New antipsychotic agents with serotonin and dopamine antagonist properties based on a pyrrolo[2,1-b][1,3]benzothiazepine structure

Article abstract of DOI:10.1021/jm9706832

The development of a synthetic approach to the novel pyrrolo[2,1- b][1,3]benzothiazepine and its derivatives and their biological evaluation as potential antipsychotic drugs are described. In binding studies these compounds proved to be potent 5-HT_2<

Full text of DOI:10.1021/jm9706832

J . Med. Chem. 1998, 41, 3763-3772
3763
Articles
New An tip sych otic Agen ts w ith Ser oton in a n d Dop a m in e An ta gon ist P r op er ties
Ba sed on a P yr r olo[2,1-b][1,3]ben zoth ia zep in e Str u ctu r e
Giuseppe Campiani,† Vito Nacci,*,† Susanna Bechelli,† Silvia M. Ciani,† Antonio Garofalo,† Isabella Fiorini,†
Håkan Wikstro¨m,§ Peter de Boer,§ Yi Liao,§ Pieter G. Tepper,§ Alfredo Cagnotto,‡ and Tiziana Mennini‡
Dipartimento Farmaco Chimico Tecnologico, Universita’ di Siena, Banchi di Sotto, 55, 53100 Siena, Italy,
Department of Medicinal Chemistry, UCF, University of Groningen, Antonius Deusinglaan, 1, NL-9713 AV Groningen,
The Netherlands, and Istituto di Ricerche Farmacologiche “Mario Negri”, via Eritrea 62, 20157 Milano, Italy
Received October 8, 1997
The development of a synthetic approach to the novel pyrrolo[2,1-b][1,3]benzothiazepine and
its derivatives and their biological evaluation as potential antipsychotic drugs are described.
In binding studies these compounds proved to be potent 5-HT2, D2, and D3 receptor ligands.
The more potent benzothiazepine (()-3b was resolved into its enantiomers by using HPLC
techniques. In vitro testing confirmed that (-)-3b is a more potent D2 receptor ligand,
maintaining high affinity for 5-HT2 receptors. In contrast, the (+)-3b enantiomer presents a
35 times higher affinity for 5-HT2 than for dopamine D2 receptors with a similar dopamine D1
receptor affinity to that of (-)-3b. Overall, (+)-3b shows an “atypical” neuroleptic binding
profile, while (-)-3b has a more “classical” profile. Furthermore pharmacological and
biochemical testing displayed that the novel benzothiazepine (()-3b is able to increase the
extracellular levels of dopamine in the rat striatum and causes a dose-related suppression of
apomorphine-induced locomotor activity. At low doses (()-3b does not induce catalepsy,
showing atypical antipsychotic properties similar to those of olanzapine. These heterocyclic
compouds represent new leads for the development of novel antipsychotic drugs with atypical
properties.
Ch a r t 1
In tr od u ction
The involvement of dopamine (DA) and dopaminergic
neurons in the pathology of a number of psychiatric and
neurological disorders has been well-documented,1 and
consequently there is considerable interest in the de-
velopment of potent DA receptor agonists and antago-
nists. For schizophrenia, a devastating mental disorder,
a dopamine hypothesis2 has been formulated stating
that the classical neuroleptic drugs alleviate the positive
symptoms of the disease by blocking the dopamine
neurotransmission in certain brain areas. For decades,
neuroleptic drugs have been established as the treat-
ment of choice for acute and chronic schizophrenia.
Chlorpromazine and haloperidol are representative of
these classical (typical) antipsychotics. More recently,
several clinical studies have demostrated that 5-HT2
antagonists could improve the negative symptoms of
schizophrenia, and coadministration of 5-HT2 antago-
nists to “typical” antipsychotics reduced the incidence
of extrapyramidal symptoms compared to treatment
with neuroleptics alone.3,4 The first antipsychotic to
show a remarkably different clinical profile was cloza-
pine (1) (Chart 1), a drug that antagonizes dopamine
at D2 receptors and serotonin at 5-HT2 receptors. The
intriguing profile of this compound has been called
“atypical”, and now clozapine represents the standard
neuroleptic to which the new antipsychotic agents are
compared.5 Clinical experience suggests that clozapine
is more effective than classical neuroleptic drugs in the
* To whom correspondence should be addressed.
† Universita’ di Siena.
§ University of Groningen.
‡ Istituto di Ricerche Farmacologiche “Mario Negri”.
S0022-2623(97)00683-3 CCC: $15.00 © 1998 American Chemical Society
Published on Web 09/04/1998

3764 J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 20
Campiani et al.
Ch a r t 2. Retrosynthetic Analyses of Compound 9a
Based on an Intramolecular Nucleophilic Displacement
of an Aromatic Fluorine Atom and on an Intramolecular
Acylation
Sch em e 1
In this work we present the synthesis, the resolution,
and the pharmacological characterization of potential
antipsychotic agents (3) with clozapine- and olanzapine-
like properties, based on the novel pyrrolo[2,1-b][1,3]-
benzothiazepine skeleton. The common features with
other tricyclic antipsychotic drugs, such as octoclothep-
ine, clozapine, and olanzapine (4), are the butterfly-like
conformation of the lipophilic tricyclic system and the
presence of the basic side chain.
treatment of schizophrenic patients with positive and
negative symptoms. Clozapine does not produce ex-
trapyramidal motor disturbances (EPS), it does not
elevate prolactin serum levels, and it has no cataleptic
potential. Its “atypical” antipsychotic profile has been
explained on the basis of the dopamine/serotonin hy-
pothesis:3 it has been proposed that the blockade of D2
and 5-HT2 receptors, together with the enhancement of
dopamine and serotonin release in cortical regions, is a
critical element in the action of clozapine. Unfortu-
nately, the occurrence of agranulocytosis in a few
percentage of patients during treatment with clozapine
has limited its therapeutic usefulness.6 (S)-Octoclothep-
ine (2) and (1S,3R)-tefludazine are neuroleptic drugs
with potent antagonist activity on D2 receptors (higher
than that of clozapine) and high affinity for 5-HT2
receptors. These two compounds have been used to
define the spatial relationships of the pharmacophore
elements through the superimposition of their active
conformations, and these spatial relationships represent
a new D2 receptor interaction model (an aromatic ring,
an ionizable nitrogen, and a dummy atom at 2.8 Å from
N in the direction of its lone pair).7a,b Clozapine
matches this model,8 although the carbon atom contain-
ing chlorine is part of the 5-HT2 pharmacophore pro-
posed by Andersen in 1994.9 The biochemical and
behavioral activity of the two enantiomers of octo-
clothepine have recently been reinvestigated,7b and
while the (S)-enantiomer was found to possess a clas-
sical neuroleptic profile, the (R)-enantiomer showed a
more “atypical” profile. This fact prompted us to develop
a project aimed at identifying novel antipsychotic
compounds based on a tricyclic skeleton and related to
octoclothepine. In particular, the structure of octo-
clothepine was modified by replacing a benzo-fused ring
with a pyrrole, in an attempt to improve its pharma-
cological profile.
Ch em istr y
The synthesis of the novel pyrrolo[2,1-b][1,3]benzo-
thiazepine skeleton has been attempted following three
retrosynthetic approaches described in Charts 2 and 3
and in Schemes 1-4. The main task to be accomplished
in this synthesis is the discovery of a cyclization method
to obtain the pyrrolobenzothiazepinone intermediates
9a ,b . Chart 2 reports our retrosynthetic analyses of
compound 9a based on the nucleophilic displacement
of an aromatic fluorine atom10 and on an intramolecular
acylation.11a,b In the first attempt the 2-(fluorophenyl)-
ethanone could be transformed in the thiocyanatopyr-
role derivative, the thioenolate of which could displace
the fluorine atom, leading to 9a . As shown in Scheme
1, after bromination and Delepine reaction12 (6), fol-
lowed by Clauson-Kaas reaction,13 the 2-fluoroac-
etophenone 5 was transformed into the pyrrole deriva-
tive 7. This compound was then treated with cupric
thiocyanate14 to give the 2-thiocyanatopyrrole 8, and the
latter, after exposure to sodium methoxide or potassium
tert-butoxide,14 did not provide the expected tricyclic
compound 9a , but the “anomalous” novel bicyclic pyr-
rolo[2,1-b]thiazole derivative 10, resulting from attack
at the thiocyanato group by the strong nucleophile
generated in situ by removal of hydrogen from the
R-position to the keto group of 8.
Following a different strategy (Scheme 2), when
pyrrole was treated with cupric thiocyanate in metha-

New Antipsychotics Based on Pyrrolobenzothiazepine
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 20 3765
Sch em e 2
Ch a r t 3. Retrosynthetic Analysis of Compound 9a
Based on a Thionium Ion Intermediate
the interaction of methyllithium and the lithium salt
of 2-(methylthio)benzoic acid (17), or from 1-chloro-4-
(methylthio)benzene (19), by a Friedel-Crafts reaction
with acetic anhydride, respectively (Scheme 3).
Subsequently, the bromophenylethanones 21a ,b were
transformed into the pyrrole derivatives 22a ,b by using
the methodology described for compoud 7. Oxidation
with sodium periodate (23a ,b) followed by exposure of
these sulfoxides to trifluoroacetic anhydride provided
the ketones 9a ,b in 40% yield (Scheme 4).16
nol, thiocyanation took place in a few minutes obtaining
the 2-thiocyanatopyrrole 11 in good yield.15a Grignard
reaction with phenylmagnesium bromide (12)15b fol-
lowed by alkylation with ethyl bromoacetate provided
the ester 13 in high overall yield. Saponification gave
the acid 14, and although different cyclization protocols
were attempted (Friedel-Crafts reactions or PPA/PPE-
promoted cyclizations), it was impossible to obtain the
desired compound 9a . On the contrary, the ester 13
could serve as starting material to attempt another
cyclization method to 9a , based on a copper(I)-promoted
acylation reaction. In fact, dimethylaluminum meth-
ylselenolate was used to obtain the acyl-transfer agent
15.11a This selenoester can, in analogy to thioesters, be
used in a carbon-carbon bond-forming reaction. Ac-
cordingly, by exposure of 15 to the highly reactive
crystalline complex of copper(I) triflate and benzene
[(CuOTf)2PhH], the tricyclic 9a in 12% yield11b was
obtained together with the ketone 16 (55% yield) and
other unidentified byproducts.
The low yield and the difficulties found in handling
the highly reactive copper reagent prompted us to
develop another synthetic route to 9a ,b. In Chart 3 is
described the synthetic approach to 9a based on a
thionium ion intermediate.16 Accordingly, the key
tricyclic intermediates 9a ,b could be prepared under
Pummerer rearrangement conditions, starting from
sulfoxides, in turn prepared from 1-[2-(methylthio)-
phenyl]ethanones. The key intermediates 21a ,b17a were
prepared starting by bromination17b of the correspond-
ing phenylethanones 1818 and 20, in turn prepared by
The proposed mechanism of the cyclization step is
reported in eq 1. The “interrupted” Pummerer rear-
rangement begins with the activation of the sulfoxide
oxygen followed by the attack of the pyrrole ring on
sulfur displacing the trifluoroacetate ion. Then the
sulfonium salt undergoes displacement of the methyl
group generating the novel heterocyclic system and
methyl trifluoroacetate. Starting from ketones 9a ,b the
piperazine ring was introduced following a standard
method.19 Accordingly, reduction of ketones 9a ,b pro-
vided the alcohols (()-24a ,b which were transformed
into the bromo derivatives (()-25a ,b by means of PBr3.
By treatment of (()-25a ,b with N-methylpiperazine, the
final products (()-3a ,b were obtained. The thiazepine
(()-3b was resolved by HPLC into the enantiomers (+)-
3b and (-)-3b using a Chiralpak AD Amylose column.
Resu lts a n d Discu ssion
P h a r m a cologica l Stu d ies. The binding affinities
for 5-HT2, D1, D2, and D3 receptors and the comparison

3766 J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 20
Campiani et al.
Sch em e 3
Sch em e 4
of pKi’s of (()-3a ,b, (+)-3b, (-)-3b, clozapine, olanzap-
ine, tested in the same experimental conditions, and
methiothepine are shown in Tables 1 and 2, while Table
3 summarizes the effect of (()-3b on apomorphine-
induced locomotor hyperactivity (APO-induced LMA)
and catalepsy, compared to the effects of olanzapine, an
“atypical” antipsychotic. Figures 1 and 2 display the
ability of (()-3b, compared to olanzapine, to increase
the release of dopamine and DOPAC from the rat brain
striatum.
1. Bin d in g Assa ys. Binding studies performed on
(()-3a ,b show that a chlorine atom is critical for the
potency of binding to serotonin and dopamine receptors.
The chloro-substituted compound (()-3b displays a
higher affinity for 5-HT2, D2, and D3 receptors than (()-
3a and a weak affinity for D1 receptors (autoradiography
results for D4 receptors for compounds 3a ,b were
negative, see the Experimental Section20). Furthermore
(()-3b shows a low affinity for the dopamine uptake
site, with an IC50 of 6500 nM. Compound (()-3b, the
most active at D2 and 5-HT2 receptors, has been
resolved, and the two enantiomers show a different
binding profile (Table 1). Despite (+)- and (-)-octo-
clothepine that present a similar binding profile at
5-HT2 and D2 receptors, with (-)-octoclothepine being
5 times less potent at the D2 receptor,7b the (+)-
enantiomer of 3b is 25 times less potent at the D2
receptor than the (-)-enantiomer, confirming a rather
stereoselective interaction of 3b enantiomers at the D2
receptor. At D1 and 5-HT2 receptors we find that the
enantiomers have almost identical affinity, (+)-3b being
slightly more potent than (-)-3b.
Ta ble 1. Binding Affinities for 5-HT2, D1, D2, and D3
Receptors of Compounds (()-3a ,b, (+)-3b, and (-)-3b
Ki (nM)a ((SEM)
compd
5-HT2
D1
D2
D3
(()-3a
7.85 ( 2.2
160 ( 77
70 ( 17
57 ( 6.2
4.1 ( 1.5
(()-3b
1.14 ( 0.12 27 ( 10
3.8 ( 0.5
(+)-3b
(-)-3b
clozapine
olanzapine
methysergide 5.3 ( 0.8
(-)-cis-
flupentixol
1.48 ( 0.2
16.4 ( 1.0 49.6 ( 6.0 NTb
1.72 ( 0.25 22.0 ( 1.3 2.06 ( 0.2 NTb
11.0 ( 1
12.0 ( 1
353 ( 35
85 ( 3.5
250 ( 57
69 (17
NTb
NTb
37.8 ( 1.7
sulpiride
dopamine
240 ( 58
11 ( 3.4
a
Each value is the mean ( SEM of three determinations and
represents the concentration giving half-maximal inhibition of
[3H]ketanserin (5-HT2), [3H]SCH 23390 (D1), [3H]spiperone (D2),
and [3H]-7-OH-DPAT (D3) binding to rat tissue homogenate. NT,
b
not tested.
ratios of typical and atypical antipsychotics, such as
methiothepine and clozapine and olanzapine, respec-
tively, are compared to those of compounds (()-3a ,b,
(+)-3b, and (-)-3b. Accordingly, from the comparison
of the pKi data and of the log Y score3 of (()-3a ,b, (+)-
3b, and (-)-3b with those of reference compounds, we
could predict (i) an atypical profile for compound (()-
3a (log Y ) 4.98), which resembles the binding charac-
Classification of atypical and typical antipsychotic
drugs could be done on the basis of D1, D2, and 5-HT2
pKi values. According to this hypothesis3 the neurolep-
tics with a 5-HT2 versus D2 affinity ratio (pKi values)
greater than 1 would have the possibility to show
atypical antipsychotic properties. In Table 2 the affinity

New Antipsychotics Based on Pyrrolobenzothiazepine
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 20 3767
Ta ble 2. pKi Values of D1, D2, and 5-HT2 Receptor Binding
Sites, Ratios for Compounds (()-3a ,b, (+)-3b, and (-)-3b,
Clozapine (Atypical), Olanzapine (Atypical), and Methiothepine
(Typical), and Their Log Y Scores
5-HT2/ 5-HT2/ log Ya
compd
D1 D2 5-HT2 D1/D2
D1
D2
score
(()-3a
6.8 7.15
7.6 8.4
7.8 7.3
7.7 8.7
7.1 7.2
6.5 6.6
8.1
8.9
8.8
8.7
7.9
7.9
9.4
0.95
0.90
1.06
0.88
0.98
0.98
0.90
1.19
1.18
1.13
1.14
1.11
1.23
1.08
1.13
1.06
1.20
1.00
1.10
1.20
0.97
4.98
6.50
4.65
7.42
5.55
4.00
8.95
(()-3b
(+)-3b
(-)-3b
olanzapine
clozapine
methiothepineb 8.7 9.7
a
Log Y score has been calculated according to the equation
b
reported in ref 22. Cutoff point 6.48. Data from ref 22.
Ta ble 3. Effect of Compound (()-3b‚2HCl and Olanzapine on
APO-Induced LMA and Catalepsy
F igu r e 2. Effect of olanzapine (4) and compound (()-3b on
extracellular levels of DOPAC in striatum expressed as
percentages of control values. All data are means ( SEM (n
) 3). Drug administration (sc) is indicated by an arrow.
dose
compd
(µmol/kg, sc)
LMA
catalepsy
control
2263 ( 157
877 ( 43
40 ( 5
43 ( 3
39 ( 3
323 ( 42
ND
0/4
0/4
0/4
1/4
4/4
0/4
ND
0/4
0/4
(()-3b‚2HCla
1
3
administration of 3 µmol/kg (()-3b. At these doses, (()-
3b did not induce catalepsy. However, after adminis-
tration of 10 and 30 µmol/kg (()-3b, catalepsy was
observed in 1/4 and 4/4 rats, respectively. Like for (()-
3b, administration of olanzapine caused a dose-related
suppression in apomorphine-induced locomotor activity
[F(3,17) ) 14.681, p < 0.001; n ) 4-5]. Locomotor
activity was suppressed to 14% of control values after
administration of 1 µmol/kg olanzapine. In contrast to
(()-3b, olanzapine did not induce catalepsy up to doses
of 30 µmol/kg, although at this dose the animals had
lower muscle tone (Table 3). Administration of 30 nmol/
kg (()-3b elevated extracellular dopamine levels in rat
striatum to maximally 140% of control values [F(10,-
32) ) 4.066, p ) 0.003; n ) 3] (Figures 1 and 2). A
smaller, but also significant, increase in extracellular
levels of DOPAC to 122% of control levels was observed
after administration of (()-3b [F(10,32) ) 7.962, p <
0.001; n ) 3]. Administration of 1 µmol/kg (()-3b
further increased extracellular dopamine levels to 180%
of control values [F(10,32) ) 2.345, p ) 0.046; n ) 3]
and DOPAC levels to 270% of control values [F(10,32)
) 30.439, p < 0.001; n ) 3]. The onset of the effect was
about 30 min after administration.
10
30
1
olanzapine
3
10
30
47 ( 3
4 ( 2
a
Compound (()-3b has been tested as the dihydrochloride salt
(see the Experimental Section). All decreases are significantly
different from control values. ND, not determined.
Administration of doses g 10 nmol/kg olanzapine also
increased extracellular levels of dopamine in striatum.
After administration of 10 nmol/kg olanzapine, dopam-
ine levels increased to 200% of control values and
returned to baseline levels in about 2 h [F(10,32) )
2.375, p ) 0.044; n ) 3]. DOPAC levels remained
unchanged after administration of 10 nmol/kg olanza-
pine [F(10,32) ) 1.003, p ) 0.471; n ) 3]. A more
profound effect on striatal biochemistry was observed
after administration of 1 µmol/kg olanzapine. Both
extracellular levels of dopamine [F(10,32) ) 7.744, p <
0.001; n ) 3] and DOPAC [F(10,32) ) 2.893, p ) 0.018;
n ) 3] increased to about 200% of control values. As
with (()-3b, the onset of the effect was about 30 min
after administration.
F igu r e 1. Effect of olanzapine (4) and compound (()-3b on
extracellular levels of dopamine in striatum expressed as
percentages of control values. All data are means ( SEM (n
) 3). Drug administration (sc) is indicated by an arrow.
teristics of clozapine, and (ii) olanzapine-like properties
for the more active thiazepine (()-3b (log Y ) 6.50).
Furthermore the binding data performed on (+)-3b and
(-)-3b confirmed an “atypical” neuroleptic binding
profile for (+)-3b (log Y ) 4.65) and a “classical”
neuroleptic profile for (-)-3b (log Y ) 7.42), showing a
stereoselective interaction at D2 receptors (Table 2).3,21,22
2. Beh a vior a l a n d Bioch em ica l Effects. Admin-
istration of (()-3b prior to 1 mg/kg apomorphine caused
a dose-related suppression of apomorphine-induced lo-
comotor activity [F(4,21) ) 8.303, p < 0.001; n ) 4-5].
At a dose of 1 µmol/kg locomotor activity was suppressed
to 39% of control values, whereas the maximal suppres-
sion (to 2% of control values) was measured after
Con clu sion s
The novel compounds (()-3b, (+)-3b, and (-)-3b are
centrally active dopamine receptor antagonists, with
high affinity for D2 and D3 receptors, together with a

3768 J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 20
Campiani et al.
temperature. The white solid (ammonium chloride) was
removed by filtration, and the filtrate was evaporated. The
residue was recrystallized from ethanol to give 2-amino-1-(2-
fluorophenyl)ethanone hydrochloride (6) (4.9 g) as colorless
prisms, which was used in the next step without further
purification (ref 13).
still higher affinity for 5-HT2 receptors. The novel
pyrrolobenzothiazepine (()-3b has been resolved, and
although a similar affinity for 5-HT2 and D1 receptors
has been found for the two enantiomers, the in vitro
testing confirmed a stereoselective interaction for (+)-
and (-)-3b at D2 receptors. In fact, (+)-3b is 25 times
less potent at D2 receptors than (-)-3b, maintaining a
high affinity for 5-HT2 receptors. Overall (+)-3b has
an “atypical” neuroleptic binding profile and represents
a new lead compound for the development of novel
atypical antipsychotic drugs. Moreover, compound (()-
3b is able to increase the extracellular level of dopamine
in the rat striatum in a manner similar to that of
olanzapine, although it is slightly less potent. At low
doses this compound shows atypical antipsychotic prop-
erties, but unlike olanzapine, at high doses, it induces
catalepsy. The separation between doses that suppress
apomorphine-induced locomotor activity and induce
catalepsy might indicate a safety margin for the induc-
tion of EPS. Further studies are necessary to fully
characterize the binding profile of this compound and
its enantiomers in order to understand the full spectrum
of potential side effects and to define their potential role
to treat disorders such as schizophrenia. Furthermore,
different-sized π-systems and different fused aromatic
rings might possibly lead to further optimization of the
atypical properties of these tricyclic compounds.
To a solution of 2-amino-1-(2-fluorophenyl)ethanone hydro-
chloride (6) (2.0 g, 10.5 mmol) in 17 mL of water, heated at 90
°C, were added sodium acetate (1.44 g), glacial acetic acid (9.5
mL), and 2,5-dimethoxytetrahydrofuran (1.11 mL). After
stirring for 15 min at 100 °C the mixture was cooled and
extracted with ethyl acetate. The organic layers were washed
with 20% NaHCO3 and brine, dried, and evaporated. The
residue was chromatographed (chloroform) to afford 1.83 g
(86% yield) of 7 as white crystals: mp 49-50 °C (hexanes); IR
(CHCl3) 1690 cm-1 1H NMR (CDCl3) δ 7.98-7.89 (m, 1 H),
;
7.62 (m, 1 H), 7.31-7.19 (m, 2 H), 6.66 (m, 2 H), 6.23 (m, 2
H), 5,27 (d, 2 H, J ) 3.4 Hz). Anal. (C12H10FNO) C, H, N.
1-(2-F lu or op h en yl)-2-(2-t h iocya n a t op yr r ol-1-yl)et h a -
n on e (8). To a stirred solution of 7 (0.46 g, 2.0 mmol) in dry
methanol (12 mL) cooled at 0 °C and kept under argon, was
added freshly prepared cupric thiocyanate (prepared from
sodium thiocyanate and cupric sulfate) (0.78 g, 4.0 mmol) in
portions. The reaction mixture was left to stir at 0 °C until
the black suspension turned white (12 h). The white cuprous
thiocyanate was filtered off and washed with methanol, and
the filtrate was evaporated. The residue was partitioned
between cold water and EtOAc. The organic layers were dried
and evaporated, and the crude product was chromatographed
(30% hexanes in chloroform) to give 0.32 g (62% yield) of 8 as
colorless prisms: mp 62-63 °C (cyclohexane); IR (Nujol) 2156,
1
1676 cm-1; H NMR (CDCl3) δ 7.96 (m, 1 H), 7.60 (m, 1 H),
Exp er im en ta l P r oced u r es
7.32 (m, 2 H), 6.93 (m, 1 H), 6.75 (m, 1 H), 6.32 (m, 1 H), 5.46
(d, 2 H, J ) 3.5 Hz). Anal. (C13H9FN2OS) C, H, N.
Melting points were determined using an Electrothermal
8103 apparatus and are uncorrected. IR spectra were taken
with Perkin-Elmer 398 and FT 1600 spectrophotometers. 1H
NMR spectra were recorded on Bruker 200-MHz and Varian
500-MHz spectrometers with TMS as internal standard; the
values of chemical shifts (δ) are given in ppm and coupling
constants (J ) in hertz. All reactions were carried out in an
argon atmosphere. Progress of the reaction was monitored by
TLC on silica gel plates (Riedel-de-Haen, Art. 37341). Merck
silica gel (Kieselgel 60) was used for chromatography (70-
230 mesh) and flash chromatography (230-400 mesh) col-
umns. Extracts were dried over MgSO4, and solvents were
removed under reduced pressure. HPLC separation was
performed using a Chiralpak AD Amylose column (097-702-
40808) (length × diameter ) 250 mm × 10 mm). Elemental
analyses were performed on a Perkin-Elmer 240C elemental
analyzer, and the results are within 0.4% of the theoretical
values, unless otherwise noted. Yields refer to purified
products and are not optimized.
1-[(2-Flu or op h en yl)-2-(p yr r ol-1-yl)eth a n on e (7). A mix-
ture of 1-(2-fluorophenyl)ethanone (5) (5.0 g, 36.0 mmol) and
anhydrous aluminum chloride (43 mg, 0.32 mmol) in 5 mL of
anhydrous ethyl ether was cooled at 0 °C under argon, and a
solution of bromine (1.84 mL, 36.0 mmol) in 5 mL of anhydrous
ethyl ether was added dropwise. After stirring for 3 h the
solvent was removed by filtration, and the solid residue was
washed with 3 mL of water and then with 3 mL of light
petroleum ether. The residue was recrystallized from metha-
nol to afford yellowish prisms of the 2-bromo derivative (5.3
g, 83%): mp 57-58 °C (hexanes); IR (neat) 1670 cm-1; 1H NMR
(CDCl3) δ 7.81 (m, 1 H), 7.50-7.30 (m, 2 H), 7.17 (m, 1 H),
4.40 (s, 2 H). Anal. (C8H6BrFO) C, H, N.
2,3-Dih yd r o-2-im in o-3-(2-flu or oben zoyl)p yr r olo[2,1-b]-
th ia zole (10). To a stirred and cooled (-20 °C) solution of
the thiocyanatopyrrole 8 (160 mg, 0.6 mmol) in freshly distilled
N,N-dimethylformamide (DMF) (3.6 mL) was added sodium
methoxide (82 mg, 1.51 mmol) in portions. After 2 h at -20
°C, the suspension was warmed to room temperature and
allowed to stir for 3 h. The solvent was evaporated, and the
residue was taken up in 10 mL of water. The aqueous
suspension was neutralized with 1 N HCl and then extracted
with EtOAc. The organic layers were washed with brine,
dried, and evaporated. The residue was chromatographed
(ethyl acetate) to afford the thiazole 10 (126 mg, 81%) as brown
prisms: mp 93-94 °C (EtOAc); IR (Nujol) 3300 cm-1; 1H NMR
(CDCl3) δ 7.47 (m, 2 H), 7.35-7.20 (m, 3 H), 7.13 (br s, 1 H),
6.10 (m, 3 H); MS m/z 260 (50, M+), 240, 172, 123 (100), 110,
95. Anal. (C13H9FN2OS) C, H, N.
2-(P h en ylth io)p yr r ole (12). To a solution of phenylmag-
nesium bromide (prepared from bromobenzene (0.75 mL, 6
mmol) and magnesium turnings (0.19 g, 7.8 mmol)) in anhy-
drous THF (20 mL), cooled at 0 °C, was slowly added a solution
of 2-thiocyanatopyrrole (11) (0.5 g, 4.0 mmol) in anhydrous
THF (20 mL). After stirring at 0 °C for 30 min, the mixture
was poured into crushed ice and extracted with ethyl acetate.
The organic phase was washed with 20% NH4Cl, dried, and
evaporated. The residue was purified by chromatography
(35% hexanes in chloroform) to afford 0.6 g (93% yield) of 12
as colorless prisms: mp 86-87 °C (hexanes); IR (CHCl3) 3420
cm-1; 1H NMR (CDCl3) δ 8.20 (br s, 1 H), 7.25-6.95 (m, 5 H),
6.92 (m, 1 H), 6.55 (m, 1 H), 6.31 (m, 1 H). Anal. (C9H9NS)
C, H, N.
2-(P h en ylth io)p yr r ole-1-a cetic Acid Eth yl Ester (13).
To a mixture of 18-crown-6 (20 mg, 0.074 mmol) and potassium
tert-butoxide (0.166 mg, 1.48 mmol) in anhydrous THF (5 mL)
was added a solution of 12 (0.2 g, 1.14 mmol) in anhydrous
THF (5 mL), under argon. After the mixture was left for 2 h
at room temperature, a solution of ethyl bromoacetate (0.254
mL, 2.28 mmol) in anhydrous THF (1 mL) was added dropwise.
After stirring for 30 min at room temperature and addition of
5 mL of water, the solvent was removed under reduced
pressure and the residue extracted with EtOAc. The organic
To a solution of 2-bromo-1-(2-fluorophenyl)ethanone (7.8 g,
36 mmol) in 70 mL of dry chloroform was added hexameth-
ylenetetramine (5.04 g, 36 mmol) in portions. The reaction
mixture was allowed to stir at room temperature for 15 h. The
solid formed was removed by filtration, washed with 5 mL of
chloroform, and dried. The hexamethylenetetrammonium salt
obtained (9.9 g, 27.7 mmol) was added to a solution of
concentrated hydrochloric acid (7.94 mL) in 63.5 mL of ethanol.
The mixture was stirred for 96 h in the dark at room

New Antipsychotics Based on Pyrrolobenzothiazepine
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 20 3769
layers were washed with brine, dried, and evaporated. The
residue was chromatographed (30% hexanes in chloroform) to
give 0.28 g (96%) of 13 as colorless prisms: mp 101-102 °C
(cyclohexane); IR (CHCl3) 1760 cm-1; 1H NMR (CDCl3) δ 7.25-
6.90 (m, 6 H), 6.61 (m, 1 H), 6.31 (m, 1 H), 4.68 (s, 2 H), 4.05
°C (hexanes); IR (CHCl3) 1685 cm-1; 1H NMR (CDCl3) δ 7.98-
7.73 (m, 3 H), 5.57 (s, 2 H), 2.31 (s, 3 H). Anal. (C9H8BrClOS)
C, H.
1-[2-(Meth ylth io)ph en yl]-2-(pyr r ol-1-yl)eth an on e (22a).
Starting from 21a (2.1 g, 8.6) the 2-amino-1-[2-(methylthio)-
phenyl]ethanone hydrochloride was obtained according to the
(q, 2 H, J ) 7.0 Hz), 1.14 (t, 3 H, J ) 7.1 Hz). Anal. (C14H15
NO2S) C, H, N.
-
1
procedure described for 6: 78% yield; H NMR (DMSO-d6) δ
8.43 (br s, 2 H), 8.11-7.31 (m, 5 H), 4.59 (d, 2 H, J ) 3.2 Hz),
2-(P h en ylth io)p yr r ole-1-a cetic Acid (14). Ester 13 (0.25
g, 0.95 mmol) was dissolved in 4 mL of ethanol/THF (1:1), and
5% NaOH (3.5 mL) was added. The mixture was stirred at
room temperature for 30 min, the solution was adjusted to pH
5-6 with 1 N HCl, and ethanol and THF were evaporated.
The aqueous residue was extracted with EtOAc. The organic
layers were washed with brine, dried, and concentrated. The
crude product was purified by chromatography (EtOAc) to give
0.2 g (89%) of 14 as white crystals: mp 126-127 °C (EtOAc);
2.46 (s, 3 H). Anal. (C9H12ClNOS) C, H, N.
Starting from 2-amino-1-[2-(methylthio)phenyl]ethanone
hydrochloride the title compound was obtained as colorless
prisms following the procedure described for 7: 50% yield; mp
113-114 °C (hexanes); IR (Nujol) 1690 cm-1; 1H NMR (CDCl3)
δ 7.74-7.23 (m, 4 H), 6.66 (m, 2 H), 6.21 (m, 2 H), 5.25 (d, 2
H, J ) 3.4 Hz), 2.44 (s, 3 H). Anal. (C13H13NOS) C, H, N.
1-[5-Ch lor o-2-(m eth ylth io)p h en yl]-2-(p yr r ol-1-yl)eth a -
n on e (22b). Starting from 21b (5.58 g, 20.0 mmol) the
2-amino-1-[5-chloro-2-(methylthio)phenyl]ethanone hydrochlo-
ride was obtained according to the procedure described for 6:
IR (Nujol) 2491 cm-1 1H NMR (CDCl3) δ 12.88 (br s, 1 H),
;
7.31-6.98 (m, 6 H), 6.55 (m, 1 H), 6.23 (m, 1 H), 4.69 (s, 2 H).
Anal. (C12H11NO2S) C, H, N.
1
2-(P h en ylth io)p yr r ole-1-selen oa cetic Acid Meth yl Es-
ter (15). A solution of dimethylaluminum methylselenolate
(2.2 mmol) (prepared by heating a toluene solution of trim-
ethylaluminum with powdered selenium for 2 h at reflux under
argon) in dry toluene (1.1 mL) was added dropwise to a
solution of 13 (0.57 g, 2.2 mmol) in dry dichloromethane (5
mL) cooled at 0 °C, under argon. The mixture was stirred at
0 °C for 45 min, warmed to room temperature, and stirred for
an additional 45 min. Water was added (2 mL), and the
mixture was extracted with EtOAc. The organic layers were
washed with brine, dried, and evaporated. The crude product
was purified by distillation (85 °C/0.1 mmHg) to give 0.6 g
75% yield; H NMR (DMSO-d6) δ 8.41 (br s, 2 H), 8.10-7.28
(m, 3 H), 4.48 (d, 2 H, J ) 3.2 Hz), 2.42 (s, 3 H). Anal. (C9H11
Cl2NOS) C, H, N.
-
Starting from 2-amino-1-[5-chloro-2-(methylthio)phenyl]e-
thanone hydrochloride the title compound was obtained as
colorless prisms following the procedure described for 7: 51%
yield; mp 124-125 °C (hexanes); IR (Nujol) 1720 cm-1 1H
;
NMR (CDCl3) δ 7.62 (d, 1 H, J ) 2.3 Hz), 7.45 (dd, 1 H, J )
8.2, 2.3 Hz), 7.29 (d, 1 H, J ) 8.2 Hz), 6.65 (m, 2 H), 6.22 (m,
2 H), 5.21 (s, 2 H), 2.43 (s, 3 H); 13C NMR (CDCl3) δ 194.2,
140.6, 134.5, 132.4, 130.1, 128.9, 127.7, 121.8, 109.2, 56.6, 16.6.
Anal. (C13H12ClNOS) C, H, N.
1
(97%) of 15 as a colorless oil: IR (neat) 1720 cm-1; H NMR
1-[2-(Met h ylsu lfin yl)p h en yl]-2-(p yr r ol-1-yl)et h a n on e
(23a ). To a suspension of sodium periodate (0.55 g, 2.6 mmol)
in methanol (7 mL) and water (1.4 mL) was added a solution
of 22a (0.6 g, 2.6 mmol) in methanol (2 mL). After the mixture
stirred for 20 h at room temperature, sodium iodate was
removed by filtration, and the filtrate was evaporated. The
residue was chromatographed (5% EtOAc in dichloromethane)
to give 0.59 g (92%) of 23a as colorless prisms: mp 174-175
(CDCl3) δ 7.24-6.95 (m, 6 H), 6.69 (m, 1 H), 6.37 (m, 1 H),
4.69 (s, 2 H), 2.11 (s, 3 H); MS m/z 311 (40, M+), 188, 155,
109, 91 (100). Anal. (C13H13SeNOS) C, H, N.
1-[2-(Meth ylth io)p h en yl]eth a n on e (18). To a suspension
of lithium hydride (0.57 g, 6.7 mmol) in anhydrous 1,2-
dimethoxyethane (5 mL), vigorously stirred, was added drop-
wise a solution of acid 17 (1.0 g, 5.9 mmol) in anhydrous 1,2-
dimethoxyethane (5 mL). The suspension was refluxed for 2.5
h and cooled at -10 °C, and methyllithium (4.2 mL, 6.7 mmol,
1.6 M) was added within 30 min. The reaction mixture was
stirred for 2 h at room temperature; 1 N HCl (15 mL) was
added, and the mixture was extracted with ethyl ether. The
organic layers were washed with brine, dried, and concen-
trated. Chromatography of the crude product (5% benzene in
dichloromethane) gave 0.78 g (79%) of 18 as colorless prisms,
whose spectroscopic data were identical with those reported
in ref 19.
1
°C (ethanol); IR (Nujol) 1710, 1090 cm-1; H NMR (CDCl3) δ
8.42-7.64 (m, 4 H), 6.66 (m, 2 H), 6.27 (m, 2 H), 5.44 (0.5 ABq,
1 H, J ) 18.0 Hz), 5.27 (0.5 ABq, 1 H, J ) 18.0 Hz), 2.80 (s, 3
H). Anal. (C13H13NO2S) C, H, N.
1-[5-Ch lor o-2-(m eth ylsu lfin yl)p h en yl]-2-(p yr r ol-1-yl)-
eth a n on e (23b). Starting from 22b (1.1 g, 4.45 mmol) the
title compound was prepared following the above-described
procedure: colorless prisms (89% yield); mp 218-219 °C
(ethanol); IR (Nujol) 1710, 1080 cm-1; 1H NMR (CDCl3) δ 8.37
(d, 1 H, J ) 8.0 Hz), 7.85 (m, 2 H), 6.66 (m, 2 H), 6.28 (m, 2
H), 5.40 (0.5 ABq, 1 H, J ) 17.7 Hz), 5.25 (0.5 ABq, 1 H, J )
17.8 Hz), 2.79 (s, 3 H); 13C NMR (CDCl3) δ 193.2, 149.6, 136.9,
134.7, 132.5, 128.8, 127.0, 121.8, 109.8, 55.7, 44.3. Anal.
(C13H12ClNO2S) C, H, N.
1-[5-Ch lor o-2-(m eth ylth io)ph en yl]eth an on e (20). A mix-
ture of 19 (1.0 g, 6.3 mmol), anhydrous aluminum chloride
(1.88 g, 13.5 mmol), and carbon disulfide (20 mL) was heated
at reflux under argon, and acetic anhydride (0.46 mL, 6.3
mmol) was added dropwise. After refluxing for 4 h, the
solution was poured into crushed ice, and 20 mL of 6 N HCl
was added. The mixture was extracted with EtOAc, and the
organic layers were washed with brine, dried, and concen-
trated. The oily residue was chromatographed (30% hexanes
in chloroform) to give 0.5 g (40%) of 20 as a waxy solid: IR
(neat) 1670 cm-1; 1H NMR (CDCl3) δ 7.83 (d, 1 H, J ) 2.1 Hz),
7.44 (dd, 1 H, J ) 8.1, 2.1 Hz), 7.29 (d, 1 H, J ) 8.1 Hz), 2.63
(s, 3 H), 2.41 (s, 3 H). Anal. (C9H9ClOS) C, H.
9,10-Dih yd r op yr r olo[2,1-b][1,3]b en zot h ia zep in -9-on e
(9a ). Meth od A: The following reaction must be performed
in inert atmosphere, and the copper reagent has been prepared
according to ref 12b. To a solution of the highly reactive
crystalline complex of copper(I) triflate and benzene (0.81 g,
1.6 mmol) in dry benzene (20 mL), cooled at 0 °C, was added
a solution of selenoester 15 (0.5 g, 1.6 mmol) in dry benzene
(11 mL), and the mixture was allowed to stir at room
temperature for 16 h. Ethyl ether (10 mL) was added; the
organic phase was washed with 6 N ammonia, dried, and
concentrated. The crude product was chromatographed (30%
hexanes in dichloromethane) to give 51 mg (12%) of 9a as
colorless prisms. The ketone 16 (55%) was also recovered from
the reaction mixture as a tick oil. Compound 9a : mp 94-95
°C (hexanes); IR (CHCl3) 1690 cm-1; 1H NMR (CDCl3) δ 8.14-
7.30 (m, 4 H), 6.88 (m, 1 H), 6.42 (m, 1 H), 6.12 (m, 1 H), 5.15
(s, 2 H); 13C NMR (CDCl3) δ 190.9, 140.0, 136.1, 133.3, 132.3,
130.8, 127.6, 123.9, 120.2, 114.4, 109.2, 57.6; MS m/z 265 (10,
M+), 215 (100), 187, 154, 115, 97. Anal. (C12H9NOS) C, H, N.
Compound 16: IR (neat) 1670 cm-1; 1H NMR (CDCl3) δ 7.22-
2-Br om o-1-[2-(m eth ylth io)p h en yl]eth a n on e (21a ). The
title compound was prepared starting from 18 (2.09 g, 12.6
mmol) and following the procedure as described to obtain 6.
21a was obtained as colorless prisms (69% yield): mp 81-82
°C (hexanes); IR (Nujol) 1690 cm-1; 1H NMR (CDCl3) δ 8.00-
7.80 (m, 2 H), 7.35 (m, 2 H), 5.53 (s, 2 H), 2.27 (s, 3 H). Anal.
(C9H9BrOS) C, H.
2-Br om o-1-[5-ch lor o-2-(m et h ylt h io)p h en yl]et h a n on e
(21b). The title compound was obtained starting from 20 (1.26
g, 6.3 mmol) and following the procedure as described for 6.
21b was obtained as colorless prisms (62% yield): mp 97-98

3770 J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 20
Campiani et al.
6.81 (m, 6 H), 6.70 (m, 1 H), 6.37 (m, 1 H), 4.61 (s, 2 H), 2.20
(()-9-(4-Met h ylp ip er a zin -1-yl)-9,10-d ih yd r op yr r olo-
[2,1-b][1,3]ben zoth ia zep in e (3a ). A mixture of 25a (0.65
g, 2.0 mmol) and N-methylpiperazine (1.1 mL, 10.0 mmol) was
heated at 130 °C for 2 h under argon, cooled, poured into
crushed ice, and extracted with ethyl ether. The combined
organic extracts were washed with brine, dried, and concen-
trated. The residue was chromatographed (EtOAc) to give 0.45
(s, 3 H); MS m/z 231 (100, M+). Anal. (C13H13NOS) C, H, N.
Meth od B: Trifluoroacetic anhydride (1.0 mL, 7.4 mmol)
was added dropwise to freshly distilled N,N-dimethylforma-
mide (8 mL) cooled at 0 °C. After the mixture stirred for 20
min at 0 °C, a solution of 23a (1.0 g, 4.0 mmol) in freshly
distilled N,N-dimethylformamide (24 mL) was added. After
15 min at 0 °C and 1 h at room temperature, the pH of the
dark-red solution was adjusted to 7 with 1 N NaOH, and the
mixture was stirred for an additional 30 min. Extraction with
dichloromethane, drying of the extracts, and evaporation of
the solvent gave an oily residue which was chromatographed
(30% hexanes in chloroform). Compound 9a was obtained in
45% yield.
1
g (75%) of 3a as colorless prisms: 206-207 °C (hexanes); H
NMR (CDCl3) δ 7.49-7.09 (m, 4 H), 6.87 (m, 1 H), 6.29 (m, 1
H), 6.06 (m, 1 H), 4.68 (dd, 1 H, J ) 14.4, 8.6 Hz), 4.51 (dd, 1
H, J ) 14.4, 3.7 Hz), 4.04 (dd, 1 H, J ) 8.6, 3.7 Hz), 2.56-2.34
(m, 8 H), 2.23 (s, 3 H); 13C NMR (CDCl3) δ 138.1, 134.6, 132.9,
130.4, 127.3, 126.9, 123.9, 121.7, 113.3, 107.7, 66.1, 55.9, 48.8,
46.6, 46.1; MS m/z 299 (100, M+), 219, 200, 167, 149, 113. Anal.
(C17H21N3S) C, H, N.
7-Ch lor o-9,10-dih ydr opyr r olo[2,1-b][1,3]ben zoth iazepin -
9-on e (9b). The title compound was obtained in 42% yield,
as colorless prisms, starting from 23b and following the
procedure as described for 9a (method B): mp 106-107 °C
(()-7-Ch lor o-9-(4-m eth ylp ip er a zin -1-yl)-9,10-d ih yd r o-
p yr r olo[2,1-b][1,3] b en zot h ia zep in e (3b). Starting from
25b (0.3 g, 0.95 mmol) the title compound was obtained
following the above-described procedure. 3b was obtained as
1
(hexanes); IR (CHCl3) 1690 cm-1; H NMR (CDCl3) δ 8.14 (d,
1
colorless prisms (68%): mp 210-211 °C (hexanes); H NMR
1 H, J ) 2.2 Hz), 7.49 (d, 1 H, J ) 8.1 Hz), 7.38 (dd, 1 H, J )
8.0, 2.3 Hz), 6.88 (m, 1 H), 6.43 (m, 1 H), 6.12 (m, 1 H), 5.14
(s, 2 H); 13C NMR (CDCl3) δ 189.7, 138.3, 137.3, 134.1, 133.1,
132.2, 131.9, 124.1, 119.5, 114.7, 109.5, 57.3; MS m/z 250 (20,
M+), 249 (100), 221, 216, 188, 158, 110. Anal. (C12H8ClNOS)
C, H, N.
(CDCl3) δ 7.51 (d, 1 H, J ) 2.4 Hz), 7.30 (d, 1 H, J ) 8.5 Hz),
7.06 (dd, 1 H, J ) 8.5, 2.4 Hz), 6.86 (m, 1 H), 6.29 (m, 1 H),
6.05 (m, 1 H), 4.71 (dd, 1 H, J ) 14.0, 8.6 Hz), 4.45 (dd, 1 H,
J ) 14.0, 3.4 Hz), 3.95 (dd, 1 H, J ) 8.6, 3.4 Hz), 2.61-2.25
(m, 8 H), 1.42 (s, 3 H); 13C NMR (CDCl3) δ 140.1, 133.2, 133.0,
132.4, 131.6, 127.3, 123.9, 121.1, 113.6, 107.9, 65.9, 55.8, 55.7,
47.7, 45.9, 44.9, 26.8; MS m/z 333 (10, M+), 250, 233 (100),
201, 166, 139. Anal. (C17H20ClN3S) C, H, N. The dihydro-
chloride salt was obtained dissolving an analytical sample in
1 N methanolic HCl. The solvent was evaporated, and the
residue was recrystallized (methanol and ethyl ether, 1/1).
Anal. (C17H22Cl3N3S) C, H, N.
(()-9,10-Dih yd r o-9-h yd r oxyp yr r olo[2,1-b][1,3]b en zo-
th ia zep in e (24a ). To a solution of 9a (61 mg, 0.23 mmol) in
dry methanol (1 mL), cooled at 0 °C and under argon, was
added sodium borohydride (80 mg, 0.23 mmol) in portions.
After stirring for 1 h at 0 °C, the reaction was quenched with
water (1 mL) and the mixture was extracted with EtOAc. The
organic layers were washed with brine, dried, and concen-
trated. The residue was chromatographed (15% EtOAc in
dichloromethane) to give 24a (64 mg, 92% yield) as colorless
Sem ip r ep a r a tive Ch ir a l Sep a r a tion of (()-3b. At first
the dihydrochloride salt of (()-3b was purified over a short
column filled with silica gel using dichloromethane and
methanol (9/1) as eluant. The purified compound was con-
verted to the free base. Evaporation of the solvent afforded
an oily residue which was dissolved in 2-propanol, and the
solution was diluted with hexanes until a ratio of 95/5 was
reached. For separation of enantiomers a concentration of 10-
15 mg/mL racemate was made. A mixture of hexanes (plus
0.1% triethylamine) and 2-propanol was used as the mobile
phase. A gradient mixer kept the ratio of both solvents
(hexanes and 2-propanol) at 95:5. The injections were 100 µL
per injection. The enantiomers were collected using a fraction
collector. Only fractions with a signal above 10% (10 mv) of
the whole scale were collected. The amount below the 10%
was collected apart and used for a second purification. The
purity of both enantiomers was determined by weighing of the
plotted peaks separately.
1
prisms: mp 101-102 °C (ethanol); IR (Nujol) 3300 cm-1; H
NMR (CDCl3) δ 7.47-7.12 (m, 4 H), 6.86 (m, 1 H), 6.33 (m, 1
H), 6.02 (m, 1 H), 5.08 (m, 1 H), 4.89 (dd, 1 H, J ) 13.9, 1.7
Hz), 4.28 (dd, 1 H, J ) 13.9, 6.0 Hz), 2.05 (d, 1 H, J ) 9.6 Hz).
Anal. (C12H11NOS) C, H, N.
(()-7-Ch lor o-9,10-d ih yd r o-9-h yd r oxyp yr r olo[2,1-b][1,3]-
ben zoth ia zep in e (24b). Starting from 9b (112 mg, 0.45
mmol) the title compound was obtained following the above-
described procedure: 88% yield; mp 118-119 °C (ethanol); IR
1
(CHCl3) 3300 cm-1; H NMR (CDCl3) δ 7.48 (d, 1 H, J ) 2.1
Hz), 7.32 (d, 1 H, J ) 8.0 Hz), 7.15 (dd, 1 H, J ) 8.1, 2.1 Hz),
6.88 (m, 1 H), 6.34 (m, 1 H), 6.11 (m, 1 H), 5.02 (m, 1 H), 4.85
(dd, 1 H, J ) 13.9, 1.9 Hz), 4.29 (dd, 1 H, J ) 13.9, 6.6 Hz),
2.10 (d, 1 H, J ) 9.6 Hz). Anal. (C12H10ClNOS) C, H, N.
(()-9-Br om o-9,10-d ih yd r op yr r olo[2,1-b][1,3]b en zo-
th ia zep in e (25a ). To a solution of 24a (0.26 g, 1.0 mmol) in
anhydrous ethyl ether (4 mL) was added dropwise a solution
of PBr3 (0.13 g, 0.5 mmol) in anhydrous ethyl ether (1 mL),
and the reaction mixture was refluxed for 2 h, under argon.
Anhydrous ethanol (0.2 mL) was added, and the resulting
solution was heated under reflux for an additional hour. Then
5 mL of 10% aqueous Na2CO3 was added; the organic phase
was separated, dried, and evaporated. The crude product was
chromatographed (hexanes and chloroform, 1/1) to give 25a
(0.2 g, 64%) as colorless prisms: mp 115-116 °C (cyclohexane);
1H NMR (CDCl3) δ 7.46-7.09 (m, 4 H), 6.93 (m, 1 H), 6.39 (m,
1 H), 6.12 (m, 1 H), 5.75 (dd, 1 H, J ) 6.9, 2.6 Hz), 5.07 (dd, 1
H, J ) 14.7, 2.6 Hz), 4.61 (dd, 1 H, J ) 14.7, 6.9 Hz). Anal.
(C12H10BrNS) C, H, N.
1
(+)-3b: H NMR (500 MHz, CDCl3) δ 7.52 (d, 1 H, J ) 2.4
Hz), 7.32 (d, 1 H, J ) 8.3 Hz), 7.09 (dd, 1 H, J ) 2.4, 8.3 Hz),
6.88 (m, 1 H), 6.30 (m, 1 H), 6.07 (m, 1 H), 4.71 (dd, 1 H, J )
8.8, 14.2 Hz), 4.50 (dd, 1 H, J ) 3.9, 14.7 Hz), 3.97 (dd, 1 H, J
) 3.4, 8.8 Hz), 2.55 (m, 4 H), 2.40 (m, 4 H), 2.27 (s, 3 H); 13C
NMR (500 MHz, CDCl3) δ 139.9, 133.0, 132.9, 132.3, 131.6,
127.3, 123.8, 121.0, 113.5, 107.9, 88.2, 65.8, 55.6, 48.6, 45.9,
45.8; purity (ee) 94.6%; [R]D ) +46.0° (c 0.48, MeOH).
1
(-)-3b: H NMR (500 MHz, CDCl3) δ 7.53 (d, 1 H, J ) 2.3
Hz), 7.32 (d, 1 H, J ) 8.3 Hz), 7.09 (d, 1 H, J ) 6.8 Hz), 6.88
(m, 1 H), 6.30 (m, 1 H), 6.07 (m, 1 H), 4.71 (dd, 1 H, J ) 9.3,
14.5 Hz), 4.48 (dd, 1 H, J ) 3.4, 14.2 Hz), 3.98 (dd, 1 H, J )
2.9, 8.8 Hz), 2.49 (m, 8 H), 2.27 (s, 3 H); 13C NMR (500 MHz,
CDCl3) δ 140.0, 133.0, 132.9, 132.3, 131.6, 127.3, 123.8, 121.0,
113.5, 107.9, 88.2, 65.8, 55.6, 48.6, 45.9, 45.8; purity (ee) 98.0%;
[R]D ) -47.9° (c 0.54, MeOH).
(()-9-Br om o-7-ch lor o-9,10-d ih yd r op yr r olo[2,1-b][1,3]-
ben zoth ia zep in e (25b). Starting from 24b (0.31 g, 1.6 mmol)
the title compound was obtained following the above-described
procedure: 51% yield; mp 106-107 °C (cyclohexane); 1H NMR
(CDCl3) δ 7.45 (d, 1 H, J ) 2.1 Hz), 7.27 (d, 1 H, J ) 8.6 Hz),
7.11 (dd, 1 H, J ) 8.6, 2.1 Hz), 6.92 (m, 1 H), 6.39 (m, 1 H),
6.12 (m, 1 H), 5.63 (dd, 1 H, J ) 7.0, 2.3 Hz), 5.06 (dd, 1 H, J
) 14.4, 2.3 Hz), 4.61 (dd, 1 H, J ) 14.0, 7.0 Hz); 13C NMR
(CDCl3) δ 139.9, 134.1, 133.2, 131.7, 131.5, 128.9, 125.6, 119.6,
114.6, 108.1, 51.2, 51.0. Anal. (C12H9BrClNS) C, H, N.
Ma ter ia ls a n d Meth od s. 1. In Vitr o Bin d in g Assa y.
Male CRL:CD(SD)BR-COBS rats (Charles River, Italy) were
killed by decapitation; their brains were rapidly dissected into
the various areas (striatum for D1 and D2 receptors, olfactory
tubercle for D3 receptors, and cortex for 5-HT2 receptors) and
stored at -80 °C until the day of assay. Tissues were
homogenized in about 50 volumes of Tris HCl, 50 mM, pH 7.4
(for D1, D2, and 5-HT2 receptors) or Hepes Na 50 mM, pH 7.5

New Antipsychotics Based on Pyrrolobenzothiazepine
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 20 3771
(for D3 receptors), using an Ultra-Turrax TP-1810 (2 × 20 s),
and centrifuged at 50000g for 10 min. The pellets were then
washed once by resuspension in fresh buffer and centrifugation
as before. The pellets obtained were resuspended in the
appropriate incubation buffer (Tris HCl, 50 mM, pH 7.1,
containing 10 µM pargyline, 0.1% ascorbic acid, 120 mM NaCl,
5 mM KCl, 2 mM CaCl2, 1 mM MgCl2 for D1 and D2 receptors;
Hepes Na, 50 mM, pH 7.5, containing 1 mM EDTA, 0.005%
ascorbic acid, 0.1% albumine, 200 nM eliprodil for D3 receptors)
just before the binding assay. [3H]SCH 23390 (specific activity
(sa) 71.1 Ci/mmol; NEN) binding to D1 receptors was assayed
in a final incubation volume of 0.5 mL, consisting of 0.25 mL
of membrane suspension (2 mg of tissue/sample), 0.25 mL of
[3H]ligand (0.4 nM), and 10 µL of displacing agent or solvent.
Nonspecific binding was obtained in the presence of 10 mM
(-)-cis-flupentixol. [3H]Spiperone (sa 19.0 Ci/mmol; NEN)
binding to D2 receptors was assayed in a final incubation
volume of 1 mL, consisting of 0.5 mL of membrane suspension
(1 mg of tissue/sample), 0.5 mL of [3H]ligand (0.2 nM), and 20
µL of displacing agent or solvent. Nonspecific binding was
obtained in the presence of 100 µL of (-)-sulpiride. [3H]-7-
OH-DPAT (sa 139 Ci/mmol; Amersham) binding to D3 recep-
tors was assayed in a final incubation volume of 1 mL,
consisting of 0.5 mL of membrane suspension (10 mg of tissue/
sample), 0.5 mL of [3H]ligand (0.7 nM), and 20 µL of displacing
agent or solvent. Nonspecific binding was obtained in the
presence of 1 µM dopamine. [3H]Ketanserin (sa 60 Ci/mmol;
Amersham) binding to 5-HT2 receptors was assayed in a final
incubation volume of 1 mL consisting of 0.5 mL of membrane
suspension (5 mg of tissue/sample), 0.5 mL of [3H]ligand (0.7
nM), and 0.02 mL of displacing agent or solvent. Nonspecific
binding was obtained in the presence of 1 µM methysergide.
Incubations (15 min at 37 °C for D1, D2, and 5-HT2 receptors,
60 min at 25 °C for D3 receptors) were stopped by rapid
filtration under vacuum through GF/B (for D1, D2, and 5-HT2
receptors) or GF/C (for D3 receptors) filters which were then
washed with 12 mL of ice-cold buffer, using a Brandel M-48R.
The radioactivity trapped on the filters was counted in 4 mL
of Ultima Gold MV (Packard) in a LKB 1214 rack beta liquid
scintillation spectrometer with a counting efficiency of 60%.
[3H]Spiperone binding to D4 receptors was performed using
autoradiography as follows: the rats were killed by decapita-
tion, and the brains were rapidly removed, frozen in liquid
nitrogen, and stored at -80 °C until use. Consecutive coronal
sections (14 µm) were cut at -16° at the level of anterior
caudate putamen, including nucleus accumbens and islands
of Calleja (plate 12-13 of the Paxinos and Watson rat brain
atlas, 1982) using a cryostat (microm HM 500 OM), thaw-
monted onto gelatin-coated glass slides, and stored at -20 °C
until the binding experiments. After a 5-min preincubation
in 50 mM Tris HCl, pH 7.4, containing 5 mM EDTA, 1.5 mM
CaCl2, and 5 mM KCl, the slides were incubated for 30 min at
room temperature in the same buffer with the addition of 0.4
nM [3H]spiperone. Nonspecific binding was determined in the
presence of 1 µM spiperone. Incubations were stopped with
two 5-min rinses in ice-cold 50 mM Tris HCl, pH 7.4, and one
rapid dipping in ice-cold distilled water. After washing, the
slides were dried overnight under a stream of cold air, apposed
to Hyperfilm (Amersham), and placed in X-ray biox. After
appropriate exposure (6 weeks), the films were developed in
Kodak D19 at 18 °C for 10 min, and optical densities of
autoradiograms were determined with a RAS 3000 image
analyzer (Loats Associate). Drugs were tested in triplicate at
10-5 M.
The reaction was stopped 5 min later by adding 2 mL of ice-
cold Krebs-Henseleit buffer and rapid filtration under vacuum
on cellulose nitrate filters (0.65-µm pore size; Millipore), which
were washed twice with 2 mL of the same buffer. The
radioactivity trapped on the filters was counted in 4 mL of
Ultima Gold MV (Packard) in a LKB 1214 rack beta liquid
scintillation spectrometer with a counting efficiency of 60%.
3. Ca lcu la tion s. Drugs were tested in triplicate at dif-
ferent concentrations, from 10-5
to 10-10 M. IC50’s, the
concentration of drug that caused 50% inhibition of [3H]-
dopamine uptake or [3H]ligand binding, were obtained using
“Allfit” program running on an IBM XT personal computer.
4. Beh a vior a l Assa y a n d Dia lysis Exp er im en ts. For
behavioral testing male rats (Harlan, Zeist, The Netherlands)
weiging 200-250 g were used. Until the experiment, animals
were group-housed (6/cage) with food and water available ad
libitum and on a 12:12-h day-night schedule (lights on 7.30
a.m.; lights off 7.30 p.m.). Catalepsy was tested on a grid (grid
size: 1.5 × 1.5 cm) that was vertically placed. The time to
leave the grid was measured in three consecutive sessions 30
min after injection of vehicle or drug. Rats that remained for
>30 s on the grid (average of three sessions) were considered
cataleptic. After testing for catalepsy, rats were injected with
1 mg/kg apomorphine (40 min after drug administration), and
locomotor activity was measured for 30 min using AUTOMEX
II (Columbus Instruments, Columbus, OH) activity monitors.
Dialysis experiments were performed in male rats (Harlan,
Zeist, The Netherlands) weighing 275-350 g. Until surgery
for microdialysis probe implantation, rats were treated as
described for behavioral experiments. Twenty-four hours
before the dialysis experiments, rats were anesthetized with
400 mg/kg chloral hydrate and microdialysis probes inserted
in the left and right striatum. After probe implantation rats
were housed individually. At the start of the dialysis experi-
ments, probes were perfused with CSF (mmol/L: NaCl, 147;
KCl, 4; CaCl2, 1.2; and MgCl2, 1.0). Probe outlets were
connected to an injection valve of an HPLC system, and
dialysates were automatically injected every 15 min. After
stabilization of the baseline output, drugs were injected sc,
and effects were recorded for 150 min. Levels of both dopam-
ine and DOPAC were measured using HPLC with electro-
chemical detection.
Behavioral data are given as counts per 30 min and dialysis
data as percentage of control values (i.e., the average output
value 60 min preceding drug administration). Data were
analyzed with ANOVA.
Ack n ow led gm en t. This work was supported by a
grant from MURST (60%) and CNR (96.00837.CT03),
Rome. The authors gratefully acknowledge Sigma-Tau.
One of the authors (H.W.) thanks Lilly for a gift of the
reference compound olanzapine.
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