New α-methylene-γ-butyrolactone derivatives as potential fungicidal agents: Design, synthesis and antifungal activities

Article abstract of DOI:10.3390/molecules21020130

In consideration of the fact that the α-methylene-γ-butyrolactone moiety is a major bio-functional group in the structure of carabrone and possesses some agricultural biological activity, forty-six new ester and six new ether derivatives containing α-methylene-γ-butyrolactone moieties were synthesized, and their fungicidal activities against Colletotrichum lagenarium and Botrytis cinerea were investigated. Most of the synthesized compounds showed moderate to significant fungicidal activity. Among them, halogen atom-containing derivatives showed better activity than others, especially compounds 6a,d which exhibited excellent fungicidal activity against C. lagenarium, with IC₅₀ values of 7.68 and 8.17 μM. The structure-activity relationship (SAR) analysis indicated that ester derivatives with electron-withdrawing groups on the benzene ring showed better fungicidal activity than those with electron-donating groups. A quantitative structure-activity relationship (QSAR) model (R² = 0.9824, F = 203.01, S² = 0.0083) was obtained through the heuristic method. The built model revealed a strong correlation of fungicidal activity against C. lagenarium with the molecular structures of these compounds. These results are expected to prove helpful in the design and exploration of low toxicity and high efficiency α-methylene-γ-butyrolactone-based fungicides.

Full text of DOI:10.3390/molecules21020130

molecules
Article
New α-Methylene-γ-Butyrolactone Derivatives as
Potential Fungicidal Agents: Design, Synthesis and
Antifungal Activities
Yongling Wu, Delong Wang, Yanqing Gao, Juntao Feng * and Xing Zhang
Research & Development Center of Biorational Pesticide, Key Laboratory of Plant Protection Resources and Pest
Management of Ministry of Education, Northwest A & F University, Xinong Road 22, Yangling 712100, Shaanxi,
China; wuyongling39@126.com (Y.W.); rizhaoalong@163.com (D.W.); gaoyanqinggc@nwsuaf.edu.cn (Y.G.);
zhxing1952@126.com (X.Z.)
* Correspondence: fengjt67@hotmail.com; Tel./Fax: +86-29-8709-2122
Academic Editor: Thomas J. Schmidt
Received: 10 December 2015 ; Accepted: 19 January 2016 ; Published: 22 January 2016
Abstract: In consideration of the fact that the
bio-functional group in the structure of carabrone and possesses some agricultural biological activity,
forty-six new ester and six new ether derivatives containing -methylene- -butyrolactone moieties
α-methylene-γ-butyrolactone moiety is a major
α
γ
were synthesized, and their fungicidal activities against Colletotrichum lagenarium and Botrytis cinerea
were investigated. Most of the synthesized compounds showed moderate to significant fungicidal
activity. Among them, halogen atom-containing derivatives showed better activity than others,
especially compounds 6a
IC50 values of 7.68 and 8.17
,
d
which exhibited excellent fungicidal activity against C. lagenarium, with
M. The structure-activity relationship (SAR) analysis indicated that
µ
ester derivatives with electron-withdrawing groups on the benzene ring showed better fungicidal
activity than those with electron-donating groups. A quantitative structure-activity relationship
(QSAR) model (R2 = 0.9824, F = 203.01, S2 = 0.0083) was obtained through the heuristic method.
The built model revealed a strong correlation of fungicidal activity against C. lagenarium with the
molecular structures of these compounds. These results are expected to prove helpful in the design
and exploration of low toxicity and high efficiency α-methylene-γ-butyrolactone-based fungicides.
Keywords:
α-methylene-γ-butyrolactone; ester and ether derivatives; antifungal activity;
quantitative structure-activity relationships (QSAR); heuristic method
1. Introduction
Plant pathogenic fungi remain a main cause of plant diseases, which can infect any tissue of
a plant and cause severe yield agricultural product losses [
phyto-fungal mycotoxins can be harmful to animal and human health [
and Botrytis cinerea are the most common plant pathogenic fungi, and can cause cross-infections
between diseased and healthy plants [ ]. In addition, they cause significant reductions of crop yield
and quality [ ]. Traditional chemical fungicides play an important role in killing or controlling target
fungi directly, but sometimes cause adverse effects to the environment and food, and often create
1–
3]. Moreover, the presence of some
4]. Colletotrichum lagenarium
5–7
8
fungicide resistance [9]. Therefore, it is urgent to develop novel and effective fungicidal agents to
protect plants.
The
sesquiterpenoids (Figure 1). It exhibits multiple biological properties, including antibacterial, cytotoxic,
antiinflammatory, antioxidant, allergenic and antimicrobial activity [10 16]. In our previous research,
we found that carabrone (which is isolated from fruits of Carpesium macrocephalum) and its derivatives
α-methylene-γ-butyrolactone ring can be found as a key substructural unit in many
–
Molecules 2016, 21, 130; doi:10.3390/molecules21020130
www.mdpi.com/journal/molecules

Molecules 2016, 21, 130
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exhibited potent antifungal activity against C. lagenarium, and the structure-activity relationship
(SAR) analysis of these compounds indicated that the -methylene- -butyrolactone ring was a major
biofunctional group in the carabrone structure [17 20]. Besides, -monosubstituted compounds of the
-methylene- -lactone ring have also been synthesized, and we concluded that aromatic substituents
directly fused to the -position improved the potency more effectively than alkyl groups. Meanwhile,
α
γ
–
γ
α
γ
γ
the cytotoxicity was tested to ensure the selectivity of the fungicidal effects [21].
Figure 1. Some representative sesquiterpenoid structures.
It is virtually and economically impossible to develop and screen candidates with fungicidal
activity from among numberless compounds. The development of new quantitative structure-activity
relationship (QSAR) methods, with simple molecular indexes, is a promising shortcut to resolve
the cost and time issues [22]. The QSAR method enables the calculation of numerous quantitative
descriptors on the basis of molecular structural information and is very useful to optimize important
aspects such as fungicidal activity or toxicity. Meanwhile, QSAR is useful in provide further guidance
for the design and development of potential new fungicides [23,24].
In order to obtain novel natural product-based fungicides, two series of derivatives based on
γ
-monosubstituted α-methylene-γ-butyrolactone rings were synthesized on the basis of their molecular
similarity. The fungicidal activities of these compounds against C. lagenarium and B. cinerea were
investigated and their structures were characterized by 1H-NMR, 13C-NMR, and HRMS spectrometric
analysis. Meanwhile, the cytotoxicity was tested to ensure selectivity of the antifungal effects.
Moreover, a QSAR study was also performed on all of the derivatives using the Gaussian and
CODESSA software packages, which can correlate their structural features with their fungicidal activity.
2. Results and Discussion
2.1. Synthesis
Three kinds of intermediate compounds
4–6 were prepared by the cyclization of γ-hydroxy-
α
-methylene esters, which were obtained under mild aqueous reaction conditions through
indium-mediated Barbier allyl addition to aldehydes [25]. In order to investigate the structure-activity
relationships, different acids were reacted with the three kinds of intermediate compounds to obtain
the corresponding ester compounds. Then, six new ether compounds were obtained by reacting with
them with brominated alkanes. The structures of all the derivatives were characterized by 1H-NMR,
13C-NMR and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The synthetic
routes are shown in Scheme 1.

Molecules 2016, 21, 130
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Scheme 1. Synthetic route of the title compounds.
2.2. Fungicidal Activity and Structure-Activity Relationships (SAR)
2.2.1. Fungicidal Activity of the Title Compounds against C. lagenarium
The results of the fungicidal activity against C. lagenarium are summarized in Table 1, from
which it can be seen that the halogen atom-containing derivatives exhibited significant fungicidal
activity against this species. The following three main SARs were obtained: first, the introduction of
the electron-withdrawing groups Cl, Br, and CN onto the benzene ring dramatically increased the
potency. Compounds 4a–f
ten to twenty fold higher than the intermediate compounds 4–6, respectively. It was notable that the
IC50 values of 6a were approximately two fold lower than those of chlorothalonil, a commercial
fungicide. Meanwhile, the electron-donating groups CH3 and CH3O introduced onto the benzene
ring to give 4j–o 5h–l and 6g–l (IC50 > 126 M) greatly weakened the potency, which was similar to
that of the fatty acid derivatives 4p 5m and 6m. It can be concluded that the electronic effect of the
substituent on the benzene ring is important for the fungicidal activity of -methylene- -butyrolactone
groups. Second, intermediate compound was found to have higher activity than the corresponding
intermediate compounds and . Meanwhile, meta-substitution on the benzene ring (compounds
, 5a–e, and 6a–e (IC50 < 18 µM) exhibited fungicidal activity approximately
,
d
,
µ
,
α
γ
6
4
5
6a–p) was found to improve the potency significantly compared with the corresponding ortho- and
para-substitution patterns (compounds 4a–r and 5a–r). This result suggests that the steric effect should
be considered and substitution patterns on the benzene ring have an important influence on the
fungicidal activity. Third, all of the synthesized ether compounds exhibited lower fungicidal activity
against C. lagenarium than the corresponding ester compounds. It was notable that the cinnamic

Molecules 2016, 21, 130
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acid and fumalic acid derivatives 4q–r
,
5n and 6n containing an unsaturated bond showed higher
fungicidal activity against C. lagenarium.
Table 1. In vitro fungicidal activity of compounds against C. lagenarium and B. cinerea.
C. lagenarium
B. cinerea
IC50 a, µM
C. lagenarium
B. cinerea
IC50 a, µM
Compd.
Compd.
IC50 a, µM
pIC50
IC50 a, µM
pIC50
4a
4b
4c
4d
4e
4f
4g
4h
4i
13.96
8.99
12.74
15.62
8.76
´1.145
´0.954
´1.105
´1.194
´0.943
´1.158
´1.723
´1.817
´1.979
´2.284
´2.250
´2.276
´2.378
´2.327
´2.341
´2.315
´0.951
´1.648
´1.225
´1.249
´1.202
´1.127
´1.186
´1.898
´2.232
´2.334
´2.259
´2.317
29.81
22.13
27.31
24.09
30.24
23.01
60.61
77.00
111.77
198.67
193.28
209.12
243.35
224.16
230.85
236.62
21.50
56.32
30.57
34.51
34.60
22.93
36.10
95.02
193.75
229.37
193.87
259.27
5k
5l
5m
5n
5o
5p
5q
5r
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
6o
6p
291.95
283.99
173.74
10.27
413.72
499.33
428.93
519.42
7.68
9.24
10.27
8.17
9.70
´2.465
´2.453
´2.240
´1.012
´2.617
´2.698
´2.632
´2.716
´0.885
´0.966
´1.012
´0.912
´0.987
´1.864
´2.202
´2.099
´2.135
´2.210
´2.133
´2.188
´2.239
´1.385
´2.384
´2.425
´2.206
´2.378
´2.069
´0.624
306.85
303.36
205.50
20.57
456.91
524.54
446.08
548.63
23.32
29.08
27.45
25.99
27.15
101.94
179.62
147.84
163.84
196.45
161.43
179.33
202.97
40.26
280.01
298.26
207.99
279.96
139.85
8.31
14.38
52.87
65.63
95.38
192.44
177.96
188.93
238.97
212.50
219.44
206.51
8.93
44.51
16.77
17.74
15.94
13.41
15.35
79.07
170.80
215.94
181.69
207.63
4j
4k
4l
4m
4n
4o
4p
4q
4r
5a
5b
5c
5d
5e
5f
73.14
159.33
125.71
136.55
162.30
135.95
154.27
173.23
24.25
242.03
266.25
160.63
238.61
117.12
4.21
5g
5h
5i
4
5
6
Chlorothalonil b
5j
Note: a All 50% inhibition concentration (IC50) values are presented as the means
fungicide, chlorothalonil was used as the positive control.
˘
SD (n = 3), µ
M; b Commercial
2.2.2. Fungicidal Activity of the Title Compounds against B. cinerea
The results of the fungicidal activity against B. cinerea are summarized in Table 1, from which
we can see that compounds 4a 4q 5a and 6a exhibited moderate fungicidal activity against
–f,
,
–e,
n
–e
B. cinerea. All of the test compounds were less effective than against C. lagenarium.
2.3. QSAR Study on the Fungicidal Activity against C. lagenarium
In general, descriptors used in QSAR can be categorized as constitutional, topological, geometrical,
electrostatic, quantum chemical, and thermodynamic. There are many regression approaches available
for the CODESSA 2.7.15 software, such as the best multi-linear, multi-linear regression, principal
component analysis, partial least square regression, and heuristic regression [26]. In view of the
number of samples and descriptors used in this study, the heuristic regression was selected for
developing the QSAR model.
Determining the number of descriptors is an important step. The “breaking point” rule was used
in the improvement of the statistical quality of the model, as described in Figure 2, the R2 value of the
heuristic regression had a dramatic increase before the number of the descriptors reached 5, descriptors
with high t values were accepted and those with low t values were rejected. After the number of the
descriptors reached a certain value, the improvement of the regression model became less insignificant

Molecules 2016, 21, 130
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(
∆
R2 < 0.02–0.04) [27]. In addition, the number of the descriptors complies to the linear regressions
given by Equation (1):
N ě 3 pK ` 1q
(1)
where N is the number of sample compounds and K is the number of descriptors. Thus, the final model
with five descriptors was selected as the best model. The values of the five descriptors of compounds
can be found in Table 2.
Figure 2. The “breaking point” rule results.
Table 2. Fungicidal activity and structural descriptors of the title compounds.
Structural Descriptors
Compd.
pIC50
No.
qC
qH
qH
No
MAOEP
max
max
min
1
2
3
4
5
6
7
8
4a
4b
4c
4d
4e
4f
4g
4h
4i
´1.1450
´0.9540
´1.1050
´1.1940
´0.9430
´1.1580
´1.7230
´1.8170
´1.9790
´2.2840
´2.2500
´2.2760
´2.3780
´2.3270
´2.3410
´2.3150
´0.9210
´1.6480
´1.2250
´1.2490
´1.2020
´1.1270
´1.1860
´1.8980
´2.2320
´2.3340
´2.2590
´2.3170
´2.4650
1.6111
1.6111
1.6111
1.6111
1.6111
1.6111
1.5946
1.5946
1.5278
1.4872
1.4872
1.4872
1.5250
1.5250
1.5250
1.4688
1.5333
1.5000
1.6111
1.6111
1.6111
1.6111
1.6111
1.5946
1.5278
1.4872
1.4872
1.4872
1.5250
0.3570
0.3568
0.3571
0.3532
0.3571
0.3555
0.3558
0.3533
0.3575
0.3595
0.3577
0.3588
0.3658
0.3558
0.3616
0.3342
0.3441
0.3435
0.3597
0.3598
0.3514
0.3596
0.3581
0.3563
0.3602
0.3643
0.3603
0.3614
0.3741
1.9821
1.9820
1.9820
1.9751
1.9851
1.9669
1.9135
1.9134
1.9133
1.9132
1.9133
1.9133
1.9138
1.9133
1.9135
1.9125
1.9135
1.9135
1.9820
1.9820
1.9838
1.9667
1.9788
1.9132
1.9131
1.9126
1.9131
1.9131
1.9121
0.1606
0.1716
0.1628
0.1613
0.1712
0.1631
0.1708
0.1655
0.1603
0.1601
0.1602
0.1601
0.1598
0.1721
0.1608
0.1610
0.2228
0.1607
0.1635
0.1647
0.1594
0.1736
0.1649
0.1670
0.1590
0.1546
0.1587
0.1585
0.1568
0.1084
0.1084
0.1084
0.1078
0.1084
0.1085
0.1088
0.1088
0.1082
0.0821
0.0872
0.0885
0.0751
0.0735
0.0771
0.0843
0.0668
0.1074
0.1077
0.1078
0.1080
0.1079
0.1081
0.1092
0.1068
0.0871
0.0848
0.0859
0.0710
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
4j
4k
4l
4m
4n
4o
4p
4q
4r
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k

Molecules 2016, 21, 130
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Table 2. Cont.
Structural Descriptors
Compd.
pIC50
No.
qC
qH
qH
min
No
MAOEP
max
max
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
5l
5m
5n
5o
5p
5q
5r
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
6o
6p
´2.4530
´2.2400
´1.0120
´2.6170
´2.6980
´2.6320
´2.7160
´0.8850
´0.9660
´1.0120
´0.9120
´0.9870
´1.8640
´2.2020
´2.0990
´2.1350
´2.2100
´2.1330
´2.1880
´2.2390
´1.3850
´2.3840
´2.4250
1.5250
1.4286
1.5333
1.3333
1.3636
1.3636
1.4000
1.6111
1.6111
1.6111
1.6111
1.6111
1.5278
1.4872
1.4872
1.4872
1.5250
1.5250
1.5250
1.4688
1.5000
1.3333
1.3636
0.3593
0.3432
0.3472
0.3407
0.3408
0.3346
0.3412
0.3569
0.3574
0.3547
0.3571
0.3558
0.3577
0.3573
0.3579
0.3590
0.3665
0.3569
0.3632
0.3344
0.3468
0.3340
0.3340
1.9131
1.9123
1.9131
1.9117
1.9117
1.9118
1.9117
1.9820
1.9820
1.9817
1.9667
1.9669
1.9133
1.9138
1.9133
1.9133
1.9126
1.9133
1.9134
1.9126
1.9133
1.9117
1.9117
0.1752
0.1578
0.2218
0.1409
0.1409
0.1471
0.1406
0.1729
0.1703
0.1736
0.1726
0.1705
0.1700
0.1690
0.1698
0.1699
0.1701
0.1742
0.1692
0.1702
0.1689
0.1719
0.1720
0.0718
0.0713
0.0659
0.0717
0.0687
0.0822
0.0712
0.1084
0.1085
0.1085
0.1085
0.1085
0.1082
0.0823
0.0868
0.0884
0.0746
0.0727
0.0769
0.0841
0.1081
0.0700
0.0694
The best statistical model for the pIC50 data had the following statistical characteristics: R2 = 0.9824,
F = 203.01, S2 = 0.0083. This model included five descriptors in descending order according to their
statistical significance (t values), which is shown in Table 3, and the regression coefficients X and their
standard errors ∆X are also listed. The comparison between the experimental and predicted pIC50
is listed in Table 4, and the plot of the comparison between the predicted and experimental values is
shown in Figure 3. The five descriptor QSAR model equation is described in the following Equation (2)
(Figure 4):
pIC50 “ ´24.230 ´ 0.6261 ˆ No ´ 10.225 ˆ qC
` 12.075 ˆ MAOEP ` 12.464 ˆ qH
` 16.086 ˆ qH
(2)
min
max
max
N = 52, R2 = 0.9824, F = 203.01, S2 = 0.0083.
Figure 3. Experimental pIC50 vs. predicted pIC50
.

Molecules 2016, 21, 130
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Figure 4. Optimized structures and HOMO energy maps for compounds 5c,f from the DFT calculations
of Gaussian 03W. The green parts represent positive molecular orbitals, and the red parts represent
negative molecular orbitals.
Table 3. The best five-descriptor model.
Descriptor No.
X
˘∆X
t-Text
Descriptor
0
1
2
3
4
5
´2.4230 ˆ 10
4.1535
5.2603 ˆ 10´1
2.9561
´3.0433
´1.1903
´3.4591
15.0631
6.0544
Intercept
a
´
6.2613
ˆ
10´1
No
b
qC
´1.0225 ˆ 10
1.2075 ˆ 10
1.2464 ˆ 10
1.6086 ˆ 10
max
MAOEP c
8.0165 ˆ 10´1
qH
d
2.0587
qHmax
e
1.8059
8.9076
min
Note: Number of occupied electronic levels of atoms; b Max. net atomic charge for a C atom; c Max. atomic
a
orbital electronic population; d Max. net atomic charge for a H atom; e Min. net atomic charge for a C atom.
Table 4. The difference between the experimental pIC50 and predicted pIC50
.
No.
Compd. Calc. pIC50
Exp. pIC50
Difference No.
Compd. Calc. pIC50
Exp. pIC50
Difference
1
2
3
4
5
6
7
8
4a
4b
4c
4d
4e
4f
4g
4h
4i
´1.1403
´1.0128
´1.0988
´1.2533
´0.8153
´1.1974
´1.7783
´1.7431
´2.0285
´2.3147
´2.2508
´2.2089
´2.3273
´2.2477
´2.2751
´2.3821
´1.0839
´1.6793
´1.1940
´1.2255
´1.1129
´1.1579
´1.1386
´1.8257
´2.2060
´2.2643
´1.1450
´0.9540
´1.1050
´1.1940
´0.9430
´1.1580
´1.7230
´1.8170
´1.9790
´2.2840
´2.2500
´2.2760
´2.3780
´2.3270
´2.3410
´2.3150
´0.9510
´1.6480
´1.2250
´1.2490
´1.2020
´1.1270
´1.1860
´1.8980
´2.2320
´2.3340
0.0047
´0.0588
0.0062
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
5i
5j
5k
5l
5m
5n
5o
5p
5q
5r
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
´2.3856
´2.3869
´2.5972
´2.3140
´2.2529
´0.9584
´2.6263
´2.8078
´2.4778
´2.8579
´0.9917
´1.0220
´0.9105
´1.0028
´1.0382
´1.8806
´2.1368
´2.0781
´2.0438
´2.2545
´2.1958
´2.0901
´2.1068
´1.5095
´2.3109
´2.4467
´2.2590
´2.3170
´2.4650
´2.4530
´2.2400
´1.0120
´2.6170
´2.6980
´2.6320
´2.7160
´0.8850
´0.9660
´1.0120
´0.9120
´0.9870
´1.8640
´2.2020
´2.0990
´2.1350
´2.2100
´2.1330
´2.1880
´2.2390
´1.3850
´2.3840
´2.4250
´0.1266
´0.0699
´0.1322
0.1390
´0.0593
0.1277
´0.0129
´0.0394
´0.0553
0.0739
´0.0495
´0.0307
´0.0008
0.0671
0.0507
0.0793
0.0659
´0.0671
´0.1329
´0.0313
0.0310
0.0235
0.0891
0.0536
´0.0093
´0.1098
0.1542
´0.1419
´0.1067
´0.0560
0.1015
´0.0908
´0.0512
´0.0166
0.0652
0.0209
0.0912
´0.0445
´0.0628
0.0979
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
4j
4k
4l
4m
4n
4o
4p
4q
4r
5a
5b
5c
5d
5e
5f
´0.0309
0.0474
6m
6n
6o
6p
0.1322
0.0723
0.0260
0.0697
´0.1245
5g
5h
0.0731
´0.0217

Molecules 2016, 21, 130
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The internal validation and the “leave-one-out” cross-validation methods were used to validate
the developed QSAR model [28]. The internal validation was carried out by dividing the compound
data into three subsets A–C, with 17
etc., went into the first subset (A);
,
5
17 and 18 compounds respectively. The compounds 10
1
,
4
,
7
,
,
2
,
,
8,
11, etc., went into the second subset (B); and 3, 6, 9, 12, etc.,
went into the third subset (C). Two of the three subsets, (A and B), (A and C), and (B and C), consist
the training set while the remaining subset was treated as a test set. The correlation equations were
derived from each of the training sets using the same descriptors and then used to predict values for the
2
corresponding test set [29]. Internal validation results are presented in Table 5. The RTraining2 and RTest
are within 5% for all three sets, and the average values of RTraining2 = 0.9833 and RTest2 = 0.9855 were
close to the overall R2 value. Thus, the obtained QSAR model obtained demonstrated the predictive
power of 3-fold cross-validation. Meanwhile, the “leave-one-out” method was completed in a similar
manner to the internal validation. Every fourth compound (1, 5, 9, 13, etc.) was put into an external test
set, and the remaining compounds were left in the training set. The QSAR model containing the same
five descriptors was obtained with R2 = 0.9862 from the training set. When the same QSAR model
was applied on the test set, R2 = 0.9789 was observed. Therefore, the “leave-one out” cross-validation
results were also satisfactory.
Table 5. Internal validation of the QSAR model a.
Training Set
N
R2
F
S2
Test Set
N
R2
F
S2
A + B
B + C
A + C
34 0.9862 211.53 0.0095
35 0.9797 201.69 0.0112
35 0.9841 207.43 0.0090
C
A
B
18 0.9896 214.65 0.0086
17 0.9807 204.11 0.0104
17 0.9862 209.81 0.0092
0.9855 209.52 0.0094
Average
0.9833 206.83 0.0099 Average
a
Note: Compounds A:
1
41
,
4
,
,
7
,
,
10
47
,
,
13
,
16
,
19
,
22
,
25
,
28
3
,
31
,
34
,
37
,
40
,
43
,
46
,
49; Compounds B:
27 30 33 36 39
2
42
,
5
,
8
,
,
11
,
14
,
17
52
,
.
20,
23
,
26
,
29,
32,
35
,
38
,
44
50; Compounds C:
,
6,
9,
12
,
15
,
18
,
21
,
24
,
,
,
,
,
,
,
45
48,
51,
Descriptors involved in this model revealed the relationship between the compounds and the
fungicidal activity. The 1st and 3rd most important descriptors obtained in the model were the number
of occupied electronic levels of atoms and maximum atomic orbital electronic population, which
belong to quantum-chemically descriptors and have a significant effect on the fungicidal activity.
The number of occupied electronic levels of atoms depends directly on the quantum-chemically
calculated charge distribution in the molecules, and therefore describes the polar interactions between
molecules [30,31]. This study found that the derivatives with electron-withdrawing groups on the
benzene ring showed higher No values than those with electron-donating groups. Maximum atomic
orbital electronic population for a given atomic species in the molecule is an important index to
describe the nucleophilicity of the molecule, which is directly related to molecular nucleophilic capacity
and characterizes the susceptibility of the molecule to electrophilic attack [32]. In Equation (2), the
maximum atomic orbital electronic population and pIC50 are positively correlated, which suggested
that the electron withdrawing substitution groups of the derivatives are beneficial for the fungicidal
activity against C. lagenarium. In fact, the
α,β-unsaturated carbonyl system (Michael acceptor), which
had higher electron deficiency induced by electron-withdrawing groups, can be easily attacked by
bionucleophiles [33,34]. Therefore, the obtained QSAR study result partially met the above SAR
study conclusion.
The 2nd, 4th and 5th descriptors obtained in the model were the maximum net atomic charge
for a C atom, maximum net atomic charge for an H atom, and minimum net atomic charge for an H
atom. These three descriptors belong to electrostatic descriptors, and they reflect characteristics of
the charge distribution of the molecules [35,36]. Thus, the electrostatic descriptors play an important
role in influencing the fungicidal activity of compounds. In Equation (2), appearance with a positive
sign in the model indicated that a molecule with a higher descriptor value had a higher pIC50. On the

Molecules 2016, 21, 130
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contrary, a negative sign in the model indicated that a molecule with a lower descriptor value had
a higher pIC50.
2.4. Cytotoxic Activity of the Representative Compounds against Human Tumor Cells Line (HepG2)
As a fact, compounds containing the
α
-methylene-γ-butyrolactone structure often exhibit a high
toxicity potential against mammalian cells [37
,
38]. In order to ensure the selectivity of the fungicidal
effects, the cytotoxicity of 24 representative derivatives was tested in a human tumor cells line (HepG2).
The result is listed in Table 6, which indicated that the QSAR underlying the fungicidal and cytotoxic
effects of these representative compounds are different. For instance, compound 6a has the highest
fungicidal activity with IC50 = 7.68
µ
M (against C. lagenarium) but moderate cytotoxic activity with
M (against HepG2 cell line), while, compound 4i has low fungicidal activity with
M (against C. lagenarium) but high cytotoxic activity with IC50 = 5.3 M (against HepG2
-methylene- -butyrolactone
IC50 = 30.2
IC50 = 95.38
µ
µ
µ
cell line). Through QSAR studies on fungicidal and antitumor activity of
α
γ
derivatives, these are important points that need further investigation to seek high activity derivatives
with weak cytotoxicity.
Table 6. In vitro fungicidal activity of compounds against C. lagenarium and cytotoxic activity against
a human tumor cells line (HepG2).
No.
Compd.
IC50 (µM) (against C. lagenarium)
IC50 (µM) (against HepG2 Cell Line)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
4b
4e
4g
4i
4k
4o
4p
4q
5a
5d
5i
8.99
8.76
22.4
21.7
18.3
5.3
52.87
95.38
177.96
219.44
206.51
8.93
16.77
13.41
181.69
283.99
173.74
499.33
519.42
7.68
28.5
25.0
19.5
27.3
28.4
35.6
85.2
29.0
23.8
>131.7
38.4
30.2
20.9
18.5
22.0
58.6
15.7
>108.2
23.3
17.9
5l
5m
5p
5r
6a
6d
6f
6g
6l
6n
6o
4
8.17
73.14
159.33
154.27
24.25
242.03
160.63
117.12
6
3. Materials and Methods
3.1. General Information
Chlorothalonil was purchased from Xiangtan Huayuan Fine-Chem Co. Ltd. (Xiangtan, China).
4-Dimethylaminopyridine (DMAP), N,N-dicyclohexylcarbodiimide (DCC) and carboxylic acids were
purchased from J & K Chemical Ltd. (Beijing, China). Other reagents and solvents were obtained
locally. All solvents were dried, and redistilled before use. The water used was redistilled and
ion-free. Analytical thin-layer chromatography (TLC) was performed on silica gel GF254. Column
chromatographic (CC) purification was carried out using silica gel (200–300 mesh). Above silica gel

Molecules 2016, 21, 130
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was obtained from Qingdao Haiyang Chemical Co., Ltd. (Qingdao, China). The melting points of
the synthetic derivatives were determined on an X-6 apparatus (Beijing Tech., Beijing, China) and
are uncorrected. Nuclear magnetic resonance (NMR) experiments were performed on an Avance
400/500 MHz instrument (Bruker, Bremerhaven, Germany). HR-MS (ESI) were obtained using a Bruker
Apex-Ultra 7.0 T spectrometer. Reaction progress was monitored by thin-layer chromatography on
silica gel GF-254 with detection by UV light.
3.2. Synthetic Procedures
3.2.1. General Synthetic Procedure for the Intermediate Compounds
α
-(Bromomethyl)acrylic acid was synthesized according to our previous report [21].
Hydroxybenzaldehyde (122.1 mg, 1.0 mmol), -(bromomethyl) acrylic acid (198.0 mg, 1.2 mmol),
α
and indium powder (136.0 mg, 1.2 mmol) were added to THF (10.0 mL) at room temperature. 6.0 M
HCl was added to the above mixture when the starting aldehyde disappeared according to TLC
analysis and stirring was continued for 6 hours. Then, the mixture was extracted with ethyl acetate
(3
ˆ
10 mL) and the organic phase dried over anhydrous Na2SO4 and evaporated under reduced
pressure. The resulting residue was purified using preparative chromatography on silica gel eluting
with 0%–40% ethyl acetate in petroleum ether. These intermediate compounds were used to prepare
the target compounds.
4-(4-Hydroxyphenyl)-2-methylenebutyrolactone (
(400 MHz, CDCl3): 2.88 (ddt, 1H, J = 17.2, 6.5, 2.6 Hz, CHHC=CH2), 3.30 (ddt, 1H, J = 17.2, 8.0,
2.0 Hz, CHHC=CH2), 5.43 (t, 1H, J = 7.1 Hz, OCH), 5.70 (t, 1H, J = 2.1 Hz, C=CHH), 6.28 (t, 1H,
4
). White crystals; mp: 79–81 ˝C; 87% yield; 1H-NMR
δ
J = 2.6 Hz, C=CHH), 6.84–7.11 (m, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 35.85, 79.14, 115.86,
123.05, 127.44, 130.59, 134.54, 156.76, 171.59; HR-MS (ESI): m/z calcd for C11H11O3 ([M + H]+) 191.0703,
found 191.0703.
4-(2-Hydroxyphenyl)-2-methylenebutyrolactone (
2.95 (ddt, 1H, J = 17.4, 5.9, 2.7 Hz, CHHC=CH2), 3.42 (ddt, 1H, J = 17.4, 8.4, 2.4 Hz, CHHC=CH2), 5.66
(t, 1H, J = 2.4 Hz, C=CHH), 5.79 (dd, 1H, J = 8.3 6.1 Hz, OCH), 6.29 (t, 1H, J = 2.8 Hz, C=CHH), 6.86–7.23
(m, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
34.67, 76.23, 115.93, 120.13, 122.77, 126.04, 126.28, 129.65,
134.82, 153.67, 172.26; HR-MS (ESI): m/z calcd for C11H11O3 ([M + H]+) 191.0703, found 191.0703.
5
). Colourless oil; 81% yield; 1H-NMR (400 MHz, CDCl3):
δ
δ
4-(3-Hydroxyphenyl)-2-methylenebutyrolactone (
). White crystal ; mp: 78–79 ˝C; 81% yield; 1H-NMR
(400 MHz, CDCl3): 2.82 (ddt, 1H, J = 17.2, 6.3, 2.8 Hz, CHHC=CH2), 3.30 (ddt, 1H, J = 17.2, 8.1, 2.3 Hz,
CHHC=CH2), 5.41 (t, 1H, J = 7.4 Hz, OCH), 5.66 (t, 1H, J = 2.3 Hz, C=CHH), 6.25 (t, 1H, J = 2.7 Hz,
6
δ
C=CHH), 6.76–7.19 (m, 4H, ArH); 13C-NMR (100 MHz, CDCl3):
δ 35.91, 78.62, 112.44, 115.87, 117.09,
123.31, 130.16, 134.04, 141.10, 156.71, 171.55; HR-MS (ESI): m/z calcd for C11H11O3 ([M + H]+) 191.0703,
found 191.0703.
3.2.2. General Synthetic Procedure for Ester Compounds
4-Dimethylaminopyridine (DMAP, 30.0 mg, 0.2 mmol) and the appropriate intermediate
compounds 4, 5 or 6 (196.0 mg, 1.1 mmol) were added to anhydrous CH2Cl2 (15.0 mL)
containing the respective carboxylic acid (1.1 mmol). Then the mixture was cooled to 0 ˝C.
N,N-dicyclohexyl-carbodiimide (DCC, 226.0 mg, 1.1 mmol) dissolved in anhydrous CH2Cl2 (10.0 mL)
˝
was added dropwise into the mixture over a period of 10 min at 0 C and the mixture was then stirred
at room temperature until the reaction was complete according to the TLC analysis. Then, the mixture
was filtered. Finally, the residual organic layers were extracted by ethyl acetate (3
ˆ
30 mL) and
dried over anhydrous Na2SO4. After filtering, the solution was evaporated under vacuum. The target
compounds were purified by column chromatography on silica gel eluting with 0%–40% ethyl acetate
in petroleum ether. The structures of all ester derivatives were characterized by 1H-NMR, 13C-NMR,
and HR-ESI-MS, and the data are listed below.

Molecules 2016, 21, 130
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˝
4-[4-(2-Chlorobenzoyloxy)phenyl]-2-methylenebutyrolactone (4a) White solid; mp: 187.2–187.9 C; 40%
yield; H-NMR (400 MHz, CDCl3):
1
δ 8.05 (dd, J =7.8, 1.1 Hz, 1H, ArH), 7.56–7.47 (m, 3H, ArH),
7.44–7.37 (m, 4H, ArH), 6.33 (t, J = 2.8 Hz, 1H, C=CHH), 5.61–5.52 (m, 1H, OCH), 5.56 (d, J = 7.7 Hz,
1H, C=CHH), 3.50–3.37 (m, 1H, CHHC=CH2), 3.04–2.82 (m, 1H, CHHC=CH2); 13C-NMR (125 MHz,
CDCl3):
δ 170.06, 163.97, 150.70, 137.72, 134.50, 133.94, 133.41, 131.97, 131.44, 128.99, 126.77, 122.83,
122.16, 77.62, 77.05, 76.73, 36.36, 1.05; HR-MS (ESI): m/z calcd for C18H13ClNaO4 ([M + Na]+) 351.0394,
found 351.0395.
4-[4-(3-Chlorobenzoyloxy)phenyl]-2-methylenebutyrolactone (4b) White solid; mp: 168.8–169.2 ˝C; 54%
1
yield; H-NMR (500 MHz, CDCl3):
δ 8.24 (m, 1H, ArH), 7.69–7.56 (m, 1H, ArH), 7.54–7.34 (m, 3H,
ArH), 7.31–7.19 (m, 3H, ArH), 6.37 (dd, J = 14.9, 12.1 Hz, 1H, C=CHH), 5.76 (dd, J = 14.6, 12.2 Hz, 1H,
OCH), 5.60 (dd, J = 20.0, 12.6 Hz, 1H, C=CHH), 3.54–3.37 (m, 1H, CHHC=CH2), 3.02–2.88 (m, 1H,
CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 150.76, 137.71, 134.84, 133.86, 131.05, 130.22, 129.95,
128.31, 126.75, 122.74, 122.02, 77.31, 77.01, 76.75, 36.30, 29.70; HR-MS (ESI): m/z calcd for C18H13ClNaO4
([M + Na]+) 351.0394, found 351.0395.
˝
4-[4-(4-Chlorobenzoyloxy)phenyl]-2-methylenebutyrolactone (4c) White solid; mp: 171.3–171.6 C; 65%
yield; 1H-NMR (400 MHz, CDCl3):
8.30–8.02 (m, 2H, ArH), 7.68–7.14 (m, 6H, ArH), 6.33 (t, J = 2.8 Hz
δ
,
1H, C=CHH), 5.72 (t, J = 2.5 Hz, 1H, OCH), 5.60–5.47 (m, 1H, C=CHH), 3.43 (ddt, J = 17.1, 8.0, 2.4 Hz,
1H, CHHC=CH2), 2.94 (ddt, J = 17.1, 6.1, 2.9 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ
170.01, 150.82, 140.37, 137.63, 133.95, 131.59, 129.04, 126.73, 122.80, 122.16, 77.39, 77.04, 76.72, 36.31.
HR-MS (ESI): m/z calcd for C18H13ClNaO4 ([M + Na]+) 351.0394, found 351.0395.
4-[4-(2-Bromobenzoyloxy)phenyl]-2-methylenebutyrolactone (4d) White crystal; mp: 174.5–174.9 ˝C; 62%
1
yield; H-NMR (500 MHz, CDCl3):
δ 8.04 (dd, J = 7.5, 1.7 Hz, 1H, ArH), 7.91–7.68 (m, 1H, ArH),
7.56–7.08 (m, 6H, ArH), 6.36 (t, J = 2.8 Hz, 1H, C=CHH), 5.74 (t, J = 2.4 Hz, 1H, OCH), 5.61–5.50 (m, 1H,
C=CHH), 3.56–3.08 (m, 1H, CHHC=CH2), 3.05–2.67 (m, 1H, CHHC=CH2). 13C-NMR (125 MHz,
CDCl3):
δ 134.69, 133.30, 131.85, 127.36, 126.70, 122.73, 122.03, 77.32, 77.01, 76.75, 36.35, 29.70,
14.99.HR-MS (ESI): m/z calcd for C18H13BrNaO4 ([M + Na]+) 394.9890, found 394.9889.
4-[4-(3-Bromobenzoyloxy)phenyl]-2-methylenebutyrolactone (4e) White crystal; mp: 176.5–176.8 ˝C; 45%
yield; 1H-NMR (500 MHz, CDCl3):
δ 8.37 (s, 1H, ArH), 8.16 (d, J = 7.7 Hz, 1H, ArH), 7.80 (d, J = 7.9 Hz,
1H, ArH), 7.56–7.19 (m, 4H, ArH), 6.36 (t, J = 2.8 Hz, 1H, C=CHH), 5.75 (t, J = 2.4 Hz, 1H, OCH),
5.66–5.52 (m, 1H, C=CHH), 5.42 (dd, J = 10.6, 5.3 Hz, 1H, ArH), 3.57–3.37 (m, 1H, CHHC=CH2), 2.95 (s,
1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 136.73, 133.16, 132.05, 131.69, 130.22, 128.79, 126.91,
126.53, 122.77, 122.20, 78.63, 77.34, 77.03, 76.78, 40.03, 36.36, 29.72, 15.00. HR-MS (ESI): m/z calcd for
C18H13BrNaO4 ([M + Na]+) 394.9890, found 394.9889.
4-[4-(4-Bromobenzoyloxy)phenyl]-2-methylenebutyrolactone (4f) White crystal; mp: 175.1–175.6 ˝C; 52%
yield; 1H-NMR (500 MHz, CDCl3):
δ 8.10 (d, J = 8.5 Hz, 2H, ArH), 7.72 (t, J = 12.5 Hz, 4H, ArH), 6.38 (t,
J = 2.8 Hz, 1H, C=CHH), 5.76 (t, J = 2.4 Hz, 1H, OCH), 5.65–5.54 (m, 1H, C=CHH), 5.43 (dd, J = 10.7,
5.2 Hz, 2H, ArH), 3.55–3.36 (m, 1H, CHHC=CH2), 3.04–2.93 (m, 1H, CHHC=CH2); 13C-NMR (125 MHz,
CDCl3):
δ 150.78, 136.95, 132.05, 131.69, 129.05, 128.28, 126.76, 122.75, 122.08, 78.62, 77.28, 77.03, 76.78,
40.03, 36.36, 15.00. HR-MS (ESI): m/z calcd for C18H13BrNaO4 ([M + Na]+) 394.9890, found 394.9889.
1
4-[4-(3-Benzonitrile)phenyl]-2-methylenebutyrolactone (4g) Yellow oil; 54% yield; H-NMR (500 MHz,
CDCl3):
δ 8.52 (s, 1H, ArH), 8.45 (d, J = 8.0 Hz, 1H, ArH), 7.95 (d, J = 7.8 Hz, 1H, ArH), 7.70 (t, J = 7.9 Hz,
1H, ArH), 7.29 (t, J = 4.3 Hz, 4H, ArH), 6.36 (t, J = 2.8 Hz, 1H, 1H, C=CHH), 5.75 (t, J = 2.4 Hz, 1H,
OCH), 5.65–5.56 (m, 1H, C=CHH), 3.46 (ddd, J = 10.5, 5.7, 2.4 Hz, 1H, CHHC=CH2), 2.96 (ddt, J = 17.0,
6.1, 2.9 Hz, 1H, CHHC=CH2), 13C-NMR (125 MHz, CDCl3):
δ 163.13, 150.51, 138.01, 136.69, 134.16,
133.82, 130.69, 129.73, 126.83, 122.82, 121.90, 113.36, 77.26, 77.01, 76.76, 49.17, 36.29, 33.95, 25.62. HR-MS
(ESI): m/z calcd for C19H13NNaO4 ([M + Na]+) 342.0736, found 342.0740.

Molecules 2016, 21, 130
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1
4-[4-(4-Benzonitrile)phenyl]-2-methylenebutyrolactone (4h) Yellow oil; 57% yield; H-NMR (500 MHz,
CDCl3): 8.51–8.39 (m, 1H, ArH), 8.34 (t, J = 7.3 Hz, 2H, ArH), 7.98 (d, J = 7.8 Hz, 1H, ArH), 7.85 (s,
δ
2H, ArH), 7.73 (t, J = 7.9 Hz, 1H, ArH), 6.37 (t, J = 2.8 Hz, 1H, C=CHH), 6.25 (t, J = 2.9 Hz, 1H, ArH),
5.75 (t, J = 2.4 Hz, 1H, OCH), 5.71–5.64 (m, 2H, ArH), 5.61–5.55 (m, 1H, C=CHH), 3.49–3.41 (m, 1H,
CHHC=CH2), 3.38–3.28 (m, 1H, CHHC=CH2). 13C-NMR (125 MHz, CDCl3):
δ 137.00, 133.71, 132.43,
130.67, 129.88, 127.05, 126.80, 123.06, 122.84, 121.89, 77.26, 77.01, 76.75, 73.73, 49.17, 36.28, 33.95, 29.69,
25.64. HR-MS (ESI): m/z calcd for C19H13NNaO4 ([M + Na]+) 342.0736, found 342.0740.
4-(4-Benzoyloxyphenyl)-2-methylenebutyrolactone 4-(4-Benzoyloxyphenyl)-2-methylenebutyrolactone (4i
)
1
White solid; mp: 223.3–223.7 ˝C; 55% yield; H-NMR (500 MHz, CDCl3):
δ 8.25 (d, J = 8.3 Hz, 5H,
ArH), 7.70 (t, J = 7.4 Hz, 4H, ArH), 6.38 (s, 1H, C=CHH), 5.76 (d, J = 2.4 Hz, 1H, OCH), 5.63–5.55 (m,
1H, C=CHH), 4.11 (dd, J = 15.3, 7.9 Hz, 1H, CHHC=CH2), 3.47 (dd, J = 17.1, 8.1 Hz, 1H, CHHC=CH2);
13C-NMR (125 MHz, CDCl3):
δ 133.76, 130.21, 128.64, 126.72, 122.12, 78.70, 77.28, 77.03, 76.77, 40.04,
36.41, 29.72, 15.00. HR-MS (ESI): m/z calcd for C18H14NaO4 ([M + Na]+) 317.0784, found 317.0788.
4-[4-(2-Methylbenzoyloxy)phenyl]-2-methylenebutyrolactone (4j) White crystals; mp: 189.6–190.1 ˝C; 53%
1
yield; H-NMR (500 MHz, CDCl3):
δ 8.18 (d, J = 7.8 Hz, 1H, ArH), 7.58–7.46 (m, 1H, ArH), 7.40 (t,
J = 14.7 Hz, 2H, ArH), 7.35 (t, J = 7.7 Hz, 2H, ArH), 7.28 (t, J = 6.3 Hz, 2H, ArH), 6.35 (t, J = 2.8 Hz,
1H, C=CHH), 5.73 (t, J = 2.4 Hz, 1H, C=CHH), 5.64–5.40 (m, 1H, OCH), 3.45 (ddt, J = 17.1, 8.0, 2.4 Hz,
1H, CHHC=CH2), 3.05–2.85 (m, 1H, CHHC=CH2), 2.70 (s, 3H, ArCH3); 13C-NMR (125 MHz, CDCl3):
δ
170.00, 165.67, 151.00, 141.44, 137.39, 134.02, 132.91, 126.65, 125.97, 125.11, 122.96, 122.66, 122.35,
77.47, 77.30, 77.05, 76.79, 36.27, 21.95; HR-MS (ESI): m/z calcd for C19H16NaO4 ([M + Na]+) 331.0940,
found 331.0937.
˝
4-[4-(3-Methylbenzoyloxy)phenyl]-2-methylenebutyrolactone (4k) White crystals; mp: 186.2–186.6 C; 52%
yield; H-NMR (500 MHz, CDCl3):
1
δ 8.00 (d, J = 8.9 Hz, 2H, ArH), 7.57–7.14 (m, 6H, ArH), 6.33 (t,
J = 2.8 Hz, 1H, C=CHH), 5.72 (t, J = 2.5 Hz, 1H, C=CHH), 5.58–5.50 (m, 1H, OCH), 3.43 (ddt, J = 17.1, 8.0,
2.4 Hz, 1H, CHHC=CH2), 3.05–2.82 (m, 1H, CHHC=CH2), 2.45 (s, 3H, ArCH3); 13C-NMR (125 MHz,
CDCl3):
δ 170.03, 165.28, 151.07, 138.51, 137.37, 134.55, 134.01, 130.71, 129.19, 128.53, 127.37, 126.67,
122.26, 77.48, 77.28, 77.02, 76.77, 36.32, 21.30. HR-MS (ESI): m/z calcd for C19H16NaO4 ([M + Na]+
)
331.0940, found 331.0937.
4-[4-(4-Methylbenzoyloxy)phenyl]-2-methylenebutyrolactone (4l) White crystals; mp: 184.5–185.1 ˝C; 60%
1
yield; H-NMR (500 MHz, CDCl3):
δ 8.11 (d, J = 8.2 Hz, 2H, ArH), 7.56–7.19 (m, 6H, ArH), 6.35 (t,
J = 2.8 Hz, 1H, C=CHH), 5.74 (t, J = 2.5 Hz, 1H, C=CHH), 5.64–5.40 (m, 1H, OCH), 3.45 (ddt, J = 17.1, 8.0,
2.4 Hz, 1H, CHHC=CH2), 3.08–2.82 (m, 1H, CHHC=CH2), 2.48 (s, 3H, ArCH3); 13C-NMR (125 MHz,
CDCl3):
δ 169.99, 165.13, 151.11, 144.63, 138.51, 137.30, 134.03, 130.24, 129.34, 127.37, 126.58, 122.65,
122.27, 77.48, 77.27, 77.02, 76.76, 36.32, 21.77. HR-MS (ESI): m/z calcd for C19H16NaO4 ([M + Na]+
)
331.0940, found 331.0937.
4-[4-(2-Methoxylbenzoyloxy)phenyl]-2-methylenebutyrolactone (4m) White crystals; mp: 179.8–180.4 ˝C;
60% yield; 1H-NMR (500 MHz, CDCl3):
8.02 (dd, J = 8.0, 1.7 Hz, 1H, ArH), 7.56 (td, J = 8.2, 1.8 Hz,
δ
1H, ArH), 7.40–6.97 (m, 6H, ArH), 6.32 (t, J = 2.8 Hz, 1H, C=CHH), 5.71 (t, J = 2.5 Hz, 1H, C=CHH),
5.59–5.48 (m, 1H, OCH), 3.94 (s, 3H, ArOCH3), 3.42 (ddt, J = 17.1, 8.0, 2.4 Hz, 1H, CHHC=CH2), 2.93
(ddt, J = 9.3, 6.0, 2.9 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 170.08, 164.25, 159.97, 151.08,
137.20, 134.54, 134.06, 132.25, 126.56, 122.67, 122.37, 120.25, 112.25, 77.55, 77.30, 77.04, 76.79, 56.07, 36.34;
HR-MS (ESI): m/z calcd for C19H16NaO5 ([M + Na]+) 347.0889, found 347.0891.
4-[4-(3-Methoxylbenzoyloxy)phenyl]-2-methylenebutyrolactone (4n) White crystals; mp: 185.7–186.2 ˝C;
44% yield; 1H-NMR (500 MHz, CDCl3):
δ 7.85 (d, J = 7.7 Hz, 1H, ArH), 7.74 (s, 4H, ArH), 6.38 (s, 1H,
C=CHH), 5.76 (s, 1H, C=CHH), 5.66–5.56 (m, 1H, OCH), 5.44 (dd, J = 10.7, 5.2 Hz, 3H, ArH), 4.35 (s,
3H, ArOCH3), 4.11 (dd, J = 17.0, 9.5 Hz, 1H, CHHC=CH2), 3.47 (dd, J = 17.1, 8.1 Hz, 1H, CHHC=CH2);
13C-NMR (125 MHz, CDCl3):
δ 170.03, 164.28, 159.77, 129.67, 126.76, 122.64, 122.10, 120.32, 114.60,

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78.69, 77.28, 77.03, 76.78, 55.56, 40.04, 36.41, 29.72, 15.00. HR-MS (ESI): m/z calcd for C19H16NaO5
([M + Na]+) 347.0889, found 347.0891.
4-[4-(4-Methoxylbenzoyloxy)phenyl]-2-methylenebutyrolactone (4o) White crystals; mp: 184.5–185.2 ˝C;
51% yield; 1H-NMR (500 MHz, CDCl3):
δ 8.28–8.00 (m, 2H, ArH), 7.53–7.30 (m, 2H, ArH), 7.28–7.14 (m,
2H, ArH), 7.02–6.95 (m, 2H, ArH), 6.32 (t, J = 2.8 Hz, 1H, C=CHH), 5.71 (t, J = 2.5 Hz, 1H, C=CHH),
5.58–5.41 (m, 1H, OCH), 3.90 (s, 3H, ArOCH3), 3.49–3.33 (m, 1H, CHHC=CH2), 2.94 (ddd, J = 14.2, 6.3,
3.1 Hz, 1H, CHHC=CH2);13C-NMR (125 MHz, CDCl3):
δ 170.08, 164.83, 164.05, 159.97, 151.16, 137.23,
134.05, 132.36, 126.64, 122.70, 122.33, 121.55, 113.92, 77.46, 77.06, 76.74, 55.56, 36.32. HR-MS (ESI): m/z
calcd for C19H16NaO5 ([M + Na]+) 347.0889, found 347.0891.
4-[4-(Propionyloxy)phenyl]-2-methylenebutyrolactone (4p) Colourless oil; 68% yield; 1H-NMR (500 MHz,
CDCl3):
OCH), 5.39 (dd, J = 10.7, 5.2 Hz, 3H,CH3CH2), 3.44 (dd, J = 17.1, 8.1 Hz, 1H, CHHC=CH2), 3.03–2.90
(m, 1H, CHHC=CH2), 1.67 (s, 2H,CH3CH2); 13C-NMR (125 MHz, CDCl3):
178.99, 172.87, 150.84,
δ 6.35 (t, J = 2.8 Hz, 1H, C=CHH), 5.74 (t, J = 2.4 Hz, 1H, C=CHH), 5.63–5.46 (m, 1H,
δ
136.53, 126.63, 122.64, 78.68, 77.39, 77.06, 76.81, 39.98, 36.33, 27.75, 14.97. HR-MS (ESI): m/z calcd for
C14H14NaO4 ([M + Na]+) 269.0784, found 269.0786.
[4-(4-Hydroxy-3-methoxycinnamoyloxy)phenyl]-2-methylenebutyrolactone (4q) Yellow oil; 45% yield;
1H-NMR (400 MHz, CDCl3):
δ
7.80 (d, J = 15.9 Hz, 1H, ArOH), 7.36 (d, J = 8.6 Hz, 2H, ArH), 7.21 (dd,
J = 21.2, 12.6 Hz, 2H, ArH), 7.16–7.05 (m, 2H, CH=CH), 6.95 (d, J = 8.2 Hz, 1H, ArH), 6.47 (d, J = 15.9 Hz
,
1H, ArH), 6.32 (t, J = 2.8 Hz, 1H, C=CHH), 6.10 (s, 1H, ArH), 5.71 (t, J = 2.5 Hz, 1H, C=CHH), 5.58–5.44
(m, 1H, OCH),4.02–3.82 (m, 3H, ArOCH3), 3.49–3.29 (m, 1H, CHHC=CH2), 2.93 (ddt, J = 12.2, 6.0,
2.9 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 170.02, 165.56, 151.01, 148.60, 147.01, 137.172,
134.06, 126.63, 123.51, 122.18, 114.92, 114.22, 109.66, 76.72, 56.01, 49.16, 36.28, 33.94, 30.90, 29.69, 25.62.
HR-MS (ESI): m/z calcd for C21H18NaO6 ([M + Na]+) 389.0997, found 389.0995.
1
4-[4-(Cinnamoyloxy)phenyl]-2-methylenebutyrolactone (4r) Yellow oil; 43% yield; H-NMR (400 MHz,
CDCl3):
δ 7.88 (d, J = 16.0 Hz, 1H, ArH), 7.64–7.53 (m, 2H, ArH), 7.47–7.40 (m, 2H, ArH), 7.39–7.32
(m, 2H, ArH), 7.28–7.16 (m, 2H, CH=CH), 6.63 (d, J = 16.0 Hz, 1H, ArH), 6.32 (t, J = 2.8 Hz, 1H,
C=CHH), 5.71 (t, J = 2.5 Hz, 1H, C=CHH), 5.63–5.46 (m, 1H, OCH), 3.41 (ddt, J = 17.1, 8.0, 2.4 Hz,
1H, CHHC=CH2), 2.93 (ddt, J = 9.4, 6.0, 2.9 Hz, 1H, CHHC=CH2); 13C-NMR (100 MHz, CDCl3):
δ
170.06, 165.31, 150.88, 146.99, 137.31, 134.05, 130.86, 129.05, 128.37, 126.65, 122.72, 122.16, 116.99, 77.44,
77.06, 76.74, 36.30, 33.94, 30.91, 29.63. HR-MS (ESI): m/z calcd for C20H16NaO4 ([M + Na]+) 343.0940,
found 343.0941.
˝
4-[2-(3-Chlorobenzoyloxy)phenyl]-2-methylenebutyrolactone (5a) White solid; mp: 201.3–201.8 C; 54%
yield; 1H-NMR (500 MHz, CDCl3):
8.16 (t, J = 1.8 Hz, 1H, ArH), 8.08 (d, J = 7.8 Hz, 1H, ArH), 7.71–7.59
δ
(m, 1H, ArH), 7.53–7.45 (m, 2H, ArH), 7.43 (dt, J = 7.8, 3.9 Hz, 1H, ArH), 7.34 (dd, J = 9.4, 4.9 Hz, 1H,
ArH), 7.21 (dd, J = 8.0, 0.7 Hz, 1H, ArH), 6.24 (t, J = 2.9 Hz, 1H, C=CHH), 5.68 (dd, J = 8.4, 6.2 Hz, 1H,
C=CHH), 5.63 (t, J = 2.5 Hz, 1H, OCH), 3.32 (ddt, J = 17.4, 8.4, 2.6 Hz, 1H, CHHC=CH2), 2.90 (ddt,
J = 17.4, 5.9, 2.9 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 169.96, 163.75, 147.46, 135.04,
134.19, 133.51, 132.32, 130.46, 129.67, 128.34, 126.85, 126.40, 123.09, 122.85, 77.31, 77.06, 76.80, 35.20;
HR-MS (ESI): m/z calcd for C18H14ClO4 ([M + Na]+) 325.0574, found 325.0575.
4-[2-(4-Chlorobenzoyloxy)phenyl]-2-methylenebutyrolactone (5b) White solid; mp: 208.7–209.3 ˝C; 48%
yield; 1H-NMR (400 MHz, CDCl3):
δ 8.17–8.07 (m, 2H, ArH), 7.59–7.45 (m, 4H, ArH), 7.26 (s, 2H, ArH),
6.22 (s, 1H, C=CHH), 5.67 (dd, J = 8.4, 6.1 Hz, 1H, OCH), 5.61 (s, 1H, C=CHH), 3.30 (ddt, J = 17.4,
8.4, 2.6 Hz, 1H, CHHC=CH2), 2.90 (ddt, J = 17.4, 5.9, 2.9 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz,
CDCl3):
δ 168.96, 165.75, 146.45, 137.04, 134.29, 131.58, 129.66, 129.25, 128.81, 128.26, 126.76, 126.40,
123.09, 122.97, 77.35, 77.03, 76.72, 30.87. HR-MS (ESI): m/z calcd for C18H14ClO4 ([M + Na]+) 325.0572,
found 325.0575.

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4-[2-(2-Bromobenzoyloxy)phenyl]-2-methylenebutyrolactone (5c) White crystal; mp: 204.6–205.1 ˝C; 43%
yield; 1H-NMR (500 MHz, CDCl3):
8.05 (dd, J = 7.5, 1.9 Hz, 1H, ArH), 7.79 (dd, J = 7.7, 1.2 Hz, 1H,
δ
ArH), 7.56–7.16 (m, 6H, ArH), 6.25 (t, J = 2.8 Hz, 1H, C=CHH), 5.76 (dd, J = 8.3, 6.2 Hz, 1H, OCH),
5.66 (t, J = 2.5 Hz, 1H, C=CHH), 3.60–3.22 (m, 1H, CHHC=CH2), 2.93 (ddt, J = 17.4, 5.9, 2.8 Hz, 1H,
CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 164.19, 147.43, 134.88, 132.39, 131.97, 130.59, 129.59,
127.57, 126.81, 126.29, 122.88, 122.69, 122.42, 77.28, 77.03, 76.78, 73.60, 35.33.HR-MS (ESI): m/z calcd for
C18H14BrO4 ([M + H]+) 373.0070, found 373.0072.
4-[2-(3-Bromobenzoyloxy)phenyl]-2-methylenebutyrolactone (5d) White crystals; mp: 189.7–190.4 ˝C; 45%
1
yield; H-NMR (500 MHz, CDCl3):
δ 8.34 (t, J = 1.6 Hz, 1H, ArH), 8.14 (d, J = 7.8 Hz, 1H, ArH),
7.91–7.76 (m, 1H, ArH), 7.54–7.40 (m, 3H, ArH), 7.36 (td, J = 7.6, 0.7 Hz, 1H, ArH), 7.23 (dd, J = 8.0,
0.6 Hz, 1H, ArH), 6.25 (t, J = 2.9 Hz, 1H, C=CHH), 5.69 (dd, J = 8.3, 6.2 Hz, 1H, OCH), 5.65 (t, J = 2.5 Hz
1H, C=CHH), 3.33 (ddt, J = 17.4, 8.4, 2.5 Hz, 1H, CHHC=CH2), 2.92 (ddt, J = 17.4, 5.9, 2.8 Hz, 1H,
CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
169.89, 163.60, 147.50, 137.07, 133.54, 133.12, 130.69,
,
δ
130.42, 129.65, 128.77, 126.83, 126.42, 123.15, 77.32, 77.06, 76.81, 73.61, 35.20. HR-MS (ESI): m/z calcd for
C18H14BrO4 ([M + H]+) 373.0070, found 373.0069.
4-[2-(4-Bromobenzoyloxy)phenyl]-2-methylenebutyrolactone (5e) White crystals; mp: 184.7–185.2 ˝C; 53%
yield; 1H-NMR (500 MHz, CDCl3):
δ 8.05 (dd, J = 23.8, 8.5 Hz, 2H, ArH), 7.70 (t, J = 11.9 Hz, 2H, ArH),
7.56–7.20 (m, 4H, ArH), 6.25 (t, J = 2.8 Hz, 1H, C=CHH), 5.69 (dd, J = 8.3, 6.2 Hz, 1H, OCH), 5.63 (t,
J = 2.4 Hz, 1H, C=CHH), 3.32 (ddt, J = 17.4, 8.4, 2.5 Hz, 1H, CHHC=CH2), 2.92 (ddt, J = 17.4, 5.9, 2.8 Hz,
1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 169.90, 164.22, 147.58, 133.55, 132.27, 131.65, 130.89,
130.62, 129.58, 127.66, 126.75, 126.44, 122.93, 77.27, 77.02, 76.76, 73.69, 35.16. HR-MS (ESI): m/z calcd for
C18H14BrO4 ([M + H]+) 373.0070, found 373.0069.
1
4-[2-(4-Benzonitrile)phenyl]-2-methylenebutyrolactone (5f) Yellow oil; 65% yield; H-NMR (500 MHz,
CDCl3):
δ 8.31 (d, J = 8.5 Hz, 2H, ArH), 7.86 (d, J = 8.5 Hz, 2H, ArH), 7.55–7.43 (m, 2H, ArH), 7.41–7.35
(m, 1H, ArH), 7.30–7.24 (m, 1H, ArH), 6.23 (t, J = 2.9 Hz, 1H, C=CHH), 5.68 (t, J = 7.3 Hz, 1H, OCH),
5.64 (t, J = 2.5 Hz, 1H, C=CHH), 3.33 (ddt, J = 17.4, 8.5, 2.5 Hz, 1H, CHHC=CH2), 3.02–2.93 (m, 1H,
CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 163.38, 147.52, 133.47, 132.59, 130.68, 129.48, 127.05,
126.81, 23.12, 122.85, 120.68, 117.59, 115.82, 77.30, 77.04, 76.79, 75.28, 73.86, 35.02. HR-MS (ESI): m/z
calcd for C19H13NNaO4 ([M + Na]+) 342.0736, found 342.0741.
4-(2-Benzoyloxyphenyl)-2-methylenebutyrolactone (5g) White solid; mp: 166.3–167.0 ˝C; 57% yield;
1H-NMR (500 MHz, CDCl3):
δ 8.22 (d, J = 7.3 Hz, 2H, ArH), 7.71 (t, J = 7.5 Hz, 1H, ArH), 7.57
(t, J = 7.8 Hz, 2H, ArH), 7.49 (t, J = 7.4 Hz, 1H, ArH), 7.47–7.42 (m, 1H, ArH), 7.35 (dd, J = 11.1, 4.0 Hz,
1H, ArH), 7.25 (d, J = 8.1 Hz, 1H, ArH), 6.24 (t, J = 2.8 Hz, 1H, C=CHH), 5.73 (dd, J = 8.2, 6.3 Hz,
1H, OCH), 5.63 (t, J = 2.4 Hz, 1H, C=CHH), 3.34 (ddt, J = 17.4, 8.4, 2.5 Hz, 1H, CHHC=CH2), 2.92
(ddt, J = 17.4, 5.9, 2.8 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 133.76, 130.21, 128.64,
126.72, 122.12, 78.70, 77.28, 77.03, 76.77, 40.04, 36.41, 29.72, 15.00. HR-MS (ESI): m/z calcd for C18H15O4
([M + H]+) 295.0964, found 295.0964.
˝
4-[2-(2-Methylbenzoyloxy)phenyl]-2-methylenebutyrolactone (5h) White crystals; mp: 172.8–173.4 C; 47%
yield; 1H-NMR (400 MHz, CDCl3):
8.21–8.12 (m, 1H, ArH), 7.55–7.49 (m, 1H, ArH), 7.49–7.39 (m, 2H,
δ
ArH), 7.38–7.28 (m, 3H, ArH), 7.26–7.19 (m, 1H, ArH), 6.22 (t, J = 2.9 Hz, 1H, C=CHH), 5.70 (dd, J = 8.3,
6.1 Hz, 1H, OCH), 5.61 (t, J = 2.5 Hz, 1H, C=CHH), 3.32 (ddt, J = 17.4, 8.4, 2.6 Hz, 1H, CHHC=CH2),
2.90 (ddt, J = 17.4, 5.9, 2.9 Hz, 1H, CHHC=CH2), 2.68 (s, 3H, ArCH3); 13C-NMR (125 MHz, CDCl3):
δ
170.05, 165.29, 147.67, 141.92, 133.66, 133.33, 132.55, 131.16, 129.52, 127.60, 126.52, 126.17, 122.96,
77.40, 77.08, 76.77, 73.66, 35.30, 22.08.HR-MS (ESI): m/z calcd for C19H16NaO4 ([M + Na]+) 331.0940,
found 337.0940.
4-[2-(3-Methylbenzoyloxy)phenyl]-2-methylenebutyrolactone (5i) White crystals; mp: 179.3–179.9 ˝C; 45%
yield; 1H-NMR (500 MHz, CDCl3):
δ
7.99 (d, J = 8.7 Hz, 2H, ArH), 7.48 (t, J = 8.0 Hz, 2H, ArH), 7.45–7.39
(m, 2H, ArH), 7.32 (t, J = 7.6 Hz, 1H, ArH), 7.21 (d, J = 8.0 Hz, 1H, ArH), 6.22 (t, J = 2.9 Hz, 1H, C=CHH),

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5.70 (dd, J = 8.3, 6.2 Hz, 1H, OCH), 5.60 (t, J = 2.5 Hz, 1H, C=CHH), 3.31 (ddt, J = 17.4, 8.4, 2.5 Hz,
1H, CHHC=CH2), 2.89 (ddt, J = 17.4, 5.9, 2.8 Hz, 1H, CHHC=CH2), 2.46 (s, 3H, ArCH3); 13C-NMR
(125 MHz, CDCl3):
δ 170.06, 165.06, 147.69, 138.77, 134.93, 133.65, 132.48, 130.76, 129.52, 128.69, 127.36,
126.56, 126.16, 122.93, 77.30, 77.05, 76.79, 73.66, 35.28, 21.32. HR-MS (ESI): m/z calcd for C19H16NaO4
([M + Na]+) 337.0940, found 337.0941.
4-[2-(4-Methylbenzoyloxy)phenyl]-2-methylenebutyrolactone (5j) White crystals; mp: 181.2–181.6 ˝C; 46%
yield; 1H-NMR (400 MHz, CDCl3):
δ
8.08 (d, J = 8.2 Hz, 2H, ArH), 7.49–7.38 (m, 2H, ArH), 7.36–7.28 (m,
3H, ArH), 7.24–7.19 (m, 1H, ArH), 6.22 (t, J = 2.9 Hz, 1H, C=CHH), 5.70 (dd, J = 8.3, 6.1 Hz, 1H, OCH),
5.60 (t, J = 2.5 Hz, 1H, C=CHH), 3.31 (ddt, J = 17.4, 8.4, 2.6 Hz, 1H, CHHC=CH2), 2.89 (ddt, J = 17.4
5.9, 2.9 Hz, 1H, CHHC=CH2), 2.47 (s, 3H, ArCH3); 13C-NMR (125 MHz, CDCl3):
170.26, 163.06,
,
δ
149.69,145.15, 138.77, 133.65, 132.49, 130.29, 129.53, 128.49, 126.51, 126.05, 122.95, 77.35, 77.03, 76.72,
73.71, 35.28, 21.83. HR-MS (ESI): m/z calcd for C19H16NaO4 ([M + Na]+) 331.0940, found 331.0937.
4-[2-(2-Methoxylbenzoyloxy)phenyl]-2-methylenebutyrolactone (5k) White crystals; mp: 177.8–178.6 ˝C;
51% yield; 1H-NMR (500 MHz, CDCl3):
δ 8.00 (dd, J = 7.7, 1.6 Hz, 1H, ArH), 7.59 (td, J = 8.5, 1.7 Hz,
1H, ArH), 7.41 (ddd, J = 15.7, 9.2, 4.6 Hz, 2H, ArH), 7.33–7.19 (m, 2H, ArH), 7.07 (dd, J = 12.2, 5.2 Hz,
2H, ArH), 6.24 (t, J = 2.9 Hz, 1H, C=CHH), 5.79 (dd, J = 8.2, 6.2 Hz, 1H, OCH), 5.61 (t, J = 2.5 Hz, 1H,
C=CHH), 3.95 (s, 3H, ArOCH3), 3.36 (ddt, J = 17.4, 8.3, 2.5 Hz, 1H, CHHC=CH2), 2.87 (ddt, J = 17.4, 5.9,
2.9 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 170.21, 164.40, 159.83, 147.61, 134.84, 133.89,
132.54, 129.32, 126.40, 125.81, 122.97, 122.72, 120.46, 118.38, 112.25, 77.31, 77.06, 76.80, 73.71, 56.01, 35.45.
HR-MS (ESI): m/z calcd for C19H16NaO5 ([M + Na]+) 347.0889, found 347.0889.
˝
4-[2-(3-Methoxylbenzoyloxy)phenyl]-2-methylenebutyrolactone (5l) White crystals; mp: 180.3–180.8 C; 50%
yield; 1H-NMR (500 MHz, CDCl3):
7.81 (d, J = 7.7 Hz, 1H, ArH), 7.76–7.65 (m, 1H, ArH), 7.55–7.40
δ
(m, 3H, ArH), 7.35 (t, J = 7.2 Hz, 1H, ArH), 7.30–7.22 (m, 2H, ArH), 6.25 (t, J = 2.9 Hz, 1H, C=CHH), 5.72
(dd, J = 8.3, 6.2 Hz, 1H, OCH), 5.63 (t, J = 2.5 Hz, 1H, C=CHH), 3.92 (s, 3H, ArOCH3), 3.42–3.22 (m, 1H,
CHHC=CH2), 3.02–2.76 (m, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 169.99, 164.76, 159.88,
147.70, 133.63, 132.44, 129.86, 129.54, 126.60, 126.24, 122.92, 122.56, 120.63, 114.65, 77.28, 77.02, 76.77,
73.69, 55.57, 35.24. HR-MS (ESI): m/z calcd for C19H16NaO5 ([M + Na]+) 347.0889, found 347.0889.
4-[2-(Butyryloxy)phenyl]-2-methylenebutyrolactone (5m) Colourless oil; 78% yield; 1H-NMR (500 MHz,
CDCl3):
δ
7.41–7.33 (m, 2H, ArH), 7.30–7.21 (m, 1H, ArH), 7.16–7.05 (m, 1H, ArH), 6.31 (t, J = 2.8 Hz
,
1H, C=CHH), 5.68 (t, J = 2.4 Hz, 1H, C=CHH), 5.61 (dd, J = 8.3, 6.3 Hz, 1H, OCH), 3.34 (ddt, J = 17.4
,
8.4, 2.5 Hz, 1H, CHHC=CH2), 2.86 (ddt, J = 17.4, 5.9, 2.8 Hz, 1H, CHHC=CH2), 2.61–2.50 (m, 2H,
CH3CH2CH2), 1.78 (dt, J = 14.8, 7.4 Hz, 2H, CH3CH2CH2), 1.05 (dd, J = 9.0, 5.9 Hz, 3H, CH3CH2CH2);
13C-NMR (125 MHz, CDCl3):
δ 171.75, 147.64, 133.87, 131.95, 129.47, 126.31, 77.34, 77.08, 76.83,
73.94, 36.12, 35.23, 18.41, 13.68. HR-MS (ESI): m/z calcd for C15H16NaO4 ([M + Na]+) 283.0840,
found 283.0841.
1
4-[2-(Cinnamoyloxy)phenyl]-2-methylenebutyrolactone (5n) Yellow oil; 48% yield; H-NMR (500 MHz,
CDCl3):
δ 7.84 (d, J = 15.9 Hz, 1H, ArH), 7.49–7.39 (m, 2H, ArH), 7.32 (t, J = 7.5 Hz, 1H, ArH), 7.29
(s, 1H, ArH), 7.24–7.17 (m, 2H, ArH), 7.01–6.97 (m, 1H, ArH), 6.48 (d, J = 15.9 Hz, 1H, ArH), 6.30 (t,
J = 2.7 Hz, 1H, C=CHH), 5.71 (dd, J = 8.2, 6.4 Hz, 1H, OCH), 5.66 (d, J = 7.3 Hz, 1H, C=CHH), 4.00 (s,
2H, CH=CH), 3.39 (dd, J = 17.5, 8.5 Hz, 1H, CHHC=CH2), 2.99–2.84 (m, 1H, CHHC=CH2); 13C-NMR
(125 MHz, CDCl3):
δ 148.74, 147.72, 129.49, 127.04, 126.21, 123.67, 122.95, 122.72, 114.93, 113.54, 109.70,
77.27, 77.01, 76.76, 74.01, 56.04, 35.16, 26.33. HR-MS (ESI): m/z calcd for C21H19O6 ([M + H]+) 367.1173,
found 317.1176.
˝
4-[3-(3-Chlorobenzoyloxy)phenyl]-2-methylenebutyrolactone (6a) White solid; mp: 205.7–206.4 C; 52%
yield; 1H-NMR (500 MHz, CDCl3):
8.20 (s, 1H, ArH), 8.10 (d, J = 7.7 Hz, 1H, ArH), 7.65 (dd, J = 8.0,
δ
1.0 Hz, 1H, ArH), 7.55–7.45 (m, 2H, ArH), 7.30–7.19 (m, 3H, ArH), 6.35 (t, J = 2.8 Hz, 1H, C=CHH), 5.74
(t, J = 2.4 Hz, 1H, C=CHH), 5.62–5.54 (m, 1H, OCH), 3.52–3.41 (m, 1H, CHHC=CH2), 2.97 (ddt, J = 12.2,
6.0, 2.9 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 163.87, 151.10, 141.83, 134.86, 133.76,

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131.04, 130.35, 129.90, 128.31, 122.93, 121.78, 118.66, 77.41, 76.88, 76.76, 36.21, 29.70. HR-MS (ESI): m/z
calcd for C18H13ClNaO4 ([M + Na]+) 351.0394, found 351.0395.
4-[3-(4-Chlorobenzoyloxy)phenyl]-2-methylenebutyrolactone (6b) White solid; mp: 209.8–210.5 ˝C; 64%
yield; 1H-NMR (400 MHz, CDCl3):
δ 8.22–8.03 (m, 2H, ArH), 7.61–7.36 (m, 3H, ArH), 7.33–7.14 (m, 3H,
ArH), 6.32 (t, J = 2.8 Hz, 1H, C=CHH), 5.71 (t, J = 2.5 Hz, 1H, C=CHH), 5.56 (dd, J = 7.8, 6.7 Hz, 1H,
OCH), 3.44 (ddt, J = 17.1, 8.1, 2.5 Hz, 1H, CHHC=CH2), 2.94 (ddt, J = 17.1, 6.2, 2.9 Hz, 1H, CHHC=CH2);
13C-NMR (125 MHz, CDCl3):
δ 164.24, 151.14, 141.80, 140.37, 133.73, 131.58, 130.12, 129.05, 127.72,
122.93, 121.85, 118.72, 77.52 ,76.91, 76.74, 36.21. HR-MS (ESI): m/z calcd for C18H13ClNaO4 ([M + Na]+)
351.0394, found 351.0394.
4-[3-(2-Bromobenzoyloxy)phenyl]-2-methylenebutyrolactone (6c) White crystals; mp: 175.3–175.8 ˝C; 56%
1
yield; H-NMR (500 MHz, CDCl3):
δ 8.06 (dd, J = 7.6, 1.7 Hz, 1H, ArH), 7.83–7.72 (m, 1H, ArH),
7.61–7.42 (m, 2H, ArH), 7.30 (d, J = 10.2 Hz, 4H, ArH), 6.38 (t, J = 2.8 Hz, 1H, C=CHH), 5.76 (dd,
J = 6.3, 3.9 Hz, 1H, C=CHH), 5.67–5.40 (m, 1H, OCH), 3.62–3.30 (m, 1H, CHHC=CH2), 3.05–2.88 (m,
1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 134.74, 133.35, 130.12, 127.40, 126.70, 122.91, 118.69,
77.28, 77.02, 76.77, 36.35, 29.71, 19.20. HR-MS (ESI): m/z calcd for C18H13BrNaO4 ([M + Na]+) 394.9889,
found 394.9892.
4-[3-(3-Bromobenzoyloxy)phenyl]-2-methylenebutyrolactone (6d) White crystals; mp: 178.6–178.9 ˝C; 63%
yield; 1H-NMR (500 MHz, CDCl3):
δ 8.31 (d, J = 52.5 Hz, 1H, ArH), 8.10 (dd, J = 52.3, 7.5 Hz, 1H, ArH),
7.84–7.72 (m, 1H, ArH), 7.54–7.34 (m, 2H, ArH), 7.33–7.17 (m, 3H, ArH), 6.36 (t, J = 2.8 Hz, 1H, C=CHH),
5.74 (t, J = 2.5 Hz, 1H, C=CHH), 5.66–5.46 (m, 1H, OCH), 3.60–3.36 (m, 1H, CHHC=CH2), 2.97 (ddt,
J = 17.1, 6.1, 2.9 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 136.72, 133.14, 132.05, 131.69,
130.17, 128.76, 126.91, 126.53, 122.94, 121.78, 118.66, 77.37, 76.87, 76.76, 36.21, 29.72, 15.00. HR-MS (ESI):
m/z calcd for C18H13BrNaO4 ([M + Na]+) 394.9894, found 394.9890.
4-[3-(4-Bromobenzoyloxy)phenyl]-2-methylenebutyrolactone (6e) White crystals; mp: 168.6–169.4 ˝C; 41%
yield; 1H-NMR (500 MHz, CDCl3):
δ 8.10 (d, J = 8.5 Hz, 2H, ArH), 8.00 (d, J = 8.4 Hz, 2H, ArH), 7.69
(dd, J = 24.8, 8.4 Hz, 4H, ArH), 6.37 (t, J = 2.8 Hz, 1H, C=CHH), 5.76 (t, J = 2.4 Hz, 1H, C=CHH), 5.61 (s,
1H, OCH), 4.35 (t, J = 6.8 Hz, 1H, CHHC=CH2), 3.48 (dd, J = 17.0, 8.1 Hz, 1H, CHHC=CH2). 13C-NMR
(125 MHz, CDCl3):
δ 150.78, 137.95, 133.05, 131.69, 129.05, 127.28, 126.76, 122.75, 122.08, 78.62, 77.28,
77.03, 76.78, 40.03, 36.36, 15.00. HR-MS (ESI): m/z calcd for C18H13BrNaO4 ([M + Na]+) 394.9890,
found 394.9889.
4-(3-Benzoyloxyphenyl)-2-methylenebutyrolactone (6f) White solid; mp: 204.5–204.8 ˝C; 52% yield;
1H-NMR (500 MHz, CDCl3):
δ 8.22 (d, J = 7.3 Hz, 2H, ArH), 7.68 (t, J = 7.5 Hz, 1H, ArH), 7.49
(t, J = 7.8 Hz, 1H, ArH), 7.32–7.20 (m, 5H, ArH), 6.35 (t, J = 2.8 Hz, 1H, C=CHH), 5.73 (t, J = 2.4 Hz,
1H, C=CHH), 5.62–5.52 (m, 1H, OCH), 3.46 (ddt, J = 17.1, 8.1, 2.4 Hz, 1H, CHHC=CH2), 2.98 (ddt,
J = 9.2, 6.0, 2.8 Hz, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 135.76, 131.21, 128.69, 126.77,
122.62, 78.70, 77.28, 77.03, 76.77, 42.04, 36.51, 29.79, 15.20. HR-MS (ESI): m/z calcd for C18H14NaO4
([M + Na]+) 317.0785, found 317.0784.
˝
4-[3-(2-Methylbenzoyloxy)phenyl]-2-methylenebutyrolactone (6g) White crystals; mp: 178.3–178.9 C; 57%
yield; H-NMR (500 MHz, CDCl3):
1
δ 8.18 (d, J = 7.8 Hz, 1H, ArH), 7.54–7.46 (m, 2H, ArH), 7.36 (t,
J = 7.7 Hz, 2H, ArH), 7.24 (dd, J = 13.8, 7.7 Hz, 3H, ArH), 6.35 (t, J = 2.8 Hz, 1H, C=CHH), 5.73 (t,
J = 2.4 Hz, 1H, C=CHH), 5.64–5.51 (m, 1H, OCH), 3.46 (ddt, J = 17.1, 8.1, 2.4 Hz, 1H, CHHC=CH2),
2.98 (ddt, J = 17.1, 6.1, 2.9 Hz, 1H, CHHC=CH2), 2.70 (s, 3H, ArCH3); 13C-NMR (125 MHz, CDCl3):
δ
165.62, 151.30, 141.68, 141.44, 133.81, 132.91, 132.02, 131.21, 130.02, 128.21, 125.98, 122.71, 122.06,
118.92, 77.26, 77.01, 76.76, 36.23, 21.96. HR-MS (ESI): m/z calcd for C19H16NaO4 ([M + Na]+) 331.0940,
found 331.0940.
˝
4-[3-(3-Methylbenzoyloxy)phenyl]-2-methylenebutyrolactone (6h) White crystals; mp: 177.6–178.2 C; 68%
yield; H-NMR (500 MHz, CDCl3):
1
δ 8.03 (s, 1H, ArH), 7.46 (ddd, J = 15.1, 9.9, 5.9 Hz, 3H, ArH),

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7.28 (d, J = 9.6 Hz, 4H, ArH), 6.35 (t, J = 2.8 Hz, 1H, C=CHH), 5.73 (t, J = 2.4 Hz, 1H, C=CHH),
5.66–5.52 (m, 1H, OCH), 3.50–3.39 (m, 1H, CHHC=CH2), 3.03–2.93 (m, 1H, CHHC=CH2), 2.48 (s, 3H,
ArCH3); 13C-NMR (125 MHz, CDCl3):
δ 170.05, 165.28, 152.07, 136.51, 137.36, 134.45, 134.61, 130.71,
129.69, 128.53, 127.37, 126.67, 122.26, 77.48, 77.28, 77.02, 76.77, 36.32, 21.30. HR-MS (ESI): m/z calcd for
C19H16NaO4 ([M + Na]+) 331.0942, found 331.0940.
4-[3-(4-Methylbenzoyloxy)phenyl]-2-methylenebutyrolactone (6i) White crystals; mp: 168.5–168.9 ˝C; 57%
yield; 1H-NMR (500 MHz, CDCl3):
δ 8.10 (d, J = 8.1 Hz, 2H, ArH), 7.48 (t, J = 7.8 Hz, 1H, ArH), 7.34 (d,
J = 8.0 Hz, 1H, ArH), 7.30–7.20 (m, 4H, ArH), 6.35 (t, J = 2.8 Hz, 1H, C=CHH), 5.73 (t, J = 2.5 Hz, 1H,
C=CHH), 5.70–5.40 (m, 1H, OCH), 3.56–3.36 (m, 1H, CHHC=CH2), 2.98 (ddt, J = 17.1, 6.0, 2.9 Hz, 1H,
CHHC=CH2), 2.34 (d, J = 144.3 Hz, 3H, ArCH3). 13C-NMR (125 MHz, CDCl3):
δ 169.99, 165.13, 151.11,
144.66, 141.64, 130.24, 130.01, 129.36, 127.37, 126.58, 122.79, 122.63, 122.00, 118.87, 77.27, 77.01, 76.76,
36.22, 21.77. HR-MS (ESI): m/z calcd for C19H16NaO4 ([M + Na]+) 331.0940, found 331.0941.
˝
4-[3-(2-Methoxylbenzoyloxy)phenyl]-2-methylenebutyrolactone (6j) White crystals; mp: 172.3–172.8 C; 45%
yield; 1H-NMR (500 MHz, CDCl3):
8.07–7.99 (m, 1H, ArH), 7.61–7.56 (m, 1H, ArH), 7.32–7.20 (m, 4H,
δ
ArH), 7.08 (t, J = 7.6 Hz, 2H, ArH), 6.34 (t, J = 2.8 Hz, 1H, C=CHH), 5.73 (t, J = 2.4 Hz, 1H, C=CHH),
5.62–5.43 (m, 1H, OCH), 3.97 (s, 3H, ArOCH3), 3.47–3.38 (m, 1H, CHHC=CH2), 2.97 (ddt, J = 17.1, 6.1,
2.9 Hz, 1H, CHHC=CH2). 13C-NMR (125 MHz, CDCl3):
δ 151.37, 141.52, 134.54, 133.87, 132.27, 129.92,
122.76, 122.54, 122.09, 120.27, 118.98, 112.26, 77.30, 77.02, 76.76, 56.07, 49.16, 36.23, 33.95, 25.63, 24.94.
HR-MS (ESI): m/z calcd for C19H16NaO5 ([M + Na]+) 347.0889, found 347.0890.
˝
4-[3-(3-Methoxybenzoyloxy)phenyl]-2-methylenebutyrolactone (6k) White crystals; mp: 183.7–184.2 C;
57% yield; 1H-NMR (500 MHz, CDCl3):
7.82 (d, J = 7.7 Hz, 1H, ArH), 7.73 (d, J = 7.7 Hz, 1H, ArH),
δ
7.47 (dt, J = 18.6, 7.8 Hz, 2H, ArH), 7.31–7.19 (m, 4H, ArH), 6.35 (t, J = 2.8 Hz, 1H, C=CHH), 5.73 (t,
J = 2.4 Hz, 1H, C=CHH), 5.62–5.55 (m, 1H, OCH), 3.92 (s, 3H, ArOCH3), 3.46 (ddt, J = 17.0, 8.1, 2.4 Hz,
1H, CHHC=CH2), 3.01–2.91 (m, 1H, CHHC=CH2). 13C-NMR (125 MHz, CDCl3):
δ 159.75, 151.34,
141.70, 133.78, 130.05, 129.67, 129.49, 122.95–122.49, 121.94, 120.39, 118.80, 114.51, 77.27, 77.01, 76.76,
55.49, 36.21, 29.70.HR-MS (ESI): m/z calcd for C19H16NaO5 ([M + Na]+) 347.0889, found 347.0889.
˝
4-[3-(4-Methoxybenzoyloxy)phenyl]-2-methylenebutyrolactone (6l) White crystals; mp: 182.6–183.3 C;
56% yield; H-NMR (500 MHz, CDCl3):
1
δ 8.23–8.07 (m, 2H, ArH), 7.45 (t, J = 8.0 Hz, 1H, ArH),
7.29–7.14 (m, 3H, ArH), 7.02–6.92 (m, 2H, ArH), 6.32 (t, J = 2.8 Hz, 1H, C=CHH), 5.70 (t, J = 2.5 Hz, 1H,
C=CHH), 5.55 (dd, J = 7.8, 6.8 Hz, 1H, OCH), 3.90 (s, 3H, ArOCH3), 3.43 (ddt, J = 17.1, 8.1, 2.5 Hz, 1H,
CHHC=CH2), 3.00–2.87 (m, 1H, CHHC=CH2); 13C-NMR (125 MHz, CDCl3):
δ 169.99, 164.80, 164.06,
151.44, 141.61, 133.83, 132.35, 130.00, 122.84, 122.60, 122.06, 121.52, 118.92, 113.93, 77.35, 77.06, 76.74,
55.56, 36.21.HR-MS (ESI): m/z calcd for C19H16NaO5 ([M + Na]+) 347.0889, found 347.0892.
4-(3-Propionyloxyphenyl)-2-methylenebutyrolactone (6m) Colourless oil; 56% yield; 1H-NMR (500 MHz,
CDCl3):
δ 7.42 (t, J = 8.3 Hz, 1H, ArH), 7.29 (s, 1H, ArH), 7.20 (d, J = 7.8 Hz, 1H, ArH), 7.09 (s, 1H,
ArH), 6.34 (t, J = 2.8 Hz, 1H, C=CHH), 5.72 (t, J = 2.4 Hz, 1H, C=CHH), 5.64–5.43 (m, 1H, OCH), 3.44
(ddt, J = 17.1, 8.1, 2.4 Hz, 1H, CHHC=CH2), 2.94 (ddt, J = 17.1, 6.0, 2.8 Hz, 1H, CHHC=CH2), 2.62 (q,
J = 7.5 Hz, 2H, CH3CH2), 1.29 (t, J = 7.5 Hz, 3H, CH3CH2); 13C-NMR (125 MHz, CDCl3):
δ 172.81,
151.14, 141.57, 133.78, 129.92, 122.78, 122.53, 121.75, 118.63, 77.23, 77.01, 76.75, 36.20, 27.73, 9.02. HR-MS
(ESI): m/z calcd for C14H14NaO4 ([M + Na]+) 269.0784, found 269.0784.
1
4-(3-Cinnamoyloxyphenyl)-2-methylenebutyrolactone (6n) Yellow oil; 34% yield; H-NMR (400 MHz,
CDCl3):
δ 7.87 (d, J = 16.0 Hz, 1H, ArH), 7.64–7.55 (m, 2H, CH=CH), 7.47–7.38 (m, 4H, ArH), 7.25–7.10
(m, 3H, ArH), 6.62 (d, J = 16.0 Hz, 1H, ArH), 6.31 (t, J = 2.8 Hz, 1H, C=CHH), 5.70 (t, J = 2.5 Hz, 1H,
C=CHH), 5.60–5.45 (m, 1H, OCH), 3.42 (ddt, J = 17.1, 8.1, 2.5 Hz, 1H, CHHC=CH2), 2.93 (ddt, J = 17.1,
6.0, 2.9 Hz, 1H, CHHC=CH2); 13C-NMR (100 MHz, CDCl3):
δ 169.99, 165.26, 151.17, 147.00, 141.64,
134.07, 133.83, 130.88, 130.01, 129.06, 128.38, 122.76, 121.88, 118.76, 116.98, 77.56,76.95, 76.78, 36.19.
HR-MS (ESI): m/z calcd for C20H16NaO4 ([M + Na]+) 343.0940, found 343.0941.

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3.2.3. General Synthetic Procedure for Ether Compounds
K2CO3 (13.8 mg, 10.0 mmol) and Cs2CO3 (3.2 mg, 1.0 mmol) as catalyst, intermediate compounds
or 6 (196.0 mg, 1.1 mmol), and acetonitrile (35.0 mL) were added into a round bottomed flask and
5
refluxed at 78 ˝C. Then, the appropriate brominated alkane (1.2 mmol) was slowly added into the
˝
mixture and stirred for 12 h at 78 C. The progress of the reaction was monitored by TLC. After complete
conversion, the suspension was filtered and washed with acetonitrile. Finally, the solution was dried
with anhydrous Na2SO4, filtered, and evaporated under vacuum. The obtained crude products
were also purified by column chromatography. The 1H-NMR, 13C-NMR, and HR-ESI-MS data are
listed below.
4-(2-Butoxyphenyl)-2-methylenebutyrolactone (5o) Yellow oil; 42% yield; 1H-NMR (500 MHz, CDCl3):
δ
7.38–7.30 (m, 2H, ArH), 7.04–6.89 (m, 2H, ArH), 6.33 (t, J = 2.8 Hz, 1H, C=CHH), 5.77 (dd, J = 8.4,
6.0 Hz, 1H, OCH), 5.67 (t, J = 2.4 Hz, 1H, C=CHH), 4.13–3.95 (m, 2H, CH3CH2CH2CH2O), 3.45 (ddt,
J = 17.4, 8.5, 2.6 Hz, 1H, CHHC=CH2), 2.92 (ddt, J = 17.4, 5.7, 2.8 Hz, 1H, CHHC=CH2), 1.86–1.76 (m,
2H, CH3CH2CH2CH2O), 1.57–1.47 (m, 2H, CH3CH2CH2CH2O), 1.05–0.98 (m, 3H, CH3CH2CH2CH2O);
13C-NMR (100 MHz, CDCl3):
δ 155.78, 134.92, 129.42, 126.12, 121.82, 120.40, 111.27, 77.29, 76.78, 75.21,
67.79, 35.04, 31.28, 30.92, 19.41, 13.83. HR-MS (ESI): m/z calcd for C15H18NaO3 ([M + Na]+) 269.1148,
found 269.1147.
4-(2-Propoxylphenyl)-2-methylenebutyrolactone (5p) Yellow oil; 38% yield; 1H-NMR (500 MHz, CDCl3):
δ
7.30 (dd, J = 13.1, 5.4 Hz, 1H, ArH), 6.90 (dd, J = 12.5, 10.8 Hz, 3H, ArH), 6.33 (t, J = 2.8 Hz, 1H, C=CHH),
5.71 (t, J = 2.4 Hz, 1H, C=CHH), 5.58–5.41 (m, 1H, OCH), 3.94 (t, J = 6.5 Hz, 2H, CH3CH2CH2O), 3.41
(ddt, J = 17.1, 8.1, 2.4 Hz, 1H, CHHC=CH2), 2.93 (ddt, J = 17.1, 6.1, 2.9 Hz, 1H, CHHC=CH2), 1.90–1.78
(m, 2H, CH3CH2CH2O), 1.12–0.97 (m, 3H, CH3CH2CH2O); 13C-NMR (125 MHz, CDCl3):
δ 170.14,
159.58, 141.41, 134.20, 129.93, 122.43, 117.30, 114.49, 111.51, 77.82, 77.28, 77.03, 76.77, 69.61, 22.57, 10.51.
HR-MS (ESI): m/z calcd for C14H16NaO3 ([M + Na]+) 255.0991, found 255.0992.
4-(2-Isopropoxylphenyl)-2-methylenebutyrolactone (5q) Yellow oil; 47% yield; 1H-NMR (500 MHz, CDCl3):
δ
7.33 (dd, J = 12.7, 6.6 Hz, 2H, ArH), 6.96 (dt, J = 12.8, 5.9 Hz, 2H, ArH), 6.32 (t, J = 2.9 Hz, 1H, C=CHH),
5.73 (dd, J = 8.4, 5.9 Hz, 1H, OCH), 5.67 (t, J = 2.4 Hz, 1H, C=CHH), 4.67 (dt, J = 12.1, 6.0 Hz, 1H,
(CH3)2CHO), 3.45 (ddt, J = 17.4, 8.5, 2.6 Hz, 1H, CHHC=CH2), 2.91 (ddt, J = 17.5, 5.7, 2.8 Hz, 1H,
CHHC=CH2), 1.38 (dd, J = 8.8, 6.1 Hz, 6H, (CH3)2CHO); 13C-NMR (125 MHz, CDCl3):
δ 170.74, 154.58,
135.17, 129.35, 129.06, 126.55, 121.63, 120.19, 112.42, 77.29, 77.04, 76.78, 75.52, 69.95, 34.95, 29.72, 22.01.
HR-MS (ESI): m/z calcd for C14H16NaO3 ([M + Na]+) 255.0991, found 255.0990.
1
4-(2-Ethoxyphenyl)-2-methylenebutyrolactone (5r) Yellow oil; 46% yield; H-NMR (400 MHz, CDCl3):
δ
7.31–7.25 (m, 3H, ArH), 6.95 (td, J = 7.5, 0.8 Hz, 1H, ArH), 6.28 (t, J = 2.9 Hz, 1H, C=CHH), 5.71 (dd,
J = 8.5, 5.8 Hz, 1H, OCH), 5.63 (t, J = 2.5 Hz, 1H, C=CHH), 4.06 (qd, J = 7.0, 2.6 Hz, 2H, CH3CH2O),
3.42 (dd, J = 17.4, 8.5 Hz, 1H, CHHC=CH2), 2.95–2.77 (m, 1H, CHHC=CH2), 1.40 (t, J = 7.0 Hz,
3H, CH3CH2O).13C-NMR (125 MHz, CDCl3):
δ 129.48, 126.34, 121.70, 120.42, 111.34, 77.29, 77.03,
76.71, 75.44, 63.64, 34.90, 14.73. HR-MS (ESI): m/z calcd for C13H14NaO3 ([M + Na]+) 241.0835,
found 241.0834.
4-(3-Butoxyphenyl)-2-methylenebutyrolactone (6o) Yellow oil; 47% yield; 1H-NMR (500 MHz, CDCl3):
δ
7.32 (dd, J = 13.2, 5.4 Hz, 2H, ArH), 6.91 (d, J = 9.0 Hz, 2H, ArH), 6.35 (t, J = 2.8 Hz, 1H, C=CHH), 5.73 (t,
J = 2.4 Hz, 1H, C=CHH), 5.63–5.40 (m, 1H, OCH), 4.01 (t, J = 6.5 Hz, 2H, CH3CH2 CH2CH2O), 3.43 (ddt,
J = 17.0, 8.0, 2.4 Hz, 1H, CHHC=CH2), 2.95 (ddt, J = 17.1, 6.1, 2.9 Hz, 1H, CHHC=CH2), 1.86–1.74 (m, 2H,
CH3CH2CH2CH2O), 1.58–1.47 (m, 2H, CH3CH2CH2CH2O), 1.09–0.96 (m, 3H, CH3CH2CH2CH2O);
13C-NMR (100 MHz, CDCl3):
δ 155.78, 134.92, 129.42, 126.12, 121.82, 120.40, 111.27, 77.29, 76.78, 75.21,
67.79, 35.04, 31.28, 30.92, 19.41, 13.83. HR-MS (ESI): m/z calcd for C15H18NaO3 ([M + Na]+) 269.1148,
found 269.1147.

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4-(3-Propoxylphenyl)-2-methylenebutyrolactone (6p) Yellow oil; 54% yield; 1H-NMR (500 MHz, CDCl3):
7.30 (dd, J = 13.1, 5.4 Hz, 1H, ArH), 6.90 (dd, J = 12.5, 10.8 Hz, 3H, ArH), 6.33 (t, J = 2.8 Hz, 1H, C=CHH),
δ
5.71 (t, J = 2.4 Hz, 1H, C=CHH), 5.58–5.41 (m, 1H, OCH), 3.94 (t, J = 6.5 Hz, 2H, CH3CH2CH2O), 3.41
(ddt, J = 17.1, 8.1, 2.4 Hz, 1H, CHHC=CH2), 2.93 (ddt, J = 17.1, 6.1, 2.9 Hz, 1H, CHHC=CH2), 1.90–1.78
(m, 2H, CH3CH2CH2O), 1.12–0.97 (m, 3H, CH3CH2CH2O); 13C-NMR (125 MHz, CDCl3):
δ 170.14,
159.58, 141.41, 134.20, 129.93, 122.43, 117.30, 114.49, 111.51, 77.82, 77.28, 77.03, 76.77, 69.61, 22.57, 10.51.
HR-MS (ESI): m/z calcd for C14H16NaO3 ([M + Na]+) 255.0991, found 255.0992.
3.3. Fungicidal Activity Bioassay
3.3.1. Preparation of Spore Suspension
The fungal pathogens C. lagenarium and B. cinerea was provided by the Agricultural Culture
˝
Collection of China (Yangling, Shaanxi, China). C. lagenarium was cultured for 2 weeks at 25
˘
1 C on
potato dextrose agar (PDA) while B. cinerea was cultured at 20 ˝C on the same medium after being
retrieved from the storage tube. Plates were flooded with sterile distilled water, and then conidia were
scraped with a glass rod. Mycelial debris was removed by filtration. The spores were harvested and
suspended in sterile distilled water containing 0.1% (v/v) Tween 20. The concentration of the spore
suspension was adjusted to 1.0 ˆ 106 spores/mL with sterilized distilled water following [21,39].
3.3.2. Spore Germination Assay
The tested samples (10.0 mg) dissolved in acetone (0.1 mL) were diluted with sterile distilled water
to prepare 10.0 mL stock solution, which was further diluted to prepare test solutions in which the final
concentration of acetone was <1% (v/v). A series of concentrations of tested samples and one control
(1% acetone with sterile distilled water) were separately tested for spore germination of C. lagenarium or
B. cinerea. The samples were inoculated with spore suspension of C. lagenarium or B. cinerea containing
1.0
ˆ
106 spores/mL. Aliquots of 10
µL of prepared spore suspension were placed on separate glass
˝
slides in triplicate. Slides containing the spores were incubated in a moisture chamber at 25 C for 6~8 h.
Each slide was then observed under the microscope for spore germination. Spores were considered to
have germinated if the length of the germ tube was at least half the length of the spore. Afterward,
spore germination was stopped by applying a drop of lactophenol-cotton blue to the inoculation
sites on plates. The numbers of generated spores were counted under a microscope (Olympus BX61,
Tokyo, Japan), and the percentage of germinated spores was calculated. Chlorothalonil was used as
the positive control [21,39].
3.4. Building and Validation of the QSAR Model
Firstly, the optimal conformers of the title compounds with the lowest energy were computed at
the DFT/6-31G (d) level using the Gaussian 03W package of programs [40]. Then, the calculated results
were changed into a form compatible with CODESSA 2.7.15 using Ampac 9.1.3 [41,42]. Finally, all of the
molecular descriptors involved in these compounds were calculated by CODESSA 2.7.15. In order to
find out which structural features play an important role in the fungicidal activity against C. lagenarium,
the heuristic method analysis was selected to generate the QSAR model. In this model, the statistical
criteria were indicated by the squared correction coefficient (R2), the squared standard error of the
estimates (S2), and the Fisher significance ratio (F). The tested IC50 values were converted into the
corresponding log IC50 values and used as dependent variables in the QSAR studies. The quality of the
final model was determined using both an internal validation and the “leave-one-out” cross-validation
methods [43].
4. Conclusions
In summary, forty-six ester and six ether derivatives containing
α-methylene-γ-butyrolactone
moieties were synthesized, and their fungicidal activities against C. lagenarium and B. cinerea was

Molecules 2016, 21, 130
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investigated. Halogen atom-containing derivatives showed better activity than others, especially
compounds 6a which exhibited excellent fungicidal activity against C. lagenarium. Both SAR and
QSAR studies indicated that the structural characteristics had an important influence on the fungicidal
activity, and electron withdrawing substituents on the -methylene- -butyrolactone derivatives
,d
α
γ
had a positive effect on the fungicidal activity. It was notable that the present set of compounds
consisted of racemic mixtures; it will be an interesting task for further studies to test the most active
compounds in optically pure form. The level of fungicidal activity and cytotoxic activity observed
with α-methylene-γ-butyrolactone derivatives provide great impetus for further work on the design
of high-activity and non-toxic crop-protection agents.
Acknowledgments: We greatly appreciate the funding support for this research provided by the National Natural
Science Foundation of China (Grant No. 31471800, 31272074). We also thank Du-qiang Luo for the HR-MS spectral
data and The Fourth Military Medical University (Xi’an, China) for the cytotoxicity testing results.
Author Contributions: Yongling Wu designed and carried out the experimental and wrote the paper;
Delong Wang and Yanqing Gao assisted in prepared the manuscript; Juntao Feng and Xing Zhang supervised the
whole experiment and provided technical guidance. All authors have read and approved the final manuscript.
Conflicts of Interest: The authors declare no conflict of interest.
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2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons by Attribution
(CC-BY) license (http://creativecommons.org/licenses/by/4.0/).