Synthesis and biological activity of n-butylphthalide derivatives

Article abstract of DOI:10.1016/j.ejmech.2010.01.036

A series of n-butylphthalide derivatives were designed and synthesized. The in vitro activities of these compounds were evaluated by a resting tension of isolated rat thoracic aorta ring assay. Compounds 4g and 4i were found to be more active than n-butylphthalide.

Full text of DOI:10.1016/j.ejmech.2010.01.036

European Journal of Medicinal Chemistry 45 (2010) 1941–1946
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and biological activity of n-butylphthalide derivatives
Wei Wang a, Xue-Xiang Cha b, John Reiner a, Yuan Gao b, Hai-Ling Qiao b, Jia-Xiang Shen a,
,b,
Jun-Biao Chang a
*
a College of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, PR China
b Department of Pharmacology, Basic Medical College of Zhengzhou University, Zhengzhou 450001, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of n-butylphthalide derivatives were designed and synthesized. The in vitro activities of these
compounds were evaluated by a resting tension of isolated rat thoracic aorta ring assay. Compounds 4g
and 4i were found to be more active than n-butylphthalide.
Received 19 September 2009
Received in revised form
15 January 2010
Accepted 15 January 2010
Available online 25 January 2010
Ó 2010 Elsevier Masson SAS. All rights reserved.
Keywords:
Vasorelaxant effects
Synthesis
n-Butylphalide
1. Introduction
pharmacological behavior is an important endeavor in drug design
[9]. Therearethreeimportantfactorsinthesubstitutionoffluorinefor
Cardiovascular and cerebrovascular disorders are the main
reason for morbidity and death in recent years. As reported, n-
butylphthalide (NBP), the primary naphtha component from seeds
of Apium graveolens Linn. has completed a phase 3 clinical trial and
was approved by the State Food and Drug Administration of China at
the end of 2002 as a new drug for the treatment of ischemic stroke in
the clinic [1]. Many basic and clinical studies have shown that NBP is
a potentially beneficial and promising drug for the treatment of
ischemic stroke with multiple actions that affect different patho-
physiological processes, such as improving microcirculation,
decreasing brain infarct volume, regulating energy metabolism,
inhibiting platelet aggregation, and reducing thrombus formation
[2–6]. However, drug safety evaluations have demonstrated the
main adverse effects of NBP to be liver dysfunction, with slight and
moderate increases in the levels of alanine aminotransferase and
aspartate aminotransferase, respectively [7].
hydrogen. First, fluorine is the third smallest element and can serve as
a replacement for hydrogen without a large steric change; Second,
fluorine is the most electronegative element, and its powerful elec-
tronwithdrawingpropertycanprofoundlyaffectchemicalreactivities
[10]; Last, the introduction of fluorine into biologically active mole-
cules often increases biological potency without increasing toxicity
[11]. In this study, the fluoro analogs of the various forms of NBP were
designed and synthesized for the first time, as well as some new
chloro and bromo analogs [12].
2. Chemistry
Compounds 4a–i were prepared from aminophthalide 1a–c as
showninScheme 1. Aminophthalide 1a–c were subjected to standard
Sandmeyer or Schieman reactions to give the halogenated derivatives
2a–i. Treatment of 2a–i with NBS in dry carbon tetrachloride
accordingtoliteratureprocedure[13,14], followedbyhydrolysisof the
intermediates gave compounds3a–i. Finally, thetargetmolecules 4a–
i were obtained by reacting 3a–i with BuMgBr in THF.
Compounds 8a–b were synthesized in three steps as outlined in
Scheme 2. Commercially available aldehydes 5a–b were converted to
acetals 6a–b according to a literature procedure [15]. Metalation of
6a–busingsec-butyllithiumfollowedbyreactionwithcarbondioxide
and then addition of HCl solution furnished hydroxyphthalides 7a
and 7b in 80% and 28% yield, respectively. The yields varied greatly. It
was also found that treatment of m-bromobenzaldehyde dimethyl
Recently, Yangandco-workershavereportedmodificationsofNBP
with different substituents at the 3-position [8]. However, as platelet
aggregation inhibitors, these derivatives were less active than NBP.
Substitution on the phthalide aromatic ring with fluorine, to the best
of our knowledge, has not been reported. Selective introduction of
fluorine into biologically active molecules for modification of their
* Corresponding author. College of Pharmaceutical Science and Technology,
Tianjin University, Tianjin 300072, PR China. Tel./fax: þ86 371 67783017.
E-mail address: changjunbiao@zzu.edu.cn (J.-B. Chang).
0223-5234/$ – see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.01.036

1942
W. Wang et al. / European Journal of Medicinal Chemistry 45 (2010) 1941–1946
R1
R1
O
R2
R3
COOH
COOH
R2
R3
i
i
ii
O
O
O
O
O
O
1a (R1=NH2, R2=R3=H)
1b (R2=NH2, R1=R3=H)
1c (R3=NH2, R1=R2=H)
2a-c (R1=F, Cl, Br, R2=R3=H)
2d-f (R2=F, Cl, Br, R1=R3=H)
2g-i
Br
Br
Br
11
10
9
(R3=F, Cl, Br, R1=R2=H)
iii
ii
OH
O
Bu
O
R1
R1
Bu
OH
iv
v
O
R2
R2
R3
iii
O
O
R3
O
O
O
Br
Br
Br
O
O
4a-c (R1=F, Cl, Br, R2=R3=H) 3a-c (R1=F, Cl, Br, R2=R3=H)
4d-f (R2=F, Cl, Br, R1=R3=H) 3d-f (R2=F, Cl, Br, R1=R3=H)
8c
12
13
3g-i
4g-i (R3=F, Cl, Br, R1=R2=H)
(R3=F, Cl, Br, R1=R2=H)
Scheme 3. Reagents and conditions: (i) KMnO4, cetyl trimethylammonium bromide,
H2O, 60 ꢀC, 4 days; (ii) Ac2O, reflux, 1 h; (iii) NaBH4, THF, 0 ꢀC, 20 h; (iv) (1) NBS, CCl4;
(2) H2O, reflux; (v) (1) BuMgBr, THF, reflux, 1.5 h; (2) Hþ, 40 ꢀC, 1 h.
Scheme 1. Reagents and conditions: (i) HBF4, NaNO2,
D
or HCl, NaNO2, CuCl, 0 ꢀC or
D; (ii) (1) NBS, CCl4; (2) H2O, reflux, 1 h; (iii) (1) BuMgBr, THF, reflux,
HBr, NaNO2, CuBr,
1.5 h; (2) Hþ, 40 ꢀC, 1 h.
and adherent connective tissue was cleaned. Second, the lower
thoracic aorta was cut into a 3–4 mm ring, and the ring was
mounted horizontally between two stirrups in an organ bath filled
with 20 mL K–H solution at 37 ꢀC, ventilated continuously with 95%
O2 and 5% CO2. Third, the ring was equilibrated for 60 min at 1.5 g
resting tension. Then, the test compound (5.0 ꢁ 10ꢂ5–8.0 ꢁ 10ꢂ4 M)
was cumulatively added into the organ bath in 10 min intervals, and
the vascular tension subtracted from the resting tension was
recorded. PEG-400 was also added into the organ bath as a control
and the compound NBP was used for comparison.
acetal with sec-butyllithium followed byaddition of CO2 and then HCl
solution did not afford the corresponding hydroxyphthalide. The
gradual decrease in electronegativity, as well as the gradual increase
in steric bulk from fluorine to bromine may account for these obser-
vations. Finally, targetcompounds8a–bcould beobtained byreacting
7a–b with BuMgBr in THF as described above.
Next, we investigated an alternative method for the synthesis of
7-bromo-3-n-butylphthalide 8c. As shown in Scheme 3, xylene 9
was oxidized to phthalic acid 10 with potassium permanganate.
Phthalic acid 10 was refluxed with acetic anhydride to yield phthalic
anhydride 11, which was then reduced with sodium borohydride to
give phthalide 12. The target compound 8c was prepared from 12 in
a similar manner to 4a–i as outlined in Scheme 1.
Norepinephrine (1.0 ꢁ 10ꢂ6 M) induced a similar sustained
contractionofaorticrings withapeaktensionineachgroup.Then, the
test compounds 4g, 4i and NBP (2.5 ꢁ 10ꢂ5–4.0 ꢁ 10ꢂ4 M) were
respective cumulativelyadded intothe organ bath in 10 min intervals.
The contractile responses were recorded as the ratio of the responses
following and before the application of the test compounds (second
response/first response), and the contraction induced by norepi-
nephrine before the application of vasodilators was recorded as 100%.
All results are expressed as mean ꢃ S.E.M. Statistical analysis
was performed with repeated-measures of the ANOVA. Differences
were accepted as statistically significant at P values <0.05.
3. Vasorelaxant effects
The in vitro relaxation activities of all compounds were evalu-
ated by a rat thoracic aorta assay. First, the thoracic aorta was
quickly isolated and immersed in oxygenated K–H solution at 4 ꢀC,
4. Results
CH(OCH3)2
CHO
i
The vasorelaxant effects of 4a–i and 8a–c were elucidated as
shown in Table 1. Compared with the PEG-400 control group,
compounds 4e, 4f, 4g and 4i (5.0 ꢁ 10ꢂ5–8.0 ꢁ 10ꢂ4 M) produced
dose-dependent relaxation. As shown in Table 1, Figs. 1 and 2,
compounds 4g and 4i are more active than NBP.
X
X
6a
, X=F
5a, X=F
6b, X=Cl
5b
, X=Cl
The rat thoracic aorta test also showed that compounds 4g and
4i can inhibit action of norepinephrine (1.0 ꢁ 10ꢂ6 M) in Ca2þ-free
ii
Medium. The IC50 of 4g and 4i are 131.53
mM and 106.91
mM
Bu
O
OH
O
respectively, while that of NBP is 130.06
mM (Fig. 3).
iii
A mouse acute toxicity test by way of intraperitoneal injection
gave LD50 for NBP and 4g of 592.93 mg/kg and 750.89 mg/kg
respectively. The LD50 for 4i is more than 1000 mg/kg.
O
O
X
X
8a, X=F
8b
7a,
5. Conclusions
X=F
, X=Cl
7b, X=Cl
In conclusion, a series of n-butylphthalide derivatives was
designed and synthesized. The activities of all compounds were
evaluated in vitro by a resting tension and NE-Induced Contractile
Scheme 2. Reagents and conditions: (i) trimethyl orthoformate, CH3OH, p-TsOH, rt,
1 h; (ii) (1) sec-BuLi,THF, ꢂ70 ꢀC; (2) CO2, -70 ꢀC; (3) Hþ; (iii) (1) BuMgBr, THF, reflux,
1.5 h; (2) Hþ, 40 ꢀC, 1 h.

W. Wang et al. / European Journal of Medicinal Chemistry 45 (2010) 1941–1946
1943
Table 1
Effects of NBP derivatives on the resting tension of isolated rat thoracic aorta rings (X ꢃ SEM, n ¼ 4).
Group
Concentration of drugs
50
m
M
100
m
M
200
m
M
400
m
M
800 mM
Control group
Group NBP
Group 4a
Group 4b
Group 4c
Group 4d
Group 4e
Group 4f
Group 4g
Group 4h
Group 4i
ꢂ0.002 ꢃ 0.009
ꢂ0.030 ꢃ 0.010*
ꢂ0.008 ꢃ 0.013
ꢂ0.010 ꢃ 0.042
þ0.025 ꢃ 0.038
ꢂ0.003 ꢃ 0.024
ꢂ0.027 ꢃ 0.021
ꢂ0.023 ꢃ 0.017*
ꢂ0.037 ꢃ 0.015*
ꢂ0.003 ꢃ 0.013
ꢂ0.027 ꢃ 0.038
þ0.000 ꢃ 0.008
ꢂ0.008 ꢃ 0.009
ꢂ0.015 ꢃ 0.031
þ0.001 ꢃ 0.020
ꢂ0.043 ꢃ 0.021*
ꢂ0.015 ꢃ 0.047
ꢂ0.032 ꢃ 0.037
þ0.023 ꢃ 0.040
ꢂ0.013 ꢃ 0.029
ꢂ0.030 ꢃ 0.017
ꢂ0.048 ꢃ 0.033*
ꢂ0.073 ꢃ 0.050*
þ0.020 ꢃ 0.056
ꢂ0.105 ꢃ 0.110*
ꢂ0.005 ꢃ 0.017
ꢂ0.010 ꢃ 0.014
þ0.015 ꢃ 0.017
ꢂ0.002 ꢃ 0.018
ꢂ0.063 ꢃ 0.035**
ꢂ0.010 ꢃ 0.024
ꢂ0.005 ꢃ 0.064
þ0.078 ꢃ 0.094
ꢂ0.020 ꢃ 0.054
ꢂ0.050 ꢃ 0.030*
ꢂ0.085 ꢃ 0.036*
ꢂ0.103 ꢃ 0.080*
þ0.018 ꢃ 0.081
ꢂ0.137 ꢃ 0.123*
ꢂ0.013 ꢃ 0.019
ꢂ0.023 ꢃ 0.026
þ0.023 ꢃ 0.026
þ0.002 ꢃ 0.021
ꢂ0.080 ꢃ 0.034*
ꢂ0.005 ꢃ 0.034
þ0.005 ꢃ 0.074
þ0.005 ꢃ 0.053
ꢂ0.020 ꢃ 0.071
ꢂ0.100 ꢃ 0.036*
ꢂ0.115 ꢃ 0.031**
ꢂ0.110 ꢃ 0.082*
þ0.050 ꢃ 0.054
ꢂ0.182 ꢃ 0.142*
ꢂ0.005 ꢃ 0.029
ꢂ0.038 ꢃ 0.043
þ0.023 ꢃ 0.040
þ0.003 ꢃ 0.018
ꢂ0.117 ꢃ 0.049*
ꢂ0.043 ꢃ 0.043
þ0.008 ꢃ 0.079
ꢂ0.030 ꢃ 0.049
ꢂ0.003 ꢃ 0.053
ꢂ0.147 ꢃ 0.025**
ꢂ0.115 ꢃ 0.039**
ꢂ0.150 ꢃ 0.131*
þ0.055 ꢃ 0.076
ꢂ0.222 ꢃ 0.160**
þ0.013 ꢃ 0.029
ꢂ0.053 ꢃ 0.062
þ0.028 ꢃ 0.053
Group 8a
Group 8b
Group 8c
*P < 0.05, **P < 0.01, þ means contraction, ꢂ means relaxation, n ¼ 4.
Responses of isolated rat thoracic aorta ring assay. Compounds 4g,
4i and NBP have vasorelaxant effects. Further testing of the activity
of these compounds will be carried out.
6.2. General procedure for the synthesis of 3-butyl-4-halogen-
1(3H)-isobenzofuranone (4a–c), 3-butyl-5-halogen-1(3H)-
isobenzofuranone (4d–f), 3-butyl-6-halogen-1(3H)-
isobenzofuranone (4g–i)
6. Experimental
6.2.1. Synthesis of 3-butyl-4-fluoro-1(3H)-isobenzofuranone (4a)
4-aminophthalide 1a (15.0 g, 60.0 mmo1) was dissolved in 6 M
hydrochloric acid (25 mL) and stirred vigorously while cooling with
an ice-salt mixture. When the temperature of the mixture has
reached 5 ꢀC or below, the diazotization is begun by the slow
addition of the sodium nitrite solution (7.0 g, 60.0 mmol), the
temperature being held below 5 ꢀC. The mixture was stirred for
0.5 h. The ice-cooled solution of fluoboric acid (20%, 60.0 mL) is
then poured in the diazonium solution, while maintaining the
temperature below 5 ꢀC during the addition. After 1 h stirring, the
6.1. Materials and methods
The reagents and solvents used in this study were of analytical
grade and were used without further purification. 1H NMR and 13
C
NMR were recorded on Bruker AV-300 spectrometers using TMS as
an internal reference. Melting points were determined on a SM/
XMT melting point apparatus and are uncorrected. High-resolution
mass spectra (HRMS-ESI) were obtained on a MicroÔ Q-TOF Mass
Spectrometer.
0.200
0.100
0.000
contr
NBP
0
100
200
300
400
500
600
700
800
900
4a
4b
4c
4d
4e
4f
-0.100
-0.200
-0.300
-0.400
-0.500
4g
4h
4i
8a
8b
8c
Concentration of test compounds (µmol/L)
Fig. 1. Effects of NBP derivatives on the resting tension of isolated rat thoracic aorta rings. *P < 0.05, compared with PEG-400.

1944
W. Wang et al. / European Journal of Medicinal Chemistry 45 (2010) 1941–1946
bromobutane was added to the flask, and the contents were stirred
until the Grignard reaction has started. When the initial vigorous
reaction had subsided the remainder of the 1-bromobutane solu-
tion was then added at a rate such that the mixture refluxed gently.
After complete addition, reflux was continued for 1 h by heating
with an oil bath. Finally, the reaction mixture was allowed to cool to
room temperature. A solution of 3a (1.74 g, 10.34 mmol) in tetra-
hydrofuran (17 mL) was added dropwise dropped into the Grignard
solution. After completion of addition, the reaction mixture was
heated at reflux for 1.5 h using an oil bath, then cooled. Saturated
aqueous ammonium chloride (10 mL) was carefully added. The
mixture was acidified with concentrated HCl until pH 2 and stirred
for 1 h at 40 ꢀC. The solution was extracted with ethyl acetate and
dried over anhydrous Na2SO4. The mixture was purified by column
chromatography to give the title compound 4a (0.78 g, 36.2%), mp:
*
*
*
*
38–40 ꢀC. 1H NMR (CDCl3, 300 MHz)
d
: 7.70 (1H, d, J ¼ 7.7 Hz), 7.53
(1H, dd, J ¼ 4.4, 8.1 Hz), 7.34 (1H, t, J ¼ 8.1 Hz), 5.61(1H, m), 2.21 (1H,
m), 1.80 (1H, m), 1.47–1.26 (4H, m), 0.91(3H, t, J ¼ 6.9 Hz). 13C NMR
Fig. 2. Effects of compounds 4g, 4i and NBP (50–800 mM) on the resting tension of rat
thoracic aorta rings. *P < 0.05, compared with PEG-400.
(CDCl3,75 MHz) d: 169.3, 156.8, 135.8, 131.3, 129.4, 121.6, 120.7, 79.6,
33.1, 26.8, 22.6, 22.5, 13.9. 19F NMR (CDCl3, 282 MHz)
d
: ꢂ119.73.
ESI-TOF/MS for C12H13FO2: calcd: 209.0978 [M þ H]þ. Found:
209.0972 [M þ H]þ.
mixture is filtered with suction. The solid is washed with cold
water, ethanol, diethyl ether and dried under vacuum. The solid is
heated at 250 ꢀC, and then the residue was purified by column
chromatography to give compound 2a (2.7 g, 17.6%), mp: 98–99 ꢀC.
6.2.2. Synthesis of 3-butyl-4-chloro-1(3H)-isobenzofuranone (4b)
A solution of 1a (3.2 g, 21.45 mmo1) in 6 mL of hydrochloric acid
(6 M) was placed in a three-neck flask and cooled in an ice bath. A
solution of sodium nitrite (1.5 g, 21.45 mmo1) in 6 mL of water
placed in the funnel was slowly added to the well-stirred mixture.
The temperature of the mixture was maintained between 0 ꢀC and
1H NMR (CDCl3, 300 MHz)
J ¼ 4.4, 7.9 Hz), 7.37 (1H, t, J ¼ 8.1 Hz), 5.38(2H, s).
d
: 7.74 (1H, d, J ¼ 7.7 Hz), 7.55 (1H, dt,
A mixture of 2a (2.1 g,13.59 mmo1), N-bromosuccinimide (2.4 g,
13.59 mmo1), and dry carbon tetrachloride (36 mL) were refluxed
for 30 min, and then the reaction mixture was exposed to the light
of an ordinary 100-W unfrosted light bulb placed 6–8 in. from the
flask. The end of the reaction is indicated by the disappearance of
N-bromosuccinimide from the bottom of the flask and accumula-
tion of succinimide at the top of the reaction mixture. The succi-
nimide was removed by filtration and the filtrate concentrated
under vacuum. 15 mL water was added to the residue and stirred
for 1 h. The reaction mixture was then placed in a refrigerator
overnight. The product was filtered, washed with ice water, and
dried in the air to give 3a.
5
ꢀC throughout the addition of the nitrite solution. The mixture
was stirred for 0.5 h. A solution of CuCl (2.1 g, 21.45 mmo1) in
hydrochloric acid is cooled to 0 ꢀC. The cold diazonium solution was
added to the well-stirred cuprous chloride solution portionwise.
The solution was stirred for 1 h at 0 ꢀC. The cold mixture was
allowed to warm up to room temperature and stirring was
continued for 1.5 h at this temperature, and then refluxed for 1.5 h.
The solution was extracted with ethyl acetate and dried over
anhydrous Na2SO4. The mixture was purified by column chroma-
tography to give the title compound 2b (2.4 g, 66.9%), mp: 88–89 ꢀC.
The compound 4b was prepared from 2b (2.3 g, 13.64 mmo1) as
described for compound 4a to give a white powder (1.0 g, 33.0%),
Under nitrogen atmosphere a 50 mL, three-neck, round-bottom
flask, fitted with a reflux condenser, pressure-equalized addition
funnel, and a thermometer, was charged with magnesium turnings
(0.70 g, 28.33 mmol) and 5 mL of dry ether. The dropping funnel
was charged with the 1-bromobutane. At first, 0.5 mL of 1-
mp: 53–54 ꢀC. 1H NMR (CDCl3, 300 MHz)
d
: 7.80 (1H, d, J ¼ 7.7 Hz),
7.62 (1H, d, J ¼ 7.8 Hz), 7.48 (1H, t, J ¼ 7.7 Hz), 5.54 (1H, m), 2.37 (1H,
m), 1.83 (1H, m), 1.45–1.29 (4H, m), 0.91(3H, t, J ¼ 6.9 Hz). 13C NMR
(CDCl3, 75 MHz) d: 169.3, 146.8, 134.4, 130.7, 128.7, 128.7, 124.1, 81.1,
31.7, 26.5, 22.3, 14.0. ESI-TOF/MS for C12H13ClO2: calcd: 225.0682
[M þ H]þ. Found: 225.0675 [M þ H]þ.
6.2.3. Synthesis of 3-butyl-4-bromo-1(3H)-isobenzofuranone (4c)
A mixture of 1a (2.3 g, 15.21 mmo1) and 8 mL hydrobromic acid
(40%) in a three-neck flask was cooled in an ice bath. A solution of
sodium nitrite (1.1 g, 15.21 mmo1) in 5 mL of water was added
slowly, while stirring, the temperature being kept below 5 ꢀC. In the
meantime, a mixture of cuprous bromide (1.3 g, 9.13 mmo1) and
10 mL of hydrobromic acid (40%) was heated to 70–75 ꢀC in a three-
neck round-bottom flask. The diazonium solution was rapidly
poured into the cuprous bromide-hydrobromic acid solution. When
the addition was complete, the solution was stirred for 2 h. The
solution was cooled to room temperature and extracted with ethyl
acetate. The organic layer dried over anhydrous Na2SO4. The
product was purified by column chromatography to give the title
compound 2c (1.9 g, 59.2%), mp: 102–103 ꢀC.
*
**
**
**
The compound 4c was prepared from 2c (3.1 g, 14.48 mmo1) as
described for compound 4a to give a white powder (2.0 g, 46.6%),
Fig. 3. Vasorelaxant effects of compounds 4g, 4i and NBP (25–400 mM) on Norepi-
nephrine (1.0 ꢁ 10ꢂ6 M) – Induced Contractile Responses of Aortic Rings. *P < 0.05,
**P < 0.01, compared with PEG-400.
mp 39–41 ꢀC. 1H NMR (CDCl3, 300 MHz)
d
: 7.85 (1H, dd, J ¼ 1.1,

W. Wang et al. / European Journal of Medicinal Chemistry 45 (2010) 1941–1946
1945
7.7 Hz), 7.79 (1H, dd, J ¼ 1.1, 7.7 Hz), 7.42 (1H, dt, J ¼ 0.7, 7.7 Hz), 5.48
6.3. General procedure for the synthesis of 3-butyl-7-halogen-
1(3H)-isobenzofuranone (8a–c)
(1H, m), 2.38 (1H, m), 1.85 (1H, m), 1.41–1.26 (4H, m), 0.89 (3H, t,
J ¼ 7.0 Hz). 13C NMR (CDCl3, 75 MHz)
d: 169.3, 148.8, 137.5, 130.8,
128.8, 124.7, 116.6, 82.0, 31.6, 26.5, 22.2, 13.8. ESI-TOF/MS for
6.3.1. Synthesis of 3-butyl-7-fluoro-1(3H)-isobenzofuranone (8a)
A mixture of m-fluorobenzaldehyde (20.0 g, 161.2 mmol), tri-
methyl orthoformate (20 mL), methanol (100 mL), and p-toluene-
sulfonic acid (0.2 g) was stirred at room temperature for 1 h. The
reaction mixture was quenched with 1% CH3OH/KOH (40 mL),
concentrated in vacuo, and then worked up as usual to afford after
distillation the dimethyl acetal 6a.
To a ꢂ70 ꢀC solution of the dimethyl acetal from above (5.3 g,
31 mmol) in THF (35 mL) was added dropwise sec-butyllithium
(22.2 mL of a 1.4 M solution in hexane), and the red solution was
stirred for 0.5 h. The solution was saturated with CO2 for 5 min with
theredcolordisappearingtoyieldalightyellowsolution. After10min
the reaction mixture was allowed to warm to room temperature, and
after 30 min HCl (3.5 mL) was added. After concentration the solution
was made basic with 5% KOH (25 mL), the neutral material extracted
with diethyl ether, the base layer acidified to pH 1 with HCl, and the
product extracted with ethyl acetate. Workup as usual afforded 7a.
The compound suitable for use in the next step.
C12H13BrO2: calcd: 269.0177 [M þ H]þ. Found: 269.0172 [M þ H]þ.
6.2.4. Synthesis of 3-butyl-5-fluoro-1(3H)-isobenzofuranone (4d)
Compound 4d was synthesized according to the method
described previously. Yield: 4.0%, yellow oil. 1H NMR (CDCl3,
300 MHz)
d
: 7.88 (1H, dd, J ¼ 4.8, 8.4 Hz), 7.24 (1H, dd, J ¼ 2.2, 8.7 Hz),
7.16 (1H, dt, J ¼ 2.2, 7.8 Hz), 5.46 (1H, m), 2.03 (1H, m), 1.81 (1H, m),
1.44–1.38 (4H, m), 0.89 (3H, t, J ¼ 7.0 Hz).13C NMR (CDCl3, 75 MHz)
d:
169.4,166.5,152.8,128.1,122.2,117.3,109.1, 80.7, 32.3, 26.7, 22.4,13.8.
19F NMR (CDCl3, 282 MHz)
d: ꢂ103.44. ESI-TOF/MS for C12H13FO2:
calcd: 209.0978 [M þ H]þ. Found: 209.0974 [M þ H]þ.
6.2.5. Synthesis of 3-butyl-5-chloro-1(3H)-isobenzofuranone(4e)
Compound 4e was synthesized according to the method
described previously. Yield: 14.7%, white solid. mp: 68–70 ꢀC. 1H
NMR (CDCl3, 300 MHz)
d
: 7.82 (1H, d, J ¼ 8.1 Hz), 7.49 (1H, d,
J ¼ 8.1 Hz), 7.43(1H, s), 5.43(1H, m), 2.03 (1H, m), 1.79 (1H, m), 1.49–
1.33 (4H, m), 0.91(3H, t, J ¼ 7.1 Hz). 13C NMR (CDCl3, 75 MHz)
d:
The compound 8a was prepared from 7a (9.1 g, 54.13 mmol) as
described for compound 4a to give a white powder (5.3 g, 46.8%),
169.4, 151.7, 140.7, 129.8, 126.9, 124.8, 122.2, 80.8, 34.3, 26.8, 22.4,
13.8. ESI-TOF/MS for C12H13ClO2: calcd: 225.0682 [M þ H]þ. Found:
225.0686 [M þ H]þ.
mp: 41–42 ꢀC. 1H NMR (CDCl3, 300 MHz)
d
: 7.66 (1H, dt, J ¼ 4.4,
7.7 Hz), 7.22 (1H, d, J ¼ 7.7 Hz), 7.15 (1H, t, J ¼ 8.4 Hz), 5.46 (1H, m),
2.04 (1H, m), 1.77 (1H, m), 1.46–1.35(4H, m), 0.91(3H, t, J ¼ 7.1 Hz).
6.2.6. Synthesis of 3-butyl-5-bromo-1(3H)-isobenzofuranone (4f)
Compound 4f was synthesized according to the method
described previously. Yield: 19.7%, white solid. mp: 74–76 ꢀC. 1H
13C NMR (CDCl3, 75 MHz)
d: 166.5, 161.1, 157.6, 152.6, 136.5, 117.7,
115.7, 80.9, 34.1, 26.6, 22.1, 13.6. 19F NMR (CDCl3, 282 MHz)
d:
ꢂ115.24. ESI-TOF/MS for C12H13FO2: calcd: 209.0978 [M þ H]þ.
NMR (CDCl3, 300 MHz)
d
: 7.75(1H, d, J ¼ 8.1 Hz), 7.67 (1H, d,
Found: 209.0971 [M þ H]þ.
J ¼ 8.1 Hz), 7.61(1H, d, J ¼ 0.7 Hz), 5.44(1H, m), 2.02 (1H, m), 1.75
(1H, m), 1.41–1.26 (4H, m), 0.90(3H, t, J ¼ 7.0 Hz). 13C NMR (CDCl3,
6.3.2. Synthesis of 3-butyl-6-chloro-1(3H)-isobenzofuranone (8b)
Compound8bwassynthesizedaccordingtothemethoddescribed
above. Yield: 9.1%, white solid. mp: 48–49 ꢀC. 1H NMR (CDCl3,
75 MHz) d: 169.5, 146.7, 134.3, 132.6, 129.4, 127.0, 125.7, 80.7, 34.3,
26.8, 22.34, 13.8. ESI-TOF/MS for C12H13BrO2: calcd: 269.0177
[M þ H]þ. Found: 269.0166 [M þ H]þ.
300 MHz)
d
: 7.59 (1H, t, J ¼ 7.7 Hz), 7.46 (1H, d, J ¼ 7.7 Hz), 7.34 (1H, d,
J ¼ 7.7 Hz), 5.42 (1H, m), 2.04 (1H, m),1.75 (1H, m),1.49–1.33 (4H, m),
6.2.7. Synthesis of 3-butyl-6-fluoro-1(3H)-isobenzofuranone (4g)
Compound 4g was synthesized according to the method
described previously. Yield: 6.7%, white solid. mp: 45–47 ꢀC. 1H
0.90(3H, t, J ¼ 7.1 Hz). 13C NMR (CDCl3, 75 MHz)
d: 167.5, 152.5, 134.9,
133.3, 130.4, 122.9, 120.1, 79.9, 34.4, 26.8, 22.4, 13.8. ESI-TOF/MS for
C12H13ClO2: calcd: 225.0682 [M þ H]þ. Found: 225.0675 [M þ H]þ.
NMR (CDCl3, 300 MHz) d: 7.56–7.38 (3H, m), 5.46(1H, m), 2.02 (1H,
m), 1.74 (1H, m), 1.49–1.23(4H, m), 0.92(3H, t, J ¼ 7.2 Hz). 13C NMR
6.3.3. Synthesis of 3-butyl-6-bromo-1(3H)-isobenzofuranone (8c)
2,3-Dimethylbromobenzene (50.8 g, 274.7 mmol), water
(300 mL), cetyl trimethylammonium bromide (0.05 g) were placed
in a round-bottom flask equipped with a condenser. KMnO4 (174.0 g,
990.8 mmol) was added in several portions to the reaction mixture
and vigorously stirred at 60 ꢀC. The reaction took approximately 4
days. MnO2 was filtered and the filtrate acidified at 0 ꢀC with
concentrated HCl until pH 1. Repeated extractions with ether gave
10. The compound 10 was refluxed for 1 h with acetic anhydride
(24.0 g) and then cooled in an ice bath. The formed white crystals
were filtered, washed with cold ether. The suspension of crushed
NaBH4 (10 mmol, dried at 120 ꢀC in vacuum), in dry tetrahydrofuran
(120 mL), was refluxed for 15 min and then cooled in an ice bath. A
solution of 10 (3.6 g, 16.0 mmol) in dry tetrahydrofuran (80 mL) was
added dropwise to a stirred, ice-cold suspension of NaBH4. The
stirring was continued for 20 h. After quenching with 3 N HCl (to pH
1), 10 mL water was added and stirring continued overnight. The
solution was extracted with diethyl ether and dried over anhydrous
Na2SO4. The mixture was purified by column chromatography to
give the 12. The target compound 8c (0.6 g, 29.7%) was prepared
from 12 (1.1 g, 7.70 mmo1) in a similar manner to 4a–i as outlined in
(CDCl3, 75 MHz) d: 169.4, 163.1, 145.6, 129.3, 123.4, 121.9, 112.0, 81.3,
34.5, 26.8, 22.4, 13.8. 19F NMR (CDCl3, 282 MHz)
d
: ꢂ112.17. ESI-TOF/
MS for C12H13FO2: calcd: 231.0797 [M þ Na]þ. Found: 231.0804
[M þ Na]þ.
6.2.8. Synthesis of 3-butyl-6-chloro-1(3H)-isobenzofuranone (4h)
Compound 4h was synthesized according to the method
described previously. Yield: 13.7%, white solid. mp: 69–70 ꢀC. 1H
NMR (CDCl3, 300 MHz)
d
: 7.85 (1H, d, J ¼ 1.8 Hz), 7.63 (1H, dd,
J ¼ 1.8, 8.1 Hz), 7.37 (1H, dd, J ¼ 0.7, 8.1 Hz), 5.46(1H, m), 2.04 (1H,
m), 1.76 (1H, m), 1.48–1.35 (4H, m), 0.91(3H, t, J ¼ 7.0 Hz). 13C NMR
(CDCl3, 75 MHz) d: 169.1,148.2,135.3,134.2, 128.0,125.6,123.0, 81.3,
34.3, 26.8, 22.4, 13.8. ESI-TOF/MS for C12H13ClO2: calcd: 225.0682
[M þ H]þ. Found: 225.0674 [M þ H]þ.
6.2.9. Synthesis of 3-butyl-6-bromo-1(3H)-isobenzofuranone (4i)
Compound 4i was synthesized according to the method
described previously. Yield: 12.9%, white solid. mp: 73–75 ꢀC. 1H
NMR (CDCl3, 300 MHz)
d
: 8.02 (1H, d, J ¼ 1.8 Hz), 7.77 (1H, dd,
J ¼ 1.8, 8.1 Hz), 7.32 (1H, d, J ¼ 8.1 Hz), 5.43(1H, m), 2.03 (1H, m),
1.76 (1H, m), 1.56–1.35 (4H, m), 0.90(3H, t, J ¼ 7.1 Hz). 13C NMR
Scheme 1. 1H NMR (CDCl3, 300 MHz)
d
: 7.67 (1H, d, J ¼ 7.7 Hz), 7.50
(CDCl3, 75 MHz)
d
: 168.9, 148.7, 136.9, 128.6, 128.3, 123.3, 122.9,
(1H, t, J ¼ 7.7 Hz), 7.38 (1H, d, J ¼ 7.7 Hz), 5.40 (1H, m), 2.03 (1H, m),
81.3, 34.2, 26.7, 22.3, 13.8. ESI-TOF/MS for C12H13BrO2: calcd:
1.76 (1H, m), 1.61–1.35 (4H, m), 0.90 (3H, t, J ¼ 7.1 Hz). 13C NMR
269.0177 [M þ H]þ. Found: 269.0178 [M þ H]þ.
(CDCl3, 75 MHz) d: 167.9, 152.6, 134.8, 133.7, 124.5, 121.0, 120.7, 79.6,

1946
W. Wang et al. / European Journal of Medicinal Chemistry 45 (2010) 1941–1946
[3] C.T. Yan, Y.P. Feng, J.T. Zhang, Acta Pharmacol. Sin 19 (1998) 117–120.
[4] H.L. Xu, Y.P. Feng, Acta Pharmacol. Sin 21( (2000) 433–438.
[5] H.L. Xu, Y.P. Feng, Acta Pharmacol. Sin 36 (2001) 329–333.
[6] G.X. Dong, Y.P. Feng, Acta Acad. Med. Sinicae 24 (2002) 93–97.
[7] Y. Xie, S.H. Jin, G.P. Zhou, D. Li, Z.H. Ren, Chin. J. Contemp. Neurol. Neurosurg. 6
(3) (2006) 178–181.
34.4, 26.8, 22.4, 13.8. ESI-TOF/MS for C12H13BrO2: calcd: 269.0177
[M þ H]þ. Found: 269.0174 [M þ H]þ.
Acknowledgement
[8] H. Yang, G.Y. Hu, J. Chen, Y. Wang, Z.H. Wang, Bioorg. Med. Chem. Lett. 17
(2007) 5210–5213.
[9] M.E. Van Dort, Jung Yong-Woon, P.S. Sherman, M.R. Kilbourn, D.M. Wieland, J.
Med. Chem. 38 (1995) 810–815.
[10] V.E. Marquez, C.K.-H. Tseng, H. Mitsuya, S. Aoki, J.A. Kelley, H. Ford Jr., J.S. Roth,
S. Broder, D.G. Johns, J.S. Driscoll, J. Med. Chem. 33 (1990) 978–985.
[11] G.H. Posner, D.J. McGarvey, C.H. Oh, N. Kumar, S.R. Meshnick,
W. Asawahasadka, J. Med. Chem. 38 (1995) 607–612.
We are indebted to the National Natural Science Foundation of
China (NO. 20672030) and the Outstanding Young Scholarship of
the NSFC (NO. 30825043) for funding. Finally, we are grateful to
Professor Jingxi Xie for his many helpful suggestions to improve the
manuscript.
[12] J.B. Chang, C.N. Patent 101029037 A; 2007.
References
[13] I.A. Koten, R.J. Sauer, Org. Synth. 42 (1962) 26–27.
[14] R.L. Shriner, F.J. Wolf, Org. Synth. 23 (1943) 74–77.
[15] J.N. Freskos, G.W. Morrow, J.S. Swenton, J. Org. Chem. 50 (1985) 805–
810.
[1] Y. Zhang, L. Wang, J. Li, X.L. Wang, J. Pharmacol. Exp. Ther. 317 (2006) 973–979.
[2] Z.Z. Chong, Y.P. Feng, Acta Pharmacol. Sin 18 (1997) 505–508.