Synthesis of 2-aryl-3,4-dihydroisoquinolin-2-ium bromides and their in Vitro acaricidal activity against Psoroptes cuniculi

Article abstract of DOI:10.1248/cpb.c12-00876

By employing sanguinarine, a natural active quaternary isoquinoline alkaloid, as a model molecule, a series of structurally simple quaternary 2-aryl-3,4-dihydroisoquinolin-2-ium compounds were designed and synthesized and evaluated for in vitro acaricidal activity against P. cuniculi. A new approach towards the title compounds was developed with isochroman as starting material. The results showed that 22 of 24 tested compounds displayed the activity in varying degrees at 0.4 mg/mL. Fourteen compounds were significantly more effective than ivermectin, a standard acaricide, and 6-methoxy dihydrosanguinarine, a derivative of sanguinarine (p<0.05). And their comprehensive relative activity was 1.4 to 16.5 times than that of ivermectin and 1.5 to 18.8 times than that of 6-methoxy dihydrosanguinarine. The structure-activity relationship indicated that the introduction of a substituent to N-benzene ring, especially halogen atom and trifluoromethyl group, led to great improvement of the activity. The position of fluorine atom, methyl group and hydroxyl group made very significant effects on the activity. It was concluded that 2-aryl-3,4-dihydroisoquinolin- 2-iums are very promising candidates for the development of new isoquinoline acaricidal agents.

Full text of DOI:10.1248/cpb.c12-00876

204
Regular Article
Chem. Pharm. Bull. 61(2) 204–211 (2013)
Vol. 61, No. 2
Synthesis of 2-Aryl-3,4-dihydroisoquinolin-2-ium Bromides and Their in
Vitro Acaricidal Activity against Psoroptes cuniculi
Yan-Ni Ma,a,# Xin-Juan Yang,a,b,# Le Pan,b Zhe Hou,a Hui-Ling Geng,a Xiao-Ping Song,c
,a
,b
Le Zhou,* and Fang Miao*
b
a College of Science, Northwest A&F University; College of Life Science, Northwest A&F University; and
c Department of Veterinary Medicine, Northwest A&F University; Yangling, Shaanxi 712100, China.
Received October 5, 2012; accepted November 27, 2012; advance publication released online December 5, 2012
By employing sanguinarine, a natural active quaternary isoquinoline alkaloid, as a model molecule, a
series of structurally simple quaternary 2-aryl-3,4-dihydroisoquinolin-2-ium compounds were designed and
synthesized and evaluated for in vitro acaricidal activity against P. cuniculi. A new approach towards the
title compounds was developed with isochroman as starting material. The results showed that 22 of 24 tested
compounds displayed the activity in varying degrees at 0.4mg/mL. Fourteen compounds were significantly
more effective than ivermectin, a standard acaricide, and 6-methoxy dihydrosanguinarine, a derivative of
sanguinarine (p<0.05). And their comprehensive relative activity was 1.4 to 16.5 times than that of ivermec-
tin and 1.5 to 18.8 times than that of 6-methoxy dihydrosanguinarine. The structure–activity relationship in-
dicated that the introduction of a substituent to N-benzene ring, especially halogen atom and trifluoromethyl
group, led to great improvement of the activity. The position of fluorine atom, methyl group and hydroxyl
group made very significant effects on the activity. It was concluded that 2-aryl-3,4-dihydroisoquinolin-
2-iums are very promising candidates for the development of new isoquinoline acaricidal agents.
Key words acaricidal activity; Psoroptes cuniculi; 2-aryl-3,4-dihydroisoquinolin-2-ium; 6-methoxy dihydro-
sanguinarine; sanguinarine; structure–activity relationship
Acariasis is a chronic skin disease caused by mites, an ecto- mange are based mainly on the use of effective drugs and
parasite, and widely occurs in animals and human. Psoroptes chemicals. At present, the use of drugs to control these
cuniculi is one of animal mites and mainly infects rabbits, parasitic arthropods presents several problems including drug-
goats, horses and sheep.1) It causes intense pruritus of animals resistance4,5) and environmental damage.6,7) Ivermectin (Fig.
with the formation of crusts and scabs and reduction of weight 1), a clinically used acaricide, is increasingly being used to
gain, or even death of animals.2,3) Therefore, this mite species treat human scabies but often treatment failures, recrudes-
causes serious economic losses for animal industry.
cence and reinfection can occur.8) Concern over toxicity of
Therapy and control of both human scabies and animal many acaricides limits their use and reduces the number of
Fig. 1. Structures of Ivermectin (95% Avermectin B1a and 5% Avermectin B1b), Sanguinarine, 6-Alkoxy Dihydrosanguinarines and 2-Aryl-3,4-
dihydroisoquinolin-2-ium Bromides
The authors declare no conflict of interest.
# These authors contributed equally to this work.
© 2013 The Pharmaceutical Society of Japan
*To whom correspondence should be addressed. e-mail: zhoulechem@yahoo.com.cn;
miaofangmf@163.com

February 2013
205
Reagents and conditions: (a) 57% HI, reflux, 1h, 96% yield; (b) 2a–x/water, SDS, refluxing, 2–3h, 86–94% yield; (c) CuCl2·2H2O, MeOH, refluxing, 10h, 94–99% yield;
(d) 47% HBr, 80–94% yield.
Chart 1. Synthetic Route of 2-Aryl-3,4-dihydroisoquinolin-2-ium Bromides
safe effective products available. These problems have led to compounds 2-aryl-1,2-dihydroisoquinolin-2-ium bromides 5a–
research efforts to discover new effective and safe acaricides x as solids in good yield (40–99%).
from active natural products.
In the literature, a few methodologies have been devel-
Sanguinarine is a natural quaternary benzo[c]phenanthridine oped to construct the 2-R-3,4-dihydroisoquinolin-2-iums.21–25)
alkaloid (QBAs) (Fig. 1), which is a relatively small subclass Among them, the condensation of 2-(2-bromoethyl)benz-
of isoquinoline alkaloids and mainly presents in the families aldehyde with primary amine was the most commonly used
of the Fumariaceae, Papaveraceae and Rutaceae families.9) In synthetic strategy. But we found that the method above was
the past decades, QBAs have given rise to a lot of attention not easy to provide high purity products which are necessary
because of their biological activities including antitumor,10) for their bioactivity evaluation. In addition, its key interme-
antimicrobial,11,12) anti-inflammatory,13) anti-human immuno- diate 2-(2-bromoethyl)benzaldehyde was not stable at room
deficiency virus (HIV),14) anti-angiogenesis15) and anti-acetyl- temperature and the operation procedure was not very con-
cholinesterase,16) and antiparasitic actions against Trichodina venient. On the contrary, compound 1 was solid, stable and
sp.,17) Dactylogyrus intermedius18) and malaria.19)
easy preparation in excellent yield as well as easy purification.
Our recent research found that 6-alkoxy dihydrosanguina- Compared with the literature method, the present method has
rines (Fig. 1) possessed significant in vitro acaricidal activity some obvious advantages such as higher yields, simple work-
against P. cuniculi, comparable with the commercial acaricide up operation and easily obtaining high purity products.
ivermectin.20) In addition, 6-alkoxy dihydrosanguinarines
The structures of all the target compounds were elucidated
were proven to be most likely prodrugs of sanguinarine, the by spectroscopic analyses. Each of the compounds showed a
real active component, and the iminium moiety (C=N+) in characteristic ion peak at m/z [M−Br] in positive electrospray
sanguinarine might well be a determinant factor for its acari- ionization (ESI)-MS spectrum, two bromide ion peaks at m/z
cidal property. The results above suggested that QBAs were 78.9 [79Br−] and 80.9 [81Br−] in negative ESI-MS spectrum and
considered as promising candidates or lead compounds or a strong absorption (C=N+) in a range of 1618 to 1640cm−1 in
1
model compounds for the development of new isoquinoline IR spectrum. In H- and 13C-NMR spectra, all the compounds
acaricidal agents. The purpose of this study is to design and 5a–x revealed singlet signals in a range of δ 9.35 to 10.27ppm
synthesize a series of C=N+-containing simple quaternary due to the HC=N+ proton (i.e. H-1) and one signal in a range
isoquinolin-2-ium compounds (Fig. 1, 5a–x) by employing of δ 157 to 173ppm due to C-1.
sanguinarine as a model molecule, and examine their acari-
Acaricidal Activity in Vitro and Structure–Activity Re-
cidal activity against P. cuniculi as well as understand their lationship In vitro acaricidal activity of target compounds
structure–activity relationship. Furthermore, we also expect 5a–x was performed according to our previous method20) with
that the present research can lead to the discovery of new some modification. Ivermectin as a standard acaricide and
acaricidal compounds.
6-methoxy dihydrosanguinarine (MSA) as the prodrug of the
model compound sanguinarine were used as the positive drug
control. The acaricidal activity and substitution patterns of
Results and Discussion
Chemistry The chemical synthesis of these compounds 5a–x are displayed in Fig. 2.
was outlined in Chart 1. As a key intermediate, compound
The results in Fig. 2 showed that except for 5a and 5s
1 was synthesized by the reaction of isochroman with 57% without activity all the target compounds displayed activity
hydroiodic acid under refluxing in 96% yield. Compound against P. cuniculi in varying degrees. Among all 24 tested
1 reacted with various mono-substituted anilines (2a–x) in compounds, fourteen compounds (5b, 5e–o, 5t, 5v) with the
water solution by using sodium dodecyl sulfonate (SDS) as mortality of 76.7 to 100% showed significantly stronger ac-
phase-transfer catalyst to afford intermediates 2-aryl-1,2,3,4- tivity than ivermectin with the mortality of 68.3% and MSA
tetrahydroisoquinolines 3a–x in 86―94% yield. The oxidation with the mortality of 51.7% (p<0.05). Compound 5f, 5h and
of 3a–x with CuCl2·2H2O in methanol quantitatively provided 5m gave the best activity with the mortality of 98.3 to 100%
the corresponding intermediates 2-aryl-1-methoxy-1,2,3,4- (p>0.05). Eight tested compounds, 5c, 5d, 5p–r, 5u, 5w and
tetrahydroisoquinolines 4a–x. The solution of 4a–x in 1,4-di- 5x exhibited lower activity with the mortality of 11.7% to
oxane was treated with hydrobromic acid to provide the target 45.0% than ivermectin.

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Vol. 61, No. 2
Fig. 2. In Vitro Acaricidal Activity of the Compounds against P. cuniculi at 0.4mg/mL
The difference between the data of two compounds with the different lowercase letter is significant (p<0.05); IV: ivermectin. the same below; MSA: 6-methoxy dihy-
drosanguinarine. The same below; Con: control.
Comparison of the activity of 5a (R=H) with that of 5b–x of the acaricidal activity of the target compounds, the higher
showed that the characteristics and position of the substitu- active compound 5b, 5e–o, 5t and 5v were subjected to acari-
ent located on N-benzene ring made significant effects on the cidal toxicity assay. Meanwhile, ivermectin and MSA were
acaricidal activity. Generally, the introduction of the substitu- used as standard drug control and model compound control,
ent to N-aromatic ring led to improvement of activity in vary- respectively. The results were listed in Table 1.
ing degrees. The general trend was that chlorine atom (5e–g),
The acaricidal activity of all the tested compounds showed
bromine atom (5h, 5i), iodine atom (5j–l) and trifluoromethyl the significant concentration dependence (R2≥0.9068, p<0.05).
group (5m–o) brought about the best improvement of activity. Except for 5e and 5g, all the tested compounds showed small-
Nitro group (5p–r) caused a moderate enhancement effect on er 50% lethal concentrations (LC50) (17.9–126.7mg/L) than
activity. For methyl group, fluorine atom and hydroxyl group, ivermectin (LC50 170.8mg/L) and MSA (LC50 335.9mg/L),
the significant position effects were observed. Among three indicating these compounds were more effective than iver-
fluorinated compounds (5b–d), 2′-fluorinated compound (5b) mectin and MSA. Unlike the other target compounds, the
was significantly more effective than 3′-F and 4′-F isomers LC50 values of 5e and 5g (172.6, 179.0mg/L) were larger than
(5c, 5d) (p<0.05), but there was no significant difference that of ivermectin but smaller than that of MSA. Among the
between 3′-F (5c) and 4′-F isomers (5d). A similar trend was compounds, 5l showed the smallest LC50 value (17.9mg/L) and
also observed for hydroxyl compounds (5v, 5w). Unlike the the strongest activity. In addition, the relative activity among
position effect of fluorine atom, 3′-Me isomer (5t) showed the the compounds can also be more clearly seen from the ratio of
strongest activity, followed by 4′-Me isomer (5u), while 2′-Me the LC50 value (LC50i) of ivermectin to that (LC50c) of each the
(5s) did not make improvement effect of activity.
target compound.
Acaricidal Toxicity To have a thorough understanding
Concentration effect (CE) of a compound on its activity is
Table 1. Toxicity Regression Equations and LC50 Values of Compounds 5b, 5e–o, 5t, 5v against P. cuniculi
Toxicity regression
d)
Compd.
R2
Linear range (mg/L)
LC50 (95%CI)b)
kc/kic)
LC50i/LC50c
equationa)
5b
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5t
5v
IV
MSA
y=0.6977x+3.9274
y=3.3704x−2.5398
y=3.9546x−2.2638
y=2.5269x−0.6926
y=3.7993x−0.6057
y=2.0331x+1.4321
y=1.5669x+2.1711
y=0.7395x+3.6340
y=0.9481x+3.8117
y=3.5353x−0.6991
y=1.6351x+2.3702
y=2.6727x+0.8954
y=1.5786x+1.6806
y=1.3701x+2.9669
y=1.3151x+2.0642
y=2.2707x−0.7363
0.9465
0.9866
0.9994
0.9750
0.9681
0.9187
0.9254
0.9068
0.9259
0.9907
0.9254
0.9674
0.9715
0.9327
0.9801
0.9619
20–500
60–400
40–200
40–1000
10–50
10–200
10–2000
40–2000
20–400
20–80
10–400
10–80
40–1000
20–400
20–1500
100–800
34.46 (35.8–33.1)
172.6 (160.0–186.3)
68.7 (68.4–69.0)
179.0 (153.4–208.8)
29.9 (25.9–34.5)
56.9 (46.3–69.8)
63.9 (41.9–97.4)
70.3 (62.8–78.7)
17.9 (16.6–19.3)
40.9 (39.8–42.1)
40.6 (31.6–52.2)
34.3 (30.3–39.0)
126.7 (118.2–135.7)
30.5 (27.7–33.5)
170.8 (160.5–181.7)
335.9 (308.5–365.8)
0.53
2.56
3.01
1.92
2.89
1.55
1.19
0.56
0.72
2.69
1.24
2.03
1.20
1.04
1.00
1.73
5.0
1.0
2.5
1.0
5.7
3.0
2.7
2.4
9.5
4.2
4.2
5.0
1.3
5.6
1.0
0.5
a) y: the probability of the average corrected mortality rate; x: log[concentration (mg/L)]. b) 95%CL: lower and upper values of the confidence interval at 95% probability. c)
kc: slope value of the tested compound; ki: slope value of ivermectin. d) LC50i: LC50 value of ivermectin; LC50c: LC50 value of the tested compound.

February 2013
207
Fig. 3. Comprehensive Relative Activity of Compounds 5b, 5e–o, 5t and 5v against P. cuniculi
an important factor for evaluation of its activity. The CE of 5s, all the target compounds showed the activity on differ-
the tested compound on its acaricidal activity can be reflected ent levels and 14 compounds (5b, 5e–o, 5t and 5v) showed
by slope ratio value (k) in activity regression equation in Table the higher activity than a standard drug ivermectin and their
1, and the ratio of the k value (kc) of each the target compound natural model compound MSA. The significant effect of the
to that (ki) of ivermectin reflects their relative CE. The data characteristics and position of the substituent located on N-
in Table 1 showed that various compounds had different k benzene ring on the activity was observed. The introduction
values, indicating that various compounds had different CEs of a substituent especially halogen atom and trifluoromethyl
on their bioactivity against P. cuniculi. Compared with iver- group to N-benzene ring led to improvement of the activity
mectin, except for 5b, 5k and 5l (kc/ki<1.0), all the target com- and the position of fluorine atom, methyl group and hydroxyl
pounds possessed more than 1.0 of kc/ki values, indicating that group made very significant effects on the bioactivity. The
they had stronger CEs on acaricidal activity than ivermectin. results suggested that 2-aryl-3,4-dihydroisoquinolin-2-ium
However, when compared with MSA (kc/ki=1.73), only 6 of 14 compounds are very promising candidates for the development
the tested compounds gave more than 1.73 of kc/ki values.
In order to comprehensively compare the activity of the dif-
ferent compounds, the value of (LC50i/LC50c×kc/ki) of each the
compound, named as comprehensive relative activity (CRA),
of new isoquinoline acaricidal agents.
Experimental
Materials Ivermectin (≥91% 22,23-dihydroavermectin B1
was calculated and shown in Fig. 3. The results showed that consisting of 95% avermectin B1a and 5% avermectin B1b) was
the CRA values (1.4 to 16.5) of all the tested compounds were purchased from Sigma-Aldrich Trading Co., Ltd., Shanghai,
bigger than that of ivermectin (CRA=1.0) and MSA (CRA= China. MSA was prepared from sanguinarine by our previous-
0.9), indicating that all the tested compounds possessed stron- ly reported method.12,20) Other chemicals were purchased from
ger CRA than ivermectin and MSA. This conclusion was in J&K Chemical Ltd. (China) and used without purification.
agreement with that obtained data from Table 1. Among them,
5h had the strongest CRA (16.5), which was attributed to its cro-melting point apparatus and uncorrected. IR spectra were
bigger LC50i/LC50c value and bigger kc/ki value. taken on a Nexus FT-IR 400 spectrometer with KBr pellets.
Apparatus Melting points were determined on XT-4 mi-
As mentioned in the introduction, our previous research UV Spectra were performed on a SP-2100 UV/VIS spectrom-
had proven that 6-alkoxy dihydrosanguinarines were prodrugs eter. 1H- and 13C-NMR spectra were recorded with Bruker
of sanguinarine and the acaricidal activity of the former was AVANCE III operating at 500 and 125MHz, respectively
far stronger than the latter, likely due to the former’s higher and using TMS as internal standard. ESI-MS was measured
lipophilicity and higher compatibility with physiological con- on Trace mass spectrometer (Thermo Finnigan Co.). Column
ditions. On these grounds, we speculated that the 1-alkoxy di- chromatography was performed on silica gel 60G (Qingdao
hydro derivatives of 5a–x may have higher activity than 5a–x. Haiyang Chemical, China).
At present, the work on this aspect is under way in our lab.
Synthesis of 1 The mixture of isochroman (13.4g,
In conclusion, a new synthetic approach towards 2-aryl-3,4- 0.10mol) and 57% HI aqueous solution (52.8mL, 89.8g,
dihydroisoquinolin-2-ium compounds from commercially 0.40mol) were refluxed in dark place for 1h. The reaction
available isochroman was developed and used to prepare the solution was diluted with 50mL water, and extracted with
target compounds 5a–x. These reactions are simple and easily diethyl ether. The combined ether solution was washed with
carried under normal reaction conditions. The present system water and then saturated sodium sulfite solution, and dried
has the advantages of higher yields, simple work-up operation over anhydrous sodium sulfate. The solvent was removed
and easily obtaining high purity products.
under a reduced pressure to provide 1 (35.7 g).
All the target compounds 5a–x were evaluated for their in
1-(2-Iodoethyl)-2-(iodomethyl)benzene (1): White needle
vitro acaricidal activity against P. cuniculi. Except 5a and crystals in 96% yield, mp 60―62°C; Rf=0.64 (petroleum

208
Vol. 61, No. 2
ether–ethyl acetate, 8:1); 1H-NMR (500MHz, CDCl3) δ: J=22.3Hz), 102.1 (d, J=26.5Hz), 43.2 (C-3), 16.9 (C-4); posi-
7.14–7.34 (4H, m), 4.46 (2H, s), 3.42 (2H, t, J=8.0Hz), 3.25 tive ESI-MS m/z: 226.1 [M−Br]+; negative ESI-MS m/z: 78.9
(2H, t, J=8.0Hz); 13C-NMR (125MHz, CDCl3) δ: 138.8, [79Br−], 80.9 [81Br−].
136.8, 130.4, 129.9, 128.8, 127.7, 36.8, 3.5, 3.2; ESI MS m/z:
2-(4-Fluorophenyl)-3,4-dihydroisoquinolin-2-ium Bromide
(5d): Pale yellow solid in 52% yield, mp 190–191°C; UV λmax
372.1[M+H]+.
Synthesis of 5a–x. General Procedure The solution (logε) (MeOH, pH 1.5) 203 (4.30), 223 (4.05), 316 (4.19) nm;
of 1 (3.72g, 10mmol), aniline or substituted aniline (2a–x) IR, ν (KBr) cm−1 1632 (s, C=N), 1239 (s, C–F); 1H-NMR
(10mmol), sodium hydrogen carbonate (1.68g, 20mmol) and (CD3OD) δ: 9.53 (H-1), 8.04–8.06 (1H, m), 7.88–7.92 (3H, m),
SDS (ca. 20mg) in 40mL of water was stirred under refluxing 7.59–7.64 (2H, m), 7.43 (2H, m), 4.64 (2H, t-like, J=7.2Hz),
for 2–3h. The reaction solution was cooled to room tempera- 3.52 (2H, t-like, J=7.2Hz); 13C-NMR (DMSO-d6) δ: 159.3
ture and extracted with ethyl acetate. The combined ethyl ace- (C-1), 155.5 (d, J=249.5Hz), 131.3, 130.7, 128.9, 126.8, 120.1
tate solution was washed with water and dried over anhydrous (d, J=14.4Hz), 117.2, 116.8 (d, J=9.1Hz), 108.6 (d, J=23.8Hz),
sodium sulfate. Evaporation of the solvent under reduced 43.4, 16.9; positive ESI-MS m/z: 226.1 [M−Br]+; negative ESI-
pressure furnished crude products 3a–x as a white or pale MS m/z: 78.9 [79Br−], 80.9 [81Br−].
yellow solid. The crude products 3a–x was dissolved in 20mL
2-(2-Chlorophenyl)-3,4-dihydroisoquinolin-2-ium Bromide
methanol, and then 2.0mmol of CuCl2·2H2O was added. The (5e): Milky-white solid in 85% yield, mp 199–200°C; UV λmax
resulting solution was refluxed for 10h under an oxygen atmo- (logε) (MeOH, pH 1.5) 203 (4.31), 301 (4.14) nm; IR, ν (KBr)-
1
sphere, and then passed through a pad of celite and washed cm−1 1636 (s, C=N); H-NMR (CD3OD) δ: 9.54 (1H, s, H-1),
with ca. 40mL of methanol. The combined filtrates were 8.06 (1H, d, J=7.6Hz), 7.96 (2H, t, J=7.6Hz), 7.79 (1H, d,
evaporated to dryness to afford 2-aryl-1-methoxy-1,2,3,4-tetra- J=8.0Hz), 7.70 (1H, d, J=7.6Hz), 7.65 (3H, t, J=7.6Hz), 4.52
hydroisoquinolines 4a–x as an oily residue. Compounds 4a–x (2H, t, J=8.0Hz, H-3), 3.58 (2H, t, J=8.0Hz, H-4); 13C-NMR
were dissolved in ca. 20mL 1,4-dioxane and dropwise added (CD3OD) δ: 170.2 (C-1), 138.9 (C-1′), 138.4, 136.2, 134.1,
ca. 2mL (ca. 14mmol) of 47% HBr aqueous solution to give 131.2, 129.6, 127.5, 127.2, 126.7, 125.5, 123.6, 51.1 (C-3), 23.8
the desired products 5a–x as solids.
(C-4); positive ESI-MS m/z: 242.1 [M−Br]+; negative ESI-MS
2-Phenyl-3,4-dihydroisoquinolin-2-ium Bromide (5a): White m/z: 78.9 [79Br−], 80.9 [81Br−].
solid in 89% yield calculated from 1 (the same below), mp
2-(3-Chlorophenyl)-3,4-dihydroisoquinolin-2-ium Bromide
106–108°C; UV λmax (logε) (MeOH, pH 1.5) 203 (4.33), (5f): Pale yellow solid in 65% yield, mp 206–208°C; UV λmax
244 (3.95), 314 (4.10) nm; IR, ν (KBr) cm−1 1635 (s, C=N); (logε) (MeOH, pH 1.5) 203 (4.37), 313 (4.10) nm; IR, ν (KBr)
1H-NMR (CD3OD) δ: 9.50 (1H, s, H-1), 8.02 (1H, d, J=7.6Hz), cm−1 1623 (s, C=N); 1H-NMR (DMSO-d6) δ: 9.74 (1H, s,
7.90 (1H, t, J=7.6Hz), 7.82–7.84 (2H, m), 7.65–7.70 (2H, m), H-1), 8.11 (1H, d, J=1.2Hz), 8.05 (1H, d, J=7.6Hz), 7.92 (1H,
7.60 (1H, t, J=7.6Hz), 7.53 (1H, d, J=7.6Hz), 7.39 (1H, d, dd, J=7.6, 1.2Hz), 7.88–7.90 (1H, m), 7.74 (1H, d, J=7.6Hz),
J=7.6Hz), 4.66 (2H, t, J=8.0Hz), 3.52 (2H, t, J=8.0Hz); 7.71 (1H, d, J=8.0Hz), 7.64 (1H, t, J=7.6Hz), 7.61 (1H, d,
13C-NMR (DMSO-d6) δ: 159.0 (C-1), 134.9 (C-1′), 130.6, 129.0, J=7.6Hz), 4.59 (2H, t, J=8.0Hz, H-4), 3.43 (2H, t, J=8.0Hz,
126.8, 122.7, 121.8, 120.5, 120.1, 117.2, 114.1, 42.8 (C-3), 16.5 H-3); 13C-NMR (DMSO-d6) δ: 168.0 (C-1), 143.8 (C-1′), 138.7,
(C-4); positive ESI-MS m/z: 208.1 [M−Br]+; negative ESI-MS 137.2, 135.1, 133.9, 131.7, 130.8, 128.5, 128.0, 125.4, 123.2,
m/z: 78.9 [79Br−], 80.9 [81Br−].
2-(2-Fluorophenyl)-3,4-dihydroisoquinolin-2-ium Bromide Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].
(5b): Light yellow solid in 86% yield, mp 175–176°C; UV 2-(4-Chlorophenyl)-3,4-dihydroisoquinolin-2-ium Bromide
121.9, 50.7 (C-3), 24.8 (C-4); positive ESI-MS m/z: 242.1 [M−
λmax (logε) (MeOH, pH 1.5) 203 (4.29), 221 (4.00), 307 (4.20) (5g): Pale yellow solid in yield 88%, mp 198–200°C (de-
1
nm; IR, ν (KBr) cm−1 1634 (s, C=N), 1236 (s, C-F); H-NMR composition); UV λmax (logε) (MeOH, pH 1.5) 203 (4.30),
(CD3OD) δ: 9.55 (1H, d, J=3.2Hz, H-1), 8.06 (1H, dd, J=3.2, 223 (4.12), 320 (4.16) nm; IR, ν (KBr) cm−1 1633 (s, C=N);
7.2Hz), 7.94 (1H, d, J=7.2Hz), 7.92 (1H, t, J=8.0Hz), 7.71 1H-NMR (CD3OD) δ: 9.52 (1H, s, H-1), 8.02 (1H, d, J=7.6Hz),
(1H, q-like, J=5.6Hz), 7.64 (2H, t, J=8.0Hz), 7.53 (1H, d, 7.91 (1H, t, J=7.6Hz), 7.84 (2H, d, J=8.8Hz), 7.70 (2H, d,
J=8.0Hz), 7.50 (1H, t, J=8.0Hz), 4.58 (2H, t, J=8.0Hz, H-3), J=8.8Hz), 7.64 (1H, t, J=7.6Hz), 7.62 (1H, d, J=7.6Hz), 4.63
3.53 (2H, t, J=8.0Hz, H-4); 13C-NMR(CD3OD) δ: 172.3 (C-1), (2H, t, J=8.0Hz, H-4), 3.51 (2H, t, J=8.0Hz, H-3); 13C-NMR
156.8 (d, J=251.7Hz, C-2′), 141.0, 139.1, 136.8, 134.6 (d, (DMSO-d6) δ: 167.3 (C-1), 141.5, 138.6, 137.1, 135.2, 130.0,
J=8.1Hz), 132.1 (d, J=10.9Hz), 129.9 (d, J=12.3Hz), 127.4 129.5, 128.4, 127.9, 125.5, 124.9, 124.6, 50.7, 24.8; positive
(br), 127.2, 127.1, 126.6, 118.7 (d, J=19.2Hz), 53.8, 26.6; posi- ESI-MS m/z: 242.1 [M−Br]+; negative ESI-MS m/z: 78.9
tive ESI-MS m/z: 226.1 [M−Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].
[79Br−], 80.9 [81Br−].
2-(2-Bromophenyl)-3,4-dihydroisoquinolin-2-ium Bromide
2-(3-Fluorophenyl)-3,4-dihydroisoquinolin-2-ium Bromide (5h): Light green solid in 87% yield, mp 252–254°C (de-
(5c): Pale orange solid in 89% yield, mp 93–94°C; UV λmax composition); UV λmax (logε) (MeOH, pH 1.5) 204 (4.28),
(logε) (MeOH, pH 1.5) 203 (4.23), 223 (3.92), 313 (4.12) nm; 220 (4.15), 301 (4.15) nm; IR, ν (KBr) cm−1 1641 (s, C=N);
IR, ν (KBr) cm−1 1630 (s, C=N), 1168 (s, C–F); 1H-NMR 1H-NMR (CD3OD) δ: 9.52 (1H, s, H-1), 8.04 (1H, d, J=8.0Hz),
(CD3OD) δ: 9.59 (1H, s, H-1), 8.07 (1H, d, J=7.6Hz), 7.92 7.90–7.98 (3H, m), 7.58–7.71 (3H, m), 4.50 (2H, t, J=8.0Hz),
(1H, t, J=7.6Hz), 7.71–7.78 (2H, m), 7.73 (1H, s), 7.64 3.60 (2H, t, J=8.0Hz); 13C-NMR (CD3OD) δ: 173.2 (C-1),
(1H, d, J=7.6Hz), 7.61 (1H, d, J=7.6Hz), 7.45 (1H, nonet, 143.5 (C-1′), 141.4, 139.1, 137.0, 135.7, 134.3, 131.1, 130.2,
J=3.2, 5.6, 8.0Hz), 4.66 (2H, t, J=8.0Hz, C-3′), 3.53 (2H, t, 128.4, 126.4, 118.9, 54.1, 26.8; positive ESI-MS m/z: 286.1
J=8.0Hz, C-4′); 13C-NMR (DMSO-d6) δ: 159.9 (C-1), 155.7 [M−Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].
(d, J=247.6Hz, C-3′), 136.0 (d, J=9.7Hz, C-1′), 131.0, 129.2,
2-(4-Bromophenyl)-3,4-dihydroisoquinolin-2-ium Bromide
127.1, 123.6 (d, J=8.9Hz), 120.2, 120.1, 117.1, 110.3, 109.6 (d, (5i): Yellow solid in 99% yield, mp 201–202°C; UV λmax (logε)

February 2013
209
(MeOH, pH 1.5) 202 (4.23), 225 (4.11), 322 (4.18) nm; IR, ν d, J=7.6Hz), 4.70 (2H, t, J=8.0Hz), 3.56 (2H, t, J=8.0Hz);
1
(KBr) cm−1 1632 (s, C=N); H-NMR (CD3OD) δ: 9.55 (1H, s, 13C-NMR (DMSO-d6) δ: 160.5 (C-1), 135.4, 131.1, 129.2, 127.2,
H-1), 8.04 (1H, d, J=7.6Hz), 7.90 (1H, t, J=7.6Hz), 7.83 (2H, 123.8 (q, J=33.0Hz, CF3), 123.0, 120.1 (d, J=14.0Hz), 119.3,
d, J=8.0Hz), 7.81 (2H, d, J=8.0Hz), 7.62 (1H, t, J=7.6Hz), 118.3, 117.2, 116.5, 113.8, 111.8, 43.3 (C-3), 16.9 (C-4); posi-
7.60 (1H, t, J=7.6Hz), 4.63 (2H, t, J=8.0Hz), 3.51 (2H, t, tive ESI-MS m/z: 276.1 [M−Br]+; negative ESI-MS m/z: 78.9
J=8.0Hz); 13C-NMR (CD3OD) δ: 169.1 (C-1), 143.6 (C-1′), [79Br−], 80.9 [81Br−].
140.6, 138.8, 136.7, 134.7, 130.0, 129.8, 127.0, 126.4, 125.8,
2-(4-Trifluoromethylphenyl)-3,4-dihydroisoquinolin-2-ium
52.9, 26.7; positive ESI-MS m/z: 286.1 [M−Br]+; negative ESI- Bromide (5o): Light yellow solid in 40% yield, mp 191–192°C;
MS m/z: 78.9 [79Br−], 80.9 [81Br−].
UV λmax (logε) (MeOH, pH 1.5) 203 (4.35), 223 (4.13), 311
2-(2-Iodophenyl)-3,4-dihydroisoquinolin-2-ium
Bromide (4.35) nm; IR, ν (KBr) cm−1 1630 (s, C=N), 1324 (vs, C–F);
(5j): Greyish-white solid in 80% yield, mp 263–264°C (de- 1H-NMR (CD3OD) δ: 9.65 (1H, s, H-1), 8.08 (3H, d-like,
composition); UV λmax (logε) (MeOH, pH 1.5) 204 (4.41), J=6.8Hz), 8.00 (2H, d-like, J=8.4Hz), 7.92 (1H, t, J=7.6Hz),
224 (4.28), 300 (4.20) nm; IR, ν (KBr) cm−1 1641 (s, C=N); 7.64 (1H, d, J=7.6Hz), 7.62 (1H, d, J=8.0Hz), 4.69 (2H, t,
1H-NMR (CD3OD) δ: 9.48 (1H, s, H-1), 8.16 (1H, d, J=7.6Hz), J=8.0Hz), 3.54 (2H, t, J=8.0Hz); 13C-NMR (DMSO-d6) δ:
8.01 (1H, d, J=7.6Hz), 7.97 (1H, t, J=7.6Hz), 7.80 (1H, dd, 160.5 (C-1), 137.6, 131.2, 129.3, 127.3, 120.3, 120.1, 118.9 (q,
J=1.2, 8.0Hz), 7.69 (1H, d, J=8.0Hz), 7.67 (1H, d, J=8.0Hz), J=14.8Hz, CF3), 117.2, 116.7, 115.3, 114.0, 43.1 (C-3), 16.9
7.65 (1H, t, J=7.6Hz), 7.42 (1H, dd, J=1.2, 8.0Hz), 4.45 (2H, (C-4); positive ESI-MS m/z: 276.1 [M−Br]+; negative ESI-MS
t-like, J=7.6Hz), 3.64 (2H, brs); 13C-NMR (CD3OD) δ: 173.1 m/z: 78.9 [79Br−], 80.9 [81Br−].
(C-1), 147.0, 142.0, 141.2, 138.7, 136.7, 133.8, 131.6, 130.0,
127.3, 126.2, 111.2, 93.7, 54.1, 26.7; positive ESI-MS m/z: 334.1 (5p): Yellowish green solid in 76% yield, mp 188–189°C; UV
[M−Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].
λmax (logε) (MeOH, pH 1.5) 202 (4.64), 301 (4.21) nm; IR,
2-(3-Iodophenyl)-3,4-dihydroisoquinolin-2-ium
2-(2-Nitrophenyl)-3,4-dihydroisoquinolin-2-ium
Bromide
Bromide ν (KBr) cm−1 1646 (s, C=N), 1527 (s, NO2), 1350 (s, NO2);
(5k): Orange solid in 71% yield, mp 132–133°C; UV λmax 1H-NMR (CD3OD) δ: 9.49 (1H, s, H-1), 8.51 (1H, d, J=8.4Hz),
(logε) (MeOH, pH 1.5) 206 (4.39), 227 (4.28), 311 (4.22) nm; 8.06 (1H, t, J=7.6Hz), 7.94–8.00 (4H, q-like, J=8.4Hz),
1
IR, ν (KBr) cm−1 1618 (s, C=N); H-NMR (CD3OD) δ: 9.53 7.65 (2H, t, J=8.0Hz), 4.56 (2H, t, J=8.0Hz), 3.60 (2H, br);
(1H, s, H-1), 8.25 (1H, s), 8.02 (2H, d, J=8.0Hz), 7.90 (1H, t, 13C-NMR (DMSO-d6) δ: 170.7 (C-1), 142.1, 140.9, 139.4, 137.1,
J=7.2Hz), 7.87 (1H, t, J=8.0Hz), 7.63 (1H, d, J=7.2Hz), 7.59 135.6, 135.4, 132.8, 129.0, 128.4, 126.6, 124.8, 109.3, 52.7,
(1H, d, J=7.2Hz), 7.44 (1H, t, J=8.0Hz); 13C-NMR (CD3OD) 25.0; positive ESI-MS m/z: 253.2 [M−Br]+; negative ESI-MS
δ: 169.5 (C-1), 145.3 (C-1′), 141.5, 140.6, 138.8, 136.7, 132.8, m/z: 78.9 [79Br−], 80.9 [81Br−].
132.7, 129.8, 129.7, 126.7, 123.9, 95.5, 52.8, 26.5; positive ESI-
2-(3-Nitrophenyl)-3,4-dihydroisoquinolin-2-ium
Bromide
MS m/z: 334.1 [M−Br]+; negative ESI-MS m/z: 78.9 [79Br−], (5q): Yellow solid in 76% yield, mp 218–220°C; UV λmax
80.9 [81Br−].
(logε) (MeOH, pH 1.5) 202 (4.32), 311 (4.23) nm; IR, ν (KBr)
1
2-(4-Iodophenyl)-3,4-dihydroisoquinolin-2-ium
Bromide cm−1 1640 (s, C=N), 1524 (s, NO2), 1347 (s, NO2); H-NMR
(5l): Yellow solid in 88% yield, mp 190–191°C; UV λmax (logε) (CD3OD) δ: 9.67 (1H, s, H-1), 8.76 (1H, s, H-2′), 8.51 (1H,
(MeOH, pH 1.5) 203 (4.74), 228 (4.54), 330 (4.52) nm; IR, d, J=8.0Hz), 8.27 (1H, d, J=7.2Hz), 8.06 (1H, d, J=7.2Hz),
1
ν (KBr) cm−1 1629 (s, C=N); H-NMR (CD3OD) δ: 9.53 (s, 7.96 (1H, d, J=8.0Hz), 7.92 (1H, d, J=7.2Hz), 7.65 (1H, d,
H-1), 8.04 (1H, d, J=7.6Hz), 8.02 (1H, d, J=7.6Hz), 7.89 (1H, J=7.6Hz), 7.62 (1H, d, J=7.6Hz), 4.70 (2H, t, J=8.0Hz), 3.55
d, J=8.0Hz), 7.61 (4H, q, J=7.6Hz), 7.18 (1H, d, J=8.0Hz), (2H, t, J=8.0Hz); 13C-NMR (DMSO-d6) δ: 161.0 (C-1), 150.2,
4.62 (2H, t, J=8.0Hz), 3.50 (2H, t, J=8.0Hz); 13C-NMR 140.7, 135.5, 131.3, 129.4, 127.3, 123.2, 120.2, 118.3, 117.1,
(DMSO-d6) δ: 159.3 (C-1), 134.5, 131.0, 130.9, 130.8, 126.9, 111.3, 110.0, 43.2, 16.9; positive ESI-MS m/z: 253.1 [M−Br]+;
120.2, 120.1, 117.2, 116.4, 115.8, 43.0, 16.9; positive ESI-MS negative ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].
m/z: 334.1 [M−Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9
2-(4-Nitrophenyl)-3,4-dihydroisoquinolin-2-ium
(5r): Yellow solid in 81% yield, mp 192–194°C; UV λmax
Bromide
[81Br−].
2-(2-Trifluoromethylphenyl)-3,4-dihydroisoquinolin-2-ium (logε) (MeOH, pH 1.5) 202 (4.44), 318 (4.31) nm; IR, ν (KBr)
1
Bromide (5m): Light yellow solid in 81% yield, mp cm−1 1634 (s, C=N), 1527 (s, NO2), 1344 (s, NO2); H-NMR
220–221°C; UV λmax (logε) (MeOH, pH 1.5) 203, 299; IR, ν (CD3OD) δ: 9.61 (1H, brs, H-1), 8.51 (2H, d, J=8.4Hz),
1
(KBr) cm−1 1633 (s, C=N), 1323 (vs, C–F); H-NMR (CD3OD) 8.02–8.05 (2H, m), 7.92 (1H, brs), 7.63 (2H, q-like, J=7.6Hz),
δ: 9.63 (1H, s, H-1), 7.92–8.08 (7H, m), 7.67 (1H, d, J=8.0Hz), 4.66 (2H, brs), 3.52 (2H, t, J=7.2Hz); positive ESI-MS m/z:
4.47 (1H, brs, H-3a), 4.45 (1H, brs, H-3b), 3.54 (2H, brs); 253.1 [M−Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9
13C-NMR (DMSO-d6) δ: 163.6 (C-1), 131.6, 131.1, 128.8, 127.1, [81Br−].
126.1, 123.3, 120.1, 119.2 (q, J=4.6Hz), 118.6, 116.0, 115.6,
2-(2-Methylphenyl)-3,4-dihydroisoquinolin-2-ium Bromide
115.7 (q, J=31.5.0Hz, CF3), 113.0, 45.0, 16.3; positive ESI-MS (5s): Orange solid in 62% yield, mp 94–96°C; UV λmax (logε)
m/z: 276.1 [M−Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9 (MeOH, pH 1.5) 203 (4.40), 299 (4.15) nm; IR, ν (KBr) cm−1
1
[81Br−].
1636 (s, C=N); H-NMR (DMSO-d6) δ: 9.57 (1H, s, H-1), 8.03
2-(3-Trifluoromethylphenyl)-3,4-dihydroisoquinolin-2-ium (1H, dd, J=8.0, 1.2Hz), 7.92 (1H, ddd, J=7.6, 1.2Hz), 7.74
Bromide (5n): Yellow solid in 60% yield, mp 179–180°C; (1H, d, J=7.6Hz), 7.62–7.66 (2H, m), 7.47–7.58 (3H, m), 4.43
UV λmax (logε) (MeOH, pH 1.5) 204 (4.34), 223 (4.06), 310 (2H, t, J=7.6Hz), 3.46 (2H, t, J=7.6Hz), 2.45 (3H, s, CH3);
(4.26) nm; IR, ν (KBr) cm−1 1627 (s, C=N), 1332 (vs, C–F); 13C-NMR (DMSO-d6) δ: 169.7 (C-1), 142.3 (C-1′), 138.6, 137.1,
1H-NMR (CD3OD) δ: 9.65 (1H, s, H-1), 8.28 (1H, s), 8.17 134.8, 132.2, 131.5, 128.6, 128.4, 128.1, 127.9, 127.1, 125.2,
(1H, d, J=8.0Hz), 8.08 (1H, d, J=7.6Hz), 8.00 (1H, d, J= 51.7 (C-3), 24.8 (C-4), 17.3; positive ESI-MS m/z: 222.1 [M−
7.6Hz), 7.90–7.94 (2H, m), 7.65 (1H, d, J=7.6Hz), 7.62 (1H, Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].

210
Vol. 61, No. 2
2-(3-Methylphenyl)-3,4-dihydroisoquinolin-2-ium Bromide Psoroptes cuniculi mites were isolated from naturally infected
(5t): Yellow solid in 60% yield, mp 61–63°C; UV λmax (logε) rabbits. The scabs and the cerumen, collected from the infect-
(MeOH, pH 1.5) 202 (4.32), 227 (4.07), 314 (3.93) nm; IR, ν ed ears, were observed by means of a stereoscopic microscope
1
(KBr) cm−1 1629 (s, C=N); H-NMR (DMSO-d6) δ: 9.68 (1H, to isolate adult mites of both sexes. Mites were collected with
s, H-1), 8.05 (1H, dd, J=7.6, 2.4Hz), 7.89 (1H, ddd, J=7.6, a needle and placed in 24-well flat-bottomed cell culture plates
1.2Hz), 7.75 (1H, s, H-2′), 7.69 (1H, d, J=8.0Hz), 7.65–7.60 (20 adult mites/each well). The compound (1.0mg) was dis-
(2H, m), 7.56 (1H, d, J=8.0Hz), 7.47 (1H, d, J=7.6Hz), solved in 0.5mL of the mixed solution of dimethyl sulfoxide
4.59 (2H, t, J=8.0Hz), 3.42 (2H, t, J=8.0Hz), 2.44 (3H, s); (DMSO) and Tween-80 (1:1, v/v), and then diluted with 2mL
13C-NMR (125MHz, DMSO-d6) δ: 166.6 (C-1), 142.8 (C-1′), normal saline to the concentration of 0.4mg/mL. Half millili-
139.7, 138.4, 137.0, 134.8, 131.6, 131.1, 129.9, 128.4, 125.5, ter of the solution was directly added to each well. Three rep-
123.2, 120.0, 50.6, 24.8, 21.0; positive ESI-MS m/z: 222.1 [M− licates were made for each compound. As untreated control,
Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].
three wells containing the same solution without the tested
2-(4-Methylphenyl)-3,4-dihydroisoquinolin-2-ium Bromide compound were used. All the plates were placed in separate
(5u): Yellow solid in 88% yield, mp 163–164°C; UV λmax humidity chambers in saturated humidity conditions at 22°C.
(logε) (MeOH, pH 1.5) 202 (4.32), 223 (3.99), 326 (4.10) nm; After 24h, each well was observed under a stereomicroscope
1
IR, ν (KBr) cm−1 1627 (s, C=N); H-NMR (CD3OD) δ: 9.44 for 5min and all the motionless mites were stimulated with a
(1H, s, H-1), 8.00 (1H, d, J=7.6Hz), 7.87 (1H, t, J=7.6Hz), needle. Lack of reactions and persistent immobility indicated
7.69 (2H, d, J=8.0Hz), 7.60 (1H, t, J=7.6Hz), 7.58 (1H, d, their death. Mortality was calculated as the following formula
J=7.6Hz), 7.48 (2H, d, J=8.0Hz), 4.61 (2H, t, J=8.0Hz), 3.49 and expressed as means S.D.
(2H, t, J=8.0Hz), 2.46 (3H, s); 13C-NMR (DMSO-d6) δ: 158.2
mortality (%)
(C-1), 133.7, 132.5, 130.4, 128.9, 126.6, 122.3, 120.1, 120.0,
117.3, 113.9, 43.2, 17.0, 11.7; positive ESI-MS m/z: 222.1 [M−
Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].
=(number of death mites / number of the tested mites)
×100
2-(2-Hydroxyphenyl)-3,4-dihydroisoquinolin-2-ium
Bro-
mide (5v): Brown solid in 80% yield, mp 193–194°C; UV
Acaricidal Toxicity Assay Based on the results above,
λmax (logε) (MeOH, pH 1.5) 203 (4.33), 299 (4.11) nm; IR, ν the compounds (5b, 5e–o, 5t, 5v) with stronger activity than
1
(KBr) cm−1 3421 (OH), 1637 (s, C=N), 1285 (C-O); H-NMR ivermectin were selected to determine their acaricidal toxicity
(CD3OD) δ: 9.35 (1H, s, H-1), 7.99 (1H, d, J=7.6Hz), 7.89 (1H, against Psoroptes cuniculi.
ddd, J=7.6, 1.6Hz), 7.59–7.63 (3H, m), 7.47 (1H, dddd, J=8.4,
Five milligram of the tested compound or ivermectin or
1.2Hz), 7.13 (1H, d, J=8.4Hz), 7.08 (1H, dddd, J=7.2, 1.2Hz), MSA was dissolved in 1.0mL of the mixed solution of DMSO
4.49 (2H, t, J=7.8Hz, H-3), 3.48 (2H, t, J=7.8Hz, H-4); and Tween-80 (1:1, v/v), and then diluted with 4.0mL normal
13C-NMR (CD3OD) δ: 170.6 (C-1), 152.1 (C-2′), 140.2, 138.8, saline to obtain a stock solution with a concentration of 1mg/
136.0, 133.8, 132.0, 129.8, 129.7, 126.7, 126.6, 121.6, 118.5, 53.1 mL. Two-fold serial dilutions were made by adding normal sa-
(C-3), 26.7 (C-4); positive ESI-MS m/z: 224.1 [M−Br]+; nega- line to obtain a series of concentrations of 1, 0.5, 0.25, 0.125,
tive ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].
0.0625, 0.0313, 0.0157 and 0.0078mg/mL. Untreated control
2-(4-Hydroxyphenyl)-3,4-dihydroisoquinolin-2-ium Bromide mites were treated with the same solution except for the tested
(5w): Yellowish green solid in 82% yield, mp 222–224°C; UV compound. The acaricidal activity for each concentration was
λmax (logε) (MeOH, pH 1.5) 202 (4.31), 226 (4.06), 284 (3.89), tested according to the same procedure described above. Each
364 (4.05) nm; IR, ν (KBr) cm−1 3427 (m, OH), 1635 (s, C= test was performed in triplicate. The mortality of mites for
1
N), 1283, 1227 (C–O); H-NMR (CD3OD) δ: 9.35 (1H, s, H-1), each test was calculated and then corrected by applying Ab-
7.98 (1H, d, J=7.6Hz), 7.86 (1H, t, J=7.6Hz), 7.65 (2H, d, J= bott’s formula.
8.8Hz), 7.01 (2H, d, J=8.8Hz), 7.61 (1H, t, J=7.6Hz), 7.59
corrected mortality (%)
(1H, d, J=7.6Hz), 4.59 (2H, t, J=8.0Hz, H-4), 3.47 (2H, t,
J=8.0Hz, H-3); 13C-NMR (DMSO-d6) δ: 164.6 (C-1), 159.5
% test mortality  % control mortality
=
×100
(C-4′), 136.6 (C-1′), 134.4, 128.3, 127.8, 125.6, 124.4, 124.0,
116.1, 116.0, 50.7 (C-3), 24.8 (C-4); positive ESI-MS m/z: 224.1
[M−Br]+; negative ESI-MS m/z: 78.9 [79Br−], 80.9 [81Br−].
100  control mortality
Probit value of the corrected mortality for each test con-
Bro- centration and the corresponding log[concentration (mg/L)]
2-(4-Methoxyphenyl)-3,4-dihydroisoquinolin-2-ium
mide (5x): Yellow solid in 85% yield, mp 163–164°C; UV were used to establish toxicity regression equation with the
λmax (logε) (MeOH, pH 1.5) 202 (4.32), 226 (4.13), 284 (3.89), linear least-square fitting method. The LC50 and its confidence
356 (4.08) nm; IR, ν (KBr) cm−1 1639 (s, C=N), 1253, 1041 interval at 95% probability were calculated from the toxicity
(C-O); 1H-NMR (CD3OD) δ: 10.27 (1H, s, H-1), 8.43 (1H, regression equation. CRA of each compound was calculated
d, J=7.6Hz), 8.01 (2H, d, J=8.8Hz), 7.70 (1H, t, J=7.6Hz), according to the following formula.
7.45 (1H, t, J=7.6Hz), 7.37 (1H, d, J=7.6Hz), 7.00 (2H, d,
slope value of the tested compound
slope value of ivermectin


J=8.8Hz), 4.57 (2H, t, J=8.0Hz, H-4), 3.79 (3H, s, OCH3),
3.48 (2H, t, J=8.0Hz, H-3); 13C-NMR (DMSO-d6) δ: 157.3
(C-1), 153.6 (C-4′), 130.2 (C-1′), 128.6, 127.7, 126.4, 120.1,
119.9, 117.3, 115.6, 106.8, 54.7 (OCH3), 43.3 (C-3), 17.0 (C-4);
positive ESI-MS m/z: 238.1 [M−Br]+; negative ESI-MS m/z:
78.9 [79Br−], 80.9 [81Br−].
CRA=




LC50 value of ivermectin


×



LC50 value of the test compound

Pharmacology. In Vitro Acaricidal Activity Assay
Acknowledgements This project was supported by the

February 2013
211
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