hz), 8.22 (2H, d, J = 7.8 Hz). IR (KBr, cm−1) 1650, 1714 (C=O), 3425 (OH).
1
3-Benzoyl-4-hydroxy-6-methylcoumarin (4b2). M.p. 176–178 °C. H-NMR (CDCl3) δ: 2.41 (3H, s),
7.29 (1H, d, J = 7.6 Hz), 7.40 (1H, dd, J = 7.6, 1.8 Hz), 7.46 (1H, s), 7.58 (2H, t, J = 7.7 Hz), 7.72 (1H,
t, J = 7.7 Hz), 8.24 (2H, d, J = 7.7 Hz). IR (KBr, cm−1) 1655, 1724 (C=O), 3445 (OH).
3-Benzoyl-4-hydroxy-6,7-dimethylcoumarin (4c2). M.p. 197–198 °C. 1H-NMR (CDCl3) δ: 2.30 (3H, d,
J = 7.1 Hz), 2.37 (3H, d, J = 7.1 Hz), 7.16 (1H, s), 7.38 (1H, s), 7.57 (2H, t, J = 7.7 Hz), 7.71 (1H, t,
J = 7.7 Hz), 8.24 (2H, d, J = 7.7 Hz). IR (KBr, cm−1) 1665, 1728 (C=O), 3480 (OH).
4-(N-Benzoylamino)ethoxycoumarin (7d). M.p. 172–173 °C. 1H-NMR (CDCl3) δ: 4.01 (2H, t, J = 5.2 Hz),
4.32 (2H, t, J = 5.2 Hz), 5.71 (1H, s), 6.53 (1H, s), 7.28 (1H, d, J = 7.7 Hz), 7.32 (1H, t, J = 7.7 Hz).
7.43 (2H, t, J = 8.2 Hz), 7.44 (1H, t, J = 7.7 Hz), 7.52 (1H, t, J = 8.2 Hz), 7.78 (1H, d, J = 7.7 Hz), 7.83
(2H, d, J = 8.2 Hz). IR (KBr, cm−1) 1653, 1730 (C=O), 3223 (NH). MS m/z (rel. int. %) 309 (2), 148
(91), 105 (100), 77 (95). HR-FAB-MS (EI, 80 eV) m/z, calculated for C18H15NO4 309.1001, found
309.1000.
1
4-[(N-Benzoylamino)-2-propoxyl]coumarin (7e). M.p. 193–194 °C. H-NMR (CDCl3) δ: 1.41 (3H, d,
J = 6.1 Hz), 3.79 (1H, dd, J = 6.4, 10.2 Hz), 3.94 (1H, dd, J = 3.8, 6.3, 10.2 Hz), 4.88 (1H, dd,
J = 6.4, 10.2 Hz), 5.78 (1H, s), 7.25 (1H, d, J = 7.3 Hz), 7.27 (1H, t, J = 7.3 Hz), 7.39 (1H, t,
J = 7.3 Hz), 7.42 (2H, t, J = 7.8 Hz), 7.78 (2H, d, J = 7.8 Hz). IR (KBr, cm−1) 1635, 1735 (C=O), 3214
(NH). MS m/z, (rel. int. %) 323 (1), 174 (25), 148 (48), 59 (100).
4-[(N-Benzoylamino)-2-methyl-2-propoxy]coumarin (7f). M.p. 198–200 °C. 1H-NMR (CDCl3) δ: 1.38
(3H, s), 3.88 (2H, d, J = 6.3 Hz), 5.87 (1H, s), 6.52 (1H, t-like), 7.27 (1H, J = 7.6 Hz), 7.29 (1H, t,
J = 7.6 Hz), 7.41 (1H, t, J = 7.6 Hz), 7.44 (2H, t, J = 7.9 Hz), 7.75 (1H, d, J = 7.6 Hz), 7.78 (1H, t,
J = 7.9 Hz), 7.79 2H, d, J = 7.9 Hz). IR (KBr, cm−1) 1648, 1742 (C=O), 3300 (NH). MS m/z, (rel. int. %)
337 (M)+ (1), 212 (21), 141 (25), 77 (100), 70 (90). HR-FAB-MS (EI, 80 eV) m/z, calculated for
C20H19NO4 337.1314, found 337.1322.
4-[(N-Ethylcarbamyl)ethyl]coumarin (7g). M.p. 123–124 °C. 1H-NMR (CDCl3) δ: 1.24 (3H, t, J = 6.5 Hz),
3.71 (2H, d, J = 5.1 Hz), 4.14 (2H, t, J = 5.1 Hz), 4.17 (2H, q, J = 6.5 Hz), 5.03 (1H, s), 5.68 (1H, s),
7.28 (1H, d, J =7.9 Hz), 7.31 (1H, t, J = 7.9 Hz), 7.54 (1H, t, J = 7.9 Hz), 7.80 (1H, d, J = 7.9 Hz). IR
(KBr, cm−1) MS m/z, (rel. int. %) 277 (10), 116 (80), 88 (100).
1
4-[(N-Benzosulfonyl)-1,1-dimethylethyl]coumarin (7h). M.p. 169–171 °C. H-NMR (CDCl3) δ: 1.61
(6H, s), 3.31 (2H, d, J = 6.8 Hz), 5.72 (1H, s), 7.23–7.29 (2H, dd, J = 8.1, 8.2 Hz), 7.54 (3H, dd,
J = 1.3, 7.4 Hz), 7.62 (2H, ddd, J = 1.2, 7.4, 7.8 Hz), 7.86 (2H, dd-like, J = 1.1, 7.2 Hz). IR (KBr,
cm−1) 1638, 1692 (C=O), 3200 (NH). HR-FAB-MS (EI, 80 eV) m/z, calculated for C19H19NO5S
373.0984, found 373.0986.

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4-[(N-p-Tolylsulfonyl)-2-methylethyl]coumarin (8i). M.p. 154–156 °C. 1H-NMR (CDCl3) δ: 1.28 (3H,
d, J = 6.8 Hz), 2.39 (3H, s), 3.83 (1H, m), 3.96 (2H, d, J = 3.8 Hz), 4.93 (1H, d, J = 7.7 Hz), 5.48 (1H, s),
7.21 (1H, d, J = 7.6 Hz), 7.23 (1H, t, J = 7.6 Hz), 7.29 (2H, d, J = 8.2 Hz), 7.53 (1H, t, J = 7.6 Hz),
7.65 (1H, d, J = 7.6 Hz), 7.72 (2H, d, J = 8.2 Hz). IR (KBr, cm−1) 1620, 1693 (C=O), 3172 (NH). MS
m/z, (rel. int. %) 373 (10), 218 (25), 155 (46), 91 (100). HR-FAB-MS (EI, 80 eV) m/z, calculated for
C19H19NO5S 373.0984, found 373.0986.
1
4-[(N-p-Tolylsulfonyl)-1,1-dimetylethyl]coumarin (8j). M.p. 187–190 °C. H-NMR (CDCl3) δ: 1.43
(3H, s), 2.23 (3H, s), 3.89 (2H, s), 4.97 (1H, s), 5.85 (1H, s), 7.07 (1H, d, J = 7.3 Hz), 7.28 (1H, t,
J = 7.3 Hz), 7.53 (1H, t, J = 7.3 Hz), 7.65 (2H, d, J = 7.5 Hz), 7.68 (1H, d, J = 7.3 Hz), 7.73 (2H, d,
J = 7.5 Hz). IR (KBr, cm−1) 1620, 1683 (C=O), 3425 (NH). MS m/z, (rel. int. %) 387 (M)+ (2), 212
(25), 155 (30), 91 (100), 70 (70).
1
7-[(N-p-Tosyl)-2,2-dimethylethyloxy]coumarin (10k). M.p. 220–221 °C. H-NMR (CDCl3) δ: 1.36
(6H, s), 2.45 (3H, s), 3.76 (2H, s), 4.91 (1H, s), 6.72 (1H, d, J = 9.5 Hz), 6.62 (1H, bs), 6.76 (1H, dd,
J = 8.5, 1.8 Hz), 7.18 (2H, d, J = 7.9 Hz), 7.36 (1H, d, J = 7.9 Hz), 7.63 (1H, d, J = 9.5 Hz), 7.74
(2H, d, J = 8.0 Hz). IR (KBr, cm−1) 1692 (C=O), 3406 (NH).
7-[(N-p-Tosyl)-2-methylethyloxy]coumarin (10l). M.p. 110–111 °C. 1H-NMR (CDCl3) δ: 1.15 (3H, s),
2.26 (3H, s), 3.62 (1H, t-like, J = 5.5 Hz), 3.73 (1H, dd, J = 5.1, 9.3 Hz), 3.81 (1H, dd, J = 4.9, 9.2 Hz),
5.87 (1H, d, J = 7.6 Hz), 6.12 (1H, d, J = 9.2 Hz), 6.50 (1H, bs), 6.58 (1H, d, J = 8.3 Hz), 7.13 (2H, d,
J = 7.7 Hz), 7.21 (1H, d, J = 8.5 Hz), 7.56 (1H, d, J = 9.5 Hz), 7.67 (2H, d, J = 8.0 Hz). IR (KBr, cm−1)
1718 (C=O), 3421 (NH).
1
7-[(N-Phenylaminylcarboxamido)ethyloxy]coumarin (10m). M.p. 164–165 °C. H-NMR (CDCl3) δ:
3.53 (2H, t, J = 5.5 Hz), 4.07 (2H, t, J = 5.3 Hz), 6.14 (1H, d, J = 9.5 Hz), 6.24 (1H, t, J = 5.6 Hz), 6.78
(1H, d, J = 2.3 Hz), 6.82 (1H, dd, J = 2.8, 8.6 Hz), 6.83 (1H, ddd, J = 1.7, 2.7, 6.9 Hz), 7.13 (2H, dd,
J = 2.3, 8.0 Hz), 7.30 (2H, d, J = 8.0 Hz), 7.39 (1H, d, J = 8.6 Hz), 7.68 (1H, d, J = 8.1 Hz), 8.23
(1H, s). IR (KBr, cm−1) 1660, 1701 (C=O), 3312 (NH).
7-[(N-Benzoyl)-1-methylethyloxy]coumarin (10n). M.p. 135–136 °C. 1H-NMR (CDCl3) δ: 1.45 (3H, d,
J = 6.8 Hz), 4.15 (2H, ddd, J = 4.5, 9.3, 12.4 Hz), 4.65 (1H, dd, J = 3.5, 7.1 Hz), 6.25 (1H, d, J = 9.5 Hz),
6.85 (1H, d, J = 2.2 Hz), 6.89 (1H, dd, J = 7.8, 2.3 Hz), 7.38 (1H, d, J = 8.6 Hz), 7.44 (2H, dd, J = 7.8,
2.1 Hz), 7.50 (1H, d, J = 7.3 Hz), 7.62 (1H, d, J = 9.5 Hz), 7.77 (2H, d, J = 7.5 Hz). IR (KBr, cm−1)
1662, 1708 (C=O), 3330 (NH).
1
7-[(2-Adamantanecarboxamido)ethyloxy]coumarin (10o). Oil. H-NMR (CDCl3) δ: 1.11 (3H, s), 1.72
(6H, dd, J = 12.3, 26.9 Hz), 1.86 (6H, d, J = 2.4 Hz), 2.05 (3H, s), 3.69 (2H, dd, J = 5.5, 10.8 Hz), 4.10
(2H, t, J = 5.1 Hz), 6.03 (1H, s), 6.26 (1H, d, J = 9.5 Hz). 6.82 (1H, d, J = 2.2 Hz), 6.85 (1H, dd,
J = 8.6, 2.4 Hz), 7.38 (1H, d, J = 8.5 Hz), 7.63 (1H, d, J = 9.5 Hz). IR (KBr, cm−1) 1663, 1705 (C=O),
3282 (NH).
1
7-[(N-p-Phenylbenzoyl)-ethyloxy]coumarin (10p). M.p. 216–217 °C. H-NMR (CDCl3) δ: 3.95 (2H,
dd, J = 5.5, 10.8 Hz), 4.24 (2H, t, J = 5.1 Hz), 6.86 (1H, d, J = 2.3 Hz), 6.88 (1H, dd, J = 8.4, 2.3 Hz),

Molecules 2012, 17
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7.39 (2H, d, J = 8.4 Hz), 7.46 (2H, t, J = 7.6 Hz), 7.61 (2H, t, J = 4.5 Hz), 7.63 (1H, d, J = 9.5 Hz),
7.67 (2H, d, J = 8.3 Hz), 7.87 (2H, d, 8.3 Hz). IR (KBr, cm−1) 1656, 1697 (C=O), 3356 (NH).
1
7-[(N-Benzoyl)-1,1-dimethylethyloxy]coumarin (10q). M.p. 104–105 °C. H-NMR (CDCl3) δ: 1.40
(6H, s), 3.71 (2H, d, J = 6.0 Hz), 6.27 (1H, d, J = 9.5 Hz), 6.76 (1H, d, J = 4.2 Hz), 6.88 (1H, d,
J = 2.2 Hz), 6.89 (1H, dd, J = 8.3, 2.2 Hz), 7.36 (1H, d, J = 8.4 Hz), 7.43 ( 2H, t, J = 7.5 Hz), 7.49
(1H, t, J = 7.3 Hz), 7.63 (1H, d, J = 9.5 Hz), 7.81 (2H, d, J = 7.4 Hz). IR (KBr, cm−1) 1651, 1692
(C=O), 3366 (NH).
1
7-[(N-Ethylcarbamyl)ethyloxy]coumarin (10r). M.p. 115–116 °C. H-NMR (CDCl3) δ: 1.25 (3H, t,
J = 6.8 Hz), 3.62 (2H, d, J = 5.1 Hz), 4.09 (1H, t, J = 5.0 Hz), 4.14 (1H, t, J = 6.8 Hz), 5.10 (1H, bs),
6.26 (1H, d, J = 9.6 Hz), 6.80 (1H, d, J = 1.8 Hz), 6.84 (1H, dd, J = 8.6, 2.2 Hz), 7.38 (1H, d, J = 8.6 Hz),
7.63 (1H, d, J = 9.5 Hz). IR (KBr, cm−1) 1677, 1733 (C=O), 3292 (NH).
1
7-[(N-p-Tosyl)-1,1-dimethylethyloxy]coumarin (11k). M.p. 177–178 °C. H-NMR (CDCl3) δ: 1.36
(6H, s), 2.45 (3H, s), 3.12 (2H, d, J = 6.4 Hz), 4.88 (1H, t, J = 5.8 Hz), 6.32 (1H, d, J = 9.5 Hz), 6.80
(2H, d, J = 7.3 Hz), 7.35 (3H, dd, J = 7.4, 5.5 Hz), 7.64 (1H, d, J = 9.5 Hz), 7.76 (2H, d, J = 8.1 Hz).
IR (KBr, cm−1) 1721 (C=O), 3416 (NH)
Bis(3-coumarin) propylenediamide (14). M.p. 264–265 °C. 1H-NMR (CDCl3) δ: 1.98 (2H, dd, J = 6.5,
13.3 Hz), 3.58 (2H, dd, J = 6.4, 12.8 Hz), 7.38 (2H, dd, J = 7.9, 7.6 Hz), 7.67 (2H, ddd, J = 1.1, 7.4,
13
8.4 Hz), 8.92 (1H, bs), 9.01 (1H, s). C-NMR δ 29.61 (CH2CN), 37.40 (2×CCH2N), 116.62 (C-4,4'),
118.55 (C-8,8'), 118.68 (C-5,5'), 125.22 (C-6,6'), 129.77 (C-7,7'), 133.94 (C-9,9'), 148.31 (C-3,3'),
154.46 (C-10,10'), 161.38 (OCN), 161.82 (O=CO). IR (KBr, cm−1) 1658, 1705 (C=O), 3341 (NH).
HR-FAB-MS (EI, 80 eV) m/z, calculated for C23H18N2O6 418.1165, found 418.1163.
1
Bis(3-coumarin)butamethylenediamide (15). M.p. 250–251 °C. H-NMR (CDCl3) δ: 1.75 (2H, t,
J = 2.8 Hz), 3.52 (2H, d, J = 5.8 Hz), 7.39 (2H, dd, J = 8.8, 7.5 Hz), 7.68 (2H, ddd, J = 8.8, 7.7, 1.4 Hz),
8.86 (1H, bs, NH), 8.91 (1H, s, H-4).13C-NMR δ: 27.02 (2×NCCH2), 39.47 (2×NCH2C), 116.61 (C-4,4'),
118.51 (C-8,8'), 118.67 (C-5,5'), 125.25 (C-6,6'), 129.79 (C-7,7'). 133.96 (C-9,9'), 148.31(C-3,3'),
154.41 (C-10,10'), 161.41 (OCN), 161.48 (O=CO). IR (KBr, cm−1) 1658, 1710 (C=O), 3337 (NH).
HR-FAB-MS (EI, 80 eV) m/z, calculated for C24H20N2O6 432.1321, found 432.1471.
1
Bis(3-coumarin)pentamethylenediamide (16). M.p. 221–222 °C. H-NMR (CDCl3) δ: 1.52 (2H, ddd,
J = 6.9, 8.4, 12.1 Hz), 1.70 (4H, dd, J = 7.3, 14.7 Hz), 3.49 (4H, dd, J = 13.1, 6.9 Hz, 2N-CH2), 7.38
(4H, dd, J = 7.7, 8.8 Hz), 7.67 (4H, dd, J = 7.7, 8.4 Hz), 8.82 (2H, bs, NH), 8.90 (2H, s, H-4,4').
13C-NMR δ: 24.38 (NCCCH2), 29.08 (2×NCCH2), 39.67 (2×CH2), 116.61 (C-4,4'), 118.63 (C-8,8'),
118.72 (C-5,5'), 125.22 (C-6,6'), 129.77 (C-7,7'), 133.88 (C-9,9'), 148.19 (C-3,3'), 154.43 (C-10,10'),
161.45 (OCN), 161.47 (OCO). IR (KBr, cm−1) 1654, 1702 (C=O). HR-FAB-MS (EI, 80 eV) m/z,
calculated for C25H22N2O6 446.1478, found 446.1477.
1
Bis(3-coumarin)hexamethylenediamide (17). M.p. 212–213 °C. H-NMR (CDCl3) δ: 1.46 (4H, t-like,
J = 7.1, 12.2 Hz), 1.66 (4H, t-like J = 6.7, 13.5 Hz), 3.47 (4H, dd, J = 6.8, 13.1 Hz), 7.38 (4H, dd,
13
J = 7.6, 8.5 Hz), 7.68 (4H, dd, J = 7.2, 8.5 Hz), 8.81 (2H, bs, NH), 8.91 (2H, s, H-4,4'). C-NMR δ:

Molecules 2012, 17
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26.71 (2×NCCCH2), 29.31 (2×NCCH2), 39.80 (2×NCH2), 116.61 (C-4,4'), 118.65 (C-8,8'), 118.72
(C-5,5'), 125.22 (C-6,6'), 129.76 (C-7,7'), 133.88 (C-9,9'), 148.17 (C-3,3'), 154.42 (C-10,10'), 161.41
(OCN),161.48 (OCO). IR (KBr, cm−1) 1668, 1712 (C=O), 3341 (NH). HR-FAB-MS (EI, 80 eV) m/z,
calculated for C26H24N2O6 460.1634, found 460.1640.
1
Bis(3-coumarin)heptamethylenediamide (18). M.p. 198–199 °C. H-NMR (CDCl3) δ: 1.42 (6H, s,
NCC(CH2)3), 1.64 (4H, t-like, J = 6.2, 12.9 Hz, NC(CH2)2), 3.47 (4H, dd, J = 7.0, 13.1 Hz, N(CH2)2),
7.38 (4H, dd, J = 7.5, 9.2 Hz, H-6,6',8,8'), 7.66 (4H, dd, J = 1.1, 7.7, 9.0 Hz, H-5,5',7,7'), 8.80 (2H, bs,
2×NH), 8.91 (2H, s, H-4,4'). 13C-NMR δ: 26.90 (NCCCCH2), 28.94 (NCCCH2), 29.32 (NCCH2),
39.85 (NCH2), 116.0 (C-4,4'), 118.65 (C-8,8'), 118.72 (C-5,5'), 125.21 (C-6,6'), 129.75 (C-7,7'), 133.87
(C-9,9'), 148.16 (C-3,3'), 154.41 (C-10,10'), 161.37 (CON), 161.47 (COO). IR (KBr, cm−1) 1662, 1704
(C=O), 3368 (NH). MS (rel.int. %) 475.384 (M++H) (40), 191.041 (100), 173.029 (80). HR-FAB-MS
(Ei, 80 eV) m/z, calculated for C27H26N2O6 474.1791, found 474.2761.
1
Bis(3-coumarin)octamethylenediamide (19). M.p. 199–200 °C. H-NMR (CDCl3) δ: 1.31 (8H, t-like,
J = 3.8, 7.1 Hz), 1.63 (4H, dd, J = 7.1, 14.0 Hz), 3.46 (4H, dd, J = 7.0, 13.1 Hz, 2×NCH2), 7.38 (4H,
dt, J = 1.4, 7.5, 8.4 Hz, H-6,6',8,8'), 7.67 (4H, dddd, J = 1.0, 1.2, 8.6,8.9 Hz, H-5,5',7,7'), 8.80 (2H, bs,
13
2×NH), 8.91 (2H, s, H-4,4'). C-NMR δ: 26.94 (NCCCCH2), 29.16 (NCCCH2), 29.36 (NCCH2),
39.90 (NCH2), 116.61 (C-4,4'), 118.67 (C-8,8'), 118.72 (C-5,5'), 125 22 (C-6,6'), 129.76 (C-7,7'),
133.88 (C-9,9'), 148.14 (C-3,3'), 154.42 (C-10,10'), 161.37 (OCN), 161.49 (OCO). IR (KBr, cm−1)
1665, 1710 (C=O), 3342 (NH). HR-FAB-MS (EI, 80 eV) m/z, calculated for C28H28N2O6 488.1947,
found 488.1951.
Bis(3-coumarin)decamethylenediamide (20). M.p. 203–204 °C. 1H-NMR (CDCl3) δ: 1.37 (12H, t-like,
J = 5.9, 8.9 Hz), 1.63 (4H, dt, J = 7.4, 14.3 Hz), 3.46 (4H, dd, J = 6.9, 13.2 Hz, NCH2), 7.38 (4H,
J = 7.5, 8.1 Hz, H-6,6',8,8'), 7.67 (4H, dd, J = 7.7, 8.6 Hz, H-5,5'7,7'), 8.80 (2H, bs, NH), 8.91 (2H, s,
H-4,4'). 13C-NMR δ: 27.01, 29.26, 29.38, 29.43, 39.96 (NCH2), 116.61 (C-4,4'), 118.68 (C-8,8'),
118.73 (C-5,5'), 125.22 (C-6,6'), 129.76 (C-7,7'), 133.88 (C-9,9'), 148.14 (C-3,3'), 154.42 (C-10,10'),
161.39 (OCN), 161.49 (OCO). IR (KBr, cm−1) 1647, 1688 (C=O), 3310 (NH). LCMS 517.305
(M++H), HR-FAB-MS (EI, 80eV) m/z, calculated for C30H32N2O6 512.2260, found 516.2051.
1
Bis(3-coumarin)dodecamethylenediamide (21). M.p. 172–173 °C. H-NMR (CDCl3) δ: 1.36 (16H,
ddd, J = 6.6,7.5,13.5 Hz), 1.63 (4H, dt, J = 7.5, 14.4 Hz), 3.45 (4H, dd, J = 7.0, 13.1 Hz, 2×NCH2),
7.38 (4H, dt, J = 7.5, 8.4 Hz, H-6,6',8,8'), 7.68 (4H, dddd, J = 1.3, 5.7, 7.6, 8.7 Hz, H-5,5',7,7'), 8.79
13
(2H, bs, NH), 8.91 (2H, s, H-4,4'). C-NMR δ: 27.03, 29.30, 29.38, 29.51, 29.54, 39.96 (NCH2),
116.61 (C-4,4'), 118.68 (C-8,8'), 118.73 (C-5,5'), 125.22 (C-6,6'), 129.76 (C-7,7'), 133.88 (C-9,9'),
148.14 (C-3,3'), 154.42 (C-10,10'), 161.39 (OCN), 161.49 (OCO). IR (KBr, cm−1) 1664, 1707 (C=O),
3362 (NH). HR-FAB-MS (EI, 80eV) m/z, calculated for C32H36N2O6 544.2573, found 544.2572.
4. Conclusions
Synthesis of coumarin derivatives via the ring-opening reaction with activated aziridines has not
been reported previously. The reaction of the coumarin anion with N-benzoyl- or N-sulfonylaziridines

Molecules 2012, 17
10860
6 yielded amidoethylated 7- or 4-hydroxycoumarins 7, 8, 9 and 10. The final results depend on the
substitution of the N-acyl or N-sulfonyl groups on the acyl group, so the benzoyl and the coumarin
anions will attack from an abnormal position to provide the major products 7d–f, 10n, and 10q. The
main products resulted from normal ring-opening of the activated aziridines 7h, 8i, 8j, 10k–l, and 11k.
It was assumed that compounds 7, 8, 10, 11, and their analogues were formed by the nucleophilic
attack of acylaziridines via an SN2-like ring opening mechanism. In our previous work, when PyBOP
(13) used as a coupling reagent to synthesize natural amide dimers, relatively high yields were
obtained. In general, for the formation of amide or dimer chains, the reaction temperature had a great
influence on the structural conformation. From NMR spectroscopic analysis, the intermediate,
coumarin-triazobenzene, displayed rearrangement characteristics. The antimicrobial tests performed on
coumarin derivatives 3c, 3c1, 4a2, 4b, 4c, and 7f confirmed the better potential activities of these
compounds against Gram-positive rather than Gram-negative bacteria. Compound 7f was the most
potent of these tested compounds against B. subtilis, with a MIC value of 8 μg/mL, while the coumarin
amide dimers 14–21 displayed lower antibacterial activities (the MICs are >128 to 256).
Acknowledgments
We are grateful to Emil T. Lin, Department of Biopharmaceutical Sciences, School of Pharmacy,
University of California at San Francisco (UCSF) for the LC/MS/MS determination. We also thank
Fan-Ing Lin Hsu for financial support of this research work.
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Sample Availability: Samples of the compounds 14–21 are available from the authors.
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