Synthesis and metal ion binding activity of methyl 12-amino-13-nitro-7-oxo dehydrodeisopropylabietate derivatives

Article abstract of DOI:10.1007/s00044-011-9766-2

Starting from dehydrobaietic acid with the analogous structure of carnosic acid, the intermediate methyl 12-bromo-13-nitro-7-oxo dehydrodeisopropylabietate was synthesized through methylation, bromination, carbonylation, and nitration. Subsequently, the c

Full text of DOI:10.1007/s00044-011-9766-2

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2012) 21:2494–2500
DOI 10.1007/s00044-011-9766-2
ORIGINAL RESEARCH
Synthesis and metal ion binding activity of methyl 12-amino-13-
nitro-7-oxo dehydrodeisopropylabietate derivatives
•
Kai Wang Xianxian Liu Xianghui Yi
•
•
•
Hengshan Wang Ye Zhang Yingming Pan
•
Received: 13 September 2010 / Accepted: 27 July 2011 / Published online: 18 August 2011
ꢀ Springer Science+Business Media, LLC 2011
Abstract Starting from dehydrobaietic acid with the
analogous structure of carnosic acid, the intermediate methyl
12-bromo-13-nitro-7-oxo dehydrodeisopropylabietate was
synthesized through methylation, bromination, carbonyl-
ation, and nitration. Subsequently, the coupling of methyl
12-bromo-13-nitro-7-oxo dehydrodeisopropylabietate with
aliphatic or aromatic primary amine by Ullmann condensa-
tion reaction produced a series of methyl 12-imino-13-nitro-
7-oxo dehydrodeisopropylabietate derivatives. In order to
probe their antioxidant effects through metal ion chelation
mechanism, the metal ion binding abilities on Cu2? and Fe2?
of these compounds were studied using fluorescence
quenching method. The results indicated that each com-
pound showed obvious chelation activity with the binding
constants (KA) of the 102 L mol-1 order of magnitude, which
implied its potential pharmacology application as antioxi-
dant by the inhibition of Feton reaction through chelation
Introduction
Dehydroabietic acid (DDA) is one of the isomerides in the
renewable rosin. Previous studies have demonstrated that
DDA derivatives shows the bioactivity of antiulcer (Wada
et al., 1985), against schistosomiasis (Steck, 1981), anti-
microbial (Feio et al., 1999), and gastroprotective (Beatriz
and Guillermo, 2005). With the special skeleton, DDA was
also used to synthesize other bioactivity compound such as
3-oxosapriparaquinone (Matsumoto and Takeda, 1996),
steroidal hormones (Matsumoto and Imai, 1988), 12-de-
oxyroyleanone, cryptoquinone, and 11, 14-dihydroxy-
8,11,13-abietatrien-7-one (Matsushita et al., 2005) as the
substance. It is noteworthy that DDA possesses a basic
skeleton and an aromatic moiety similar to carnosic acid
(Fig. 1), so it has been modified to some antioxidant
derivatives with excellent free radical scavenging activity
(Esteves and Narender, 2001; Gigante et al., 2003; Justino
et al., 2006).
with Cu2? and Fe2?
.
Keywords Dehydrodeisopropylabietate ꢀ
Ion chelation activity ꢀ Antioxidant
For antioxidants, three main mechanisms were proposed
based on the recent antioxidant theory (Wright et al., 2001;
Leopoldini et al., 2004). The H-atom transfer mechanism,
through which a free radical R• removes a hydrogen atom
from the antioxidant (ArOH):
Rꢁ þ ArOH ! RH þ ArOꢁ
K. Wang ꢀ H. Wang ꢀ Y. Pan (&)
And the one-electron transfer mechanism, in which one
of the antioxidant can give an electron to the free radical:
Key Laboratory for the Chemistry and Molecular Engineering
of Medicinal Resources (Ministry of Education of China),
School of Chemistry & Chemical Engineering of Guangxi
Normal University, Guilin 541004, People’s Republic of China
e-mail: panym2004@yahoo.com.cn
Rꢁ þ ArOH ! Rꢂ þ ArOHꢁþ
In the above two mechanisms, the radicals could be
stable so that the chain radical reactions were prevented or
delayed arising from both reactions. Another antioxidant
mechanism is based on the ability of some of these
compounds to chelate transition metals ions (especially
K. Wang ꢀ X. Liu ꢀ X. Yi ꢀ Y. Zhang
Department of Material and Chemical Engineering,
Guilin Institute of Technology, Guilin 541001,
People’s Republic of China
123

Med Chem Res (2012) 21:2494–2500
2495
well as its chelation activity on Cu2? and Fe2? using
fluorescence quenching method.
Results and discussion
Starting from DDA according to the literature procedure
(Esteves et al., 1999; Wada et al., 1985; Fonseca et al., 2004),
methyl dehydrodeisopropylabietate (compound 2) was syn-
thesized through methylation by freshly distilled dimethyl
sulfite in acetone. Then bromination was conducted with
NBS (N-bromosuccinimide) in dark place to obtain methyl
12-bromo dehydrodeisopropylabietate (compound 3). Based
on this, methyl 12-bromo 7-oxo dehydrodeisopropylabietate
(compound 4) was prepared through carbonylation from
compound 3 using CrO3 at low temperature. Subsequently,
nitration was completed in the condition of mixed acid
(HNO3/H2SO4) in cold traps and methyl 12-imino-13-
nitro-7-oxo dehydrodeisopropylabietate (compound 5) was
prepared. Finally, the coupling of methyl 12-bromo-13-
nitro-7-oxo dehydrodeisopropylabietate with aliphatic or
aromatic primary amine by Ullmann condensation reaction
produced a series of methyl 12-imino-13-nitro-7-oxo dehy-
drodeisopropylabietate derivatives. The melting point and
yields of all compounds 6 are given in Table 1. Using the
aliphatic primary amine as the substrates, the reaction pro-
duced good yields (80.1–92.3%) and the work-up after the
completion of this reaction is very simple. The mixture was
added to ice water and a lot of solid was precipitated, filtered,
washed, and then dried. The solid was recrystallized
from ethanol and crystals could be obtained. However,
the products of methyl 12-bromo-13-nitro-7-oxo dehy-
drodeisopropylabietate with aromatic primary amine could
not be obtained through crystallization directly, so the
products should be purified by silica gel column chroma-
tography using petroleum ether/ethyl acetate (10:1, V/V) as
the eluent with the yield of 75.1–79.5%.
Fig. 1 Molecular structure of DDA, carnosic acid, and catechol
derived from abietic acid
iron and copper), which gives rise to stable complexes that
entrap metals (Jovanovic et al., 1998; Leopoldini et al.,
2006). Metals ions in human body could catalyze
biomolecular oxidations especially the conversion of less
reactive species such as H2O2 or lipid peroxides into more
reactive ones such as hydroxyl radical (OH•) or peroxyl/
alkoxyl radicals through Feton reaction or Haber–Weiss
reaction. So the role of iron and other transition metals in
catalyzing free radical reactions, and the safe sequestration
of such metals in non-redox-active forms can be regarded
as a component of the antioxidant defense network
(Halliwell and Gutteridge, 1990; Halliwell, 2009).
During the last few years, some studies about antioxi-
dant has been made by our group (Pan et al., 2007a, b,
2008, 2009). In our opinion, most of the antioxidants
reported play their protective role through H-atom transfer
mechanism and one-electron transfer mechanism, such as
DDA derivatives with analogous structure of carnosic acid
(Esteves and Narender, 2001; Gigante et al., 2003). How-
ever, antioxidants through transition metals chelate ions
mechanism was not exhaustively studied in recently years,
especially DDA derivatives with transition metals ions
chelation activity has not been reported as we know. In this
article, to further explore the antioxidant activity of DDA
derivatives based on the mechanism of chelate transition
metals, we report a facile synthesis of 12-amine-13-nitro-7-
oxo dehydrodeisopropylabietate derivatives (Scheme 1) as
Scheme 1 Synthetic route of
7-oxo-12-amine-13-nitro
dehydrodeisopropylabietate
Br
(CH3)2SO4
NBS
CrO3
derivatives
Rosin
COOH
1
COOCH3
COOCH3
3
2
Br
NHR
Br
NO2
NO2
88%HNO3
H2SO4
R-NH2, DMF
K2CO3, CuCl,
O
O
O
COOCH3
COOCH3
COOCH3
5
4
6
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Med Chem Res (2012) 21:2494–2500
metal concentration caused the decrease in the peak
amplitude and this great variation in the fluorescence
spectrum suggests the formation of the 6h–Cu2? and 6h–
Fe2? complex. With these fluorescence quenching effect
conditions in hand, the binding constants (KA) were esti-
mated from the fluorescence quenching spectral data using
Stern–Volmer curves involving plots of the inverse of
Cu2?/Fe2? concentrations against the inverse of changes in
their respective fluorescence spectrum (Bermejo et al.,
2008; Xu and Wang, 2006). The following equation was
used to calculate the binding constants from these plots:
Table 1 Physicochemical property of compounds 6a–6k
Compounds R-moiety
Molecular m.p. (ꢁC)
weight
Yield
(%)
6a
6b
6c
6d
6e
6f
CH3-
359.40
373.42
387.45
387.45
401.48
401.48
389.42
388.44
421.47
435.49
191.8–192.6 82.4
190.4–191.9 83.9
182.4–183.6 84.2
174.1–174.8 87.2
134.6–135.5 80.1
234.8–235.3 92.3
138.0–138.7 89.7
185.4–186.1 83.9
172.8–173.0 75.1
149.7–150.1 78.3
152.4–153.0 79.5
C2H5-
CH3CH2CH2-
(CH3)2 CH-
CH3(CH2)3-
(CH3)3 C-
OH CH2CH2-
CH2CH2NH2-
C6H5-
6g
6h
6i
F0=F ¼ 1 þ Kqs0cðQÞ ¼ 1 þ KAcðQÞ
where F0 is the fluorescence intensity of compounds 6
without any metal ion, F is the fluorescence intensity of
mixture of compounds 6 with the increase of the metal
concentration of the metal ion, c(Q) is the concentration of
Cu2?/Fe2?, and KA is the binding constants.
6j
p-CH3–C6H4-
6k
p-CH3O–C6H4- 451.49
The binding constants (KA) of methyl 12-imino-13-
nitro-7-oxo dehydrodeisopropylabietate derivatives are
shown in Table 2. All the derivatives showed metals ion
chelation ability with the KA of the 102 L mol-1 order of
The crystal structure of compound 6b has been deter-
mined by X-ray diffraction and is shown in Fig. 2. Rings A
(atoms C9–C14) and rings B (atoms C5–C10) demonstrate
a trans ring junction, with two methyl groups in the axial
positions of the six-membered rings. The torsion angles
display classical chair and half-chair skeletons for rings A
and B, respectively. The crystal structure is stabilized by
weak intermolecular C–HꢀꢀꢀO and N–HꢀꢀꢀO interactions.
We then explored the metals ion chelation ability with
Cu2? and Fe2? in DMF/H2O solutions of the pure com-
pounds 6a–6k as described by Bermejo et al., 2008 with a
little modification. Take 6h for example, the fluorescence
quenching effect chelated with Cu2? and Fe2? are shown in
Fig. 3, the excitation peak of 6h can be recorded at 337 nm
that are generally ascribed to p ? p* electronic transitions
from the conjugated aromatic system. The increase of the
magnitude. The KA (Fe2?) were bigger than KA (Cu2?
)
indicating that the compounds showed more activity metals
ion chelation ability with Fe2? than Cu2? except for 6f.
Compound 6f has the strongest chelation activity with
Cu2?, while 6h has the strongest chelation activity with
Fe2?, respectively. However, from the factors of electronic
effect, steric hindrance, and chain length of substituting
group, respectively, it is difficult to find a relationship
between the chelation ability and the structure compounds
6. This could be due to the chelation activity of compounds
6 which were not determined by single factor but by the
synergistic effect of all these factors.
Fig. 2 X-ray crystal structure and packing diagram of compound 6b
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Med Chem Res (2012) 21:2494–2500
2497
400
400
300
200
100
0
C(Fe2+) Increased
1.20
1.15
1.10
1.05
C(Cu2+) Increased
1.25
1.20
1.15
1.10
1.05
350
300
250
200
150
100
50
0.0 0.2 0.4 0.6 0.8 1.0 1.2
Concentration(Cu2+ )/(10-3M)
0.0 0.2 0.4 0.6 0.8 1.0 1.2
Concentration (Fe2+)/(10-3M)
0
-50
250
300
350
400
450
250
300
350
400
450
Wavelength (nm)
Wavelength (nm)
Fig. 3 Fluorescence quenching effect of compound 6f and the Stern–Volmer curves chelated with Cu2? and Fe2?
Table 2 Fluorescence parameter and chelation to Cu2?/Fe2? of
compounds 6a–6k
analysis was done using RF-5301PC (SHIMADZU Scien-
tific Instruments, Inc., Japan).
Compound
kex
(nm)
kem
(nm)
KA (L mol-1)/
KA (L mol-1)/
(Cu2?
)
(Fe2?
)
Synthesis
6a
6b
6c
6d
6e
6f
279
283
280
263
284
264
280
261
286
283
285
330
331
331
338
322
340
330
337
330
316
317
107.0
81.3
186.0
138.3
135.7
168.3
181.7
103.6
108.0
305.9
106.9
122.7
165.0
(a) General procedure for the preparation of 6a–6h:
compound 5 was synthesized through 4 steps starting
from DDA, which were prepared according to the
literature procedure (Esteves et al., 1999; Wada et al.,
1985; Fonseca et al., 2004). The compound 5
(2.5 mmol), potassium carbonate (1 mmol), cuprous
chloride (2 mmol) were added to 15 mL DMF. After
stirring for 5–10 min, alicyclic amine (2.5 mmol) was
added drop-wise. The resultant solution was stirred
for 3–4 h at 100ꢁC (monitored by TLC), and then
plenty of ice water was added, a lot of orange–yellow
solid was precipitated, filtered, washed with water,
and then dried. The solid was recrystallized with
ethanol and pale orange–yellowish crystals were
obtained.
61.7
102.9
137.2
175.6
70.3
6g
6h
6i
97.6
60.7
6j
60.7
6k
89.2
Experimental
Reagents and apparatus
(b) General procedure for the preparation of 6i–6k:
compound
All chemicals were purchased from China National Med-
icine Group Shanghai Corporation (Shanghai, China). All
chemicals and solvents used were of analytical grade. The
1H-NMR and 13C-NMR spectra were carried out by the
instrument NMR (BRUKER AVANCE 500, BRUKER
company, Switzerland), and the mass spectral studies were
done using BRUKER ESQUIRE HCT instrument (BRU-
KER DALTON company, USA). Elemental analyses were
determined in the apparatus Carlo Erba model 1106 (Carlo
Erba company, Italy). Melting points were determined on a
WRS-IA apparatus (Shanghai Precision & Scientific
Instrument Co,. Ltd) without correction. Fluorescence
5
(2.5 mmol), potassium carbonate
(1 mmol), cuprous chloride (2 mmol) were added
to 15 mL DMF. After stirring for 5–10 min, aro-
matic amine (2.5 mmol) was added drop-wise. The
resultant solution was stirred for 3–4 h at 100ꢁC
(monitored by TLC), then plenty of ice water was
added. A lot of orange–yellow solid was precipi-
tated, filtered, and washed with water. Subsequently,
the solid obtained was purified by silica gel column
chromatography with petroleum ether/ethyl acetate
(20:1, V/V) as the eluent. Yellow powders of 6i–6k
were obtained.
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Med Chem Res (2012) 21:2494–2500
Spectra data for representative compounds
1.70–1.76 (2H, m, 2-H2), 1.83–1.87 (3H, m, 1-H2, 3-Ha),
2.28–2.36 (2H, m, 3-Hb, 6-Ha), 2.63–2.68 (2H, m, 6-Hb,
5-H), 3.91 (1H, q, J = 12.6, –CH(CH3)2), 3.68 (3H, s,
COOCH3), 6.71 (1H, s, 11-H), 8.27 (1H, s, N–H), 8.88
(1H, s, 14-H). 13C NMR (CDCl3, 125 Mz) d: 16.47, 18.01,
22.27, 23.32, 36.37, 36.88, 37.28, 38.03, 42.78, 44.25,
46.63, 52.16, 107.35, 119.63, 128.47, 130.80, 146.91,
161.86, 177.39, 194.70. EI-MS(m/z): 389.21 [M ? H]?;
Anal. Calcd. for C21H28N2O5: C, 64.93; H, 7.27; N, 7.21%.
Found: C, 65.16; H, 7.40; N, 6.95%.
Methyl 12-methylamino-13-nitro-7-oxo
dehydrodeisopropylabietate (6a)
1H-NMR (CDCl3, 500 Hz) d: 1.31 (3H, s, 4-CH3), 1.37
(3H, s, 10-CH3), 1.71–1.77 (2H, m, 2-H2), 1.80–1.88 (3H,
m, 1-H2, 3-Ha), 2.33–2.38 (2H, m, 3-Hb, 6-Ha), 2.67–2.69
(2H, m, 6-Hb, 5-H), 3.11(3H, d, J = 5.1, N-CH3), 3.68
(3H, s, –OCH3), 6.70 (1H, s, 11-H), 8.36 (1H, d, J = 5.1,
N–H), 8.91 (1H, s, 14-H). 13C NMR (CDCl3, 125 Hz) d:
16.63, 18.07, 23.43, 29.83, 36.51, 36.99, 37.42, 38.27,
42.96, 46.77, 52.28, 106.65, 120.19, 128.31, 131.26,
148.64, 162.33, 177.49, 194.40; EI-MS(m/z): 361.22
[M ? H]?; Anal. Calcd. for C19H24N2O5: C, 63.32; H,
6.71; N, 7.77%. Found: C, 63.48; H, 6.54; N, 7.92%.
Methyl 12-butylamino-13-nitro-7-oxo
dehydrodeisopropylabietate (6e)
1H-NMR (CDCl3, 500 Hz) d: 1.02 (3H, t, J = 7.25,
–NH(CH2)3CH3), 1.29 (3H, s, 4-CH3,), 1.49 (3H, s,
10-CH3), 1.49–1.54 (2H, m, –CH2CH3), 1.73–1.84 (7H, m,
–CH2CH2CH3, 1-H2, 2-H2, 3-Ha), 2.28–2.36 (2H, m, 3-Hb,
6-Ha), 3.37 (2H, dd, J = 7.25, –NHCH2–), 3.67 (3H, s,
–OCH3), 6.69 (1H, s, 11-H), 8.33 (1H, s, N–H), 8.87 (1H, s,
14-H). 13C NMR (CDCl3, 125 Mz) d: 16.63, 16.51, 17.9,
20.09, 23.32, 30.72, 36.40, 36.85, 37.31, 38.07, 42.8,
46.66, 52.2, 106.97, 119.80, 128.26, 130.86, 147.83,
162.05, 177.37, 194.79. EI-MS(m/z): 403.21 [M ? H]?;
Anal. Calcd. for C22H30N2O5: C, 65.65; H, 7.51; N, 6.96%.
Found: C, 65.31; H, 7.71; N, 7.10%.
Methyl 12-ethylamino-13-nitro-7-oxo
dehydrodeisopropylabietate (6b)
1H-NMR (CDCl3, 500 Hz) d: 1.30 (3H, s, 4-CH3) 1.36 (3H,
s, 10-CH3), 1.36 (3H, s, 10-CH3), 1.43 (3H, t, J = 6.85, N–
CH2CH3), 1.71–1.77 (2H, m, 2-H2,), 1.80–1.83 (3H, m,
1-H2, 3-Ha,), 2.30–2.38 (2H, m, 3-Hb, 6-Ha), 2.64–2.71
(2H, m, 6-Hb, 5-H), 3.43 (2H, q, J = 6.85, N–CH2), 3.68
(3H, s, COOCH3), 6.70 (1H, s, 11-H), 8.26 (1H, s, N–H),
8.9 (1H, s, 14-H). 13C NMR (CDCl3, 125 Hz) d: 14.13,
16.78, 17.94, 23.14, 36.50, 36.99, 37.41, 37.91, 38.21,
42.95, 47.04, 52.26, 107.03 (C-11), 120.41, 128.26, 131.23,
148.04, 162.53, 177.83, 195.02. EI-MS(m/z): 375.21
[M ? H]?; Anal. Calcd. for C20H26N2O5: C, 64.15; H,
7.00; N, 7.48%. Found: C, 64.02; H, 7.25; N, 7.36%.
Methyl 12-tert-butylamino-13-nitro-7-oxo
dehydrodeisopropylabietate (6f)
1H-NMR (CDCl3, 500 Hz) d: 1.28 (3H, s, 4-CH3), 1.34
(3H, s, 10-CH3), 1.54 (9H, s, –C(CH3)3), 1.49–1.54 (2H, m,
–CH2CH3), 1.70–1.75 (2H, m, 1-H2), 1.78–1.84 (3H, m,
2-H2, 3-Ha), 2.24–2.26 (1H, m, 3-Hb,), 2.30–2.35 (1H,
m,6-Ha), 2.61–2.68 (2H, m, 6-Hb, 5-H), 3.66 (3H, s,
–COOCH3), 6.95 (1H, s, 11-H), 8.61 (1H, s, N–H), 8.88
(1H, s, 14-H). 13C NMR (CDCl3, 125 Hz) d: 16.59, 18.16,
23.49, 29.68, 36.48, 37.13, 37.42, 38.11, 42.93, 46.76,
52.16, 52.29, 109.24, 119.48, 128.71, 131.66, 147.29,
161.02, 177.50, 194.85. EI-MS(m/z): 403.22 [M ? H]?;
Anal. Calcd. for C22H30N2O5: C, 65.65; H, 7.51; N, 6.96%.
Found: C, 65.35; H, 7.61; N, 7.16%.
Methyl 12-propylamino-13-nitro-7-oxo
dehydrodeisopropylabietate (6c)
1H-NMR (CDCl3, 500 Hz) d: 1.11 (3H, t, J = 7.4 Hz,
–NCH2CH2CH3), 1.30 (3H, s, 4-CH3), 1.37 (3H, s, 10-CH3),
1.69–1.77 (2H, m, 2-H2), 1.80–1.85 (5H, m, –NHCH2CH2CH3,
2-H2, 3-Ha), 2.30–2.38 (2H, m, 3-Hb, 6-Ha), 2.64–2.72 (2H, m,
6-Hb, 5-H), 3.35 (2H, q, J = 12.3, –NCH2–), 3.69 (3H, s,
–OCH3), 6.70 (1H, s, 11-H), 8.35 (1H, s, N–H), 8.9 (1H, s, 14-H).
13C NMR (CDCl3, 125 Hz) d: 11.55, 16.61, 18.80, 23.13,
23.42, 36.51, 37.42, 38.21, 42.94, 45.07, 46.82, 52.28, 107.08,
120.03, 128.42, 131.08, 147.94, 162.13, 177.51, 194.88.
EI-MS(m/z): 389.22 [M ? H]?; Anal. Calcd. for C21H28N2O5:
C, 64.93; H, 7.27; N, 7.21%. Found: C, 64.73; H, 7.12; N, 7.56%.
Methyl 12-(2-hydroxyethyl)-amino-13-nitro-7-oxo
dehydrodeisopropylabietate (6g)
1H-NMR (CDCl3, 500 MHz) d: 1.29 (3H, s, 4-CH3), 1.35
(3H, s, 10-CH3), 1.77–1.79 (2H, m, 2-H2,), 1.82–1.83 (3H,
m, 1-H2, 3-Ha), 2.32 (2H, dd, J = 4.68, 3-Hb, 6-Ha),
2.51 (1H, s, –OH), 2.64–2.71 (2H, m, 6-Hb, 5-Ha), 3.57
(2H, q, J = 5.10, –NHCH2–), 3.99 (2H, q, J = 5.10,
–NHCH2CH2–), 3.68 (3H, s, COOCH3), 6.75 (1H, s, 11-H),
8.55 (1H, s, N–H), 8.77 (1H, s, 14-H). 13C NMR (CDCl3,
Methyl 12-isopropylamino-13-nitro-7-oxo
dehydrodeisopropylabietate (6d)
1H-NMR (CDCl3, 500 MHz) d: 1.29 (3H, s, 4-CH3), 1.35
(3H, s, 10-CH3), 1.38 (6H, d, J = 12.6, –CH(CH3)2),
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Med Chem Res (2012) 21:2494–2500
2499
125 Mz) d: 16.46, 17.9, 23.21, 36.33, 36.80, 37.27, 38.08,
42.71, 45.09, 46.61, 52.19, 60.59, 107.27, 119.26, 128.47,
130.97, 147.91, 162.16, 177.63, 195.10. EI-MS(m/z):
391.16 [M ? H]?; Anal. Calcd. for C20H26N2O6: C, 61.53;
H, 6.71; N, 7.18%. Found: C, 61.28; H, 6.94; N, 7.30%.
EI-MS(m/z): 437.22 [M ? H]?; Anal. Calcd. for
C24H26N2O5: C, 68.79; H, 6.47; N, 6.42%. Found: C,
68.60; H, 6.57; N, 6.51%.
Methyl 12-(p–methoxyphenyl)-amino-13-nitro-7-oxo
dehydrodeisopropylabietate (6k)
Methyl 12-(2-aminoethyl)-amino-13-nitro-7-oxo
dehydrodeisopropylabietate (6h)
1H-NMR (CDCl3, 500 Hz) d: 1.18 (3H, s, 4-CH3) 1.30
(3H, s, 10-CH3), 1.43–1.50 (1H, m, 1-Ha), 1.60–1.76 (4H,
m, 1-Hb, 2-H2, 3-Ha,), 1.93 (1H, d, J = 12.58, 3-Hb),
2.27–2.36 (H, m, 6-Ha), 2.59–2.68 (2H, m, 6-Hb, 5-H),
3.65 (3H, s, COOCH3), 3.87 (3H, s, ph-OCH3), 6.90 (1H, s,
11-H), 6.99–7.01 (2H, d, J = 8.83, 30-H and 50-H),
7.19–7.12 (2H, d, J = 8.83, 20-H and 60-H), 8.90 (1H, s,
14-H), 9.67 (1H, s, N–H). 13C NMR (CDCl3, 125 Hz) d:
16.56, 17.59, 23.23, 36.45, 36.59, 37.41, 38.10, 42.87,
46.72, 52.31, 52.55, 109.27, 115.17, 121.37, 126.95,
128.17, 130.28, 131.49, 147.05, 158.37, 161.75, 177.52,
194.92. EI-MS(m/z): 453.20 [M ? H]?; Anal. Calcd. for
C25H28N2O6: C, 66.36; H, 6.24; N, 6.19%. Found: C,
66.51; H, 6.43; N, 5.85%.
1H-NMR (CDCl3, 500 Hz) d: 1.22 (6H, t, J = 7.04,
–CH2CH3),1.30 (3H, s, 4-CH3), 1.36 (3H, s, 10-CH3),
1.69–1.76 (2H, m, 1-H2), 1.84–1.88 (3H, m, 2-H2, 3-Ha),
2.29–2.37 (2H, m, 3-Hb, 6-Ha), 2.64–2.72 (2H, m,6-Hb,
5-H), 3.31 (4H, q, J = 7.04, –CH2CH3), 3.68 (3H, s,
COOCH3), 6.90 (1H, s, 11-H), 8.36 (1H, s, 14-H). 13C
NMR (CDCl3, 125 Hz) d: 12.46, 16.53, 18.12, 23.54,
36.49, 37.03, 37.40, 38.04, 43.38, 45.91, 48.78, 52.27,
113.18, 121.54, 127.14, 139.09, 147.56, 159.19, 177.52,
194.99. EI-MS(m/z): 391.22 [M ? H]?; Anal. Calcd. for
C20H27N3O5: C, 61.68; H, 6.99; N, 10.79%. Found: C,
61.96; H, 6.79; N, 10.71%.
Methyl 12-phenyl-amino-13-nitro-7-oxo
dehydrodeisopropylabietate (6i)
Metals ion chelation ability
The metals ion chelation ability of the title compound was
evaluated according to the method of Bermejo et al., 2008
and Perez et al., 2009 with little modification. Different
volume of CuCl2/FeCl2 solution [10-3 mol/L, DMF/H2O
(1:1, V/V)] was added to the title compound solution
(10-3 mol/L, DMF) and then distilled to the appropriate
concentration with DMF. The mixture was mixed thor-
oughly and the fluorescence intensity of different solution
was measured with slit of 5 nm.
1H-NMR (CDCl3, 500 Hz) d: 1.22 (3H, s, 4-CH3,) 1.33
(3H, s, 10-CH3), 1.51–1.58 (1H, m, 1-Ha), 1.71–1.79 (4H,
m, 1-Hb, 2-H2, 3-Ha,), 1.99 (1H, d, J = 12.5, 3-Hb), 2.35
(H, m, 6-Ha), 2.67 (2H, m, 6-Hb, 5-H), 3.68 (3H, s,
COOCH3), 7.12 (1H, s, 11-H), 7.33–7.35 (3H, m, 30-H,
40-H and 50-H), 7.49–7.52 (2H, m, 20-H and 60-H), 8.94
(1H, s, 14-H), 9.81 (1H, s, N–H). 13C NMR (CDCl3, 125
Mz) d: 16.46, 17.87, 23.19, 36.35, 36.53, 37.32, 38.05,
42.80, 46.62, 52.39, 109.41, 121.75, 124.57, 126.56,
128.10, 130.06, 131.91, 137.83, 145.63, 161.54, 177.45,
194.39. EI-MS(m/z): 423.19 [M ? H]?; Anal. Calcd. for
C24H26N2O5: C, 68.23; H, 6.20; N, 6.63%. Found: C,
68.41; H, 6.32; N, 6.33%.
Conclusions
Compounds 6 were synthesized through coupling of methyl
12-bromo-13-nitro-7-oxo dehydrodeisopropylabietate with
aliphatic or aromatic primary amine by Ullmann conden-
sation reaction. The fluorescence quenching results indi-
cated that each compound showed obvious chelation
activity with the KA of the 102 L mol-1 order of magni-
tude. Compound 6f has the strongest chelation activity with
Cu2? while 6h has the strongest chelation activity with
Fe2?, respectively. It is difficult to find a relationship
between the chelation abilities and the structures of com-
pounds 6. This could be due to the chelation activity of
compound 6 which was not determined by single factor
of electronic effect, steric hindrance or chain length of
substituting group, but by the synergistic effect of all these
factors. Further experiments were needed to elucidate their
metal chelation mechanism of compounds 6. However, the
Methyl 12-(p-methylphenyl)-amino-13-nitro-7-oxo
dehydrodeisopropylabietate (6j)
1H-NMR (CDCl3, 500 Hz) d: 1.22 (3H, s, 4-CH3) 1.33
(3H, s, 10-CH3), 1.51–1.55 (1H, m, 1-Ha), 1.72–1.80 (4H,
m, 1-Hb, 2-H2, 3-Ha,), 1.99 (1H, d, J = 12.7, 3-Hb),
2.31–2.39 (H, m, 6-Ha), 2.44 (3H, s, ph-CH3), 2.63–2.71
(2H, m, 6-Hb, 5-H), 3.68 (3H, s, COOCH3), 7.07 (1H, s,
11-H), 7.19–7.21 (2H, d, J = 8.15, 30-H and 50-H),
7.29–7.30 (2H, m, J = 8.15, 20-H and 60-H), 8.93 (1H, s,
14-H), 9.75 (1H, s, N–H). 13C NMR (CDCl3, 125 Hz) d:
16.58, 17.98, 21.06, 23.27, 36.46, 36.62, 37.42, 38.14,
42.9, 46.72, 52.30, 109.44, 121.57, 124.78, 128.15, 130.53,
131.42, 135.03, 136.57, 146.36, 161.72, 177.51, 194.88.
123

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Acknowledgments This study was supported by 973 projects
(2011CB512005), Guangxi Natural Science Foundation of China
(2011GXNSFD018010 and 2010GXNSFF013001), The projects of
Key Laboratory for the Chemistry and Molecular Engineering
of Medicinal Resources (Guangxi Normal University) Ministry of
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Small Highland Foundation (0808), and The Scientific Research and
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