Substituted 3-benzylcoumarins as allosteric MEK1 inhibitors: Design, synthesis and biological evaluation as antiviral agents

Article abstract of DOI:10.3390/molecules18056057

In order to find novel antiviral agents, a series of allosteric MEK1 inhibitors were designed and synthesized. Based on docking results, multiple optimizations were made on the coumarin scaffold. Some of the derivatives showed excellent MEK1 binding affinity in the appropriate enzymatic assays and displayed obvious inhibitory effects on the ERK pathway in a cellular assay. These compounds also significantly inhibited virus (EV71) replication in HEK293 and RD cells. Several compounds showed potential as agents for the treatment of viral infective diseases, with the most potent compound 18 showing an IC ₅₀ value of 54.57 nM in the MEK1 binding assay.

Full text of DOI:10.3390/molecules18056057

Molecules 2013, 18, 6057-6091; doi:10.3390/molecules18056057
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Substituted 3-Benzylcoumarins as Allosteric MEK1 Inhibitors:
Design, Synthesis and Biological Evaluation as Antiviral Agents
Chao Wang 1, Hao Zhang 2, Fengrong Xu 1, Yan Niu 1,*, Yun Wu 1, Xin Wang 2, Yihong Peng 2,
Jing Sun 1, Lei Liang 1 and Ping Xu 1,*
1
State Key Laboratory of Natural and Biomimetic Drugs, Department of Medicinal Chemistry,
School of Pharmaceutical Science, Peking University Health Science Center,
Beijing 100191, China
2
Department of Microbiology, School of Basic Medical Sciences, Peking University,
Beijing 100191, China
* Authors to whom correspondence should be addressed; E-Mails: yanniu@bjmu.edu.cn (Y.N.);
pingxu@bjmu.edu.cn (P.X.); Tel./Fax: +86-10-8280-1505 (Y.N.); Tel.: +86-10-8280-2632 (P.X.);
Fax: +86-10-8280-1117 (P.X.).
Received: 25 April 2013; in revised form: 10 May 2013 / Accepted: 14 May 2013 /
Published: 21 May 2013
Abstract: In order to find novel antiviral agents, a series of allosteric MEK1 inhibitors
were designed and synthesized. Based on docking results, multiple optimizations were
made on the coumarin scaffold. Some of the derivatives showed excellent MEK1 binding
affinity in the appropriate enzymatic assays and displayed obvious inhibitory effects on the
ERK pathway in a cellular assay. These compounds also significantly inhibited virus
(EV71) replication in HEK293 and RD cells. Several compounds showed potential as
agents for the treatment of viral infective diseases, with the most potent compound 18
showing an IC50 value of 54.57 nM in the MEK1 binding assay.
Keywords: MEK1 inhibitor; coumarin; antiviral
Abbreviations: MAPK, Mitogen-activated protein kinase; MAP3K, Mitogen-activated protein
kinase kinase kinase; MEK, mitogen-activated protein kinase/extracellular signal regulated kinase
kinase; ERK, mitogen-activated protein kinase/extracellular signal-regulated kinase; EV71,
Enterovirus 71; HEK293, human embryonic kidney293; RD cell: rhabdomyosarcoma cell; PDB:
protein data bank; HTRF, homogeneous time-resolved fluorescence; FRET, Förster (Fluorescence)

Molecules 2013, 18
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resonance energy transfer; TPA, 12-O-tetradecanoylphorbol-13-acetate; AP-1, activating protein-1; PE:
petroleum ether; EA: ethyl acetate; Ts: tosyl; t-Bu: tert-butyl.
1. Introduction
According to WHO statistics, almost 75% of infectious diseases are caused by viruses, yet R&D
efforts related to the discovery and development of novel and potent antiviral agents have obviously
lagged behind. A major difficulty in developing antiviral agents is drug resistance caused by virus
variation. To the best of our knowledge, most studies of viruses and viral diseases focused on “viruses”
themselves and ignored the interactions between viruses and their host cells. Several studies have
reported that the RAF/MEK/ERK pathway plays a very important role in virus infection and
replication. Selective blocking of the pathway can prevent the virus proliferation [1–4].
The RAF/MEK/ERK pathway belongs to mitogen-activated protein kinase (MAPK) pathways
which are key intracellular signaling pathways involved in the regulation of a wide range of cellular
events, including cell proliferation, differentiation, survival, apoptosis, etc. Functionally, the
RAF/MEK/ERK pathway of normal cells is in a resting state, and this low activity state is sufficient to
maintain the basic requirements of normal cell metabolism. As viruses need to activate ERK pathway
continually when they replicate in cells [3,5], blocking of the pathway has a strong inhibitory effect on
viral replication. Since the ERK pathway is coded by host genes, antiviral drugs targeting the ERK
pathway can significantly overcome the drug resistance problems caused by virus variation.
MEK1 and MEK2 are closely related, dual-specificity tyrosine/threonine protein kinases that have
an integral role in the ERK signaling pathway by phosphorylating the downstream ERK1 and ERK2.
Since ERK1 and ERK2 are known to be the only substrates for MEK1 and MEK2 [6,7], targeting these
two receptors had been an attractive approach for new therapy development. Lots of MEK1/2
inhibitors have been reported in the last twenty years, and Hasemann et al. have reported the crystal
structure of ternary complex of MEK1 bound to its biarylamine inhibitor PD318088 and MgATP [8].
Most of the efficient MEK1/2 inhibitors are designed as non-ATP-competitive allosteric inhibitors [9–12].
They bind in a unique inhibitor-binding pocket adjacent to the ATP binding site, inducing
conformational changes in the unphosphorylated MEK1/2 enzymes that lock them into a closed but
catalytically inactive species [8]. This unique binding mode offers the non-ATP-competitive allosteric
inhibitors better specificity and selectivity compared to the ATP-competitive inhibitors, which share a
common ATP binding pocket and negatively influenced by the inhibition of other kinases.
Till now, most reported allosteric MEK1/2 inhibitors bear a biarylamine scaffold [6,13] and there
are 13 MEK inhibitors at different stages of clinical evaluations [14] although none of them has been
approved yet for clinical use. On the other hand, very limited types of non-biarylamines have been
identified as MEK1/2 inhibitors, such as PD98059, U0126 and G8935 [15]. PD98059 was the first
synthetic MEK inhibitor which only had activities in vitro [16]. Similarly, U0126, the second MEK
inhibitor with better potency, was mostly used in vitro at research labs due to its serious toxicity issues [10].
The coumarin derivative G8935 was also identified as MEK inhibitor by TR-FRET-based in vitro
assay, however, no more functional evaluations have been reported [15].
For years, we have been focusing on the discovery and development of novel MEK1/2 inhibitors,
the evaluation of their biological activities and the mechanisms of their usage as antivirus agents. Our

Molecules 2013, 18
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early studies showed that in cell-based assays replication of enterovirus EV71, borna virus and herpes
simplex virus HSV2 could be effectively suppressed by the MEK1/2 inhibitor U0126 [17–22].
Selective blocking of mRNA expression of MEK1 could significantly inhibit virus replication, by
contrast, knockdown of MEK2 expression showed dispensable effect, suggesting distinct functions of
MEK1 and MEK2 in virus replication [22,23]. MEK1 might be a potential broad antiviral molecular
target. Herein, we report the discovery of a series of novel 3-benzylcoumarins as allosteric MEK1
inhibitors. Multiple in vitro biological evaluations, including binding affinity to phosphorylated
MEK1, ERK pathway inhibition and antiviral effects were performed, which demonstrated that these
compounds were active MEK1 inhibitors and potential antiviral agent candidates.
2. Results and Discussion
2.1. Molecular Design
According to the report by Gu et al. [23], a series of coumarin derivatives could potently inhibit the
activation of the unphosphorylated human MEK1. Molecular modeling studies suggested that the best
inhibitor, G8935 (Figure 1) with an IC50 of 0.3 μM, bound to the allosteric site in the unphosphorylated
conformation of MEK1. We used G8935 as a lead compound and docked G8935 into the allosteric site
of the MEK1 structure (PDB code: 1S9J) using the docking program GOLD [23] and compared its
binding mode with the host biarylamine allosteric inhibitor PD318088 (Figure 1).
Figure 1. Structures of PD318088 and G8935.
Their docking energy scores were similar to each other and the docked G8935 (docking score:
67.14) overlapped very well with the active conformation of PD318088 (docking score: 66.01) (Figure 2).
Compared with the biarylamine skeleton, the 3-benzyl group is positioned in a lipophilic pocket
formed by Met219, Ile216, Gly210, Arg189, and Asp190 that is not occupied by PD318088 (Figure 3)
and the distance between the fluorine at the para-position of the 3-benzyl group and the terminal
hydrogen of Arg234 is 3.30 Å, therefore structure modification at C3 to improve the affinity could be a
very promising approach. The oxygen of the coumarin ring formed strong hydrogen bonds with Val
211 and Ser212, and the methyl group at C4 extended in the same direction as the side chain on the
aromatic ring of PD318088, so optimization can be performed at the C4 position to enhance protein-
inhibitor interactions. Moreover, the carbonyl group of the carbamoyloxyl moiety substituted at the C7
position also formed a strong hydrogen bond with the backbone of Asp208 in the DFG motif and the
distance between the hydrogen of the methyl group in the C7 substituent and the carbonyl oxygen of
Val127 is only 2.15 Å, so optimization at the C7 position can also be performed to enhance the
interaction between the inhibitor and these two residues.

Molecules 2013, 18
Figure 2. Superposition of the docked conformation of PD318088 (yellow) and the active
6060
conformation of G8935 (pink) (PDB code: 1S9J). Yellow dotted lines: hydrogen bonds
between compounds and MEK1; green dotted lines: illustrative distance between
compounds and MEK1.
Figure 3. Close-up view of the 3-benzyl group fitting into the lipophilic pocket of MEK1
unoccupied by PD318088. Pink: G8935; Yellow: PD318088.
Based on the above observations, 3-benzyl- coumarin may represent a better scaffold for novel
MEK1 inhibitor design compared with the biarylamines. As most reported allosteric MEK1/2
inhibitors bear a biarylamine scaffold and coumarin is one of the very limited types of non-biarylamine
scaffold without further functional evaluations, we selected coumarin as the key moiety and performed
structure optimization at the 3, 4, 7-postions to break though the biarylamine limitation and also
evaluated biological functions of these compounds. This scaffold has following advantages: (1) the
docking results suggested that the coumarin derivative overlapped very well with the biarylamine,
suggesting a high possibility of similar MEK-inhibitory potency; (2) coumarin derivatives can be
easily synthesized; (3) lots of studies could be done for coumarin-based MEK inhibitors since only one
report [23] about coumarin structural modifications has been published and the highest potency could
still be improved. Besides benzyl, a derivative with a benzoyl at the C3 position was also designed for
comparison. Finally, a series of coumarin derivatives with benzyls or benzoyls at C3, various alkyl,

Molecules 2013, 18
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cyano or carboxyl groups at C4 and different types of ester group at the C7 position were designed and
synthesized (Figure 4).
Figure 4. Structure and substituent groups of designed coumarin derivatives.
1
8
5
R1
R4
O
O
7
2
3
6
R2
4
R3
R1 = OH; OCH3; CH3COO; EtCOO; (Me)2NCOO; (Et)2NCOO; n-PrCOO; BuCOO; t-BuCOO; PhCOO; PhSO2COO;
p-CH3PhCOO; R2 = Bn; 4-F-Bn; bezoyl; R3 = H; Me; Et; n-Pr; CH2Cl; CH2OH; CN; COOH; R4 = H; Cl.
2.2. Chemistry
The synthetic routes to the 3-benzyl- and 3-benzoyl coumarin derivatives are outlined in Schemes 1–3.
All substituents are summarized in Table 1.
Scheme 1. Synthesis of substituted 3-benzylcoumarin derivatives 1,2
.
O
O
HO
R4
OH
Et
+ R2X
R3
O
1
8
O
O
a
HO
R4
O
O
R1
R4
O
O
1
7
Et
2
R3
O
c
b
R2
3
6
R2
R2
4
5
R3
R3
O
3
e
2
Bn
Et
+
4
HCOOEt
12-82
O
4a R2=Bn, R3=H, R4=H
1a R3=Me
1b R3=Et
1c R3=n-Pr
2a R2=Bn, R3=Me
2b R2=Bn, R3=Et
2c R2=Bn, R3=n-Pr
2d R2=4-F-Bn, R3=Me
2e R2=4-F-Bn, R3=Et
4b R2=Bn, R3=Me, R4=H
4c R2=Bn, R3=Me, R4=Cl
4d R2=Bn, R3=Et, R4=H
4e R2=Bn, R3=n-Pr, R4=H
4f R2=4-F-Bn, R3=Me, R4=H
4g R2=4-F-Bn, R3=Et, R4=H
2f R2=4-F-Bn, R3=n-Pr
2g R2=Bn, R3=H
4h R2=4-F-Bn, R3=n-Pr, R4=H
4i R2=H, R3=CH2Cl, R4=H
4j R2=H, R3=CH2OH, R4=H
d
1
Reagents and Conditions: (a): NaH, DMF, 60 °C; (b): 70% H2SO4, r.t.; (c): acyl chloride, NaH, r.t.;
(d): H2O, reflux; (e): NaH, THF, 63.3%. 2 For R1, R2, R3 and R4 of target product, see Table 1.
Scheme 2. Synthesis of substituted 3-benzylcoumarin derivatives 83–84 1.
1
Reagents and Conditions: (a): AlCl3, 1 h, r.t., 86.7%; (b): CHCl3, 15 h, 85 °C; (c): toluene, 15 h, 85 °C;
(d): 2 h, 220 °C, nitrogen atmosphere.

Molecules 2013, 18
Scheme 3. Synthesis of substituted 3-benzoyl coumarin derivatives 1.
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1 Reagents and Conditions: (a): piperidine, HCl; (b): NaCN, r.t. 1 h; I2, 1 h; (c): 50% H2SO4, 100 °C, 15 h.
Table 1. Potencies in binding affinity assay.
% binding
(20 µM)
−6.03
% binding
(2 µM)
−0.81
15.84
27.04
29.06
10.90
20.86
33.28
36.28
31.63
75.61
66.26
85.01
70.94
71.56
98.24
66.17
15.49
27.00
6.63
IC50
Std
Compd. R1
R2
R3
R4
Std
Std
(nM)
(nM)
4b
4c
4d
4e
4g
4h
4i
OH
Bn
Me
Me
Et
H
0.27
0.22
0.47
0.16
0.92
0.50
0.36
1.64
0.46
0.47
1.80
5.95
1.65
0.16
3.30
2.38
0.90
2.71
1.63
0.04
0.12
1.38
1.28
0.48
0.69
1.53
0.56
0.62
OH
Bn
Cl 5.10
OH
Bn
H
H
H
H
H
H
H
H
10.39
7.06
OH
Bn
n-Pr
Et
OH
4-F-Bn
4-F-Bn
H
19.62
20.40
22.38
33.58
25.62
95.16
OH
n-Pr
CH2Cl
CH2OH
H
OH
4j
OH
H
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
N(CH3)2COO
N(CH3)2COO
N(CH3)2COO
N(CH3)2COO
N(CH3)2COO
N(CH3)2COO
N(CH3)2COO
N(CH3)2COO
N(Et)2COO
N(Et)2COO
N(Et)2COO
N(Et)2COO
N(Et)2COO
N(Et)2COO
N(Et)2COO
CH3COO
CH3COO
CH3COO
CH3COO
Bn
Bn
Me
Me
Et
3.22 222.8
0.74 307.3
1.92 163.5
5.15 1035
1.29 407.8
5.62 54.57
1.21 157.8
0.66
7.7
6.9
8.2
68
Bn
Cl 80.76
Bn
H
H
H
H
H
H
92.78
95.37
82.14
99.40
87.58
20.02
Bn
n-Pr
Me
Et
4-F-Bn
4-F-Bn
4-F-Bn
Bn
3.6
1.4
10.8
n-Pr
Me
Me
Et
Bn
Cl 48.14
2.55
Bn
H
H
H
H
H
48.09
46.11
27.76
59.16
37.50
1.59 6600
2.78
210
130
Bn
n-Pr
Me
Et
0.43 43.14
0.15 22.26
2.78 25.91
1.25 35.17
0.66 30.55
0.82 72.22
3.01 88.70
0.89 15.47
4-F-Bn
4-F-Bn
4-F-Bn
Bn
1.10
3.73 2190
1.46
n-Pr
Me
Me
Et
Cl 30.83
0.77
Bn
H
H
H
96.53
102.10
25.60
3.08 519.8 11.2
4.35 175.7 11.1
3.45
Bn
Bn
n-Pr

Molecules 2013, 18
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Table 1. Cont.
% binding
R4
% binding
(2 µM)
IC50
Std
Compd. R1
R2
R3
Std
Std
(20 µM)
(nM)
(nM)
10.1
7.9
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
CH3COO
CH3COO
CH3COO
EtCOO
4-F-Bn
4-F-Bn
4-F-Bn
Bn
Me
Et
H
H
H
78.18
100.96
72.16
0.75 72.20
2.00 94.57
3.49 61.41
0.30 70.05
3.73 64.55
3.71 81.04
1.86 19.36
1.95 75.69
3.28 75.42
0.50 72.18
0.34 20.97
1.74 53.76
1.51 45.04
2.22 13.97
4.52 45.34
3.67 76.94
6.06 56.96
0.83 18.83
0.07 8.15
0.27 37.25
0.12 29.52
0.89 42.77
1.30 34.74
1.97 11.72
0.29 14.62
1.82 16.56
0.90 6.61
0.83 43.16
0.12 45.92
0.78 23.71
1.79 31.62
1.73 4.07
0.66 33.33
0.40 10.11
0.59 32.57
1.14 25.78
0.70 44.56
0.58 26.15
0.00 -11.27
0.39 29.87
3.59 247.6
1.06 91.2
3.90 252.1
0.30 325.5
3.93 1033
0.83 391.1
2.40
n-Pr
Me
Me
Et
7.5
Cl 72.37
12.6
79
EtCOO
Bn
H
H
H
H
H
H
85.02
87.02
38.80
90.85
76.31
78.53
EtCOO
Bn
8.8
EtCOO
Bn
n-Pr
Me
Et
EtCOO
4-F-Bn
4-F-Bn
4-F-Bn
Bn
4.53 189.9
3.13 140.4
2.40 175.6
0.97
12.2
10.7
11.3
EtCOO
EtCOO
n-Pr
Me
Me
Et
n-PrCOO
n-PrCOO
n-PrCOO
n-PrCOO
n-PrCOO
n-PrCOO
n-PrCOO
BuCOO
BuCOO
BuCOO
BuCOO
BuCOO
BuCOO
BuCOO
t-BuCOO
t-BuCOO
t-BuCOO
t-BuCOO
t-BuCOO
t-BuCOO
t-BuCOO
PhCOO
PhCOO
PhCOO
PhCOO
PhCOO
PhCOO
PhCOO
PhSO3
Cl 25.79
Bn
H
H
H
H
H
H
H
68.43
54.72
38.86
72.35
96.49
70.28
21.23
3.25 352.9
3.28 473.3
0.77
12.3
13.4
Bn
Bn
n-Pr
Me
Et
4-F-Bn
4-F-Bn
4-F-Bn
Bn
0.29 824.5
2.67 908.6
2.35 944.1
0.37
10.5
28
n-Pr
Me
Me
Et
10.9
Bn
Cl 20.33
0.40
Bn
H
H
H
H
H
H
43.18
42.48
34.02
38.28
23.93
14.78
0.10
Bn
n-Pr
Et
0.97
4-F-Bn
4-F-Bn
4-F-Bn
Bn
0.31
Me
n-Pr
Me
Me
Et
1.63
0.44
0.24
Bn
Cl 34.11
0.57
Bn
H
H
H
H
H
H
21.02
19.05
23.36
20.26
40.92
31.11
0.82
Bn
n-Pr
Et
1.78
4-F-Bn
4-F-Bn
4-F-Bn
Bn
0.65
Me
n-Pr
Me
Me
Et
0.06
0.48
0.06
Bn
Cl 27.96
1.58
Bn
H
H
H
H
H
H
21.54
37.15
30.96
21.28
45.57
2.32
1.54
Bn
n-Pr
Me
Et
0.68
4-F-Bn
4-F-Bn
4-F-Bn
Bn
0.02
1.26
n-Pr
Me
Me
0.45
0.42
PhSO3
Bn
Cl 24.53
0.08

Molecules 2013, 18
6064
Table 1. Cont.
% binding
R4
% binding
(2 µM)
IC50
Std
(nM)
Compd. R1
R2
R3
Std
Std
(20 µM)
(nM)
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
PhSO3
PhSO3
PhSO3
PhSO3
PhSO3
TsO
Bn
Et
H
H
H
H
H
H
−2.35
14.03
7.40
0.11 31.12
0.10 26.00
0.31 16.59
0.95 21.39
0.29 21.55
0.03 2.87
1.22 31.68
0.16 33.20
0.53 24.60
0.07 33.06
0.20 8.05
1.77 37.51
0.05 23.04
0.51 17.56
0.44 23.01
0.42 7.96
1.87 31.91
1.50 32.41
0.24 16.51
1.30
1.13
0.56
0.43
0.38
0.09
1.30
1.65
0.18
0.56
0.10
0.33
0.00
0.68
0.85
0.16
1.87
0.21
0.76
Bn
n-Pr
Et
4-F-Bn
4-F-Bn
4-F-Bn
Bn
Me
n-Pr
Me
Me
Et
17.00
13.78
−2.36
TsO
Bn
Cl 29.57
TsO
Bn
H
H
H
H
H
H
H
H
H
H
H
H
4.76
TsO
Bn
n-Pr
Et
11.73
16.54
9.55
TsO
4-F-Bn
4-F-Bn
4-F-Bn
Bn
TsO
Me
n-Pr
H
TsO
45.87
2.93
CH3O
CH3O
OH
4-F-Bn
PhCO
PhCO
PhCO
PhCO
PhCO
H
15.43
20.52
−8.83
30.03
22.90
6.34
H
CH3O
OH
H
CN
CN
COOH
CH3O
CH3O
The substituted 3-benzylcoumarin derivatives have been synthesized in three steps (Scheme 1)
starting from ethyl acylacetate 1 and benzyl bromide or 4-fluorobenzyl bromide in the presence of
sodium hydride or potassium carbonate in DMF at 60 °C to afford the corresponding substituted ethyl
acylacetates 2. However, 2-formoxyl-ethyl-3-phenyl propionate (2g) can’t be obtained by this method
since the starting material (ethyl formyl acetate) is not commercially available. In this case, 2g was
obtained by an alternative Claisen condensation of ethyl-3-phenyl propionate (3) and ethyl formate.
Next, the condensation of 2 with resorcinol by the Pechmann reaction in the presence of 70% H2SO4
led to the formation of the intermediate 7-hydroxycoumarin cyclization products 4, some of which
(compounds 4b–e, 4g–j) were also evaluated as target compounds. Esterification of 4 with acyl
chlorides in the presence of NaH afforded the target products 12–82 [24].
The Pechmann reaction was not suitable for the synthesis of 3-benzyl-7-N,N-
dimethylcarbamoyloxyl-2H-chromen-2-one (12) which has no substituent group at the C4 position,
and the overall yield of 12 was as low as 3.6%. To improve the synthetic yield of this kind of
compounds, the Wittig reaction [25] was adopted and a better synthetic route was used, which
provided 3-benzyl-7-methoxy-2H-chromen-2-one (83) and 3-(4-fluorobenzyl)-7-methoxy-2H-
chromen-2-one (84) in four steps (Scheme 2). First, selective demethylation of 2,4-dimethoxybenzaldehyde
(5) was performed in the presence of anhydrous AlCl3 to afford 2-hydroxy-4-methoxybenzaldehyde
(6). Ethoxycarbonylmethylene triphenylphosphorane (7) was mixed with benzyl bromide or
4-fluorobenzyl bromide in dry chloroform to form the stable alkylated phosphorane 8. Next 6 was
reacted in toluene with phosphorane 8, which is a resonance stabilized ylide, to yield the corresponding

Molecules 2013, 18
6065
hydroxyesters 9. Only E-isomers of 9 were obtained [25]. These were then converted thermally under
nitrogen atmosphere to the respective coumarins 83 and 84 in high yields.
The substituted 3-benzoylcoumarins have been synthesized as described in Scheme 3. Condensation
of o-hydroxybenzaldehyde (10) and ethyl benzoylacetate (11) in the presence of piperidine afforded
3-benzoyl coumarin rings 85, 86 [26]. Compound 86 could be synthesized without solvent, while
acetonitrile was required as solvent for the synthesis of 85. In addition, it took 24 h to get 85 while the
synthesis of 86 was finished almost instantaneously with the product obtained as solid, and by-products
would be produced if the reaction time was prolonged. Next, cyanation occured in the presence of
NaCN at room temperature for 1 h, followed by addition of iodine into the mixture and reaction for
another hour to give the nitriles 87, 88 [27]. Hydrolysis of the nitriles with 50% H2SO4 gave the
corresponding 4-carboxylic acids 89 [28]. The products were purified by flash chromatography. The
structures were confirmed by 1H and 13C-NMR spectroscopy, EI-MS or EI-HRMS spectra (for details,
see Experimental).
2.3. Binding to Phosphorylated MEK1
All of the newly synthesized compounds were first tested for binding affinity to phosphorylated
MEK1 at 20 μM 2 μM in a biochemical homogeneous time-resolved fluorescence (HTRF) assay. The
IC50 values were determined for the 25 compounds with >45% inhibition of the tracer binding at 20 μM
and the best IC50 value (54.57 nM) was observed for 18 (Table 1).
Only coumarin derivatives with benzyl- or 4-fluorobenzyl substitutions at the C3 position showed
activity (compounds 12–84), while all 3-benzoyl-substituted analogues demonstrated less than 40%
binding affinity at 20 μM (compounds 85–89). This might related to the reduced flexibility of the
carbonyl group, which can block the phenyl ring from entering into the lipophilic pocket, compared
with the CH2 in the benzyl substitution. In addition, 4-fluorobenzyl substitution at the C3 position
seemed to be better than a benzyl group, as observed by comparison of 15, 16, 28–30, 35–37 with their
respective analogues 18, 19, 31–33, 38–40, which suggested that fluorine could enhance the binding
affinity between the inhibitor and protein. Fluorine is different from other halogens. As a small atom of
high electronegativity, fluorine prefers to orient towards the electropositive guanidinium side chain of
Arg234 and undergoes C-F···H-N interactions, and therefore strengthens protein-ligand binding
affinity, while no other halogen could have such an effect [29–31]. Compounds with alkyl chains,
including methyl, ethyl and propyl groups, at the C4 position displayed good affinity and the ethyl
group is the best of them (13, IC50 = 222.8 nM; 15, IC50 = 163.5 nM; 16, IC50 = 1,035 nM) while
compounds without any substitution at this site (e.g., 12) led to the disappearance of affinity. The
affinities of most compounds substituted with chlorine at the C6 position (14, 21, 27, 34, 41, 49, 56,
63, 70, 77) and the non-substituted analogues (13, 20, 28, 35, 42, 48, 55, 62, 69, 76) displayed no
obvious differences. Compounds with a N, N-dimethylcarbamoyloxyl at the C7 position displayed the
best activity, and the sequence of the substituents for better binding affinity was N(CH3)2COO >
MeCOO, EtCOO, n-PrCOO > N(Et)2COO, while other substituents such as t-BuCOO, BuCOO,
PhCOO, TsO, PhSO3, OH, OCH3 showed no activity (comparing the active 18, 25, 32, 39, 46 and the
inactive 52, 59, 67, 73, 80), revealing that the affinity was quite sensitive to modifications at the
7-position. From the structures of these substituent groups at the C7 position, we speculated that their

Molecules 2013, 18
6066
distinct activities may be related to their different steric hindrances and carbon chain lengths. Neither
larger nor smaller substituents at the C7 position were good for activity. The docking results suggested
that the coumarin derivatives with N(CH3)2COO, MeCOO, EtCOO, n-PrCOO or N(Et)2COO at the C7
position (compounds 18, 25, 32, 39 and 46) could occupy the lipophilic pocket suitably. Moreover,
N(CH3)2COO could just occupy the pocket completely. Substituent groups whose steric hindrances
and carbon chain lengths are larger than n-PrCOO, such as t-BuCOO, n-BuCOO, PhCOO, TsO, PhSO3
(compounds 52, 59, 67, 73 and 80), would extend beyond the pocket. That’s the reason why
compounds with different substituents at the C7 position showed different binding affinities.
2.4. Inhibition of ERK Pathway
The effects of the inhibitors on the activation of ERK pathway were determined in TPA (12-O-
tetradecanoylphorbol-13-acetate)-stimulated cells using the AP-1 luciferase reporter gene assay
system. Activating protein-1 (AP-1) is the nuclear transcription factor which is a heterodimeric protein
downstream of MAPK composed of dimers of the Fos and Jun proteins. The stable AP-1 dimers bind
to DNA recognition elements (AP-1 response elements) and mediate transcriptional induction. AP-1
controls a number of cellular events including differentiation, proliferation and apoptosis [32,33].
Simultaneously, the expression of AP-1 can be regulated in response to different extracellular stimuli,
such as cytokines, growth factors, stress, and bacterial and viral infections. ERK pathway is the most
important mediator which is closely related to these responses. Activation of ERK pathway causes
induction of fos gene, and then the product heterodimerizes with the Jun protein to form the AP-1
dimers. These newly formed heterodimers can enhance the expression of c-jun through AP-1 binding
sites in the c-jun promoter. TPA can increase levels of AP-1 proteins through activation of the ERK
pathway. U0126, a specific MEK inhibitor, can suppress the activation of the ERK pathway through
inhibition of MEK1/2. It is reported that U0126 was an inhibitor of AP-1 transactivation [34]. As a
cellular AP-1 antagonist, U0126 did not prevent AP-1 from DNA binding rather it inhibited the up-
regulation of c-Fos and c-Jun and protein levels in activated cells. These effects resulted from
inhibition of the ERK pathway. The AP-1 luciferase reporter assay system was constructed according
to the effect of U0126 on AP-1 levels in TPA-activated cells as described above. This system was used
to screen synthesized compounds which may have the same effect as U0126.
Twenty compounds which had excellent binding affinity with phosphorylated MEK1 were selected
for further testing in intracellular assays. U0126 was taken as a positive control. In HEK 293 cells
treated with TPA, 30 μM U0126 could suppress the up-regulation of AP-1 by 50%, as detected by the
reporter gene assay. The AP-1 IC50s for inhibition of ERK pathway activation are shown in Table 2.
Fifteen of 20 compounds exhibited inhibition effects on activation of the ERK pathway. Among them,
six compounds (13, 17, 18, 19, 31, 33) acted more efficiently than U0126 at the same concentration.
All of them were 3-(4-fluorobenzyl)- or 3-benzylcoumarins with methyl, ethyl or propyl substitutions
at the C4 position and N,N-dimethylcarbamoyloxyl or acetoxyl substitution at the C7 position.
Compounds with other substituent groups at these positions showed less inhibition in this assay.

Molecules 2013, 18
Table 2. Inhibition of ERK pathway in AP-1 luciferase reporter assay.
6067
IC50 (μM)
27.50 ± 1.16
5.40 ± 1.26
30.80 ± 1.40
N/A
4.06 ± 3.26
23.37 ± 1.11
4.31 ± 2.14
N/A
IC50 (μM)
N/A
11.63 ± 1.20
N/A
49.82 ± 1.24
38.1 ± 1.26
N/A
87.45 ± 1.98
88.68 ± 2.52
85.86 ± 1.46
64.61 ± 1.74
U0126
13
14
15
17
18
19
20
28
32
33
34
36
38
39
40
42
43
67
37.56 ± 1.10
90.49 ± 1.83
15.70 ± 1.18
29
31
2.5. Inhibition of Virus Replication
To further examine the functional effects, we selected EV71 to perform the antiviral analysis. It is
established that inhibition of the ERK pathway with U0126 can suppress EV71 replication in HEK 293
and RD cells [10], so the antiviral activity of six compounds (13, 17, 18, 19, 31, 33) was determined by
measuring the inhibition of virus-induced cytopathic effects in cells. EC50s of inhibition of EV71
replication for the six compounds are summarized in Table 3. CC50 is the median cytotoxic
concentration measured with the MTT assay. Therapeutic index (TI) was calculated as a comparison of
a compound that caused the therapeutic effect (EC50) to the amount that caused cytotoxicity (CC50),
whereby the higher the value of TI, the safer the compound was. The results in Table 3 showed four
compounds but not 17 and 31 had inhibition effects on EV71 replication in both HEK293 and RD
cells, but according to the values of TI, compounds 13 and 19 not only had a better anti-viral activity,
but could also be used more safely. Examining the structures of compounds, all of them had benzyl or
substituted benzyl at the C3 position, an alkyl group at the C4 position and N,N-dimethyl-
carbamoyloxyl or acetoxyl substitution at the C7 position, suggesting that these substituent groups
were beneficial to the antiviral effects.
Table 3. Antiviral effects in HEK293 cells and RD cells.
HEK293 cells
RD cells
EC50 (μM) CC50 (μM) TI (CC50/IC50)
EC50 (μM) CC50 (μM) TI (CC50/IC50)
13
17
18
19
31
33
3.29
N/A
19.38
4.85
N/A
12.77
98.22
42.38
65.31
316.43
119.3
27.88
29.85
N/A
3.37
65.24
N/A
2.5
5.25
10
3.98
N/A
18.5
152
85.91
72.92
756.06
N/A
60.8
16.36
7.29
190
N/A
2.24
2.18
41.46
For compounds 13, 19 and 33, we did further experiments by western blots which were processed
as previously described [22] to verify their inhibition to ERK pathway and EV71 replication in RD
cells (Figure 5).

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6068
Figure 5. Verification of the inhibition to ERK pathway and EV71 replication in RD cells
by western blots.
The results showed that the expression of pERK and virus capsid protein VP1 can be inhibited
significantly and dramatically by compounds at 20 μM. These results intuitively verified the
compound inhibition of the ERK pathway and EV71 replication in RD cells.
3. Experimental
3.1. General Conditions
All solvents and reagents were used as obtained. Melting points were taken with an XT4A
1
13
apparatus and are uncorrected. H-NMR and C-NMR spectra were recorded at ambient temperature
using a 400 MHz Bruker Avance III spectrometer or 300 MHz JEOL JNM-AL300 spectrometer.
Chemical shifts are expressed in ppm relative to tetramethylsilane. MS data were obtained with Bruker
Apex IV FTMS or MDS SCIEX QSTAR systems. TLC analysises were performed on silica gel GF254
purchased from Qingdao Haiyang Chemical Co. (Qingdao, China) or Merck (Darmstadt, Germany).
3.2. Chemistry
3.2.1. General Procedure for the Preparation of Ethyl 2-Benzylacylacetate or Ethyl 2-(p-Fluorobenzyl)
Acylacetates 2a–f
NaH (1.2 equiv.) was added to a solution of ethyl acylacetate (1, 1.0 equiv.) in THF (3 mL/mmol
ethyl acylacetate) at 0 °C under a nitrogen atmosphere. The reaction mixture was stirred for 15 minutes
and benzyl bromide or 4-fluorobenzyl bromide (1.1 equiv.) was added dropwise. The reaction mixture
was then heated to 60 °C for 12 h. The reaction mixture was poured into ice-cold saturated NH4Cl and
extracted with EtOAc three times. The combined organic extract was washed with brine, dried over
MgSO4 and the solvent was removed under reduced pressure. The products were purified by flash
column chromatography.
Ethyl 2-benzyl-3-oxobutanoate (2a). Yield: 7.17 g, 65.1%, yellow oil. 1H-NMR (300 MHz, CDCl3): δ
1.18 (t, J = 7.1 Hz, 3H, CH3), 2.17 (s, 3H, CH3), 3.15 (d, J = 7.5 Hz, 2H, PhCH2), 3.78 (t, J = 7.5 Hz,
1H, CH), 4.13 (q, J = 7.2 Hz, 2H, CH2CH3), 7.16–7.28 (m, 5H, PhH).
1
Ethyl 2-benzyl-3-oxopentanoate (2b). Yield: 0.799 g, 68.11%, colorless oil. H-NMR (CDCl3): δ 1.00
(t, J = 7.2 Hz, 3H, COCH2CH3), 1.19 (t, J = 7.2 Hz, 3H, OCH2CH3), 1.49–1.59 (m, 1H, CH2Ph), 2.53–2.60

Molecules 2013, 18
6069
(m, 1H, CH2Ph), 3.16 (q, J = 7.6 Hz, 2H, COCH2CH3), 3.76–3.81 (dt, J = 2.4, 5.2 Hz, 1H, CHCH2Ph),
4.13 (q, J = 7.2 Hz, 2H, OCH2CH3), 7.15–7.28 (m, 5H, PhH). MS (ESI): m/z 235.1 (M+H+), 257.1
(M+Na+), 273.1 (M+K+).
Ethyl 2-benzyl-3-oxohexanoate (2c). Yield: 0.949 g, 76.4%, colorless oil. 1H-NMR (CDCl3): δ 0.84 (t,
J = 7.2 Hz, 3H, CH2CH2CH3), 1.19 (t, J = 7.2 Hz, 3H, OCH2CH3), 1.54 (sext, J = 7.2 Hz, 2H,
CH2CH2CH3), 2.27–2.35 (dt, J = 7.2 Hz, 1H, CH2Ph), 2.47–2.55 (dt, J = 7.2 Hz, 1H, CH2Ph), 3.15 (t,
J = 7.2 Hz, 2H, CH2C2H5), 3.78 (t, J = 7.6 Hz, 1H, CHCH2Ph), 4.13 (q, J = 7.2 Hz, 2H, OCH2CH3),
7.16–7.28 (m, 5H, PhH). MS (ESI): m/z 249.1 (M+H+), 271.1 (M+Na+), 287.1 (M+K+).
1
Ethyl 2-(4-fluorobenzyl)-3-oxobutanoate (2d). Yield: 1.41 g, 59%, yellow oil. H-NMR (CDCl3): δ
1.21 (t, J = 7.2 Hz, 3H, CH2CH3), 2.19 (s, 3H, CH3CO), 3.13 (dd, J =1.2, 7.2 Hz, 2H, CH2Ph), 3.73 (t,
J = 7.6 Hz, 1H, CH), 4.14 (ddd, J = 1.2, 7.2, 11.6 Hz, 2H, CH2CH3), 6.93–6.98 (m, 2H, PhH), 7.12–7.16
(m, 2H, PhH).
Ethyl 2-(4-fluorobenzyl)-3-oxopentanoate (2e). Yield: 0.52 g, 21%, colorless oil. 1H-NMR (CDCl3): δ
1.00 (t, J = 7.2 Hz, 3H, CH2CH3), 1.20 (t, J = 7.2 Hz, 3H, OCH2CH3), 2.31–2.39 (dt, J = 7.2 Hz, 1H,
CH2Ph), 2.53–2.61 (dt, J = 7.2 Hz, 1H, CH2Ph), 3.12 (q, J = 4.8 Hz, 2H, CH2CH3), 3.74 (t, J = 7.6 Hz,
1H, CHCH2Ph), 4.14 (dd, J = 7.2 Hz, 2H, OCH2CH3), 6.93–6.97 (m, 2H, PhH), 7.11–7.15 (m, 2H,
PhH). MS (ESI): m/z 253.1 (M+H+), 275.1 (M+Na+), 291.1 (M+K+).
Ethyl 2-(4-fluorobenzyl)-3-oxohexanoate (2f). Yield: 2.086 g, 78.3%, colorless oil. 1H-NMR (CDCl3):
δ 0.85 (t, J = 7.2 Hz, 3H, CH2CH2CH3), 1.21 (t, J = 7.2 Hz, 3H, OCH2CH3), 1.55 (sext, J = 7.2 Hz, 2H,
CH2CH2CH3), 2.28–2.36 (dt, J = 7.2 Hz, 1H, CH2Ph), 2.48–2.56 (dt, J = 7.2 Hz, 1H, CH2Ph), 3.07–3.17
(m, 2H, CH2C2H5), 3.73 (t, J = 7.6 Hz, 1H, CHCH2Ph), 4.11–4.17 (dd, J = 7.2 Hz, 2H, OCH2CH3),
6.93–6.97 (m, 2H, PhH), 7.11–7.15 (m, 2H, PhH). MS (ESI): m/z 267.1 (M+H+), 289.1 (M+Na+),
305.1 (M+K+).
3.2.2. General Procedure for the Preparation of 7-Hydroxy-2H-chromen-2-one derivatives 4b–i
The compounds 2 obtained above (1.0 equiv.) and resorcinol (1.0 equiv.) were suspended in 70%
sulfuric acid (2 mL/mmol resorcinol) at room temperature. The reaction mixture was stirred for 12 h
and poured into ice water and extracted with EtOAc three times. The combined organic extract was
washed with brine, dried over MgSO4 and the solvent was removed under reduced pressure. The crude
products were recrystalized from ethanol to afford the products.
3-Benzyl-7-hydroxy-4-methyl-2H-chromen-2-one (4b). Yield: 0.84 g, 63.2%, yellow solid, m.p.:
1
228–230 °C. H-NMR (DMSO-d6): δ 2.40 (s, 3H, CH3), 3.93 (s, 2H, CH2), 6.72 (d, J = 2.4 Hz, 1H,
PhH), 6.82 (dd, J = 2.4, 8.8 Hz, 1H, PhH), 7.16–7.30 (m, 5H, PhH), 7.64 (d, J = 8.8 Hz, 1H, PhH).
3-Benzyl-6-chloro-7-hydroxy-4-methyl-2H-chromen-2-one (4c). Yield: 0.652 g, 43.5%, white powder,
1
m.p.: 261–263 °C. H-NMR (DMSO-d6): δ 2.40 (s, 3H, CH3), 3.93 (s, 2H, CH2), 6.89 (s, 1H, PhH),
7.15–7.28 (m, 5H, PhH), 7.79 (s, 1H, PhH), 11.26 (s, 1H, OH).

Molecules 2013, 18
6070
3-Benzyl-4-ethyl-7-hydroxy-2H-chromen-2-one (4d). Yield: 0.251 g, 56.3%, yellow solid, m.p.:
140–141 °C. 1H-NMR (DMSO-d6): δ 1.02 (t, J = 7.6 Hz, 3H, CH3), 2.82 (q, J = 7.6 Hz, 2H, CH2CH3),
3.91 (s, 2H, CH2Ph), 6.72 (d, J = 2.8 Hz, 1H, H-8), 6.80–6.83 (dd, J = 2.4, 8.8 Hz, 1H, H-6), 7.17–7.29
(m, 5H, PhH), 7.64 (d, J = 8.8 Hz, 1H, H-5), 10.45 (s, 1H, OH). MS (ESI): m/z 281.1 (M+H+), 303.1
(M+Na+), 319.1 (M+K+).
3-Benzyl-7-hydroxy-4-propyl-2H-chromen-2-one (4e). Yield: 0.185 g, 46%, white solid, m.p.: 139–140 °C.
1H-NMR (DMSO-d6): δ 0.95 (t, J = 7.2 Hz, 3H, CH3), 1.35–1.42 (m, J = 7.6 Hz, 2H, CH2CH2CH3),
2.77 (t, J = 8.0 Hz, 2H, CH2C2H5), 3.91 (s, 2H, CH2Ph), 6.71 (d, J = 2.4 Hz, 1H, H-8), 6.80–6.83 (dd,
J = 2.0, 8.8 Hz, 1H, H-6), 7.15–7.28 (m, 5H, PhH), 7.63 (d, J = 8.8 Hz, 1H, H-5), 10.44 (s, 1H, OH).
13C-NMR (DMSO-d6): δ 14.57, 22.82, 30.77, 32.33, 102.60, 111.89, 113.54, 120.11, 126.48, 127.13,
128.35, 128.83, 140.22, 152.80, 154.37, 160.84, 162.10. HRMS (ESI): m/z 295.13330 (M+H+),
317.11525 (M+Na+), 333.08918 (M+K+).
3-(4-Fluorobenzyl)-7-hydroxy-4-methyl-2H-chromen-2-one (4f). Yield: 0.762 g, 78%, white powder,
1
m.p.: 243–244 °C. H-NMR (DMSO-d6): δ 2.40 (s, 3H, CH3), 3.90 (s, 2H, CH2), 6.71 (s, 1H, PhH),
6.81 (d, J = 8.4 Hz, 1H, PhH), 7.01–7.10 (m, 2H, PhH), 7.23–7.27 (m, 2H, PhH), 7.63–7.66 (d, J = 8.8 Hz,
1H, PhH), 10.46 (s, 1H, OH). 13C-NMR (CDCl3): δ 15.06, 31.26, 101.89, 112.38, 112.92, 114.92,
115.13, 120.01, 126.77, 129.72, 129.80, 135.53, 148.58, 153.43, 160.46, 161.29, 161.86.
4-Ethyl-3-(4-fluorobenzyl)-7-hydroxy-2H-chromen-2-one (4g). Yield: 0.183 g, yield 31%. M.p.:
1
131–132 °C. Light yellow solid. H-NMR (DMSO-d6): δ 1.03 (t, J = 7.6 Hz, 3H, CH3), 2.83
(q, J = 7.6 Hz, 2H, CH2CH3), 3.90 (s, 2H, CH2Ph), 6.73 (s, 1H, H-8), 6.82 (d, J = 8.8 Hz, 1H, H-6), 7.09
(t, J = 8.8 Hz, 2H, PhH), 7.25 (t, 2H, PhH), 7.65 (d, J = 8.8 Hz, 1H, H-5), 10.47 (s, 1H, OH). 13C-NMR
(DMSO-d6): δ 13.47, 21.52, 30.87, 102.18, 111.01, 113.11, 114.91, 115.12, 119.12, 126.55, 129.62,
129.70, 135.76, 153.85, 153.99, 159.45, 160.41, 161.61. HRMS (ESI): m/z 299.10780 (M+H+),
321.09033 (M+Na+), 337.06455 (M+K+).
3-(4-Fluorobenzyl)-7-hydroxy-4-propyl-2H-chromen-2-one (4h). Yield: 0.631 g, 67.4%, white solid,
m.p.: 130–131 °C. 1H-NMR (CDCl3): δ 1.04 (t, J = 7.2 Hz, 3H, CH2CH2CH3), 1.52 (sext, J = 7.2 Hz, 2H,
CH2CH2CH3), 2.75–2.90 (t, J = 8.0 Hz, 2H, CH2C2H5), 3.97 (s, 2H, CH2Ph), 6.80–6.83 (dd, J = 2.4,
8.8 Hz, 1H, H-6), 6.92–7.00 (m, 3H, PhH, H-8), 7.19–7.23 (m, 2H, PhH), 7.48 (d, J = 8.8 Hz, 1H, H-5).
MS (ESI): m/z 313.1 (M+H+), 335.1 (M+Na+), 351.1 (M+K+).
4-(Chloromethyl)-7-hydroxy-2H-chromen-2-one (4i). Yield: 1.518 g, 72%, grey solid, m.p.: 166–167 °C.
1H-NMR (DMSO-d6): δ 4.96 (s, 2H, CH2), 6.42 (s, 1H, H-3), 6.76 (s, 1H, H-8), 6.85 (d, J = 8.8 Hz, 1H,
H-6), 7.68 (d, J = 8.8 Hz, 1H, H-5), 10.66 (s, 1H, OH). 13C-NMR (DMSO-d6): δ 41.33, 102.49,
109.32, 111.03, 113.05, 126.52, 150.95, 155.27, 160.11, 161.43. HRMS (ESI): m/z 211.01561
(M+H+), 232.99758 (M+Na+).
3.2.3. Procedure for the Preparation of 7-Hydroxy-4-(hydroxymethyl)-2H-chromen-2-one (4j)
Compound 4i (1 mmol, 0.21 g) was suspended in water (20 mL) and refluxed for four days. After
extraction with EtOAc three times the organic extracts were combined, washed with brine and dried

Molecules 2013, 18
6071
over MgSO4. The products were purified by flash column chromatography to afford a yellow solid.
Yield: 78 mg, yield 41%, m.p.: 148–149 °C. 1H-NMR (DMSO-d6): δ 4.71 (s, 2H, CH2), 5.59 (br s, 1H,
ArOH), 6.24 (s, 1H, H-3), 6.73 (s, 1H, H-8), 6.78 (d, J = 8.4 Hz, 1H, H-6), 7.53 (d, J = 8.4 Hz, 1H, H-5),
10.52 (s, 1H, CH2OH). 13C-NMR (DMSO-d6): δ 59.04, 102.26, 106.51, 109.53, 112.79, 125.45,
154.83, 156.77, 160.60, 160.95. HRMS (ESI): m/z 193.04956 (M+H+), 215.03145 (M+Na+), 231.00538
(M+K+).
3.2.4. Procedure for the Preparation of 3-benzyl-7-N,N-Dimethylcarbamate-2H-chromen-2-one (12)
To the solution of ethyl-3-phenylpropionate (3, 0.98 g, 5.5 mmol,1 equiv.,) in DMF (4 mL), was
added NaH (0.25 g, 8.25 mmol, 1.5 equiv.) at 0 °C under a nitrogen atmosphere. The reaction mixture
was stirred for 1 h and ethyl formate (0.68 mL, 8.25 mmol, 1.5 equiv.) was added. The reaction
mixture was stirred for another hour at 0 °C and then 24 h at r.t. Then the pH was adjusted to 2–3 with
3 M HCl, followed by routine workup. Purification of the residue by flash column chromatography
(PE–EA = 30:1) afforded 2-formoxylethyl-3-phenylpropionate (2g) as a yellow oil (0.718 g, 63.3%).
Compound 2g (0.206 g, 1 mmol, 1 equiv.) and resorcinol (0.110 g, 1 mmol, 1 equiv.) were
suspended in 70% sulfuric acid (4 mL), and heated at 100 °C for 1 h. The mixture was processed by
routine procedures. Purification of the residue by flash column chromatography (PE–EA = 5:1)
afforded 3-benzyl-7-hydroxylcoumarin (4a) as a thick white solid (0.074 g, 29.2%).
To the solution of compound 4a (0.25 g, 1 mmol, 1 equiv.) in DMF (12 mL) was added NaH (0.045 g,
1.5 mmol, 1.5 equiv.) at room temperature under a nitrogen atmosphere. The reaction mixture was
stirred for 1 h and dimethycarbamoyl chloride (0.14 mL, 1.5 mmol, 1.5 equiv.) was added. The
reaction mixture was stirred for another 4 h. The mixture was processed by routine procedures, then
the crude product was recrystallised from ethanol as a white solid (0.063 g, 19.5%), m.p.: 151–153 °C.
1H-NMR (CDCl3): δ 3.02 (s, 3H, NCH3), 3.11 (s, 3H, NCH3), 3.88 (s, 2H, CH2), 7.01–7.04 (dd, J = 2,
8.4 Hz, 1H, PhH), 7.10 (d, J = 6 Hz, 1H, PhH), 7.24–7.37 (m, 7H, PhH). HRMS (ESI): m/z 324.12341
(M+H+), 346.10524 (M+Na+).
3.2.5. General Procedure for the Preparation of 7-Carboxylate-2H-chromen-2-one derivatives 13–82 [24]
To the solution of the 7-hydroxycoumarin derivatives 4 obtained above (1.0 equiv.) in DMF
(5.5 mL/mmol) was added NaH (2.0 equiv.) at room temperature under a nitrogen atmosphere. The
reaction mixture was stirred for 30 minutes and acylchloride (2.0 equiv.) was added. The reaction
mixture was stirred for another hour and poured into saturated NaHCO3. After extraction with EtOAc
three times the organic extract was combined washed with brine and dried over MgSO4. The products
were purified by flash column chromatography.
3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl dimethylcarbamate (13). Yield: 0.44 g, 86.8%, white solid,
1
m.p.: 130–133 °C. H-NMR (CDCl3): δ 2.43 (s, 3H, CH3), 3.03 (s, 3H, NCH3), 3.12 (s, 3H, NCH3),
4.06 (s, 2H, CH2), 7.08–7.29 (m, 5H, PhH), 7.58 (d, J = 8.8 Hz, 1H, PhH). 13C-NMR (CDCl3): δ 15.48,
32.95, 36.56, 36.82, 110.10, 117.88, 118.22, 124.38, 125.15, 126.34, 128.26, 128.57, 138.82, 147.13,
152.91, 153.41, 153.99, 161.79. HRMS (ESI): m/z 338.13939 (M+H+).

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3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl dimethylcarbamate (14). Yield: 0.193 g, 52%,
1
white solid, m.p.: 156–157 °C. H-NMR (CDCl3): δ 2.42 (s, 3H, CH3), 3.05 (s, 3H, NCH3), 3.17 (s,
3H, NCH3), 4.06 (s, 2H, CH2), 7.19–7.29 (m, 6H, PhH), 7.64 (s, 1H, PhH). 13C-NMR (CDCl3): δ
15.53, 33.04, 36.64, 36.98, 112.58, 119.13, 123.18, 125.36, 125.64, 126.47, 128.24, 128.64, 138.44,
146.02, 149.19, 151.16, 152.99, 161.22. HRMS (ESI): m/z 372.10060 (M+H+).
3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl dimethylcarbamate (15). Yield: 0.147 g, 94.6%, white solid,
m.p.: 85–86 °C. 1H-NMR (CDCl3): δ 1.14 (t, J = 7.6 Hz, 3H, CH3), 2.86 (q, J = 7.6 Hz, 2H, CH2CH3),
3.03 (s, 3H, NCH3), 3.12 (s, 3H, NCH3), 4.04 (s, 2H, CH2Ph), 7.08 (d, J = 2.4 Hz, 1H, H-8), 7.11–7.13
(dd, J = 2.4, 7.6 Hz, 1H, H-6), 7.17–7.27 (m, 5H, ArH), 7.60 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR
(CDCl3): δ 13.20, 22.27, 32.54, 36.56, 36.82, 110.38, 116.66, 118.28, 123.42, 125.12, 126.33, 128.19,
128.56, 139.04, 152.68, 153.30, 153.48, 154.00, 162.11. HRMS (ESI): m/z 352.15437(M+H+),
374.13662 (M+Na+).
3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl dimethylcarbamate (16). Yield: 0.44 g, 86.8%, white solid,
1
m.p.: 117–118 °C. H-NMR (DMSO-d6): δ 0.97 (t, J = 7.2 Hz, 3H, CH2CH2CH3), 1.38–1.45
(m, J = 7.6 Hz, 2H, CH2CH2CH3), 2.84 (t, J = 8.0 Hz, 2H, CH2C2H5), 2.93 (s, 3H, NCH3), 3.06 (s, 3H,
NCH3), 3.97 (s, 2H, CH2Ph), 7.15–7.27 (m, 7H, ArH), 7.83 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR
(CDCl3): δ 14.46, 22.46, 31.15, 32.73, 36.56, 36.82, 110.33, 116.99, 118.21, 123.80, 125.22, 126.34,
128.18, 128.55, 139.08, 151.33, 153.27, 153.39, 153.99, 162.06. HRMS (ESI): m/z 366.17006 (M+H+),
388.15222 (M+Na+).
3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl dimethylcarbamate (17). Yield: 0.173 g, 65.3%,
white powder, m.p.: 149–150 °C. 1H-NMR (CDCl3): δ 2.44 (s, 3H, CH3), 3.03 (s, 3H, NCH3), 3.12 (s,
3H, NCH3), 4.02 (s, 2H, CH2), 6.93–6.97 (m, 2H, PhH), 7.09–7.11 (m, 2H, PhH), 7.20–7.23 (m, 2H,
PhH), 7.59 (d, J = 8.6 Hz, 1H, PhH). 13C-NMR (CDCl3): δ 15.44, 32.20, 36.56, 36.82, 110.15, 115.24,
115.45, 117.78, 118.30, 124.25, 125.19, 129.65, 129.73, 134.42, 134.45, 147.11, 152.91, 153.50,
153.96, 160.32, 161.71, 162.74. HRMS (ESI): m/z 356.12960 (M+H+).
4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl dimethylcarbamate (18). Yield: 0.090 g, yield
68%. M.p.: 75 °C. White solid. 1H-NMR (CDCl3): δ 1.14 (t, J = 7.6 Hz, 3H, CH3), 2.85 (q, J = 7.6 Hz,
2H, CH2CH3), 3.02 (s, 3H, NCH3), 3.12 (s, 3H, NCH3), 3.99 (s, 2H, CH2Ph), 6.94 (t, J = 8.0 Hz, 2H,
PhH), 7.09–7.14 (m, 2H, H-6, H-8), 7.20–7.23 (m, J = 6.4 Hz, 2H, PhH), 7.60 (d, J = 8.8 Hz, 1H, H-5).
13C-NMR (CDCl3): δ 13.28, 22.25, 31.77, 36.54, 36.79, 110.37, 115.17, 115.39, 116.51, 118.38,
123.16, 125.23, 129.60, 129.68, 134.72, 152.83, 153.40, 153.96, 160.27, 162.04, 162.70. HRMS (ESI):
m/z 370.14511 (M+H+), 392.12716 (M+Na+).
3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl dimethylcarbamate (19). Yield: 0.175 g, 91.6%,
1
white solid, m.p.: 82–84 °C. H-NMR (CDCl3): δ 1.03 (t, J = 7.6 Hz, 3H, CH2CH2CH3), 1.52 (sext,
J = 7.6 Hz, 2H, CH2CH2CH3), 2.80 (t, J = 7.6 Hz, 2H, CH2C2H5), 3.03 (s, 3H, NCH3), 3.12 (s, 3H,
NCH3), 3.99 (s, 2H, CH2Ph), 6.92–6.97 (m, 2H, ArH), 7.08–7.13 (m, 2H, ArH), 7.19–7.23 (m, 2H,
13
ArH), 7.58 (d, J = 8.8 Hz, 1H, H-5). C-NMR (CDCl3): δ 14.45, 22.52, 31.12, 31.97, 36.55, 36.81,

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110.35, 115.19, 115.40, 116.86, 118.32, 123.58, 125.31, 129.57, 129.65, 134.72, 151.43, 153.36,
153.96, 160.30, 161.99, 162.73. HRMS (ESI): m/z 384.16069 (M+H+), 406.14275 (M+Na+).
3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl diethylcarbamate (20). Yield: 0.05 g, 27%, white solid,
m.p.: 109 °C. 1H-NMR (CDCl3): δ 1.20–1.29 (dt, J = 6.8 Hz, 6H, CH2CH3), 2.44 (s, 3H, CH3), 3.39–3.46
(m, J = 6.8 Hz, 4H, CH2CH3), 4.06 (s, 2H, CH2Ph), 7.09–7.12 (m, 2H, ArH), 7.19–7.26 (m, 5H, ArH),
7.59 (d, J = 8.4 Hz, 1H, ArH). 13C-NMR (CDCl3): δ 13.33, 14.26, 15.50, 32.96, 42.01, 42.40, 110.05,
117.78, 118.22, 124.30, 125.12, 126.34, 128.27, 128.58, 138.84, 147.16, 152.93, 153.33, 153.48,
161.82. HRMS (ESI): m/z 366.16971 (M+H+), 388.15157 (M+Na+), 404.12558 (M+K+).
3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl diethylcarbamate (21). Yield: 0.069 g, 58%,
white solid, m.p.: 83–84 °C. 1H-NMR (CDCl3): δ 1.21–1.32 (dt, J = 6.4 Hz, 6H, CH2CH3), 2.41 (s, 3H,
CH3), 3.39–3.51 (m, J = 6.8 Hz, 4H, CH2CH3), 4.05 (s, 2H, CH2Ph), 7.18–7.27 (m, 6H, ArH), 7.64 (s,
1H, H-5). 13C-NMR (CDCl3): δ 13.27, 14.15, 15.53, 33.05, 42.21, 42.59, 112.54, 119.01, 123.30,
125.38, 125.55, 126.47, 128.25, 128.64, 138.48, 146.07, 149.28, 151.16, 152.34, 161.25. HRMS (ESI):
m/z 400.13113 (M+H+), 422.11302 (M+Na+), 438.08702 (M+K+).
3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl diethylcarbamate (22). Yield: 0.118 g, 62.4%, milk white
1
solid, m.p.: 64–65 °C. H-NMR (CDCl3): δ 1.15 (t, J = 7.6 Hz, 3H, CH3), 1.21–1.29 (dt, J = 6.8 Hz,
6H, N(CH2CH3)2), 2.87 (q, J = 7.6 Hz, 2H, CH2CH3), 3.38–3.49 (m, J = 6.8 Hz, 4H, N(CH2CH3)2),
4.05 (s, 2H, CH2Ph), 7.11–7.13 (m, 2H, H-6 and H-8), 7.20–7.30 (m, 5H, CH2Ph), 7.61 (d, J = 8.4 Hz,
1H, H-5). 13C-NMR (CDCl3): δ 13.26, 13.35, 14.30, 22.30, 32.54, 42.06, 43.43, 110.33, 116.54,
118.34, 123.28, 125.17, 126.34, 128.20, 128.57, 139.08, 152.81, 153.37, 153.45, 162.17. HRMS (ESI):
m/z 380.18545 (M+H+), 402.16736 (M+Na+), 418.14141 (M+K+).
3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl diethylcarbamate (23). Yield: 0.099 g, 50%, white solid,
1
m.p.: 112–113 °C. H-NMR (CDCl3): δ 1.02 (3H, CH2CH2CH3), 1.21–1.23 (6H, CH2CH3), 1.50 (2H,
CH2CH2CH3), 2.79 (2H, CH2CH2CH3), 3.41 (4H, CH2CH3), 4.03 (s, 2H, CH2Ph), 7.08–7.24 (m, 7H,
13
ArH), 7.56 (d, J = 7.2 Hz, 1H, ArH). C-NMR (CDCl3): δ 18.30, 19.25, 19.42, 27.45, 36.11, 37.73,
47.04, 47.42, 115.22, 121.85, 123.17, 128.71, 130.20, 131.31, 133.18, 133.52, 144.13, 156.34, 158.30,
158.39, 167.03. HRMS (ESI): m/z 394.20179 (M+H+), 416.18395 (M+Na+), 432.15778 (M+K+).
3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl diethylcarbamate (24). Yield: 0.02 g, 10%, white
solid, m.p.: 101–102 °C. 1H-NMR (CDCl3): δ 1.22–1.27 (m, 6H, CH2CH3), 2.44 (s, 3H, CH3), 3.39–3.45
(m, 4H, CH2CH3), 4.02 (s, 2H, CH2Ph), 6.95 (t, J = 8.0 Hz, 2H, ArH), 7.10–7.12 (m, 2H, H-6 and
13
H-8), 7.22 (m, 2H, ArH), 7.60 (d, J = 8.0 Hz, 1H, H-5). C-NMR (CDCl3): δ 13.33, 14.27, 15.48,
32.20, 42.03, 42.42, 110.09, 115.24, 115.45, 117.67, 118.32, 124.15, 125.18, 129.66, 129.74, 134.48,
147.18, 152.91, 153.30, 153.57, 160.30, 161.75, 162.73. HRMS (ESI): m/z 384.16108 (M+H+),
406.14280 (M+Na+), 422.11691 (M+K+).
4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl diethylcarbamate (25). Yield: 0.125 g, 63%, white
1
solid, m.p.: 74–75 °C. H-NMR (CDCl3): δ 1.15 (t, J = 7.6 Hz, 3H, CH3), 1.20–1.29 (dt, J = 6.8 Hz,
6H, N(CH2CH3)2), 2.86 (q, J = 7.6 Hz, 2H, CH2CH3), 3.38–3.48 (m, J = 6.8 Hz, 4H, N(CH2CH3)2),

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4.00 (s, 2H, CH2Ph), 6.96 (t, J = 8.4 Hz, 2H, ArH), 7.10 (d, 1H, H-6), 7.13 (s, 1H, H-8), 7.22 (m, 2H,
13
ArH), 7.60 (d, J = 8.4 Hz, 1H, H-5). C-NMR (CDCl3): δ 18.27, 19.24, 27.24, 36.79, 47.03, 47.42,
115.34, 120.20, 120.41, 121.42, 123.34, 128.16, 130.12, 134.58, 134.66, 139.67, 139.70, 157.73,
158.30, 158.47, 165.30, 167.03, 167.73. HRMS (ESI): m/z 398.17617 (M+H+), 420.15785 (M+Na+),
436.13206 (M+K+).
3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl diethylcarbamate (26). Yield: 0.134 g, 65%,
white solid, mp: 51–52 °C. 1H-NMR (CDCl3): δ 1.04 (t, J = 7.2 Hz, 3H, CH2CH2CH3), 1.20–1.29 (m,
6H, CH2CH3), 1.52–1.53 (m, 2H, CH2CH2CH3), 2.80 (br s, 2H, CH2CH2CH3), 3.40–3.46 (m, 4H,
CH2CH3), 4.00 (s, 2H, CH2Ph), 6.95 (t, J = 8.4 Hz, 2H, ArH), 7.10–7.14 (m, 2H, H-6 and H-8), 7.20–7.23
(m, 2H, ArH), 7.58 (d, J = 8.4 Hz, 1H, H-5).13C-NMR (CDCl3): δ 13.35, 14.29, 14.50, 22.57, 31.15,
32.00, 42.09, 42.45, 110.31, 115.22, 115.44, 116.79, 118.35, 123.54, 125.32, 129.64, 134.79, 151.49,
153.35, 160.34, 162.04, 162.75. HRMS (ESI): m/z 412.19179 (M+H+), 434.17324 (M+Na+).
3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl acetate (27). Yield: 0.05 g, 29%, white solid,
m.p.: 190 °C. 1H-NMR (CDCl3): δ 2.39 (s, 3H, CH3CO), 2.43 (s, 3H, CH3), 4.06 (s, 2H, CH2Ph), 7.15
(s, 1H, H-8), 7.20–7.27 (m, 5H, CH2Ph), 7.68 (s, 1H, H-5). 13C-NMR (CDCl3): δ 15.56, 20.60, 33.07,
112.32, 119.73, 122.97, 125.69, 126.08, 126.53, 128.24, 128.67, 138.31, 145.88, 148.40, 151.16,
161.01, 167.94. HRMS (ESI): m/z 343.07294 (M+H+), 365.05485 (M+Na+).
3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl acetate (28). Yield: 0.082 g, 55%, white solid, m.p.:
165–166 °C. 1H-NMR (CDCl3): δ 2.33 (s, 3H, CH3CO), 2.44 (s, 3H, CH3), 4.06 (s, 2H, CH2Ph), 7.05
(dd, J = 8.8, 2.0 Hz, 1H, H-6), 7.10 (d, J = 2.0 Hz, 1H, H-8), 7.18–7.29 (m, 5H, CH2Ph), 7.62 (d,
J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 15.51, 21.11, 32.97, 110.16, 118.00, 118.47, 124.85,
125.43, 126.40, 128.25, 128.60, 138.69, 146.98, 152.34, 152.90, 161.61, 168.82. HRMS (ESI): m/z
309.11175 (M+H+), 331.09374 (M+Na+), 347.06770 (M+K+).
3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl acetate (29). Yield: 0.11 g, 66%, white solid, m.p.: 123–125 °C.
1H-NMR (CDCl3): δ 1.14 (t, J = 7.6 Hz, 3H, CH2CH3), 2.34 (s, 3H, CH3CO), 2.86 (q, J = 7.6 Hz, 2H,
CH2CH3), 4.04 (s, 2H, CH2Ph), 7.06 (d, J = 8.8 Hz, 1H, H-6), 7.12 (s, 1H, H-8), 7.19–7.29 (m, 5H,
CH2Ph), 7.62 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 13.20, 21.12, 22.28, 32.56, 110.43,
117.26, 118.05, 123.90, 125.39, 126.40, 128.19, 128.59, 138.91, 152.24, 152.52, 153.46, 161.91,
168.84. HRMS (ESI): m/z 323.12751 (M+H+), 345.10923 (M+Na+), 361.08309 (M+K+).
3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl acetate (30). Yield: 0.105 g, 63%, white solid, m.p.:
139–140 °C. 1H-NMR (CDCl3): δ 1.04 (t, J = 7.2 Hz, 3H, CH2CH2CH3), 1.49–1.55 (m, J = 7.6 Hz, 2H,
CH2CH2CH3), 2.34 (s, 3H, CH3CO), 2.81 (t, J = 7.2 Hz, 2H, CH2CH2CH3), 4.04 (s, 2H, CH2Ph), 7.05
(d, J = 8.4 Hz, 1H, H-6), 7.11 (s, 1H, H-8), 7.19–7.29 (m, 5H, CH2Ph), 7.60 (d, J = 8.8 Hz, 1H, H-5).
13C-NMR (CDCl3): δ 14.48, 21.12, 22.46, 31.15, 32.75, 110.38, 117.58, 117.99, 124.28, 125.48,
126.40, 128.17, 128.58, 138.95, 151.17, 152.21, 153.38, 161.86, 168.83. HRMS (ESI): m/z 337.14307
(M+H+), 359.12512 (M+Na+), 375.09918 (M+K+).

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3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl acetate (31). Yield: 0.100 g, 61%, white solid,
m.p.: 119–120 °C. 1H-NMR (CDCl3): δ 2.34 (s, 3H, CH3CO), 2.44 (s, 3H, CH3), 4.02 (s, 2H, CH2Ph),
6.95 (t, J = 8.4 Hz, 2H, ArH), 7.06–7.11 (m, 2H, H-6 and H-8), 7.12 (s, 1H, H-8), 7.21–7.26 (m, 2H,
ArH), 7.62 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 15.47, 21.11, 32.21, 110.19, 115.26, 115.47,
118.09, 118.36, 124.69, 125.49, 129.66, 129.74, 134.31, 134.34, 146.97, 152.43, 152.88, 160.32,
161.52, 162.75, 168.80. HRMS (ESI): m/z 327.10315 (M+H+), 349.08500 (M+Na+), 365.05920 (M+K+).
4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl acetate (32). Yield: 0.12 g, 70%, white solid, m.p.:
1
122–123 °C. H-NMR (CDCl3): δ 1.16 (t, J = 7.6 Hz, 3H, CH2CH3), 2.34 (s, 3H, CH3CO), 2.86 (q,
J = 7.6 Hz, 2H, CH2CH3), 4.00 (s, 2H, CH2Ph), 6.95 (t, J = 8.4 Hz, 2H, ArH), 7.07 (d, J = 8.8 Hz, 1H,
H-6), 7.12 (s, 1H, H-8), 7.20–7.26 (m, 2H, ArH), 7.63 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ
13.27, 21.11, 22.26, 31.82, 110.47, 115.25, 115.46, 117.15, 118.14, 123.72, 125.43, 129.59, 129.67,
134.52, 134.55, 152.33, 152.56, 153.45, 160.33, 161.83, 162.76, 168.83. HRMS (ESI): m/z 341.11816
(M+H+), 363.10008 (M+Na+).
3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl acetate (33). Yield: 0.127 g, 72%, white solid,
m.p.: 150–151 °C. 1H-NMR (CDCl3): δ 1.07 (t, J = 7.6 Hz, 3H, CH2CH2CH3), 1.52–1.58 (m, J = 7.6 Hz,
2H, CH2CH2CH3), 2.36 (s, 3H, CH3CO), 2.80–2.85 (m, 2H, CH2CH2CH3), 4.02 (s, 2H, CH2Ph), 6.98
(t, J = 8.4 Hz, 2H, ArH), 7.07–7.10 (dd, J = 2.0, 8.4 Hz, 1H, H-6), 7.13 (d, J = 2.0 Hz, 1H, H-8), 7.21–7.25
13
(m, 2H, ArH), 7.63 (d, J = 8.8 Hz, 1H, H-5). C-NMR (CDCl3): δ 14.49, 21.12, 22.52, 31.14, 32.01,
110.43, 115.25, 115.46, 117.47, 118.08, 124.11, 125.54, 129.57, 129.65, 134.58, 151.20, 152.30,
153.37, 160.34, 161.78, 162.77, 168.82. HRMS (ESI): m/z 355.13436 (M+H+), 377.11631 (M+Na+),
393.09050 (M+K+).
3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl propionate (34). Yield: 0.047 g, 44%, white solid,
m.p.: 124–126 °C. 1H-NMR (CDCl3): δ 1.32 (t, J = 7.2 Hz, 3H, CH2CH3), 2.43 (s, 3H, CH3), 2.69 (q,
J = 7.2 Hz, 2H, CH2CH3), 4.06 (s, 2H, CH2Ph), 7.15 (s, 1H, H-8), 7.19–7.28 (m, 5H, CH2Ph), 7.67 (s,
1H, H-5). 13C-NMR (CDCl3): δ 8.99, 15.56, 27.45, 33.07, 112.33, 119.63, 123.00, 125.66, 126.01,
126.52, 128.25, 128.67, 138.34, 145.92, 148.51, 151.18, 161.05, 171.48. HRMS (ESI): m/z 357.08905
(M+H+), 379.07086 (M+Na+), 395.04497 (M+K+).
3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl propionate (35). Yield: 0.14 g, 87%, white solid, m.p.:
118–119 °C. 1H-NMR (CDCl3): δ 1.28 (t, J = 7.6 Hz, 3H, CH2CH3), 2.45 (s, 3H, CH3), 2.63 (q, J = 7.6 Hz,
2H, CH2CH3), 4.07 (s, 2H, CH2Ph), 7.06 (d, J = 8.4 Hz, 1H, H-6), 7.10 (s, 1H, H-8), 7.19–7.29 (m, 5H,
CH2Ph), 7.61 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 8.93, 15.50, 27.74, 32.97, 110.12, 118.00,
118.38, 124.78, 125.38, 126.39, 128.26, 128.60, 138.71, 147.00, 152.50, 152.92, 161.64, 172.35.
HRMS (ESI): m/z 323.12765 (M+H+), 345.10937 (M+Na+), 361.08330 (M+K+).
3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl propionate (36). Yield: 0.143 g, 85%, white solid, m.p.: 124 °C.
1H-NMR (CDCl3): δ 1.15 (t, J = 7.6 Hz, 3H, CH2CH3), 1.28 (t, J = 7.6 Hz, 3H, COCH2CH3), 2.63 (q,
J = 7.6 Hz, 2H, CH2CH3), 2.87 (q, J = 7.6 Hz, 2H, COCH2CH3), 4.05 (s, 2H, CH2Ph), 7.06 (d, J = 8.8 Hz,
1H, H-6), 7.12 (s, 1H, H-8), 7.19–7.29 (m, 5H, CH2Ph), 7.62 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR
(CDCl3): δ 8.94, 13.21, 22.28, 27.74, 32.56, 110.39, 117.16, 118.06, 123.82, 125.34, 126.39, 128.20,

Molecules 2013, 18
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128.58, 138.93, 152.40, 152.54, 153.48, 161.95, 172.37. HRMS (ESI): m/z 337.14303 (M+H+),
359.12504 (M+Na+).
3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl propionate (37). Yield: 0.121 g, 69%, white solid, m.p.:
1
120–121 °C. H-NMR (CDCl3): δ 1.04 (t, J = 7.2 Hz, 3H, CH2CH2CH3), 1.28 (t, J = 7.6 Hz, 3H,
COCH2CH3), 1.49–1.57 (m, J = 7.6 Hz, 2H, CH2CH2CH3), 2.63 (q, J = 7.6 Hz, 2H, COCH2CH3), 2.81
(t, J = 8.0 Hz, 2H, CH2CH2CH3), 4.04 (s, 2H, CH2Ph), 7.05 (d, J = 8.8 Hz, 1H, H-6), 7.11 (s, 1H, H-8),
13
7.19–7.29 (m, 5H, CH2Ph), 7.59 (d, J = 8.4 Hz, 1H, H-5). C-NMR (CDCl3): δ 8.94, 14.48, 22.47,
27.74, 31.16, 32.75, 110.34, 117.48, 117.99, 124.19, 125.44, 126.40, 128.18, 128.57, 138.97, 151.20,
152.37, 153.39, 161.90, 172.35. HRMS (ESI): m/z 351.15891 (M+H+), 373.14083 (M+Na+),
389.11452 (M+K+).
3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl propionate (38). Yield: 0.082 g, 48%, white
1
solid, m.p.: 115–116 °C. H-NMR (CDCl3): δ 1.28 (t, J = 7.6 Hz, 3H, CH2CH3), 2.45 (s, 3H, CH3),
2.63 (q, J = 7.6 Hz, 2H, CH2CH3), 4.02 (s, 2H, CH2Ph), 6.95 (t, J = 8.0 Hz, 2H, ArH), 7.06–7.10 (m, 2H,
H-6 and H-8), 7.20–7.26 (m, 2H, ArH), 7.62 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 8.93,
15.47, 27.73, 32.22, 110.16, 115.26, 115.48, 118.09, 118.27, 124.63, 125.43, 129.67, 129.75, 134.33,
134.36, 146.98, 152.59, 152.91, 160.33, 161.56, 162.76, 172.33. HRMS (ESI): m/z 341.11829
(M+H+), 363.10044 (M+Na+), 379.07431 (M+K+).
4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl propionate (39). Yield: 0.14 g, 81%, white solid,
1
m.p.: 97–98 °C. H-NMR (CDCl3): δ 1.16 (t, J = 7.6 Hz, 3H, CH2CH3), 1.28 (t, J = 7.6 Hz, 3H,
COCH2CH3), 2.63 (q, J = 7.6 Hz, 2H, CH2CH3), 2.87 (q, J = 7.6 Hz, 2H, COCH2CH3), 4.00 (s, 2H,
CH2Ph), 6.95 (t, J = 8.4 Hz, 2H, ArH), 7.07 (d, J = 8.8 Hz, 1H, H-6), 7.12 (s, 1H, H-8), 7.20–7.24 (m,
2H, ArH), 7.62 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 8.93, 13.27, 22.26, 27.74, 31.82,
110.43, 115.25, 115.46, 117.04, 118.14, 123.65, 125.38, 129.60, 129.68, 134.54, 134.57, 152.49, 152.57,
153.47, 160.33, 161.87, 162.76, 172.35. HRMS (ESI): m/z 355.13383 (M+H+), 377.11579 (M+Na+).
3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl propionate (40). Yield: 0.113 g, 61%, white
solid, m.p.: 94–95 °C. 1H-NMR (CDCl3): δ 1.05 (t, J = 7.2 Hz, 3H, CH2CH2CH3), 1.28 (t, J = 7.6 Hz,
3H, COCH2CH3), 1.50–1.56 (m, J = 7.6 Hz, 2H, CH2CH2CH3), 2.63 (q, J = 7.6 Hz, 2H, COCH2CH3),
2.81 (t, J = 7.6 Hz, 2H, CH2CH2CH3), 4.00 (s, 2H, CH2Ph), 6.95 (t, J = 8.4 Hz, 2H, ArH), 7.06 (d,
J = 8.8 Hz, 1H, H-6), 7.11 (s, 1H, H-8), 7.19–7.23 (m, 2H, ArH), 7.60 (d, J = 8.8 Hz, 1H, H-5).
13C-NMR (CDCl3): δ 8.93, 14.49, 22.53, 27.74, 31.14, 32.01, 110.39, 115.24, 115.45, 117.37, 118.09,
124.03, 125.49, 129.58, 129.66, 134.58, 134.61, 151.23, 152.46, 153.38, 160.34, 161.82, 162.77,
172.35. HRMS (ESI): m/z 369.15020 (M+H+), 391.13211 (M+Na+), 407.10587 (M+K+).
3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl butyrate (41). Yield: 0.076 g, 68.5%, white solid,
1
m.p.: 107–108 °C. H-NMR (CDCl3): δ 1.07 (t, J = 7.2 Hz, 3H, CH2CH2CH3), 1.83 (m, 2H,
CH2CH2CH3), 2.42 (s, 2H, CH3), 2.63 (t, J = 7.2 Hz, 2H, CH2CH2CH3), 4.05 (s, 2H, CH2Ph), 7.13 (s,
1H, H-8), 7.18–7.28 (m, 5H, ArH), 7.66 (s, 1H, H-5). 13C-NMR (CDCl3): δ13.65, 15.55, 18.34, 33.07,
35.84, 112.34, 119.62, 123.00, 125.67, 125.99, 126.52, 128.25, 128.66, 138.35, 145.93, 148.50, 151.16,
161.03, 170.64. HRMS (ESI): m/z 371.10463 (M+H+), 393.08669 (M+Na+), 409.06073 (M+K+).

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3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl butyrate (42). Yield: 0.15 g, 89%, white solid, m.p.:
1
139–140 °C. H-NMR (CDCl3): δ 1.05 (t, J = 7.6 Hz, 3H, CH2CH3), 1.80 (q, J = 7.6 Hz, 2H,
CH2CH3), 2.44 (s, 3H, CH3), 2.57 (t, J = 7.6 Hz, 2H, CH2CH2CH3), 4.06 (s, 2H, CH2Ph), 7.05 (d,
J = 8.8 Hz, 1H, H-6), 7.09 (s, 1H, H-8), 7.19–7.26 (m, 5H, CH2Ph), 7.61 (d, J = 8.8 Hz, 1H, H-5).
13C-NMR (CDCl3): δ 13.61, 15.51, 18.34, 32.97, 36.17, 110.14, 118.04, 118.37, 124.77, 125.39,
126.39, 128.26, 128.60, 138.72, 147.00, 152.48, 152.91, 161.63, 171.52. HRMS (ESI): m/z 337.14308
(M+H+), 359.12508 (M+Na+).
3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl butyrateen-7-yl propionate (43). Yield: 0.18 g, 100%, white
solid, m.p.: 102 °C. 1H-NMR (CDCl3): δ 1.06 (t, J = 7.2 Hz, 3H, COCH2CH2CH3), 1.14 (t, J = 7.6 Hz,
3H, CH2CH3), 1.78–1.83 (m, J = 7.2 Hz, 2H, COCH2CH2CH3), 2.58 (t, J = 7.2 Hz, 2H, COCH2CH2CH3),
2.87 (q, J = 7.6 Hz, 2H, CH2CH3), 4.04 (s, 2H, CH2Ph), 7.05 (d, J = 8.8 Hz, 1H, H-6), 7.11 (s, 1H, H-8),
13
7.19–7.29 (m, 5H, CH2Ph), 7.62 (d, J = 8.8 Hz, 1H, H-5). C-NMR (CDCl3): δ 13.20, 13.61, 22.28,
29.71, 32.57, 36.17, 110.42, 117.15, 118.08, 123.82, 125.34, 126.38, 128.19, 128.58, 138.94, 152.38,
152.53, 153.48, 161.93, 171.55. HRMS (ESI): m/z 351.15891 (M+H+), 373.14081 (M+Na+),
389.11448 (M+K+).
3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl butyrate (44). Yield: 0.167 g, 92%, white solid, m.p.:
1
105–106 °C. H-NMR (CDCl3): δ 1.02–1.07 (m, J = 7.6 Hz, 6H, CH3), 1.49–1.55 (m, J = 7.6 Hz,
2H, CH2CH2CH3), 1.77–1.83 (m, J = 7.6 Hz, 2H, COCH2CH2CH3), 2.58 (t, J = 7.2 Hz, 2H,
COCH2CH2CH3), 2.81 (t, J =8.0 Hz, 2H, CH2CH2CH3), 4.04 (s, 2H, CH2Ph), 7.04 (d, J = 8.8 Hz, 1H,
H-6), 7.10 (s, 1H, H-8), 7.19–7.29 (m, 5H, CH2Ph), 7.59 (d, J = 8.4 Hz, 1H, H-5). 13C-NMR (CDCl3):
δ 13.60, 14.48, 18.35, 22.47, 31.15, 32.76, 36.17, 110.37, 117.48, 118.03, 124.19, 125.45, 126.40,
128.18, 128.57, 138.98, 151.20, 152.36, 153.39, 161.89, 171.54. HRMS (ESI): m/z 365.17454
(M+H+), 387.15649 (M+Na+), 403.13042 (M+K+).
3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl butyrate (45). Yield: 0.122 g, 69%, white solid,
m.p.: 85–86 °C. 1H-NMR (CDCl3): δ 1.05 (t, J = 7.2 Hz, 3H, CH2CH2CH3), 1.77–1.83 (m, J = 7.2 Hz,
2H, CH2CH2CH3), 2.45 (s, 3H, CH3), 2.58 (t, J = 7.2Hz, 2H, CH2CH2CH3), 4.02 (s, 2H, CH2Ph), 6.95
(t, J = 8.0 Hz, 2H, ArH), 7.05–7.10 (m, 2H, H-6 and H-8), 7.20–7.26 (m, 2H, ArH), 7.62 (d, J = 8.8 Hz,
1H, H-5). 13C-NMR (CDCl3): δ 13.61, 15.47, 18.34, 32.22, 36.16, 110.18, 115.26, 115.47, 118.13,
118.27, 124.63, 125.43, 129.67, 129.75, 134.33, 134.36, 146.99, 152.57, 152.90, 160.32, 161.54,
162.75, 171.51. HRMS (ESI): m/z 355.13422 (M+H+), 377.11617 (M+Na+), 393.09024 (M+K+).
4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl butyrate (46). Yield: 0.155 g, 84%, white solid,
1
m.p.: 79 °C. H-NMR (CDCl3): δ 1.06 (t, J = 7.6 Hz, 3H, CH2CH2CH3), 1.16 (t, J = 7.6 Hz, 3H,
CH2CH3), 1.78–1.83 (m, J = 7.6 Hz, 2H, CH2CH2CH3), 2.58 (t, J = 7.6 Hz, 2H, CH2CH2CH3), 2.87 (q,
J = 7.6 Hz, 2H, CH2CH3), 4.00 (s, 2H, CH2Ph), 6.95 (t, J = 8.4 Hz, 2H, ArH), 7.06 (d, J = 8.4 Hz, 1H,
H-6), 7.11 (s, 1H, H-8), 7.20–7.24 (m, 2H, ArH), 7.62 (d, J = 8.4 Hz, 1H, H-5). 13C-NMR (CDCl3): δ
13.27, 13.60, 18.34, 22.26, 31.82, 36.17, 110.46, 115.25, 115.46, 117.04, 118.17, 123.66, 125.37,
129.59, 129.67, 134.53, 134.57, 152.47, 152.56, 153.47, 160.34, 161.85, 162.77, 171.54. HRMS (ESI):
m/z 369.14937 (M+H+), 391.13124 (M+Na+).

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3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl butyrate (47). Yield: 0.122 g, 64%, white solid,
1
m.p.: 88–90 °C. H-NMR (CDCl3): δ 1.05–1.07 (m, 6H, CH3), 1.50–1.56 (m, J = 7.6 Hz, 2H,
CH2CH2CH3), 1.77–1.83 (m, J = 7.2 Hz, 2H, COCH2CH2CH3), 2.58 (t, J = 7.2 Hz, 2H, COCH2CH2CH3),
2.80 (t, J = 7.6 Hz, 2H, CH2CH2CH3), 4.00 (s, 2H, CH2Ph), 6.95 (t, J = 8.4 Hz, 2H, ArH), 7.05 (d,
J = 8.8 Hz, 1H, H-6), 7.10 (s, 1H, H-8), 7.21–7.22 (m, 2H, ArH), 7.60 (d, J = 8.8 Hz, 1H, H-5).
13C-NMR (CDCl3): δ 13.60, 14.49, 18.35, 22.53, 31.14, 32.01, 36.17, 110.42, 115.24, 115.45, 117.37,
118.12, 124.03, 125.48, 129.58, 129.65, 134.58, 151.22, 152.44, 153.38, 160.34, 161.81, 162.77,
171.53. HRMS (ESI): m/z 383.16575 (M+H+), 405.14765 (M+Na+), 421.12162 (M+K+).
3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl pentanoate (48). Yield: 0.151 g, 86%, white solid, m.p.:
1
110–111 °C. H-NMR (CDCl3): δ 0.98 (t, J = 7.6 Hz, 3H, CH2CH3), 1.43–1.48 (m, J = 7.6 Hz, 2H,
CH2CH3), 1.73–1.77 (m, J = 7.6 Hz, 2H, CH2CH2CH3), 2.44 (s, 3H, CH3), 2.59 (t, J = 7.6 Hz, 2H,
COCH2), 4.06 (s, 2H, CH2Ph), 7.05 (d, J = 8.8 Hz, 1H, H-6), 7.09 (s, 1H, H-8), 7.18–7.25 (m, 5H,
CH2Ph), 7.61 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 13.71, 15.50, 22.23, 26.86, 32.97, 34.07,
110.13, 118.03, 118.37, 124.76, 125.39, 126.38, 128.27, 128.60, 138.73, 147.00, 152.50, 152.91,
161.62, 171.70. HRMS (ESI): m/z 351.15892 (M+H+), 373.14081 (M+Na+), 389.11455 (M+K+).
3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl pentanoate (49). Yield: 0.099 g, 86%, white solid,
1
m.p.: 108–109 °C. H-NMR (CDCl3): δ 0.98 (t, J = 7.2 Hz, 3H, CH2CH3), 1.45–1.50 (m, J = 7.2 Hz,
2H, CH2CH2CH2CH3), 1.74–1.80 (m, J = 7.2 Hz, 2H, CH2CH2CH2CH3), 2.42 (s, 3H, CH3), 2.65 (t,
J = 7.2 Hz, 2H, CH2CH2CH2CH3), 4.05 (s, 2H, CH2Ph), 7.13 (s, 1H, H-8), 7.19–7.29 (m, 5H,
13
CH2PhH), 7.66 (s, 1H, H-5). C-NMR (CDCl3): δ 13.70, 15.55, 22.23, 26.82, 33.07, 33.72, 112.34,
119.62, 123.00, 125.67, 125.99, 126.52, 128.25, 128.66, 138.35, 145.93, 148.51, 151.16, 161.03,
170.81. HRMS (ESI): m/z 385.12011 (M+H+), 407.10215 (M+Na+), 423.07623 (M+K+).
3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl pentanoate (50). Yield: 0.112 g, 62%, white solid, m.p.:
1
72–73 °C. H-NMR (CDCl3): δ 0.98 (t, J = 7.2 Hz, 3H, CH2CH2CH2CH3), 1.14 (t, J = 6.8 Hz, 3H,
CH2CH3), 1.43–1.48 (m, J = 6.8 Hz, 2H, CH2CH2CH2CH3), 1.74–1.77 (m, J = 6.8 Hz, 2H,
CH2CH2CH2CH3), 2.59 (t, J = 6.8 Hz, 2H, COCH2), 2.86–2.87 (m, J = 6.0 Hz, 2H, CH2CH3), 4.04 (s,
2H, CH2Ph), 7.04–7.10 (m, 2H, H-6 and H-8), 7.18–7.25 (m, 5H, CH2PhH), 7.61 (d, J = 6.0 Hz, 1H,
13
H-5). C-NMR (CDCl3): δ 18.17, 18.70, 27.21, 27.26, 31.85, 37.56, 39.06, 115.40, 122.14, 123.06,
128.81, 130.32, 131.37, 133.18, 133.57, 143.93, 157.39, 157.51, 158.47, 166.92, 176.71. HRMS (ESI):
m/z 365.17447 (M+H+), 387.15629 (M+Na+), 403.13036 (M+K+).
3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl pentanoate (51). Yield: 0.166 g, 88%, white solid, m.p.:
1
78–79 °C. H-NMR (CDCl3): δ 0.95–1.05 (m, 6H, CH3), 1.43–1.53 (m, 4H, CH2CH2CH2CH3 and
CH2CH2CH3), 1.74–1.79 (m, 2H, CH2CH2CH2CH3), 2.57–2.61 (m, 2H, CH2CH2CH3), 2.78–2.82 (m,
2H, COCH2), 4.04 (s, 2H, CH2Ph), 7.03–7.09 (m, 2H, H-6 and H-8), 7.18–7.25 (m, 5H, CH2PhH),
13
7.57–7.59 (m, 1H, H-5). C-NMR (CDCl3): δ 13.71, 14.48, 22.22, 22.47, 26.86, 31.15, 32.75, 34.07,
110.36, 117.47, 118.03, 124.19, 125.44, 126.40, 128.18, 128.57, 138.98, 151.20, 152.37, 153.39,
161.89, 171.73. HRMS (ESI): m/z 379.19074 (M+H+), 401.17263 (M+Na+), 417.14655 (M+K+).

Molecules 2013, 18
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4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl pentanoate (52). Yield: 0.153 g, 80%, white solid,
1
m.p.: 70–71 °C. H-NMR (CDCl3): δ 0.98 (t, J = 7.6 Hz, 3H, CH2CH2CH2CH3), 1.16 (t, J = 7.6 Hz,
3H, CH2CH3), 1.43–1.49 (m, J = 7.6 Hz, 2H, CH2CH2CH2CH3), 1.72–1.80 (m, J = 7.6 Hz, 2H,
CH2CH2CH2CH3), 2.60 (t, J = 7.6 Hz, 2H, COCH2), 2.87 (q, J = 7.6 Hz, 2H, CH2CH3), 4.00 (s, 2H,
CH2Ph), 6.95 (t, J = 8.4 Hz, 2H, ArH), 7.06 (d, J = 8.8 Hz, 1H, H-6), 7.11 (s, 1H, H-8), 7.20–7.23 (m,
2H, ArH), 7.62 (d, J = 8.4 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 13.27, 13.70, 22.22, 22.26, 26.86,
31.82, 34.06, 110.46, 115.25, 115.46, 117.04, 118.17, 123.65, 125.37, 129.60, 129.67, 134.54, 134.57,
152.49, 152.57, 153.47, 160.34, 161.85, 162.76, 171.72. HRMS (ESI): m/z 383.16509 (M+H+),
405.14697 (M+Na+).
3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl pentanoate (53). Yield: 0.122 g, 66%, white
solid, m.p.: 83–84 °C. 1H-NMR (CDCl3): δ 0.98 (t, J = 7.2 Hz, 3H, CH2CH3), 1.43–1.48 (m, J = 7.2 Hz,
2H, CH2CH2CH2CH3), 1.72–1.79 (m, J = 7.2 Hz, 2H, CH2CH2CH2CH3), 2.44 (s, 3H, CH3), 2.59 (t,
J = 7.2 Hz, 2H, CH2CH2CH2CH3), 4.02 (s, 2H, CH2Ph), 6.95 (t, J = 8.0 Hz, 2H, ArH), 7.05–7.09 (m,
2H, H-6 and H-8), 7.20–7.26 (m, 2H, ArH), 7.62 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 13.70,
15.47, 22.22, 26.85, 32.22, 34.06, 110.17, 115.26, 115.47, 118.12, 118.26, 124.62, 125.43, 129.67,
129.75, 134.33, 134.36, 146.98, 152.59, 152.90, 160.32, 161.54, 162.75, 171.69. HRMS (ESI): m/z
369.15012 (M+H+), 391.13209 (M+Na+), 407.10611 (M+K+).
3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl pentanoate (54). Yield: 0.122 g, 62%, white
solid, m.p.: 68–70 °C. 1H-NMR (CDCl3): δ 0.98 (t, J = 7.2 Hz, 3H, CH2CH2CH2CH3), 1.05 (t, J = 7.2 Hz,
3H, CH2CH2CH3), 1.43–1.56 (m, 4H, CH2CH2CH2CH3 and CH2CH2CH3), 1.72–1.79 (m, J = 7.2 Hz,
2H, CH2CH2CH2CH3), 2.60 (t, J = 7.2 Hz, 2H, COCH2), 2.78–2.82 (m, J = 7.6 Hz, 2H, CH2CH2CH3),
4.00 (s, 2H, CH2Ph), 6.94–6.98 (m, 2H, CH2PhH), 7.05 (d, J = 8.8Hz, 1H, H-6), 7.10 (s, 1H, H-8),
7.20–7.23 (m, 2H, CH2PhH), 7.60 (d, J = 8.4 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 13.70, 14.48, 22.22,
22.53, 26.86, 31.14, 32.01, 34.07, 110.41, 115.24, 115.45, 117.36, 118.11, 124.02, 125.48, 129.58,
129.66, 134.58, 134.61, 151.22, 152.46, 153.38, 160.34, 161.81, 162.77, 171.71. HRMS (ESI): m/z
397.18122 (M+H+), 419.16309 (M+Na+).
3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl pivalate (55). Yield: 0.157 g, 90%, white solid, m.p.:
157–158 °C. 1H-NMR (CDCl3): δ 1.37 (s, 9H, C(CH3)3), 2.44 (s, 3H, CH3), 4.06 (s, 2H, CH2Ph), 7.01
(d, J = 8.8 Hz, 1H, H-6), 7.06 (s, 1H, H-8), 7.19–7.26 (m, 5H, CH2Ph), 7.61 (d, J = 8.8 Hz, 1H, H-5).
13C-NMR (CDCl3): δ 15.51, 27.08, 32.99, 39.24, 110.06, 117.98, 118.29, 124.72, 125.33, 126.38,
128.28, 128.60, 138.75, 147.00, 152.94, 161.63, 176.52. HRMS (ESI): m/z 351.15890 (M+H+),
373.14087 (M+Na+), 389.11450 (M+K+).
3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl pivalate (56). Yield: 0.1 g, 87%, white solid,
m.p.: 113 °C. 1H-NMR (CDCl3): δ 1.41 (s, 9H, C(CH3)3), 2.43 (s, 3H, CH3), 4.06 (s, 2H, CH2Ph), 7.11
(s, 1H, H-8), 7.20–7.28 (m, 5H, CH2PhH), 7.66 (s, 1H, H-5). 13C-NMR (CDCl3): δ 15.55, 27.14,
33.08, 39.43, 112.26, 119.52, 123.06, 125.64, 125.94, 126.51, 128.27, 128.66, 138.38, 145.92, 148.81,
151.19, 161.06, 175.56. HRMS (ESI): m/z 385.12023 (M+H+), 407.10224 (M+Na+), 423.07644 (M+K+).

Molecules 2013, 18
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3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl pivalate (57). Yield: 0.180 g, 99%, white solid, m.p.:
1
105–106 °C. H-NMR (CDCl3): δ 1.15 (t, J = 7.6 Hz, 3H, CH2CH3), 1.38 (s, 9H, C(CH3)3), 2.87 (q,
J = 7.6 Hz, 2H, CH2CH3), 4.05 (s, 2H, CH2Ph), 7.01–7.03 (dd, J = 1.6, 8.4 Hz, 1H, H-6), 7.07 (d,
J = 2.0 Hz, 1H, H-8), 7.19–7.30 (m, 5H, CH2Ph), 7.61 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ
13.23, 22.29, 27.08, 32.57, 39.25, 110.34, 117.06, 118.04, 123.76, 125.30, 126.39, 128.21, 128.59,
138.95, 152.57, 152.83, 153.50, 161.97, 176.58. HRMS (ESI): m/z 365.17453 (M+H+), 387.15631
(M+Na+), 403.13040 (M+K+).
3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl pivalate (58). Yield: 0.184 g, 97%, white solid, m.p.:
1
138–139 °C. H-NMR (CDCl3): δ 1.04 (t, J = 6.4 Hz, 3H, CH2CH3), 1.38 (s, 9H, C(CH3)3), 1.52 (q,
J = 7.2 Hz, 2H, CH2CH2CH3), 2.81 (m, 2H, CH2CH2CH3), 4.04 (s, 2H, CH2Ph), 7.01 (d, J = 8.4 Hz,
1H, H-6), 7.07 (s, 1H, H-8), 7.19–7.26 (m, 5H, CH2Ph), 7.58 (d, J = 8.4 Hz, 1H, H-5). 13C-NMR
(CDCl3): δ 14.48, 22.48, 27.08, 31.15, 32.77, 39.25, 110.28, 117.39, 117.96, 124.14, 125.39, 126.39,
128.20, 128.57, 139.00, 151.21, 152.82, 153.42, 161.90, 176.54. HRMS (ESI): m/z 379.19072
(M+H+), 401.17258 (M+Na+), 417.14652 (M+K+).
4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl pivalate (59). Yield: 0.16 g, 84%, white solid,
m.p.: 103–104 °C. 1H-NMR (CDCl3): δ 1.16 (t, J = 7.6 Hz, 3H, CH2CH3), 1.38 (s, 9H, C(CH3)3), 2.87
(q, J = 7.6 Hz, 2H, CH2CH3), 4.00 (s, 2H, CH2Ph), 6.95 (t, J = 8.4 Hz, 2H, ArH), 7.03 (d, J = 8.8 Hz,
1H, H-6), 7.08 (s, 1H, H-8), 7.21–7.26 (m, 2H, ArH), 7.62 (d, J = 8.4 Hz, 1H, H-5). 13C-NMR
(CDCl3): δ 13.28, 22.27, 27.07, 31.83, 39.25, 110.37, 115.24, 115.45, 116.95, 118.11, 123.59, 125.34,
129.62, 129.69, 134.57, 134.60, 152.58, 152.94, 153.50, 160.33, 161.86, 162.76, 176.53. HRMS (ESI):
m/z 383.16508 (M+H+), 405.14694 (M+Na+), 421.11022 (M+K+).
3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl pivalate (60). Yield: 0.096 g, 52%, white solid,
m.p.: 136–138 °C. 1H-NMR (CDCl3): δ 1.38 (s, 9H, C(CH3)3), 2.45 (s, 3H, CH3), 4.02 (s, 2H, CH2Ph),
6.96 (t, J = 8.0 Hz, 2H, ArH), 7.01–7.06 (m, 2H, H-6 and H-8), 7.21–7.26 (m, 2H, ArH), 7.60 (d,
J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 15.48, 27.07, 32.24, 39.25, 110.11, 115.27, 115.48, 118.06,
118.19, 124.59, 125.37, 129.68, 129.76, 134.35, 134.38, 146.98, 152.94, 153.04, 160.33, 161.55,
162.76, 176.52. HRMS (ESI): m/z 369.15012 (M+H+), 391.13212 (M+Na+), 407.10589 (M+K+).
3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl pivalate (61). Yield: 0.160 g, 81%, white solid,
1
m.p.: 138–140 °C. H-NMR (CDCl3): δ 1.05 (t, J = 7.2 Hz, 3H, CH2CH3), 1.38 (s, 9H, C(CH3)3),
1.52–1.56 (m, J = 7.2 Hz, 2H, CH2CH2CH3), 2.81 (t, J = 7.6 Hz, 2H, CH2CH2CH3), 4.00 (s, 2H,
CH2Ph), 6.96 (t, J = 8.4 Hz, 2H, ArH), 7.02 (d, J =8.8 Hz, 1H, H-6), 7.07 (s, 1H, H-8), 7.20–7.23 (m,
2H, ArH), 7.59 (d, J = 8.8 Hz, 1H, H-5). 13C-NMR (CDCl3): δ 14.48, 22.53, 27.07, 31.14, 32.02,
39.25, 110.33, 115.24, 115.45, 117.28, 118.05, 123.98, 125.42, 129.59, 129.67, 134.60, 134.63,
151.22, 152.91, 153.41, 160.34, 161.82, 162.77, 176.53. HRMS (ESI): m/z 397.18136 (M+H+),
419.16318 (M+Na+).
3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl benzoate (62). Yield: 0.180 g, 97%, white solid, m.p.:
1
149–150 °C. H-NMR (CDCl3): δ 2.47 (s, 3H, CH3), 4.08 (s, 2H, CH2Ph), 7.18–7.27 (m, 7H, ArH),
7.53 (t, 2H, ArH), 7.67 (t, 2H, ArH), 8.21 (d, J = 7.6 Hz, 2H, ArH). 13C-NMR (CDCl3): δ 15.55, 33.01,

Molecules 2013, 18
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110.33, 118.18, 118.55, 124.88, 125.49, 126.41, 128.29, 128.62, 128.72, 128.91, 130.33, 134.02,
138.72, 147.03, 152.69, 152.99, 161.64, 164.62. HRMS (ESI): m/z 371.12762 (M+H+), 393.10954
(M+Na+), 409.08341 (M+K+).
3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl benzoate (63). Yield: 0.179 g, 88.6%, white solid,
1
m.p.: 133–135 °C. H-NMR (CDCl3): δ 2.46 (s, 3H, CH3), 4.08 (s, 2H, CH2Ph), 7.21–7.32 (m, 6H,
ArH), 7.53–7.57 (m, 2H, ArH), 7.67–7.72 (m, 2H, ArH), 8.23–8.25 (m, J = 7.2 Hz, 2H, ArH).
13C-NMR (CDCl3): δ 15.59, 33.10, 112.47, 119.71, 123.11, 125.71, 126.08, 126.54, 128.27, 128.68,
128.78, 130.53, 134.26, 138.36, 145.94, 148.67, 151.21, 161.08, 163.77. HRMS (ESI): m/z 405.08872
(M+H+), 427.07096 (M+Na+), 443.04450 (M+K+).
3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl benzoate (64). Yield: 0.149 g, 78%, white solid, m.p.: 138 °C.
1H-NMR (CDCl3): δ 1.17 (t, J = 6.8 Hz, 3H, CH2CH3), 2.88–2.90 (m, J = 7.2 Hz, 2H, CH2CH3), 4.06
(s, 2H, CH2Ph), 7.18–7.27 (m, 7H, ArH), 7.52–7.55 (m, 2H, ArH), 7.65–7.69 (m, 2H, ArH), 8.21 (d,
J = 6.4 Hz, 2H, ArH). 13C-NMR (CDCl3): δ 18.20, 27.29, 37.60, 115.58, 122.32, 123.18, 128.94,
130.41, 131.38, 133.21, 133.58, 133.69, 133.94, 135.31, 138.99, 143.94, 157.50, 157.60, 158.57,
166.90, 169.60. HRMS (ESI): m/z 385.14322 (M+H+), 407.12515 (M+Na+), 423.09884 (M+K+).
3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl benzoate (65). Yield: 0.159 g, 80.3%, white solid, m.p.: 120 °C.
1H-NMR (CDCl3): δ 1.05 (t, J = 7.2 Hz, 3H, CH2CH3), 1.52–1.57 (m, J = 7.2 Hz, 2H, CH2CH3), 2.83
(t, J = 7.6 Hz, 2H, CH2CH2CH3), 4.06 (s, 2H, CH2Ph), 7.18–7.27 (m, 7H, ArH), 7.48–7.55 (m, 2H,
13
ArH), 7.64–7.68 (m, 2H, ArH), 8.21 (d, J = 7.2 Hz, 2H, ArH). C-NMR (CDCl3): δ 14.51, 22.50,
31.19, 32.79, 110.56, 117.66, 118.18, 124.30, 125.56, 126.42, 128.21, 128.60, 128.72, 130.34, 134.03,
138.98, 151.24, 152.57, 153.46, 161.92, 164.64. HRMS (ESI): m/z 399.15917 (M+H+), 421.14128
(M+Na+), 437.11514 (M+K+).
3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl benzoate (66). Yield: 0.13 g, 67%, white solid,
1
m.p.: 151–153 °C. H-NMR (CDCl3): δ 2.48 (s, 3H, CH3), 4.04 (s, 2H, CH2Ph), 6.97 (t, J = 8.4 Hz,
2H, ArH), 7.20–7.26 (m, 4H, ArH), 7.52–7.56 (m, 2H, ArH), 7.65–7.69 (m, 2H, ArH), 8.21 (d, J = 7.6 Hz,
2H, ArH). 13C-NMR (CDCl3): δ 15.51, 32.25, 110.39, 115.29, 115.50, 118.26, 118.44, 124.75, 125.53,
128.72, 128.87, 129.69, 129.77, 130.33, 134.04, 134.35, 146.99, 152.79, 152.99, 160.35, 161.56,
162.78,164.61. HRMS (ESI): m/z 389.11849 (M+H+), 411.10049 (M+Na+), 427.07456 (M+K+).
4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl benzoate (67). Yield: 0.073 g, 36%, white solid,
1
m.p.: 70–71 °C. H-NMR (CDCl3): δ 1.18 (t, J = 7.2 Hz, 3H, CH2CH3), 2.89 (q, J = 7.2 Hz, 2H,
CH2CH3), 4.02 (s, 2H, CH2Ph), 6.96 (t, J = 8.0 Hz, 2H, ArH), 7.22–7.25 (m, 4H, ArH), 7.53–7.69 (m,
13
4H, ArH), 8.21 (d, J = 7.2 Hz, 2H, ArH). C-NMR (CDCl3): δ 18.27, 27.27, 36.85, 115.62, 120.24,
120.46, 122.21, 123.27, 128.77, 130.45, 133.70, 133.90, 134.61, 134.69, 135.31, 139.01, 139.54,
157.53, 157.70, 158.55, 166.82, 167.78, 169.59. HRMS (ESI): m/z 403.13421 (M+H+).
3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl benzoate (68). Yield: 0.176 g, 85%, white solid,
m.p.: 95–96 °C. 1H-NMR (CDCl3): δ 1.06 (t, J = 7.2 Hz, 3H, CH2CH3), 1.53–1.58 (m, J = 7.2 Hz, 2H,
CH2CH2CH3), 2.83 (t, J = 7.6 Hz, 2H, CH2CH2CH3), 4.02 (s, 2H, CH2Ph), 6.96 (t, J = 8.4 Hz, 2H,

Molecules 2013, 18
6082
ArH), 7.19–7.25 (m, 4H, ArH), 7.52–7.55 (m, 2H, ArH), 7.65–7.69 (m, 2H, ArH), 8.21 (d, J = 8.0 Hz,
13
2H, ArH). C-NMR (CDCl3): δ 14.51, 22.56, 31.18, 32.04, 110.60, 115.26, 115.47, 117.54, 118.26,
124.13, 125.60, 128.73, 128.87, 129.61, 129.68, 130.33, 134.05, 134.59, 134.62, 151.26, 152.66,
153.45, 160.35, 161.83, 162.78, 164.62. HRMS (ESI): m/z 417.14989 (M+H+), 439.13191 (M+Na+),
455.10528 (M+K+).
3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl benzenesulfonate (69). Yield: 0.138 g, 68%, white solid,
m.p.: 131–132 °C. 1H-NMR (CDCl3): δ 2.43 (s, 3H, CH3), 4.04 (s, 2H, CH2Ph), 6.84 (s, 1H, H-8), 7.06
(d, J = 8.8 Hz, 1H, H-6), 7.19–7.29 (m, 5H, CH2Ph), 7.53–7.58 (m, 3H, H-5 and PhSO3), 7.70 (t,
13
J = 7.6 Hz, 1H, PhSO3), 7.86 (d, J = 7.6 Hz, 2H, PhSO3). C-NMR (CDCl3): δ 15.54, 33.03, 110.61,
118.69, 119.57, 125.67, 125.80, 126.51, 128.31, 128.46, 128.64, 129.43, 134.70, 135.03, 138.45,
146.56, 150.76, 152.59, 161.20. HRMS (ESI): m/z 407.09446 (M+H+), 429.07635 (M+Na+),
445.05041 (M+K+).
3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl benzenesulfonate (70). Yield: 0.165 g, 75%, white
1
solid, m.p.: 154–155 °C. H-NMR (CDCl3): δ 2.41 (s, 3H, CH3), 4.05 (s, 2H, CH2Ph), 7.19–7.25 (m,
6H, ArH), 7.58–7.60 (m, 3H, ArH), 7.73 (m, 1H, ArH), 7.93 (d, J = 6.4 Hz, 2H, ArH). 13C-NMR
(CDCl3): δ 15.54, 33.13, 112.33, 120.38, 123.50, 126.11, 126.62, 126.78, 128.30, 128.60, 128.70,
129.47, 134.91, 135.37, 138.15, 145.50, 146.48, 150.83, 160.73. HRMS (ESI): m/z 441.05606
(M+H+), 463.03794 (M+Na+), 479.01170 (M+K+).
3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl benzenesulfonate (71). Yield: 0.187 g, 89%, white solid, m.p.:
1
57–58 °C. H-NMR (CDCl3): δ 1.11 (t, J = 7.2 Hz, 3H, CH2CH3), 2.84 (t, J = 7.2 Hz, 2H, CH2CH3),
4.01 (s, 2H, CH2Ph), 6.88 (s, 1H, H-8), 7.03 (d, J = 8.8 Hz, 1H, H-6), 7.16–7.24 (m, 5H, CH2Ph),
7.52–7.58 (m, 3H, H-5 and PhSO3), 7.67–7.70 (m, J = 7.2 Hz, 1H, PhSO3), 7.86 (d, J = 8.0 Hz, 2H,
PhSO3). 13C-NMR (CDCl3): δ 18.15, 27.28, 37.62, 115.83, 123.38, 123.66, 129.67, 130.88, 131.48,
133.24, 133.42, 133.61, 134.48, 139.76, 140.02, 143.69, 155.63, 157.23, 158.14, 166.51. HRMS (ESI):
m/z 421.11015 (M+H+), 443.09190 (M+Na+), 459.06604 (M+K+).
3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl benzenesulfonate (72). Yield: 0.155 g, 71%, white solid,
1
m.p.: 96 °C. H-NMR (CDCl3): δ 1.03 (br s, 3H, CH2CH3), 1.49 (br s, 2H, CH2CH3), 2.79 (br s, 2H,
CH2CH2CH3), 4.02 (s, 2H, CH2Ph), 6.84 (s, 1H, H-8), 7.06 (d, J = 6.8 Hz, 1H, H-6), 7.24 (m, 5H,
CH2Ph), 7.56 (br s, 3H, H-5 and PhSO3), 7.71 (br s, 1H, PhSO3), 7.87 (d, J = 6.0 Hz, 2H, PhSO3).
13C-NMR (CDCl3): δ 14.48, 22.43, 31.15, 32.81, 110.81, 118.71, 125.07, 125.86, 126.52, 128.21,
128.46, 128.62, 129.45, 134.71, 135.09, 138.69, 150.64, 150.80, 153.06, 161.48. HRMS (ESI): m/z
435.12627 (M+H+), 457.10839 (M+Na+), 473.08227 (M+K+).
4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl benzenesulfonate (73). Yield: 0.195 g, 89%, white
solid, m.p.: 93–94 °C. 1H-NMR (CDCl3): δ 1.14 (t, J = 7.6 Hz, 3H, CH2CH3), 2.85 (q, J = 7.6 Hz, 2H,
CH2CH3), 3.97 (s, 2H, CH2Ph), 6.87 (s, 1H, H-8), 6.94 (t, J = 8.4 Hz, 2H, CH2Ph), 7.07 (d, J = 8.4 Hz,
1H, H-6), 7.19–7.23 (m, 2H, CH2Ph), 7.55–7.60 (m, 3H, H-5 and PhSO3), 7.69–7.73 (m, 1H, PhSO3),
13
7.87 (d, J = 8.0 Hz, 2H, PhSO3). C-NMR (CDCl3): δ 13.22, 22.26, 31.87, 110.89, 115.28, 115.49,
118.26, 118.79, 124.53, 125.83, 128.44, 129.45, 129.65, 129.73, 134.27, 134.30, 134.74, 135.08,

Molecules 2013, 18
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150.73, 152.19, 153.15, 160.36, 161.44, 162.79. HRMS (ESI): m/z 439.10053 (M+H+), 461.08240
(M+Na+), 477.05639 (M+K+).
3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl benzenesulfonate (74). Yield: 0.153 g, 72%,
1
white solid, m.p.: 108–109 °C. H-NMR (CDCl3): δ 2.44 (s, 3H, CH3), 3.99 (s, 2H, CH2Ph), 6.85 (s,
1H, H-8), 6.93–6.97 (m, J = 8.4 Hz, 2H, CH2Ph), 7.07 (d, J = 8.8 Hz, 1H, H-6), 7.19–7.23 (m, 2H,
CH2Ph), 7.54–7.59 (m, 3H, H-5 and PhSO3), 7.69–7.71 (m, 1H, PhSO3), 7.86 (d, J = 7.6 Hz, 2H,
13
PhSO3). C-NMR (CDCl3): δ 15.50, 32.27, 110.65, 115.31, 115.52, 118.76, 119.47, 125.52, 125.86,
128.45, 129.44, 129.72, 129.80, 134.05, 134.09, 134.72, 135.03, 146.56, 150.84, 152.59, 160.36,
161.13, 162.80. HRMS (ESI): m/z 425.08559 (M+H+), 447.06760 (M+Na+), 463.04156 (M+K+).
3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl benzenesulfonate (75). Yield: 0.104 g, 46%,
1
white solid, m.p.: 109–110 °C. H-NMR (CDCl3): δ 1.04 (t, J = 7.2 Hz, 3H, CH2CH3), 1.48–1.54 (m,
J = 7.6 Hz, 2H, CH2CH2CH3), 2.79 (t, J = 7.6 Hz, 2H, CH2CH2CH3), 3.97 (s, 2H, CH2Ph), 6.86 (s, 1H,
H-8), 6.95 (t, J = 8.4 Hz, 2H, CH2Ph), 7.07 (d, J = 8.8 Hz, 1H, H-6), 7.19–7.22 (m, 2H, CH2Ph), 7.55–7.59
(m, 3H, H-5 and PhSO3), 7.69–7.73 (m, 1H, PhSO3), 7.88 (d, J = 7.6 Hz, 2H, PhSO3). 13C-NMR
(CDCl3): δ 14.48, 22.48, 31.13, 32.05, 110.85, 115.29, 115.50, 118.56, 118.76, 124.89, 125.90, 128.45,
129.45, 129.63, 129.70, 134.32, 134.72, 135.10, 150.72, 150.82, 153.07, 160.37, 161.40, 162.81.
HRMS (ESI): m/z 453.11683 (M+H+), 475.09903 (M+Na+), 491.07253 (M+K+).
3-Benzyl-4-methyl-2-oxo-2H-chromen-7-yl 4-methylbenzenesulfonate (76). Yield: 0.103 g, 49%, white
1
solid, m.p.: 138–139 °C. H-NMR (CDCl3): δ 2.43 (s, 3H, CH3), 2.46 (s, 3H, CH3), 4.03 (s, 2H,
CH2Ph), 6.82 (s, 1H, H-8), 7.08 (d, J = 8.8 Hz, 1H, H-6), 7.18–7.28 (m, 5H, CH2Ph), 7.33 (d, J = 8.0 Hz,
13
2H, PhSO3), 7.57 (d, J = 8.8 Hz, 1H, H-5), 7.72 (d, J = 8.0 Hz, 2H, PhSO3). C-NMR (CDCl3): δ
15.54, 21.79, 33.02, 110.59, 118.80, 119.49, 125.57, 125.79, 126.50, 128.31, 128.48, 128.63, 130.07,
131.96, 138.48, 146.00, 146.65, 150.88, 152.55, 161.26. HRMS (ESI): m/z 421.11003 (M+H+),
443.09190 (M+Na+), 459.06602 (M+K+).
3-Benzyl-6-chloro-4-methyl-2-oxo-2H-chromen-7-yl 4-methylbenzenesulfonate (77). Yield: 0.136 g,
60%, white solid, m.p.: 173–174 °C. 1H-NMR (CDCl3): δ 2.41 (s, 3H, CH3), 2.48 (s, 3H, CH3), 4.04 (s,
2H, CH2Ph), 7.16 (s, 1H, H-8), 7.19–7.27 (m, 5H, CH2PhH), 7.36 (d, J = 8.0 Hz, 2H, ArH), 7.60 (s,
13
1H, H-5), 7.80 (d, J = 7.6 Hz, 2H, ArH). C-NMR (CDCl3): δ 15.54, 21.83, 33.11, 112.23, 120.28,
123.60, 126.10, 126.61, 126.68, 128.30, 128.63, 128.69, 130.10, 132.32, 138.17, 145.57, 146.26,
146.61, 150.81, 160.78. HRMS (ESI): m/z 455.07186 (M+H+).
3-Benzyl-4-ethyl-2-oxo-2H-chromen-7-yl 4-methylbenzenesulfonate (78). Yield: 0.169 g, 78%, white
solid, m.p.: 66–68 °C. 1H-NMR (CDCl3): δ 1.13 (t, J = 7.6 Hz, 3H, CH2CH3), 2.46 (s, 3H, CH3), 2.85
(q, J = 7.6 Hz, 2H, CH2CH3), 4.01 (s, 2H, CH2Ph), 6.84 (d, J = 1.6 Hz, 1H, H-8), 7.07–7.10 (dd,
J = 1.6, 8.8 Hz, 1H, H-6), 7.18–7.26 (m, 5H, CH2Ph), 7.34 (d, J = 8.0 Hz, 2H, PhSO3), 7.57 (d, J = 8.8 Hz,
13
1H, H-5), 7.74 (d, J = 8.0 Hz, 2H, PhSO3). C-NMR (CDCl3): δ 18.14, 26.77, 27.26, 37.60, 115.83,
123.27, 123.83, 129.61, 130.74, 131.48, 133.22, 133.46, 133.60, 135.06, 137.05, 143.67, 150.98,
155.77, 157.18, 158.12, 166.55. HRMS (ESI): m/z 435.12593 (M+H+), 457.10761 (M+Na+),
473.08160 (M+K+).

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3-Benzyl-2-oxo-4-propyl-2H-chromen-7-yl 4-methylbenzenesulfonate (79). Yield: 0.159 g, 80%, white
1
solid, m.p.: 120 °C. H-NMR (CDCl3): δ 1.04 (t, J = 7.2 Hz, 3H, CH2CH3), 1.48 (q, J = 7.2 Hz, 3H,
CH2CH3), 2.47 (s, 3H, CH3), 2.79 (q, J = 7.6 Hz, 2H, CH2CH2CH3), 4.02 (s, 2H, CH2Ph), 6.81 (s, 1H,
H-8), 7.09 (d, J = 8.4 Hz, 1H, H-6), 7.19–7.25 (m, 5H, CH2Ph), 7.34 (d, J = 7.6 Hz, 2H, PhSO3), 7.55
13
(d, J = 8.8 Hz, 1H, H-5), 7.74 (d, J = 7.6 Hz, 2H, PhSO3). C-NMR (CDCl3): δ 14.48, 21.80, 22.44,
31.15, 32.80, 110.80, 118.59, 118.84, 124.98, 125.83, 126.51, 128.21, 128.48, 128.61, 130.07, 132.04,
138.71, 145.99, 150.76, 150.86, 153.03, 161.54. HRMS (ESI): m/z 449.14190 (M+H+), 471.12381
(M+Na+), 487.09789 (M+K+).
4-Ethyl-3-(4-fluorobenzyl)-2-oxo-2H-chromen-7-yl 4-methylbenzenesulfonate (80). Yield: 0.132 g,
58%, white solid, m.p.: 96–97 °C. 1H-NMR (CDCl3): δ 1.15 (t, J = 7.2 Hz, 3H, CH2CH3), 2.47 (s, 2H,
CH3), 2.85 (q, J = 7.2 Hz, 2H, CH2CH3), 3.97 (s, 2H, CH2Ph), 6.84 (s, 1H, H-8), 6.95 (t, J = 8.0 Hz,
2H, CH2Ph), 7.10 (d, J = 8.4 Hz, 1H, H-6), 7.21 (m, 2H, CH2Ph), 7.35 (t, J = 7.6 Hz, 2H, PhSO3), 7.59
13
(d, J = 8.8 Hz, 1H, H-5), 7.74 (d, J = 7.6 Hz, 2H, PhSO3). C-NMR (CDCl3): δ 13.22, 21.80, 22.27,
31.86, 110.89, 115.29, 115.50, 118.17, 118.96, 124.45, 125.77, 128.47, 129.64, 129.72, 130.08,
132.04, 134.27, 134.30, 146.02, 150.85, 152.23, 153.12, 160.37, 161.50, 162.80. HRMS (ESI): m/z
453.11738 (M+H+).
3-(4-Fluorobenzyl)-4-methyl-2-oxo-2H-chromen-7-yl 4-methylbenzenesulfonate (81). Yield: 0.145 g,
1
66%, white solid, m.p.: 95–96 °C. H-NMR (CDCl3): δ 2.44 (s, 3H, CH3), 2.47(s, 3H, CH3), 3.99 (s,
2H, CH2Ph), 6.83 (s, 1H, H-8), 6.93–6.97 (m, J = 8.4 Hz, 2H, CH2Ph), 7.09 (d, J = 8.8 Hz, 1H, H-6),
7.20–7.22 (m, 2H, CH2Ph), 7.34 (d, J = 7.6 Hz, 2H, PhSO3), 7.58 (d, J = 8.4 Hz, 1H, H-5), 7.72 (d,
13
J = 8.0 Hz, 2H, PhSO3). C-NMR (CDCl3): δ 15.51, 21.79, 32.26, 110.64, 115.31, 115.52, 118.88,
119.38, 125.42, 125.83, 128.47, 129.72, 129.80, 130.07, 131.98, 134.08, 134.11, 146.02, 146.63,
150.95, 152.56, 160.36, 161.19, 162.79. HRMS (ESI): m/z 439.10127 (M+H+), 461.08292 (M+Na+),
477.05669 (M+K+).
3-(4-Fluorobenzyl)-2-oxo-4-propyl-2H-chromen-7-yl 4-methylbenzenesulfonate (82). Yield: 0.134 g,
58%, white solid, m.p.: 110–111 °C. 1H-NMR (CDCl3): δ 1.05 (t, J = 7.2 Hz, 3H, CH2CH3), 1.49–1.54
(m, J = 7.2 Hz, 2H, CH2CH2CH3), 2.47 (s, 3H, CH3), 2.79 (t, J = 7.6 Hz, 2H, CH2CH2CH3), 3.98 (s,
2H, CH2Ph), 6.83 (s, 1H, H-8), 6.93–6.97 (m, J = 6.8 Hz, 2H, CH2Ph), 7.10 (d, J = 8.8 Hz, 1H, H-6),
7.19–7.22 (m, 2H, CH2Ph), 7.35 (d, J = 7.2 Hz, 2H, PhSO3), 7.56 (d, J = 8.8 Hz, 1H, H-5), 7.74 (d,
J = 6.8 Hz, 2H, PhSO3). 13C-NMR (CDCl3): δ 14.48, 21.80, 22.49, 31.14, 32.05, 110.84, 115.28,
115.50, 118.48, 118.90, 124.80, 125.87, 128.47, 129.62, 129.70, 130.07, 132.05, 134.31, 134.34,
146.01, 150.84, 150.89, 153.03, 160.37, 161.46, 162.80. HRMS (ESI): m/z 467.13229 (M+H+),
489.11399 (M+Na+), 505.08809 (M+K+).
3.2.6. Procedure for the Preparation of 3-Benzyl-7-methoxy-2H-chromen-2-one (83) [25]
Step 1: Preparation of 2-hydroxy-4-methoxybenzaldehyde (6) [35]
To the solution of compound 2,4-dimethoxybenzaldehyde (5, 10 g, 60 mmol, 1 equiv.) in dry
dichloromethane (200 mL) was added dropwise AlCl3 (20 g. 150 mmol, 2.5 equiv.) at room
temperature, the mixture was stirred for 1 h and poured into 3 mol/L HCl solution. The reaction

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mixture was extractrd with CH2Cl2 three times and the organic extracts were combined, washed with
brine and dried over MgSO4. The solvent was removed under reduced pressure. Purification of the
residue by flash column chromatography (PE-EA = 20:1) to afford 2-hydroxy-4-methoxybenzaldehyde
(6) as a white powder (7.917 g, 86.7%), m.p.: 35–36 °C. 1H-NMR (CDCl3): δ 3.86 (s, 3H, CH3), 6.43
(d, J = 2.4 Hz, 1H, PhH), 6.53–6.56 (dd, J = 2.4, 8.8 Hz, 1H, PhH), 7.43 (d, J = 8.8 Hz, 1H, PhH), 9.72
(s, 1H, OH), 11.49 (s, 1H, CHO).
Step 2: Preparation of ethoxycarbonylbenzylmethylene triphenylphosphorane (8a)
To a solution of benzyl bromide (0.3 mL, 2.53 mmol, 1.05 equiv.) in dry chloroform (20 mL),
ethoxycarbonyl methylene triphenylphosphorane (7, 0.835 g, 2.4 mmol, 1 equiv.) was added at room
temperature. After stirring for 30 min at r.t., the mixture was refluxed for 15 h. The solvent was
removed under reduced pressure to afford the phosphonium salt as an oil. This salt was dissolved in
water (50 mL) and dichloromethane (50 mL) was added. It was then made alkaline (phenolphthalein
colorless to pink) with 2 M NaOH. The dichloromethane layer was separated and the aqueous layer
was extracted with dichloromethane (50 mL × 2). The combined dichloromethane extract was dried
over MgSO4 and solvent was removed to give the phosphorane, which was recrystallised from
chloroform-hexane as yellowish needles (0.680 g, 81.3%), m.p.: 133–134 °C. MS (ESI): m/z 439.2
(M+H+).
Step 3: Preparation of (E)-ethyl 2-benzyl-3-(2-hydroxy-4-methoxyphenyl) acrylate (9a)
A mixture of compound 6 (0.858 g, 5.645 mmol, 1 equiv.) and compound 8a (3.045 g, 6.944 mmol,
1.23 equiv.) was refluxed at 85 °C in dry benzene (30 mL) for 15 h. The solvent was removed under
reduced pressure. The residue obtained was purified by flash column chromatography (PE-EA = 5:1)
to afford the crude product, which was recrystallised from chloroform-hexane as a white solid (1.233 g,
1
70%), m.p.:104–105 °C. H-NMR (CDCl3): δ 1.22 (t, J = 7.2 Hz, 3H, CH2CH3), 3.77 (s, 3H, OCH3),
3.87 (s, 2H, CH2Ph), 4.19 (q, J = 7.2 Hz, 2H, CH2CH3), 5.34–5.65 (br s, 1H, OH), 6.41–6.44 (m, 2H,
PhH), 7.12–7.28 (m, 6H, PhH), 7.94 (s, 1H, CH=C). MS (ESI): m/z 313.1 (M+H+), 330.1 (M+H2O),
335.1 (M+Na+), 351.1 (M+K+), 647.2 (2M+Na+).
Step 4: Preparation of 3-benzyl-7-methoxy-2H-chromen-2-one (83)
Compound 9a (6 mmol, 1.884 g) was heated at 220 °C for 2 h under nitrogen atmosphere, The
residue obtained was purified by flash column chromatography (PE-EA = 10:1) to afford the product, a
1
white to light green powder (1.449 g, 90%), m.p.: 102–103 °C. H-NMR (CDCl3): δ 3.85 (s, 5H,
OCH3, CH2Ph), 6.77–6.81 (m, 2H, PhH), 7.22–7.36 (m, 7H, PhH). MS (ESI): m/z 267.1 (M+H+),
289.1 (M+Na+).
3.2.7. Procedure for the Preparation of 3-(4-Fluorobenzyl)-7-methoxy-2H-chromen-2-one (84) [25]
Step 1: Preparation of ethoxycarbonyl-(4-fluorobenzyl)-methylenetriphenylphosphorane (8b) [35]
To the solution of 4-fluorobenzyl bromide (0.378 g, 2 mmol) in dry chloroform (16 mL),
ethoxycarbonylmethylene triphenylphosphorane (7, 0.68 g, 1.9 mmol) was added at room temperature.
After stirring for 30 min at rt, it was refluxed for 15 hr. The solvent was removed under reduced
pressure to give the phosphonium salt as an oil. This salt was dissolved in water (50 mL) and

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dichloromethane (50 mL) was added to it. It was then made alkaline (phenolphthalein colouless to
pink) with 2 M NaOH. The dichloromethane layer was separated and the aqueous layer was extracted
with dichloromethane (50 mL × 2). The combined dichloromethane extract was dried over MgSO4 and
solvent was removed to give the phosphorane which was used without further purification for the
next step.
Step 2: Preparation of (E)-ethyl 2-(4-fluorobenzyl)-3-(2-hydroxy-4-methoxyphenyl) acrylate (9b)
A mixture of 6 (0.189 g, 1.24 mmol) and 8b (1.52 mmol) was refluxed at 85 °C in dry benzene (12 mL)
for 15 h. The solvent was removed under reduced pressure. The residue obtained was purified by flash
column chromatography (PE-EA = 5:1) to afford the crude product, which was recrystallised from
1
chloroform-hexane as a white solid (0.206 g, 50%), m.p.: 114–115 °C. H-NMR (CDCl3): δ 1.24 (t,
J = 7.2 Hz, 3H, CH2CH3), 3.79 (s, 3H, OCH3), 3.82 (s, 2H, CH2Ph), 4.20 (q, J = 7.2 Hz, 2H, CH2CH3),
5.10 (br s, 1H, OH), 6.44–6.47 (m, 2H, PhH), 6.92–6.97 (m, 2H, PhH), 7.00–7.13 (m, 3H, PhH), 7.90
(s, 1H, CH=C). MS (ESI): m/z 331.1 (M+H+), 348.1 (M+H2O), 353.1 (M+Na+), 369.1 (M+K+).
Step 3: Preparation of 3-(4-fluorobenzyl)-7-methoxy-2H-chromen-2-one (84)
Compound 9b (0.66 g, 2 mmol) was heated at 220 °C for 3 h under a nitrogen atmosphere, The
residue obtained was purified by flash column chromatography (PE-EA = 10:1) to afford the product, a
1
white powder (0.408 g, 72%), m.p.: 94–95 °C. H-NMR (DMSO-d6): δ 3.76 (s, 2H, CH2Ph), 3.84 (s,
3H, OCH3), 6.92 (dd, J = 8.6, 2.4 Hz, 1H, H-6), 6.98 (d, J = 2.4 Hz, 1H, H-8), 7.11–7.16 (m, 2H, Ph-
13
H), 7.33 (dd, J = 8.6, 5.4 Hz, 2H, Ph-H) 7.57 (d, J = 8.6 Hz, 1H, H-5), 7.75 (s, 1H, H-4). C-NMR
(DMSO-d6): δ 35.46, 56.33, 100.85, 112.82, 113.13, 115.49, 115.70, 124.91, 129.45, 131.13, 135.21,
140.71, 154.92, 160.22, 161.41, 162.27, 162.62. HRMS (ESI): m/z 285.09185 (M+H+).
3.2.8. Preparation of 3-Benzoyl-7-hydroxycoumarin (85) [26]
To a mixture of 2,4-dihydroxybenzylaldehyde (10b, 0.138 g, 1 mmol) and ethyl benzoylacetate (16,
0.192 g, 1.1 mmol) in acetonitrile (4 mL) was added 2 drops of piperidine. The neat mixture was kept
stirring for 24 h at room temperature. The solvent was removed under reduced pressure. The products
were purified by flash column chromatography (PE-EA = 3:1) to afford a yellow solid (0.23 g, 86.5%),
m.p.: 220–221 °C. 1H-NMR (DMSO-d6): δ 6.81 (d, J = 2.0 Hz, 1H, H-8), 6.87 (dd, J = 8.8, 2.0 Hz, 1H,
H-6), 7.53 (t, J = 7.6 Hz, 2H, m-Ph), 7.65–7.73 (m, 2H, p-Ph, H-5), 7.86 (d, J = 7.2 Hz, 2H, o-Ph), 8.35
(s, 1H, H-4), 11.05 (s, 0.11H, OH). MS (ESI): m/z 267.1 (M+H+), 289.0 (M+Na+), 305.0 (M+K+).
3.2.9. Preparation of 3-benzoyl-7-methoxycoumarin (86) [26]
To a mixture of 2-hydroxyl-4-methoxybenzylaldehyde (10a, 0.152 g, 1 mmol, 1 equiv.) and
ethyl benzoylacetate (11, 0.192 g, 1 mmol, 1 equiv.) was added piperidine (0.25 mL) dropwise. The
neat mixture was kept stirring at room temperature until a pink solid was formed. The solid was then
dissolved in CH2Cl2 and neutralised with 20 mL HCl (1 M). After extracting with CH2Cl2, the organic
phase was dried over MgSO4 and concentrated. The crude product was then recrystallised from
CH2Cl2–PE to give a pure product as yellow needle-like crystals (0.269 g, 96%), m.p.: 149–150 °C.
1H-NMR (CDCl3): δ 3.92 (s, 3H, OCH3), 6.87 (d, J = 2.0 Hz, 1H, H-8), 6.90–6.93 (dd, J = 8.8, 2.0 Hz,