Diversity-Oriented Synthesis of Natural-Product-like Libraries Containing a 3-Methylbenzofuran Moiety for the Discovery of New Chemical Elicitors

Article abstract of DOI:10.1002/open.201600118

Natural products are a major source of biological molecules. The 3-methylfuran scaffold is found in a variety of plant secondary metabolite chemical elicitors that confer host-plant resistance against insect pests. Herein, the diversity-oriented synthesis of a natural-product-like library is reported, in which the 3-methylfuran core is fused in an angular attachment to six common natural product scaffolds—coumarin, chalcone, flavone, flavonol, isoflavone and isoquinolinone. The structural diversity of this library is assessed computationally using cheminformatic analysis. Phenotypic high-throughput screening of β-glucuronidase activity uncovers several hits. Further in vivo screening confirms that these hits can induce resistance in rice to nymphs of the brown planthopper Nilaparvata lugens. This work validates the combination of diversity-oriented synthesis and high-throughput screening of β-glucuronidase activity as a strategy for discovering new chemical elicitors.

Full text of DOI:10.1002/open.201600118

DOI: 10.1002/open.201600118
Diversity-Oriented Synthesis of Natural-Product-like
Libraries Containing a 3-Methylbenzofuran Moiety for the
Discovery of New Chemical Elicitors
+
[a]
+ [b]
[a]
[b]
[b]
Xingrui He , Xia Chen , Songbo Lin, Xiaochang Mo, Pengyong Zhou,
[a]
[c]
[c]
[a]
[a]
[b]
Zhihao Zhang, Yaoyao Lu, Yu Yang, Haining Gu, Zhicai Shang,* Yonggen Lou,* and
[a]
Jun Wu*
Natural products are a major source of biological molecules.
The 3-methylfuran scaffold is found in a variety of plant secon-
dary metabolite chemical elicitors that confer host-plant resist-
ance against insect pests. Herein, the diversity-oriented synthe-
sis of a natural-product-like library is reported, in which the 3-
methylfuran core is fused in an angular attachment to six
common natural product scaffolds—coumarin, chalcone, fla-
vone, flavonol, isoflavone and isoquinolinone. The structural di-
versity of this library is assessed computationally using chemin-
formatic analysis. Phenotypic high-throughput screening of b-
glucuronidase activity uncovers several hits. Further in vivo
screening confirms that these hits can induce resistance in rice
to nymphs of the brown planthopper Nilaparvata lugens. This
work validates the combination of diversity-oriented synthesis
and high-throughput screening of b-glucuronidase activity as
a strategy for discovering new chemical elicitors.
1
. Introduction
Plants possess innate immune responses to deter or overcome
co-evolution of plants with their biotic environments. NPs have
been and continue to be a major source of the biological mol-
ecules from which many drugs and pesticides, as well as elici-
[
1]
pests and attackers. These responses, their natural self-de-
fense mechanisms, are activated by the accumulation of chem-
ical elicitors; these elicitors are generated in plants or are pro-
[4]
tors, have been developed. Because many NPs are defense
molecules against other organisms, NPs are essential sources
[
2]
vided by the attackers. Because the chemical elicitors them-
selves are not toxic to pests or herbivores and decompose
easily in the environment, a good way to develop safe plant
[5]
of new chemical elicitors. Therefore, the synthesis and screen-
ing of small-molecule libraries based on NPs or NP-like struc-
tures is a significant means of developing new chemical
[
3]
protection agents is based on chemical elicitors.
[6]
Natural products (NPs), which have been optimized over
time in a long process of natural selection, are the result of the
elicitors.
Diversity-oriented synthesis (DOS), which aims to synthesize
libraries of diverse small molecules, has proven to be an essen-
[7]
tial tool for discovering bioactive small molecules. The incor-
poration of privileged molecular scaffolds has become an es-
sential element in DOS pathways. In this work, we used DOS
+
[
a] Dr. X. He, S. Lin, Z. Zhang, H. Gu, Prof. Z. Shang, Prof. J. Wu
Department of Chemistry, Zhejiang University
Hangzhou 310027 (P. R. China)
[7b,8]
E-mail: wujunwu@zju.edu.cn
to create NP-like libraries containing a 3-methylfuran core.
shangzc@zju.edu.cn
The 3-methylfuran framework is found in a variety of NPs
with diverse biological activities. Of particular interest are men-
+
[
b] Dr. X. Chen, X. Mo, P. Zhou, Prof. Y. Lou
State Key Laboratory of Rice Biology
Institute of Insect Science, Zhejiang University
Hangzhou 310058 (P. R. China)
[
9]
thofuran (monoterpene),
furanoeremophilane (sesquiter-
[10]
[11]
[12]
pene),
cacalol,
and tanshinone (quinone; Figure 1).
E-mail: yglou@zju.edu.cn
Moreover, these compounds are plant secondary metabolites,
[9–10,11b]
[
c] Y. Lu, Y. Yang
conferring host resistance against plant invaders.
There-
School of Biological and Chemical Engineering
Zhejiang University of Science and Technology
Hangzhou 310023 (P. R. China)
fore, we predict that the 3-methylfuran scaffold is an important
+
[
] These authors contributed equally to this work.
Supporting Information for this article can be found under http://
dx.doi.org/10.1002/open.201600118.
ꢀ
2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
This is an open access article under the terms of the Creative Commons
Attribution-NonCommercial-NoDerivs License, which permits use and
distribution in any medium, provided the original work is properly cited,
the use is non-commercial and no modifications or adaptations are
made.
Figure 1. Bioactive natural products that contain a 3-methylfuran core.
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Scheme 1. Diversity-oriented synthesis of 88 compounds based on six natural product frameworks. Reagents and conditions: a) KOH, ethyl 2-chloroacetoace-
tate, H O/MeOH (1:2.5), RT, 6 h, >90%; c) Cu, pyridine, DEG, 1758C, 10 h, ꢀ85%; d) NaH, ethyl formate, PhMe,
O/MeOH (6:1), RT, 5 days, ꢀ65%; b) KOH, H
8C–RT, 10 h; e) NaH, ethyl acetate, DME, 0–908C, 4.5 h; f) NaH, dimethyl carbonate, DME, 0–908C, 4.5 h; g) DDQ, PhMe, 1208C, 6 h, ꢀ75% (d+g); h) DDQ,
PhMe, 1208C, 6 h, ꢀ70% (e+h); i) DDQ, PhMe, 1208C, 6 h, ꢀ75% (f+i); j) DMF-DMA, DMF, 758C, 4 h, 99%; k) I , CHCl , RT, 15 h, 90%; l) arylboronic acid,
Na CO , Pd(OAc) , PEG 10000, MeOH, 508C, 4 h; m) benzaldehyde, NaH, THF, RT, 2 h; n) 25% aq NaOH, 30% aq H , THF/MeOH (3:5), 08C–RT, 48 h; o) reac-
tive methylene compound, piperidine, EtOH, 808C, 4 h; p) DMSO, NaH, PhMe, 808C, 2 h, 95%; q) benzaldehyde, piperidine, PhMe, 1208C, 3 h; r) MeOH (satu-
rated with NH ), 658C, 24 h, 100%; s) benzaldehyde, piperidine, PhMe, 1208C, 12 h. DEG=diethylene glycol; DDQ=2,3-dichloro-5,6-dicyano-1,4-benzoqui-
2
2
0
2
3
2
3
2
2 2
O
3
none; DMF-DMA=N,N-dimethylformamide dimethyl acetal; DME=glycol dimethyl ether; DMF=N,N-dimethylformamide; PEG=polyethylene glycol; THF=te-
trahydrofuran; DMSO=dimethylsulfoxide.
factor in the activity of these molecules, and we expect to find
chemical elicitors by synthesizing NP-like libraries containing
versatile key substrate that can be transformed into the target
compounds.
[13]
the 3-methylfuran moiety. Furthermore, coumarin,
chal-
The compound 3 was prepared in three steps directly from
commercially available cyclohexane-1,3-diketone and ethyl 2-
chloroacetoacetate. This process involved the cycloaddition of
cyclohexane-1,3-diketones with ethyl 2-chloroacetoacetate, fol-
lowed by the base-catalyzed dehydration to give the 3-methyl-
[
14]
[15]
[16]
[17]
cone,
flavone,
flavonol,
isoflavone
and isoquinoli-
[
18]
none are six naturally occurring compounds that have exhib-
ited a variety of biological activities. Inspired by these NPs and
their inherent biological activities, we designed a divergent
synthetic pathway to synthesize 88 NP-like compounds based
on a key 3-methylfuran core obtained from available starting
[21]
tetrahydrobenzofuran 1 in 65% yield. This method was effi-
cient and gave the product 1 on a 20 g scale. Ester 1 was hy-
drolyzed to afford 2 in 90% yield by treatment with KOH in
aqueous ethanol at RT. Treatment of 2 with Cu powder in di-
ethylene glycol containing pyridine was heated at 170–1758C
[
13b,19]
material cyclohexane-1,3-diketone (Scheme 1).
These
compounds have been applied in a phenotypic high-through-
[
20]
put screening of b-glucuronidase (GUS) and several new hits
have been discovered. As chemical elicitors, these hits can
induce resistance in rice to nymphs of the brown planthopper
[21a]
for 10 h to give the product 3 in 85%.
After being acidified
to pH<1, the excess of pyridine was removed, and the pure 3
could be easily obtained.
(BPH) Nilaparvata lugens, one of the most important rice insect
pests in Asia.
Three key intermediates 7, 8, 9 were prepared from cyclo-
hexenone 3 using 2,3-dichloro-5,6-dicyano-l,4-benzoquinone
(
(
DDQ)-catalyzed dehydrogenation–aromatization reactions
2
. Results and Discussion
[19c,e]
Scheme 1).
This transformation was a key step, because it
A divergent synthetic pathway to NP-like libraries containing
a 3-methylfuran moiety is illustrated in Scheme 1. Our diver-
gent synthetic pathway was achieved by identifying 3 as the
is difficult to obtain the pure products 7, 8 and 9 by a classical
[19d,22]
electrophilic aromatic substitution reaction of phenol.
No-
tably, the metal-free oxidative aromatization of substituted cy-
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clohexenones is an effective route to obtain ortho-substituted
phenols with high regioselectivity. For example, 3 was formy-
lated using an excess of NaH in the presence of ethyl formate
in toluene to give 4 followed by the dehydrogenation–aroma-
[
a]
Table 2. Structures and yields of angular 3-methylfuranochalcones deriva-
tives. The X-ray crystal structure of 11 s is also shown.
[
19c]
tization reaction to 7 in an overall 75% yield.
The pure com-
pound 7 was obtained by using column chromatography.
Compounds 8 and 9 were also obtained under similar condi-
[
23]
1
tions. In a H NMR spectroscopic examination of 7, 8 and 9,
the proton of OH in phenol displayed a typical chemical shift
of 9.4 ppm due to the deshielding effect of the hydrogen
bond with the neighboring C-12 carbonyl oxygen atom.
Product
1 a
B
C
Yield [%]
Product
B
Yield [%]
1
6
H
5
82
85
87
84
88
85
74
81
76
86
73
88
81
73
11 o
11 p
11 q
11 r
11 s
11 t
11 u
11 v
11 w
11 x
11 y
11 z
11 aa
11 ab
2-ClC
2-BrC
2-MeOC H
6
H
4
83
81
86
85
86
87
80
82
81
80
84
86
77
1
1 b
11 c
1 d
1 e
1 f
1 g
11 h
1 i
1 j
1 k
4-MeC
4-iPrC H
4-tBuC
4-MeOC
4-EtOC
4-FC
4-ClC
4-BrC
4-(Me)
4-CNC
4-(Et) NC H
6
H
4
6 4
H
6
4
6
4
1
6
H
4
2,4-di-MeC
2,4,6-tri-MeC
3,4,5-tri-MeOC
2,4-di-ClC
2-Br-4-FC
3-ClC
3-BrC
3-MeC
6 3
H
1
6
H
4
6 2
H
1
6
H
4
6 2
H
2.1. Synthesis of Angular 3-Methylfuranocoumarins (10)
1
6
H
4
6 3
H
For the synthesis of 3-methylfuranocoumarins 10a, we first
used l-proline as the promoter to test the reaction between al-
dehyde 7 and ethyl acetoacetate, according the procedure re-
6
H
4
6 3
H
1
6
H
4
6 4
H
1
2
NC
6
H
4
6
H
4
1
6
H
4
6
H
4
[
24]
ported by Kurt and co-workers.
Surprisingly, the reaction
11 l
11 m
6 4
3-MeOC H
2
6
4
failed, probably due to the presence of an acidic hydroxy
group in the phenol. After several trials, the use of piperidi-
4-NO
2-FC
2
C
6
H
4
2-furaldehyde
2-thenaldehyde 79
11 n
6
H
4
[
13a,25]
ne
as a promoter in ethanol under reflux conditions gave
[a] Yield of isolated product.
the products 10a in 90% yield (Table 1). Furthermore, the gen-
eral scope of this reaction was tested with different active
methylene compounds, and the desired products 10b–10h
were directly precipitated from solution under identical reac-
tion conditions in good yields (Table 1). This methodology is
efficient, operationally simple and environmentally friendly.
screening of other bases afforded a very good yield (82%) of
11 a, and NaH was proved to be optimal for this transforma-
[26]
tion. Furthermore, a series of substituted aldehydes (1 equiv)
were allowed to undergo Claisen–Schmidt condensation with
8
(1 equiv) in the presence of NaH (2 equiv) in anhydrous THF
at room temperature (Table 2). The products 11 were readily
obtained by recrystallization from ethanol after acidifying the
solution to pH 1. Reactions involving electron-withdrawing and
electron-donating substituents on benzene rings all proceeded
well to afford good to very good yields of 11 (Table 2). Finally,
we attempted to determine the E,Z configurations of 11. The
trans (E) configuration of 11 was confirmed by the use of X-ray
structure analysis of a single crystal of 11 s obtained by recrys-
[
a,b]
Table 1. Structures and yields
rivatives.
of angular 3-methylfuranocoumarins de-
[43]
tallization from ethanol.
2.3. Synthesis of Angular 3-Methylfuranoflavonols (12)
From a survey of the literature, we found that flavonol deriva-
tives can be achieved by the epoxidation of corresponding fla-
[27]
vone compounds or by the Baker–Venkataraman type of se-
[28]
[a] All reactions were performed in ethanol at reflux. [b] Yield of isolated
quential cyclization-dehydration reaction.
Another Algar–
product.
Flynn–Oyamada reaction has also been widely used to make
[16,28b]
flavonols.
-methylfuranochalcones 11 to angular 3-methylfuranoflavo-
nols 12 in the presence of NaOH (2 equiv) and H O
We chose this reaction for the transformation of
3
2
2
2
.2. Synthesis of Angular 3-Methylfuranochalcones (11)
(
2.2 equiv). In this procedure, the use of THF and methanol as
The synthesis of angular 3-methylfuranochalcones 11 was ac-
complished from commercially available starting materials in
the presence of bases through Claisen–Schmidt condensation
co-solvents instead of methanol alone gave the best results,
because of the poor solubility of these corresponding chal-
cones 11 in methanol (Table 3). The electron-donating substitu-
[
14]
[22a]
(Table 2). First, we investigated the effect of bases on the re-
ents on benzene rings were compatible.
The product was
actions of 8 with benzaldehyde. It was found that 5 equiva-
lents of NaOH can hardly catalyze the reaction (yield <5%).
KOH gave 57% yield of the desired product 11 a. Further
purified by recrystallization from ethanol to afford the desired
products 12. Single crystals of 12c were obtained by recrystal-
lization from petroleum ether/CH Cl , and the configurations of
2
2
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[
a]
[a]
Table 3. Structures and yields of angular 3-methylfuranoflavonol deriva-
tives. The X-ray crystal structure of 12c is also shown.
Table 4. Structures and yields of angular 3-methylfuranoflavone deriva-
tives. The X-ray crystal structure of 14h is also shown.
[a] Yields of isolated products.
the products were unambiguously determined by X-ray
[
43]
analysis.
2.4. Synthesis of Angular 3-Methylfuranoflavones (14)
Many molecules of biological importance contain a 4-pyrone
[
19e]
moiety,
and various methods are available for constructing
this unit. These transformations have involved the Baker–Ven-
[
29]
[30]
[a] Yields of isolated products.
kataraman rearrangement,
Allan–Robinson reaction,
and
We
[22a]
the intramolecular cyclization of 2-hydroxychalcones.
tried to use the Von Strandtmann approach for constructing 4-
[
22b,31]
pyrone rings.
The 3-methylbenzofuran 9 was treated with
a methanol solution saturated with ammonia in a Fisher–
Porter bottle with 100% conversion. Excess ammonia was re-
moved under vacuum at 408C. The resulting intermediate 15
was allowed to undergo cyclization with a series of substituted
aldehydes using piperidine as a catalyst at 1108C to afford the
the dimsyl anion in DMSO to form the b-ketosulfoxide 13,
which after treatment with benzaldehyde derivatives and pi-
peridine in anhydrous toluene, first at 408C and then at 1108C,
produced the corresponding 3-methylfuranoflavones 14
[18,32]
(
Table 4). After removal of the solvent under reduced pressure,
products 16.
The crude products were readily purified by
the residue was added to EtOH and stirred. The resulting pre-
cipitate was filtered, then recrystallized from EtOH to readily
afford products 14. With the use of 13 as a highly activated
methylene compound, both electron-withdrawing and elec-
tron-donating substituents were introduced into the aryl alde-
hyde to study the effects of the electronic and steric properties
on reactivity. We found that all the reactions proceeded well to
afford the 3-methylfuranoflavones 14 in good yields ranging
from 80% to 95% (Table 4). The identity of product 14h was
column chromatography in moderate to good yields (60–80%)
(Table 5). The structure of 3-methylfuranoisoquinolinone 16a
[43]
was determined by X-ray analysis.
2.6. Synthesis of Angular 3-Methylfuranoisoflavones (19)
Finally, the synthesis of 3-methylfuranoisoflavones 19 was ac-
complished by the introduction of the key intermediate 18 in
two steps. The first step was to treat intermediate 8 with N,N-
dimethylformamide dimethyl acetal (DMF-DMA) to form the
corresponding enamine 17. In the second step, this crude
product 17 was filtered and directly cyclized to 3-iodochro-
[
43]
unambiguously determined by X-ray analysis.
2.5. Synthesis of Angular 3-Methylfuranoisoquinolinones
[17,33]
mone 18 using iodine in CHCl3
without further purification
(16)
(
Scheme 1). We were satisfied with the cross-coupling of 3-io-
For the synthesis of 3-methylfuranoisoquinolinones 16, we first
synthesized amide intermediate 15 by treating ester 9 with
dochromone 18 with 2 equivalents of substituted phenylbor-
onic acids using polyethylene glycol 10000 (PEG 100000) as
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chemical space occupied by top-selling drugs considerably
and overlapped with the space of coumarins and flavonoid
natural products. This indicated the potential drug-like proper-
ties of our library and possibly implied that these compounds
overlapped with biologically relevant areas of the chemical
space. Examination of the component loadings (Table S5) indi-
cated that the major contributions of principal component one
[
a]
Table 5. Structures and yields of angular 3-methylfuranoisoquinolinone
derivatives. The X-ray crystal structure of 16a is also shown.
(
PC1) are the number of all atoms, molecular surface areas and
solvent-accessible surface areas. The lipophilicity (logP), topo-
logical polarity surface area and relative hydrophobic surface
area are the key factors associated with principal component
two (PC2). The principal component three (PC3) is greatly influ-
enced by relative negatively and positively charge surface
areas. It is worth noting that in Figure 2B and C, our library is
even more distinct from the range of drug structures com-
pared with the analysis in Figure 2A. These suggest that the
relative negatively and positively charged surface areas are
two important properties that differentiate our libraries from
the drug library in Figure 2B and C. The understanding of such
analyses might be advantageous for further structural optimi-
zation and provides some insight into the planning of future
libraries.
[
a] Yields of isolated products.
[
a]
Table 6. Structures and yields of 3-methylfuranoisoflavone derivatives.
2.8. Screening of Candidate Elicitors from Synthesized
Compounds
[39]
To discover new candidate elicitors, we used a high-through-
put screening system that we had previously established to
evaluate these synthesized chemicals for their potential to
[a] Yields of isolated products.
[20,40]
induce GUS activity.
Table S2 summarizes the relative in-
duction of GUS activity (comparing GUS activities in roots of
plants that were grown in nutrient solution with that of com-
À1
a ligand in the presence of Pd(OAc) and Na CO in MeOH to
pounds tested at a concentration of 5 mgL versus GUS activ-
2
2
3
obtain 3-methylfuranoisoflavones 19 in generally moderate to
high yields (Table 6).
ities in roots of control plants) in rice plants after these were
treated with each chemical. The higher the value, the higher
the potential of the compound to induce GUS activity; also,
the compound used might have high potential to elicit plant
defenses. To our delight, 23 compounds were found to induce
an increase in GUS activity (Table S2). Notably, compounds 3
(1.68**), 11 h (1.53**), 11 a (1.55**), 11 d (1.83**) 11 r (2.11**),
11 y (1.80**) and 11 k (1.51**) exhibited strong potential for
the ability to induce GUS activity. Moreover, most of the 3-
methylfuranochalcones demonstrated moderate to good po-
tential to induce GUS activity, and 3-methylfuranochalcones
derivatives showed the most potent activities of these com-
pounds. Thus, 3-methylfuranochalcones derivatives might be
used as potential lead compounds to develop novel chemical
elicitors.
[
16,34]
2.7. Chemoinformatic Analysis
To computationally assess the structural diversity of our 3-
methylfuran library, the structural features were analyzed in
terms of their chemical properties by using principal compo-
[35]
nent analysis (PCA).
PCA computes the position of each
compound in a two- or three-dimensional coordinate system
based on a set of molecular properties, such as physicochemi-
cal properties, to simplify the comparison with different sets of
[
8a,b,36]
compounds.
Using PCA, the chemical properties of our 3-
methylfuran library were compared with reference sets of
[
8b,37]
40 top-selling brand name drugs used by Tan
(Table S6)
and 20 coumarin and flavonoid natural products (Table S7).
Twenty physicochemical properties (Table S3) of these com-
2.9. Effects of Candidate Elicitors on the Survival Rates of
[38]
pounds were analyzed using a public, web-based tool. These
properties represent each compound as a vector in 20-dimen-
sional space. The 20-dimensional vector can be reduced to
two-dimensional vectors by an orthogonal transformation and
plotted as a scatter plot (Figure 2A–C and Table S5). The first
three principal components captured 80.7% of the dataset var-
iance (Table S4). As seen in Figure 3a, our library accesses the
the BPH
To investigate whether the candidate elicitors can provoke
plant defenses and thus influence herbivore behavior, we
chose the most promising compounds, including 3-methylfura-
nochalcones (11 d, 11 h, 11 k, 11 r, and 11 y), a 3-methylfurano-
flavonol (12g) and a 3-methylfuranoflavone (14u), to evaluate
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Figure 2. Comparative PCA plots. Ninety-nine DOS library compounds (green), 40 top-selling brand-name drugs (red) and 20 coumarins and flavonoid natural
products (blue) were used; a) PC1 versus PC2; b) PC1 versus PC3; c) PC2 versus PC3.
their effects on the survival rate of BPH nymphs. Results
showed that compared to those feeding on control plants, the
survival rates of BPH nymphs were significantly lower on
plants whose roots had been treated with 3-methylfuranochal-
cones compounds—such treatment caused 40–50% mortality
rate of BPH nymphs at 10–14 days after the release of the her-
bivore (Figure 3A–E), whereas the survival rates on plants
treated with compound 12g or 14u were only slightly lower
than those on control plants (Figure 3F and G). Moreover, the
tested compounds themselves did not result in the death of
the herbivore: the survival rates of BPH nymphs that fed on an
artificial diet containing the test compounds did not differ
from those of nymphs that fed on the artificial diet only (Fig-
ure S1); similarly, the survival rates of BPH nymphs that were
sprayed with one of these chemicals had no difference with
those of the control groups (Figure S2). In addition, the survival
rates of BPH nymphs on plants treated with 3-methylfurano-
chalcone compounds decreased continuously until 10–11 days
after herbivore release, when the nymphs were in their third
and fourth instars (Figure 3). These data suggest that the re-
sistance of the candidate elicitor-treated rice plant to the her-
bivore derives from the defense responses induced in the
plant by these chemicals, not from the chemicals themselves,
and that the elicited resistance is also effective against third–
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À1
Figure 3. Mean survival rate of N. lugens nymphs (+SE, n=6) on plants, that had been treated with one of the compounds, at a concentration of 20 mgL
4 h before exposure versus control plants (C), 1–14 d after exposure. Asterisks indicate significant differences between treatments and controls at each time
2
point (*P<0.05, **P<0.01, Student’s t-tests).
fourth instar BPH nymphs. Therefore, 3-methylfuranochalcones
can be used as possible lead compounds to develop chemical
elicitors as safe plant protection agents.
skeletal diversity. A collection of 88 NP-like small molecules
with 3-methylfuran cores was synthesized. Principal compo-
nent analysis (PCA) was used to assess the structural diversity
of our DOS library, and showed our molecules overlapping
with drug and NP chemical spaces, indicating the drug- and
NP-like structures of our libraries. Phenotypic high-throughput
screening for GUS activity uncovered several hits. Further
in vivo screenings confirmed that these elicitors can induce re-
3
. Conclusions
We describe a divergent synthetic strategy for discovering
chemical elicitors. The aim of DOS is to achieve high levels of
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sistance to N. lugens in rice. The present work demonstrates
that 3-methylfuranochalcones can be used as potential lead
compounds for developing chemical elicitors. Moreover, the
discovery of new chemical elicitors serves to endorse DOS as
an approach to discover new classes of biological small
molecules.
mixture was heated slowly to reflux over 30 min and then heated
at reflux for 3 h. After the mixture had cooled, water (40 mL) and
saturated NH Cl solution (120 mL) were added dropwise, and the
4
aqueous layer was extracted with ethyl acetate (3ꢁ80 mL). The
combined organic layers were washed with brine, dried over
Na SO , and evaporation of the solvent gave crude product 5.
2
4
Without further purification, 5 in anhydrous toluene (60 mL) was
treated with DDQ (3.06 g, 13.5 mmol), and the mixture was heated
at reflux for 6 h. The reaction mixture was allowed to cool to RT
then filtered. The solids were washed with toluene and the filtrate
was evaporated in vacuo. Purification by column chromatography
gave the corresponding product 8 (1.87 g, 70%, 2 steps). The
target compound 9 was prepared by following the same proce-
dure as for 8. Reaction of tetrahydrobenzofuran 3 (2.1 g, 14 mmol)
with dimethyl carbonate (6.3 g, 70 mmol) in DME (150 mL) afforded
Experimental Section
Chemical Synthesis
General Procedure for the Synthesis of Compounds 3
1
,3-Cyclohexanedione (20 g, 0.178 mol) was added to a solution of
KOH (10 g, 0.178 mol) in water (240 mL). After 5 min, ethyl 2-chlor-
oacetoacetate (29.35 g, 0.178 mol) in MeOH (60 mL) was added.
The mixture was stirred at room temperature for 5 days. After
acidification with HCl (4n, 300 mL), the solution was extracted
with ethyl acetate (3ꢁ250 mL). The combined extracts were
washed with brine (300 mL) and dried (Na SO ), and the solvent
6
as a white solid. Product 6 (2.0 g) was treated with DDQ in anhy-
drous toluene (60 mL) to give compound 9 (2.16 g, 75%, 2 steps).
2
4
General Procedure for the Synthesis of Angular 3-Methyl-
furanocoumarins (10)
was evaporated under vacuum to give the furan ester 1 (25.7 g,
5%). Without further purification, compound 1 (20 g, 0.09 mol)
6
A solution of 7 (200 mg, 1.12 mmol), ethyl acetoacetate (146 mg,
was dissolved in MeOH (84 mL) and water (32 mL) and treated
with KOH (35.4 g, 0.56 mol). After stirring overnight at RT, the reac-
tion mixture was diluted with water (160 mL), acidified with HCl
1
.12 mmol) and piperidine in anhydrous EtOH (10 mL) was heated
at reflux for 4 h. The product precipitated quantitatively from the
solution as it was formed. The precipitate was filtered and washed
with ethanol to afford pure 10a as a white solid in 90% yield. The
target compounds 10b–10h were prepared by following the same
procedure as for 10a.
(
6n), and extracted with ethyl acetate (3ꢁ250 mL). The extract was
washed with brine (250 mL), dried (Na SO ), and the solvent was
2
4
evaporated under vacuum to give the furan acid 2 (15.73 g, 90%).
Without further purification, the 2 (10 g, 0.052 mol) in diethylene
glycol (80 mL) was treated with Cu powder (3.27 g, 0.052 mol) and
anhydrous pyridine (8.23 g, 0.104 mol) and heated at 170–1758C
for 10 h. The mixture was cooled to room temperature, diluted
with ice water (150 mL), acidified with HCl, (4n, 100 mL), and ex-
tracted with ether (3ꢁ100 mL). The combined ether extracts were
General Procedure for the Synthesis of Angular 3-Methyl-
furanochalcones (11)
washed with water (100 mL) and saturated aqueous NaHCO solu-
3
NaH (2 mmol, 60% dispersion in mineral oil) was added in portions
tion (150 mL), dried (Na SO ), and evaporated to give pale yellow
2
4
to a solution of 8 (1 mmol) in anhydrous THF (5 mL), under N and
2
crystals of 3 (6.6 g, 85%).
with vigorous stirring. After stirring for 15 min, a solution of the
corresponding benzaldehyde (1 mmol) in anhydrous THF (3 mL)
was added dropwise over 5 min, and the reaction mixture was
stirred at RT for 2 h. Water (10 mL) was added to quench the reac-
tion. The pH of the mixture was adjusted to 1 by adding 2n HCl.
The product was precipitated as a colorful solid in aqueous solu-
tion. After filtration, the crude product was recrystallized from
EtOH to afford the pure product as a colorful solid. Using this pro-
cedure, the target compounds 11 b–11 ab were obtained. An addi-
tional amount of product could be obtained from the mother liq-
uors. To this end, the solvent was evaporated in vacuo, and the res-
idue was purified by column chromatography.
General Procedure for the Synthesis of Compounds 7–9
NaH (2.47 g, 61.7 mmol, 60% dispersion in mineral oil) was added
to a solution of 3 (2.1 g, 14 mmol) in anhydrous toluene (150 mL)
at 08C, and the mixture was stirred for 30 min. A solution of ethyl
formate (3.42 g, 46.2 mmol) in anhydrous toluene (20 mL) was
added to the reaction mixture over a period of 30 min at 08C. The
mixture was stirred at 08C for 1 h, allowed to warm to RT then
stirred for 8 h. Water (100 mL) was added to the mixture at 08C
and acidified by HCl (2n). The organic layer was separated, and
the aqueous layer was extracted with diethyl ether (3ꢁ80 mL). The
combined organic extracts were washed with brine and dried over
anhydrous Na SO . Evaporation of the solvent gave crude product
2
4
General Procedure for the Synthesis of Angular 3-Methyl-
furanoflavonols (12)
4. Without further purification, 4 (2.0 g) in anhydrous toluene
(
20 mL) was treated with DDQ (3.06 g, 13.5 mmol), and the mixture
was heated at reflux for 6 h. The reaction mixture was allowed to
cool to RT and filtered. The solids were washed with toluene and
the filtrate was evaporated in vacuo. The residue was purified by
column chromatography to give the corresponding product 7. A
solution of 3 (2.1 g, 14 mmol) in anhydrous DME (20 mL) at 08C
was added to a stirred solution of NaH (2.8 g, 70 mmol, 60% dis-
30% aqueous H O (2.2 mmol) was added dropwise to a stirred so-
2
2
lution of the corresponding angular 3-methylfuranochalcones
(1 mmol) in THF (3 mL), methanol (5 mL), and 25% aqueous NaOH
solution (2 mmol) at 08C was added dropwise. The solution was
sealed and stirred at 08C for 1 h, then stirred at RT for 48 h. The
product precipitated from the solution as it was formed. After
acidification with HCl (2m), the resulting flavonols were filtered
from aqueous solution. The crude product was recrystallized from
EtOH to afford the pure product as a colorful solid. The target
compounds 12a–12j were obtained using this procedure.
persion in mineral oil) in anhydrous DME (100 mL) under N was
2
added and the mixture was stirred at 08C for 30 min. A solution of
ethyl acetate (3.69 g, 42 mmol) in anhydrous DME (20 mL) was
added to the reaction mixture over a period of 30 min at 08C. The
&
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General Procedure for the Synthesis of Angular 3-Methyl-
furanoflavones (14)
afford the product 19. The target compounds 19a–19e were ob-
tained using this procedure.
A mixture of anhydrous DMSO (5.2 mL) and NaH (36.4 mmol, 60%
dispersion in mineral oil) in anhydrous toluene (60 mL) was heated
at 808C under N2 for 2 h. The solution was cooled to 408C, and
a solution of 9 (7.2 mmol) in anhydrous toluene (8 mL) was added
dropwise to the stirred solution. The reaction mixture was then
stirred at 408C for 1 h, diluted with diethyl ether (75 mL), and
Principal Component Analysis
PCA was performed using the SPSS 20 software package. A total of
2
0 physicochemical properties (Table S3) were obtained for estab-
lished reference sets of 40 top-selling brand-name drugs (Table S6)
and 20 coumarins and flavonoid natural products (Table S7). The
summary of the contribution of each principal component is
shown in Table S4, and the component loadings are shown in
Table S5. The first three principal components account for 80.7%
of the variance in the dataset and were used to generate Figure 2.
quenched with a saturated solution of NH Cl (60 mL). The organic
4
layer was separated, and the aqueous layer was extracted with di-
ethyl ether (30 mLꢁ3). The combined organic layer was washed
with brine, dried over Na SO and concentrated in vacuo. The re-
2
4
sulting residue was purified by column chromatography to afford
3 (95%) as a yellow solid. A solution of substituted benzaldehyde
4.2 mmol) in anhydrous toluene was added dropwise to a warm
1
(
Quantitative b-Glucuronidase Activity Assay
solution (408C) of 13 (0.42 mmol) in anhydrous toluene (15 mL)
containing a catalytic amount of piperidine (4 drops). The resulting
mixture was heated at reflux for 3 h. After removal of the solvent
under reduced pressure, EtOH (10 mL) was added to the residue
and stirred to achieve precipitation. The resulting precipitate was
filtered, then washed with EtOH to afford the pure product as a col-
orful solid. The products 14a–14ab were obtained in this way,
which were of sufficient purity for most purposes.
The rice genotypes used in this study were transgenic lines of L15–
[20]
3
8. Pre-germinated seeds of the different lines were cultured in
plastic bottles (diameter 8 cm, height 10 cm) in a greenhouse
288C, 14 h light, 10 h dark). Ten-day-old seedlings were transferred
(
[41]
to 20 L hydroponic boxes with a rice nutrient solution. After 25–
30 days, plants were transferred to individual 500 mL hydroponic
plastic pots. Four to five days later, individual rice plants were ran-
domly divided into two groups: chemical treatment and control. For
chemical treatment, individual plants were grown in the nutrient so-
lution that contained one of the tested compounds at the concen-
General Procedure for the Synthesis of Angular 3-Methyl-
furanoisoquinolinones (16)
À1
tration of 5 mgL . Non-manipulated plants grown in the nutrient
solution without tested compounds were used as controls. GUS ac-
tivities in transgenic plants were analyzed according to the method
A solution of 9 (3 mmol) in methanol (15 mL) was saturated with
ammonia and heated to 658C for 24 h in a Fisher–Porter bottle.
The excess of methanol and ammonia was removed under vacuum
at 408C to provide pure intermediate 15. To a solution of 15
[40]
described by He et al. Each treatment at each time interval was re-
plicated six times. The relative GUS activity for one chemical is equal
À1
to the GUS activity induced by the tested compound (5 mgL ) di-
(
0.42 mmol) and substituted benzaldehyde (1.26 mmol) in anhy-
vided by that induced by the control 48 h after treatment.
drous toluene (20 mL), a catalytic amount of piperidine was added.
The resulting mixture was heated at reflux for 12 h. After removal
of the solvent under reduced pressure, the residue was purified by
column chromatography to afford the product 16 as a white solid.
The target compounds 16a–16i were obtained using this procedure.
Herbivore Bioassay
Plant Growth
The rice genotypes used in this study were cultivar Xiushui 110.
The method for plant growth was the same as stated above.
General Procedure for the Synthesis of Angular 3-Methyl-
furanoisoflavones (19)
Insects
A solution of 8 (1 mmol) and N,N-dimethylformamide dimethyl
acetal (3.5 mmol) in DMF (10 mmol) was heated to 70–758C for
Colonies of BPH were originally obtained from rice fields in Hang-
zhou, China, and maintained on TN1 seedlings in a controlled cli-
mate chamber at 26Æ28C, with a 12/12 h (light/dark) photoperiod
and 80% relative humidity.
4
h. Saturated brine (20 mL) was added to the cooled reaction mix-
ture, and a green product precipitated from the solution. The reac-
tion mixture was filtered, and a green precipitate of 17 (99%) was
obtained. I (3 mmol, 3 equiv) was added to a solution of 17 in
2
CHCl (15 mL), and the mixture was stirred at room temperature
3
for 12 h. The reaction was quenched by adding 5% aqueous
Survival Rate of N. lugens Nymphs Feeding on Elicitor-Treated
Plants
NaHSO (10 mL), and the aqueous layer was extracted with CHCl3
3
(
3ꢁ10 mL). The combined organic layers were washed with 5%
aqueous NaHCO , then dried over Na SO . Evaporation of the sol-
vent gave a residue, which was purified by column chromatogra-
Individual rice seedlings were grown in nutrient solution that con-
tained one of the tested compounds (each compound was first dis-
solved in a small quantity of DMSO) at a concentration of 20 mgL
3
2
4
À1
phy to afford the product 18 (90%). A mixture of Na CO (0.212 g,
2
3
2
mmol), Pd(OAc) (2 mg, 1 mol%), PEG 10000 (3.5 g), and metha-
24 h before insects were introduced. Non-manipulated plants grown
in the same nutrient solution with a small quantity of DMSO but
without compounds were used as controls. The basal stem of each
plant was confined within a glass cylinder (diameter 4 cm, height
8 cm, with 48 small holes, diameter 0.8 mm), into which 11 newly
hatched BPH nymphs were introduced. The numbers of surviving
BPH nymphs each day on each plant were recorded until they
emerged as adults. The experiment was replicated six times.
2
nol (3 mL) was heated to 508C with stirring. Then, 18 (1 mmol) and
an arylboronic acid (1.5 mmol) were added to the solution and the
mixture was stirred at 508C for 4 h. After being cooled to room
temperature, the reaction mixture was diluted with H O (30 mL)
and extracted with diethyl ether (4ꢁ15 mL). The collected organic
extracts were dried (Na SO ) and concentrated under reduced pres-
2
2
4
sure. The residue was purified by column chromatography to
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Direct Effects of Chemical Elicitors on N. lugens Nymphs
[15] M. Khanapur, N. K. Pinna, J. Badiger, Med. Chem. Res. 2015, 24, 2656–
669.
[16] Z. Li, G. Ngojeh, P. DeWitt, Z. Zheng, M. Chen, B. Lainhart, V. Li, P. Felpo,
Tetrahedron Lett. 2008, 49, 7243–7245.
2
[
42]
Survival rates of newly-hatched BPH nymphs on an artificial diet
containing one of these chemicals at a concentration of 20 mgL
À1
were determined using 30 mL glass cylinders, each side containing
diet covered with a thin layer of parafilm into which 11 BPH
nymphs were introduced and allowed to feed for 6 days. The
number of BPH nymphs alive in each glass cylinder was recorded
every day. The experiment was replicated six times. To further deter-
mine if these candidate elicitors have toxicity upon direct contact
with insects, newly hatched BPH nymphs were put in Petri dishes
lined with filter papers and sprayed with one of these elicitors in so-
[17] D. A. Vasselin, A. D. Westwell, C. S. Matthews, T. D. Bradshaw, M. F. Ste-
vens, J. Med. Chem. 2006, 49, 3973–3981.
[
18] L.-J. Cui, J. Guo, G.-H. Gong, Z.-S. Quan, Asian J. Chem. 2014, 26, 2553–
556.
2
[
19] a) H. Valizadeh, A. Shockravi, J. Heterocycl. Chem. 2006, 43, 763–765;
b) T. Kitamura, K. Otsubo, J. Org. Chem. 2012, 77, 2978–2982; c) Y. R.
Lee, Tetrahedron 1995, 51, 3087–3094; d) M. Dixit, B. K. Tripathi, A. K.
Tamrakar, A. K. Srivastava, B. Kumar, A. Goel, Bioorg. Med. Chem. 2007,
15, 727–734; e) Y. R. Lee, A. T. Morehead, Jr., Tetrahedron 1995, 51,
4909–4922.
À1
lution (20 mgL ). The control group of BPH nymphs was sprayed
with water only. As soon as the insects were dry, they were all trans-
ferred onto rice seedlings, each containing 11 nymphs. The number
of BPH nymphs that were alive on each plant was recorded every
day. The experiment was replicated six times.
[20] Z. Xin, Z. Yu, M. Erb, T. C. Turlings, B. Wang, J. Qi, S. Liu, Y. Lou, New
Phytol. 2012, 194, 498–510.
[
21] a) A. Gopalan, P. Magnus, J. Org. Chem. 1984, 49, 2317–2321; b) H. Stet-
ter, R. Lauterbach, Angew. Chem. 1959, 71, 673–673.
[
22] a) S. R. Satyavani, S. Kanjilal, M. S. Rao, R. B. N. Prasad, U. S. N. Murthy,
Med. Chem. Res. 2015, 24, 842–850; b) Y. R. Lee, D. H. Kim, Synthesis
2
006, 603–608; c) Y. Izawa, D. Pun, S. S. Stahl, Science 2011, 333, 209–
Acknowledgements
213.
[
[
23] Y. R. Lee, A. T. Morehead, Cheminform 1995, 26, DOI: 10.1002/
chin.199535304.
24] B. Z. Kurt, I. Gazioglu, F. Sonmez, M. Kucukislamoglu, Bioorg. Chem.
The study was jointly sponsored by the Special Fund for Agro-sci-
entific Research in the Public Interest (201403030), the National
Natural Science Foundation of China (No.31471807), the Special
Fund for Agro-scientific Research in the Public Interest of Zhe-
jiang (2014C22004).
2
015, 59, 80–90.
[
[
25] J. Li, X. Li, S. Wang, Chin. J. Struct.Chem. 2012, 7, 1003–1007.
26] G. Sagrera, A. Bertucci, A. Vazquez, G. Seoane, Bioorg. Med. Chem. 2011,
19, 3060–3073.
[
27] S. Li, M.-H. Pan, C.-S. Lai, C.-Y. Lo, S. Dushenkov, C.-T. Ho, Bioorg. Med.
Chem. 2007, 15, 3381–3389.
Keywords: 3-methylbenzofurans
activity · chemical elicitors · diversity-oriented synthesis · insect
pests
·
beta-glucuronidase
[28] a) K.-i. Oyama, S. Kawaguchi, K. Yoshida, T. Kondo, Tetrahedron Lett.
007, 48, 6005–6009; b) C. J. Bennett, S. T. Caldwell, D. B. McPhail, P. C.
Morrice, G. G. Duthie, R. C. Hartley, Bioorg. Med. Chem. 2004, 12, 2079–
098.
2
2
[
[
[
29] W. Baker, J. Chem. Soc. 1933, 1381–1389.
[
1] a) F. P. Silverman, P. D. Petracek, D. F. Heiman, C. M. Fledderman, P. Warri-
or, J. Agric. Food Chem. 2005, 53, 9775–9780; b) L. Sticher, B. Mauch-
Mani, J. P. Mꢂtraux, Annu. Rev. Phytopathol. 1997, 35, 235–270.
2] Y. R. Cohen, Plant Dis. 2002, 86, 448–457.
30] J. Allan, R. Robinson, J. Chem. Soc. Trans. 1924, 125, 2192–2195.
31] M. Von Strandtmann, S. Klutchko, M. P. Cohen, J. Shavel, J. Heterocycl.
Chem. 1972, 9, 171–172.
[
[
[
32] R. B. Gammill, J. Org. Chem. 1981, 46, 3340–3342.
3] I. S. Sobhy, M. Erb, Y. Lou, T. C. Turlings, Philos. Trans. R. Soc. London Ser.
B 2014, 369, 20120283.
[
33] a) R. Gammill, Synthesis 1979, 901–903; b) G. Li, Z. T. Zhang, L. Y. Dai,
Y. L. Du, D. Xue, Helv. Chim. Acta 2012, 95, 989–997.
34] L. Liu, Y. Zhang, Y. Wang, J. Org. Chem. 2005, 70, 6122–6125.
[4] a) H. Lachance, S. Wetzel, K. Kumar, H. Waldmann, J. Med. Chem. 2012,
[
[
[
55, 5989–6001; b) C. Cordier, D. Morton, S. Murrison, A. Nelson, C.
35] C. M. Dobson, Nature 2004, 432, 824–828.
O’Leary-Steele, Nat. Prod. Rep. 2008, 25, 719–737.
36] B. M. Ibbeson, L. Laraia, E. Alza, O. C. CJ, Y. S. Tan, H. M. Davies, G.
McKenzie, A. R. Venkitaraman, D. R. Spring, Nat. Commun. 2014, 5, 3155.
37] R. A. Bauer, J. M. Wurst, D. S. Tan, Curr. Opin. Chem. Biol. 2010, 14, 308–
[5] a) D. Camp, R. A. Davis, M. Campitelli, J. Ebdon, R. J. Quinn, J. Nat. Prod.
2012, 75, 72–81; b) J. Larsson, J. Gottfries, S. Muresan, A. Backlund, J.
[
[
Nat. Prod. 2007, 70, 789–794; c) A. M. Rimando, S. O. Duke, Natural
Products for Pest Management, ACS Symposium Series, Washington,
2
314.
38] D. Jie, D.-S. Cao, H.-Y. Miao, L. Shao, B.-C. Deng, Y.-H. Yun, N.-N. Wang,
A.-P. Lu, W.-B. Zeng, A. F. Chen, J. Cheminf. 2015, 7, DOI: 10.1186/
s13321-015-0109-z.
39] a) T. A. Walsh, Pest Manage. Sci. 2007, 63, 1165–1171; b) G. Jin, S. Lee,
M. Choi, S. Son, G.-W. Kim, J.-W. Oh, C. Lee, K. Lee, Eur. J. Med. Chem.
006, pp. 2–21.
6] B. A. Kulkarni, G. P. Roth, E. Lobkovsky, J. A. Porco, J. Comb. Chem. 2002,
, 56–72.
7] a) S. L. Schreiber, Science 2000, 287, 1964–1969; b) E. Lenci, G. Menchi,
A. Guarna, A. Trabocchi, J. Org. Chem. 2015, 80, 2182–2191; c) D. S. Tan,
Nat. Chem. Biol. 2005, 1, 74–84.
[
[
4
[
2
014, 75, 413–425.
[
[
40] X. He, Z. Yu, S. Jiang, P. Zhang, Z. Shang, Y. Lou, J. Wu, Bioorg. Med.
Chem. Lett. 2015, 25, 5601–5603.
41] S. Yoshida, D. A. Forno, J. H. Cock, K. A. Gomez, Laboratory Manual for
Physiological Studies of Rice, 3rd ed., International Rice Research Insti-
tute, Los BaÇos, 1976, pp. 61–62.
[8] a) R. A. Bauer, T. A. Wenderski, D. S. Tan, Nat. Chem. Biol. 2013, 9, 21–29;
b) F. Kopp, C. F. Stratton, L. B. Akella, D. S. Tan, Nat. Chem. Biol. 2012, 8,
358–365; c) H. S. G. Beckmann, F. Nie, C. E. Hagerman, H. Johansson,
Y. S. Tan, D. Wilcke, D. R. Spring, Nat. Chem. 2013, 5, 861–867.
[9] M. E. Maffei, G. Arimura, A. Mithofer, Nat. Prod. Rep. 2012, 29, 1288–
[
[
42] Q. Fu, Z. Zhang, C. Hu, F. Lai, Z. Sun, Applied Entomology & Zoology
1303.
2
001, 36, 111–116; Zoology 2001, 36, 111–116.
43] CCDC 1444188, 1444189, 1444187 and 1444190 (for 11 s, 12c, 14h and
6a, respectively) contain the supplementary crystallographic data for
[
[
10] Y.-P. Liu, R. Lai, Y.-G. Yao, Z.-K. Zhang, E.-T. Pu, X.-H. Cai, X.-D. Luo, Org.
Lett. 2013, 15, 4940–4943.
11] a) Y. Hirai, M. Doe, T. Kinoshita, Y. Morimoto, Chem. Lett. 2004, 33, 136–
1
this paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre.
137; b) B. Hagele, M. Rowell-Rahier, J. Evol. Biol. 2000, 13, 131–142.
[
[
12] M. Jiao, C. Ding, A. Zhang, Tetrahedron Lett. 2015, 56, 2799–2802.
13] a) R. B. Patil, S. D. Sawant, Der Pharma Chemica 2015, 7, 26–37; b) H. Va-
lizadeh, A. Shockravi, J. Heterocycl. Chem. 2006, 43, 763–765.
[
14] R. Ranga Rao, A. K. Tiwari, P. Prabhakar Reddy, K. Suresh Babu, G. Suresh,
A. Z. Ali, K. Madhusudana, S. B. Agawane, P. Badrinarayan, G. Narahar-
i Sastry, J. Madhusudana Rao, Med. Chem. Res. 2012, 21, 760–774.
Received: September 29, 2016
Published online on && &&, 2016
&
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FULL PAPERS
Natural-product-like libraries: Coumar-
in, chalcone, flavone, flavonol, isofla-
vone and isoquinolinone are six natural-
ly occurring compounds that are ubiqui-
tous in diverse plants. To extend molec-
ular diversity and discover chemical elic-
itors, the diversity-oriented synthesis is
reported of a natural-product-like li-
brary, in which the 3-methylfuran core is
fused to the six common natural prod-
uct scaffolds.
X. He, X. Chen, S. Lin, X. Mo, P. Zhou,
Z. Zhang, Y. Lu, Y. Yang, H. Gu, Z. Shang,*
Y. Lou,* J. Wu*
&& – &&
Diversity-Oriented Synthesis of
Natural-Product-like Libraries
Containing a 3-Methylbenzofuran
Moiety for the Discovery of New
Chemical Elicitors
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