Synthesis and insect attractant activity of fluorine-containing Pinus diterpenic amides and imines

Article abstract of DOI:10.1080/14786410802155954

A series of fluorine-containing Pinus diterpenic amides and imines have been synthesised and their structures were confirmed by elemental analysis, IR, 1H NMR spectroscopy and single crystal X-ray diffraction. Their insect attractant activity to Spodoptera litura were screened by leaf plate method; the results indicated that most fluorine-containing dehydroabietic amides and imines exhibited attractive activity to S. litura, in which dehydroabietic p-trifluoromethyl amide (A6) exhibit seven times the attractive rate compared with blank at the concentration of 0.01 g mL-1. The fluorine moiety fused to the benzene ring results in decreased attractive rates for amides except (A6), while the effects of fluorine result in increased attractive rates for diterpenic imines.

Full text of DOI:10.1080/14786410802155954

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Synthesis and insect attractant activity
of fluorine-containing Pinus diterpenic
amides and imines
Xiaoping Rao a , Zhanqian Song a , Zhaojiu Han b & Zhikuan Jiang b
a Institute of Chemical Industry of Forest Products, Chinese
Academy of Forestry, Nanjing, P.R. China
b Military Medicine Institute of Nanjing Command, Nanjing, P.R.
China
Published online: 29 Oct 2009.
To cite this article: Xiaoping Rao , Zhanqian Song , Zhaojiu Han & Zhikuan Jiang (2009): Synthesis
and insect attractant activity of fluorine-containing Pinus diterpenic amides and imines, Natural
Product Research: Formerly Natural Product Letters, 23:9, 851-860
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Natural Product Research
Vol. 23, No. 9, 15 June 2009, 851–860
Synthesis and insect attractant activity of fluorine-containing
Pinus diterpenic amides and imines
a
Xiaoping Rao , Zhanqian Song , Zhaojiu Han and Zhikuan Jiang
a
b
b
*
aInstitute of Chemical Industry of Forest Products, Chinese Academy of Forestry, Nanjing,
P.R. China; Military Medicine Institute of Nanjing Command, Nanjing, P.R. China
b
(Received 17 October 2007; final version received 23 April 2008)
A series of fluorine-containing Pinus diterpenic amides and imines have been
synthesised and their structures were confirmed by elemental analysis, IR,
1H NMR spectroscopy and single crystal X-ray diffraction. Their insect
attractant activity to Spodoptera litura were screened by leaf plate method; the
results indicated that most fluorine-containing dehydroabietic amides and imines
exhibited attractive activity to S. litura, in which dehydroabietic p-trifluoromethyl
amide (A6) exhibit seven times the attractive rate compared with blank at the
concentration of 0.01 g mLꢀ1. The fluorine moiety fused to the benzene ring
results in decreased attractive rates for amides except (A6), while the effects of
fluorine result in increased attractive rates for diterpenic imines.
Keywords: fluorine-containing Pinus diterpenic; single crystal; insect attractant;
attractive rate
1. Introduction
Insect attractants are useful chemicals for determining movement of insect populations;
they are used in an environmentally friendly way that has no negative effect on other
animals or humans (Hao, Thi, Giang, Khoa, & Son, 1996). The most common use of
chemical attractants is in traps, to monitor insect populations, and they can also be widely
used as poison bait to disrupt insect mating. Insect attractants and feeding arrestants are
usually used in combination with an insecticide in pest management programmes (Momin
& Nair, 2002). Spodoptera litura is a widely dispersed pest in Asia and Pacific regions, and
is also a polyphagous pest for many agricultural crops. They will chew large areas of the
leaf and even can defoliate a crop when the pests are numerous. In such cases, the larvae
migrate in large groups from one field to another in search of food. So, to prevent and
control S. litura is of great importance to agriculture in these areas.
Developing high value products from main chemical components of natural resources
through chemical modification is an important direction of natural product research.
Pinus diterpenic resin acids have attracted great interest for their special chemical
structures and wide range of biological activities. The major component of disproportio-
nated rosin – dehydroabietic acid – is extremely stable to air oxidation, so that it is suitable
*Corresponding author. Email: rxping2001@163.com
ISSN 1478–6419 print/ISSN 1029–2349 online
ß 2009 Taylor & Francis
DOI: 10.1080/14786410802155954
http://www.informaworld.com

852
X. Rao et al.
as a raw material for design and synthesis of biological derivatives (Kushnir et al., 2003).
The derivatives of diterpenic resin acids displayed a significant series of biological
activities, such as anti-bacterial, anti-fungal, anti-cancer and anti-inflammatory (Feio,
Gigante, Roseiro, & Marcelo-Curto, 1999; Feio, Roseiro, Gigante, & Marcelo-Curto,
1997; San, Gordaliza, Salinero, & Miguel, 1993; Smith, Williamson, Zloh, & Gibbons,
2005; Ulusu, Ercil, Sakar, & Tezcan, 2002; Wada et al., 1985; Yanez, Theoduloz, &
Schmeda-Hirschmann, 2005). Naturally occurring resin acids have insect anti-feedant
characteristics; isopimaric acid is superior to other resin acids in inhibiting larval
development in several Lepidoptera species, including the pink bollworm.
It is well known that fluorine can affect the biological activities of compounds in
a number of ways due to its unique properties, such as high thermal stability, lipophilicity,
special biomimetic effect and electronegativity (Xua, Qianb, Lia, Songa, & Chena, 2005).
This implied that introducing fluorine atoms into the parent compound could cause a
big change in its bioactivities.
Although much attention has been paid to the biological derivatives of dehydroabietic
acid, its fluorine-containing derivatives have not yet been dealt with. In this article,
we describe the synthesis and insect attractant activity of fluorine-containing Pinus
diterpenic amides and imines.
2. Results and discussion
2.1. Synthesis
The tricyclic phenanthrene structure of dehydroabietic acid has high sterical hindrence to
the carboxyl acid group; the modification of the carboxyl acid needs secure conditions,
such as high temperature, high pressure and a catalyst (Kushnir et al., 2003). However, the
reaction activities can be highly promoted through a chloride intermediate. Trichloro
phosphorous has been found to be the best reagent to prepare dehydroabietic chloride.
Fluorine-containing dehydroabietic amides can be obtained from dehydroabietic acid
through chloride intermediate by two steps of reactions. The reaction process is shown in
Scheme 1.
Fluorine-containing dehydroabietic imines can be obtained by direct condensation
reaction with dehydroabietylamine and fluorine-containing benzaldehydes. Despite of
sterical hindrance to the amino group of tricyclic phenethrane structure, the condensation
reaction affords high yields of fluorine-containing imines. Scheme 2 shows the reaction
process of fluorine-containing dehydroabietic imines.
PCl
3
OH
Cl
N
H
O
O
O
R
1
Comp A1 A2
A3 A4
A5
A6
R =
H
o-F p-F 2,6-F 3,5-F p-CF3
1
Scheme 1. Reaction process of fluorine-containing amides.

Natural Product Research
853
Dehydroabietic anilide (A1): C26H33NO, white crystal: yield 69.8%, m.p. 139.2ꢁC,
elemental analysis: calculate(found),C: 83.20(83.21); H: 8.80(8.78); N: 3.73(3.70);
IR(cmꢀ1): 3339(N–H); 2956(–CH3,–CH2); 1659(O¼C–N); 823(Ar–H); 1H NMR:
(CDCl3 ꢀ/ppm. 400 MHz), 7.56(1H,CONH–); 7.54–6.91 (8H, C¼CH–); 2.86(1H,
ꢀCH(Me)2); 2.93–1.61(10H, –CH2–); 1.63 (1H,4CH–); 1.43–1.24(12H, –CH3).
Dehydroabietic o-fluoro-anilide (A2): C26H3I3NO, white crystal: yield 58.5%, m.p.
93.2ꢁC, elemental analysis: calculate(found), C: 79.39(79.27); H: 8.14(8.19); N: 3.56(3.52);
1
IR(cmꢀ1): 3316(N–H); 2960(–CH3,–CH2); 1654(O¼C–N); 821(Ar–H); H NMR: (CDCl3
ꢀ/ppm. 400 MHz), 7.80 (1H, CONH–); 8.36–6.91 (7H, C¼CH–); 2.86 (1H, –CH(Me)2);
2.93–1.64 (10H, –CH2–); 1.61 (1H, 4CH–); 1.46–1.25 (12H, –CH3).
Dehydroabietic p-fluoro-anilide (A3): C26H3I3NO, white crystal: yield 46.3%, m.p.
141.1ꢁC, elemental analysis: calculate(found), C: 79.39(79.43); H: 8.14(8.07); N: 3.56(3.52);
1
IR(cmꢀ1): 3423(N–H); 2955(–CH3,–CH2); 1659(O¼C–N); 831(Ar–H); H NMR: (CDCl3
ꢀ/ppm. 400 MHz), 7.80 (1H, CONH–); 7.22(1H, CONH–); 7.50–6.90(7H, C¼CH–);
2.85(1H, –CH(Me)2); 2.92–1.80(10H, –CH2–); 1.59(1H, 4CH–); 1.42–1.24(12H, –CH3).
Dehydroabietic 2,6-difluoro-anilide (A4): C26H31F2NO, white crystal: yield 58.6%, m.p.
159.9ꢁC, elemental analysis: calculate(found), C: 75.91(75.88); H: 7.54(7.50); N: 3.41(3.44);
1
IR(cmꢀ1): 3310(N–H); 2960(–CH3,–CH2); 1659(O¼C–N); 826(Ar–H); H NMR: (CDCl3
ꢀ/ppm. 400 MHz), 7.27(1H, CONH–); 7.22–6.91(6H, C¼CH–); 2.85(1H, –CH(Me)2);
2.94–1.78 (10H, –CH2–); 1.56(1H, 4CH–); 1.44–1.24(12H, –CH3).
Dehydroabietic 3,5-fifluoro-anilide (A5): C26H31F2NO, white crystal: yield 56.9%, m.p.
134.1ꢁC, elemental analysis: calculate(found), C: 75.91(75.96); H: 7.54(7.56); N: 3.41(3.40);
1
IR(cmꢀ1): 3315(N–H); 2961(–CH3,–CH2); 1644(O¼C–N); 805(Ar–H); H NMR: (CDCl3
ꢀ/ppm. 400 MHz), 7.85(1H, CONH–); 7.44–6.77(6H, C¼CH–); 2.85(1H, –CH(Me)2);
2.92–1.80 (10H, –CH2–); 1.62(1H, 4CH–); 1.45–1.23(12H, –CH3).
Dehydroabietic p-trifluoromethyl-anilide (A6): C27H3I33NO, white crystal: yield 43.3%,
m.p. 169.5ꢁC, elemental analysis: calculate(found), C: 73.14(73.20); H: 7.22(7.16);
N: 3.16(3.22); IR(cmꢀ1): 3341(N–H); 2961(–CH3,–CH2); 1675(O¼C–N); 841(Ar–H);
1H NMR: (CDCl3 ꢀ/ppm. 400 MHz), 7.69(1H,CONH–); 7.67–6.90(6H,C¼CH–);
2.89(1H,–CH(Me)2); 2.92–1.80 (10H, –CH2–); 1.59(1H, 4CH–); 1.43–1.23(12H, –CH3).
CHO
+
R
C
H
NCH
CH NH
2
2
2
R
2
Comp
I1
I2
I3
R =
p-CF
H
m-F
2
3
Scheme 2. Reaction process of fluorine-containing imines.

854
X. Rao et al.
Dehydroabietylamine benzaldehyde imine (I1): C27H35N, white crystal: yield 70.2%, m.p.
104.5ꢁC, elemental analysis: calculate(found), C: 86.22(86.86); H: 9.49(9.39); N: 3.61(3.75),
IR(cmꢀ1): 2931(–CH3,–CH2); 1644(C¼N); 1040(C–N); 832(Ar–H),1H NMR: (CDCl3.
ꢀ/ppm. 400 MHz), 8.26(1H, N¼CH–); 7.76–6.91(8H, C¼CH–); 3.54(2H, N–CH2–);
2.88(1H, –CH(Me)2); 2.86–1.58(10H, –CH2–); 1.27–1.08(12H, –CH3).
Dehydroabietylamine m-fluoro-benzaldehyde imine (I2): C27H34FN, white crystal: yield
95.3%, m.p. 89.2ꢁC, elemental analysis: calculate(found), C: 83.26(83.16); H: 8.77(8.69);
N: 3.41(3.58), IR(cmꢀ1): 2930(–CH3,–CH2); 1654(C¼N); 1134(C–N); 785(Ar–H),
1H NMR: (CDCl3 ꢀ/ppm. 400 MHz), 8.24(1H, N¼CH–); 7.51–6.91(7H, C¼CH–);
3.53(2H, N–CH2–); 2.91(1H, –CH(Me)2); 2.85–1.56(10H, –CH2–); 1.28–1.09(12H, –CH3).
Dehydroabietylamine p-trifluoromethyl benzaldehyde imine (I3): C28H34F3N, white crystal:
yield 86.9%, m.p. 119.5ꢁC, elemental analysis: calculate(found), C: 75.97(76.19);
H: 7.71(7.71); N: 3.21(3.17), IR(cmꢀ1): 2930(–CH3,–CH2); 1654(C¼N); 1134(C–N);
785(Ar–H), 1H NMR: (CDCl3 ꢀ/ppm. 400 MHz), 8.24(1H, N¼CH–); 7.51–6.91
(7H, C¼CH–); 3.53(2H, N–CH2–); 2.91(1H, –CH(Me)2); 2.85–1.56(10H, –CH2–);
1.28–1.09(12H, –CH3).
2.2. X-ray single crystal structure
White crystals suitable for X-ray analysis were obtained by solvent evaporation under
room temperature. The crystallographic details are summarised in Table 1. The selected
bond lengths and angles are shown in Table 2.
As shown in Figure 1, the two crystallographically independent molecules in the crystal
structure of compound I2, in each molecule there are four six-membered rings which
exhibited plane, half-chair, chair and plane configurations, respectively. (The atomic
coordinates, bond lengths and angles and the X-ray crystallographic files on CIF format
for the determination of compound I2 can be obtained from the author by request). The
two methyl groups on the phenanthrene structure were in the same side of rings. There are
two fluorine atoms in each molecules, the atom occupational rate is 50%, respectively. The
atoms of isopropyl group showed disorder. The bond lengths of C¼N and C–N were
˚
˚
1.268 A and 1.433 A, respectively. C¼N bond exhibited trans configuration. The packing
diagram of compound I2 is shown in Figure 2; hydrogen bond and weak ꢁ ꢂ ꢂ ꢂ ꢁ stack
make the molecules stable.
2.3. Insect attractant activity
The insect attractant activity of fluorine-containing dehydroabietic amides and imines to
S. litura were investigated at the concentration of 0.01 g mLꢀ1. The attractive rates of
compounds at 24, 48 and 72 h are listed in Table 3, 4 and 5, respectively. These data are
summarised in Table 6. The bigger attractive rate means the attractant activity is higher.
The results below zero mean the compounds exhibited anti-feedant activity to S. litura.
At the first 24 h bioassay, some fluorine-containing amides exhibited higher attractive
rates and some displayed lower attractive rates compared with parent compound.
All fluorine-containing imines exhibited higher attractive rates compared with parent
compound. After 48 h bioassay, most fluorine-containing compounds except for A6
exhibited lower attractive rates while all imines exhibited higher attractive rates compared

Natural Product Research
Table 1. Crystal data and structure refinement for I2.
855
Empirical formula
Formula weight
Temperature (K)
C27H30FN
387.52
293 (2)
0.71073
Triclinic
P21
6.0280 (12)
10.996 (2)
18.519 (4)
74.20 (3)
82.29 (3)
77.01 (3)
˚
Wavelength (A)
Crystal system
Space group
˚
a (A)
˚
b (A)
˚
c (A)
ꢂ (ꢁ)
ꢃ (ꢁ)
ꢄ (ꢁ)
3
˚
V (A )
1147.4 (4)
1.122
0.070
Density (calculated) (mg mꢀ3
)
)
Absorption coefficient (mmꢀ1
F(0 0 0)
416
Crystal size (mm3)
0.30 ꢃ 0.20 ꢃ 0.10
1.96 to 25
0 ꢄ h ꢄ 7, ꢀ12 ꢄ k ꢄ 13,
ꢀ21 ꢄ l ꢄ 22
4365/4365
98.4
0.9821, 0.9309
4365/3/559
1.024
ꢅ range for data collection (ꢁ)
Limiting indices
Reflections collected/unique
Completeness to ꢅ ¼ 25.99 (%)
Max. and min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I 4 2ꢆ(I)]
R indices (all data)
Absolute structure parameter
R1 ¼ 0.0961, wR2 ¼ 0.2772
R1 ¼ 0.1608, wR2 ¼ 0.2262
2(4)
ꢀ3
˚
Largest diff. peak and hole (e A
)
0.363, ꢀ0.184
P
P
P
P
2
2 1=2
Note: R1 ¼ kF0j ꢀ jFck= jF0j; wR2 ¼ ½wðF20 ꢀ Fc2Þ = ½wðF02Þ ꢅ
:
with parent compound. After 72 h bioassay, most fluorine-containing compounds except
for A6 and A2 exhibited lower attractive rates, while most imines except for I3 exhibited
higher attractive rates compared with parent compound.
The attractive rates of all diterpenic fluorine-containing compounds to S. litura are
listed in Table 6. From the results, it can be concluded that the fluorine atom introduced to
the amides may result in the decrease of attractive rates of dehydroabietic amides except
A6, while the introduction of fluorine atom to the imines may lead to the increase of
attractive rates of dehydroabietic imines. The trifluoromethyl amide and m-fluoro imine
exhibited higher activities than that of parent compound by four to seven times in terms of
attractive rates. These compounds exhibited higher attractant activities at the first 24 h
bioassay, the activities are higher at first, after 48 h the activity reduced greatly, and at 72 h
the activities increased.
3. Experimental
3.1. Reagents and instruments
All chemicals purchased were of reagent grade and used without further
purification. Infrared spectrum was recorded as KBr pellets on a Bio-Rad FTS-185

856
X. Rao et al.
Table 2. Selected bond lengths and angles for I2.
˚
Bond length (A)
N(1)–C(19)
N(1)–C(18)
C(7)–C(6)
N(2)–C(33)
N(2)–C(34)
C(41)–C(42)
F(1)–C(24)
F(2)–C(22)
1.268 (11)
1.433 (11)
1.377 (12)
1.232 (11)
1.460 (11)
1.530 (12)
1.241 (15)
1.23 (2)
Bond angles (ꢁ)
C(3)–C(2)–C(4)
C(6)–C(7)–C(9)
C(19)–N(1)–C(18)
C(29)–C(30)–C(31)
F(1)–C(24)–C(23)
F(2)–C(22)–C(21)
N(1)–C(18)–C(17)
F(3)–C(28)–C(29)
C(48)–C(47)–C(46)
112.7 (10)
121.9 (7)
120.0 (8)
119.5 (9)
119.8 (15)
122.6 (15)
112.4 (7)
124.7 (16)
120.0 (11)
Torison angles (ꢁ)
C(16)–C(15)–C(14)–C(9)
C(24)–C(23)–C(22)–F(2)
C(24)–C(23)–C(22)–C(21)
C(10)–C(11)–C(12)–C(6)
N(1)–C(19)–C(20)–C(25)
C(16)–C(17)–C(18)–N(1)
C(54)–C(17)–C(18)–N(1)
C(40)–C(39)–C(38)–C(37)
C(37)–C(35)–C(41)–C(40)
C(44)–C(49)–C(48)–C(50)
56.7 (9)
169.8 (18)
1 (2)
ꢀ42.5 (11)
170.3 (10)
50.7 (9)
ꢀ70.3 (9)
56.3 (10)
ꢀ50.4 (8)
179.6 (10)
IR spectrophotometer. Melting points were determined by XT5 melting point apparatus.
1H NMR spectrum was recorded on a Bruker AVANCE 400 spectrometer. (CDCl3
as solvent). C, H, N elemental analysis was performed by a PE-2400CHN instrument.
3.2. Synthesis of dehydroabietic amides
A mixture of dehydroabietic acid (0.1 mol), phosphorous trichloride (6 mL) and
chloroform (40 mL) was stirred at 333 k for 3 h, then trichloroform was distilled off and
the residue was added to the fluorine-containing aniline (0.2 mol) in toluene solution; after
further 24 h stirring at room temperature, the resulting mixture was filtrated and the filter
was washed with hydrochloride and water, then the solvent was distilled off, upon
recrystallisation from acetone, white crystals were obtained.
3.3. Synthesis of dehydroabietic imines
The dehydroabietic imines were prepared according to the procedure of direct
condensation reaction. Dehydroabietylamine (10 mmol) dissolved in 200 mL ethanol,

Natural Product Research
857
Figure 1. ORTEP diagram of crystal I2.
Figure 2. Molecular packing arrangement in the unit cell of crystal I2.
10 mmol fluorine-containing benzaldehyde dissolved in 100 mL ethanol solution were
added dropwise into the dehydroabietylamine solution, the mixture were refluxed for 3 h
and the crystal was filtrated and recrystallised from acetone. Single crystals were grown
from acetone.

858
X. Rao et al.
Table 3. Attractive rates of dehydroabietic amides and imines to
Spodoptera litura after 24 h.
Times of
medcine
Times of
blank
Attractive
rate (%)
Compound
A1
A2
A3
A4
A5
A6
I1
67
40
15
3
19
58
15
36
57
22
18
18
15
30
8
51
9
21
206.67
122.22
ꢀ16.67
ꢀ80.00
ꢀ36.67
650.00
ꢀ70.59
300.00
171.43
I2
I3
Table 4. Attractive rates of dehydroabietic amides and imines to
Spodoptera litura after 48 h.
Times of
medcine
Times of
blank
Attractive
rate (%)
Compound
A1
A2
A3
A4
A5
A6
I1
341
52
56
37
220
51
46
41
61
46
114
59
38.14
1.96
21.74
ꢀ9.76
ꢀ13.12
206.52
49.12
53
141
170
181
233
I2
I3
206.78
71.32
136
Table 5. Attractive rates of dehydroabietic amides and imines to
Spodoptera litura after 72 h.
Times of
medicine
Times of
blank
Attractive
rate (%)
Compound
A1
A2
A3
A4
A5
A6
I1
361
130
94
203
70
118
83
159
44
184
94
66.67
85.71
ꢀ20.34
ꢀ3.61
ꢀ2.52
350.00
48.37
80
155
198
273
268
279
I2
I3
185.11
7.31
260
3.4. X-ray crystallography
The crystal structure of compound I2 was determined by X-ray single crystal
diffraction. XRD data were collected on a Enraf-Nonius CAD-4 diffractometer equipped

Natural Product Research
859
Table 6. Attractive rates of dehydroabietic amides and imines to
Spodoptera litura.
Compound
24 h
48 h
72 h
A1
A2
A3
A4
A5
A6
I1
206.79
122.22
ꢀ16.67
ꢀ80.00
ꢀ36.67
625.00
ꢀ70.59
300.00
171.43
38.14
1.96
66.67
85.71
21.74
ꢀ9.76
ꢀ13.12
206.52
49.12
206.78
71.32
ꢀ20.34
ꢀ3.61
ꢀ2.52
350.00
48.37
I2
I3
185.11
7.31
˚
with Mo-Kꢂ (ꢇ ¼ 0.07103 A) at 293 K. A single crystal suitable for determination was
mounted inside a glass fibre capillary. The structure of compound I2 was solved by direct
methods and refined by full-matrix least squares on F2. All the hydrogen atoms were
added in their calculated positions and all the non-hydrogen atoms were refined with
anisotropic temperature factors. SHELXS97 were used to solve the structure and
SHELTL were used to refine the structure (Sheldrick, 1997a and b).
3.5. Insect attractant bioassay
The Pinus diterpenic amides and imines were dissolved in acetone and tween 60 mixed
solvent to form 0.01 g mLꢀ1 solution. A 15 cm diameter leaf was dissolved in the test
solution and another was dissolved in the same solvent for comparison; S. litura was
introduced in a special equipment and the times of S. litura in different leaf plates was
determined. The attractive rates were calculated using the following equation:
M ꢀ B
A ¼
ꢃ 100%,
B
in which A is attractive rate, M is the times of S. litura stopped in the medicine leaf plate
and B is the times of S. litura stopped in the blank leaf plate.
4. Conclusions
Insect attractants are of great interest in pest management programmes; especially those
from natural products are attracting great attention, as these kinds of products are
environmentally friendly to animals and humans. Pinus dehydroabietic acids are widely
distributed in the secretion of Pinus trees, and their special chemical structure and wide
range of biological activities attracted our attention. Naturally occuring pine resin acids
exhibited insect anti-feedant activities against some pests, and in our first thought, we
wanted to obtain anti-feedants against S. litura from pine resin acids and their derivatives.
However, to our surprise, the amides and imines from pine resin acids and those
derivatives exhibited significant insect attractant activities to S. litura. From the bioassay
results, fluorine-containing Pinus diterpenic amides and imines exhibited insect attractant

860
X. Rao et al.
activities to S. litura; the fluorine introduced to the amides may result in the decrease
of attractant rates of dehydroabietic amides (except A6), and the introduction of fluorine
atom to the imines may result in the increase of attractive rates of dehydroabietic imines.
The trifluoromethyl amide and m-fluoro imine exhibited higher activities; the attractive
rates were four to seven times greater compared with blank. The characteristic group,
the number, and the position of fluorine atoms in the benzene ring affect the insect
attractant activity of compounds.
Acknowledgements
We gratefully acknowledge financial support of this work by the National Natural Science
Foundation of China (No. 30771690) and the Forestry Commonwealth Industry Special Foundation
of China (No. 200704008).
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