Studies on synthesis and biological activity of oxidative aglafolin derivatives

Article abstract of DOI:10.1002/jhet.1842

The synthesis of the key intermediate of rocaglamide, oxidative aglafolin, was studied, and its diastereoisomers were obtained. The amination of oxidative aglafolin was also investigated, affording amino derivatives. The preliminary bioassay results indic

Full text of DOI:10.1002/jhet.1842

1430
Studies on Synthesis and Biological Activity of Oxidative Aglafolin
Derivatives
Vol 51
b
a
a
a
a
a
a
a
*
Xianyou Wang, Zhuoqun Xie, Bin Fu, Nan Li, Mingan Wang, Yongqiang Ma, Fengpei Du, Yanjun Xu,
a
*
and Zhaohai Qin
aCollege of Science, China Agricultural University, Beijing, 100193, China
bCollege of Quality and Technical Supervision, Hebei University, Baoding, 071002, China
*
E-mail: fubinchem@cau.edu.cn; qinshaohai@263.net
Received February 22, 2012
DOI 10.1002/jhet.1842
Published online 25 March 2014 in Wiley Online Library (wileyonlinelibrary.com).
The synthesis of the key intermediate of rocaglamide, oxidative aglafolin, was studied, and its diastereoisomers
were obtained. The amination of oxidative aglafolin was also investigated, affording amino derivatives. The
preliminary bioassay results indicate that these new aglafolin derivatives showed certain degree of insecticidal
and repellent activity against Plutella xylostella and Laphygma exigua.
J. Heterocyclic Chem., 51, 1430 (2014).
INTRODUCTION
RESULTS AND DISCUSSION
Rocaglamide (Fig. 1), featuring a cyclopenta[b]benzofuran
core, belongs to a class of natural product possessing
diverse biological activity such as insecticidal, antifungal,
and antitumor activity [1]. Because of these features, roca-
glamide can serve as a viable lead for the discovery of new
drugs and agrochemicals.
Oxidative aglafolin (3a) and its isomers were synthe-
sized according to our previously reported method
(Scheme 1) [5]. Two diastereoisomers of 2a (cis) and 2b
(trans) (the ratio of 2.24 to 1) were afforded via Michael
addition of benzylidene malonate to 1 in the presence of
Bu4N+OHꢀ.The structure of 2a had been confirmed by
X-ray diffraction analysis [6]. Subsequently, oxidative
aglafolin 3 was successfully prepared from 2 via intramo-
lecular keto-ester reductive coupling. In this process,
SmI2 was proved to be the best reductive coupling system
after many trials, despite that the Ti3+and Zr3+ were also
used in this reduction reaction [7,8]. Through further opti-
mizing, the solvent and other conditions, four isomers of
oxidative aglafolin 3 were completely obtained, that is,
2a converting into 3a and 3b, 2b converting into 3c and
3d. This result is a little different from our former report;
there are only two diastereoisomers because of the plausi-
ble racemerization of 2-position chiral carbon resulted
from keto-ester equilibrium in compound 3. However,
herein, two couples of diastereoisomers between 3a and
3b, and 3c and 3d were successfully separated (Scheme 1).
With the precursors of rocaglamide in hand, the
derivatization of b-keto ester 3 was investigated next.
The amination of oxidative aglafolin 3a with various amine
compounds was studied (Scheme 2). When 3a was reacted
with hydrazine hydrate, the product pyrazolinone 4 with a
fused five-membered heterocycle was given in good yield.
This result can be attributed to the double condensation
In most rocaglamide derivatives, the phenyl groups at
positions 3 and 3a always occupy a cis orientation with
respect to the hydroxyl group at position 8b, whereas
the substituents at positions 1 and 2 are in trans with
respect to the hydroxyl at position 8b. Because of the
shortage of analogs with varied configurations, it is diffi-
cult to evaluate the relationship between the biological
activities and different configurations. On the other hand,
it appears that the 1-position carbon atom has little influ-
ence on the insecticidal activity. For example, compound
8 shows excellent insecticidal activity against littoralis
[2]. Moreover, aglaiastatin and dehydro-aglaiastatin with
cyclopentane fused other cycle and show almost the
same good insecticidal activity, indicating that the sub-
stituents at 1-position and 2-position have little effect
on the insecticidal activity, which has been ever
regarded as the major site for structural modification
[3,4]. Owing to oxidative aglafolin containing b-keto
ester unit, further structural modification and derivatiza-
tion become much more easily. We have chosen oxidative
aglafolin as the key intermediate for derivatization and
structure activity relationship analysis.
© 2014 HeteroCorporation

September 2014
Studies on Synthesis and Biological Activity of Oxidative Aglafolin Derivatives
1431
HO
that occurred. Condensation of benzene hydrazine with 3a
afforded only the expected hydrazone 5 in good yield. To
our surprise, the reaction of 3a with hydroxylamine
hydrochloride was more complex. Despite many trials that
were attempted under various bases, such as Na2CO3,
triethylamine, pyridine, and NaOH, the expected product
7 was not obtained even after heating at reflux. However,
without the addition of base, the reaction mixture was
directly refluxed in anhydrous methanol; the unexpected
product 6 with a three-membered spiro-ring containing
N-O bond was obtained in 61% yield. Its structure was
MeO
8
CONMe2
HO
8a
1
2
3
8b
7
3a
6
O
4a
MeO
5
OMe
Figure 1 Rocaglamide
Scheme 1
OMe
HO
O
OMe
O
COOMe
COOMe
OMe
COOMe
O
i
ii
O
O
MeO
O
MeO
MeO
OMe
OMe
OMe
2
3
1
Reaction condition: i.PhCH=CHCO2Me, Bu4N+OH-; ii. SmI2
OMe
HO
O
OMe
HO
O
OMe
HO
O
OMe
HO
O
COOMe
Ph
COOMe
Ph
COOMe
Ph
COOMe
Ph
O
O
O
MeO
O
MeO
MeO
MeO
OMe
OMe
OMe
OMe
3a
3b
3c
3d
Scheme 2
H
N
HN Ph
OMe
HO
OMe
HO
N
N
OMe
HO
O
O
COOMe
COOMe
i
ii
O
O
O
MeO
MeO
MeO
OMe
OMe
OMe
3a
5
4
iii
iii
OH
OMe
HO
N
Me
N
OMe
COOMe
O
HO
COOMe
O
MeO
O
MeO
R
OMe
7 R=H; 8 R=OMe
OMe
6
Reaction condition: i. NH2NH2.HCl; ii) PhNH2NH2 ; iii) NH2OH.HCl
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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X. Wang, Z. Xie, B. Fu, N. Li, M. Wang, Y. Ma, F. Du, Y. Xu, and Z. Qin
Vol 51
Table 1
Insecticidal activities of the title compounds (% mortality).
Plutella xylostella
Laphygma exigua
Concentration
No.
(mg/mL)
2 days
3 days
5 days
2 days
3 days
5 days
3a
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
5.0
60.0
5.0
60.0
0
45.0
25.0
55.0
5.0
10.0
5.0
20.0
10.0
55.0
10.0
25.0
—
47.4
73.7
57.9
89.5
57.9
57.9
52.6
100.0
52.6
73.7
63.2
68.4
68.4
100.0
100.0
100.0
15.0
30.0
0
40.0
45.0
5.0
10.0
25.0
60.0
5.0
10.0
15.0
15.0
5.0
10.0
0
70.0
80.0
75.0
75.0
70.0
100.0
15.0
100.0
50.0
75.0
25.0
60.0
68.4
42.1
73.7
10.5
52.6
—
57.9
—
26.3
—
3b
0
3c
20.0
15.0
0
0
0
5.0
0
10.0
0
5.0
30.0
40.0
3d
4
5
36.8
36.8
73.7
5.3
6
0
5.0
55.0
50.0
50.0
100.0
100.0
Azadirachtin
42.1
confirmed by 1H NMR, 13C NMR, IR, and HRMS. Similar
products were not observed when methanol was used in
place of ethanol or benzyl alcohol. The mechanism for this
reaction is under further investigation.
and corresponding derivatives were investigated. Our
research demonstrated that the configuration of oxidative
aglafolin exhibited different degree of impact on the
insecticidal and repellent activity. Further studies are in
progress in our laboratory.
Finally, we evaluated the insecticidal and repellent activ-
ity of all the newly synthesized compounds and compared
them with azadirachtin as shown in Tables 1 and 2. The
biological activities of different isomers of oxidative agla-
folin 3 showed somewhat differences from the bioassay
EXPERIMENTAL
data. Especially, under the concentration of 200 mg mLꢀ1
,
Chemistry.
Melting points were measured with an XT-4
the compound 3d displayed 100% of insecticidal activity
against Plutella xylostella and Laphygma exigua. In the
test of repellency, 3c and 3d showed almost the same
repellent as that of azadirachtin, whereas the amino- deriva-
tives 4, 5, and 6 have low repellent activity against L. exigua.
These results indicated the change of the configuration at
2-position and 3-position of oxidative aglafolin that had
an important effect on the insecticidal and repellent activity.
In summary, oxidative aglafolin and its isomers were pre-
pared; further derivatization with various amines was studied.
In addition, the biological activity of its stereo-isomers
melting point apparatus (Beijing Tech Instruments Co., Beijing,
China) and are uncorrected. NMR spectra were recorded with a
Bruker Avance DPX300 spectrometer (Bruker, Swiss) with
tetramethylsilane as the internal standard. Mass spectra were
obtained with a VG-ZAB-HS mass spectrometer (Micromass Co.
UK). Solvents used were purified and dried by standard procedures.
Compound 1 was synthesized according to literature procedure [5].
Synthesis of 2. Under a N2 atmosphere, to a solution of 1
(3.0 g, 10 mmol) in anhydrous THF (100 mL) was added a
solution of Triton B (40% in CH3OH, 0.30 mL) and a solution
of dimethyl benzylidene malonate (3.2 g, 14.5 mmol) in THF
(30 mL) by syringe. After stirring for 3 h at 60ꢁC, the solvent
was removed in vacuo and to the residue was added a solution
of HCl (1 M, 30 mL), and this solution was extracted with
CH2Cl2 (3 ꢂ 30 mL). The combined organic phase was washed
with brine (2 ꢂ 30 mL), dried with Na2SO4, and concentrated.
The crude product was separated by silica-gel column
chromatography (petroleum ether/ethyl acetate, 1:1) to afford a
couple of diastereoisomers 2a and 2b.
Table 2
Repellency of the title compounds against Laphygma exigua.
No.
Repellency (%)
Azadirachtin
50.0
25.0
20.0
50.0
45.0
30.0
0
3a
3b
3c
3d
4
2a (Cis), 1.82 g, 35.0% yield, mp: 169–170ꢁC. 1H NMR (CDCl3):
d 3.17 (s, 3H), 3.27 (s, 3H), 3.65 (s, 3H), 3.77 (s, 3H), 3.86 (s, 3H),
4.33 (d, 1H, J = 10.8Hz), 4.53 (d, 1H, J = 10.8 Hz), 5.78 (d, 1H,
J = 1.8 Hz), 6.27 (d, 1H, J = 1.8 Hz), 6.82–6.85 (m, 2H), 7.05–7.13
(m, 3H,), 7.31–7.34 (m, 2H), 7.69–7.76 (m, 2H). 13C NMR d:
194.3, 174.0, 169.5, 167.6, 167.5, 159.6, 159.1, 135.4, 130.0,
127.7, 127.5, 127.3, 127.0, 113.4, 103.7, 92.8, 92.3, 88.5, 55.8,
5
6
0
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2014
Studies on Synthesis and Biological Activity of Oxidative Aglafolin Derivatives
1433
55.7, 55.2, 54.1, 52.2, 52.1, 51.4. IR (cmꢀ1): 2953, 1746, 1707,
1620, 1594, 1510, 1255, 1219, 1156, 1124, 841, 816, 698.
6.16 (s, 1H), 5.96 (d, 1H, J = 1.8 Hz), 6.24 (d, 1H, J = 1.8 Hz),
6.62–6.67 (m, 2H), 7.15–7.24 (m, 3H), 7.29–7.34 (m, 4H).
13C NMR: d 200.7, 170.6, 162.1, 158.9, 156.4, 115.1, 130.9,
129.9, 129.2, 127.7, 127.4, 127.2, 126.4, 113.8, 101.5, 95.5,
92.9, 77.4, 77.0, 76.5, 75.9, 61.4, 55.8, 55.4, 55.2, 53.0, 52.9,
51.5, 50.9. IR (cmꢀ1): 3249, 1739, 1681, 1605, 1384, 1259,
1144, 1095, 812, 708. HRMS m/z: 491.1729 (M + H, Calcd for
2b (Trans): 0.85g, 16.3% yield, mp 168–169ꢁC. 1H NMR
(CDCl3): d 3.29 (s, 3H), 3.54 (s, 3H), 3.67 (s, 3H), 3.84 (s, 3H),
3.88 (s, 3H), 4.21 (d, 1H, J = 9.3Hz), 4.47 (d, 1H, J = 9.3 Hz),
5.97 (d, 1H, J = 1.8Hz ), 6.27 (d, 1H, J = 1.8Hz), 6.63–6.67 (m,
2H), 7.04–7.11(m, 3H), 7.17–7.21 (m, 2H), 7.36–7.42 (m, 2H).
13C NMR: d 194.5, 174.0, 169.8, 167.8, 167.6, 159.2, 159.1,
136.2, 130.2, 128.4, 127.4, 127.0, 126.9, 113.2, 104.3, 93.2, 92.7,
88.8, 55.9, 55.1, 53.4, 52.5, 52.1, 52.0. IR (cmꢀ1): 2953, 2841,
1785, 1623, 1592, 1511, 1254, 1221, 1159, 1032, 927, 818, 698.
Synthesis of 3. (1) 3a and 3b: To the reactant of metal Sm
(1.20 g, 8.0 mmol) in a flame-dried, three-necked round-bottom
flask (100 mL) equipped with a stir bar, septum, and nitrogen
inlet was added a solution of C2H4I2 (1.10 g, 3.9 mmol) in THF
(7 mL). After stirring for 1 h, the solution changed to blue, and
the reaction was continued for 3 h under ultrasound irradiation.
Anhydrous benzene (20 mL) was then added, and the reaction
was continued for an additional 2 h. A solution of 2a (1.02 g,
1.96 mmol) in benzene (100 mL) was added, and the reaction
was allowed to proceed for 10 h under ultrasound irradiation.
The reaction was quenched with the addition of HCl (1 M,
20 mL), and the solution was extracted with CH2Cl2
(3 ꢂ 30 mL). The combined organic phase was washed with
brine (2 ꢂ 20 mL), dried with anhydrous Na2SO4, and
concentrated. The crude product was purified by silica-gel column
chromatography (petroleum ether/EtOAc, 2:3) to afford a couple of
C
28H27O8, 491.1738).
Synthesis of 4.
anhydrous methanol (10 mL) was added
To a solution of 3a(0.1 g, 0.20 mmol) in
solution of
a
NH2NH2.H2O (0.013 g, 0.22 mmol) in methanol (2 mL). The
mixture was refluxed for 6 h and left to stand at room
temperature overnight and was then filtered to afford colorless
solid 0.078 g (82.6%), mp: 280–282ꢁC.1H NMR (CDCl3) d:
3.49 (s, 1H), 3.66 (s, 3H), 3.81 (s, 3H), 3.84 (s, 3H), 4.94
(s, 1H, ), 6.07 (d, 1H, J = 1.9 Hz), 6.31 (d, 1H, J = 1.9 Hz),
6.58–6.61 (m, 2H), 7.03–7.28 (m, 8H,). 13C NMR d: 164.1,
160.7, 158.8, 157.4, 137.5, 128.7, 127.8, 127.7, 126.8, 126.4,
113.0, 112.8, 107.0, 92.6, 89.3, 83.7, 64.3, 55.7, 55.0, 54.9.
IR (cmꢀ1): 3189, 1609, 1514, 1456, 1252, 1150, 1113, 1037,
1019, 811, 764, 700. HRMS m/z: 473.17031 (M+ H, Calcd for
C27H25N2O6, 473.17071).
Synthesis of 5.
To a solution of 3a (0.1 g, 0.20 mmol) in
anhydrous methanol (10 mL) was added a solution of phenyl
hydrazine (0.023g, 0.22 mmol) in methanol (3 mL). The mixture
was refluxed for 10h and left to stand at room temperature
overnight and was then filtered to afford red solid 0.07 g (60.3%
1
yield), mp 210–212ꢁC. H NMR (CDCl3) d: 3.66 (s, 3H), 3.70
diastereoisomers 3a and 3b.
1
3a: 0.27 g, yield: 28.6%. mp 161–162ꢁC. H NMR (CDCl3):
(s, 3H), 3.75 (s, 3H), 3.86 (s, 3H), 4.00 (d, 1H, J = 12.2 Hz), 4.35
(d, 1H, J = 12.2Hz ), 6.10 (d, 1H, J = 1.9Hz), 6.34 (d, 1H,
J = 1.9 Hz), 6.65–6.68 (m, 2H), 6.94–7.24 (m, 11H,), 7.26–7.34
(m, 2H). 13C NMR: d 171.8, 164.3, 160.4, 159.1, 157.5, 145.2,
138.0, 136.0, 129.2, 128.1, 127.9, 126.9, 125.7, 119.6, 113.5,
112.3, 101.4, 92.9, 90.2, 86.8, 56.1, 55.7, 55.1, 53.0, 52.4, 51.1.
IR (cmꢀ1): 3435, 2937, 1738, 1600, 1516, 1384, 1253, 1151,
1019, 805, 749, 696. HRMS m/z: 581.22825 (M+ H, Calcd for
C34H33N2O7, 581.22823).
d 3.04 (s, 1H), 3.66 (s, 3H), 3.71 (s, 3H), 3.81 (s, 3H), 3.85
(s, 3H), 4.06 (d, 1H, J = 13.2 Hz), 4.24 (d, 1H, J = 13.2 Hz),
6.10 (d, 1H, J = 1.8 Hz), 6.35 (d, 1H, J = 1.8 Hz), 6.66–6.70
(m, 2H), 6.89–6.97 (m, 4H), 7.08–7.12 (m, 3H). 13C NMR: d
203.3, 167.2, 164.9, 161.0, 158.9, 158.6, 135.4, 129.1, 128.0,
127.9, 127.7, 127.1, 125.4, 113.2, 112.2, 106.1, 99.3, 92.9,
89.9, 88.5, 56.4, 55.7, 55.6, 55.1, 55.0, 52.9, 52.0, 51.5. IR
(cmꢀ1): 3420, 2980, 1760, 1720, 1620, 1600, 1520, 1480,
1260, 1230, 1180, 1160, 1120, 1100, 1020, 820, 710. HRMS
m/z: 491.1685 (M + H, Calcd for C28H27O8, 491.1738). 3b:
Synthesis of 6.
To a solution of 3a (0.1 g, 0.20 mmol)
in anhydrous methanol (10 mL) was added a solution of
hydroxylamine hydrochloride (0.017 g, 0.25 mmol) in methanol
(2 mL). The mixture was refluxed for 12 h, and then the solvent
was evaporated and separated by column chromatography
(petroleum/ethyl acetate as eluent) to afford red solid 0.07 g
(60.3% yield), mp 203–205ꢁC.
1H NMR (CDCl3) d: 2.98 (s, 3H), 3.51 (s, 3H), 3.74 (s, 3H),
3.87 (s, 3H), 3.80 (d, 1H, J = 13.2 Hz), 4.20 (d, 1H, J = 13.2 Hz ),
6.19 (d, 1H, J = 1.9 Hz), 6.32 (d, 1H, J = 1.9 Hz), 6.67–6.70
(m, 2H), 6.82–7.10 (m, 7H,). 13C NMR d: 171.0, 164.4, 161.1,
160.0, 158.8, 157.3, 134.9, 128.3, 128.0, 127.8, 127.7, 127.1,
126.2, 113.1, 103.5, 99.0, 93.0, 91.4, 89.4, 71.7, 64.3, 55.9,
55.8, 55.7, 55.6, 52.5, 52.3, 47.2. IR (cmꢀ1): 3205, 2948,
1736, 1613, 1598, 1518, 1384, 1252, 1116, 1046, 974, 838,
814, 700. HRMS m/z: 520.19624 (M + H, Calcd for
C29H30NO8, 520.19659); 542.17786 (M + Na, Calcd for
C29H29N2O8Na, 542.17854).
1
0.10 g, yield: 10.5%. mp 196–198ꢁC. H NMR(CDCl3): d 3.17
(s, 1H), 3.67 (s, 3H), 3.72 (s, 3H), 3.80 (s, 3H), 3.81 (s, 3H),
4.93 (s, 1H), 5.60 (s, 1H), 6.10 (d, 1H, J = 1.8 Hz), 6.35
(d, 1H, J = 1.8 Hz), 6.65–6.68 (m, 2H), 7.15–7.24 (m, 3H),
7.29–7.35 (m, 4H). 13C NMR: d 200.8, 170.5, 162.1, 158.9,
156.4, 130.4, 129.2, 129.0, 127.6, 127.4, 127.2, 126.4, 113.8,
101.5, 95.6, 92.9, 77.4, 77.0, 76.5, 75.9, 61.4, 55.8, 55.4, 55.2,
53.0, 52.9, 51.6, 50.9. IR (cmꢀ1): 3429, 1739, 1682, 1604, 1384,
1259, 1201, 1144, 1096, 852, 707. HRMS m/z: 491.1742 (M+ H,
Calcd for C28H27O8, 491.1738).
(2) 3c and 3d: Following the same procedure as previously
mentioned, starting from 2b to prepare 3c and 3d.
1
3c: 0.25 g, yield: 26.2%, mp 95–96ꢁC. H NMR (CDCl3): d
2.95 (s, 1H), 3.42 (s, 3H), 3.49 (s, 3H), 3.61 (s, 3H), 3.63
(s, 3H), 4.08 (d, 1H, J = 13.0 Hz), 4.16 (d, 1H, J = 13.0 Hz),
5.30 (d, 1H, J = 1.8 Hz), 5.60 (d, 1H, J = 1.8 Hz), 6.63–6.67
(m, 2H), 6.90–7.01 (m, 4H), 7.08–7.65 (m, 3H). IR (cmꢀ1):
3400, 2980, 1770, 1720, 1600, 1500, 1480, 1430, 1420, 1350,
1260, 1220, 1150, 1120, 820, 710. HRMS m/z: 491.1735
(M + H, Calcd for C28H27O8, 491.1738). 3d, 0.12 g, yield:
BIOASSAY
1
12.5%. mp 163–164ꢁC. H NMR (CDCl3): d 3.17(s, 1H), 3.68
Azadirachtin and the newly synthesized compounds
were individually dissolved in chloroform (1% M/V) and
(s, 3H), 3.71 (s, 3H), 3.80 (s, 3H), 3.81 (s, 3H), 4.95 (s, 1H),
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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X. Wang, Z. Xie, B. Fu, N. Li, M. Wang, Y. Ma, F. Du, Y. Xu, and Z. Qin
Vol 51
then diluted with water containing 0.02% emulsifier and
0.05% Triton X-100 to the tested concentrations.
was placed in the hole and covered with cling film. Ten
insects were used at every concentration; all experiments
were kept at (27 ꢃ 1)ꢁC and were replicated six times.
The mortality of insects was determined after 3 days, and
Abbotts formula was used to correct the mortality relative
to that of negative control. The data was presented in the
form of mean mortality (%).
Insect repellency. The leaf of Brassica chinensis Linn.
was washed, dried by airing, and cut as a ꢀ70-mm round
disk, which was then divided into two halves. One half of
the disk was daubed with 0.2 mL tested agent prepared
earlier on both sides. The other half of the disk was a
control, which was only daubed with water containing
emulsifier and Triton X-100. After being dried by airing,
the disks were put in an ꢀ85-mm culture dish and 10 third
instar larvae of P. xylostella (Linnaeus) were put on the
half leaf disk containing insecticide, covered with cling
film, and kept at (27 ꢃ 1)ꢁC for 24 h. Experiments were
replicated three times at every concentration. The contents
of worm at each treated or control diet was counted, and
the repellency (%) was calculated by the following formula:
Acknowledgments. We would like to thank the National Natural
Science Foundation of China (No. 20772151) and Hebei
University Young Foundation (2010Q13) for financial support.
We are most grateful to Professor Rui Changhui (Institute of
Plant Protection, Chinese Academy of Agriculture Science) for
his kind assistance with the bioassay study.
Repellency ð%Þ ¼ ðC ꢀ EÞ=T ꢂ 100%
REFERENCES AND NOTES
where C is the insect numbers in the negative control half
of the leaf disk, E is the insect numbers in the treated half
of disk, and T is the number of total insects. C, E, and T
were the mean data of the three replicates.
Insecticidal activity. The third instar larvae of Pieris
rapae Linnaeus, Brassica napus Linn., and second instar
larvae of L. exigua (Hubner) were treated with Potter’s
method under 200 and 100 mg mLꢀ1. The leaf of B.
chinensis Linn. was cut to ꢀ15-mm round disks. These
leaf disks were immersed in sample solution for 10 s,
dried by airing, and then put in a testing box with ten
holes, which in every hole a piece of leaf disk was
needed. The third instar larva of Helicoverpa armigera
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet