Stereoselective synthesis of 4α-acyloxy-2α/β- bromopodophyllotoxin derivatives as insecticidal agents

Article abstract of DOI:10.1016/j.tet.2012.10.073

To find new natural products-based insecticidal agents, and substantially extend our previous work, we have designed and stereoselectively synthesized 4α-acyloxy-2α/β-bromopodophyllotoxin derivatives from podophyllotoxin. Interestingly, 4α-acyloxy-2α- bro

Full text of DOI:10.1016/j.tet.2012.10.073

Tetrahedron 69 (2013) 774e781
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Stereoselective synthesis of 4
a
-acyloxy-2
a/
b-bromopodophyllotoxin
derivatives as insecticidal agents
*
Yong Guo, Lingling Fan, Juanjuan Wang, Chun Yang, Huan Qu, Hui Xu
Laboratory of Pharmaceutical Design and Synthesis, College of Sciences, Northwest A&F University, Yangling 712100, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 August 2012
Received in revised form 17 October 2012
Accepted 26 October 2012
Available online 1 November 2012
To find new natural products-based insecticidal agents, and substantially extend our previous work, we
have designed and stereoselectively synthesized 4
a-acyloxy-2a/b-bromopodophyllotoxin derivatives
from podophyllotoxin. Interestingly, 4 -acyloxy-2 -bromopicropodophyllotoxins were easily converted
a
a
to a more rigid compound 14 by an intramolecular FriedeleCrafts alkylation reaction in the presence of
BF3$Et2O when the reaction time was prolonged to 4e18 h. Compounds 5g, 6h, 6i, and 14 displayed the
more promising and pronounced insecticidal activity than toosendanin, a commercial insecticide derived
from Melia azedarach, against the pre-third-instar larvae of Mythimna separata.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Podophyllotoxin
Botanical insecticides
4a-Acyloxy-2-bromopodophyllotoxin
FriedeleCrafts alkylation
Insecticidal activity
1. Introduction
yield.16
anylpicropodophyllotoxin (9) and 2
Two
stereoisomers,
2
a
b
-bromo-4-O-tetrahydropyr-
-bromo-4-O-tetrahydropyr-
Podophyllotoxin (1, Fig. 1), a naturally occurring aryltetralin
lignan, besides its use as the lead-compound for the preparation of
potent anticancer drugs, such as etoposide, teniposide and
etopophos,1e6 has also received much research attention for its
interesting insecticidal and antifungal activities.7e13 More recently,
anylpodophyllotoxin (10), were prepared by treatment of 7 with
lithium diisopropylamide (LDA) at ꢀ78 ꢁC in dry THF, via the
intermediate 8, followed by reaction with Br2. Then hydrolysis of
the THP group of 9 and 10 afforded 2
(11) and 2
-bromopodophyllotoxin (12), respectively.15,17
Secondly, as shown in Scheme 2, 4 -acyloxy-2 -bromopicro-
a-bromopicropodophyllotoxin
b
we have studied stereoselective synthesis of 4
podophyllotoxins (2, Fig. 1),14
-alkyloxy-2
phyllotoxins (3, Fig. 1) and 4 -alkyloxy-2 -bromopodophyllotoxins
a
-acyloxy-2
b-chloro-
a
a
4
a
a
-bromopicropodo-
podophyllotoxins (5aei) were smoothly obtained in 52e86% yields
by reaction of 11 with carboxylic acids (13aei) in the presence of
N,N0-diisopropylcarbodiimide (DIC) and 4-dimethylaminopyridine
(DMAP). Similarly, 12 reacted with 13b, 13h, and 13i in the pres-
a
b
(4, Fig. 1),15 and found some compounds showed more potent
insecticidal activity than toosendanin, a commercial insecticide
derived from Melia azedarach. To find new natural products-based
insecticidal agents, and substantially extend our above-mentioned
ence of DIC and DMAP to afford 4
phyllotoxins (6b, 6h, and 6i) in 60e83% yields.
Thirdly, as shown in Scheme 3, when 11 reacted with 13f, 13g or
13i, in the presence of BF3$Et2O for 1e3 h, only 4 -acyloxy-2
bromopicropodophyllotoxins (5f, 5g, and 5i) were obtained in
53e84% yields. On the contrary, the corresponding isomers, 4
acyloxy-2
-bromopodophyllotoxins (50f, 50g, and 50i) were not
a-acyloxy-2b-bromopodo-
work,14,15 we herein further designed four series of 4
a/
b-acyloxy-
2a
/b
-bromopodophyllotoxins (5, 50, 6, and 60, Fig. 1), and in-
a
a-
vestigated their insecticidal activity.
b
-
a
2. Results and discussion
obtained at all. The assignment of configuration of C-4 position of
5aei (bearing cis-lactone) was according to our previous research
results: if J3.4 z2.0 Hz, it indicates that H-3 and H-4 is trans re-
lationship, that is, the substituent on the C-4 position of pic-
Firstly, as depicted in Scheme 1, the 4-hydroxy group of 1 was
protected by a tetrahydropyranyl (THP) group in the presence of
phosphorus oxychloride (POCl3) and dihydropyran (DHP) at rt for
3 h to give 4-O-tetrahydropyranylpodophyllotoxin (7) in a 90%
ropodophyllotoxin is
5aei were 1.5e2.5 Hz, therefore, the substituents on the C-4 po-
sition of 5aei were configuration.
a
configuration.15 The J3.4 values of H-4 of
a
The precise three-dimensional structural information of 5i was
further determined by X-ray crystallography as illustrated in
* Corresponding author. Tel./fax: þ86 29 87091952; e-mail address: orgxuhui@
nwsuaf.edu.cn (H. Xu).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.10.073

Y. Guo et al. / Tetrahedron 69 (2013) 774e781
775
Fig. 1. Chemical structures of podophyllotoxin and its derivatives.
Scheme 1. Synthesis of isomers 11 and 12.
Fig. 2.18 It obviously suggested that 2-bromo and
4-naphthylacetoxy groups of 5i all adopted configuration. Based
upon the X-ray crystallography of 5i, if the acyloxy group on the C-4
position adopted configuration, the big steric effects might be
observed between the lactone (endo-configuration) and the acyloxy
group. Consequently, the acyloxy groups on the C-4 position of 5f,
5g, and 5i adopting configuration was reasonable when 11 reac-
ted with 13f, 13g or 13i, in the presence of BF3$Et2O. Interestingly,
when the reaction time was further prolonged (15 h for 5f, 9 h for
5g, and 10 h for 5i), 5f, 5g, and 5i were entirely converted to the
a
a
b

776
Y. Guo et al. / Tetrahedron 69 (2013) 774e781
Scheme 2. Isomers 11 and 12 reacting with carboxylic acids in the presence of DIC and DMAP.
same by-product 14 via the intermediate 140, in 47e57% yields by
an intramolecular FriedeleCrafts (FC) alkylation reaction, and its
configuration was confirmed by X-ray crystallography.15 Mean-
while, 11 reacting with other carboxylic acids in the presence of
BF3$Et2O for prolonged time was also examined. As shown in Table
1, after 4e18 h, the intermediates 5 were completely disappeared
and the same by-product 14 was obtained in 30e57% yields.
larval period. In the meantime, many larvae of the treated groups
moulted to malformed pupae, and died during the stage of pupa-
tion. Malformed moths with imperfect wings were also appeared in
the treated groups. As described in Table 2, 5g, 6h, 6i, 10, and 14
exhibited more pronounced insecticidal activity than or compara-
ble to toosendanin. Especially 6h and 6i displayed the most
promising insecticidal activity. In general, the insecticidal activity of
As anticipated in our previous report for
opodophyllotoxin,14 when 12 reacted with 13i in the presence of
BF3$Et2O, due to steric effects of the C-2 bromine atom, only
-naphthylacetoxy-2 -bromopodophyllotoxin (6i) was stereo-
selectively obtained in a 53% yield, whereas its isomer, 4 -naph-
thylacetoxy-2
-bromopodophyllotoxin (60i), was not obtained
2
b
-chlor-
4
a
-acyloxy-2
of the corresponding 4
dophyllotoxin. Therefore, as described in our previous reports,15 the
trans-lactone and the bromine atom at the C-2 position were also
necessary for -acyloxy-2-bromopodophyllotoxins possessing
good insecticidal activity. For example, to 2 -bromopicropodo-
b
-bromopodophyllotoxins was more potent than that
a
-acyloxy derivatives of 2 -bromopicropo-
a
b
4
a
b
b
b
4a
b
a
(Scheme 3). The assignment of configuration of C-4 position of 6b,
phyllotoxin series, the final mortality rates of 9, 11, 5b, 5h, and 5i
were 45.8%, 41.7%, 33.3%, 45.8%, and 50%, respectively; on the
6h, and 6i (bearing trans-lactone) was based on the Lee’s rule.19 The
C-4
b-substituted compounds have a J3.4 z4.0 Hz due to a cis re-
contrary, to the corresponding 2b-bromopodophyllotoxin series,
lationship between H-3 and H-4. If J3.4 ꢂ10.0 Hz, it indicates that H-3
the final mortality rates of 10, 12, 6b, 6h, and 6i were 54.2%, 45.8%,
41.7%, 62.5%, and 66.7%, respectively. On the other hand, when
and H-4 is trans relationship, and the substituent on the C-4 position
of podophyllotoxin is
H-4of 6i was 9.0 Hz, therefore, the naphthylacetoxygroup on the C-4
position of 6i was configuration. The configuration of 6i was fur-
ther confirmed by X-ray crystallography (Fig. 3),19 and 2-bromo and
4-naphthylacetoxy groups of 6i adopted and configuration, re-
a
configuration.19 For example, the J3.4 value of
compared
-acyloxy-2
less potent insecticidal activity than 4
with
4a-alkyloxy-2-a/b-bromopodophyllotoxins,
4a
a-bromopicropodophyllotoxins generally exhibited
a
a
-alkyloxy-2 -bromopicro-
a
podophyllotoxins; 4
a
-alkyloxy- and 4
a
-acyloxy-2b-bromopodo-
b
a
phyllotoxins both showed the potent insecticidal activity.15 The
aforementioned interesting results will encourage us to further
spectively. However, to 6i, even if the reaction time was further
prolonged to 25 h, the proposed by-product 15 was not monitored.
Finally, the insecticidal activity of 5aei, 6b, 6h, and 6i against
the pre-third-instar larvae of Mythimna separata Walker in vivo was
tested by the leaf-dipping method at the concentration of 1 mg/mL.
Toosendanin, a commercial insecticide derived from M. azedarach,
was used as the positive control. Leaves treated with acetone alone
were used as a blank control group. The symptoms of the tested M.
separata were also characterized by the same way as our previous
reports.14,15 The pupation of the larvae and the adult emergence of
M. separata were inhibited by these compounds, that is, the stage of
the treated groups from the larvae to adulthood of M. separata was
prolonged when comparing with that of the blank control group.
For feeding too much treated leaves during the first 48 h, some
larvae died slowly with the slim and wrinkled bodies during the
prepare other 4a-acyloxy-2b-bromopodophyllotoxin derivatives as
insecticidal agents in future.
3. Conclusions
In summary, we have prepared 4a-acyloxy-2a/b-bromopodo-
phyllotoxin derivatives starting from podophyllotoxin, and
assessed their insecticidal activity against the pre-third-instar lar-
vae of M. separata. It is noteworthy that 4a-acyloxy-2a-bromopi-
cropodophyllotoxins were readily converted to a more rigid
compound 14 by an intramolecular FC alkylation reaction when the
reaction time was prolonged to 4e18 h. Compounds 5g, 6h, 6i, and
14 exhibited the more promising and pronounced insecticidal ac-
tivity as compared with toosendanin. Now, the development of

Y. Guo et al. / Tetrahedron 69 (2013) 774e781
777
Scheme 3. Investigation of 11 or 12 reacting with carboxylic acids in the presence of BF3$Et2O.
new methodology for the preparation of 4
podophyllotoxin derivatives is under study in our lab.
b
-acyloxy-2
a
/
b
-bromo-
preparation of 4-O-tetrahydropyranylpodophyllotoxin (7) was
described in our previous paper.12 Melting points were de-
termined on a digital melting-point apparatus and were un-
corrected. Infrared spectra (IR) were recorded on a Bruker TENSOR
27 spectrometer. Nuclear magnetic resonance spectra (NMR) were
recorded on a Bruker Avance III 500 MHz instrument in CDCl3 (1H
at 500 MHz and 13C at 125 MHz) using tetramethylsilane (TMS) as
the internal standard. High-resolution mass spectra (HRMS) and
electrospray iontrap mass spectrometry (ESI-TRAP-MS) were car-
ried out with APEX II Bruker 4.7T AS instrument and Bruker ESI-
TRAP Esquire 6000 plus mass spectrometry instrument,
respectively.
4. Experimental
4.1. General remarks
All reagents and solvents were of reagent grade or purified
according to standard methods before use. Analytical thin-layer
chromatography (TLC) and preparative thin-layer chromatogra-
phy (PTLC) were performed with silica gel plates using silica gel 60
GF254 (Qingdao Haiyang Chemical Co., Ltd., Qingdao, China). The

778
Y. Guo et al. / Tetrahedron 69 (2013) 774e781
Fig. 3. The X-ray crystal structure of 6i.
Fig. 2. The X-ray crystal structure of 5i.
was allowed to warm slowly from ꢀ78 to 30 ꢁC for 18 h. The solvent
was removed and the residue was diluted by CH2Cl2 (50 mL),
washed by water (25 mL), HCl (0.5 mol/L, 25 mL) and water (25 mL),
dried over anhydrous Na2SO4, concentrated in vacuo, and purified
by silica gel column chromatography to afford 9 and 10.
4.2. Synthesis of 2a-bromo-4-O-tetrahydropyr-
anylpicropodophyllotoxin (9) and 2
dropyranylpodophyllotoxin (10)
b-bromo-4-O-tetrahy-
To a solution of lithium diisopropylamide (LDA, 14 mmol) in dry
tetrahydrofurane (THF, 10 mL) at ꢀ78 ꢁC under N2, a solution of 7
(10 mmol) in dry THF (5 mL) was added dropwise for 10 min. After
adding, the reaction mixture was stirred for 15 min, and then
treated with Br2 (14 mmol) for 30 min. Subsequently, the solution
4.2.1. Compound 9. Yield: 22%, white solid, mp 80e82 ꢁC; [
a
]
20 ꢀ85
D
(c 2.6 mg/mL, CHCl3); IR cmꢀ1: 2923, 1779, 1591, 1483, 1326, 1236,
1168,1124,1028, 959, 867, 751; 1H NMR (500 MHz, CDCl3)
0.6H, H-5), 6.70 (s, 1H, H-20), 6.68 (s, 1H, H-60), 6.65 (s, 0.4H, H-5),
d: 6.86 (s,
Table 1
Investigation of 11 reacting with carboxylic acids to obtain 14 in the presence of BF3$Et2O
Entry
R
Reaction
time (h)
Yield of
14 (%)
1
2
3
4
5
6
7
8
9
(p-Me)Ph
18
10
13
5
18
9
7
4
9
9
57
54
47
57
54
35
46
36
30
31
(m-NO2)Ph
1-Naphthylmethylene
PhCH2
(m-Cl)Ph
(p-Cl)Ph
PhOCH2
Fur-2-yl
Pyridin-3-yl
Pyridin-4-yl
10

Y. Guo et al. / Tetrahedron 69 (2013) 774e781
779
6.57 (s, 0.4H, H-8), 6.53 (s, 0.6H, H-8), 5.90e5.92 (m, 2H, OCH2O),
5.11 (d, J¼2.5 Hz, 0.6H, OCH(CH2)O), 4.77e4.85 (m, 2.4H, H-1, 4,
OCH(CH2)O), 4.57e4.58 (m, 0.4H, H-11), 4.50e4.52 (m, 1H, H-11),
4.45e4.47 (m, 0.6H, H-11), 4.00e4.06 (m, 0.6H, OCH2CH2CH2),
3.94e3.96 (m, 0.4H, OCH2CH2CH2), 3.81e3.84 (m, 9H, 30,40,50-
OCH3), 3.63e3.66 (m, 0.6H, OCH2CH2CH2), 3.56e3.60 (m, 0.4H,
OCH2CH2CH2), 3.36e3.38 (m, 0.4H, H-3), 3.13e3.15 (m, 0.6H, H-3),
Na2SO4, concentrated in vacuo, and purified by silica gel column
chromatography to give 11 in 63% yield as a white solid. Mp
20
92e94 ꢁC; [
a]
ꢀ87 (c 3.0 mg/mL, CHCl3); IR cmꢀ1: 3468, 2936,
D
1775, 1592, 1484, 1326, 1235, 1169, 1122, 1034, 998, 934; 1H NMR
(500 MHz, CDCl3)
d
: 6.81 (s, 2H, H-20, 60), 6.72 (s, 1H, H-5),
6.59e6.61 (m, H, H-8), 5.89e5.91 (m, 2H, OCH2O), 4.91e4.94 (m,
1H, H-4), 4.77e4.80 (m, 1H, H-11), 4.52e4.54 (m, 1H, H-1),
4.44e4.48 (m, 1H, H-11), 3.82 (s, 9H, 30,40,50-OCH3), 3.18e3.21 (m,
1.79e1.82 (m, 2H), 1.56e1.64 (m, 4H); 13C NMR (125 MHz, CDCl3)
d:
19.74, 21.03, 25.13, 25.24, 29.70, 31.05, 31.27, 49.35, 50.94, 51.64,
51.68, 56.24, 56.26, 60.83, 61.84, 62.46, 63.74, 64.94, 74.27, 74.30,
75.36, 80.12, 96.95, 101.40, 101.45, 102.51, 106.94, 107.18, 108.48,
108.73,108.87, 109.75, 126.62, 126.65, 130.33,130.50,135.64,135.72,
137.20, 137.31, 147.80, 147.88, 148.45, 148.59, 152.89, 173.17, 173.64;
MS (ESI-TRAP), m/z (%): 599 ([MþNa]þ, 100), 601 ([MþNa]þ, 96).
1H, H-3); 13C NMR (125 MHz, CDCl3)
d: 51.38, 51.43, 51.91, 56.18,
60.86, 73.76, 73.85, 101.54, 106.78, 108.20, 108.34, 109.16, 128.30,
130.17, 135.70, 136.84, 148.09, 148.61, 152.93, 173.54; MS (ESI-TRAP),
m/z (%): 515 ([MþNa]þ, 100), 517 ([MþNa]þ, 91).
4.4. Synthesis of 2b-bromopicropodophyllotoxin (12)
20
4.2.2. Compound 10. Yield: 10%, white solid, mp 87e89 ꢁC; [
a]
D
ꢀ108 (c 2.4 mg/mL, CHCl3); IR cmꢀ1: 2925, 2850, 1779, 1588, 1504,
A solution of 10 (0.80 mmol) in 12 mL of concd HCleTHF (1:9)
was stirred for 3 h, and then adjusted the pH value to 5 by using of
5% aq Na2CO3. After removing THF, the mixture was extracted with
CH2Cl2 (40 mLꢃ3), and the combined organic phase were washed
by 5% aq Na2CO3 (20 mL) and brine (20 mL), dried over anhydrous
Na2SO4, concentrated in vacuo, and purified by silica gel column
1482, 1324, 1235, 1124, 1031, 978, 932, 867, 769; 1H NMR
(500 MHz, CDCl3) d: 7.22 (s, 0.4H, H-5), 6.91 (s, 0.6H, H-5), 6.50 (s,
1H, H-8), 6.44 (s, 2H, H-20, 60), 5.98e5.99 (m, 2H, OCH2O), 4.99 (d,
J¼9.0 Hz, 0.4H, OCH(CH2)O), 4.87e4.88 (m, 1H, H-4), 4.76e4.77 (m,
0.6H, H-1), 4.71 (d, J¼8.5 Hz, 0.6H, OCH(CH2)O), 4.63e4.64 (m,
0.4H, H-1), 4.58e4.61 (m, 0.6H, H-11), 4.50e4.53 (m, 0.4H, H-11),
4.28e4.30 (m, 0.4H, H-11), 4.19e4.23 (m, 0.6H, H-11), 4.00e4.02
(m, 0.4H, OCH2CH2CH2), 3.91e3.93 (m, 0.6H, OCH2CH2CH2),
3.80e3.81 (m, 3H, 40-OCH3), 3.75 (s, 6H, 30,50-OCH3), 3.51e3.58 (m,
1H, OCH2CH2CH2), 2.82e2.87 (m, 0.4H, H-3), 2.71e2.76 (m, 0.6H,
H-3), 1.87e1.96 (m, 2H), 1.55e1.73 (m, 4H); 13C NMR (125 MHz,
chromatography to give 12 in 60% yield as a white solid. Mp
20
89e91 ꢁC; [
a
]
D
ꢀ113 (c 3.1 mg/mL, CHCl3); IR cmꢀ1: 3504, 2920,
1787, 1590, 1505, 1481, 1327, 1238, 1121, 1058, 1035, 998, 932; 1H
NMR (500 MHz, CDCl3) d: 7.09 (s, 1H, H-5), 6.51 (s, 1H, H-8), 6.42 (s,
2H, H-20, 60), 5.98 (dd, J¼10.5, 1.5 Hz, 2H, OCH2O), 4.90e4.92 (m, 2H,
H-1, 4), 4.55e4.58 (m, 1H, H-11), 4.23e4.26 (m, 1H, H-11), 3.80 (s,
3H, 40-OCH3), 3.75 (s, 6H, 30,50-OCH3), 2.63e2.68 (m, 1H, H-3); 13C
CDCl3) d: 20.30, 21.00, 25.14, 25.18, 29.71, 31.37, 31.43, 42.96, 43.47,
53.95, 54.14, 56.18, 56.21, 60.75, 64.16, 64.64, 65.68, 66.20, 70.55,
71.51, 75.82, 79.25, 98.09, 101.50, 101.53, 103.15, 107.35, 107.92,
108.96, 109.01, 109.61, 109.71, 129.45, 130.01, 130.08, 130.44, 133.21,
133.30, 137.56, 147.64, 147.75, 148.08, 152.67, 152.71, 170.63, 171.08;
MS (ESI-TRAP), m/z (%): 599 ([MþNa]þ, 100), 601 ([MþNa]þ, 95).
NMR (125 MHz, CDCl3) d: 44.80, 54.34, 56.34, 60.77, 64.87, 70.12,
71.06, 101.64, 106.48, 109.16, 109.98, 129.70, 131.27, 133.22, 137.82,
147.99, 148.25, 152.76, 170.76; MS (ESI-TRAP), m/z (%): 515
([MþNa]þ, 92), 517 ([MþNa]þ, 100).
4.5. General procedure for synthesis of compounds 5aei, 6b,
6h, and 6i in the presence of DIC/DMAP
4.3. Synthesis of 2a-bromopicropodophyllotoxin (11)
A solution of 9 (1.90 mmol) in 30 mL of concd HCleTHF (1:9)
was stirred for 3 h, and then adjusted the pH value to 5 by using of
5% aq Na2CO3. After removing THF, the mixture was extracted with
CH2Cl2 (40 mLꢃ3), and the combined organic phase were washed
by 5% aq Na2CO3 (20 mL) and brine (20 mL), dried over anhydrous
A mixture of 11 or 12 (59.2 mg, 0.12 mmol), carboxylic acids
13aei (0.168 mmol), N,N0-diisopropylcarbodiimide (DIC,
0.168 mmol), and 4-dimethylaminopyridine (DMAP, 0.05 mmol) in
dry CH2Cl2 (10 mL) was stirred at rt. When the reaction was com-
plete checked by TLC after 1e3 h, the mixture was filtered, and the
filtrate was collected and diluted by CH2Cl2 (30 mL). Subsequently,
the filtrate was washed by water (20 mL), 0.1 N HCl (20 mL), 5% aq
Na2CO3 (20 mL) and brine (20 mL), dried over anhydrous Na2SO4,
concentrated, and purified by PTLC to give the products.
Table 2
Insecticidal activity of novel 4
a-acyloxy-2a/b-bromopodophyllotoxins (5aei, 6b, 6h,
and 6i) at 1 mg/mL against M. separata
Compound
Corrected mortality rate (%)
20
4.5.1. Compound 5a. Yield: 78%, white solid, mp 90e92 ꢁC; [
a]
D
ꢀ93 (c 3.0 mg/mL, CHCl3); IR cmꢀ1: 2923, 2838, 1779, 1483, 1224,
10 Days
20 Days
35 Days
1124, 1031, 955, 785; 1H NMR (500 MHz, CDCl3)
d: 6.64 (s, 1H, H-5),
1
9
10
11
12
5a
5b
5c
5d
5e
5f
5g
5h
5i
6b
6h
10.0 (ꢄ8.2)
10.0 (ꢄ8.2)
13.3 (ꢄ9.4)
6.7 (ꢄ4.7)
20.7 (ꢄ4.7)
20.7 (ꢄ9.4)
24.1 (ꢄ9.4)
17.2 (ꢄ8.2)
20.7 (ꢄ4.7)
17.2 (ꢄ8.2)
20.7 (ꢄ4.7)
20.7 (ꢄ4.7)
13.8 (ꢄ9.4)
24.1 (ꢄ4.7)
20.7 (ꢄ9.4)
20.7 (ꢄ4.7)
24.1 (ꢄ4.7)
31.0 (ꢄ4.7)
17.2 (ꢄ8.2)
31.0 (ꢄ17)
31.0 (ꢄ4.7)
25.0 (ꢄ8.2)
34.5 (ꢄ12.5)
41.7 (ꢄ4.7)
45.8 (ꢄ4.7)
54.2 (ꢄ4.7)
41.7 (ꢄ4.7)
45.8 (ꢄ4.7)
37.5 (ꢄ8.2)
33.3 (ꢄ4.7)
45.8 (ꢄ4.7)
45.8 (ꢄ4.7)
50.0 (ꢄ0)
6.63 (s, 2H, H-20, H-60), 6.59 (s, 1H, H-8), 5.96 (d, J¼1.5 Hz, 1H, H-4),
5.93 (d, J¼4.5 Hz, 2H, OCH2O), 4.81 (s, 2H, H-11), 4.58 (s, 1H, H-1),
3.84 (s, 6H, 30,50-OCH3), 3.83 (s, 3H, 40-OCH3), 3.01 (s, 1H, H-3), 2.13
(s, 3H, CH3); HRMS (ESI): calcd for C24H23O9BrNa ([MþNa]þ),
557.0418; found, 557.0429.
10.0 (ꢄ8.2)
10.0 (ꢄ0)
13.3 (ꢄ4.7)
16.7 (ꢄ4.7)
10.0 (ꢄ8.2)
16.7 (ꢄ4.7)
13.3 (ꢄ4.7)
20.0 (ꢄ8.2)
16.7 (ꢄ4.7)
16.7 (ꢄ9.4)
13.3 (ꢄ4.7)
20.0 (ꢄ14.1)
20.0 (ꢄ0)
20
4.5.2. Compound 5b. Yield: 83%, white solid, mp 123e125 ꢁC; [
a]
D
45.8 (ꢄ9.4)
58.3 (ꢄ4.7)
45.8 (ꢄ4.7)
50.0 (ꢄ0)
ꢀ106 (c 3.1 mg/mL, CHCl3); IR cmꢀ1: 2946, 2889, 1774, 1733, 1595,
1505, 1228, 1173, 1125, 1075, 1030, 962, 942, 788; 1H NMR
(500 MHz, CDCl3) d
: 6.62 (s, 2H, H-20, 60), 6.61 (s, 1H, H-5), 6.58 (s,
1H, H-8), 5.95 (d, J¼2.5 Hz, 1H, H-4), 5.93 (dd, J¼4.0, 1.0 Hz, 2H,
OCH2O), 4.78e4.84 (m, 2H, H-11), 4.58 (s,1H, H-1), 3.84 (s, 6H, 30,50-
OCH3), 3.83 (s, 3H, 40-OCH3), 2.97e2.98 (m, 1H, H-3), 2.26e2.38 (m,
2H, eCH2CH2CH3), 1.67e1.74 (m, 2H, eCH2CH2CH3), 0.97 (t,
J¼7.5 Hz, 3H, eCH2CH2CH3); ESI-MS m/z: 584.79 ([MþNa]þ, 100),
41.7 (ꢄ4.7)
62.5 (ꢄ8.2)
66.7 (ꢄ4.7)
59.3 (ꢄ4.7)
50.0 (ꢄ8.2)
6i
14
17.9 (ꢄ9.4)
23.3 (ꢄ9.4)
Toosendanin

780
Y. Guo et al. / Tetrahedron 69 (2013) 774e781
586.80 ([MþNa]þ, 89); HRMS (ESI): calcd for C26H27O9BrNa
([MþNa]þ), 585.0731; found, 585.0747.
1484, 1238, 1125, 1031, 956, 733; 1H NMR (500 MHz, CDCl3)
d:
7.24e7.38 (m, 5H), 6.63 (s, 2H, H-20, 60), 6.58 (s, 1H, H-5), 6.54 (s, 1H,
H-8), 5.93 (dd, J¼2.5, 1.0 Hz, 2H, OCH2O), 5.92 (d, J¼2.5 Hz, 1H, H-4),
4.76e4.81 (m, 2H, H-11), 4.59 (s, 1H, H-1), 3.85 (s, 6H, 30,50-OCH3),
3.84 (s, 3H, 40-OCH3), 3.62e3.70 (m, 2H, eCH2C6H5), 3.01e3.02 (m,
1H, H-3); ESI-MS m/z: 634.14 ([MþNa]þ, 100), 632.22 ([MþNa]þ,
94); HRMS (ESI): calcd for C30H27O9BrNa ([MþNa]þ), 633.0731;
found, 633.0724.
20
4.5.3. Compound 5c. Yield: 61%, white solid, mp 108e110 ꢁC; [
a]
D
ꢀ106 (c 3.3 mg/mL, CHCl3); IR cmꢀ1: 2966, 2932, 2875, 1774, 1731,
1594,1481,1225,1125,1094,1025,1003, 941, 788; 1H NMR (500 MHz,
CDCl3) d
: 6.62 (s, 2H, H-20, 60), 6.61 (s,1H, H-5), 6.58 (s,1H, H-8), 5.95
(d, J¼2.5 Hz,1H, H-4), 5.93e5.94 (m, 2H, OCH2O), 4.78e4.84 (m, 2H,
H-11), 4.58 (s,1H, H-1), 3.84 (s, 6H, 30,50-OCH3), 3.83 (s, 3H, 40-OCH3),
2.97e2.98 (m, 1H, H-3), 2.27e2.39 (m, 2H, eCH2(CH2)3CH3),
1.65e1.68 (m, 2H, eCH2CH2(CH2)2CH3), 1.31e1.33 (m, 4H,
eCH2CH2(CH2)2CH3), 0.89 (t, J¼7.0 Hz, 3H, eCH2(CH2)3CH3); ESI-MS
m/z: 612.30 ([MþNa]þ, 100), 614.32 ([MþNa]þ, 84); HRMS (ESI):
calcd for C28H31O9BrNa ([MþNa]þ), 613.1044; found, 613.1029.
4.5.9. Compound 5i. Yield: 53% (in BF3$Et2O) and 85% (in DIC),
white solid, mp 96e98 ꢁC; [
a
]
20 ꢀ90 (c 3.1 mg/mL, CHCl3); IR cmꢀ1
:
D
2924, 1779, 1734, 1590, 1483, 1326, 1239, 1167, 1125, 1033, 955, 779;
1H NMR (500 MHz, CDCl3)
d: 7.87e7.91 (m, 2H, naphthalene ring),
7.83 (d, J¼8.0 Hz, 1H, naphthalene ring), 7.51e7.54 (m, 2H, naph-
thalene ring), 7.43e7.46 (m,1H, naphthalene ring), 7.37 (d, J¼7.0 Hz,
1H, naphthalene ring), 6.66 (s, 2H, H-20, 60), 6.58 (s,1H, H-5), 6.48 (s,
1H, H-8), 5.94 (d, J¼7.0 Hz, 2H, OCH2O), 5.91 (d, J¼2.0 Hz, 1H, H-4),
4.75 (s, 2H, H-11), 4.60 (s, 1H, H-1), 4.06e4.15 (m, 2H, eCH2C10H7),
3.85 (s, 6H, 30,50-OCH3), 3.84 (s, 3H, 40-OCH3), 3.03 (s, 1H, H-3); ESI-
MS m/z: 682.78 ([MþNa]þ, 100), 684.81 ([MþNa]þ, 86); HRMS
(ESI): calcd for C34H29O9BrNa ([MþNa]þ), 683.0887; found,
683.0882.
20
4.5.4. Compound 5d. Yield: 55%, white solid, mp 96e98 ꢁC; [
a]
D
ꢀ84 (c 3.2 mg/mL, CHCl3); IR cmꢀ1: 2918, 1778, 1732, 1591, 1484,
1458, 1328, 1238, 1123, 1032, 956, 743; 1H NMR (500 MHz, CDCl3)
d:
8.16 (s, 1H, NH), 7.51 (d, J¼7.5 Hz, 1H), 7.38 (d, J¼8.0 Hz, 1H),
7.21e7.24 (m, 1H), 7.17 (d, J¼2.0 Hz, 1H), 7.12e7.14 (m, 1H), 6.65 (s,
2H, H-20, 60), 6.58 (s, 1H, H-5), 6.56 (s, 1H, H-8), 5.93e5.95 (m, 3H,
H-4 and OCH2O), 4.75e4.81 (m, 2H, H-11), 4.59 (s, 1H, H-1), 3.84 (s,
6H, 30,50-OCH3), 3.83 (s, 3H, 40-OCH3), 3.81 (s, 2H, eCH2C8H6N),
3.02e3.03 (m, 1H, H-3); ESI-MS m/z: 671.73 ([MþNa]þ, 98), 673.73
([MþNa]þ, 100); HRMS (ESI): calcd for C32H28NO9BrNa ([MþNa]þ),
672.0840; found, 672.0844.
20
4.5.10. Compound 6b. Yield: 60%, white solid, mp 74e76 ꢁC; [
a]
D
ꢀ133 (c 3.0 mg/mL, CHCl3); IR cmꢀ1: 2961, 2930, 1781, 1735, 1588,
1504, 1484, 1459, 1236, 1169, 1124, 1036, 1004, 930, 769, 685; 1H
NMR (500 MHz, CDCl3) d: 6.79 (s, 1H, H-5), 6.54 (s, 1H, H-8), 6.44 (s,
20
4.5.5. Compound 5e. Yield: 73%, white solid, mp 92e94 ꢁC; [
a
]
2H, H-20, 60), 6.00 (d, J¼8.5 Hz, 2H, OCH2O), 5.93 (d, J¼8.5 Hz, 1H, H-
4), 4.90 (s, 1H, H-1), 4.38e4.42 (m, 1H, H-11), 4.30e4.33 (m, 1H, H-
11), 3.80 (s, 3H, 40-OCH3), 3.75 (s, 6H, 30,50-OCH3), 2.71e2.76 (m, 1H,
H-3), 2.35e2.46 (m, 2H, eCH2CH2CH3), 1.68e1.75 (m, 2H,
eCH2CH2CH3), 0.98 (t, J¼7.5 Hz 3H, eCH2CH2CH3); ESI-MS m/z:
584.74 ([MþNa]þ, 100), 586.82 ([MþNa]þ, 87); HRMS (ESI): calcd
for C26H27O9BrNa ([MþNa]þ), 585.0731; found, 585.0742.
D
ꢀ94 (c 3.1 mg/mL, CHCl3); IR cmꢀ1: 2921, 2850, 1777, 1729, 1591,
1483, 1229, 1123, 1030, 953, 742; 1H NMR (500 MHz, CDCl3)
d: 7.98
(s, 1H, NH), 7.55 (d, J¼8.0 Hz, 1H), 7.34 (d, J¼8.0 Hz, 1H), 7.17e7.20
(m, 1H), 7.08e7.11 (m, 1H), 6.94 (d, J¼2.5 Hz, 1H), 6.56e6.58 (m, 4H,
H-5, 8, 20, 60) 5.91e5.93 (m, 3H, H-4 and OCH2O), 4.73e4.79 (m, 2H,
H-11), 4.56 (s, 1H, H-1), 3.82 (s, 3H, 40-OCH3), 3.73 (s, 6H, 30,50-
OCH3), 2.87e2.90 (m, 1H, H-3), 2.79e2.85 (m, 2H,
eCH2CH2CH2C8H6N), 2.29e2.43 (m, 2H, eCH2CH2CH2C8H6N),
2.06e2.12 (m, 2H, eCH2CH2CH2C8H6N); ESI-MS m/z: 699.80
([MþNa]þ, 100), 701.81 ([MþNa]þ, 93); HRMS (ESI): calcd for
C34H32NO9BrNa ([MþNa]þ), 700.1153; found, 700.1144.
20
4.5.11. Compound 6h. Yield: 62%, white solid, mp 84e86 ꢁC; [
a]
D
ꢀ129 (c 3.1 mg/mL, CHCl3); IR cmꢀ1: 2916, 1762, 1702, 1584, 1502,
1458, 1235, 1122, 1032, 1006, 937, 697; 1H NMR (500 MHz, CDCl3)
d:
7.27e7.35 (m, 5H), 6.67 (s, 1H, H-5), 6.52 (s, 1H, H-8), 6.40 (s, 2H, H-
20, 60), 5.98e6.01 (m, 2H, OCH2O), 5.91 (d, J¼9.0 Hz,1H, H-4), 4.87 (s,
1H, H-1), 4.31e4.35 (m, 1H, H-11), 4.15e4.18 (m, 1H, H-11), 3.80 (s,
3H, 40-OCH3), 3.73 (s, 2H, eCH2C6H5), 3.72 (s, 6H, 30,50-OCH3),
2.65e2.70 (m, 1H, H-3); ESI-MS m/z: 632.80 ([MþNa]þ, 95), 634.77
([MþNa]þ, 100); HRMS (ESI): calcd for C30H27O9BrNa ([MþNa]þ),
633.0731; found, 633.0721.
4.5.6. Compound 5f. Yield: 57% (in BF3$Et2O) and 52% (in DIC),
20
white solid, mp 176e178 ꢁC; [
a]
ꢀ27 (c 3.0 mg/mL, CHCl3); IR
D
cmꢀ1: 2925, 2895, 1775, 1719, 1595, 1502, 1267, 1247, 1128, 1085,
1039, 753; 1H NMR (500 MHz, CDCl3)
d
: 7.86 (d, J¼8.0 Hz, 2H, H-200,
600), 7.23 (d, J¼8.0 Hz, 2H, H-300, 500), 6.72 (s, 1H, H-5), 6.66 (s, 2H, H-
20, 60), 6.64 (s, 1H, H-8), 6.01 (d, J¼2.0 Hz, 1H, H-4), 5.96 (s, 2H,
OCH2O), 5.02 (d, J¼9.5 Hz, 1H, H-11), 4.88e4.91 (m, 1H, H-11), 4.62
(s, 1H, H-1), 3.80 (s, 3H, 40-OCH3), 3.68 (s, 6H, 30,50-OCH3),
3.20e3.22 (m, 1H, H-3), 2.43 (s, 3H, 400-CH3); ESI-MS m/z: 632.26
([MþNa]þ, 100), 634.26 ([MþNa]þ, 98); HRMS (ESI): calcd for
C30H27O9BrNa ([MþNa]þ), 633.0731; found, 633.0722.
4.5.12. Compound 6i. Yield: 53% (in BF3$Et2O) and 83% (in DIC),
20
white solid, mp172e174 ꢁC; [
a
]
ꢀ163 (c 3.0 mg/mL, CHCl3); IR
D
cmꢀ1: 2919,1770,1733,1591,1507,1484,1235,1128,1037,1005, 862,
781; 1H NMR (500 MHz, CDCl3)
: 7.99 (d, J¼8.0 Hz, 1H, naphtha-
d
lene ring), 7.88 (d, J¼7.5 Hz, 1H, naphthalene ring), 7.81e7.82 (m,
1H, naphthalene ring), 7.50e7.56 (m, 2H, naphthalene ring),
7.41e7.44 (m, 2H, naphthalene ring), 6.54 (s, 1H, H-5), 6.48 (s, 1H,
H-8), 6.33 (s, 2H, H-20, 60), 5.96 (d, J¼17.0 Hz, 2H, OCH2O), 5.90 (d,
J¼9.0 Hz,1H, H-4), 4.83 (s,1H, H-1), 4.24e4.28 (m,1H, H-11), 4.18 (s,
2H, eCH2C10H7), 4.01e4.04 (m,1H, H-11), 3.79 (s, 3H, 40-OCH3), 3.65
(s, 6H, 30,50-OCH3), 2.58e2.63 (m, 1H, H-3); ESI-MS m/z: 684.29
([MþNa]þ, 100), 682.31 ([MþNa]þ, 98); HRMS (ESI): calcd for
C34H29O9BrNa ([MþNa]þ), 683.0887; found, 683.0877.
4.5.7. Compound 5g. Yield: 84% (in BF3$Et2O) and 86% (in DIC), pale
20
yellow solid, mp 114e116 ꢁC; [
a
]
ꢀ17 (c 3.5 mg/mL, CHCl3); IR
D
cmꢀ1: 2924, 1780, 1722, 1590, 1532, 1484, 1350, 1241, 1124, 1033,
950, 718; 1H NMR (500 MHz, CDCl3) : 8.79 (s, 1H, H-200), 8.47 (d,
d
J¼8.0 Hz, 1H, H-400), 8.32 (d, J¼7.5 Hz, 1H, H-600), 7.68 (t, J¼8.0 Hz,
1H, H-500), 6.72 (s, 1H, H-5), 6.67 (s, 1H, H-8), 6.64 (s, 2H, H-20, 60),
6.13 (d, J¼2.0 Hz,1H, H-4), 5.98 (s, 2H, OCH2O), 4.98 (d, J¼9.5 Hz,1H,
H-11), 4.89e4.91 (m, 1H, H-11), 4.65 (s, 1H, H-1), 3.80 (s, 3H, 40-
OCH3), 3.71 (s, 3H, 30,50-OCH3), 3.21e3.23 (m, 1H, H-3); ESI-MS m/z:
663.75 ([MþNa]þ, 91), 665.72 ([MþNa]þ, 100); HRMS (ESI): calcd
for C29H24NO11BrNa ([MþNa]þ), 664.0425; found, 664.0409.
4.6. General procedure for synthesis of compounds 5f, 5g, 5i,
and 6i in the presence of BF3$Et2O
To a mixture of 11 or 12 (59.2 mg, 0.12 mmol), and carboxylic
acids 13f,13g or 13i (0.144 mmol) in dry CH2Cl2 (10 mL), a solution of
BF3$Et2O (0.144 mmol) in dried CH2Cl2 (5 mL) was added dropwise
20
4.5.8. Compound 5h. Yield: 55%, white solid, mp 85e87 ꢁC; [
a]
D
ꢀ67 (c 3.3 mg/mL, CHCl3); IR cmꢀ1: 2924, 2836, 1780, 1734, 1590,

Y. Guo et al. / Tetrahedron 69 (2013) 774e781
781
to keep the temperature below ꢀ15 ꢁC. After adding, the reaction
Acknowledgements
temperature was raised from ꢀ15 ꢁC to rt, and the reaction process
was checked by TLC analysis. When the reaction was complete for
1e3 h, pyridine (0.12 mmol) was added to the mixture, which was
diluted by CH2Cl2 (30 mL). The mixture was then washed by water
(20 mL), HCl (0.1 mol/L, 20 mL), 5% aq NaHCO3 (20 mL), and brine
(20 mL), dried over anhydrous Na2SO4, concentrated in vacuo, and
purified by PTLC to give the products.
This work was supported by National Natural Science Founda-
tion of China (No. 31071737, 31000862), and Program for Chang-
jiang Scholars and Innovative Research Team in University
(IRT1035). We are deeply grateful to Prof. H.L. Zhang for the NMR
experiments.
References and notes
4.7. Biological assay
1. Issell, B. F. Cancer Chemother. Pharmacol. 1982, 7, 73.
The insecticidal activity of 5aei, 6b, 6h, and 6i against the pre-
third-instar larvae of M. separata was tested by the leaf-dipping
method at the concentration of 1 mg/mL.11 For each compound,
30 larvae (10 larvae per group) were used. Acetone solutions of
5aei, 6b, 6h, and 6i and toosendanin (used as a positive control)
were prepared at the concentration of 1 mg/mL. Fresh wheat leaves
were dipped into the corresponding solution for 3 s, then taken out,
and dried in a room. Leaves treated with acetone alone were used
as a control group. Several treated leaves were kept in each dish,
where every 10 larvae were raised. If the treated leaves were con-
sumed, the corresponding ones were added to the dish. After 48 h,
untreated fresh leaves were added to the all of the dishes until adult
emergence. The experiment was carried out at 25ꢄ2 ꢁC and a rel-
ative humidity (RH) 65e80%, and on 12/12 h (light/dark) photo-
period. The insecticidal activity of the tested compounds against
the pre-third-instar larvae of M. separata was calculated with the
formula:
2. Hartwell, J. L.; Schrecker, A. W. Fortschr. Chem. Org. Naturst. 1958, 15, 83.
3. Xu, H.; Lv, M.; Tian, X. Curr. Med. Chem. 2009, 16, 327.
4. Lv, M.; Xu, H. Mini-Rev. Med. Chem. 2011, 11, 901.
5. You, Y. J. Curr. Pharm. Des. 2005, 11, 1695.
6. Gordaliza, M.; Garcia, P. A.; Miguel Del Corral, J. M.; Castro, M. A.; Gomez-Zurita,
M. A. Toxicon 2004, 44, 441.
7. Kozawa, M.; Baba, K.; Matsuyama, Y.; Kido, T.; Sakai, M.; Takemoto, T. Chem.
Pharm. Bull. 1982, 30, 2885.
8. Miyazawa, M.; Fukuyama, M.; Yoshio, K.; Kato, T.; Ishikawa, Y. J. Agric. Food
Chem. 1999, 47, 5108.
9. Gao, R.; Gao, C. F.; Tian, X.; Yu, X. Y.; Di, X. D.; Xiao, H.; Zhang, X. Pest Manag. Sci.
2004, 60, 1131.
10. Liu, Y. Q.; Liu, Y.; Xiao, H.; Gao, R.; Tian, X. Pestic. Biochem. Physiol. 2008, 91, 116.
11. Xu, H.; Wang, J. J.; Sun, H. J.; Lv, M.; Tian, X.; Yao, X. J.; Zhang, X. J. Agric. Food
Chem. 2009, 57, 7919.
12. Xu, H.; Xiao, X. Bioorg. Med. Chem. Lett. 2009, 19, 5415.
13. Kumar, K. A.; Singh, S. K.; Kumar, B. S.; Doble, M. Cent. Eur. J. Chem. 2007, 5, 880.
14. Xu, H.; Xiao, X.; Zhao, X. F.; Guo, Y.; Yao, X. J. Bioorg. Med. Chem. Lett. 2011, 21, 4008.
15. Xu, H.; Wang, Q. T.; Guo, Y. Chem.dEur. J. 2011, 17, 8299.
16. Gensler, W. J.; Gatsonis, C. D. J. Org. Chem. 1966, 31, 4004.
17. Glinski, M. B.; Freed, J. C.; Durst, T. J. Org. Chem. 1987, 52, 2749.
18. Crystallographic data (excluding structure factors) for the structures of 5i and
6i in this Letter has been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication number CCDC 816002 and 815493, re-
spectively. Copies of the data can be obtained, free of charge, on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: þ44(0)1223 336033 or e-
mail: deposit@ccdc.cam.ac.uk].
corrected mortality rate ð%Þ ¼ ðT ꢀ CÞ ꢃ 100=ð1 ꢀ CÞ
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.
19. Lee, K. H.; Imakura, Y.; Haruna, M.; Beers, S. A.; Thursto, L. S.; Dai, H. J.; Chen, C.
H.; Liu, S. Y.; Cheng, Y. C. J. Nat. Prod. 1989, 52, 606.