Discovery and synthesis of novel luteolin derivatives as DAT agonists

Article abstract of DOI:10.1016/j.bmc.2010.09.049

Luteolin, 5,7-dihydroxy-2-(3,4-dihydroxyphenyl)-4H-chromen-4-one, has been proposed and proved to be a novel dopamine transporter (DAT) activator. In order to develop this potential of luteolin, a series of novel luteolin derivatives were designed, synthesized, and evaluated for their DAT agonistic activities, utilizing constructed Chinese hamster ovary (CHO) cell lines stably expressing rat DAT. Biological screening results demonstrated that luteolin derivatives 1d, 1e, and 4c carry great DAT agonistic potency (EC₅₀ = 0.046, 0.869, and 1.375 μM, respectively) compared with luteolin 8 (EC₅₀ = 1.45 ± 0.29 μM). Luteolin derivative 1d, notably, exhibited a 32-fold-higher DAT agonistic potency than luteolin. These luteolin derivatives represent a novel DAT agonist class, from which lead compounds useful for exploration of additional novel DAT agonists could be drawn.

Full text of DOI:10.1016/j.bmc.2010.09.049

Bioorganic & Medicinal Chemistry 18 (2010) 7842–7848
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Discovery and synthesis of novel luteolin derivatives as DAT agonists
Jiange Zhang a, , Xianbo Liu a,b, Xinsheng Lei b, , Lei Wang a, Lihe Guo c, , Gang Zhao c, Guoqiang Lin b
⇑
⇑
⇑
a Department of Medicinal Chemistry, School of Pharmaceutical Science, Zhengzhou University, Zhengzhou 450001, China
b Department of Medicinal Chemistry, School of Pharmacy, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
c Cell Star Bio-Technologies Co., Ltd, 898 Halei Road, Shanghai 201203, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Luteolin, 5,7-dihydroxy-2-(3,4-dihydroxyphenyl)-4H-chromen-4-one, has been proposed and proved to
be a novel dopamine transporter (DAT) activator. In order to develop this potential of luteolin, a series
of novel luteolin derivatives were designed, synthesized, and evaluated for their DAT agonistic activities,
utilizing constructed Chinese hamster ovary (CHO) cell lines stably expressing rat DAT. Biological screen-
ing results demonstrated that luteolin derivatives 1d, 1e, and 4c carry great DAT agonistic potency
Received 17 August 2010
Revised 20 September 2010
Accepted 21 September 2010
Available online 25 September 2010
(EC50 = 0.046, 0.869, and 1.375 lM, respectively) compared with luteolin 8 (EC50 = 1.45 0.29 lM). Lute-
Keywords:
Luteolin
Dopamine transporter
Agonist
Synthesize
olin derivative 1d, notably, exhibited a 32-fold-higher DAT agonistic potency than luteolin. These luteolin
derivatives represent a novel DAT agonist class, from which lead compounds useful for exploration of
additional novel DAT agonists could be drawn.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
abuse have been reviewed elsewhere.9 Nonetheless, to date, no
practical pharmaceutical can act as DAT agonists, which we assume
Psychiatric and neurological diseases compromise the health of
multiple millions of people. Neurotransmitters such as dopamine
(DA), noradrenaline (NA), and serotonin (5-HT), for example, have
been implicated as playing key roles in psychiosis and neurogenic
diseases. Dopamine, one of the most important neurotransmitters,
affects brain processes, causing diseases as dopaminergic
neurotransmission dysfunction in the central nervous system
(CNS),1–3 such as Parkinson’s disease (PD), schizophrenia, atten-
tion-deficit hyperactivity disorder, and drug addiction.4,5
In response to certain physiological actions, DA is released from
nerve cells into the synapses, where it binds to its receptors on the
postsynaptic membrane. DA is inactivated mainly by reuptake via
the dopamine transporter (DAT), the monamine transport protein
on the presynaptic membrane of dopaminergic neurons existing
in areas of the brain where DA signaling is common.6 Thus, DAT
plays a key role in regulating dopaminergic signaling in the brain
by mediating rapid clearance of dopamine from the synaptic clefts
and then it is involved in a number of DA-related disorders, includ-
ing attention-deficit hyperactivity disorder, bipolar disorder, clini-
cal depression, and alcoholism.7,8
would act by positively modulating DAT activity, an opposing effect
of the transporter antagonists. DAT agonists, significantly, strength-
en the DAT’ reuptake action, thereby relieve psychiosis or neuro-
genic diseases caused by DA accentuation. Lihe Guo et al. were the
firstto propose andto provethatthe DATcanbe agitated by thepoly-
phenolic plant-derived flavonoids luteolin and apigenin.10,11 These
two compounds possess actions of enhancing monoamine uptake
either upon monoamine-transporter transgenic Chinese hamster
ovary (CHO) cells or upon wild dopaminergic cell lines, with higher
specificity for dopamine (DA) uptake than for norepinephrine (NE)-
and serotonin (5-HT)-uptake. Therefore, luteolin and apigenin can
be regarded as novel monoamine-transporter activators. However,
the DAT agonistic potency and efficacy of luteolin are stronger than
that of apigenin. Luteolin was thereby chosen as the candidate com-
pound to be used in our study.
In the present study, luteolin was chosen as lead compounds for
exploration of novel compounds with more DAT agonistic activities
and better water-solubility. A series of novel luteolin derivatives,
5-acylluteolin derivatives 1a–i, 5-alkylluteolin derivatives 2a–k,
7-alkylluteolin derivatives 3a–e, 7-acylluteolin derivatives 4a–c,
5,7-dimethylluteolin derivative 5a, 30,40-dialkylluteolin derivative
5b, 40-alkylluteolin derivatives 6a,b and 30-alkylluteolin derivatives
7a,b, thus were synthesized and screened using a transgenic CHO
(Tr-CHO) cell-line system and discovered that luteolin derivatives
1d, 1e, and 4c exhibited more DAT agonistic activities than luteo-
lin, especially, compound 1d exhibited a 32-fold-higher DAT ago-
nistic potency than luteolin.
In the last 20 years, several classes of DAT antagonists that were
tested preclinically for their potential as treatments for stimulant
⇑
Corresponding authors. Tel.: +86 371 6778 1908 (J.Z.); tel.: +86 21 51980128
(X.L.).
E-mail addresses: jgzhang5500@hotmail.com (J. Zhang), leixs@fudan.edu.cn (X.
Lei), lhguo@sibs.ac.cn (L. Guo).
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.09.049

J. Zhang et al. / Bioorg. Med. Chem. 18 (2010) 7842–7848
7843
in 10 with the respective halogenated hydrocarbons and K2CO3
provided compounds 14a–e. Cleavage of the dibenzal groups of
14a–e with a mixture of acetic acid and water (4:1) gave the cor-
responding 7-alkylluteolin derivatives 3a–e. The requisite esters
4a–c were prepared by condensation of 10 with the equivalent
respective acyl chlorides and KOH or K2CO3, followed by the
hydrogenolysis of dibenzal groups of 15a–c with palladium
hydroxide in EtOH–THF at rt, producing good yields. However,
the dibenzal groups of 15a–c were partially hydrogenised if they
were treated with a mixture of acetic acid and water (4:1).
Compound 10 was treated with 2 equiv MeI and K2CO3 to
produce 5,7-dimethylluteolin derivative 16. Subsequently, 5,7-dim-
ethylluteolin derivative 5a was synthesized by removalof the diben-
zal group with a mixture of acetic acid and water (4:1). The
corresponding displacement reaction using 2-iodopropane or 1-
iodo-2-methylpropane instead of MeI did not proceed, perhaps be-
cause slightly large groups can cause steric hindrance, only 5,7-dim-
ethylluteolin derivative 5a was obtained (Scheme 3).
2. Chemistry
Since the structure of luteolin 8 contains polyphenolic groups,
and its four phenolic hydroxyls posses different reactivities, for
example, in the acetylation reaction, the order from strong to weak
is 40-, 7->30->5-, hence, addition of different substituent groups at
certain positions on the luteolin ring is feasible. 5-Acylluteolin
derivatives 1a–i and 5-etherluteolin derivatives 2a–k were pre-
pared according to Scheme 1. The key intermediate 9 was synthe-
sized by treatment of luteolin 8 with 3 equiv amounts of benzyl
bromide and K2CO3 in dimethyl formamide (DMF). Compounds
12a–i were synthesized by esterification of 9 with excess respec-
tive acyl chlorides and NaH in CH2Cl2 or with the carboxylic acids,
DCC, and DMAP in CH2Cl2 at room temperature. These syntheses
were accomplished initially under various conditions such as
K2CO3/DMF, pyridine/CH2Cl2, concd sulphuric acid/CH2Cl2, and
others, but the resulting yields were poor, due to the intramolecu-
lar hydrogen bond between carbonyl group of C4 and adjacent hy-
droxyl of group of C5 of flavonoid.12 Subsequently, the benzyl
protection groups in 12a–i were removed by transfer hydrogenol-
ysis using palladium hydroxide (on carbon, containing 20% pd) in
EtOH–THF at rt, thereby yielding the target compounds 1a–i. Sim-
ilarly, compound 9 was etherified by treatment of substituted hal-
ogenated hydrocarbon with K2CO3, affording to produce 13a–k.
The 5-alkylluteolin derivatives 2a–k were obtained by debenzyla-
tion of 13a–k under the same conditions.
By Scheme 4, the 40-alkylluteolin derivatives 6a,b were synthe-
sized. Protection of the 5- and 7-hydroxyl groups of compound 10
with benzyl bromide and K2CO3 in DMF produced 17, in excellent
yield. Selective removal of the 5-benzyl group and the dibenzal
group from 17 by means of the acetic acid and water mixture
(4:1) at reflux afforded 19 in 96.8% yield, in which the 40-hydroxyl
group was displaced using 1 equiv corresponding halogenated
hydrocarbon and K2CO3 in DMF. Finally, compounds 6a,b were pre-
pared by hydrogenolysis with palladium hydroxide. Also, both the
30- and 40-hydroxyl groups in 19 were displaced using 2 equiv
C2H5Br and K2CO3 in DMF, yielding compound 21. Finally, the
30,40-diethylluteolin derivative 5b was produced in 71% yield by
hydrogenolysis of 21 on palladium hydroxide (Scheme 5).
The syntheses of the 7-etherluteolin derivatives 3a–e and the
7-acylluteolin derivatives 4a–c are shown in Scheme 2. Luteolin
8 was heated with dichlorodiphenylmethane at 180 °C for 20 min
to produce compound 10. Displacement of the 7-hydrogen atom
OH
3'
OH
4'
5'
2'
1
8
HO
O
7
1'
2
3
6'
6
4
5
OH
O
luteolin
(8)
OBn
OH
OBn
HO
OH
BnO
c
O
O
O
O
e
OBn
R
O
O
R
O
OBn
12a-i
1a-i
O
BnO
O
12a, 1a R=CH3; 12b, 1b R=C2H5; 12c, 1c R=C3H7
12d, 1d R=i-C3H7; 12e, 1e R=C4H9; 12f, 1f R=i-C5H11
12g, 1g R=C7H15; 12h, 1h R=Ph; 12i, 1i R=p-Me-Ph
a
OH
OH
O
OBn
OBn
OH
luteolin
9
Ph
O
8
d
e
HO
O
BnO
O
Ph
O
OR
O
HO
O
OR
O
b
2a-k
13a-k
13a, 2a R=CH3; 13b, 2b R=C2H5; 13c, 2c R=C3H7; 13d, 2d R=i-C3H7;
13e, 2e R=C4H9; 13f, 2f R=i-C4H9; 13g, 2g R=i-C5H11; 13h, 2h R=C6H13; 13i, 2i R=C8H17
13j, 2j R=C10H21; 13k, 2k R=Ph-C4H9
OH
O
;
10
Scheme 1. Reagents and conditions: (a) BnBr/K2CO3/DMF; (b) Ph2CCl2, 180 °C; (c) RCOCl/NaH/CH2Cl2 or RCOOH/DMAP/DCC/CH2Cl2, rt; (d) R0X/K2CO3/DMF, rt–70 °C, X = I or
Br; (e) H2/20% Pd(OH)2/C/THF/EtOH.

7844
J. Zhang et al. / Bioorg. Med. Chem. 18 (2010) 7842–7848
Ph
Ph
O
OH
O
OH
RO
a
O
RO
O
c
OH
O
OH
O
3a-e
14a, 3a R=C2H5; 14b, 3b R=i-C3H7; 14c, 3c R=C4H9;
14d, 3d R=i-C4H9; 14e, 3e R=i-C5H11
Ph
14a-e
10
Ph
O
OH
OH
O
b
d
R
O
O
R
O
O
O
O
OH
O
OH
O
15a-c
4a-c
15a, 4a R=C2H5; 15b, 4b R=C3H7; 15c, 4c R=i-C3H7
Scheme 2. Reagents and conditions: (a) RX/K2CO3/DMF, 70 °C, X = I or Br; (b) R0COCl/KOH or K2CO3/DMF, rt; (c) AcOH/H2O (4:1), reflux; (d) H2/20% Pd(OH)2/C/THF/EtOH.
Ph
O
Ph
Ph
a
Ph
OH
O
O
O
OH
HO
O
MeO
O
MeO
O
b
OH
O
OMe O
OMe O
10
5a
16
Scheme 3. Reagents and conditions: (a) MeI/K2CO3/DMF, rt; (b) AcOH/H2O (4:1), reflux.
Ph
Ph
O
Ph
a
Ph
b
O
O
OH
O
OH
BnO
OH
O
HO
O
BnO
O
OBn O
OH
O
OH
O
OH
10
19
17
OR
OR
HO
O
BnO
O
c
d
OH
O
OH
O
6a R=C2H5
6b R=i-C5H11
6a-b
20
Scheme 4. Reagents and conditions: (a) BnBr/K2CO3/DMF; (b) AcOH/H2O (4:1), reflux; (c) 1 equiv RX/K2CO3/DMF; (d) H2/20% Pd(OH)2/C/THF/EtOH X = I or Br.
OC2H5
OC2H5
OH
OC2H5
OC2H5
OH
BnO
O
BnO
O
HO
O
b
a
OH
O
OH
O
OH
O
5b
19
21
Scheme 5. Reagents and conditions: (a) 2 equiv C2H5Br/K2CO3/DMF; (b) H2/20% Pd(OH)2/C/THF/EtOH.
Reaction of luteolin 8 with 2 equivalent of benzyl bromide
afforded the main product 11 (Scheme 6), in which the 7- and
40-hydroxyl groups were protected by the benzyl group. Displace-
ment of the 30-hydrogen atom in 11 by halogenated hydrocarbon

J. Zhang et al. / Bioorg. Med. Chem. 18 (2010) 7842–7848
OH
7845
OR
OH
OBn
OBn
OH
BnO
O
BnO
O
HO
O
a
b
OH
O
OH
O
OH
O
18a-b
8
11
OR
OH
c
HO
O
OH
O
18a, 7a R=C2H5; 18b, 7b R=i-C5H11
7a-b
Scheme 6. Reagents and conditions: (a) 2 equiv BnBr/K2CO3/DMF; (b) RX/K2CO3/DMF; (c) H2/20% Pd(OH)2/C/THF/EtOH X = I or Br.
and K2CO3 resulted in compounds 18a,b. The target-compound 30-
alkylluteolin derivatives 7a,b were produced in good yield by
hydrogenolysis on palladium hydroxide.
DAT agonistic potency than luteolin 8. 5-Pentanoylluteolin deriva-
tive 1e, as compared with the latter, likewise revealed a higher le-
vel of DAT agonistic activity (EC50 = 0.869 lM). 5-Butyrylluteolin
derivative 1c and 5-iso hexanoylluteolin derivative 1f, meanwhile,
showed an agonistic potency approximately equal to that of luteo-
lin 8. The DAT agonistic activity decreased as a result of 5-acyl sub-
stitution for the acetyl group, the propionyl group, the benzoyl
group, and the 4-methylbenzoyl group in 1a, 1b, 1g, 1h, and 1i,
3. Results and discussion
All of the synthesized luteolin derivatives and the three inter-
mediates (10, 11, and 19), in comparison with luteolin
8
the EC50 values falling in the 5.368 ꢀ 30.978
lM range. This fact
(EC50 = 1.45 0.29 M), were evaluated in vitro for DAT agonistic
l
suggests that the various 5-acyl substituents of luteolin 8 are
essential to DAT agonistic activity and that hydrocarbon substitu-
ent (in possession of 4–6 carbons) is integral to that activity. How-
ever, the EC50 results for 5-alkylluteolin derivatives 2a–k indicated
a lesser DAT agonistic potency than that of luteolin 8 regardless of
the 5-alkyl substituent. This suggests that substitution of an acyl
group for the 5-hydrogen atom in luteolin 8 is more effective than
substitution of an alkyl group.
activities (expressed in EC50 values). First, 5-acylluteolin deriva-
tives 1a–i and 5-alkylluteolin derivatives 2a–k were synthesized
and evaluated for those activities by means of constructed CHO cell
lines. Table 1 lists the results obtained. 5-isobutyrylluteolin deriv-
ative 1d (EC50 = 0.046 lM) was found to be the most potent DAT
agonist among the luteolin derivatives, exhibiting a 32-fold-higher
The discovery of 7-alkylluteolin derivatives 3a–e and 7-acyllute-
olin derivatives 4a–c led us to explore C-7 modification on the lute-
olin ring, as a means of further improving DAT agonistic potency
(Table 2). All of the synthesized 7-alkylluteolin derivatives 3a–e
and the intermediate 19 were inactive. The DAT agonistic activities
of 7-acylluteolin derivatives 4a, 4b, and 4c were slightly reduced
or equipotent compared with luteolin 8. This suggests, further, that
the C-5 or C-7 ester derivatives of luteolin are more favorable than
the C-5 or C-7 ether derivatives of same.
Table 1
In vitro DAT agonistic activities of 1a–i and 2a–k
OH
OH
OH
OH
HO
R
O
HO
O
O
O
OR
O
1a-i
Table 2
2a-k
O
In vitro DAT agonistic activities of 3a–e and 4a–c
Compound
R
EC50 (lM)
OH
1a
1b
1c
1d
1e
1f
1g
1h
1i
2a
2b
2c
2d
2e
2f
2g
2h
2i
CH3
C2H5
C3H7
i-C3H7
C4H9
i-C5H11
C7H15
Ph
p-Me–Ph
CH3
C2H5
C3H7
i-C3H7
C4H9
5.368
30.978
1.820
0.046
0.869
2.706
8.557
11.174
6.920
4.345
2.213
3.072
5.430
OH
OH
OH
R
O
O
O
RO
O
O
OH
OH
O
3a-e
4a-c
Compound
R
EC50 (lM)
3a
3b
3c
3d
3e
19
4a
4b
4c
8
C2H5
i-C3H7
C4H9
i-C4H9
i-C5H11
Ph–CH2
C2H5
—
—
—
—
—
—
1.696
1.694
1.375
2.40192
4.798
3.428
i-C4H9
i-C5H11
C6H13
C8H17
4.575
16.521
33.002
2.594
2j
2k
8
C
10H21
C3H7
i-C3H7
Ph–C4H8
1.45 0.29
1.45 0.29

7846
J. Zhang et al. / Bioorg. Med. Chem. 18 (2010) 7842–7848
5.1. 7-(Benzyloxy)-2-(30,40-bis(benzyloxy)phenyl)-5-hydroxy-
4H-chromen-4-one 9
Table 3
In vitro DAT agonistic activities of 5a, 5b, 6a,b, 7a,b and 10, 11
OH
OH
OC2H5
OC2H5
A mixture of luteolin 8 (0.1 g, 0.35 mmol), benzyl bromide
(0.125 mL, 1.05 mmol), and anhydrous K2CO3 (0.145 g, 1.05 mmol)
in DMF (10 mL) was stirred at 0 °C to rt overnight. The reaction
mixture was diluted with EtOAc and washed with water. The or-
ganic layer was separated, dried over anhydrous MgSO4, and con-
centrated in vacuo. The residue was purified by silica gel
chromatography (2:1 petroleum/ether to 1:1 petroleum/CH2Cl2)
to give stramineous solid product 9 (0.109 g, 56%). 1H NMR
(300 MHz, CDCl3): d 5.084 (s, 2H), 5.202 (s, 4H), 6.391–6.399 (d,
1H, J = 2.4 Hz), 6.450 (s, 1H), 6.475–6.481 (d, 1H, J = 1.8 Hz),
6.949–6.978 (d, 1H, J = 8.7 Hz), 7.312–7.485 (m, 17H), 12.787 (s,
1H); MS (ESI, m/z): 557.5 [M+H+], 579.6 [M+Na+].
MeO
O
HO
O
OMe O
OH
O
5b
5a
OH
OR
OH
OR
HO
O
HO
O
5.2. 2-(2,2-Diphenylbenzo[d][1,3]dioxol-5-yl)-5,7-dihydroxy-
4H-chromen-4-one 10
OH
O
7a-b
OH
O
6a-b
A
mixture
of
luteolin
8
(2 g,
6.99 mmol)
and
Compound
R
EC50
(lM)
dichlorodiphenylmethane (2 mL,10.42 mmol) was intimately
mixed then heated at 180 °C for 20 min. till the white gas did not
emit. The crude resulting products was diluted with hot acetone
then the insoluble substance was strained off. The filtrate obtained
was concentrated then purified by flash column chromatography
using petroleum ether/EtOAc (6:1 to 1:1) as eluent, vacuum dehy-
dration to give yellow solid product 10: 1.248 g, 39.6% yield. 1H
NMR (300 MHz, CDCl3): d 6.177–6.184 (d, 1H, J = 2.1 Hz), 6.499–
6.506 (d, 1H, J = 2.1 Hz), 6.877 (s, 1H), 7.198–7.226 (d, 1H,
J = 8.4 Hz), 7.438–7.539 (m, 10H), 7.679–7.707 (d, 1H, J = 8.4 Hz),
7.772 (s, 1H), 10.884 (s, 1H), 12.856 (s, 1H); MS (ESI, m/z): 449.1
[MꢀHꢀ].
5a
5b
6a
6b
7a
7b
10
11
8
—
—
C2H5
i-C5H11
C2H5
i-C5H11
3.417
—
—
—
12.856
—
—
—
1.45 0.29
Comparing the 5,7-dimethylluteolin derivative 5a, the 30,40-
diehtylluteolin derivative 5b, the 40-alkylluteolin derivatives 6a,b,
the 30-alkylluteolin derivatives 7a,b and the intermediates 10 and
11 as shown in Table 3, 5a showed reduced DAT agonistic activity.
The fact that the 30-, or the 40-, or the 30,40-substituted derivatives
of luteolin 8 showed lesser activity or inactivity implies that the
free hydroxyl at 30- and 40- is essential to DAT agonistic functional-
ity. It is possible that introduction of a substituent at the 30- or 40-
position on the luteolin ring prevents combination with the DAT,
thereby reducing agonistic potency.
5.3. 7-(Benzyloxy)-2-(3,4-bis(benzyloxy)phenyl)-4-oxo-4H-
chromen-5-yl acetate 12a
A solution of 9 (300 mg, 0.54 mmol) in DMF (10 mL), 60% NaH
(44 mg, 1.1 mmol) was added under argon, stirred for 30 min.
Acetyl chloride (77 lL, 1.08 mmol) was added. After stirring at rt
for 2 h, the resulting mixture was diluted with EtOAc, and then
according to the general disposal procedure, crude products was
purified by flash column chromatography using petroleum ether/
EtOAc (6:1 to 1:1) as eluent to afford stramineous solid product
12a: 320 mg, 99% yield. 1H NMR (300 MHz, CDCl3): d 2.430 (s,
3H), 5.142 (s, 2H), 5.233 (s, 4H), 6.433 (s, 1H), 6.669–6.677 (d,
1H, J = 2.4 Hz), 6.880–6.888 (d, 1H, J = 2.4 Hz), 6.974–7.002 (d,
1H, J = 8.4 Hz), 7.323–7.487 (m, 17H); MS (MALDI, m/z): 599.2
[M+H+], 621.2 [M+Na+]. Compounds 12b–i was prepared as de-
scribed for compound 12a (Supplementary data).
4. Conclusions
It was found that the optimal DAT agonistic structure features of
luteolin 8 are: (1) the number and type of acyl substituents at C-5 or
C-7, hydrocarbon substituent (in possession of 4–6 carbons) being
crucial and (2) the free hydroxyl at 30- and 40-. These findings led
to the discovery of 5-isobutyrylluteolin derivative 1d as a potent
DAT agonist. Compound 1d offers a 32-fold increase in potency over
that of the parent core 8. Further, in vivo studies on compound 1d are
ongoing.
5.4. 2-(3,4-Dihydroxyphenyl)-7-hydroxy-4-oxo-4H-chromen-
5-yl acetate 1a
5. Experimental
A suspension of 12a (598 mg, 0.535 mmol) in EtOH (15 mL) was
treated with 20% palladium hydroxide (32 mg) under a flow of
hydrogen for 7 h at rt. The reaction mixture was then filtered on
Celite and eluted with EtOH. After concentration of the filtrate under
vacuum, EtOAc was added to collect product then hexane was added
to scorify solid. Solid was filtered, washed with hexane and vacuum
drying to give flavovirens solid product 1a: 150 mg, 85.4% yield. 1H
NMR (300 MHz, CDCl3): d 2.285 (s, 3H), 6.462 (s, 1H), 6.530–6.538
(d, 1H, J = 2.4 Hz), 6.860–6.868 (d, 1H, J = 2.4 Hz), 6.900 (s, 1H),
7.355 (s, 1H), 7.377 (s, 1H); MS (ESI, m/z): 327.0 [MꢀHꢀ], 284.9
[MꢀCH3COꢀ]; FT-IR: mmax 3375 (br, OH), 2924, 2854, 1744, 1658,
1615, 1494, 1450, 1367, 1257, 1166, 946, 830 cmꢀ1; HRMS (MALDI)
Materials were obtained from commercial suppliers. 1H NMR
spectra were obtained on NMR spectrometer with superconductor
magnet (MERCURY 300). The chemical shifts are given in d values
(ppm) using tetramethylsilane as the internal standard. ESI-MS
were determined on LCMS-2010EV spectrometer. MALDI-MS were
determined on Ion Spec HiResMALDI spectrometer. IR was re-
corded on FT-185 spectrometer. HRMS were determined on Ion
Spec 4.7 Tesla FTMS. Reactions were followed by TLC on Silica
gel (HSGF 254). Chromatographic separations were carried out on
silica gel (300–400 mesh) using the indicated eluents. Yields are
unoptimized. Chemical intermediates were characterized by 1H
NMR.
m
/z calcd for C17H13O7 [M+H+]: 329.0650, found 329.06558. Com-

J. Zhang et al. / Bioorg. Med. Chem. 18 (2010) 7842–7848
7847
pounds 1b–i was prepared as described for compound 1a (Supple-
mentary data).
315.0858, found 315.08632. Compounds 3b–e was prepared as de-
scribed for compound 3a (Supplementary data).
5.5. 7-(Benzyloxy)-2-(3,4-bis(benzyloxy)phenyl)-5-ethoxy-4H-
chromen-4-one 13b
5.9. 2-(2,2-Diphenylbenzo[d][1,3]dioxol-5-yl)-5-hydroxy-4-oxo-
4H-chromen-7-yl propionate 15a
A solution of 9 (300 mg, 0.54 mmol) in DMF (10 mL), anhydrous
Compound 10 (300 mg, 0.67 mmol) in DMF (15 mL), anhydrous
potassium carbonate (149 mg, 1.08 mmol), and iodoethane (87
lL,
potassium carbonate (185 mg, 0.84 mmol) was added under argon,
1.08 mmol) were added under argon. After stirring at 75 °C for
12 h, the resulting mixture was diluted with EtOAc, and then
according to the general disposal procedure, crude products was
purified by flash column chromatography using petroleum ether/
EtOAc (6:1 to 3:1) as eluent to afford stramineous solid product
13b: 311 mg, 98.7% yield. 1H NMR (300 MHz, CDCl3): d 1.508–
1.554 (t, 3H, J = 6.9 Hz), 4.084–4.155 (q, 2H, J = 6.9 Hz), 5.125 (s,
2H), 5.220 (s, 4H), 6.413–6.421 (d, 1H, J = 2.4 Hz), 6.492 (s, 1H),
6.559–6.567 (d, 1H, J = 2.4 Hz), 6.967–6.995 (d, 1H, J = 8.4 Hz),
7.315–7.502 (m, 17H); MS (MALDI, m/z): 585.4 [M+H+], 607.4
[M+Na+]. Compounds 13a and 13c–k were prepared as described
for compound 13b (Supplementary data).
stirred for 30 min. Propionyl chloride (57 lL, 0.67 mmol) was
added. After vigorous stirring at rt for 24 h, the resulting mixture
was diluted with dichloromethane, and then according to the gen-
eral disposal procedure, crude products was purified by flash col-
umn chromatography using dichloromethane as eluent to afford
yellow solid product 15a: 251 mg, 74.4% yield. 1H NMR
(300 MHz, CDCl3): d 1.258–1.309 (t, 3H, J = 7.5 Hz), 2.586–2.661
(q, 2H, J = 7.5 Hz), 6.549–6.556 (d, 1H, J = 2.1 Hz), 6.584 (s, 1H),
6.806–6.813 (d, 1H, J = 2.1 Hz), 6.979–7.007 (d, 1H, J = 8.4 Hz),
7.380–7.480 (m, 8H), 7.578–7.610 (m, 4H), 12.788 (s, 1H). Com-
pounds 15b,c was prepared as described for compound 15a (Sup-
plementary data).
5.6. 2-(3,4-Dihydroxyphenyl)-5-ethoxy-7-hydroxyl-4H-chro
5.10. 2-(3,4-Dihydroxyphenyl)-5-hydroxy-4-oxo-4H-chromen-
men-4-one 2b
7-yl propionate 4a
From compound 13b (100 mg, 0.17 mmol) as described for 1a,
flavovirens solid product 2b was obtained: 30 mg, 57% yield. 1H
NMR (300 MHz, CDCl3): d 1.314–1.360 (t, 3H, J = 6.9 Hz), 3.976–
4.046 (q, 2H, J = 6.9 Hz), 6.327 (s, 1H), 6.352 (s, 1H), 6.455 (s, 1H),
6.830–6.858 (d, 1H, J = 8.4 Hz), 7.290–7.296 (d, 2H, J = 1.8 Hz);
MS (ESI, m/z): 313.1 [MꢀHꢀ]; FT-IR: mmax 3472 (br, OH), 2950,
1604, 1520, 1465, 1374, 1277, 1114, 1025, 825, 786 cmꢀ1; HRMS
(MALDI) m/z calcd for
315.08632. Compounds 2a and 2c–k were prepared as described
for compound 2b (Supplementary data).
From compound 15a (185 mg) as described for 1a, flavovirens
solid product 4a was obtained: 86 mg, 69% yield. 1H NMR
(300 MHz, CDCl3): d 1.128–1.176 (t, 3H, J = 7.2 Hz), 2.609–2.683
(q, 2H, J = 7.5 Hz), 6.636–6.642 (d, 1H, J = 1.8 Hz), 6.852 (s, 1H),
6.900–6.928 (d, 1H, J = 8.4 Hz), 7.033–7.039 (d, 1H, J = 1.8 Hz),
7.456 (s, 1H), 7.464–7.492 (d, 1H, J = 8.4 Hz), 13.057 (s, 1H); MS
(ESI, m/z): 341.1 [MꢀHꢀ]; FT-IR: mmax 3400 (br, OH), 2984, 1767,
1656, 1567, 1455, 1335, 1218, 1137, 1074, 944, 878, 740, 639 cm
ꢀ1; HRMS (MALDI) m/z calcd for C18H15O7 [M+H+]: 343.0815, found
343.08123. Compounds 4b,c was prepared as described for com-
pound 4a (Supplementary data).
C
17H15O6 [M+H+]: 315.0864, found
5.7. 2-(2,2-Diphenylbenzo[d][1,3]dioxol-5-yl)-7-ethoxy-5-hydr
oxy-4H-chromen-4-one 14a
5.11. 2-(3,4-Dihydroxyphenyl)-5,7-dimethoxy-4H-chromen-4-
one 5a
From compound 10 (300 mg, 0.67 mmol) and iodoethane
(54
l
L, 0.67 mmol) as described for 13b to obtain yellow solid
From compound 10 (300 mg, 0.67 mmol) and iodomethane
product 14a: 219 mg, 69% yield. 1H NMR (300 MHz, CDCl3): d
1.425–1.472 (t, 3H, J = 6.9 Hz), 4.060–4.130 (q, 2H, J = 6.9 Hz),
6.339–6.346 (d, 1H, J = 2.1 Hz), 6.437–6.444 (d, 1H, J = 2.1 Hz),
6.519 (s, 1H), 6.975–7.003 (d, 1H, J = 8.4 Hz), 7.389–7.469 (m,
8H), 7.750–7.600 (m, 4H), 12.754 (s, 1H); MS (ESI, m/z): 479.1
[M+H+], 501.2 [M+Na+]. Compounds 14b–e was prepared as de-
scribed for compound 14a (Supplementary data).
(167 lL, 2.68 mmol) as described for 13b to obtain white solid
product 16: 280 mg, 88% yield. Then, from compound 16
(280 mg, 0.59 mmol) as described for 3a, gray solid product 5a
was obtained: 45 mg, 25% yield. 1H NMR (300 MHz, CDCl3): d
3.798 (s, 3H), 3.872 (s, 3H), 6.443 (s, 1H), 6.466–6.473 (d, 1H,
J = 2.1 Hz), 6.750–6.757 (d, 2H, J = 2.1 Hz), 6.835–6.864 (d, 1H,
J = 8.7 Hz), 7.328 (s, 1H), 7.350 (s, 1H); MS (ESI, m/z): 313.1
[MꢀHꢀ]; FT-IR: mmax 3460 (br, OH), 2945, 1640, 1560, 1399,
1276, 1163, 1057, 957, 826, 741, 670 cmꢀ1; HRMS (MALDI) m/z
calcd for C17H15O6 [M+H+]: 315.0863, found 315.08632.
5.8. 2-(3,4-Dihydroxyphenyl)-7-ethoxy-5-hydroxy-4H-chro
men-4-one 3a
Compound 14a (219 mg, 0.458 mmol) was added to a mixture
of acetic acid/water (4:1, 50 mL) and refluxed for 9 h. Then, EtOAc
(100 mL) and water (100 mL) were added. The organic layer was
washed with NaHCO3 saturated aqueous solution (40 mL ꢁ 3)
and dried over anhydrous Na2SO4. After concentration, the residue
was added with copious dichloromethane and petroleum ether. So-
lid scorified was filtered, washed with petroleum ether, and vac-
uum drying to give yellow solid product 3a: 80 mg, 56% yield. 1H
NMR (300 MHz, CDCl3): d 1.335–1.381 (t, 3H, J = 6.9 Hz), 4.120–
4.190 (q, 2H, J = 6.9 Hz), 6.345–6.352 (d, 1H, J = 2.1 Hz), 6.703–
6.710 (d, 1H, J = 2.1 Hz), 6.728 (s, 1H), 6.886–6.913 (d, 1H,
J = 8.1 Hz), 7.434–7.461 (d, 1H, J = 8.1 Hz), 7.467 (s, 1H), 12.986
(s, 1H); MS (ESI, m/z): 313.0 [MꢀHꢀ]; FT-IR: mmax 3415 (br, OH),
2750, 1656, 1500, 1419, 1336, 1245, 1125, 1032, 859, 763,
5.12. 2-(4-Ethoxy-3-hydroxyphenyl)-5,7-dihydroxy-4H-chro
men-4-one 6a
From compound 10 (2.26 g, 5 mmol) and benzyl bromide
(1.5 mL, 12.5 mmol) as described for 15a to afford off-white solid
product 17: 2.304 g, 73% yield. Then, compound 17 (838 mg,
1.33 mmol) was added to a mixture of acetic acid/water (4:1,
50 mL) and as described for 3a to obtain yellow solid product 19:
484 mg, 96.8% yield. From compound 19 (377 mg, 1 mmol) and
iodoethane (80 lL, 1 mmol) as described for 13b to obtain yellow
solid product 20a: 305 mg, 75.3% yield. Finally, from compound
20a (293 mg) as described for 1a, flavovirens solid product 6a
was obtained: 174 mg, 76.4% yield. 1H NMR (300 MHz, CDCl3): d
1.290–1.334 (t, 3H, J = 6.6 Hz), 4.031–4.098 (q, 2H, J = 6.6 Hz),
6.141 (s, 1H), 6.405 (s, 1H), 6.681 (s, 1H), 6.989–7.017 (d, 1H,
;
686 cmꢀ1 HRMS (MALDI) m/z calcd for C17H15O6 [M+H+]:

7848
J. Zhang et al. / Bioorg. Med. Chem. 18 (2010) 7842–7848
J = 8.4 Hz), 7.379 (s, 1H), 7.443–7.471 (d, 1H, J = 8.4 Hz), 12.885 (s,
4.091 (q, 2H, J = 6.6 Hz), 6.133–6.139 (d, 1H, J = 1.8 Hz), 6.443–
6.449 (d, 1H, J = 1.8 Hz), 6.856 (s, 1H), 6.886–6.913 (d, 1H,
J = 8.1 Hz), 7.490 (s, 1H), 7.515 (s, 1H), 12.932 (s, 1H); MS (ESI,
m/z): 355.1 [MꢀHꢀ]; FT-IR: mmax 3250 (br, OH), 2957, 1647, 1561,
1434, 1360, 1255, 1117, 1029, 948, 831, 724, 640 cmꢀ1; HRMS
1H); MS (ESI, m/z): 313.1 [MꢀHꢀ]; FT-IR:
mmax 3546 (br, OH), 2990,
1654, 1586, 1431, 1363, 1263, 1172, 1031, 921, 846, 799, 643 cmꢀ1
;
HRMS (MALDI) m/z calcd for C17H15O6 [M+H+]: 315.0869, found
315.08632. Compounds 6b was prepared as described for com-
pound 6a (Supplementary data).
(MALDI) m/z calcd for
C
20H21O6 [M+H+]: 357.1333, found
357.13327. Compounds 7a was prepared as described for com-
pound 7b (Supplementary data).
5.13. 2-(3,4-Diethoxyphenyl)-5,7-dihydroxy-4H-chromen-4-one
5b
Acknowledgments
From compound 19 (377 mg, 1 mmol) and iodoethane (160 lL,
2 mmol) as described for 13b to obtain yellow solid product 21:
351 mg, 81% yield. Then, from compound 21 (342 mg) as described
for 1a, flavovirens solid product 5b (167 mg) was obtained. By flash
column chromatography using petroleum ether/EtOAc (6:1) as elu-
ent, another 5b (24 mg) was afforded from the filtrate residue. The
total 5b was afforded: 191 mg, 71% yield. 1H NMR (300 MHz,
CDCl3): d 1.285–1.332 (t, 6H, J = 7.2 Hz), 4.030–4.131 (m, 4H),
6.145–6.151 (d, 1H, J = 1.8 Hz), 6.457–6.463 (d, 1H, J = 1.8 Hz),
6.877 (s, 1H), 7.028–7.057 (d, 1H, J = 8.7 Hz), 7.483–7.489 (d, 1H,
J = 1.8 Hz), 7.561–7.596 (dd, 1H, J = 1.8 Hz, J = 8.4 Hz), 12.885 (s,
1H); MS (ESI, m/z): 341.2 [MꢀHꢀ]; FT-IR: mmax 3100 (br, OH),
2621, 1651, 1525, 1434, 1371, 1265, 1253, 1170, 1045, 1033,
905, 828, 752, 611 cmꢀ1; HRMS (MALDI) m/z calcd for C19H19O6
[M+H+]: 343.1183, found 343.11762.
We gratefully acknowledge the help of analysis centre in Shang-
hai Institute of Organic Chemistry, Chinese Academy of Sciences,
with spectral data.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmc.2010.09.049.
References and notes
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5.14. 5,7-Dihydroxy-2-(4-hydroxy-3-(isopentyloxy) phenyl)-4H-
chromen-4-one 7b
Luteolin 8 (2.87 g, 10 mmol) and benzyl bromide (2.4 mL,
20 mmol) was as described for 13b to obtain flavovirens solid
product 11 (1.913 g, 41% yield). Then, from compound 11
(268 mg, 0.575 mmol) and 1-bromo-3-methylbutane (69 lL,
0.575 mmol) as described for 13b to afford off-white solid product
18b: 121 mg, 39% yield. Finally, from compound 18b (108 mg) as
described for 1a, flavovirens solid product 7b was obtained:
70 mg, 97.6% yield. 1H NMR (300 MHz, CDCl3): d 0.906 (s, 3H),
0.928 (s, 3H), 1.582–1.649 (m, 2H), 1.729–1.859 (m, 2H), 4.084–
11. Zhao, G.; Qin, G. W.; Wang, J.; Chu, W. J.; Guo, L. H. Neurochem. Int. 2010, 56,
168.
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