Synthesis of 1-(3,4-dihydroxy-5-nitrophenyl)-2-phenyl-ethanone and derivatives as potent and long-acting peripheral inhibitors of catechol-O-methyltransferase

Article abstract of DOI:10.1021/jm0109964

A homologous series of novel nitro-catechol structures (7a-7e) were synthesized and tested as inhibitors of the enzyme catechol-O-methyltransferase (COMT). Increasing chain length was found to have significant impact on both brain penetration and duration

Full text of DOI:10.1021/jm0109964

J . Med. Chem. 2002, 45, 685-695
685
Syn th esis of 1-(3,4-Dih yd r oxy-5-n itr op h en yl)-2-p h en yl-eth a n on e a n d Der iva tives
a s P oten t a n d Lon g-Actin g P er ip h er a l In h ibitor s of
Ca tech ol-O-m eth yltr a n sfer a se
David A. Learmonth,† Maria A. Vieira-Coelho,§ J an Benes,†, Paula C. Alves,† Nuno Borges,§,#
Ana P. Freitas,† and Patr´ıcio Soares-da-Silva*,§
Department of Research & Development, BIAL, 4745-457 S. Mamede do Coronado, Portugal
Received J uly 19, 2001
A homologous series of novel nitro-catechol structures (7a -7e) were synthesized and tested
as inhibitors of the enzyme catechol-O-methyltransferase (COMT). Increasing chain length
was found to have significant impact on both brain penetration and duration of COMT inhibition
in the rat. Of this series, compound 7b (1-(3,4-dihydroxy-5-nitrophenyl)-2-phenyl-ethanone)
was found to exhibit the most potent and selective inhibition of peripheral COMT, with an
inhibition profile more similar to entacapone 2 than tolcapone 1 (an equipotent peripheral
and central inhibitor) but with much improved duration of action (7b, 70% inhibition and 2,
25% inhibition at 9 h after administration). The effects of structural modifications to 7b on
COMT inhibitory profile were investigated, and it is concluded that the carbonyl group and
preferably unsubstituted aromatic ring are essential features to maintain prolonged peripheral
COMT inhibition. The introduction of the R-methylene group, the major structural difference
between 7b and 1, would appear responsible for the observed enhancement in selectivity of
peripheral COMT inhibition of 7b, which has more limited access to the brain than 1.
In tr od u ction
breakdown of L-Dopa in the periphery. Enzymatic de-
carboxylation of L-Dopa successfully reaching the brain
(AADC) permits an ‘artificial’ increase of dopamine
levels. The rationale for the use of COMT inhibitors is
based on their capacity to inhibit the O-methylation of
L-Dopa to 3-O-methyl-L-Dopa (3-OMD), the major meta-
bolic deactivation pathway of L-Dopa in the periphery
when administered with an AADC inhibitor.14-16 3-OMD,
which offers no therapeutic effect and a long elimination
half-life compared to L-Dopa, accumulates in plasma
and tissues and competes with L-Dopa for transport
across the BBB into the brain. In fact, a close relation-
ship between accumulation of 3-OMD and the ‘end-of-
dose’ or ‘wearing-off’ syndrome has been described.17 In
principle therefore, COMT inhibition should improve
L-Dopa/AADC inhibitor therapy namely by reducing
metabolic formation of 3-OMDsincreasing the bioavail-
ability of L-Dopa to enter the brain would extend the
duration of antiparkinsonian action and permit dosage
lowering and/or increasing the time interval between
doses.
The so-called ‘first-generation’ inhibitors3,18 such as
pyrogallol, tropolone, and gallic acid, which besides
being toxic and lacking potency with inhibition con-
stants (Ki) in the micromolar range, are themselves
competitive substrates for COMT. It was subsequently
discovered that incorporation of the strongly electrone-
gative nitro group to catechol-containing molecules gave
rise to highly potent and tight-binding inhibitors of
COMT, which were in addition very poor substrates for
the enzyme.19-21 The electron-withdrawing nitro group
could be envisaged to both stabilize the ionized cat-
echol-COMT complex and to reduce the nucleophilicity
of the hydroxyl oxygen normally prone to undergo
methylation. Typical second-generation inhibitors con-
The enzyme-catalyzed O-methylation of catechol-
based neurotransmitters was reported as early as 19581
and attributed to catechol-O-methyltransferase (COMT),2
a magnesium-dependent enzyme found in both cerebral
tissues and the central nervous system (CNS). COMT
catalyzes the transfer of a methyl group from its cofactor
S-adenosyl-L-methionine (AdoMet) to one hydroxyl group
of a catecholic substrate via an SN2-type reaction, giving
rise to O-methylated products and S-adenosylhomocys-
teine (SAH). COMT is now known to play a key role in
the inactivation of endogenous catecholamines,3 catechol
estrogens,4 and the detoxification of several xenobiotic
catechols.5-7 Accordingly, medicinal chemists over the
last 20 years have been greatly interested in exploring
the design and clinical potential of inhibitors of the
COMT enzyme.8,9
Development of such inhibitors has been accelerated
mainly on the premise that inhibition of COMT may
provide therapeutic benefit to patients afflicted by
Parkinson’s disease (PD), a dopamine deficiency disor-
der resulting from the degeneration of striatal dopam-
inergic neurons. Orally administered L-Dopa (3-(3,4-
dihydroxyphenyl)-L-alanine), conceived as a dopamine
precursor able to cross the blood-brain barrier (BBB),
continues as standard therapy for PD,10,11 in conjunction
with a peripherally acting aromatic amino acid decar-
boxylase (AADC) inhibitor such as carbidopa or benser-
azide12,13 (also inaccessible to the brain) to prevent
* To whom correspondence should be addressed. Tel: 351-22-
9866100. Fax: 351-22-9866192. E-mail: psoares.silva@bial.com.
† Laboratory of Chemistry.
§ Laboratory of Pharmacology.
Present address: Dusni 2, 110 00 Prague, Czech Republic.
#
Present address: Faculdade de Cieˆncias da Nutric¸a˜o e Alimenta-
c¸a˜o, Universidade do Porto, 4200-465 Porto, Portugal.
10.1021/jm0109964 CCC: $22.00 © 2002 American Chemical Society
Published on Web 12/22/2001

686 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3
Learmonth et al.
Ta ble 1. Physical Constants for Homologous Nitro-catechols
7a -7e
F igu r e 1. Chemical structures of tolcapone (1) and entaca-
pone (2).
compd
n
mp (°C)
recryst. solvent
formula
anal.
7a
7b
7c
7d
7e
0
1
2
3
4
134-136 EtOH
178-179 EtOH
131-132 Et2O/PE
C
C
13H9NO5
14H11NO5 C, H, N
C, H, N
taining the 3-nitrocatechol motif such as tolcapone22
1
and entacapone23 2 (Figure 1) are very potent with
inhibition constants in the low nanomolar range and
were introduced into clinical practice as adjuncts to
L-Dopa therapy for PD. Due to liver toxicity concerns
however (several cases of fatal fulminant hepatitis were
reported24-26), 1 was recently withdrawn from the
market.
C15H13NO5 C, H, N
123-125 CH2Cl2/heptane C16H15NO5 C, H, N
109-111 CH2Cl2/heptane C17H17NO5 C, H, N
Sch em e 1. Synthesis of Homologous Nitro-catechol
Seriesa
The subject of selectivity of COMT inhibition remains
controversial, selectivity being defined in terms of the
predominance of peripheral over central COMT inhibi-
tion. Compound 1, a more potent inhibitor of peripheral
COMT, also penetrates into the brain to inhibit cerebral
COMT. Conversely, 2 is considered a purely peripheral
COMT inhibitor. This distinction is of key importance
- while COMT inhibitors penetrating the brain may
theoretically have the benefits of decreasing dopamine
methylation, indeed central inhibition may be unim-
portant if the more significant action is to protect
L-Dopa from breakdown in the periphery. Furthermore,
COMT inhibitors with limited access to the brain may
avoid undesired side-effects of these agents. It is inter-
esting to highlight both the lack of antiparkinsonian
action of tolcapone when administered alone,27 and the
relatively frequent observations of increased dopamin-
ergic stimulation expressed as dyskinesia and confusion
in patients taking both L-Dopa and tolcapone.28 Such
observations lead to the conclusion that COMT inhibi-
tors entering the brain have minimal beneficial effect
alone and, when administered together with L-Dopa,
may provoke serious symptoms requiring cessation of
therapy.
A further concern with established COMT inhibitors
concerns their relatively short half-life29,30 (1, 2 h and
2, 0.3 h) such that recommended doses of 2 are twice
that of 1 and in either case are administered up to thrice
daily. To date, the development of a potent, long-acting,
and selective inhibitor of peripheral COMT as an
adjunct to L-Dopa/AADC inhibitor therapy for the
treatment of PD remains an unfulfilled objective.
Our initial strategy therefore was to synthesize a
preliminary restricted series of homologous nitro-cat-
echol compounds in order to ascertain the effect of chain
length (increasing lipophilicity) on potency, duration,
and selectivity of COMT inhibition. One compound from
this series uniquely displayed potent, selective, and
long-acting inhibition of peripheral COMT. This lead
structure was modified, and the effects on COMT
inhibition in terms of peripheral selectivity and duration
of action were determined.
a
Reagents: (a) i. Ar(CH2)nMgX, ii. H3O+, (87-94%); (b) NaOt-
Bu, cyclohexanone, PhCH3, ∆, (87-94%); (c) 10% Pd/C, NH4+HCO2
,
-
MeOH, ∆, (84-94%); (d) 70% HNO3, AcOH, (67-77%); (e) AlCl3,
pyridine, EtOAc, ∆, (90-99%).
(3, R ) H) as the benzyl ether (3, R ) Bn; BnBr,
K2CO3, acetone, ∆, 96%) and subsequent reaction with
the appropriate preformed arylalkyl Grignard reagents
(Ar(CH2)nMgX, n ) 0-4) furnished the alcohols (4a -
4e, R ) Bn, n ) 0-4, 87-94%). Oppenauer oxidation
using sodium tert-butoxide as base and cyclohexanone
as hydrogen acceptor in warm toluene proved quicker
and more expedient than J ones oxidation under PTC
conditions (Na2Cr2O7, H2SO4, CH2Cl2, H2O, Bu4N+Br-)
both in terms of ease of product isolation and yields
(ketones 5a -5e, R ) Bn, 87-94%). Selective deprotec-
tion of the benzyl-protecting groups proceeded smoothly
under acidic conditions (excess 30% HBr in acetic acid,
CH2Cl2, room temperature, 2 h (75-87%)) or more
conveniently by catalytic hydrogen transfer using am-
monium formate as hydrogen donor and palladium
catalysis to provide the phenols (5a -5e, R ) H, 84-
92%), which underwent regioselective nitration in mod-
erate to good yields under mild conditions (70% HNO3,
AcOH) to 6a -6e (67-77%). Although methyl ether
cleavage proceeded under standard forcing conditions
(48% HBr, AcOH, ∆), these rather harsh conditions and
only moderate yields prompted us to develop an im-
proved method for the demethylation of nitro-catechol
methyl ethers using aluminum chloride and pyridine
in warm ethyl acetate,31 which furnished the target
compounds (7a -7e, Table 1) in excellent yields (90-
99%) and purity (>99%, HPLC).
Structural modifications considered for the ethanone
7b, identified from the preliminary series, are outlined
in Figure 2. The 3,4-dihydroxy-5-nitrophenyl group as
mentioned earlier is essential for high activity, so our
initial focus centered on the carbonyl group. Catalytic
Ch em istr y
The initial nitro-catechol homologues (7a -7e, Table
1) were prepared according to Scheme 1. Protection of
the hydroxyl group of commercially available vanillin

Synthesis of Catechol-O-methyltransferase Inhibitors
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3 687
Compound 7a presented an almost identical inhibitory
profile in brain and liver COMT (very similar to that of
1), whereas longer chained 7c-7e were noticeably more
potent inhibitors of liver rather than brain COMT after
only 3 h. Similarly at 6 and 9 h, compound 7b was
distinctly more potent as a peripheral COMT inhibitor,
and notably endowed with a particularly long duration
of action, such that 70% inhibition of liver COMT was
still attained even at 9 h. These results demonstrate
that increasing chain length has a definite effect on the
selectivity of COMT inhibition and imply that the
introduction of the R-methylene group, the major struc-
tural difference between 7b and 1, is most probably
responsible for the selectivity enhancement of peripheral
COMT inhibition observed for 7b.
F igu r e 2. Structural modifications to lead structure 7b.
hydrogenation of benzyl protected alcohol 4b (R ) Bn,
n ) 1) under acidic conditions allowed concomitant
removal of both benzyl ether and benzylic hydroxyl
groups, and subsequent nitration (100% HNO3/Et2O)
and demethylation step e outlined in Scheme 1 afforded
deoxy analogue 8. Direct oximation of 7b with hydroxy-
lamine hydrochloride gave 9 while standard procedures
afforded aza-derivatives 10-14 (Table 2) in generally
moderate yields.
Modification of the hitherto unsubstitued aryl ring
was achieved via Friedel-Crafts acylation of guaiacol
(2-methoxyphenol) with an appropriate arylacetic acid
in a zinc chloride-phosphorus oxychloride mixture32
(Scheme 2), which gave access to the intermediate
ketones of general structure 15 albeit in generally low
yields (25-38%). Only marginally better yields were
obtained with the same reagents using boron trifluoride
as both solvent and catalyst for the Friedel-Crafts
reaction.33 Subsequent nitration and demethylation
steps afforded the target compounds 16-23 (Table 3).
Introduction of strongly electronegative substituents
to this aryl ring was achieved by direct nitration of the
diacetate 24 derived from 7b (Ac2O, H2SO4, 77%) which
afforded a separable mixture of 4′- and 2′-nitro isomers
25 and 26 (ratio ∼ 1:1, 45% combined yield). Construc-
tion of the skeleton of the 2′-carboxyl derivative 27 was
achieved by lateral lithiation of o-toluic acid and reac-
tion with methyl vanillate.34 Exposure of 27 to warm
acid effected cyclization to 28 (both Scheme 3).
Finally, attention was turned to the free R-methylene
group of ethanone 7b, which was changed by the
introduction of alkyl substituents via either mono- or
dialkylation of the benzyl protected intermediate ke-
tone 5b (n ) 1) using sodium hydride and an alkyl
halide (Scheme 4). Subsequent elaboration afforded
the R-alkylated nitro-catechol derivatives, which were
more conveniently isolated and purified as their di-
acetates 29-32 (Table 4). Direct bromination of 7b
using phenyltrimethylammonium tribromide in THF
afforded bromo-derivative 33 while the R-phenyl ana-
logue 34 was conveniently obtained by reaction of
guaiacol with diphenylacetic acid under conditions
described in Scheme 2.
Figure 3 clearly highlights differences in inhibitory
profile between 7b and standards 1 and 2. As indicated
earlier, 1 produces almost equipotent inhibition of both
liver and brain COMT at 6 and 9 h after administration.
Although both 2 and 7b possess similar central COMT
inhibition profiles, 2 is characterized by markedly lower
peripheral COMT inhibitory activity at 9 h (only 25%)
compared to 7b.
In vitro COMT inhibition studies were then carried
out to evaluate and compare the potency of compounds
1, 2, and 7b. Incubation of liver and whole brain
homogenates in the presence of increasing concentra-
tions of adrenaline resulted in a concentration-depend-
ent formation of metanephrine, yielding Km (in µM) and
Vmax (in nmol mg protein-1 h-1) values of 0.7 (0.5, 0.9;
95% confidence intervals) and 1.31 ( 0.02 for brain and
238.5 (128.5; 348.5) and 61.6 ( 3.8 for liver, respectively.
From these kinetic parameters, a saturating concentra-
tion of adrenaline was chosen to use in inhibition studies
(liver, adrenaline ) 1000 µM; brain, adrenaline ) 100
µM). The protein content was similar in all samples
(approximately 5 mg/500 µL homogenate). Compounds
1, 2, and 7b produced a concentration-dependent de-
crease in the O-methylation of adrenaline with IC50
values in the low nanomolar range for the brain and in
the micromolar range for the liver (Table 6). Interest-
ingly, 7b displayed, along with 1, potent inhibition of
both cerebral and peripheral COMT (thereby implying
that 7b is a potent inhibitor of both forms of COMT),
whereas 2 was endowed with noticeably lower potency.
Confirmation of the reduced potency of 2 compared to
1 and 7b came from further in vitro testing (SK-N-SH
cell monolayers, Table 7).
The in vivo inhibitory potency of 1, 2, and 7b was
evaluated in experiments in which rats were given in-
creasing doses of the compounds (0.3 to 30 mg/kg). Ani-
mals were killed 1 h after administration, and COMT
activity was determined. The results (Figure 4) show
that 1 and 7b are essentially equipotent inhibitors of
peripheral COMT with ED50’s of 0.7 ( 1.1 and 0.7 (
0.1 mg/kg, respectively; 2 again was less potent with
an ED50 value of 1.9 ( 0.2 mg/kg. Significantly, however,
7b was less potent than 1 at inhibiting cerebral COMT
with ED50’s of 5.3 ( 1.1 and 1.6 ( 0.1 mg/kg, respec-
tively (2 failed to reach the 50% inhibition level). Taken
together, these results indicate that the observed se-
lectivity of peripheral COMT inhibition may be at-
tributed to the fact that 7b (unlike 1) has limited access
to the brain.
Resu lts a n d Discu ssion
Initial experiments were designed to evaluate the
effect of increasing chain length of new compounds 7a -
7e on both duration of inhibition and brain access and
comparison with standards 1 and 2. Test compounds
were administered by gastric tube to overnight fasted
rats. Thereafter at defined intervals, the animals were
killed by decapitation, and the livers and brains were
removed and used to determine COMT activity (see
Experimental Section). Compounds 7a -7e were found
to rapidly achieve maximal inhibitory effect (within 30
min) after oral administration. The time course inhibi-
tion profiles differed significantly, however (Table 5).

688 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3
Ta ble 2. Modified Carbonyl Derivatives of 7b
Learmonth et al.
compd
R1, R2
mp (°C)
cryst. solvent
formula
C14H13NO4
C14H12N2O5‚0.2H2O
20H17N3O4
C21H16N3F3O4
C20H16N4O6
anal.
8
9
H, H
108-110
135-139
198-200
173-175
216-217
238-240
255-257
Et2O/PE
CH2Cl2/PE
AcOH
AcOH
AcOH
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
dN-OH
dN-NH-Ph
dN-NH-Ph-(4-CF3)
dN-NH-Ph-(4-NO2)
dN-NH-CO-Ph
10
11
12
13
14
C
AcOH
AcOH
C
C
21H17N3O5
21H16N3ClO5
dN-NH-CO-Ph-(4-Cl)
Sch em e 2. Modification of Unsubstituted Aryl Ring of
selective than 17 at the time points studied. Other para
substituents as in the p-methoxy (18) and p-chloro (19)
derivatives also gave long-lasting liver COMT inhibition
(50-60%) until 9 h. At this junction, having established
that potent and selective liver COMT inhibition could
be achieved until at least 9 h, this time-point became
our main focus of interest. Interestingly, electron-
withdrawing groups in particular were very poorly
tolerated (NO2, 25 and 26) in terms of duration of
inhibition, and only carboxyl derivative 27 managed
moderate, though erratic inhibition at 6 and 9 h; even
this effect was virtually lost on cyclization to 28.
7ba
a
Reagents: (a) ArCH2CO2H, ZnCl2, POCl3, 80 °C, (25-38%);
(b) 70% HNO3, AcOH (65-74%); (c) AlCl3, pyridine, EtOAc, ∆, (90-
96%); (d) Ac2O, H2SO4 (cat.), (73%).
That even simple alterations of the carbonyl group of
7b caused marked reduction in COMT inhibition was
quickly determined during in vitro screening (SK-N-SH
cell monolayers, Table 7). Of the aza-compounds 10-
14 (Table 2), only the phenyl derivative 10 retained
reasonable inhibition (77%, identical to 2) compared to
7b (90%). Carbonyl derivatives of 10 such as 13 and 14
displayed only approximately half the activity associ-
ated with 7b, while substitution of the aryl ring of 10
(11, 4-CF3; 12, 4-NO2) led to a substantial two to 3-fold
decrease in activity. In tandem, time course experiments
confirmed that deoxy compound 8 and oxime 9 were
essentially devoid of inhibition of liver COMT at only 6
and 9 h, respectively (Table 8). These results prove that
additional conjugation of the 3,4-dihydroxy-5-nitrophen-
yl pharmacophore with the electron-withdrawing car-
bonyl group is absolutely necessary for high inhibition.
Attempts toward crystallization and crystallographic
characterization of the COMT complex with 7b are in
progress and could serve to clarify in more detail the
role of the carbonyl group in enhancing COMT inhibi-
tory activity.
In contrast, replacement of the hitherto unsubstituted
aromatic ring of 7b with larger, more lipophilic aromatic
groups was reasonably well tolerated (1- or 2-naphthyl,
4′-biphenyl), compounds 20-22 having very good selec-
tivity at 6 h and moderate to high inhibition of liver
COMT at 9 h (Table 8). The saturated cyclic hydrocar-
bon derivative 23, however, exhibited notably higher
inhibition (∼40%) of brain COMT at 6 h. Introduction
of the p-methyl substituent to the aryl ring (as 1
possesses) gave a highly potent and selective inhibitor
17, with an almost identical inhibition profile as 7b.
This would suggest that enzymatic hydroxylation of the
aromatic ring, which normally occurs at the para
position, may not be a major metabolic deactivation
pathway for 7b. The o-methyl analogue 16 also retained
almost 50% liver inhibition at 9 h but was slightly less
Substituents at the R-methylene carbon to the car-
bonyl group were then investigated and also found to
be poorly tolerated. Alkyl derivatives 29-32 were more
conveniently isolated and purified as their diacetates;
rapid hydrolysis of the acetate residues in vivo was
expected to give origin to the corresponding nitro-
catechols. Alkylation with small residues such as the
R-methyl and R-dimethyl derivatives 29 and 30 was
sufficient to noticeably diminish liver COMT inhibition
at 9 h, an effect also seen for R-aryl and R-bromo
analogues 34 and 33, respectively, both equipotent with
29 at 9 h. The R-spiro compound 32 was thereafter
unsurprisingly found as inactive as 30. Interestingly,
the bulkier benzyl derivative 31 did exhibit respectable
liver COMT inhibition at 9 h (41%), but should perhaps
be more correctly regarded as a propan-1-one derivative
more closely related to 7c rather than the ethanone 7b.
Con clu sion s
From the initial series of homologous nitro-catechol
structures, increasing chain length was found to have
a profound effect on the selectivity and duration of
COMT inhibition. 1-(3,4-Dihydroxy-5-nitrophenyl)-2-
phenyl-ethanone 7b was found to possess the optimum
combined properties of potent and selective inhibition
of peripheral COMT with outstanding duration of ac-
tion. A structure-activity relationship study revealed
that conjugation of an unmodified carbonyl moiety with
the already established 3,4-dihydroxy-5-nitrophenyl
pharmacophore is absolutely essential for maintaining
high and prolonged inhibitory activity. Likewise, the
unsubstituted methylene carbon atom R to this carbonyl
group, the major structural difference between 7b and
1, is strictly required to achieve selectively peripheral
COMT inhibition. Prolonged and selective peripheral
COMT inhibition is also dependent upon the nature of
the aromatic ring of 7b. While electron-donating sub-

Synthesis of Catechol-O-methyltransferase Inhibitors
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3 689
Ta ble 3. Modifications of Unsubstituted Aryl Ring of 7b
compd
R1
R2
Ar
mp (°C)
recryst. solvent
formula
C15H13NO5
C15H13NO5
C19H17NO8
anal.
16
17
18
19
20
21
22
23
25
26
27
H
H
Ac
H
H
H
H
H
H
H
Ac
H
H
H
H
H
Ph-(2-CH3)
Ph-(4-CH3)
Ph-(4-OCH3)
Ph-(4-Cl)
1-naphthyl
2-naphthyl
4′-biphenyl
cyclohexyl
Ph-(4-NO2)
Ph-(2-NO2)
Ph-(2-CO2H)
163-165
189-190
88-89
AcOH
AcOH
EtOH
AcOH
AcOH
AcOH
AcOH
AcOH
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
162-164
206-208
190-192
182-184
113-114
140-145
127-130
244-247
C
C
C
C
C
14H10NClO5
18H13NO5
18H13NO5‚0.3H2O
20H15NO5
14H17NO5
Ac
Ac
H
Ac
Ac
H
CH2Cl2/PE
CH2Cl2/PE
EtOH
C18H14N2O9
C18H14N2O9
C15H11NO7
Sch em e 3. Introduction of Electronegative Substituents
to 7ba,b
Sch em e 4. Substitution at R-Methylene Group of 7ba-c
a
Reagents: (a) NaH, alkyl halide, DMF, (65-73%); (b) 10% Pd/
C, NH4+HCO2-, MeOH, ∆, (82-93%); (c) 70% HNO3, AcOH, (65-
73%); (d) AlCl3, pyridine, EtOAc, ∆, (90-99%); (e) Ac2O, H2SO4
(cat.), (90-95%). bCompound 24, PhMe3N+Br3-,THF, (67%). As
c
in Scheme 2 from guaiacol and Ph2CO2H.
peripheral selectivity of COMT inhibition is attributed
to the limited access of 7b to the brain. This compound
is presently under clinical evaluation as an adjunct to
L-Dopa/AADC therapy for the treatment of Parkinson’s
disease.
Exp er im en ta l Section
Ch em istr y. Melting points were measured in open capillary
tubes on an Electrothermal model 9100 hot stage apparatus
and are uncorrected. NMR spectra were recorded on a Bruker
Avance DPX (400 MHz) spectrometer with solvent used as
internal standard, and data are reported in the following
order: chemical shift (ppm), multiplicity (s, singlet; d, doublet;
t, triplet; m, multiplet; br, broad), number of protons, ap-
proximate coupling constant in hertz, and assignment of a
signal. IR spectra were measured with a Bomem Hartmann
& Braun MB Series FTIR spectrometer using KBr tablets.
Analytical HPLC was performed on a Gilson System equipped
with a model 305 pump and 117 UV detector, LiChrospher
100 RP-18 EcoCART 125-3 Cartridges (Merck), in combination
with acetonitrile/water mixtures. Analytical TLC was per-
formed on precoated silica gel plates (Merck 60 Kieselgel F
254) and visualized with UV light. Preparative chromatogra-
phy was done on Merck 60 Kieselgel (0.063-0.2 mm). Elemen-
tal analyses were performed on a Fisons EA 1110 CHNS
instrument, and all analyses are consistent with theoretical
values to within (0.4% unless otherwise indicated (Tables
1-4). Solvents and reagents were purchased from Aldrich, E.
Merck, and Fluka.
a
Reagents: (a) i. 100% HNO3, 0 °C; ii. chromatographic
separation. bReagents: (a) LDA, THF, -78 °C then RT, (66%); (b)
70% HNO3, AcOH, (62%); (c) AlCl3, pyridine, EtOAc, ∆, (72%); (d)
AcOH, H2SO4 (cat.), ∆, (61%).
stituents and p-alkyl substitution in particular are well
tolerated, electron-withdrawing substituents lead to a
striking reduction in activity and/or selectivity at 6 and
9 h after administration. However, replacement of the
same ring with larger, more lipophilic aromatic rings
such as naphthyl and biphenyl rings is relatively well
tolerated, suggesting possibilities for further investiga-
tion.
Ethanone 7b (BIA 3-202) presents a COMT inhibition
profile more similar to entacapone 2 than tolcapone 1,
but it possesses the additional benefit of markedly
prolonged duration of peripheral COMT inhibition. The
The following details are representative procedures for
synthesis of compounds 7a -7e.
4-Ben zyloxy-3-m eth oxyben za ld eh yd e (3, R ) Bn ). To
a vigorously stirred solution of vanillin (3, R ) H, 60 g, 395
mmol) in acetone (600 mL) at room temperature was added
finely powdered potassium carbonate (148 g, 1072 mmol). The

690 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3
Ta ble 4. Modifications of R-Methylene Group of 7b
Learmonth et al.
compd
R1
R2
R3
R4
mp (°C)
recryst. solvent
formula
anal.
29
30
31
32
33
34
Ac
Ac
Ac
Ac
Ac
H
Ac
Ac
Ac
Ac
Ac
H
H
CH3
H
-(CH2)5-
H
H
CH3
CH3
CH2Ph
110-111
116-118
126-128
166-168
124-126
204-205
EtOH
EtOH
EtOH
EtOH
Et2O
C19H17NO7
C20H19NO7
C25H21NO7
C23H23NO7
C18H14NBrO7
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
Br
Ph
AcOH
C20H15NO5
Ta ble 5. Percent Inhibition of COMT Activity by Compounds
7a -7e, Tolcapone 1, and Entacapone 2 in Homogenates of Rat
Brain and Liver, Determined at 0.5, 1, 3, 6, and 9 h after Their
Administration (all at 30 mg/kg) by Gastric Tubea
Brain Time Course % Inhibition
no.
0.5 h
1 h
3 h
6 h
9 h
7a
7b
7c
7d
7e
2
96 ( 1
84 ( 1
90 ( 1
85 ( 2
87 ( 1
72 ( 7
99 ( 1
96 ( 1
81 ( 3
86 ( 1
69 ( 5
74 ( 4
45 ( 7
99 ( 1
97 ( 1
65 ( 4
60 ( 6
33 ( 4
25 ( 3
30 ( 6
97 ( 1
86 ( 7
32 ( 3
33 ( 7
27 ( 4
-6 ( 7
20 ( 7
86 ( 8
35 ( 6
22 ( 3
1 ( 5
12 ( 6
-7 ( 5
23 ( 3
78 ( 2
1
Liver Time Course (% Inhibition)
no.
0.5 h
1 h
3 h
6 h
9 h
7a
7b
7c
7d
7e
2
99 ( 1
99 ( 1
98 ( 1
97 ( 1
99 ( 1
98 ( 1
100 ( 1
98 ( 1
97 ( 2
98 ( 1
95 ( 1
99 ( 1
96 ( 1
99 ( 1
97 ( 3
96 ( 1
95 ( 1
67 ( 8
88 ( 4
86 ( 2
98 ( 1
81 ( 7
76 ( 4
71 ( 13
52 ( 10
36 ( 6
74 ( 5
94 ( 1
32 ( 6
70 ( 4
40 ( 11
39 ( 13
-4 ( 8
25 ( 8
67 ( 4
1
a
Results are means ( SEM of four experiments per group.
resulting suspension was stirred at steady reflux for 2 h and
then allowed to cool to room temperature. The inorganic
material was removed by filtration, and the filter cake was
washed by acetone (100 mL). Evaporation of the solvent (40
°C, water aspirator pressure) left an oily residue, which was
crystallized from a diethyl ether/petroleum ether mixture (500
mL, 1:2) to afford glistening white crystals (88.4 g, 93%) of
1
mp 61-63 °C. H NMR (CDCl3) δ 9.86 (s, 1H, CHO), 7.5-7.3
(m, 7H, H-2, H-6, Ph), 7.01 (d, 1H, J ) 8.2 Hz, H-5), 5.27 (s,
2H, CH2), 3.97 (s, 3H, OCH3). 13C NMR (CDCl3) δ 191.5, 154.2,
150.6, 136.6, 130.8, 129.3, 128.8, 127.8, 127.2, 112.9, 109.8,
71.4, 56.6.
F igu r e 3. Brain and liver COMT activity after oral admin-
istration of 1 (open squares), 2 (open circles), and 7b (closed
squares) (all at 30 mg/kg).
1-(4-Ben zyloxy-3-m eth oxyph en yl)-2-ph en yl-eth an ol (4b,
R ) Bn , n ) 1). In a flame-dried three-necked (500 mL) round-
bottomed flask flushed by a stream of nitrogen was placed
oven-dried magnesium turnings (8.3 g, 341 mmol) and a single
crystal of iodine. Anhydrous diethyl ether (Aldrich, 75 mL) was
added, followed by a few drops of neat benzyl chloride. On
discoloration of the yellow color, stirring was started and a
solution of benzyl chloride (35.7 g, 282 mmol) in anhydrous
diethyl ether (150 mL) was added so as to maintain steady
reflux. When the exothermic reaction subsided, the mixture
was cooled in an ice-water bath and a solution of the aldehyde
3 (54.5 g, 225 mmol) in anhydrous tetrahydrofuran (Aldrich,
200 mL) was added dropwise. The resulting mixture was
allowed to stir at room temperature for 1 h, then cooled again
and quenched by careful addition of excess 2 N hydrochloric
acid. Unreacted magnesium was removed by filtration, and
the organic phase of the filtrate separated. The aqueous phase
was extracted by diethyl ether (50 mL), and the combined
organic layers were washed by water (100 mL) and brine (100
mL), then dried over anhydrous sodium sulfate, filtered, and
Ta ble 6. IC50 Values (in nM) for Inhibition of Rat Brain and
Liver COMT
no.
brain
liver
1
2
7b
2.2 (0.8, 6.4)
12.8 (4.0, 41.3)
3.7 (1.7, 8.1)
927 (551, 1561)
2320 (741, 7263)
696 (356, 1360)
evaporated (40 °C, water aspirator pressure). The residue was
recrystallized from a dichloromethane/petroleum ether mixture
(200 mL, 1:2) to afford white crystals (70.1 g, 93%) of mp 96-
1
98 °C. H NMR (CDCl3) δ 7.5-7.15 (m, 10H, 2 × Ph), 6.92 (d,
1H, J ) 1.9 Hz, H-2), 6.87 (d, 1H, J ) 8.2 Hz, H-5), 6.82 (dd,
1H, J ) 1.9, 8.2 Hz, H-6), 5.17 (s, 2H, OCH2), 4.86 (t, 1H),
3.02 (m, 2H, CH2), 3.89 (s, 3H, OCH3). 13C NMR (CDCl3) δ
150.2, 148.1, 138.6, 137.7, 137.6, 130.1, 129.1, 129.1, 128.4,
127.8, 127.2, 118.6, 114.4, 110.2, 75.8, 71.7, 56.6, 46.6.
1-(4-B e n zy lo x y -3-m e t h o x y p h e n y l)-2-p h e n y l-e t h a -
n on e (5b, R ) Bn , n ) 1). To a stirred suspension of the

Synthesis of Catechol-O-methyltransferase Inhibitors
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3 691
Ta ble 7. Percent Inhibition of COMT Activity in SK-N-SH
Cells by Compounds 1, 2, 7b, and 10-14 (100 nM)a
Ta ble 8. Percent Inhibition of COMT Activity by Derivatives
of 7b in Homogenates of Rat Brain and Liver, Determined
between 6 and 9 h after Administration (all at 30 mg/kg) by
Gastric Tubea
compound
% inhibition
1
2
97 ( 1
77 ( 3
90 ( 1
77 ( 3
38 ( 4
28 ( 4
45 ( 7
50 ( 2
liver
brain
7b
10
11
12
13
14
compd
6 h
9 h
6 h
9 h
8
9
0 ( 13
48 ( 9
74 ( 5
83 ( 7
72 ( 5
69 ( 4
70 ( 3
83 ( 2
78 ( 5
72 ( 12
49 ( 7
28 ( 2
39 ( 9
15 ( 12
42 ( 3
19 ( 3
63 ( 6
14 ( 2
48 ( 2
13 ( 1
12 ( 3
18 ( 10
46 ( 11
70 ( 8
53 ( 3
57 ( 8
38 ( 4
46 ( 10
51 ( 4
36 ( 3
11 ( 10
20 ( 13
16 ( 5
14 ( 14
24 ( 8
9 ( 5
10 ( 3
13 ( 8
33 ( 2
23 ( 6
25 ( 2
12 ( 3
10 ( 5
17 ( 4
28 ( 5
39 ( 7
0 ( 3
20 ( 3
34 ( 5
29 ( 8
44 ( 2
23 ( 4
44 ( 2
19 ( 2
20 ( 2
7 ( 5
16 ( 2
15 ( 2
25 ( 7
21 ( 9
9 ( 8
16
17
18
19
20
21
22
23
25
26
27
28
29
30
31
32
33
34
a
26 ( 2
1 ( 7
Results are means ( SEM of four experiments per group.
7 ( 3
27 ( 5
6 ( 3
1 ( 4
7 ( 3
42 ( 3
11 ( 2
0 ( 7
15 ( 1
0 ( 8
41 ( 2
9 ( 8
36 ( 8
20 ( 7
7 ( 2
13 ( 5
0 ( 1
a
Results are means ( SEM of four experiments per group.
(46.1 g, 732 mmol) in methanol (550 mL) at room temperature
was added carefully a slurry of 10 % palladium on charcoal
(2.5 g) in methanol (50 mL). The resulting dark suspension
was gradually warmed to gentle reflux (vigorous gas evolution)
and after 30 min allowed to cool to room temperature. After
cooling in an ice-water bath, water (200 mL) and concentrated
hydrochloric acid (60 mL) was slowly added. Further water
(500 mL), followed by dichloromethane (500 mL), was added,
and the mixture was filtered through a Celite pad. The filter
cake was washed by dichloromethane (100 mL), and the
organic phase of the filtrate was separated. The aqueous phase
was extracted by dichloromethane (100 mL), and the combined
organic layers were washed by water (100 mL) and brine (100
mL), then dried over anhydrous sodium sulfate, filtered, and
evaporated (40 °C, water aspirator pressure). The residue was
recrystallized from a dichloromethane/petroleum ether mixture
(300 mL, 1:2) to give white crystals (41.6 g, 94%) of mp 106-
108 °C. 1H NMR (CDCl3) δ 7.65 (dd, 1H, J ) 2.1, 8.2 Hz, H-6),
7.59 (d, 1H, J ) 2.1 Hz, H-2), 7.4-7.2 (m, 5H, Ph), 6.96 (d,
1H, J ) 8.2 Hz, H-5), 6.16 (br, 1H, 4-OH), 4.26 (s, 2H, CH2),
3.94 (s, 3H, OCH3). 13C NMR (CDCl3) δ 196.8, 150.9, 147.1,
135.5, 129.9, 129.7, 129.1, 127.2, 124.6, 114.2, 110.7, 56.4, 45.5.
1-(4-Hyd r oxy-3-m eth oxy-5-n itr op h en yl)-2-p h en yl-eth -
a n on e (6b, n ) 1). To a stirred semi-solution of the phenol
5b (40 g, 165 mmol) obtained above in acetic acid (400 mL) at
room temperature was added dropwise 70% nitric acid (88 mL,
177 mmol), causing formation of a deep red solution followed
by a copious orange precipitate. After stirring for 30 min, the
mixture was poured slowly onto stirred ice-water (1000 mL).
The resulting precipitate was filtered and washed by water
(200 mL). Recrystallization from ethanol (150 mL) afforded
bright yellow crystals (33.6 g, 71%) of mp 129-130 °C. 1H NMR
(CDCl3) δ 11.14 (br, 1H, 4-OH), 8.43 (d, 1H, J ) 2.1 Hz, H-6),
7.79 (d, 1H, J ) 2.1 Hz, H-2), 7.4-7.2 (m, 5H, Ph), 4.30 (s,
2H, CH2), 4.00 (s, 3H, OCH3). 13C NMR (CDCl3) δ 195.1, 150.9,
150.5, 134.3, 133.3, 129.7, 129.3, 127.9, 127.7, 118.3, 116.3,
57.3, 45.6.
F igu r e 4. Concentration dependent inhibition of brain and
liver COMT activity by 1 (open squares), 2 (open circles), and
7b (closed squares) at 1 h after administration.
foregoing ethanol 4b (70 g, 210 mmol) in toluene (600 mL) at
room temperature was added sodium tert-butoxide (25.2 g, 262
mmol) followed by cyclohexanone (102.6 g, 1046 mmol). The
resulting mixture was warmed until gentle reflux and after
30 min left to cool to 50 °C. Water (150 mL) was added slowly
with stirring, and the phases were separated. The aqueous
phase was extracted by ethyl acetate (100 mL), and the
combined organic layers were washed by brine (100 mL) and
then evaporated (60 °C, water aspirator pressure). The residue
was recrystallized from 96% ethanol (200 mL) to afford off-
white crystals (63.5 g, 91%) of mp 136-138 °C. 1H NMR
(CDCl3) δ 7.61 (m, 2H, H-2, H-6), 7.5-7.2 (m, 10H, 2 x Ph),
6.91 (d, 1H, J ) 8.9 Hz, H-5), 5.24 (s, 2H, OCH2), 4.25 (s, 2H,
CH2), 3.94 (s, 3H, OCH3). 13C NMR (CDCl3) δ 196.7, 152.9,
149.9, 136.6, 135.4, 130.4, 129.7, 129.1, 129.1, 128.6, 127.6,
127.2, 123.7, 112.5, 111.5, 71.2, 56.4, 45.6.
1-(3, 4-Dih yd r oxy-5-n itr op h en yl)-2-p h en yl-eth a n on e
(7b, n ) 1). To a stirred yellow suspension of the methyl ether
6b (30 g, 104 mmol) obtained above in ethyl acetate (300 mL)
at room temperature was added aluminum chloride (16.7 g,
125 mmol) in one portion. To the resulting orange/red suspen-
sion was added dropwise pyridine (33 g 418 mmol), causing
the internal temperature to rise to 45 °C. The orange solution
was then heated at reflux for 2 h and then allowed to cool to
60 °C whereupon the reaction mixture was carefully added to
1-(4-Hydr oxy-3-m eth oxyph en yl)-2-ph en yl-eth an on e (5b,
R ) H, n ) 1). To a stirred suspension of the benzyl ketone
5b (60.7 g, 183 mmol) from above and ammonium formate

692 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3
Learmonth et al.
a mixture of ice/concentrated hydrochloric acid (120 mL). After
being stirred at 50 °C for 1 h, the mixture was cooled in an
ice/water bath for 1 h and then filtered. The filter cake was
washed by water (100 mL), and the product then dried (70
°C, 0.02 mmHg, 5 h) to afford the title product as a yellow
solid (28.3 g, 99%). IR(KBr) 3352 (OH), 1669 (CdO), 1539
c. A stirred solution of the orange oil (0.28 g, 1 mmol) in
ethyl acetate (15 mL) was treated with aluminum chloride
(0.24 g, 1.83 mmol) and pyridine (0.35 g, 4.48 mmol) as
described for 7b to give 8 as yellow crystals (0.1 g, 38%). IR-
(KBr) 3385 (OH), 1551 (NO2). 1H NMR (CDCl3) δ 10.51 (br,
1H, 4-OH), 7.46 (d, 1H, J ) 2.1 Hz, H-6), 7.09 (d, 1H, J ) 2.1
Hz, H-2), 7.35-7.15 (m, 5H, Ph), 5.80 (br, 1H, 3-OH), 2.9 (m,
4H, CH2CH2). 13C NMR (CDCl3) δ 146.6, 141.5, 141.0, 134.2,
133.7, 128.9, 128.8, 126.7, 122.7, 115.3, 37.7, 37.3.
1
(NO2). H NMR (DMSO-d6) δ 10.9 (br, 2H, 3-OH, 4-OH), 8.09
(d, 1H, J ) 2.1 Hz, H-6), 7.63 (d, 1H, J ) 2.1 Hz, H-2), 7.35-
7.20 (m, 5H, Ph), 4.33 (s, 2H, CH2). 13C NMR (DMSO-d6) δ
196.0, 148.5, 146.6, 138.0, 135.9, 130.6, 129.2, 127.5, 127.4,
118.2, 117.4, 45.0.
1-(3,4-Dih yd r oxy-5-n it r op h en yl)-1-h yd r oxyim in o-2-
p h en yl-eth a n e (9). A stirred suspension of 7b (0.33 g, 1.2
mmol) in absolute ethanol (6 mL) was treated with hydroxy-
lamine hydrochloride (0.29 g, 4.2 mmol) and pyridine (0.28 g,
3.6 mmol), and the mixture was heated at reflux for 1 h. The
mixture was evaporated (40 °C, water aspirator pressure), and
the residue treated with water (5 mL). The precipitate was
collected by filtration and recrystallized from a dichloromethane/
toluene mixture to give orange crystals (0.12 g, 34%). IR(KBr)
By application of similar procedures, the following were also
obtained:
1-(3, 4-Dih yd r oxy-5-n itr op h en yl)-1-p h en yl-m eth a n on e
1
(7a , n ) 0). IR(KBr) 3353 (OH), 1640 (CdO), 1539 (NO2). H
NMR (DMSO-d6) δ 10.94 (br, 2H, 3-OH, 4-OH), 7.77 (d, 2H,
o-Ph), 7.72 (t, 1H, p-Ph), 7.72 (d, 1H, J ) 2.1 Hz, H-6), 7.57 (t,
2H, m-Ph), 7.49 (d, 1H, J ) 2.1 Hz, H-2). 13C NMR (DMSO-
d6) δ 194.2, 148.8, 147.0, 138.0, 137.7, 133.5, 130.3, 129.6,
127.7, 120.0, 119.0.
1
3385 (OH), 3254 (OH, oxime), 1548 (NO2). H NMR (CDCl3) δ
8.6 (vbr, 2H, 3-OH, 4-OH), 7.92 (d, 1H, J ) 2.1 Hz, H-6), 7.62
(d, 1H, J ) 2.1 Hz, H-2), 7.35-7.15 (m, 5H, Ph), 4.20 (s, 2H,
CH2). 13C NMR (CDCl3) δ 156.0, 147.1, 144.3, 136.3, 134.0,
129.4, 129.1, 128.2, 127.3, 120.0, 114.7, 32.1.
1-(3, 4-Dih yd r oxy-5-n itr op h en yl)-3-p h en yl-p r op a n -1-
on e (7c, n ) 2). IR(KBr) 3373 (OH), 1664 (CdO), 1549 (NO2).
1H NMR (CDCl3) δ 11.0 (br, 1H, 4-OH), 8.29 (d, 1H, J ) 2.1
Hz, H-6), 7.86 (d, 1H, J ) 2.1 Hz, H-2), 7.35-7.20 (m, 5H,
Ph), 6.1 (br, 1H, 3-OH), 3.30 (t, 2H, COCH2), 3.10 (t, 2H, CH2-
Ph). 13C NMR (CDCl3) δ 196.5, 147.2, 146.7, 141.1, 133.5, 129.3,
129.0, 128.8, 126.7, 120.6, 117.0, 40.5, 30.4.
1-(3,4-Dih yd r oxy-5-n itr op h en yl)-2-p h en yl-1-p h en ylh y-
d r a zon o-eth a n e (10). A stirred solution of 7b (0.2 g, 0.73
mmol) and phenylhydrazine (0.28 g, 2.6 mmol) in 96% ethanol
(5 mL) and acetic acid (3 drops) was stirred at reflux for 3 h.
On cooling, the orange precipitate was filtered off and recrys-
tallized from acetic acid to give orange crystals (0.14 g, 53%).
IR(KBr) 3536 (OH), 3332 (NH), 1535 (NO2). 1H NMR (DMSO-
d6) δ 10.3 (br, 2H, 3-OH, 4-OH), 9.84 (br, 1H, NH), 7.71 (d,
1H, J ) 2.1 Hz, H-2), 7.58 (d, 1H, J ) 2.1 Hz, H-6), 7.40-7.10
(m, 9H, 2 × Ph), 6.79 (t, 1H, NHPh), 4.21 (s, 2H, CH2). 13C
NMR (DMSO-d6) δ 148.4, 146.7, 142.7, 140.3, 137.9, 137.7,
130.3, 130.0, 129.8, 129.1, 127.3, 120.2, 117.1, 113.8, 112.5,
31.7.
1-(3,4-Dih yd r oxy-5-n it r op h e n yl)-4-p h e n yl-b u t a n -1-
on e (7d , n ) 3). IR(KBr) 3381, 3335 (OH), 1663 (CdO), 1548
1
(NO2). H NMR (DMSO-d6) δ 10.8 (br, 2H, 3-OH, 4-OH), 7.93
(d, 1H, J ) 2.1 Hz, H-6), 7.57 (d, 1H, J ) 2.1 Hz, H-2), 7.35-
7.10 (m, 5H, Ph), 2.97 (t, 2H, COCH2), 2.63 (t, 2H, CH2Ph),
1.89 (qui, 2H, CH2CH2CH2). 13C NMR (DMSO-d6) δ 198.2,
148.6, 146.6, 142.8, 138.1, 129.35, 129.3, 128.0, 126.8, 118.0,
116.9, 37.8, 35.4, 26.6.
1-(3, 4-Dih yd r oxy-5-n itr op h en yl)-5-p h en yl-p en ta n -1-
on e (7e, n ) 4). IR(KBr) 3368 (OH), 1675 (CdO), 1544 (NO2).
1H NMR (CDCl3) δ 11.0 (br, 1H, 4-OH), 8.29 (d, 1H, J ) 2.1
Hz, H-6), 7.85 (d, 1H, J ) 2.1 Hz, H-2), 7.40-7.10 (m, 5H,
Ph), 6.0 (br, 1H, 3-OH), 2.97 (t, 2H, COCH2), 2.69 (t, 2H, CH2-
Ph), 1.85-1.70 (m, 4H, CH2CH2CH2CH2). 13C NMR (CDCl3) δ
197.5, 147.3, 146.7, 142.6, 133.7, 129.6, 129.0, 128.9, 126.4,
120.8, 117.1, 38.6, 36.3, 31.5, 24.3.
By application of similar procedures, the following were also
obtained:
1-(3,4-Dih yd r oxy-5-n itr op h en yl)-2-p h en yl-1-(4-tr iflu o-
r om eth yl)p h en ylh yd r a zon o-eth a n e (11). Yield, 42%. IR-
1
(KBr) 3496 (OH), 3330 (NH), 1532 (NO2). H NMR (CDCl3) δ
10.8 (br, 1H, 4-OH), 7.98 (d, 1H, J ) 2.1 Hz, H-6), 7.95 (d, 1H,
J ) 2.1 Hz, H-2), 7.75 (br, 1H, NH), 7.55-710 (m, 9H, 2 x Ph),
5.9 (br, 1H, 3-OH), 4.14 (s, 2H, CH2). 13C NMR (CDCl3) δ 147.4,
147.1, 143.8, 142.0, 134.5, 134.0, 131.5, 130.2, 128.3, 128.2,
127.2, 127.2, 119.3, 113.5, 113.3, 32.6.
1-(3,4-Dih yd r oxy-5-n itr op h en yl)-2-p h en yl-eth a n e (8).
a . To a stirred solution of the benzyl alcohol 4b (R ) Bn, n )
1) (1 g, 3 mmol) in methanol (40 mL) at room temperature
was added concentrated hydrochloric acid (1 mL) followed by
10% palladium on charcoal (0.35 g). Hydrogen gas was bubbled
through the dark suspension for 2 h, and then the catalyst
was removed by filtration through Celite. The filter cake was
washed by methanol (10 mL), and the combined filtrate was
evaporated (40 °C, water aspirator pressure) to leave a pale
orange oil (0.67 g, 98%), which was used without further
1-(3,4-Dih yd r oxy-5-n itr op h en yl)-1-(4-n itr op h en yl)h y-
d r a zon o-2-p h en yl-et h a n e (12). Yield, 45%. IR(KBr) 3493
(OH), 3305 (NH), 1541 (broad, NO2). 1H NMR (DMSO-d6) δ
10.7 (br, 1H, NH), 10.4 (br, 2H, 3-OH, 4-OH), 8.17 (d, 2H,
NHPh), 7.69 (d, 1H, J ) 2.1 Hz, H-2), 7.66 (d, 1H, J ) 2.1 Hz,
H-6), 7.40-7.10 (m, 7H, Ph, Ph), 4.29 (s, 2H, CH2). 13C NMR
(DMSO-d6) δ 152.1, 148.5, 146.0, 143.4, 139.8, 138.1, 137.2,
129.9, 129.1, 129.1, 127.5, 127.0, 117.5, 113.6, 113.2, 32.3.
1-(3,4-Dih yd r oxy-5-n itr op h en yl)-1-ben zoylh yd r a zid o-
2-p h en yl-eth a n e (13) Yield, 56%. IR(KBr) 3362 (OH), 3200
(NH), 1668 (CdO), 1541 (NO2). 1H NMR (DMSO-d6) δ 11.0 (br,
1H, NH), 10.5 (br, 2H, 3-OH, 4-OH), 7.80-7.10 (m, 12H, H-2,
H-6, Ph, Ph), 4.38 (s, 2H, CH2). 13C NMR (DMSO-d6) δ 165.4,
153.5, 148.5, 144.0, 138.0, 137.2, 135.0, 132.6, 129.8, 129.3,
129.1, 128.9, 127.5, 118.0, 114.7, 32.9.
1-(3,4-Dih yd r oxy-5-n it r op h en yl)-1-(4-ch lor ob en zoyl)-
h yd r a zid o-2-p h en yl-eth a n e (14). Yield, 49%. IR(KBr) 3304
(OH), 1647 (CdO), 1532 (NO2). 1H NMR (DMSO-d6) δ 11.0 (br,
1H, NH), 10.5 (br, 2H, 3-OH, 4-OH), 7.80-7.20 (m, 11H, Ph),
4.36 (s, 2H, CH2). 13C NMR (DMSO-d6) δ 164.4, 154.0, 144.1,
138.0, 137.2, 133.6, 130.9, 129.8, 129.3, 129.1, 128.7, 127.5,
118.0, 114.8, 33.1.
1
purification. H NMR (CDCl3) δ 7.35-7.15 (m, 5H, Ph), 6.86
(d, 1H, J ) 8.2 Hz, H-5), 6.71 (dd, 1H, J ) 2.1, 8.2 Hz, H-6),
6.64 (d, 1H, J ) 2.1 Hz, H-2), 5.50 (br, 1H, 4-OH), 3.86 (s, 3H,
OCH3), 2.90 (m, 4H, CH2CH2). 13C NMR (CDCl3) δ 146.6, 144.1,
142.2, 134.1, 129.0, 128.7, 126.3, 121.4, 114.6, 111.5, 56.2, 38.7,
38.0.
b. A stirred and cooled (ice bath) solution of the oil from
above (0.57 g, 2.51 mmol) in diethyl ether (15 mL) was treated
dropwise with 100% nitric acid (0.11 mL, 2.76 mmol). The
resulting deep red solution was stirred at room temperature
for 1 h and then poured onto ice-water (20 mL). The mixture
was extracted by diethyl ether (20 mL) and the organic phase
washed by water (20 mL) and brine (20 mL), then dried over
anhydrous sodium sulfate, filtered, and evaporated (40 °C,
water aspirator pressure). The residue was chromatographed
over silica gel (petroleum ether/ethyl acetate, 4:1) to give an
orange oil (0.3 g, 44%). 1H NMR (CDCl3) δ 10.68 (br, 1H, 4-OH),
7.52 (d, 1H, J ) 2.1 Hz, H-6), 7.4-7.1 (m, 5H, Ph), 6.80 (d,
1H, J ) 2.1 Hz, H-2), 3.85 (s, 3H, OCH3), 2.93 (m, 4H, CH2-
CH2). 13C NMR (CDCl3) δ 149.9, 145.1, 141.0, 134.0, 133.2,
129.0, 128.9, 126.7, 119.2, 115.4, 57.0, 37.9, 37.6.
The following details are representative procedures for
synthesis of compounds 16-23.
1-(3,4-Dih yd r oxy-5-n itr op h en yl)-2-(1′-n a p h th yl)-eth a -
n on e (20). A stirred suspension of guaiacol (1.24 g, 10 mmol),
1-naphthylacetic acid (1.86 g, 10 mmol), and zinc chloride (5
g, 36.7 mmol) in phosphorus oxychloride (24.7 g, 160 mmol)

Synthesis of Catechol-O-methyltransferase Inhibitors
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3 693
was heated at 80 °C for 2 h and then allowed to cool. The
purple mixture was carefully added to ice-water (200 mL)
(CAUTION: exothermic) and then extracted by dichlo-
romethane (2 × 50 mL). The extracts were washed by water
(50 mL) and brine (50 mL), then dried over anhydrous sodium
sulfate, filtered, and evaporated (40 °C, water aspirator
pressure). The residue was chromatographed over silica gel
(petroleum ether/ethyl acetate, 2:1) to give the intermediate
ketone 15 (Ar ) 1-naphthyl) as beige crystals, (1.08 g, 37%) of
(d, 2H, J ) 6.8 Hz, CH2), 1.97 (m, 1H, CH), 1.8-1.0 (m, 10H,
c-hexyl). 13C NMR (CDCl3) δ 197.5, 147.3, 146.7, 133.7, 130.1,
120.9, 117.2, 46.3, 35.1, 33.9, 26.7, 26.6.
1-(3,4-Dih yd r oxy-5-n it r op h e n yl)-2,2-d ip h e n yl-e t h a -
1
n on e (34). IR(KBr) 3400 (OH), 1669 (CdO), 1547 (NO2). H
NMR (DMSO-d6) δ 10.9 (vbr, 2H, 3-OH, 4-OH), 8.10 (d, 1H, J
) 2.1 Hz, H-6), 7.64 (d, 1H, J ) 2.1 Hz, H-2), 7.40-7.10 (m,
10H, 2 x Ph), 6.33 (s, 1H, CH). 13C NMR (DMSO-d6) δ 196.4,
148.7, 147.0, 140.4, 138.1, 130.0, 129.6, 127.9, 127.4, 118.9,
118.0, 58.2.
1
mp 121-122 °C. H NMR (CDCl3) δ 8.0-7.8 (m, 3H, Ar), 7.74
(dd, 1H, J ) 1.8, 8.2 Hz, H-6), 7.61 (d, 1H, J ) 1.8 Hz, H-2),
7.55-7.35 (m, 4H, Ph), 6.98 (d, 1H, J ) 8.2 Hz, H-5), 6.11 (br,
1H, 4-OH), 4.71 (s, 2H, CH2), 3.92 (s, 3H, OCH3). 13C NMR
(CDCl3) δ 196.8, 151.1, 147.3, 134.5, 132.8, 132.4, 130.2, 129.4,
128.5, 128.3, 126.9, 126.3, 126.1, 124.5, 124.4, 114.4, 110.9,
56.6, 43.3.
Nitration (as described for 6b, n ) 1, 78%) and demethy-
lation (as described for 7b, 93%) gave the title compound 20
as yellow crystals. IR(KBr) 3376 (OH), 1669 (CdO), 1546
(NO2). 1H NMR (DMSO-d6) δ 10.9 (vbr, 2H, 3-OH, 4-OH), 8.22
(d, 1H, J ) 1.8 Hz, H-6), 8.0-7.8 (m, 3H, Ar), 7.66 (d, 1H, J )
1.8 Hz, H-2), 7.6-7.3 (m, 4H, Ar), 4.85 (s, 2H, CH2). 13C NMR
(DMSO-d6) δ 196.2, 148.7, 146.9, 138.3, 134.4, 133.2, 133.1,
129.4, 129.3, 128.3, 127.8, 127.0, 126.6, 126.5, 125.5, 118.3,
117.5, 43.0.
3,4-Dia cet oxy-5-n it r op h en yl-2-p h en yl-et h a n on e (24).
To a stirred suspension of 7b (4.1 g, 15 mmol) in acetic
anhydride (48 g, 470 mmol) was added two drops of concen-
trated sulfuric acid. After being stirred for 30 min, the mixture
was poured onto ice-water (500 mL) and the precipitate was
filtered off, washed by water (50 mL), and dried to give the
product as an off-white solid, (41.5 g, 77%) of mp 92-93 °C.
(C, H, N). IR(KBr) 1778 (CdO, ester), 1699 (CdO, ketone),
1
1539 (NO2). H NMR (CDCl3) δ 8.61 (d, 1H, J ) 2.1 Hz, H-6),
8.59 (d, 1H, J ) 2.1 Hz, H-2), 7.45-7.15 (m, 5H, Ph), 4.3 (s,
2H, CH2), 2.42 (s, 3H, COCH3), 2.38 (s, 3H, COCH3). 13C NMR
(CDCl3) δ 193.9, 168.0, 145.1, 143.1, 140.9, 134.6, 133.3, 129.8,
129.5, 129.1, 128.8, 128.6, 127.9, 125.7, 123.4, 45.9, 20.9, 20.8.
3,4-Dia cet oxy-5-n it r op h en yl-2-(4′-n it r op h en yl)-et h a -
n on e (25) a n d 3,4-Dia cetoxy-5-n itr op h en yl-2-(2′-n itr o-
p h en yl)-eth a n on e (26). To 100% nitric acid (3 mL) at 0 °C
(ice-salt bath) was added 24 (1.07 g, 3 mmol) in portions with
stirring over 15 min. When addition was complete, the mixture
was poured onto ice-water (100 mL). The precipitate was
filtered off and washed with water (20 mL). Chromatography
on silica gel (petroleum ether/ethyl acetate, 2:1) allowed
separation of the faster-running product which, after recrys-
tallization was identified as the 4′-nitro isomer 25 (0.29 g,
24%). IR(KBr) 1779 (CdO, ester), 1696 (CdO, ketone), 1535
(very strong, NO2). 1H NMR (CDCl3) δ 8.61 (d, 1H, J ) 2.1
Hz, H-6), 8.10 (d, 1H, J ) 2.1 Hz, H-2), 8.30-7.4 (m, 4H, Ph),
4.45 (s, 2H, CH2), 2.42 (s, 3H, COCH3), 2.39 (s, 3H, COCH3).
13C NMR (CDCl3) δ 192.7, 168.1, 167.3, 148.0, 145.6, 143.5,
141.5, 140.8, 131.3, 128.8, 124.6, 123.2, 45.4, 21.1, 21.0.
The slower running product obtained from the column was
recrystallized and identified as the 2′-nitro isomer 26 (0.25 g,
21%). IR(KBr) 1779 (CdO, ester), 1696 (CdO, ketone), 1529
(very strong, NO2). 1H NMR (CDCl3) δ 8.64 (d, 1H, J ) 2.1
Hz, H-6), 8.10 (d, 1H, J ) 2.1 Hz, H-2), 8.20-7.45 (m, 4H,
Ph), 4.7 (s, 2H, CH2), 2.43 (s, 3H, COCH3), 2.41 (s, 3H, COCH3).
13C NMR (CDCl3) δ 192.3, 168.0, 167.2, 148.9, 145.2, 143.3,
141.3, 134.4, 134.1, 129.4, 129.8, 128.7, 126.0, 123.0, 44.7, 20.9,
20.8.
By application of similar procedures the following were
obtained:
1-(3,4-Dih yd r oxy-5-n itr op h en yl)-2-(2′-m eth ylp h en yl)-
eth a n on e (16). IR(KBr) 3365 (OH), 1669 (CdO), 1544 (NO2).
1H NMR (DMSO-d6) δ 10.9 (vbr, 2H, 3-OH, 4-OH), 8.11 (d,
1H, J ) 2.1 Hz, H-6), 7.62 (d, 1H, J ) 2.1 Hz, H-2), 7.20-7.10
(m, 4H, Ph), 4.37 (s, 2H, CH2), 2.14 (s, 3H, CH3). 13C NMR
(DMSO-d6) δ 196.0, 148.7, 146.8, 138.2, 137.9, 135.1, 131.5,
130.9, 127.9, 127.8, 126.7, 118.2, 117.3, 43.5, 20.3.
1-(3,4-Dih yd r oxy-5-n itr op h en yl)-2-(4′-m eth ylp h en yl)-
eth a n on e (17). IR(KBr) 3357 (OH), 1670 (CdO), 1540 (NO2).
1H NMR (DMSO-d6) δ 10.9 (vbr, 2H, 3-OH, 4-OH), 8.07 (d,
1H, J ) 2.1 Hz, H-6), 7.61 (d, 1H, J ) 2.1 Hz, H-2), 7.20-7.00
(m, 4H, Ph), 4.26 (s, 2H, CH2), 2.26 (s, 3H, CH3). 13C NMR
(DMSO-d6) δ 196.2, 148.7, 146.8, 138.2, 136.5, 132.9, 130.5,
130.0, 127.6, 118.4, 117.5, 44.8, 21.7.
1-(3,4-Dia cetoxy-5-n itr op h en yl)-2-(4′-m eth oxyp h en yl)-
eth a n on e (18). IR(KBr) 1779 (CdO, ester), 1687 (CdO,
1
ketone), 1543 (NO2). H NMR (CDCl3) δ 8.60 (d, 1H, J ) 2.1
Hz, H-6), 8.12 (d, 1H, J ) 2.1 Hz, H-2), 7.18 (d, 2H, J ) 8.6
Hz, Ph), 6.9 (d, 2H, J ) 8.6 Hz, Ph), 4.25 (s, 2H, CH2), 3.81 (s,
3H, CH3). 13C NMR (CDCl3) δ 194.4, 168.1, 167.4, 159.5, 145.3,
141.0, 134.8, 131.0, 129.0, 125.3, 123.6, 115.1, 55.8, 45.3, 21.1,
21.0.
2-(2′-Ca r boxylp h en yl)-1-(3,4-dih ydr oxy-5-n itr op h en yl)-
eth a n on e (27). To a stirred and cooled (-78 °C) solution of
diisopropylamine (1.8 g, 17.65 mmol) in anhydrous THF (10
mL) under nitrogen was added n-butyllithium (8.8 mL, 2 M
solution in hexanes, 17.6 mmol). After the mixture was stirred
for 30 min, o-toluic acid (0.6 g, 4.41 mmol) in THF (5 mL) was
added dropwise, and the resulting deep red solution was
stirred at -78 °C for 1 h. Thereupon, a solution of methyl
vanillate (0.84 g, 4.63 mmol) in THF (10 mL) was added
dropwise, and the temperature was gradually allowed to reach
room temperature. The mixture was then poured onto ice/2 N
HCl (350 mL) and extracted by diethyl ether (3 × 50 mL). The
organic extracts were washed by water (50 mL) and brine (50
mL), then dried over anhydrous sodium sulfate, filtered, and
evaporated (40 °C, water aspirator pressure). The residue was
recrystallized from 50% aqueous ethanol to afford white
crystals (0.83 g, 66%) of mp 166-168 °C.
2-(4′-Ch lor op h en yl)-1-(3,4-d ih yd r oxy-5-n it r op h en yl)-
eth a n on e (19). IR(KBr) 3374 (OH), 1671 (CdO), 1540 (NO2).
1H NMR (DMSO-d6) δ 10.9 (vbr, 2H, 3-OH, 4-OH), 8.09 (d,
1H, J ) 2.1 Hz, H-6), 7.61 (d, 1H, J ) 2.1 Hz, H-2), 7.38 (d,
2H, J ) 8.3 Hz, Ph), 7.26 (d, 2H, J ) 8.3 Hz, Ph), 4.37 (s, 2H,
CH2). 13C NMR (DMSO-d6) δ 195.8, 148.7, 146.8, 138.2, 135.1,
132.7, 132.3, 129.2, 127.6, 118.2, 117.5, 44.3.
1-(3,4-Dih yd r oxy-5-n itr op h en yl)-2-(2′-n a p h th yl)-eth a -
n on e (21). IR(KBr) 3383, 3260 (OH), 1684 (CdO), 1548 (NO2).
1H NMR (DMSO-d6) δ 10.8 (vbr, 2H, 3-OH, 4-OH), 8.14 (d,
1H, J ) 1.9 Hz, H-6), 8.0-7.7 (m, 4H, Ar), 7.65 (d, 1H, J ) 1.9
Hz, H-2), 7.55-7.3 (m, 3H, Ar), 4.51 (s, 2H, CH2). 13C NMR
(DMSO-d6) δ 196.2, 148.7, 146.9, 138.2, 134.0, 133.9, 132.8,
129.3, 129.1, 128.7, 128.5, 128.4, 127.7, 127.1, 126.7, 118.3,
117.6, 45.3.
2-(4′-Bip h en yl)-1-(3,4-d ih yd r oxy-5-n itr op h en yl)-eth a -
1
n on e (22). IR(KBr) 3380 (OH), 1674 (CdO), 1554 (NO2). H
Nitration (as described for 6b, n ) 1, 62%) and demethy-
lation (as described for 7b, 72%,) gave the title compound 27
as yellow crystals. IR(KBr) 3374 (OH), 2903, 2652 (CO2H,
NMR (DMSO-d6) δ 10.9 (vbr, 2H, 3-OH, 4-OH), 8.12 (d, 1H, J
) 2.1 Hz, H-6), 8.0-7.3 (m, 10H, H-2, Ar), 4.39 (s, 2H, CH2).
13C NMR (DMSO-d6) δ 196.1, 148.7, 146.9, 141.0, 139.5, 138.2,
135.3, 131.3, 129.9, 128.4, 127.6, 127.6, 118.4, 117.6, 44.8.
2-Cyloh e xyl-1-(3,4-d ih yd r oxy-5-n it r op h e n yl)-e t h a -
1
acid), 1686 (broad, CdO), 1543 (NO2). H NMR (DMSO-d6) δ
12.8 (vbr, 1H, COOH), 10.8 (vbr, 2H, 3-OH, 4-OH), 8.07 (d,
1H, J ) 2.1 Hz, H-6), 7.95 (d, 1H, Ar), 7.63 (d, 1H, J ) 2.1 Hz,
H-2), 7.6-7.3 (m, 3H, Ar), 4.68 (s, 2H, CH2). 13C NMR (DMSO-
d6) δ 195.7, 169.2, 148.6, 146.5, 138.2, 138.1, 133.8, 133.0,
131.5, 131.4, 128.3, 128.0, 118.2, 116.8, 45.0.
1
n on e (23). IR(KBr) 3361 (OH), 1669 (CdO), 1540 (NO2). H
NMR (CDCl3) δ 10.98 (br, 1H, 4-OH), 8.29 (d, 1H, J ) 2.1 Hz,
H-6), 7.85 (d, 1H, J ) 2.1 Hz, H-2), 6.02 (br, 1H, 3-OH), 2.81

694 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3
Learmonth et al.
3-(3,4-Dih ydr oxy-5-n itr oph en yl)-isoch r om en -1-on e (28).
A stirred suspension of 27 (0.3 g, 0.94 mmol) in acetic acid
(12 mL) was treated with concentrated sulfuric acid (3 drops)
and heated at 95 °C for 10 min and then allowed to cool to
room temperature. The mixture was poured onto ice-water
(30 mL), and the orange precipitate was filtered off and washed
by water (5 mL). Recrystallization from ethanol afforded
orange crystals (0.17 g, 61%) of mp 285-288 °C. (Anal. C, H,
7.50-7.30 (m, 5H, Ph), 2.5 (m, 2H, c-hexyl), 2.35 (s, 3H,
COCH3), 2.30 (s, 3H, COCH3), 1.8 (m, 2H, c-hexyl), 1.7 (m, 3H,
c-hexyl), 1.4 (m, 3H, c-hexyl). 13C NMR (CDCl3) δ 200.8, 168.0,
167.5, 144.3, 143.3, 142.5, 139.4, 136.0, 130.1, 129.7, 128.3,
126.7, 124.0, 56.2, 36.2, 26.2, 23.7, 21.0, 21.0.
2-Br om o-1-(3,4-d ia cetoxy-5-n itr op h en yl)-2-p h en yl-eth -
a n on e (33). To a stirred solution of 24 (0.36 g, 1 mmol) in dry
THF (5 mL) was added phenyltrimethylammonium tribromide
(0.45 g, 1.2 mmol) in one portion. After stirring at room
temperature for 45 min, the mixture was poured onto ice-
water (20 mL) and extracted by dichloromethane (3 × 30 mL).
The organic extracts were washed by water (30 mL) and brine
(30 mL), then dried over anhydrous sodium sulfate, filtered,
and evaporated (40 °C, water aspirator pressure). The residue
was chromatographed over silica gel (dichloromethane/petro-
leum ether, 2:1) and the major product obtained recrystallized
(diethyl ether) to give 33 as off-white crystals (0.67 g, 51%).
IR(KBr) 1786 (CdO, ester), 1703 (CdO, ketone), 1546 (NO2).
1H NMR (CDCl3) δ 8.58 (d, 1H, J ) 2.1 Hz, H-6), 8.15 (d, 1H,
J ) 2.1 Hz, H-2), 7.60-7.30 (m, 5H, Ph), 6.25 (s, 1H, CH),
2.41 (s, 3H, COCH3), 2.38 (s, 3H, COCH3). 13C NMR (CDCl3) δ
187.9, 168.0, 167.3, 145.4, 143.3, 141.4, 134.9, 132.3, 130.3,
129.9, 129.7, 129.7, 124.1, 50.3, 21.1, 21.0.
1
N). IR(KBr) 3226 (OH), 1701 (CdO, lactone), 1533 (NO2). H
NMR (DMSO-d6) δ 10.7 (vbr, 2H, 3-OH, 4-OH), 8.16 (d, 1H,
Ar), 7.9-7.8 (m, 2H, H-6, Ar), 7.71 (d, 1H, Ar), 7.65-7.5 (m,
2H, H-2, Ar), 7.46 (s, 1H, CH). 13C NMR (DMSO-d6) δ 162.1,
151.8, 149.2, 144.2, 138.7, 138.3, 136.5, 129.9, 129.6, 127.6,
123.1, 120.7, 116.1, 112.7, 102.7.
The following details are representative procedures for
synthesis of compounds 29-32.
1-(3,4-Diacetoxy-5-n itr oph en yl)-2-m eth yl-2-ph en yl-pr o-
p a n -1-on e (30). Sodium hydride (0.92 g, 55-65% mineral oil
dispersion) was washed with dry diethyl ether (6 mL) under
nitrogen and then covered by dry THF (10 mL). After cooling
to 0 °C, a solution of the ketone 5b (R ) Bn, n ) 1) (2 g, 6.02
mmol) in dry THF (50 mL) was added dropwise, and the
resulting suspension was allowed to stir for 45 min at room
temperature. The suspension was thereafter cooled again (0
°C), and a solution of methyl iodide (4.27 g, 30.12 mmol) in
dry THF (5 mL) was added dropwise. The resulting mixture
was stirred at 55 °C for 3 h and then quenched by careful
addition of cold water (10 mL). The solvent was removed (40
°C, water aspirator pressure) and the residue partitioned
between dichloromethane (50 mL) and water (50 mL). The
organic phase was separated, washed by water (10 mL) and
brine (10 mL), then dried over anhydrous sodium sulfate,
filtered, and dried. Evaporation (40 °C, water aspirator pres-
sure) afforded a pale yellow oil which was chromatographed
over silica gel (petroleum ether/ethyl acetate, 95:5) to afford
the dimethylated product as a clear oil (1.55 g, 71%). 1H NMR
(CDCl3) δ 7.4-7.25 (m, 10H, 2 x Ph), 7.21 (d, 1H, J ) 2.1 Hz,
H-2), 7.07(dd, 1H, J ) 2.1, 8.5 Hz, H-6), 6.67 (d, 1H, J ) 8.5
Hz, H-5), 5.13 (s, 2H, OCH2), 3.71 (s, 3H, OCH3), 1.62 (s, 6H,
2 × CH3). 13C NMR (CDCl3) δ 202.6, 151.7, 149.1, 146.7, 136.9,
129.5, 129.3, 129.2, 128.6, 127.7, 127.2, 126.2, 124.8, 113.6,
112.2, 71.2, 56.3, 51.8, 28.7.
P h a r m a cology. Male Wistar rats (Harlan-Interfauna Ibe´r-
ica, Barcelona, Spain) aged 60 days and weighing 240-260 g
were used in all experiments. Rats were kept under controlled
environmental conditions (12 h light/dark cycle and room
temperature 22 ( 1 °C) with food and tap water allowed ad
libitum. All test compounds were given by gastric tube (30 mg/
kg) in 0.5% carboxymethylcellulose to overnight fasted rats.
Thereafter, at defined intervals (0.5, 1, 3, 6, and 9 h), animals
were sacrificed and tissues removed to determine COMT
activity. Rats were anaesthetised with sodium pentobarbital
(60 mg/kg) and perfused through the left ventricle with 0.9%
(w/v) NaCl. Livers and brains were immediately removed and
homogenized in 5 mM sodium phosphate buffer, pH 7.8 at 4
°C with a Teflon homogenizer (Heidolph). The crude homoge-
nates were directly used for the COMT assay. The protein
content in the homogenates was determined by the method of
Bradford35 with human serum albumin as standard.
COMT activity was determined by the ability of enzyme
preparations to methylate adrenaline to metanephrine as
previously described.36 Briefly, aliquots of 0.5 mL of liver or
brain homogenates were preincubated for 20 min with 0.4 mL
of phosphate buffer in the presence of a saturating concentra-
tion of S-adenosyl-L-methionine, the methyl donor (500 µM and
100 µM for liver and brain, respectively). The incubation
medium contained also pargyline (100 µM), MgCl2 (100 µM),
and EGTA (1 mM). The reaction mixture was incubated with
a saturating concentration of adrenaline (1000 µM and 100
µM for liver and brain, respectively). The preincubation and
incubation were carried out at 37 °C under conditions of light
protection with continuous shaking. At the end of the incuba-
tion period (5 and 15 min for liver and brain, respectively),
the tubes were transferred to ice, and the reaction was stopped
by the addition of 200 µL of 2 M perchloric acid. The samples
were then centrifuged (200 g, 4 min, 4 °C), and 500 µL aliquots
of the supernatant, filtered on 0.22 µm pore size Spin-X filter
tubes (Costar), were used for the assay of metanephrine by
means of HPLC-ED, as previously described.36 In brief, ali-
quots of 50 µL of the filtered supernatant were injected into
the chromatograph. The chromatography system consisted of
a pump (Gilson model 302; Gilson Medical Electronics, Villiers
le Bel, France) connected to a manometric module (Gilson
model 802 C) and a stainless steel 5 µm ODS column
(Biophase; Bioanalytical Systems, West Lafayette, IN) of 25
cm length. Samples were injected by means of an automatic
sample injector (Gilson model 231) connected to a Gilson
dilutor (model 401). The mobile phase was a degassed solution
of citric acid (0.1 mM), sodium octylsulfate (0.5 mM), sodium
acetate (0.1 M), EDTA (0.17 mM), dibutylamine (1 mM), and
methanol (10% v/v), adjusted to pH 3.5 with perchloric acid (2
M) and pumped at a rate of 1.0 mL/min. The detection was
carried out electrochemically with a glassy carbon electrode,
Subsequent debenzylation (91%), nitration (69%), demethy-
lation (93%), and acetylation (95%) using procedures described
above gave 30 as off-white crystals. IR(KBr) 1775 (CdO, ester),
1
1684 (CdO, ketone), 1545 (NO2). H NMR (CDCl3) δ 8.04 (d,
1H, J ) 2.1 Hz, H-6), 7.70 (d, 1H, J ) 2.1 Hz, H-2), 7.50-7.30
(m, 5H, Ph), 2.35 (s, 3H, COCH3), 2.30 (s, 3H, COCH3), 1.65
(s, 6H, 2 × CH3). 13C NMR (CDCl3) δ 199.7, 168.0, 167.5, 144.5,
144.2, 142.6, 139.8, 134.1, 130.5, 130.1, 128.2, 126.1, 124.9,
52.2, 28.0, 21.0, 21.0.
By application of similar procedures the following were
obtained:
1-(3,4-Dia cet oxy-5-n it r op h en yl)-2-p h en yl-p r op a n -1-
on e (29). IR(KBr) 1780 (CdO, ester), 1690 (CdO, ketone),
1
1548 (NO2). H NMR (CDCl3) δ 8.54 (d, 1H, J ) 2.1 Hz, H-6),
8.08 (d, 1H, J ) 2.1 Hz, H-2), 7.40-7.20 (m, 5H, Ph), 4.61 (q,
1H, J ) 6.8 Hz, CH), 2.38 (s, 3H, COCH3), 2.36 (s, 3H, COCH3),
1.57 (d, 3H, CH3). 13C NMR (CDCl3) δ 196.5, 167.9, 167.2,
144.9, 142.9, 140.5, 140.3, 134.5, 129.9, 129.1, 128.1, 128.0,
123.7, 48.8, 20.9, 20.8, 19.7.
1-(3,4-Dia cetoxy-5-n itr op h en yl)-2,3-d ip h en yl-p r op a n -
1-on e (31). IR(KBr) 1782 (CdO, ester), 1686 (CdO, ketone),
1
1544 (NO2). H NMR (CDCl3) δ 8.47 (d, 1H, J ) 2.1 Hz, H-6),
8.03 (d, 1H, J ) 2.1 Hz, H-2), 7.40-7.00 (m, 10H, 2 × Ph),
4.72 (t, 1H, J ) 7.2 Hz, CH), 3.56 (dd, 1H, J ) 7.5, 13.7 Hz,
CH2), 3.09 (dd, 1H, J ) 6.8, 13.7 Hz, CH2), 2.36 (s, 3H, COCH3),
2.34 (s, 3H, COCH3). 13C NMR (CDCl3) δ 195.6, 168.0, 167.3,
145.1, 143.1, 140.7, 139.5, 138.1, 134.8, 130.0, 129.7, 129.1,
129.0, 128.7, 128.4, 127.0, 123.7, 57.0, 40.5, 21.1, 21.0.
(3,4-Dia cet oxy-5-n it r op h en yl)-1-(p h en yl-cycloh exyl)-
m eth a n on e (32). IR(KBr) 2943 (aliphatic CH), 1780 (CdO,
ester), 1679 (CdO, ketone), 1540 (NO2). 1H NMR (CDCl3) δ
7.93 (d, 1H, J ) 2.1 Hz, H-6), 7.54 (d, 1H, J ) 2.1 Hz, H-2),

Synthesis of Catechol-O-methyltransferase Inhibitors
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3 695
(15) Messiha, F.; Hsu, T.; Bianchine, J . Peripheral aromatic L-amino
acid decarboxylase inhibitor in parkinsonism. I. Effect on
O-methylated metabolites of L-Dopa-2-14C. J . Clin. Invest. 1972,
51, 452-455.
an Ag/AgCl reference electrode, and an amperometric detector
(Gilson model 141); the detector cell was operated at 0.75 V.
The current produced was monitored using the Gilson 712
HPLC software. The lower limits for detection of metanephrine
ranged from 350 to 500 fmol.
(16) Mannisto, P. T.; Ulmanen, I.; Lundstrom, K.; Taskinen, J .;
Tenhunen, J .; Tilgmann, C., Kaakkola, S. Characteristics of
catechol-O-methyltransferase (COMT) and properties of selective
COMT inhibitors. Prog. Drug Res. 1992, 39, 291-350.
(17) Tohgi, H.; Abe, T.; Kikuchi, T.; Takahashi, S.; Nozaki, Y. The
significance of 3-O-methyldopa concentrations in the cerebrospi-
nal fluid in the pathogenesis of wearing-off phenomenon in
Parkinson’s disease. Neurosci. Lett. 1991, 132, 19-22.
(18) Ericsson A. D. Potentiation of the L-Dopa effect in man by the
use of catechol-O-methyltransferase inhibitors. J . Neurol. Sci.
1971, 14, 193-197.
(19) Borgulya, J .; Bruderer, H.; Bernauer, K.; Zurcher, G.; Da Prada,
M. Catechol-O-methyltransferase-inhibiting pyrocatechol deriva-
tives: synthesis and structure-activity studies. Helv. Chim.
Acta. 1989, 72, 952-968.
(20) Backstrom, R.; Honkanen, E.; Pippuri, A.; Kairisalo, P.; Py-
stynen, J .; Heinola, K.; Nissinen, E.; Linde´n, I.-B.; Mannisto, P.
T.; Kaakkola, S.; Pohto, P. Synthesis of some novel potent and
selective catechol-O-methyltransferase inhibitors. J . Med. Chem.
1989, 32, 841-846.
(21) Perez, R. A.; Fernandez-Alvarez, E.; Nieto, O.; Piedrafita, F. J .
Dihydroxynitrobenzaldehydes and hydroxymethoxynitrobenzal-
dehydes: synthesis and biological activity as catechol-O-meth-
yltransferase inhibitors. J . Med. Chem. 1992, 35, 4584-4588.
(22) Borgulya, J .; Da Prada, M.; Dingemanse, J .; Scherschlicht, R.;
Schlappi, B.; Zurcher, G. Ro 40-7592. Catechol-O-methyltrans-
ferase (COMT) inhibitor. Drugs Future 1991, 16, 719-721.
(23) Nissinen, E.; Linde´n, I.-B.; Schultz, E.; Pohto, P. Biochemical
and pharmacological properties of a peripherally acting catechol-
O-methyltransferase inhibitor Entacapone. Nauyn Schmiede-
bergs Arch. Pharmacol. 1992, 346, 262-266.
(24) Assal, F.; Spahr, L.; Hadengue, A.; Rubbici-Brandt, L.; Burkhard,
P. R. Tolcapone and fulminant hepaptitis. Lancet 1998, 352, 958.
(25) Bonifati, V.; Meco, G. New, selective catechol-O-methyltrans-
ferase inhibitors as therapeutic agents in Parkinson’s disease.
Pharmacol. Ther. 1999, 81, 1-36.
(26) Colissimo, C. The rise and fall of tolcapone. J . Neurol. 1999, 246,
880-882.
SK-N-SH cells, a human neuroblastome derived cell line,
were obtained from the American Type Culture Collection
(ATTC HTB-11). The SK-N-SH cell line expresses high levels
of COMT activity with similar kinetics parameters to rat brain
COMT and is considered to be an appropriate in vitro model
for the assay of human COMT.37 SK-N-SH cells were main-
tained in a humidified atmosphere of 5% CO2-95% air at 37
°C. The cells were grown in Minimal Essential Medium
supplemented with 10% foetal bovine serum, 100 U/mL
penicillin G, 0.25 µg/mL amphotericin B, 100 µg/mL strepto-
mycin, and 25 mM HEPES. For the assays, the cells were
plated in 24-well plates, and 24 h prior to each experiment
the medium was changed to medium free of foetal bovine
serum. Experiments were generally performed after cells
reached confluence (5-7 days), and each cm2 contained about
100 µg of cell protein. COMT activity was evaluated in cell
monolayers by the ability to methylate adrenaline to meta-
nephrine in the presence of saturating concentration (100 µM)
of the methyl donor (S-adenosyl-L-methionine). The incubation
medium also contained 100 µM pargyline, 100 µM MgCl2, and
1 mM EGTA. The preincubation (20 min) and incubation (15
min) were carried out at 37 °C, in the dark, with continuous
shaking and without oxygenation. At the end of the incubation
period, the plates were transferred to ice and the reaction was
stopped by the addition of 2 M perchloric acid. The assay of
metanephrine was performed by means of HPLC-ED, as
described above.
Refer en ces
(1) Axelrod, J .; Senoh, S.; Witkop, B. O-Methylation of catechol
amines in vivo. J . Biol. Chem. 1958, 233, 697-701.
(2) Axelrod, J .; Tomchick, R. Enzymatic O-methylation of epineph-
rine and other catechols. J . Biol. Chem. 1958, 233, 702-705.
(3) Guldberg, H.; Marsden, C. Catechol-O-methyltransferase: phar-
macological aspects and physiological role. Pharmacol. Rev.
1975, 27, 135-206.
(4) Creveling, C.; Dalgard, N.; Shimizu, H.; Daly, J . Catechol-O-
methyltransferase III. M- and p-O-methylation of catechola-
mines and their metabolites. Mol. Pharmacol. 1970, 6, 691-
696.
(5) Zhu, B. T.; Ezell, E. L.; Liehr, J . G. Catechol-O-methyltrans-
ferase-catalysed rapid O-methylation of mutagenic flavanoids.
Metabolic inactivation as a possible reason for their lack of
carcinogenicity in vitro. J . Biol. Chem. 1994, 269, 292-299.
(6) Borcharrdt, R. T.; Thakker, D. R. Affinity labeling of catechol-
O-methyltransferase by N-haloacetyl derivatives of 3,5-dimeth-
oxy-4-hydroxyphenylethylamine and 3,4-dimethoxy-5-hydroxy-
phenylethylamine. Kinetics of inactivation. Biochemistry 1975,
14, 4542-4551.
(7) Burba, J . V.; Becking, G. C. Effect of the antioxidant norhy-
droguaiaretic acid on the in vitro activity of catechol-O-meth-
yltransferase. Arch. Int. Pharmacodyn. Ther. 1969, 180, 323-
329.
(27) Hauser, R. A.; Molho, E.; Shale, H.; Pedder, S.; Dorflinger, E.
E. A pilot evaluation of the tolerability, safety and efficacy of
tolcapone alone and in combination with oral selegiline in
untreated Parkinson’s disease patients. Mov. Disord. 1998, 13,
643-647.
(28) Nutt, J . G. Catechol-O-methyltransferase inhibitors for treat-
ment of Parkinson’s disease. Lancet 1998, 351, 1221-1222.
(29) Dingemanse, J .; J orga, K.; Schmitt, M.; Gieschke, R.; Fotteler,
B.; Zurcher, G.; Da Prada, M.; van Brummelen, P. Integrated
pharmacokinetics and pharmacodynamics of the novel catechol-
O-methyltransferase inhibitor tolcapone during first administra-
tion to humans. Clin. Pharmacol. Ther. 1995, 57, 508-517.
(30) Keranen, T.; Gordin, A.; Harjola, V.-P.; Karlsson, M.; Korpela,
K.; Pentikainen, P. J .; Rita, H.; Seppala, L.; Wikberg, T.
Inhibition of soluble catechol-O-methyltransferase and single-
dose pharmacokinetics after oral and intravenous administration
of entacapone. Eur. J . Clin. Pharmacol. 1994, 46, 151-157.
(31) Learmonth, D. A.; Alves, P. C. Improved method for the
demethylation of nitro-catechol methyl ethers. Synth. Commun.
In press.
(32) Devi, N.; J ain, N.; Krishnamurty, H. G. Synthesis of deoxyben-
zoins. Indian J . Chem. Sect. B. 1993, 32B (8), 874-875.
(33) Wahala, K.; Hase, T. A. Expedient synthesis of polyhydroxy-
isoflavones. J . Chem. Soc., Perkin Trans. 1 1991, 3005-3008.
(34) Guion, T. S.; Koller, M. U.; Lachicotte, R. J .; Rutledge, R. N.;
Hildebran, K. C.; Le, P. H.; Beam, C. F. The preparation of 2-(2-
oxo-2-phenylethyl)benzoic acids from dilithiated ortho-toluic
acid. Synth. Commun. 1996, 26 (9), 1753-1762.
(35) Bradford, M. M. A rapid method for the quantification of
microgram quantities of protein utilizing the principle of protein-
dye binding. Anal. Biochem. 1976, 72, 248-254.
(36) Borges, N.; Vieira-Coelho, M. A.; Parada, A.; Soares-da-Silva,
P. Studies on the tight-binding nature of tolcapone inhibition of
soluble and membrane-bound rat brain catechol-O-methyltrans-
ferase. J . Pharmacol. Exp. Ther. 1997, 282, 812-817.
(37) Costa, J . L.; Vieira-Coelho, M. A.; Soares-da-Silva, P. Catechol-
O-methyltransferase activity in SK-N-SH cells. Eur. J . Neu-
rosci. 2000, 12 (suppl. 11), 280.
(8) Mannisto, P. T.; Kaakkola, S. New selective COMT inhibitors:
Useful adjuncts for Parkinson’s disease? Trends Pharmacol. Sci.
1989, 10, 54-56.
(9) Mannisto P. T.; Kaakkola, S. Rationale for selective COMT
inhibitors as adjuncts in the drug treatment of Parkinson’s
disease. Pharmacol. Toxicol. 1990, 66, 317-323.
(10) Cotzias, G. C.; Papavasiliou, P. S.; Ginos, J .; Steck, A.; Duby, S.
Aromatic amino acids and modification of parkinsonism. N. Engl.
J . Med. 1967, 276, 374-379.
(11) Calne, D. B. Treatment of Parkinson’s disease. N. Engl. J . Med.
1993, 329, 1021-1027.
(12) Diamond, S. G.; Markham, C. H.; Treciokas, L. J . A double-blind
comparison of levodopa, Madopar and Sinemet in Parkinson’s
disease. Ann. Neurol. 1978, 3, 267-272.
(13) Bartholini, G.; Pletscher, A. Decarboxylase inhibitors. Pharma-
col. Ther. 1975, 1, 407-421.
(14) Nutt, J . G.; Woodward, W. R.; Anderson, J . L. The effect of
carbidopa on the pharmacokinetics of intavenously administered
levodopa: the mechanism of action in the treatment of parkin-
sonism. Ann. Neurol. 1985, 18, 537-543.
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