Synthesis and biological evaluation of a series of 6,7-dimethoxy-1-(3,4- dimethoxybenzyl)-2-substituted tetrahydroisoquinoline derivatives

Article abstract of DOI:10.2174/157340612801216337

Multidrug resistance in cancer is a major cause of failure in cancer chemotherapy. In search of new compounds with strong reversal activity and simple molecular structure, we have synthesized a series of compounds in which different substituents were linked to the 2-position of the 6,7-dimethoxy-1-(3, 4-dimethoxybenzyl)-tetrahydroisoquinoline system. Compounds were analyzed for their cytotoxicity by MTT in K562 cell line in vitro, all of the derivatives exhibited little cytotoxic activity. In the meantime, these compounds were evaluated by MTT in K562/A02 cell line in vitro, 6e, 6h and 7c exhibited similar or more potent activities than verapamil with the IC₅₀ values at 0.66, 0.65 and 0.96μM, and with the ratio factor of 24.13, 24.50 and 16.59, respectively.

Full text of DOI:10.2174/157340612801216337

Medicinal Chemistry, 2012, 8, 711-716
711
Synthesis and Biological Evaluation of a Series of 6,7-dimethoxy-1-(3,4-
dimethoxybenzyl)-2-substituted Tetrahydroisoquinoline Derivatives
Zhi-hong Zou1,2,#, Xiao-bu Lan1,3,#, Chun-lei Tang1, Xiao-yun Zhu1, Bao-min Liu1, Hai Qian1,*,
Wen-long Huang1,* and Yun-man Li4
1Centre of Drug Discovery, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing, Jiangsu 210009, China
2Department of Pharmaceutical Engineering, College of Chemistry and Chemical Engineering, Southeast University,
Nanjing 210009, China
3Department of Organic Chemistry & Medicinal Chemistry, Guangxi Medical University, 22 Shuangyong Road,
Nanning, Guangxi, 530021, China
4Department of Pharmacology, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing, Jiangsu 210009, China
Abstract: Multidrug resistance in cancer is a major cause of failure in cancer chemotherapy. In search of new compounds
with strong reversal activity and simple molecular structure, we have synthesized a series of compounds in which differ-
ent substituents were linked to the 2-position of the 6,7-dimethoxy-1-(3,4-dimethoxybenzyl)- tetrahydroisoquinoline sys-
tem. Compounds were analyzed for their cytotoxicity by MTT in K562 cell line in vitro, all of the derivatives exhibited
little cytotoxic activity. In the meantime, these compounds were evaluated by MTT in K562/A02 cell line in vitro, 6e, 6h
and 7c exhibited similar or more potent activities than verapamil with the IC50 values at 0.66, 0.65 and 0.96μM, and with
the ratio factor of 24.13, 24.50 and 16.59, respectively.
Keywords: Multidrug resistance, anticancer, tetrahydroisoquinoline.
INTRODUCTION
placed by nitro-vinyl amidino or N-nitro-guanyl groups, to
form another class of potent multidrug resistance reversal
agents. And their preliminary biological activities were
evaluated. We anticipated the designed compounds exhibit-
ing MDR reversal activities and anti-tumor activities.
Multidrug resistance (MDR) induced by anti-tumor
agents treatment is a significant obstacle to the success of
chemotherapy in many cancers [1, 2]. There has been rising
interest in the discovery and development of novel small
molecules to reverse MDR. Verapamil, the calcium channel
blocker, is the most widely used agent to reverse MDR [3].
However, verapamil has been restricted as MDR reversal
agent due to its risks in cardiovascular system at effective
dose [4]. Consequently, synthesis and screening of novel
MDR reversing agents with higher selective activity and low
cytotoxicity are essential. Tetrandrine (Fig. 1), a complex
natural alkaloid extracted from Radix Stephaniae Tetrandrae
root, displayed antioxidant [5], anti-inflammatory [6], anti-
allergic [7] and anti-tumor [8] activities. In our previous
work [9-12], a series of 6,7-dimethoxy-1-(3,4-dimethoxy-
benzyl)-1,2,3,4-tetrahydroisoquinoline derivatives derived
from tetrandrine exhibited potent MDR reversing activities
against cancer cells, especially HZ08 (Fig. 1). HZ08, a well
acknowledged P-glycoprotein inhibitor [9,11], possesses
superior activity in reversing MDR cell lines induced by
various anti-tumor agents. In this paper, the cyano-guanyl
RESULTS AND DISCUSSION
Synthesis
We designed and synthesized a series of tetrahydroiso-
quinoline derivatives, including 12 compounds which are the
combination of 6,7-dimethoxy-1-(3,4-dimethoxybenzyl)-
1,2,3,4-tetrahydroisoquinoline with nitro-vinyl amidino or
N-nitro-guanyl groups. The synthetic routes of compounds
6a-6h and 7a-7d were outlined in Scheme 1. The compound
1 was treated with formaldehyde by Pictet-Spengler reaction
to afford 3a [13], and 2b-2d were obtained from compound
1 by Bischler-Napieralski reaction with appropriate substi-
tuted acetic acid at 190°C under N2 environment [14]. Com-
pounds 2b-2d reacted with POCl3 in toluene under reflux to
provide dihydroisoquinoline 1-substituted derivatives 3b-3d.
Compounds 3a-3d reacted with KBH4 in methanol to afford
1-substituted derivatives 4a-4d. Next, the reaction at the N-
position of compounds 5a-5d was achieved with 1,1-
dimethylthio-2-nitroethene [15] in toluene, respectively. Re-
action of the intermediate 5a-5d with substituted amines in
toluene under reflux gave compounds 6a-6h. Furthermore,
the reaction at the 2-position of compounds 4a-4d with
methyl N'-nitrocarbamimidothioate are compounds 7a-7d
[16] in ethanol under reflux.
group
at
2-position
of
6,7-dimethoxy-1-(3,4-
dimethoxybenzyl)-1,2,3,4-tetrahydroisoquinoline was re-
# These authors contributed equally to this work.
*Address Correspondence to these authors at the Centre of Drug Discovery,
China Pharmaceutical University, 24 Tongjiaxiang, Nanjing, Jiangsu
210009, China; Tel: +86-25-83271302; Fax: +86-25-83271480; E-mails:
qianhai24@163.com (H. Qian) or ydhuangwenlong@126.com (W. Huang).
1875-6638/12 $58.00+.00
© 2012 Bentham Science Publishers

712 Medicinal Chemistry, 2012, Vol. 8, No. 4
Zou et al.
O
O
O
5
8
4
N
O
6
7
3
O
H
N
2
N
O
O
1
N
N
CN
O
O
O
Tetrandrine
HZ08
Fig. (1). Structure of Tetrandrine and HZ08.
H3CO
H3CO
H3CO
H3CO
H3CO
H3CO
H3CO
i
ii
iii
NH2
NH
R1
N
H3CO
NH
O
R1
3a-3d
R1
4a-4d
1
2a-2d
H3CO
H3CO
H3CO
iv
H
v
H
N
N
NO2
NO2
H3CO
R1 SCH3
R1 R2
5a-5d
6a-6h
H3CO
H3CO
vi
N
N
NO2
R1 R2
7a-7d
NH2
6a
6b
R1= H
R1= H
R2=
R2=
NH(CH2)7CH3
NH(CH2)2Ph
R2=
R2=
7a
7b
R1= H
R1=
O
O
O
NH2
NH2
6c
R1=
R1=
NH(CH2)7CH3
NH(CH2)2Ph
R2=
R2=
O
O
6d
O
O
R2=
R2=
7c
R1=
R1=
O
O
6e
6f
R1=
R1=
NH(CH2)7CH3
R2=
NH(CH2)2Ph
R2=
R2=
NH2
7d
NH(CH2)3CH3
6g
6h
R1=
R1=
O
H
N
R2=
O
Scheme 1. Synthesis of compounds 6a-6h and 7a-7d. Reagents and conditions: (i) R1CH3COOH, N2, 190°C, 3h; (ii) POCl3, toluene, N2, 110°C, reflux, 2.5h;
(iii) KBH4, diethylamine, methanol, rt, 24h; (iv) 1, 1 -dimethylthio-2-nitroethene, toluene, reflux, 30-50h; (v) R2NH2, toluene, reflux, 14-72h; (vi) methyl N'-
nitrocarbamimidothioate, ethanol, reflux, 18-72h.
Cytotoxicity Assay
mosphere. For the log phase cells were implanted in 96-well
plates in the density of 1ꢀ105 cells/mL, the original medium
was removed and the cells were incubated in the 160 mL
RPMI 1640 containing no serum for 30 min. With 10 μg/mL
tested compounds (adriamycin, compounds 6a-6h and 7a-
7d) or the same volume PBS as vehicle control were added
to incubate at 37°C for 48h. During the next 4 h incubation
Human chronic myelogenous leukemia cells: The K562
cell line was obtained from the erythroleukemia type (Insti-
tute of Hematology Chinese Academy of Medical Sciences,
Tianjin, China). Cells were grown in RPMI 1640 containing
10% fetal calf serum at 37°C in a 5% CO2 humidified at-

Synthesis and Biological Evaluation
Medicinal Chemistry, 2012, Vol. 8, No. 4 713
Table 1. Cytotoxicity to K562 Cells as Determined by MTT
Table 2. MDR Reversal Activity Tested Compounds in
K562/A02 Cell Lines by MTT Assay
Assay ( , n=3) Dose: 10 μg/ml
x
IC50 of Adriamycin and Ratio Factor (RF)
Compound
Compound
Survival (%)
(10μg/mL)
IC50*
RF
verapamil
HZ08
6a
98.3*
93.5*
90.6*
93.9*
97.2*
95.2*
90.0*
87.5*
89.8*
95.0*
95.9*
95.9*
88.0*
99.4*
verapamil
0.88 a
0.73 a
1.68 a
23.31 a
1.79 a
12.87 a
0.66 a
1.82 a
3.97 a
0.65 a
18.62 a
1.76 a
0.96 a
1.69 a
15.93 b
18.10ꢀ
21.82ꢀ
9.48ꢀ
0.68ꢀ
8.89ꢀ
1.23ꢀ
24.13ꢀ
8.75ꢀ
4.01ꢀ
24.50ꢀ
0.85ꢀ
9.05ꢀ
16.59ꢀ
9.42ꢀ
-
HZ08
6a
6b
6c
6b
6c
6d
6e
6d
6e
6f
6g
6f
6h
6g
6h
7a
7b
7c
7a
7b
7c
7d
* P<0.005, determined by X2 test.
7d
-
the cells were determined by MTT assay [17]. The cells were
exposed to MTT (5 mg/mL, sigma) and the resulting forma-
zan crystals were dissolved in 200 μM DMSO, followed by
measuring the absolute fluorescence value at ꢀ=492 nm on a
microplate reader (Thermo, USA). Assays were performed in
duplicate, with at least three separate experiments. Cytotox-
icity rate was expressed as survival, which was calculated
using (mean absolute fluorescence value of the treated
group/the mean absolute fluorescence value of control) ꢁ100
(%). The results were showed in Table 1. The cell survival of
the tested compounds was over 85%. It indicated that all
tested compounds were not toxic to K562 cancer cell lines
thus and cannot be regarded as anti-tumor agents.
a IC50 of adriamycin in the presence of tested compounds;
b IC50 of adriamycin alone (control IC50);
* IC50 of adriamycin (μg/mL), , n=3, reversal adriamycin.
x
verapamil and HZ08. Compound 6h, with a 1-positioned 1-
naphthylmethyl group and 2-positioned 3,4-dimethoxy-
phenylethyl linked by nitro-vinyl amidino, exhibited the
most potency with the IC50 values at 0.65μM and the RF of
24.50 in K562/A02 cells. Compounds 6e and 7c also exhib-
ited high potent with the IC50 value at 0.65μM and 0.96μM,
and with the RF of 24.13 and 16.59, respectively. In com-
parison with HZ08, compounds 6c and 6e with 2-positioned
n-octyl group showed better anti-MDR activities, indicating
that the introduction of a long linear chain of fatty amine at
R2 may benefit to the anti-MDR effect. The activity could be
improved when the 3,4-dimethoxybenzyl group was replaced
by phenoxymethyl group (compounds 6e and 7c). addition-
ally, when the R1 was substituted by 1-naphthyl-methyl
group while R2 was replaced by 3,4-dimethoxy-
phenethylamino group at the meantime, the derivative 6h
also exhibited more potent than HZ08. As all the derivatives
were not toxic to K562 cancer cell lines under the dosage of
10 μg/ml, it can be attributed to the reversal agents that dis-
played a sensitizing effect on anti-tumor drugs, but not their
cytotoxic effect to tumor cells.
MDR Reversal Activity
MDR reversal activity of tested compounds (compounds
6a-6h and 7a-7d) was reported as IC50 values and ratio fac-
tor (RF) in the K562/A02 cell line (Institute of Hematology
Chinese Academy of Medical Sciences, Tianjin, China).
Cells were seeded into 96-well plates at 3ꢁ104 cells/well.
Various concentrations of adriamycin and the tested com-
pounds were gradually added and plates were incubated in
5% humidified incubator at 37°C for 48h. Finally, the MTT
assay was performed as mentioned before. IC50 values of
adriamycin (concentration resulting in 50% inhibition of cell
growth) were calculated in the presence of five concentra-
tions of the tested compounds (0.5μM, 1μM, 10μM, 20μM
and 50μM). The RF was calculated by the following equa-
tion: MDR ratio factor (RF) = IC50 (adriamycin alone) / IC50
(adriamycin + tested compound).
CONCLUSION
We have synthesized a series of nitro-vinyl amidino and
nitro-guanyl substituted 6,7-dimethoxy-1-(3,4-dimethoxy-
benzyl)-1,2,3,4-tetrahydroisoquinoline derivatives. The bio-
logical evaluation included two tumor cell lines, K562 and
As shown in Table 2, compounds 6e, 6h and 7c displayed
similar or more potent reversal activities in comparison with

714 Medicinal Chemistry, 2012, Vol. 8, No. 4
Zou et al.
drug-resistant K562/A02 cell lines. All synthesized com-
pounds displayed little cytotoxic effect in K562 cell line.
Some of these compounds (compounds 6e, 6h and 7c) exhib-
ited similar or more potent MDR reversal activities than
verapamil with IC50 values at 0.66μM, 0.65μM and 0.96μM,
and with the RF of 24.13, 24.50 and 16.59 in K562/A02 cell
line, respectively. So these three compounds could be chosen
as candidates for MDR reversal agents. Further studies on
separating the chiral enantiomers and the mechanism of ac-
tion of these three compounds are currently in progress and
the results will be reported in due course.
197°ꢀ. 1HNMR (CDCl3, 300M, ꢀppm) ꢀ: 2.50 (s, 3H, SCH3),
2.72-3.87 (m, 4H, C3-H, C4-H), 3.87 (s, 6H, 2ꢁOCH3), 4.17
(m, 2H, Ar-OCH2), 4.89 (t, 1H, C1-H), 6.52 (s, 1H,
CꢂCH(NO2)), 6.63, 6.66 (each s, 2H, C5-H, C8-H), 6.83-
7.30 (m, 5H, Ar-H); IR (KBr, ꢂ): 3451, 3034, 2972, 2935,
2874, 1665, 1611, 1599, 1555, 1519, 1432, 1356 cm-1; MS
(ESI, m/z): 417.1 (M+H, base peak).
6,7-dimethoxy-1-(1-naphthylmethyl)-2-(1-methylthio-2-
nitro)vinyl-1,2,3,4-tetrahydroisoquinoline (5d)
Following the procedure described for 5a from 4d, com-
pounds 5d was obtained as a yellow solid, 70%, mp 148-
150°ꢀ. 1HNMR (CDCl3, 300M, ꢀppm) ꢀ: 1.96 (s, 3H, SCH3),
2.95 (m, 2H, C4-H), 3.43 (s, 3H, C7-OCH3), 3.84 (s, 3H, C6-
OCH3), 3.66,4.08 (m, 4H, C3-H, Ar-CH2), 5.73 (t, 1H, C1-H),
5.93 (s, 1H, CꢂCH(NO2)), 6.62, 6.71 (each s, 2H, C5-H, C8-
H), 7.22-8.02 (m, 7H, Ar-H); IR (KBr, ꢂ): 3444, 3112, 2931,
2837, 1729, 1607, 1521, 1468, 1391, 1348 cm-1; MS (ESI,
m/z): 451.1 (M+H, base peak).
EXPERIMENTAL
The melting points were determined with an x4-type mi-
cro melting point apparatus (Beijing Optical Instrument Fac-
1
tory III) and were uncorrected. The H NMR spectra were
recorded on an ACF-300 Bruker spectrometer in d1-
chloroform. Tetramethylsilane (TMS) was used as the inter-
nal standard. The mass spectra were obtained with a
HP1100LC/MSD spectrometer with a direct inlet system at
70 eV. The IR spectra were recorded on a Nicolet Impact
410 infrared spectrometer (KBr disk). The elemental analysis
were obtained with a Carlo Erba 1106-type analyzer. Reac-
tions were monitored by TLC on Silica Gel 60 F254 (Qing-
dao Ocean Chemical Company, China) plates. Column
chromatography was performed with Silica Gel 100-200
(Qingdao Ocean Chemical Company, China).
6,7-dimethoxy-2-(1-n-octylamino-2-nitro)vinyl-1,2,3,4-
tetrahydroisoquinoline (6a)
A mixture of compound 5a (0.78g, 2.5mmol), n-octyl
amine (2.6g, 20mmol) and anhydrous toluene (15mL) was
stirred for 16h at 60-70°ꢀꢃꢄThe resultant solvent was con-
centrated under pressure. The residue was purified by col-
umn chromatography on silica gel (EtOAc-petroleum ether
1-1 v/v), and compound 6a was obtained as a white solid
6,7-dimethoxy-2-(1-methylthio-2-nitro)vinyl-1,2,3,4-
tetrahydroisoquinoline (5a)
1
0.52g, yield: 53%, mp 100-102°C. HNMR (CDCl3, 300M,
ꢀppm) ꢀ: 0.91 (t, 3H, J=6.0Hz, CH2CH3), 1.31-1.73 (m, 13H,
NHCH2, (CH2)6CH3), 2.92 (t, 2H, J=6.0Hz, C4-H),
3.37ꢅ(m, 2H, NHCH2), 3.55 (t, 2H, J=6.0Hz, C3-H), 3.89,
3.90 (s, 6H, 2ꢁOCH3), 4.35 (s, 2H, C1-H), 6.58 (s, 1H,
CꢂCH(NO2)), 6.62, 6.67 (each s, 2H, C5-H, C8-H)ꢁIR
(KBr, ꢂ): 3451, 2952, 2924, 2854, 1598, 1534, 1518, 1462,
1306 cm-1; MS (ESI, m/z): 392.1 (M+H, base peak); Anal.
Calcd. for C21H33N3O4ꢆC 64.42, H 8.50, N 10.73; Found: C
64.45, H 8.27, N 10.86.
A mixture of compound 4a (9.7g, 50mmol), 1,1-
dimethylthio-2-nitroethene (11.6g, 70mmol) in acetone
(100mL) was refluxed for 18h. Then the resultant mixture
was concentrated under reduced pressure and the residue was
re-dissolved in hot ethanol (50mL). The solvent was cooled
and filtered. The mother solution was concentrated under
pressure and the residue was purified by column chromatog-
raphy on silica gel (EtOAc-petroleum ether 2-1 v/v), and
compound 5a was obtained as a yellow solid 10.9g, yield:
1
70%, mp 130-132°ꢀ. HNMR (CDCl3, 300M, ꢀppm) ꢀ: 2.51
6,7-dimethoxy-2-(1-phenethylamino-2-nitro)vinyl-1,2,3,4-
tetrahydroisoquinoline (6b)
(s, 3H, SCH3), 2.94 (t, 2H, C4-H), 3.84, 3.86 (s, 6H,
2ꢁOCH3), 3.96 (t, 2H, C3-H), 4.58 (s, 2H, C1-H), 6.55 (s, 1H,
CꢀCH(NO2)), 6.64, 6.72 (each s, 2H, C5-H, C8-H); IR
(KBr, ꢂ): 3460, 2932, 2837, 1660, 1559, 1455, 1381 cm-
1ꢁMS (ESI, m/z): 311.1 (M+H, base peak).
Following the procedure (6a) for the condensation be-
tween 5a and phenethylamine, the crude residue was purified
by column chromatography on silica gel (EtOAc-petroleum
ether 1-1 v/v), and compound 6b was obtained as a white
1
solid, yield: 56%, mp 150-152°ꢀ. HNMR (CDCl3, 300M,
6,7-dimethoxy-1-(3,4-dimethoxy)benzyl-2-(1-methylthio-
2-nitro)vinyl-1,2,3,4-tetrahydroisoquinoline (5b)
1
ꢀppm) ꢀ: HNMR (CDCl3 ,300M) ꢀꢆ3.82-2.84 (m, 3H, C4-
H, NHCH2), 2.97 (t, 2H, ArCH2), 3.43 (t, 2H, J=6.0Hz, C3-
H), 3.60 (m, 2H, NHCH2), 3.85 (s, 6H, 2ꢁOCH3), 4.21 (s,
2H, C1-H), 6.49-6.61 (each s, 3H, CꢂCH(NO2), C5-H, C8-
H), 7.26 (m, 5H, Ar-H)ꢁIR (KBr, ꢂ): 3415, 3240, 3152,
3027, 1612, 1582, 1518, 1450, 1374, 1357 cm-1ꢁMS (ESI,
m/z): 384.2 (M+H, base peak); Anal. Calcd. for
C21H25N3O4ꢆC 65.78, H 6.57, N 10.96; FoundꢆC 66.62, H
6.84, N 1.70.
Following the procedure described for 5a from 4b, com-
pound 5b was obtained as a yellow solid, 55%, mp 152-
154°ꢀ. 1HNMR (CDCl3, 300M, ꢀppm) ꢀ: 2.50 (s, 3H, SCH3),
2.85-3.53 (m, 6H, C3-H, C4-H, ArCH2), 3.76-3.85 (s, 12H,
4ꢁOCH3), 4.71 (t, 1H, C1-H), 6.34 (s, 1H, CꢂCH(NO2)),
6.41-7.26(m, 5H, Ar-H); IR (KBr, ꢂ): 3444, 2951, 2933,
1592, 1540, 1514, 1463, 1450 1366 cm-1; MS (ESI, m/z):
461.1 (M+H, base peak).
6,7-dimethoxy-1-(3,4-dimethoxy)benzyl-2-(1-n-octyl-
amino-2-nitro)vinyl-1,2,3,4-tetrahydroisoquinoline (6c)
6,7-dimethoxy-1-phenoxymethyl-2-(1-methylthio-2-
nitro)vinyl-1,2,3,4-tetrahydroisoquinoline (5c)
Following the procedure (6a) for the condensation be-
tween 5b and n-octyl amine, the crude residue was purified
Following the procedure described for 5a from 4c, com-
pound 5c was obtained as a yellow solid, 50%, mp 195-

Synthesis and Biological Evaluation
Medicinal Chemistry, 2012, Vol. 8, No. 4 715
by column chromatography on silica gel (EtOAc-petroleum
490.2 (M+H, base peak); Anal.Calcd. for C28H31N3O5: C
68.69, H 6.38, N 8.58; Found: C, 68.55, H 6.46, N 8.54.
ether 1-1 v/v), and compound 6c was obtained as a white
1
solid, yield: 62%, mp 156-158°ꢀ. HNMR (CDCl3, 300M,
6,7-dimethoxy-1-(ꢀ-naphthylmethyl)-2-(1-n-butylamino-
2-nitro)vinyl-1,2,3,4-tetrahydroisoquinoline (6g)
ꢀppm) ꢀ: 0.88 (t, 3H, J=6.0Hz, (CH2)2CH3), 1.24-1.55 (m,
15H, (CH2)6CH3), 2.69-3.56 (m, 8H, C3-H, C4-H, NHCH2,
ArCH2), 3.75-3.88 (s, 12H, 4ꢁOCH3), 4.70 (t, 1H, J=7.5Hz,
C1-H), 6.31 (s, 1H, CꢁCH(NO2)), 6.41-7.26 (m, 5H, Ar-H);
IR (KBr, ꢂ): 3444, 2996, 2923, 2844, 1592, 1544, 1515,
1464, 1448, 1356 cm-1ꢂMS (ESI, m/z) : 542.3 (M+H, base
peak); Anal. Calcd. for C30H43N3O6: C 66.52, H 8.00, N
7.76; Found: C 66.48, H 8.11, N 7.74.
Following the procedure (6a) for the condensation be-
tween 5d and n-butylamine, the crude residue was purified
by column chromatography on silica gel (EtOAc-petroleum
ether 1-1 v/v), and compound 6g was obtained as a white
1
solid, yield: 60%, mp 221-223°ꢀ. HNMR (CDCl3, 300M,
ꢀppm) ꢀ: 0.83 (t, 3H, J=6.0Hz, (CH2)2CH3), 1.12-1.35 (m,
4H, (CH2)2CH3), 1.58 (d, 1H, J=6.0Hz, NHCH), 2.76-3.00
(m, 4H, C4-H, NHCH2), 3.51-3.75 (m, 4H, C3-H, Ar'CH2,),
3.53 (s, 3H, C7-OCH3), 3.86 (s, 3H, C6-OCH3), 4.87 (t, 1H,
J=7.5Hz, C1-H), 6.03 (s, 1H, CꢁCH(NO2)), 6.37, 6.61 (each
s, 2H, C5-H, C8-H), 7.17-7.96(m, 7H, Ar-H); IR (KBr, ꢂ):
3451, 2957, 2933, 2866, 1588, 1518, 1464, 1452, 1352 cm-1;
MS (ESI, m/z): 476.3 (M+H, base peak); Anal.Calcd. for
C28H33N3O4·0.3H2O: C 69.92, H, 7.04, N 8.74; Found: C
70.17, H 7.01, N 8.75.
6,7-dimethoxy-1-(3, 4-dimethoxy)benzyl-2-(1-phenethyl-
amino-2-nitro)vinyl-1,2,3,4-tetra hydroisoquinoline (6d)
Following the procedure (6a) for the condensation be-
tween 5b and phenethylamine, the crude residue was puri-
fied by column chromatography on silica gel (EtOAc-
petroleum ether 1-1 v/v), and compound 6d was obtained as
1
a white solid, yield: 65%, mp 180-181°ꢀ. HNMR (CDCl3,
300M, ꢀppm) ꢀ: 2.64-3.49 (m, 10H, C3-H, C4-H, NHCH2,
2ArCH2), 3.73-3.85 (s, 12H, 4ꢁOCH3), 4.65 (t, 1H, J=7.5Hz,
C1-H), 6.26 (s, 1H, CꢁCH(NO2)), 6.26, 6.37 (each s, 2H,
C5-H, C8-H), 6.57-7.33 (m, 8H, Ar-H)ꢂIR (KBr, ꢂ):
3436,2996, 2924, 2830, 1590, 1514, 1498, 1465, 1451, 1352
cm-1ꢂMS (ESI, m/z): 534.2 (M+H, base peak); Anal. Calcd.
for C30H35N3O6: C 67.52, H 6.61, N 7.87; Found: C 67.30, H
6.77, N 7.92.
6,7-dimethoxy-1-(ꢀ-naphthylmethyl)-2-(1-(3,4-dimetho-
xy)-phenethylamino-2-nitro)vinyl-1,2,3,4-tetrahydroiso-
quinoline (6h)
Following the procedure (6a) for the condensation be-
tween 5d and 3,4-dimethoxyphenethylamine, the crude resi-
due was purified by column chromatography on silica gel
(EtOAc-petroleum ether 1-1 v/v), and compound 6h was
obtained as a white solid, yield: 60%, mp 221-223°ꢀ.
1HNMR (CDCl3, 300M, ꢀppm) ꢀ: 2.57-2.73 (m, 4H, C4-H,
Naphthyl-CH2), 3.16-3.70 (m, 6H, C3-H, NHCH2, Ar'CH2,),
3.49, 3.83 (s, 12H, 4ꢁOCH3), 4.81 (t, 1H, J=7.5Hz, C1-H),
5.86 (s, 1H, CꢁCH(NO2)), 6.34, 6.58 (each s, 2H, C5-H, C8-
H), 6.60-7.88(m, 10H, Ar-H); IR (KBr, ꢂ): 3429, 2924, 2830,
1607, 1589, 1515, 1462, 1353 cm-1; MS (ESI, m/z): 584.3
(M+H, base peak); Anal. Calcd. for C34H37N3O6: C 69.96, H
6.39, N 7.20; Found: C 69.97, H 6.41, N 7.17.
6,7-dimethoxy-1-phenoxymethyl-2-(1-n-octylamino-2-
nitro)vinyl-1,2,3,4-tetrahydroisoquinoline (6e)
Following the procedure (6a) for the condensation be-
tween 5c and n-octyl amine, the crude residue was purified
by column chromatography on silica gel (EtOAc-petroleum
ether 1-1 v/v), and compound 6e was obtained as a white
1
solid, yield: 60%, mp 112-114°ꢀ. HNMR (CDCl3, 300M,
ꢀppm) ꢀ: 0.83 (t, 3H, J=6.0Hz, CH2CH3), 1.24-1.68 (m,
12H, (CH2)6CH3), 2.71-2.77(m. 2H, NHCH2), 3.29-3.33(dd,
2H, J=13.2Hz, J=6.7Hz, C4-H), 3.59-3.62 (t, 2H, J=5.8Hz,
C3-H), 3.87 (s, 6H),3.87 (s, 6H, 2ꢁOCH3), 4.17 (dd, 2H,
J=18.0Hz, J=9.0Hz, Ar-OCH2), 4.89 (t, 1H, J=9.0Hz, C1-H),
6.52 (s, 1H, CꢁCH(NO2)), 6.62, 6.65 (each s, 2H, C5-H, C8-
H), 6.81-7.29 (m, 5H, Ar-H)ꢂIR (KBr, ꢂ): 3429, 2987,
2922, 2853, 1599, 2587, 1536, 1516, 1432, 1358 cm-1ꢂMS
(ESI, m/z): 498.1 (M+H, base peak); Anal. Calcd. for
C28H39N3O5: C 67.58, H 7.90, N 8.44; Found: C 67.63, H
7.98, N 8.41.
6,7-dimethoxy-2-(N-nitro)guanyl-1,2,3,4-tetrahydroiso-
quinoline (7a)
A mixture of 5a (0.97g, 5.0mmol), anhydrous ethanol
(30mL) and S-methyl-N-nitroisothiourea (0.68g, 5.0mmol)
was refluxed for 12h. The mixture was cooled to room tem-
perature and stood overnight. Then compound 7a was col-
lected, washed with cooled anhydrous ethanol and obtained a
white, crystalline powder, 0.77g, yield: 55%, mp 145-147°ꢀꢃꢄ
1HNMR (CDCl3, 300M, ꢀppm) ꢀ: 2.88 (t, 2H, J=6.0Hz, C4-
H), 3.75 (t, 2H, J=6.0Hz, C3-H), 3.85 (s, 6H, 2ꢁOCH3), 4.64
(s, 2H, C1-H), 6.67(s, 2H, Ar-H), 7.86 (s, 2H, NH2); IR
(KBr, ꢂ): 3380, 3281, 3198, 2953, 2830, 1744, 1602, 1577,
1519, 1484, 1467, 1380, 1300 cm-1; MS (ESI, m/z): 281.1
(M+H, base peak); Anal. Calcd. for C12H16N4O4: C 51.42, H
5.75, N 19.99; Found: C 51.49, H 5.65, N 20.06.
6,7-dimethoxy-1-phenoxymethyl-2-(1-phenethylamino-2-
nitro)vinyl-1,2,3,4-tetrahydroisoquinoline (6f)
Following the procedure (6a) for the condensation be-
tween 5c and phenethylamine, the crude residue was purified
by column chromatography on silica gel (EtOAc-petroleum
ether 1-1 v/v), and compound 6f was obtained as a white
1
solid, yield: 65%, mp 180-181°ꢀ. HNMR (CDCl3, 300M,
6,7-dimethoxy-1-(3,4-dimethoxy)benzyl-2-(N-nitro)gua-
nyl-1,2,3,4-tetrahydroisoquinoline (7b)
ꢀppm) ꢀ: 2.35-2.97 (m, 8H, C3-H, C4-H, ArCH2 NHCH2),
3.87 (s, 6H, 2ꢁOCH3), 4.11 (dd, 2H, J=18.0Hz, J=9.1Hz, Ar-
OCH2), 4.76 (t, 1H, J=9.1Hz, C1-H), 6.48 (s, 1H,
CꢁCH(NO2)), 6.58, 6.57 (each s, 2H, C5-H, C8-H), 6.79-
7.29 (m, 10H, Ar-H); IR (KBr, ꢂ): 3465, 3126, 2916, 2830,
1594, 1536, 1518, 1466, 1433, 1355 cm-1; MS (ESI, m/z):
A mixture of 5b (1.7g, 5.1mmol), anhydrous ethanol
(30mL) and S-methyl-N-nitroisothiourea (0.68g, 5.0mmol)
was refluxed for 48h. The resultant solvent was concentrated
under pressure. The residue was purified by column chroma-

716 Medicinal Chemistry, 2012, Vol. 8, No. 4
Zou et al.
tography on silica gel (EtOAc-petroleum ether 1-2 v/v), and
compound 7b was obtained as a white solid 1.2g, yield:
53%, mp 151-152°ꢀ. 1HNMR (CDCl3, 300M, ꢀppm) ꢀ: 2.67-
3.51 (m, 6H, C3-H, C4-H, ArCH2), 3.73, 3.85 (s, 12H,
4ꢁOCH3), 5.25 (t, 1H, J=7.5Hz, C1-H), 6.37-6.77(m, 5H, Ar-
H), 7.32 (s, 2H, NH2); IR (KBr, ꢂ): 3429, 3310, 2993, 2958,
2937, 2830, 1740, 1615, 1564, 1517, 1446, 1382, 1296 cm-1;
MS (ESI, m/z)ꢀ431.1 (M+H, base peak); Anal. Calcd. for
C21H26N4O6: C 58.59, H 6.09, N 13.02; Found: C 58.19, H
6.04, N 12.70.
REFERENCES
[1]
Liscovitch, M.; Lavie, Y. Cancer multidrug resistance: a review of
recent drug discovery research. IDrugs, 2002, 5(4), 349-355.
Thomas, H.; Coley, H. M. Overcoming multidrug resistance in
cancer: an update on the clinical strategy of inhibiting p-
glycoprotein. Cancer Control, 2003, 10(2), 159-165.
[2]
[3]
Chatterjee, M.; Robson, C. N.; Harris, A. L. Reversal of multidrug
resistance by verapamil and modulation by alpha 1-acid
glycoprotein in wild-type and multidrug-resistant Chinese hamster
ovary cell lines. Cancer Res, 1990, 50(9), 2818-2822.
[4]
[5]
Pereira, E.; Teodori, E.; Dei, S.; Gualtieri, F.; Garnier-Suillerot, A.
Reversal of multidrug resistance by verapamil analogues. Biochem
Pharmacol, 1995, 50(4), 451-457.
Shi, X.; Mao, Y.; Saffiotti, U.; Wang, L.; Rojanasakul, Y.;
Leonard, S. S.; Vallyathan, V. Antioxidant activity of tetrandrine
and its inhibition of quartz-induced lipid peroxidation. J Toxicol
Environ Health, 1995, 46(2), 233-248.
6,7-dimethoxy-1-phenoxymethyl-2-(N-nitro)guanyl-1,2,3,
4-tetrahydroisoquinoline (7c)
Following the procedure (7b) for the condensation be-
tween 5c and S-methyl-N-nitroisothiourea, the crude residue
was purified by column chromatography on silica gel
(EtOAc-petroleum ether 1-2 v/v), and compound 7c was
obtained as a white solid, yield: 53%, mp 122-124°ꢀ.
1HNMR (CDCl3, 300M, ꢀppm) ꢀ: 2.80-3.46 (m, 4H, C3-H,
C4-H), 3.86 (s, 6H, 2ꢁOCH3), 4.25-4.37 (m, 3H, C1-H, Ar-
OCH2), 6.67, 6.69 (each s, 2H, C5-H, C8-H), 6.87-7.32 (m,
5H, Ar-H), 7.99 (s, 2H, NH2); IR (KBr, ꢂ): 3373, 3274,
3198, 2966, 2935, 2837, 1747, 1615,1599, 1550, 1516, 1448,
1462, 1394, 1372 cm-1; MS (ESI, m/z)ꢀ387.1 (M+H, base
peak); Anal.Calcd. for C19H22N4O5: C 59.06, H 5.74, N
14.50; Found: C 58.96,H 5.69, N 14.25.
[6]
Shen, Y. C.; Chou, C. J.; Chiou, W. F.; Chen, C. F. Anti-
inflammatory effects of the partially purified extract of radix
Stephaniae tetrandrae: comparative studies of its active principles
tetrandrine and fangchinoline on human polymorphonuclear
leukocyte functions. Mol Pharmacol., 2001, 60(5), 1083-1090.
Hong, J. L.; Zhou, H. L.; Bian, R. L. [Effects of tetrandrine on
cytoplasmic free calcium in rat neutrophils]. Zhongguo Yao Li Xue
Bao, 1989, 10(6), 533-537.
Liu, B.; Wang, T.; Qian, X.; Liu, G.; Yu, L.; Ding, Y. Anticancer
effect of tetrandrine on primary cancer cells isolated from ascites
and pleural fluids. Cancer Lett., 2008, 268(1), 166-175.
Li, Y.; Zhang, H. B.; Huang, W. L.; Li, Y. M. Design and synthesis
of tetrahydroisoquinoline derivatives as potential multidrug
resistance reversal agents in cancer. Bioorg Med Chem Lett, 2008,
18(12), 3652-3655.
[7]
[8]
[9]
[10]
Yan, F.; Jiang, Y.; Li, Y. M.; Zhen, X.; Cen, J.; Fang, W. R.
Reversal of P-glycoprotein and multidrug resistance-associated
protein 1 mediated multidrug resistance in cancer cells by HZ08
Isomers, tetrataisohydroquinolin derivatives. Biol Pharm Bull,
2008, 31(6), 1258-1264.
Cen, J.; Qi, Y.; Tao, Y. F.; Deng, Y.; Fang, W. R.; Li, Y. M.;
Zhang, L. Y.; Huang, W. L. HZ08, a great regulator to reverse
multidrug resistance via cycle arrest and apoptosis sensitization in
MCF-7/ADM. Eur. J. Pharmacol., 2010, 647(1-3), 21-30.
Zou, Z.; Lan, X.; Qian, H.; Huang, W.; Li, Y. Synthesis and
evaluation of furoxan-based nitric oxide-releasing derivatives of
tetrahydroisoquinoline as anticancer and multidrug resistance
reversal agentsꢁBioorg. Med. Chem. Lett., 2011, 21(19), 5934-
5938.
Manske, R. H. The chemistry of isoquinolizines. Chem Rev, 1942,
1942(30), 145-158.
Samuel Natelson. Rearrangement of Alkyl Phenyl Ethers on
Heating at Moderate Temperatures. Synthesis of Tertiary Amyl,
Tertiary Butyl and Diisobutyl Phenols. J Am Chem Soc, 1934,
56(12), 2799.
He, H.; Liu, M.; Zheng, Z.; Liu, Y.; Xiao, J.; Su, R.; Hu, C.; Li, J.;
Li, S. Synthesis and analgesic activity evaluation of some agmatine
derivatives. Molecules, 2006, 11(6), 393-402.
Wang, R.; Guo, Y.; Zeng, Z.; Shreeve, J. M. Nitrogen-rich
nitroguanidyl-functionalized tetrazolate energetic salts. Chem
Commun (Camb), 2009, 45(19), 2697-2699.
Jabbar, S. A.; Twentyman, P. R.; Watson, J. V. The MTT assay
underestimates the growth inhibitory effects of interferons. Br J
Cancer, 1989, 60(4), 523-528.
6,7-dimethoxy-1-(ꢀ-naphthylmethyl)-2-(N-nitro)guanyl-
1,2,3,4-tetrahydroisoquinoline (7d)
Following the procedure (7b) for the condensation be-
tween 5d and S-methyl-N-nitroisothiourea, the crude residue
was purified by column chromatography on silica gel
(EtOAc-petroleum ether 1-2 v/v), and compound 7d was
obtained as a white solid, yield: 59%, mp 192-194°ꢀ.
1HNMR (CDCl3, 300M, ꢀppm) ꢀ: 2.93 (t, 2H, J=6.5Hz, C4-
H), 2.95-3.66 (m, 4H, C3-H, ArCH2), 3.79, 3.86 (s, 6H,
2ꢁOCH3), 5.43 (t, 1H, J=7.5Hz, C1-H,), 6.64, 6.90 (each s,
2H, C5-H, C8-H), 7.06-7.87 (m, 7H, Ar-H), 8.49 (s, 2H,
NH2); IR (KBr, ꢂ): 3395, 3306, 2953, 2830, 1740, 1614,
1548, 1518, 1479, 1452, 1396, 1293 cm-1; MS (ESI,
m/z)ꢀ421.1 (M+H, base peak); Anal. Calcd. for
C23H24N4O4: C 65.70, H 5.75, N 13.33; Found: C 65.35, H
5.70, N 13.04.
[11]
[12]
[13]
[14]
[15]
[16]
[17]
ACKNOWLEDGMENTS
The work was supported by the Important National Sci-
ence and Technology Specific Projects (2009ZX09102-033),
the National Natural Science Foundation of China (No.
81172932) and the High Technology Programs of Jiangsu
province (BG2007612).
Received: March 01, 2011
Revised: September 17, 2011
Accepted: October 03, 2011