Synthesis and insecticidal activity of new deoxypodophyllotoxin-based phenazine analogues against Mythimna separata walker

Article abstract of DOI:10.1021/jf4011033

In continuation of our program aimed at the discovery and development of natural-product-based insecticidal agents, a series of new deoxypodophyllotoxin- based phenazine analogues modified in their E-ring were prepared, and their structures were well characterized by ¹H NMR, HRMS, ESI-MS, IR, optical rotation, and mp. The absolute steric configuration of one key isomer was unambiguously confirmed by X-ray crystallography. Their insecticidal activity was examined against the pre-third-instar larvae of oriental armyworm, Mythimna separata (Walker) in vivo at the concentration of 1 mg/mL. All derivatives showed delayed insecticidal activity. Especially compound 9i, containing p-methoxybenzoylamnio at the C-9′ position of deoxypodophyllotoxin-based phenazine fragment, exhibited the most promising insecticidal activity with the final mortality rate of 72.4%. According to the symptoms of the tested M. separata, the derivatives likely displayed an antimolting hormone effect. In addition, preliminary structure-activity relationships were observed. These suggested that the proper length of the side chain of alkylacylamino might be important for their insecticidal activity, and introduction of the acylamino groups at the C-9′ position of deoxypodophyllotoxin-based phenazine fragment usually afforded more potent compounds than those containing the same ones at the C-10′ position. This will pave the way for further design, structural modification, and development of deoxypodophyllotoxin-based derivatives as insecticidal agents.

Full text of DOI:10.1021/jf4011033

Article
pubs.acs.org/JAFC
Synthesis and Insecticidal Activity of New Deoxypodophyllotoxin-
Based Phenazine Analogues against Mythimna separata Walker
Juanjuan Wang, Xiaoyan Zhi, Xiang Yu, and Hui Xu*
Laboratory of Pharmaceutical Design and Synthesis, College of Sciences, Northwest A&F University, Yangling 712100, Shannxi
Province, People’s Republic of China
ABSTRACT: In continuation of our program aimed at the discovery and development of natural-product-based insecticidal
agents, a series of new deoxypodophyllotoxin-based phenazine analogues modified in their E-ring were prepared, and their
structures were well characterized by 1H NMR, HRMS, ESI-MS, IR, optical rotation, and mp. The absolute steric configuration
of one key isomer was unambiguously confirmed by X-ray crystallography. Their insecticidal activity was examined against the
pre-third-instar larvae of oriental armyworm, Mythimna separata (Walker) in vivo at the concentration of 1 mg/mL. All
derivatives showed delayed insecticidal activity. Especially compound 9i, containing p-methoxybenzoylamnio at the C-9′ position
of deoxypodophyllotoxin-based phenazine fragment, exhibited the most promising insecticidal activity with the final mortality
rate of 72.4%. According to the symptoms of the tested M. separata, the derivatives likely displayed an antimolting hormone
effect. In addition, preliminary structure−activity relationships were observed. These suggested that the proper length of the side
chain of alkylacylamino might be important for their insecticidal activity, and introduction of the acylamino groups at the C-9′
position of deoxypodophyllotoxin-based phenazine fragment usually afforded more potent compounds than those containing the
same ones at the C-10′ position. This will pave the way for further design, structural modification, and development of
deoxypodophyllotoxin-based derivatives as insecticidal agents.
KEYWORDS: podophyllotoxin, deoxypodophyllotoxin, phenazine, structural modification, botanical insecticide, insecticidal activity,
Mythimna separata Walker
INTRODUCTION
■
Repeat application of synthetic agrochemicals over years has
resulted in the development of resistance in insect pest
populations and environmental problems.1,2 On the other hand,
plant secondary metabolites result from the interaction between
plants and the environment (life and nonlife) during the long
period of evolution in plants, and pesticides produced from
plant secondary metabolites may lead to less or slower
resistance development and lower pollution.3 Consequently,
the discovery of new insecticidal compounds directly from
Figure 1. Chemical structures of podophyllotoxin (1) and
deoxypodophyllotoxin (2).
plant secondary metabolites or by using them as the lead
compounds for further structural modifications has recently
become an important area of research and development of new
pesticides.4−10 For example, nowadays some botanical
insecticides such as nicotine, pyrethrum, and neem extracts
are made by plants as defenses against insect pests.11
compounds exhibited insecticidal activity equal to or higher
than that of toosendanin, a commercial botanical insecticide
isolated from Melia azedarach.22−27 On the other hand, a series
of new phenazine derivatives of 4β-acyloxypodophyllotoxin
modified in the E-ring were prepared, and some compounds
showed potent insecticidal activity.28 Encouraged by the above-
mentioned results, we herein wanted to prepare a series of 4-
deoxypodophyllotoxin-based phenazine derivatives by intro-
duction of the phenazine fragment in the E-ring (Scheme 1).
Their insecticidal activity was evaluated against the pre-third-
instar larvae of oriental armyworm, Mythimna separata
(Walker) in vivo.
Podophyllotoxin (1, Figure 1), a main secondary metabolite
isolated from the roots and rhizomes of Podophyllum species
such as Podophyllum hexandrum and Podophyllum peltatum, has
been used as a unique lead compound for the preparation of
potent antitumor drugs such as etoposide (VP-16), teniposide
(VM-26), and etopophos against various cancers including
small cell lung cancer, testicular carcinoma, lymphoma, and
Kaposi’s sarcoma.12−15 Additionally, extensive chemical mod-
ification of compound 1 has been reported leading to
insecticidal and antifungal agents.16−21
More recently, we have studied the insecticidal activity of 2β-
chloropodophyllotoxin or 2α/β-bromopodophyllotoxin deriva-
tives modified in the C-ring and 4-deoxypodophyllotoxin (2,
Figure 1) derivatives modified in the E-ring and found some
Received: March 11, 2013
Revised: June 11, 2013
Accepted: June 11, 2013
© XXXX American Chemical Society
A
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a
Scheme 1
a
Reagents and conditions: (a) H2, 10% Pd/C, 95 °C, 5 h, 66%; (b) concd HNO3, 0 °C, 4 min, 73%; (c) 1,2-diaminobenzene, room temperature, 0.5
h, 82%; (d) 4-nitro-1,2-phenylenediamine, room temperature, 5 h, 29% (5) and 59% (6); (e) SnCl2·2H2O, N2, reflux, 7 h, 81% (7) or 85% (8); (f)
RCOCl (11a−e and h), Et3N, 0 °C, room temperature, 1−9.5 h, 28−89%, or RCOCl (11f,g,i, and j), Et3N, 0 °C, room temperature, reflux, 3−80 h,
32−92%.
Avance DMX 400 or 500 MHz instrument in CDCl3 using
MATERIALS AND METHODS
■
tetramethylsilane (TMS) as the internal standard. High-resolution
General. Podophyllotoxin was purchased from Gansu Gerui
mass spectra (HR-MS) were carried out with an IonSpec 4.7 T FTMS
Medicinal Materials Co., Ltd. All reagents and solvents were of
instrument.
reagent grade or purified according to standard methods before use.
Analytical thin-layer chromatography (TLC) and preparative thin-layer
chromatography (PTLC) were performed with silica gel plates using
silica gel 60 GF254 (Qingdao Haiyang Chemical Co., Ltd.). Silica gel
Synthesis of 4-Deoxypodophyllotoxin (2). A mixture of 10%
palladium/carbon (12 g) and podophyllotoxin (1, 16 g, 38.6 mmol) in
acetic acid solution (150 mL) was stirred at 95 °C under 2 atm of
hydrogen for 5 h. After the catalyst and solvent were removed, the
column chromatography was performed with silica gel 200−300 mesh
residue was separated by silica gel column chromatography to give the
crude product, which was further purified by recrystallization from
methanol to afford 2 in 66% yield as a white solid: mp = 165−167 °C
(Qingdao Haiyang Chemical Co., Ltd.). Melting points (mp) were
determined on an XT-4 digital melting point apparatus (Beijing Tech
Instrument Co., Ltd.) and were uncorrected. Infrared spectra (IR)
were recorded on a Bruker TENSOR 27 spectrometer. Proton nuclear
magnetic resonance spectra (1H NMR) were recorded on a Bruker
[literature, 166−168 °C];29 [α]20 = −116 (c 1 mg/mL, CHCl3); IR
D
1
2892, 2831, 1763, 1587, 1482, 1457, 1223, 1120, 925, 768 cm−1; H
B
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Journal of Agricultural and Food Chemistry
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NMR (400 MHz, CDCl3) δ 6.67 (s, 1H, H-5), 6.52 (s, 1H, H-8), 6.34
(s, 2H, H-2′,6′), 5.93 (d, J = 8.0 Hz, 2H, OCH2O), 4.60 (s, 1H, H-1),
4.43−4.48 (m, 1H, H-11), 3.89−3.95 (m, 1H, H-11), 3.79 (s, 3H, 4′-
OCH3), 3.75 (s, 6H, 3′, 5′-OCH3), 3.06−3.09 (m, 1H, H-4), 2.71−
2.78 (m, 3H, H-2,3,4); MS (EI) m/z (%) 398 (M+, 100).
2H, OCH2O), 4.84 (s, 1H, H-1), 4.40−4.43 (m, 1H, H-11), 4.34 (s,
2H, NH2), 4.19 (s, 3H, 3′-OCH3), 3.94−3.98 (m, 1H, H-11), 3.10−
3.13 (m, 1H, H-4), 2.77−2.94 (m, 3H, H-2,3,4). HRMS (ESI) calcd
for C26H22N3O5 ([M + H]+), 456.1554; found, 456.1543.
Data for Compound 8: rufous solid; mp = 190−192 °C; [α]20
=
D
Synthesis of 4′,5′-Didemethoxy-4′,5′-dioxodeoxypodophyllotox-
in (3). Concentrated nitric acid (1.2 mL) was rapidly added to a
solution of 2 (60 mg, 0.15 mmol) in propionic acid (1.2 mL) at 0 °C.
After stirring at 0 °C for 4 min, the dark red solution was poured into
water (10 mL) and extracted with CH2Cl2 (2 × 20 mL). The organic
layer was then washed with saturated aqueous NaHCO3 and brine,
dried over Na2SO4, concentrated in vacuo, and purified by
recrystallization from CH2Cl2 and petroleum ether to afford 3 in
73% yield as a crimson solid: mp = 184−186 °C [literature, 182−184
+27 (c 3.9 mg/mL, CHCl3); 1H NMR (400 MHz, CDCl3) δ 8.14 (d, J
= 8.8 Hz, 1H), 7.40 (s, 1H, H-6′), 7.24 (s, 1H), 7.03 (s, 1H, H-2′),
6.90 (s, 1H), 6.69 (s, 1H, H-5), 6.56 (s, 1H, H-8), 5.92 (d, J = 7.6 Hz,
2H, OCH2O), 4.83 (s, 1H, H-1), 4.40−4.43 (m, 3H, H-11, NH2), 4.19
(s, 3H, 3′-OCH3), 3.93−3.97 (m, 1H, H-11), 3.09−3.12 (m, 1H, H-
4), 2.76−2.94 (m, 3H, H-2,3,4). HRMS (ESI) calcd for C26H22N3O5
([M + H]+), 456.1554; found, 456.1548.
Synthesis of Compounds 9a−c,e−j, 10a−j, and 10g′. To a stirred
mixture of 7 or 8 (45.5 mg, 0.1 mmol) and Et3N (0.12 mmol) in
CH2Cl2 (5 mL) at 0 °C, was added dropwise a solution of acyl
chlorides RCOCl (11a−j, 0.11 mmol) in CH2Cl2 (5 mL). After this
addition to 11a−e and h, the reaction was allowed to proceed at room
temperature, and the mixture was stirred at room temperature for 1−
9.5 h, whereas after the addition to 11f,g,i, and j, the reaction was first
allowed to proceed at room temperature and then the mixture was
refluxed for 3−80 h. Subsequently, CH2Cl2 (10 mL) and water (20
mL) were added to the mixture, and the organic phase was separated.
The water phase was further extracted with CH2Cl2 (2 × 40 mL).
Finally, the combined organic phase was washed by brine, dried over
anhydrous Na2SO4, concentrated in vacuo, and purified by PTLC to
give the target compounds.
°C];30 [α]20 = −35 (c 2.4 mg/mL, CHCl3); H NMR (400 MHz,
1
D
CDCl3) δ 6.62 (s, 1H, H-6′), 6.51 (d, J = 1.2 Hz, 1H, H-5), 6.50 (s,
1H, H-8), 5.95 (dd, J = 1.2, 6.4 Hz, 2H, OCH2O), 5.35 (s, 1H, H-2′),
4.59−4.63 (m, 1H, H-11), 4.26 (d, J = 5.6 Hz, 1H, H-1), 4.01−4.05
(m, 1H, H-11), 3.84 (s, 3H, 3′-OCH3), 3.03−3.05 (m, 1H, H-4),
2.88−2.92 (m, 1H, H-2), 2.71−2.79 (m, 2H, H-3,4). HRMS (ESI)
calcd for C20H17O7 ([M + H]+), 369.0968; found, 369.0965.
Synthesis of Phenazine Derivative of Deoxypodophyllotoxin (4).
A solution of o-phenylenediamine (35.6 mg, 0.33 mmol) in CHCl3 (5
mL) was added dropwise to a solution of 3 (110 mg, 0.3 mmol) in
CHCl3 (5 mL) at room temperature. After 0.5 h, the mixture was
concentrated in vacuo and purified by PTLC to afford 4 in 82% yield
as a yellow solid: mp = 127−129 °C; [α]20 = +5.3 (c 2.2 mg/mL,
Data for Compound 9a: yield = 74%; yellow solid; mp = 280−282
D
CHCl3); 1H NMR (500 MHz, CDCl3) δ 8.38−8.40 (m, 1H), 8.10 (d,
J = 8.0 Hz, 1H), 7.80−7.81 (m, 2H), 7.56 (s, 1H, H-6′), 7.06 (s, 1H,
H-2′), 6.71 (s, 1H, H-5), 6.56 (s, 1H, H-8), 5.94 (d, J = 8.0 Hz, 2H,
OCH2O), 4.88 (d, J = 4.0 Hz, 1H, H-1), 4.41−4.44 (m, 1H, H-11),
4.24 (s, 3H, 3′-OCH3), 3.95−3.99 (m, 1H, H-11), 3.13−3.15 (m, 1H,
H-4), 2.80−2.96 (m, 3H, H-2,3,4). HRMS (ESI) calcd for
C26H21N2O5 ([M + H]+), 441.1445; found, 441.1434.
°C; [α]21 = +20 (c 3.1 mg/mL, CHCl3); 1H NMR (400 MHz,
D
CDCl3) δ 8.13 (d, J = 8.8 Hz, 2H), 7.90 (s, 1H), 7.51 (s, 1H, H-6′),
7.05 (s, 1H, H-2′), 6.71 (s, 1H, H-5), 6.61 (s, 1H, H-8), 5.95 (d, J =
3.2 Hz, 2H, OCH2O), 4.87 (d, J = 3.6 Hz, 1H, H-1), 4.43−4.46 (m,
1H, H-11), 4.10 (s, 3H, 3′-OCH3), 3.95−3.99 (m, 1H, H-11), 3.12−
3.16 (m, 1H, H-4), 2.79−2.97 (m, 3H, H-2,3,4), 2.11 (s, 3H, CH3).
HRMS (ESI) calcd for C28H24N3O6 ([M + H]+), 498.1659; found,
498.1652.
Synthesis of Phenazine Derivative of Deoxypodophyllotoxin (5
and 6). A solution of 4-nitro-1,2-phenylenediamine (50.5 mg, 0.33
mmol) in CHCl3 (5 mL) was added dropwise to a solution of 3 (110
mg, 0.3 mmol) in CHCl3 (5 mL) at room temperature. After 5 h, the
mixture was concentrated in vacuo and purified by PTLC to afford 5
and 6 in 29 and 59% yields, respectively.
Data for Compound 9b: yield = 87%; yellow solid; mp = 265−267
°C; [α]21 = +25 (c 2.2 mg/mL, CHCl3); 1H NMR (500 MHz,
D
CDCl3) δ 8.65 (s, 1H, NH), 8.57 (s, 1H), 8.09 (d, J = 9.5 Hz, 1H),
7.99 (d, J = 9.5 Hz, 1H), 7.55 (s, 1H, H-6′), 7.03 (s, 1H, H-2′), 6.71
(s, 1H, H-5), 6.56 (s, 1H, H-8), 5.94 (d, J = 8.0 Hz, 2H, OCH2O),
4.87 (d, J = 4.5 Hz, 1H, H-1), 4.41−4.44 (m, 1H, H-11), 4.28 (s, 2H,
CH2Cl), 4.22 (s, 3H, 3′-OCH3), 3.95−3.99 (m, 1H, H-11), 3.13−3.15
(m, 1H, H-4), 2.80−2.96 (m, 3H, H-2,3,4). HRMS (ESI) calcd for
C28H23N3O6Cl ([M + H]+), 532.1269; found, 532.1258.
Data for Compound 5: orange solid; mp = 174−176 °C; [α]20
=
D
+28 (c 3.1 mg/mL, CHCl3); 1H NMR (400 MHz, CDCl3) δ 9.37 (d, J
= 2.4 Hz, 1H), 8.53 (dd, J = 2.4, 9.2 Hz, 1H), 8.24 (d, J = 9.6 Hz, 1H),
7.62 (d, J = 1.2 Hz, 1H, H-6′), 7.10 (d, J = 0.8 Hz, 1H, H-2′), 6.74 (s,
1H, H-5), 6.55 (s, 1H, H-8), 5.95 (dd, J = 1.2, 4.4 Hz, 2H, OCH2O),
4.90 (d, J = 5.2 Hz, 1H, H-1), 4.43−4.47 (m, 1H, H-11), 4.26 (s, 3H,
3′-OCH3), 3.98−4.02 (m, 1H, H-11), 3.15−3.18 (m, 1H, H-4), 2.97−
3.01(m, 1H, H-2), 2.80−2.89 (m, 2H, H-3,4). HRMS (ESI) calcd for
C26H20N3O7 ([M + H]+), 486.1295; found, 486.1287.
Data for Compound 9c: yield = 80%; yellow solid; mp = 274−276
°C; [α]21 = +27 (c 4.5 mg/mL, CHCl3); 1H NMR (400 MHz,
D
CDCl3) δ 8.20 (d, J = 8.8 Hz, 2H), 7.97 (s, 1H), 7.51 (s, 1H, H-6′),
7.04 (s, 1H, H-2′), 6.70 (s, 1H, H-5), 6.59 (s, 1H, H-8), 5.94 (d, J =
4.4 Hz, 2H, OCH2O), 4.86 (d, J = 4.4 Hz, 1H, H-1), 4.42−4.45 (m,
1H, H-11), 4.14 (s, 3H, 3′-OCH3), 3.94−3.99 (m, 1H, H-11), 3.11−
3.14 (m, 1H, H-4), 2.78−2.96 (m, 3H, H-2,3,4), 2.41−2.50 (m, 2H,
CH3CH2), 1.22−1.29 (m, 3H, CH3CH2). HRMS (ESI) calcd for
C29H26N3O6 ([M + H]+), 512.1816; found, 512.1802.
Data for Compound 6: orange solid; mp = 272−274 °C; [α]20
=
D
1
+31 (c 4.4 mg/mL, CHCl3); H NMR (400 MHz, CDCl3) δ 9.06 (s,
1H), 8.53 (s, 2H), 7.65 (s, 1H, H-6′), 7.10 (s, 1H, H-2′), 6.75 (s, 1H,
H-5), 6.55 (s, 1H, H-8), 5.97 (s, 2H, OCH2O), 4.89 (d, J = 4.8 Hz,
1H, H-1), 4.44−4.48 (m, 1H, H-11), 4.26 (s, 3H, 3′-OCH3), 3.98−
4.03 (m, 1H, H-11), 3.17−3.19 (m, 1H, H-4), 2.97−3.01 (m, 1H, H-
2), 2.84−2.89 (m, 2H, H-3, 4). HRMS (ESI) calcd for C26H20N3O7
([M + H]+), 486.1295; found, 486.1286.
Data for Compound 9e: yield = 79%; yellow solid; mp = 167−169
°C; [α]21 = +16 (c 2.0 mg/mL, CHCl3); 1H NMR (400 MHz,
D
CDCl3) δ 8.34 (d, J = 2.0 Hz, 1H, NH), 8.20 (d, J = 9.2 Hz, 1H), 8.04
(d, J = 9.2 Hz, 1H), 7.61 (s, 1H), 7.54 (s, 1H, H-6′), 7.02 (s, 1H, H-
2′), 6.71 (s, 1H, H-5), 6.56 (s, 1H, H-8), 5.94 (d, J = 6.0 Hz, 2H,
OCH2O), 4.86 (d, J = 4.8 Hz, 1H, H-1), 4.41−4.45 (m, 1H, H-11),
4.21 (s, 3H, 3′-OCH3), 3.95−3.99 (m, 1H, H-11), 3.12−3.15 (m, 1H,
H-4), 2.79−2.96 (m, 3H, H-2,3,4), 2.44 (t, J = 7.6 Hz, 2H,
CH2CONH), 1.75−1.81 (m, 2H, CH2CH2CONH), 1.32−1.41 (m,
6H, CH3CH2CH2CH2CH2CH2CONH), 0.87 (t, J = 6.8 Hz, 3H,
CH3). HRMS (ESI) calcd for C33H34N3O6 ([M + H]+), 568.2442;
found, 568.2429.
Synthesis of Compounds 7 and 8. A mixture of 5 or 6 (121 mg,
0.25 mmol) and SnCl2·2H2O (395 mg, 1.75 mmol) in ethyl acetate
(15 mL) was refluxed under N2 for 7 h. After cooling, the pH value of
the mixture (the initial pH value of the mixture was 3−4) was adjusted
to 8−9 by the addition of saturated aqueous NaHCO3 (30 mL). Then
the mixture was filtered, and the water layer was extracted with ethyl
acetate (3 × 50 mL). Then the combined organic phase was dried over
anhydrous Na2SO4, concentrated in vacuo, and purified by PTLC to
give 7 in 81% yield or 8 in 85% yield.
Data for Compound 9f: yield = 84%; yellow solid; mp = 215−217
Data for Compound 7: rufous solid; mp = 184−186 °C; [α]20
=
°C; [α]20 = +34 (c 3.1 mg/mL, CHCl3); 1H NMR (500 MHz,
D
D
+39 (c 3.5 mg/mL, CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.88 (d, J
= 9.2 Hz, 1H), 7.48 (s, 1H, H-6′), 7.34 (s, 1H), 7.29 (s, 1H), 6.94 (s,
1H, H-2′), 6.69 (s, 1H, H-5), 6.56 (s, 1H, H-8), 5.93 (d, J = 7.6 Hz,
CDCl3) δ 8.49 (s, 1H, NH), 8.28 (d, J = 9.5 Hz, 2H), 8.08 (s, 1H),
7.89−7.90 (m, 2H), 7.47−7.52 (m, 4H), 7.03 (s, 1H, H-2′), 6.70 (s,
1H, H-5), 6.57 (s, 1H, H-8), 5.93 (d, J = 8.5 Hz, 2H, OCH2O), 4.86
C
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(d, J = 4.5 Hz, 1H, H-1), 4.42−4.45 (m, 1H, H-11), 4.18 (s, 3H, 3′-
OCH3), 3.95−3.99 (m, 1H, H-11), 3.12−3.14 (m, 1H, H-4), 2.79−
2.95 (m, 3H, H-2,3,4). HRMS (ESI) calcd for C33H26N3O6 ([M +
H]+), 560.1816; found, 560.1804.
7.5 Hz, 3H, CH3CH2). HRMS (ESI) calcd for C29H26N3O6 ([M +
H]+), 512.1816; found, 512.1803.
Data for Compound 10d: yield = 28%; yellow solid; mp = 200−
1
202 °C; [α]21 = +23 (c 3.3 mg/mL, CHCl3); H NMR (400 MHz,
D
Data for Compound 9g: yield = 92%; yellow solid; mp = 222−224
CDCl3) δ: 8.45 (s, 1H, NH), 8.31 (d, J = 9.2 Hz, 1H), 7.87−7.91 (m,
2H), 7.51 (s, 1H, H-6′), 7.02 (s, 1H, H-2′), 6.71 (s, 1H, H-5), 6.56 (s,
1H, H-8), 5.94 (d, J = 4.8 Hz, 2H, OCH2O), 5.86 (s, 1H, CCH2),
5.54 (s, 1H, CCH2), 4.86 (d, J = 3.6 Hz, 1H, H-1), 4.41−4.45 (m,
1H, H-11), 4.22 (s, 3H, 3′-OCH3), 3.95−3.99 (m, 1H, H-11), 3.12−
3.16 (m, 1H, H-4), 2.78−2.95 (m, 3H, H-2,3,4), 2.10 (s, 3H, CH3).
HRMS (ESI) calcd for C30H26N3O6 ([M + H]+), 524.1816; found,
524.1807.
°C; [α]21 = +17 (c 3.0 mg/mL, CHCl3); 1H NMR (400 MHz,
D
CDCl3) δ 8.48 (s, 1H, NH), 8.34 (d, J = 9.6 Hz, 1H), 8.03−8.14 (m,
2H), 7.87 (d, J = 7.6 Hz, 1H), 7.52−7.55 (m, 2H), 7.37−7.41 (m,
1H), 7.09−7.12 (m, 1H), 7.02 (s, 1H, H-2′), 6.69 (s, 1H, H-5), 6.57
(s, 1H, H-8), 5.94 (d, J = 4.8 Hz, 2H, OCH2O), 4.85 (d, J = 4.4 Hz,
1H, H-1), 4.43−4.46 (m, 1H, H-11), 4.19 (s, 3H, 3′-OCH3), 3.95−
4.00 (m, 1H, H-11), 3.11−3.14 (m, 1H, H-4), 2.79−2.96 (m, 3H, H-
2,3,4). HRMS (ESI) calcd for C33H25N3O6I ([M + H]+), 686.0782;
found, 686.0771.
Data for Compound 10e: yield = 81%; yellow solid; mp = 166−
1
168 °C; [α]20 = +22 (c 3.0 mg/mL, CHCl3); H NMR (500 MHz,
D
Data for Compound 9h: yield = 86%; yellow solid; mp = 141−143
CDCl3) δ 8.39 (s, 1H, NH), 8.29 (d, J = 9.0 Hz, 1H), 7.89 (d, J = 8.0
Hz, 1H), 7.70 (s, 1H), 7.50 (s, 1H, H-6′), 7.00 (s, 1H, H-2′), 6.68 (s,
1H, H-5), 6.55 (s, 1H, H-8), 5.93 (d, J = 7.5 Hz, 2H, OCH2O), 4.85
(d, J = 4.0 Hz, 1H, H-1), 4.40−4.42 (m, 1H, H-11), 4.21 (s, 3H, 3′-
OCH3), 3.94−3.98 (m, 1H, H-11), 3.10−3.12 (m, 1H, H-4), 2.80−
2.95 (m, 3H, H-2,3,4), 2.42 (t, J = 7.0 Hz, 2H, CH2CONH), 1.73−
1.76 (m, 2H, CH2 CH2 CONH), 1.29−1.36 (m, 6H,
CH3CH2CH2CH2CH2CH2CONH), 0.85 (t, J = 6.5 Hz, 3H, CH3).
HRMS (ESI) calcd for C33H34N3O6 ([M + H]+), 568.2442; found,
568.2430.
°C; [α]21 = +25 (c 1.5 mg/mL, CHCl3); 1H NMR (400 MHz,
D
CDCl3) δ 8.52 (d, J = 2.0 Hz, 1H, NH), 8.24 (dd, J = 2.4, 9.6 Hz, 1H),
8.17 (s, 1H), 8.10 (d, J = 9.6 Hz, 1H), 7.55 (s, 1H, H-6′), 7.49 (s, 1H),
7.41−7.46 (m, 2H), 7.12−7.14 (m, 1H), 7.03 (s, 1H, H-2′), 6.72 (s,
1H, H-5), 6.57 (s, 1H, H-8), 5.94 (d, J = 5.6 Hz, 2H, OCH2O), 4.87
(d, J = 4.4 Hz, 1H, H-1), 4.42−4.46 (m, 1H, H-11), 4.23 (s, 3H, 3′-
OCH3), 3.96−4.00 (m, 1H, H-11), 3.89 (s, 3H, OCH3), 3.13−3.16
(m, 1H, H-4), 2.80−2.97 (m, 3H, H-2,3,4). HRMS (ESI) calcd for
C34H28N3O7 ([M + H]+), 590.1921; found, 590.1910.
Data for Compound 9i: yield = 78%; yellow solid; mp = 196−198
Data for Compound 10f: yield = 82%; yellow solid; mp = 213−
1
°C; [α]21 = +21 (c 2.0 mg/mL, CHCl3); 1H NMR (400 MHz,
215 °C; [α]20 = +27 (c 3.2 mg/mL, CHCl3); H NMR (500 MHz,
D
D
CDCl3) δ 8.45 (d, J = 2.0 Hz, 1H, NH), 8.29 (dd, J = 2.4, 9.6 Hz, 2H),
8.06 (d, J = 9.2 Hz, 1H), 7.88 (d, J = 8.4 Hz, 2H), 7.53 (s, 1H, H-6′),
7.03 (s, 1H, H-2′), 6.96 (d, J = 8.0 Hz, 2H), 6.71 (s, 1H, H-5), 6.57 (s,
1H, H-8), 5.94 (d, J = 6.4 Hz, 2H, OCH2O), 4.86 (d, J = 4.8 Hz, 1H,
H-1), 4.42−4.45 (m, 1H, H-11), 4.20 (s, 3H, 3′-OCH3), 3.95−4.00
(m, 1H, H-11), 3.87 (s, 3H, OCH3), 3.12−3.15 (m, 1H, H-4), 2.79−
2.97 (m, 3H, H-2,3,4). HRMS (ESI) calcd for C34H28N3O7 ([M +
H]+), 590.1921; found, 590.1908.
CDCl3) δ 8.53 (s, 1H, NH), 8.34 (d, J = 9.5 Hz, 2H), 8.04−8.09 (m,
1H), 7.90 (d, J = 7.5 Hz, 2H), 7.46−7.57 (m, 4H), 7.03 (s, 1H, H-2′),
6.68 (s, 1H, H-5), 6.55 (s, 1H, H-8), 5.92 (d, J = 11.0 Hz, 2H,
OCH2O), 4.85 (d, J = 4.0 Hz, 1H, H-1), 4.41−4.43 (m, 1H, H-11),
4.21 (s, 3H, 3′-OCH3), 3.94−3.98 (m, 1H, H-11), 3.10−3.13 (m, 1H,
H-4), 2.77−2.95 (m, 3H, H-2,3,4). HRMS (ESI) calcd for
C33H26N3O6 ([M + H]+), 560.1816; found, 560.1809.
Data for Compound 10g: yield = 32%; yellow solid; mp = 204−
1
Data for Compound 9j: yield = 68%; yellow solid; mp = 201−203
206 °C; [α]21 = +19 (c 4.7 mg/mL, CHCl3); H NMR (400 MHz,
D
°C; [α]21 = +23 (c 3.3 mg/mL, CHCl3); 1H NMR (400 MHz,
CDCl3) δ 8.51 (s, 1H, NH), 8.36 (d, J = 9.2 Hz, 1H), 8.02−8.04 (m,
2H), 7.89 (d, J = 7.6 Hz, 1H), 7.53−7.56 (m, 2H), 7.40−7.43 (m,
1H), 7.13−7.16 (m, 1H), 7.02 (s, 1H, H-2′), 6.68 (s, 1H, H-5), 6.56
(s, 1H, H-8), 5.93 (d, J = 6.4 Hz, 2H, OCH2O), 4.87 (d, J = 3.2 Hz,
1H, H-1), 4.42−4.45 (m, 1H, H-11), 4.23 (s, 3H, 3′-OCH3), 3.95−
3.99 (m, 1H, H-11), 3.10−3.13 (m, 1H, H-4), 2.78−2.95 (m, 3H, H-
2,3,4). HRMS (ESI) calcd for C33H25N3O6I ([M + H]+), 686.0782;
found, 686.0769.
D
CDCl3) δ 8.47 (s, 1H, NH), 8.35 (s, 1H), 8.27 (dd, J = 2.0, 9.2 Hz,
1H), 8.07 (d, J = 9.2 Hz, 1H), 7.53 (s, 2H), 7.44 (d, J = 8.0 Hz, 1H),
7.03 (s, 1H, H-2′), 6.89 (d, J = 6.4 Hz, 1H), 6.70 (s, 1H, H-5), 6.56 (s,
1H, H-8), 5.93 (d, J = 6.4 Hz, 2H, OCH2O), 4.86 (d, J = 4.8 Hz, 1H,
H-1), 4.42−4.45 (m, 1H, H-11), 4.19 (s, 3H, 3′-OCH3), 3.93−3.99
(m, 7H, H-11, 2 × OCH3), 3.12−3.15 (m, 1H, H-4), 2.79−2.96 (m,
3H, H-2,3,4). HRMS (ESI) calcd for C35H30N3O8 ([M + H]+),
620.2027; found, 620.2013.
Data for Compound 10g′: yield = 57%; yellow solid; mp = 172−
1
Data for Compound 10a: yield = 68%; yellow solid; mp = 214−
174 °C; [α]21 = +9 (c 4.8 mg/mL, CHCl3); H NMR (400 MHz,
D
1
216 °C; [α]20 = +22 (c 3.1 mg/mL, CHCl3); H NMR (500 MHz,
CDCl3) δ 8.35 (d, J = 8.8 Hz, 1H), 8.25 (s, 1H), 7.90 (d, J = 8.8 Hz,
1H), 7.71 (d, J = 8.0 Hz, 2H), 7.52−7.56 (m, 3H), 7.23−7.20 (m,
2H), 7.04 (s, 1H, H-2′), 6.94−6.97 (m, 2H), 6.72 (s, 1H, H-5), 6.55
(s, 1H, H-8), 5.95 (s, 2H, OCH2O), 4.87 (d, J = 4.0 Hz, 1H, H-1),
4.43−4.46 (m, 1H, H-11), 4.22 (s, 3H, 3′-OCH3), 3.96−4.00 (m, 1H,
H-11), 3.13−3.16 (m, 1H, H-4), 2.79−2.98 (m, 3H, H-2,3,4). HRMS
(ESI) calcd for C40H28N3O7I2 ([M + H]+), 916.0011; found,
915.9999.
D
CDCl3) δ 8.44 (s, 1H, NH), 8.27 (d, J = 9.5 Hz, 1H), 8.03 (s, 1H),
7.85 (d, J = 9.0 Hz, 1H), 7.50 (s, 1H, H-6′), 7.01 (s, 1H, H-2′), 6.67
(s, 1H, H-5), 6.54 (s, 1H, H-8), 5.92 (d, J = 8.5 Hz, 2H, OCH2O),
4.85 (d, J = 4.0 Hz, 1H, H-1), 4.40−4.43 (m, 1H, H-11), 4.21 (s, 3H,
3′-OCH3), 3.94−3.98 (m, 1H, H-11), 3.08−3.11 (m, 1H, H-4), 2.77−
2.95 (m, 3H, H-2,3,4), 2.25 (s, 3H, CH3). HRMS (ESI) calcd for
C28H24N3O6 ([M + H]+), 498.1659; found, 498.1655.
Data for Compound 10b: yield = 89%; yellow solid; mp = 191−
Data for Compound 10h: yield = 81%; yellow solid; mp = 145−
1
1
193 °C; [α]20 = +29 (c 3.9 mg/mL, CHCl3); H NMR (500 MHz,
147 °C; [α]21 = +13 (c 2.9 mg/mL, CHCl3); H NMR (400 MHz,
D
D
CDCl3) δ 8.57 (s, 2H), 8.35 (d, J = 9.0 Hz, 1H), 7.80 (d, J = 9.5 Hz,
1H), 7.53 (s, 1H, H-6′), 7.03 (s, 1H, H-2′), 6.71 (s, 1H, H-5), 6.56 (s,
1H, H-8), 5.94 (d, J = 7.0 Hz, 2H, OCH2O), 4.86 (d, J = 5.0 Hz, 1H,
H-1), 4.42−4.44 (m, 1H, H-11), 4.27 (s, 2H, CH2Cl), 4.23 (s, 3H, 3′-
OCH3), 3.95−3.99 (m, 1H, H-11), 3.13−3.15 (m, 1H, H-4), 2.79−
2.96 (m, 3H, H-2,3,4). HRMS (ESI) calcd for C28H23N3O6Cl ([M +
H]+), 532.1269; found, 532.1263.
CDCl3) δ 8.53 (s, 1H, NH), 8.34 (d, J = 9.2 Hz, 1H), 8.27 (s, 1H),
7.98 (dd, J = 2.4, 9.2 Hz, 1H), 7.51 (d, J = 2.0 Hz, 1H, H-6′), 7.45−
7.46 (m, 1H), 7.36−7.44 (m, 2H), 7.08−7.10 (m, 1H), 7.02 (d, J = 0.8
Hz, 1H, H-2′), 6.70 (s, 1H, H-5), 6.56 (s, 1H, H-8), 5.93 (dd, J = 1.2,
6.8 Hz, 2H, OCH2O), 4.86 (d, J = 4.8 Hz, 1H, H-1), 4.41−4.45 (m,
1H, H-11), 4.22 (s, 3H, 3′-OCH3), 3.95−3.99 (m, 1H, H-11), 3.86 (s,
3H, OCH3), 3.12−3.15 (m, 1H, H-4), 2.78−2.96 (m, 3H, H-2,3,4).
HRMS (ESI) calcd for C34H28N3O7 ([M + H]+), 590.1921; found,
590.1905.
Data for Compound 10c: yield = 84%; yellow solid; mp = 204−
1
206 °C; [α]21 = +21 (c 2.0 mg/mL, CHCl3); H NMR (500 MHz,
D
CDCl3) δ 8.38 (s, 1H, NH), 8.29 (d, J = 9.5 Hz, 1H), 7.89 (d, J = 9.5
Hz, 1H), 7.61 (s, 1H), 7.51 (s, 1H, H-6′), 7.01 (s, 1H, H-2′), 6.69 (s,
1H, H-5), 6.55 (s, 1H, H-8), 5.94 (d, J = 6.5 Hz, 2H, OCH2O), 4.86
(d, J = 4.5 Hz, 1H, H-1), 4.41−4.44 (m, 1H, H-11), 4.22 (s, 3H, 3′-
OCH3), 3.94−3.98 (m, 1H, H-11), 3.11−3.13 (m, 1H, H-4), 2.80−
2.95 (m, 3H, H-2,3,4), 2.46 (q, J = 7.5 Hz, 2H, CH3CH2), 1.27 (t, J =
Data for Compound 10i: yield = 81%; yellow solid; mp = 217−219
°C; [α]21 = +35 (c 3.2 mg/mL, CHCl3); 1H NMR (400 MHz,
D
CDCl3) δ 8.48 (s, 1H, NH), 8.32 (d, J = 9.2 Hz, 1H), 8.26 (s, 1H),
8.01 (d, J = 9.2 Hz, 1H), 7.87 (d, J = 8.0 Hz, 2H), 7.50 (s, 1H, H-6′),
7.01 (s, 1H, H-2′), 6.94 (d, J = 8.0 Hz, 2H), 6.69 (s, 1H, H-5), 6.55 (s,
1H, H-8), 5.92 (d, J = 8.0 Hz, 2H, OCH2O), 4.85 (d, J = 4.0 Hz, 1H,
D
dx.doi.org/10.1021/jf4011033 | J. Agric. Food Chem. XXXX, XXX, XXX−XXX

Journal of Agricultural and Food Chemistry
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H-1), 4.41−4.44 (m, 1H, H-11), 4.21 (s, 3H, 3′-OCH3), 3.94−3.99
(m, 1H, H-11), 3.86 (s, 3H, OCH3), 3.11−3.14 (m, 1H, H-4), 2.77−
2.95 (m, 3H, H-2,3,4). HRMS (ESI) calcd for C34H28N3O7 ([M +
H]+), 590.1921; found, 590.1906.
Data for Compound 10j: yield = 70%; yellow solid; mp = 202−204
°C; [α]21 = +32 (c 4.2 mg/mL, CHCl3); 1H NMR (400 MHz,
D
CDCl3) δ 8.51 (s, 1H, NH), 8.32−8.35 (m, 2H), 7.99 (d, J = 9.2 Hz,
1H), 7.50 (d, J = 4.4 Hz, 2H), 7.44 (d, J = 8.0 Hz, 1H), 7.02 (s, 1H, H-
2′), 6.88 (d, J = 8.0 Hz, 1H), 6.69 (s, 1H, H-5), 6.55 (s, 1H, H-8), 5.92
(d, J = 8.0 Hz, 2H, OCH2O), 4.85 (d, J = 3.6 Hz, 1H, H-1), 4.41−4.44
(m, 1H, H-11), 4.21 (s, 3H, 3′-OCH3), 3.93−3.99 (m, 7H, H-11, 2 ×
OCH3), 3.11−3.14 (m, 1H, H-4), 2.78−2.96 (m, 3H, H-2,3,4). HRMS
(ESI) calcd for C35H30N3O8 ([M + H]+), 620.2027; found, 620.2015.
Biological Assay. The insecticidal activity of 1−8, 9a−c and 9e−j,
10a−j, and 10g′ against the pre-third-instar larvae of oriental
armyworm, M. separata (Walker), was assessed by leaf-dipping
method, as described previously.26 For each compound, 30 larvae
(10 larvae per group) were used. Acetone solutions of compounds 1−
8, 9a−c, 9e−j, 10a−j, 10g′, and toosendanin (used as a positive
control) were prepared at a concentration of 1 mg/mL. Meanwhile,
the acetone solution of dibenzo[a,c]phenazine (12, mp = 226−228 °C
(literature, 224.8−225.7 °C)31) at a concentration of 1 mg/mL was
used as a control. Fresh wheat leaves were dipped into the
corresponding solution for 3 s and then taken out and dried in a
room. Leaves treated with acetone alone were used as a blank control
group. Several treated leaves were kept in each dish, where every 10
larvae were raised. If the treated leaves were consumed, additional
treated leaves were added to the dish. After 48 h, untreated fresh leaves
were added to all dishes until adult emergence. The experiment was
carried out at 25 2 °C and relative humidity (RH) 65−80% and on a
12 h/12 h light/dark photoperiod. The insecticidal activity of the
tested compounds against the pre-third-instar larvae of M. separata was
calculated by using the formula
Figure 2. X-ray crystal structure of 6.
optical rotation, and mp. Crystallographic data (excluding
structure factors) for the structure of 6 have been deposited
with the Cambridge Crystallographic Data Centre as
supplementary publication CCDC 908384. Copies of the data
can be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK [fax, +44 (0)1223
336033; e-mail, deposit@ccdc.cam.ac.uk].
corrected mortality rate (%) = (T − C) × 100/(100% − C)
Insecticidal Activity. The insecticidal activity of 1−8, 9a−
c, 9e−j, 10a−j, and 10g′ against the pre-third-instar larvae of
M. separata, tested by the leaf-dipping method at a
concentration of 1 mg/mL, was expressed as mortality rates.
As indicated in Table 1, the corresponding mortality rates
caused by these compounds after 35 days were generally higher
than those after 10 and 20 days. That is, these compounds as
opposed to other quick-acting conventional neurotoxic
insecticides such as organophosphates, carbamates, and
pyrethroids, showed delayed insecticidal activity.26−28 In the
meantime, the symptoms of the tested M. separata were also
characterized in the same way as in our previous papers.26−28
Due to feeding too much treated leaves during the first 48 h,
some larvae died slowly with slim and wrinkled bodies during
the larval period (Figure 3). On the other hand, many larvae of
the treated groups molted to malformed pupae and died during
the stage of pupation (Figure 4). Malformed moths with
imperfect wings also appeared in the treated groups (Figure 5).
On the basis of the above-mentioned symptoms, the derivatives
likely exhibited an antimolting hormone effect.
Compounds 4, 7, 9c, 9f, 9g, 9i, 9j, and 10c exhibited
insecticidal activity equal to or higher than that of toosendanin.
Especially 9i displayed the best promising insecticidal activity
with a final mortality rate of 72.4%. In addition, preliminary
structure−activity relationships were studied. When compound
2 was oxidized to the quinone 3, the final mortality rate of 3
was decreased to 24.1% (41.4% for 2). Whereas 3 reacting with
1,2-phenylenediamine gave the phenazine 4, the final mortality
rate of 4 was increased to 55.2%. In general, introduction of the
acylamino groups at the C-9′ position of 4 could afford more
potent compounds than those containing the same ones at the
C-10′ position. As shown in Table 1, the insecticidal activity of
where T is the mortality rate in the treated group expressed as a
percentage and C is the mortality rate in the untreated group expressed
as a percentage.
RESULTS AND DISCUSSION
■
Synthesis. A series of new phenazine derivatives of 4-
deoxypodophyllotoxin (9a−c, 9e−j, 10a−j, and 10g′) modified
in the E-ring were synthesized as shown in Scheme 1. First,
podophyllotoxin (1) was smoothly transformed to 4-deoxy-
podophyllotoxin (2) in the presence of 10% palladium/
carbon.29 By treatment of 2 with concentrated nitric acid,
4′,5′-didemethoxy-4′,5′-dioxodeoxypodophyllotoxin (3) was
obtained in 73% yield.32 Then 3 rapidly reacted with 1,2-
phenylenediamine to give the phenazine derivative 4.32 When 3
reacted with 4-nitro-1,2-phenylenediamine for 5 h, two
regioisomers, 5 and 6, were afforded in 29 and 59% yields,
respectively. Additionally, to confirm the absolute three-
dimensional configuration of 5 and 6, a single crystal of 6
was obtained and its steric structure was illustrated by X-ray
crystallography (Figure 2). It obviously demonstrated that the
nitro group of 6 was unambiguously at the C-10′ position and
its trans lactone was retained, so the nitro group of the other
isomer, 5, was at the C-9′ position. Interestingly, it was
noteworthy that two nitrogen atoms of the phenazine fragment
of 6 were obviously at the C-4′ and C-5′ positions; therefore,
the o-quinone moiety of 3 should also be at the C-4′ and C-5′
positions. Subsequently, reduction of 5 or 6 in the presence of
SnCl2 easily afforded 7 or 8. Finally, 9a−c, 9e−j, 10a−j, and
10g′ were obtained by reaction of 7 or 8 with acyl chlorides
(11a−j) in the presence of Et3N. The structures of all target
compounds were well characterized by 1H NMR, HRMS,
E
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Journal of Agricultural and Food Chemistry
Article
Table 1. Insecticidal Activity of Some Deoxypodo-
phyllotoxin-Based Phenazine Derivatives against M. separata
on Leaves Treated with a Concentration of 1 mg/mL
corrected mortality rate (%)
compd
10 days
20 days
35 days
1
13.3 4.7
20.0 8.2
6.7 9.4
24.1 4.7
34.5 4.7
41.4 4.7
24.1 9.4
55.2 12.5
31.0 12.5
20.7 12.5
55.2 4.7
34.5 4.7
44.8 9.4
48.3 8.2
62.1 4.7
41.4 4.7
62.1 9.4
55.2 4.7
44.8 4.7
72.4 4.7
51.7 9.4
34.5 4.7
2
27.6
0
3
13.8 4.7
17.2 8.2
24.1 4.7
13.8 4.7
34.5 4.7
20.7 4.7
24.1 4.7
10.3 4.7
24.1 9.4
20.7 9.4
34.5 9.4
20.7 4.7
17.2 8.2
31.0 9.4
27.6 8.2
27.6 8.2
4
6.7 9.4
5
16.7 4.7
13.3 4.7
13.3 4.7
13.3 4.7
13.3 9.4
6.7 9.4
6
7
8
9a
9b
9c
9e
9f
9g
9h
9i
9j
13.3 4.7
10.0 8.2
13.3 9.4
13.3 4.7
13.3 4.7
26.7 4.7
16.7 9.4
16.7 4.7
3.3 4.7
Figure 4. Representative malformed pupae pictures of 4, 9b, 9g, 9h,
and 10c during the pupation period (CK, blank control group).
10a
10b
0
4.7
17.2
0
10c
13.3 9.4
13.3 4.7
13.3 9.4
13.3 4.7
13.3 4.7
16.7 4.7
3.3 4.7
31.0 9.4
24.1 9.4
31.0 12.5
24.1 4.7
17.2 8.2
20.7 9.4
24.1 4.7
58.6 8.2
31.0 12.5
34.5 9.4
31.0 4.7
27.6 8.2
10d
10e
10f
10g
10g′
10h
10i
27.6
48.3 8.2
37.9
0
3.3 4.7
6.9
20.7 4.7
−3.4
34.5 4.7
0
0
10j
23.3 4.7
44.8 9.4
51.7 4.7
48.3 8.2
12
0
0
0
toosendanin
26.7 4.7
Figure 5. Representative malformed moth pictures of 4, 9i, 9j, 10c,
and 10h during the emergence period (CK, blank control group).
and 34.5%, respectively; however, the final mortality rate of 10c
(R = Et) was 58.6%. Interestingly, when the methoxy group
was introduced at the para position of 9f to give 9i, the final
mortality rate of 9i was increased to 72.4%; on the contrary,
introduction of the methoxy group at the meta position of 9f
afforded 9h, the final mortality rate of which was decreased to
44.8%. On the other hand, the insecticidal activity of the
prepared derivatives was different from that of phenazine 12.
No larvae died for the group treated by compound 12.
In conclusion, a series of new deoxypodophyllotoxin-based
phenazine analogues modified in their E-ring were prepared
and tested for their insecticidal activity against the pre-third-
instar larvae of M. separata in vivo at a concentration of 1 mg/
mL. Of all the derivatives, compound 9i, containing p-
methoxybenzoylamino at the C-9′ position of the deoxypodo-
phyllotoxin-based phenazine fragment, exhibited a more
promising insecticidal activity than toosendanin. The deriva-
tives likely displayed an antimolting hormone effect. This
suggested that the proper length of the side chain of
alkylacylamino was important for their insecticidal activity,
and introduction of the acylamino groups at the C-9′ position
of deoxypodophyllotoxin-based phenazine fragment generally
afforded more potent compounds than those containing the
same ones at the C-10′ position. Hence, other substituents
could be introduced at the C-9′ position of the deoxypodo-
Figure 3. Representative abnormal larvae pictures of 4, 9c, and 10d
during the larval period (CK, blank control group).
5, 7, 9a−c, and 9e−j was usually more pronounced than that of
6, 8, 10a−c, and 10e−j (except 9h and 10h). The proper
length of the side chain of alkylacylamino was essential for their
insecticidal activity. For example, the final mortality rates of 9a
(R = Me), 9b (R = CH2Cl), and 9e (R = n-hexyl) were only
44.8, 48.3, and 41.4%, respectively, whereas the final mortality
rate of 9c (R = Et) was 62.1%. Similarly, the final mortality
rates of 10a (R = Me), 10b (R = CH2Cl), 10d (R =
isopropenyl), and 10e (R = n-hexyl) were only 34.5, 17.2, 31,
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AUTHOR INFORMATION
■
Corresponding Author
*(H.X.) Phone: +86(0)29-87091952. Fax: +86(0)29-
87091952. E-mail: orgxuhui@nwsuaf.edu.cn.
Funding
The present research was supported by National Natural
Science Foundation of China (No. 31071737) and Special
Funds of Central Colleges Basic Scientific Research Operating
Expenses (YN2013008).
Notes
The authors declare no competing financial interest.
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