4-(Phenylsulfonyl)piperidines: Novel, selective, and bioavailable 5-HT2A receptor antagonists

Article abstract of DOI:10.1021/jm011030v

On the basis of a spirocyclic ether screening lead, a series of acyclic sulfones have been identifed as high-affinity, selective 5-HT_2A receptor antagonists. Bioavailability lacking in the parent, 1-(2-(2,4-difluorophenyl)ethyl)-4-(phenylsulfon

Full text of DOI:10.1021/jm011030v

492
J . Med. Chem. 2002, 45, 492-503
4-(P h en ylsu lfon yl)p ip er id in es: Novel, Selective, a n d Bioa va ila ble 5-HT2A
Recep tor An ta gon ists
Stephen R. Fletcher,* Frank Burkamp, Peter Blurton, Susan K. F. Cheng, Robert Clarkson, Desmond O’Connor,
Daniel Spinks, Matthew Tudge, Monique B. van Niel, Smita Patel, Kerry Chapman, Rose Marwood,
Sara Shepheard, Graham Bentley, Gina P Cook, Linda J Bristow, J ose L. Castro, Peter H. Hutson, and
Angus M. MacLeod
Merck Sharp and Dohme, The Neuroscience Research Centre, Terlings Park, Eastwick Road, Harlow, Essex CM20 2QR, U.K.
Received August 23, 2001
On the basis of a spirocyclic ether screening lead, a series of acyclic sulfones have been identifed
as high-affinity, selective 5-HT2A receptor antagonists. Bioavailability lacking in the parent,
1-(2-(2,4-difluorophenyl)ethyl)-4-(phenylsulfonyl)piperidine (12), was introduced by using stabil-
ity toward rat liver microsomes as a predictor of bioavailability. By this means, the 4-cyano-
and 4-carboxamidophenylsulfonyl derivatives 26 and 31 were identified as orally bioavailable,
brain-penetrant analogues suitable for evaluation in animal models. Bioavailability was also
attainable by N substitution leading to the N-phenacyl derivative 35. IKr activity detected
through counterscreening was reduced to insignificant levels in vivo with the latter compound.
In tr od u ction
and human 5-HT2A receptors was observed with the
spirocyclic ether 5, studies based on the alternative lead
were undertaken. Comparison of the structure of
MDL100907 and the spirocyclic ether initially suggested
that spirocyclic alcohols would be high-affinity 5-HT2A
ligands. Searching of the literature revealed that alcohol
7, reported as a σ ligand, showed high affinity for the
5-HT2A receptor in counterscreening assays, and we
were able to confirm this (Table 1).19 The compound,
however, like MDL100907 (2), showed very low expo-
sure following oral dosing in rat at 1-2 mg/kg (Table
2), and this avenue was not pursued further.
It is generally accepted that activation of central
5-HT2A receptors (agonism) produces the psychomimetic
effects of hallucinogenic drugs such as LSD and mes-
caline.1,2 The resulting effects in man include major
changes in mood, perception, and cognition. Blockade
of 5-HT2A receptors (antagonism) has been implicated
in the beneficial effects of newly released antidepres-
sants such as mirtazepine, nefazodone, and atypical
antipsychotic drugs such as risperidone and olanzapine.3
However, these latter compounds bind at sites in
addition to the 5-HT2A receptor.4-7 Thus, while blockade
of the 5-HT2A receptor has been demonstrated to give
rise to quantifiable behavioral effects in animal models,
such as the DOI-induced head-twitch,8 it remains
unclear whether specific blockade of central 5-HT2A
receptors will be therapeutically beneficial.9 Recently,
compounds selective for the 5-HT2 family of receptors
such as fananserin (1),10 MDL100907 (2),11 and epli-
vanserin (3)12 have been described (Figure 1). Both
fananserin13 and MDL10090714 showed a lack of efficacy
in trials of psychosis,15 with PET labeling in the latter
case being used to demonstrate high receptor oc-
cupancy.16 Eplivanserin (SR 46349B) is currently un-
dergoing clinical evaluation.17 To fully evaluate the
therapeutic potential of selective 5-HT2A antagonists,
we wished to identify a novel series of orally active
compounds suitable for evaluation in vivo both in
animal models and clinically.
In the following discussion, optimization of the screen-
ing lead 5 to give orally bioavailable, selective, high-
affinity 5-HT2A antagonists of general structure I20 will
be described.
Resu lts a n d Discu ssion
The receptor binding profile obtained for the screening
lead 5 is shown in Table 1. High affinity at the rat and
human 5-HT2A subtypes was observed (Ki of h5-HT2A
,
1.8 nM). Counterscreening, however, showed only mod-
est selectivity over D2 (320-fold) and high affinity at the
outward delayed rectifier potassium channel IKr (Ki, 20
nM). We set out to eradicate this activity because it is
now recognized that IKr blockade leads to prolongation
of the QTc interval in vivo, which can lead to episodes
of polymorphic ventricular dysrhythmias that occasion-
ally culminate in sudden death.21 A further issue was
the poor oral bioavailability of 5. Systemic exposure in
rat following oral dosing at 1.5 mg/kg was found to be
low (AUC 4 ng h/mL (Table 2)). To address these issues,
the strategy adopted was to initially identify a frame-
Comprehensive robotic screening of the Merck sample
collection generated two leads 4 and 5 (Figure 2). Indole
4 was progressed to give 6 as recently described.18
A
limitation of the indole series was the 200-fold binding
selectivity observed for the human vs the rodent form
of the 5-HT2A receptor (Table 1), since this reduced the
effectiveness of the compounds in animal behavioral
models. Because comparable binding affinity at the rat
* To whom correspondence should be addressed. Phone: 01279
440000. Fax: 01279 440390. E-mail: stephen_fletcher@merck.com.
10.1021/jm011030v CCC: $22.00 © 2002 American Chemical Society
Published on Web 12/20/2001

4-(Phenylsulfonyl)piperidines
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 493
F igu r e 1. 5HT2 antagonists.
the N substituent showed that 2,4-difluoro substitution
of the phenethyl group gives a modest but significant
increase in 5-HT2A binding affinity, as shown by a
comparison of 12 and 13 (Table 1). Furthermore, the
N-benzyl and N-phenpropyl derivatives (14 and 15,
respectively) have considerably reduced 5-HT2A binding
affinity compared to the phenethyl derivative (13).
Consequently, 12 was selected for further optimization
studies to address the remaining issue of low oral
bioavailability.
Assessment of the pharmacokinetics of 12 after iv
dosing in rat revealed plasma clearance to be relatively
high (CL, 34 mL/min/kg), as shown in Table 2. On this
basis, it was reasoned that reduction of metabolism
would enhance bioavailability. Evaluation of routes of
metabolism in vitro using rat liver microsomes showed
oxidation to occur at several positions and via several
CYP450 isozymes. Thus, little insight could be gained
into how metabolism might be blocked through specific
substitution. In an effort to identify global structural
changes that might lead to enhancement of stability,
analogues of the cyclic ether 5, available from the
company collection, were evaluated, with stability to-
ward rat liver microsomes being used as a surrogate
measure of bioavailability.
The stability toward rat liver microsomes of available
compounds structurally related to 5 is shown graphi-
cally in Chart 1. Enhanced stability was attained
through substitution of the spirocyclic ring system as
with 20 and through appropriate substitution of the
nitrogen atom as with 21 and 23. Attention was first
directed toward aromatic substitution. It was not a
straightforward task to ascertain whether reduced
turnover of 20 was derived from the presence of the keto
or the cyano group because neither the des-cyano or des-
keto derivatives were available for evaluation. Because
the 5-HT2A affinity for 20 was low, and undesired, high
IKr activity was observed in the ether series; synthesis
of the des-cyano or des-keto derivatives was not con-
sidered. Instead, aromatic substitution within the acy-
clic phenyl sulfone series was explored. The 4-cyanophe-
nyl sulfone 26 was prepared. This compound binds with
high affinity at both rat and human 5-HT2A receptors
(Table 1). Functional studies showed the compound to
be an antagonist. Counterscreening showed a 250-fold
selectivity over 5-HT2C and a >2000-fold selectivity over
D2 and R1-Adr receptors. More significantly, assessment
of pharmacokinetics in rat showed the compound to
have 23% oral bioavailability with a mean residence
time of 2.3 h (Table 2). The stability of a selection of
F igu r e 2. Lead and literature compounds.
work for optimization of activity in vitro, then to develop
the structure-activity relationships relating to bioavail-
ability.
Deletion studies shown in Table 1 were carried out
on the basis of 5 in order to determine the contribution
to 5-HT2A binding affinity provided by the substituents
and the molecular architecture. Removal of the methoxy
group to give 8 results in little loss of binding affinity.
The two fluorine atoms, on the other hand, produce a
10-fold increase in binding as shown by the loss of
affinity observed with 9 (Table 1). Most strikingly, des-
oxy derivative 10 showed that the spirocyclic ether
oxygen contributes little to 5-HT2A receptor binding
affinity. It thus became apparent that there might be
an opportunity to introduce a linking group in place of
the ether that would retain high affinity at the 5-HT2A
receptor but reduce IKr activity and enhance bioavail-
ability. From a wide range of groups evaluated, the
sulfone was found to be most advantageous. Thus,
spirocyclic sulfone 11 binds with high binding affinity
at both the rat and human forms of the 5-HT2A receptor
with good selectivity over 5-HT2C, D2, and R1-Adr
receptors. Furthermore, IKr binding is reduced when
compared to the corresponding ether 8 and the meth-
ylene compound 10. Enhancement in oral bioavailability
was not, however, observed as shown in Table 2.
The influence of ring constraint on binding affinity
was assessed through preparation of acyclic sulfone 12.
This compound was found to bind with high affinity at
both human and rat 5-HT2A receptors (Ki of h5-HT2A
,
0.33 nM). Selectivity over D2 and R1 receptors compa-
rable to the spirocyclic sulfone 11 was observed, and IKr
activity was further reduced. Exploration of changes to

494 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2
Ta ble 1. Binding Data
Fletcher et al.
a
Affinities at human cloned 5-HT2A, 5-HT2C, and D2 receptors, the IKr channel (hERG), and rat 5-HT2A and R1Adrenergic receptors.
substituted phenyl sulfones in the presence of rat
microsomal stability is shown in Chart 2. Comparison
of the 4-cyano derivative 26 with the 2- and 3-cyano
derivatives 27 and 28 showed that enhanced stability
is only obtained with a cyano group at the 4-position.
Substitution with F and Cl at the 4-position (29 and
30, respectively) does not confer stability, but a car-
boxamide group at the 4-position does (31). Further-
more, contrary to the findings with the nitriles, turnover
is reduced when a carboxamide is introduced at the
3-position (32). Pharmacokinetic studies in rat con-
firmed the correlation of turnover with bioavailability.
Thus, 31 and 32 were found to have bioavailability
comparable with that of 26 (Table 2). It was anticipated
that brain penetration of these amides would be com-
promised relative to nitrile because of the increased
polarity and increased H-bonding capability of the
carboxamide.22 Blood and brain levels of 31 and 26
measured following po dosing to mice confirmed this. A
brain/blood ratio of 10 was obtained for the nitrile 26
compared with 0.3 for the carboxamide 31. Neverthe-
less, high brain levels were obtained with both com-
pounds in mouse 30 min following po dosing at 1 mg/kg
(26, brain 406 ng/mL, plasma 41ng/mL; 31, brain 135
ng/mL, plasma 397 ng/mL), indicating suitability for use
in animal behavioral studies.

4-(Phenylsulfonyl)piperidines
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 495
Ta ble 2. Rat Pharmacokinetics
Ch a r t 3. Effect of 5-HT2A Receptor Antagonists on QTc
Interval in the Anaesthetised Ferretc
a
Cmax
AUCb ng Fc
Cld mL
Vde Mrtf dose
compd ng/mL h mL-1
%
min-1 kg-1 L/kg
h
mg/kg
2
5
7
2
2
2
8
4
3
3
1
77
53
4.6
4.9
1.0
1.5
1.2
1.5
2.0
2.0
10
1
2
2
1
1
11
12
26
27
28
31
32
35
1
1
23
30
0
100
177
0
2
23
34
20
2.0
2.8
1.0
2.3
0
0
70
38
140
199
115
171
22
24
30
19
36
29
1.0
2.3
1.2
0.9
1.1
0.7
1
a
b
Maximum blood concentration after oral dosing. Area under
a
b
Infusion dose (mg kg-1 h-1). Line showing 10% increase in
the concentration-time curve for 0-4 h after oral dosing. c Bio-
QTc interval. c Error bars show standard error of the mean of three
determinations.
d
availability calculated from dosing iv and po. Clearance from
plasma calculated following iv dosing. e Volume of distribution
calculated from dosing iv. f Mean residence time following iv
dosing.
on the QTc interval in the anesthetized ferret following
iv infusion (Chart 3). The ferret model was developed
as an alternative to the dog for simplicity and to reduce
the amount of compound required for evaluation. The
studies showed that 12, 26, and 31 caused a significant
prolongation of the QTc interval (>10% increase). Since
it is not currently clear what level of receptor occupancy
of 5HT2A receptors would be required therapeutically,
the QTc data obtained for 12, 26, and 31 cannot be used
to establish a safety margin between the QTc interval
and 5HT2A activity. A better option is to eliminate QTc
prolongation in vivo. This was achieved with compound
35, which had no significant effect on the QTc interval
following infusion dosing up to 10 mg kg-1 h-1. Phar-
macokinetic evaluation of 35 showed the compound to
be orally bioavailable in rat (F, 30% (Table 2)).
Ch a r t 1. Stability of Spirocyclic Ether Derivatives in
the Presence of Rat Liver Microsomesa
a
See Experimental Section for details.
Ch a r t 2. Stability of Sulfone Derivatives toward Rat
Ch em istr y
Liver Microsomesa
Spirocyclic derivatives 5,23 7,21 22,21 55,24 57,23 and
5923 have been reported previously. Compounds 8, 9,
16-21, and 23-25 were prepared in a manner similar
to that described for 5 as shown in Scheme 1. The des-
oxy derivative 10 was obtained by reduction of alcohol
58 using triethylsilane in TFA (Scheme 2). Spirocyclic
sulfone 11 was prepared from the previously reported
thioether 59,23 as outlined in Scheme 3. The 4-(phenyl-
sulfonyl)piperidine derivatives (12-15 and 26-35) were
prepared as shown in Scheme 4. The thioethers (64a -
f) were initially obtained via condensation of N-BOC
4-piperidinol (62) with diphenyl disulfide in the presence
of tributylphosphine.25 Subsequently alkylation of the
appropriate thiophenol with N-BOC 4-mesyloxypiperi-
dine (63)20 was employed. Oxidation to the sulfones
(65a -f) was best achieved using oxone on alumina in
CH2Cl2 in accordance with the method of Greenhalgh.26
Deprotection with HCl afforded piperidines 66a -f as
precursors for alkylation.
a
See Experimental Section for details.
To identify bioavailable analogues with reduced IKr
activity, the alternative approach to exploring N sub-
stitution was investigated. Preparation of the 4-(phe-
nylsulfonyl)piperidine analogues of the stable spirocyclic
ethers 21 and 23 gave 33 and 34, respectively. Com-
pound 33 lacked affinity for the 5-HT2A receptor, but
moderate affinity was observed with 34 (Ki h5-HT2A, 15
nM). Since the earlier comparison of binding data for
13-15 suggested a two-carbon linker to be optimal for
high 5-HT2A binding affinity, 35 (the lower homologue
of 34) was prepared. This led to enhanced affinity for
both human and rat 5-HT2A receptors (Ki of h5-HT2A
2.4 nM) and good selectivity over other receptors includ-
ing enhanced selectivity over IKr (Table 1).
To confirm that the reduction in IKr binding affinity
had pharmacological significance, studies were carried
out to investigate the effect of the compounds in vivo
Biology
Compounds were evaluated for displacement of [3H]-
ketanserin binding to human 5HT2A receptors27 stably
expressed in Chinese hamster ovary (CHO) cells, [3H]-
mesurgeline binding to human 5-HT2C receptors stably
expressed in CHO cells, [3H]-spiperone binding to CHO
cells stably expressing hD2 receptors,28 [3H]-prazosin
binding to rat cortical membranes,29 and [3H]-dofetilide
binding to HEK cells stably expressing hERG, which
encodes the IKr potassium channel. For h5-HT2A recep-
,

496 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2
Fletcher et al.
Sch em e 1a
a
Reagents: (i) pyrrolidine, EtOH, room temp, 18 h; (ii) borane/THF, reflux, 16 h; (iii) 5 N HCl, reflux, 2.5 h; (iv) RX, K2CO3, CH3CN,
reflux, 10 h; (v) Pd/C, H2 (55psi), EtOH, 1 N HCl, 8 h.
Sch em e 2a
Sch em e 3a
a
Reagents: (i) 2,4-difluorophenethyl bromide, K2CO3, CH3CN,
reflux, 15 h; (ii) NaBH4, EtOH, room temp, 12 h; (iii) Et3SiH, TFA,
CH2Cl2, room temp.
a
Reagents: (i) 30% H2O2, HOAc, 90 °C, 2 h; (ii) NaBH4, EtOH;
(iii) p-toluenesulfonic acid, toluene, reflux, 72 h; (iv) 6 N HCl, 90
°C, 12 h; (v) 2,4-difluorophenethyl bromide, K2CO3, CH3CN, reflux,
18 h; (vi) Pd/C, H2 (55psi), EtOH, 18 h.
tors, the Ki values are quoted as the geometric mean of
at least three separate determinations, and the errors
of the mean are within 2-fold of the mean. In counter-
screening binding assays, Ki values are the geometric
mean of at least two independent determinations (Table
1). In a functional assay, compounds were evaluated for
their effect alone (agonist activity) and their ability to

4-(Phenylsulfonyl)piperidines
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 497
Sch em e 4a
a
Reagents: (i) nBu3P, PhSSPh, THF, reflux, 48 h; (ii) ArSH, K2CO3, CH3CN, reflux, 18 h; (iii) oxone, wet alumina, CHCl3, reflux, 18
h, (iv) 5 N HCl, MeOH, reflux, 3 h; (v) RX, K2CO3, CH3CN, reflux, 18 h; (vi) CuCN, N-methylpyrrolidinone, reflux, 16 h; (vii) 85% H2SO4,
100 °C, 30 min; (viii) CO, Pd(OAc)2, MeOH; (ix) NH4Cl, Me3Al, toluene, reflux, 18 h.
block (antagonist activity) 5HT (1 µM) mediated ac-
cumulation of inositol phosphates in CHO cells stably
expressing h5-HT2A receptors.27,30
in man, is not significant with this derivative. These
compounds thus provide the opportunity of determining
the therapeutic potential of selective 5-HT2A receptor
antagonists.
The methodology for determination of compound
stability toward rat liver microsomes is described in the
Experimental Section. The results shown in Charts 1
and 2 are expressed as the percent of material remain-
ing after incubation for 30 min, with each determination
carried out three times. Methods for determination of
pharmacokinetics (Table 2) are also included in the
Experimental Section.
Exp er im en ta l Section
Melting points were taken on a Reichert Thermovar ap-
paratus and are uncorrected. Proton NMR spectra were
recorded on Bruker DPX 400, AM 360, and AC 250 spectrom-
eters, and chemical shifts are reported in parts per million (δ)
downfield from tetramethylsilane as internal standard. Mass
spectra were recorded on a VG 70/250 spectrometer. Merck
Kieselgel (230-400) mesh (silica) was used as bought from
Aldrich. Reactions were carried out under nitrogen, and
organic solutions were dried with anhydrous magnesium
sulfate unless indicated otherwise. Elemental analyses were
determined by Butterworth Laboratories, Ltd., Teddington,
Middlesex, U.K. Compounds 36-42 and 56 were obtained
commercially.
The QTc interval was determined in the anesthetized
ferret for assessment of IKr activity in vivo. Changes
in QTc interval were measured following infusion dosing
at increased dose levels (0.3, 1, 3, and 10 mg kg-1 h-1
)
administered sequentially over three time periods (30
min) in triplicate (Chart 3).
1′-[2-(2,4-Diflu or op h en yl)et h yl]-3,4-d ih yd r osp ir o[2H-
1-ben zop yr a n -2,4′-p ip er id in e] (8). To a mixture of 3,4-
dihydrospiro[2H-1-benzopyran-2,4′-piperidine] hydrochloride
(55)24 (0.37 g, 1.5 mmol) and 2,4-difluorophenylacetic acid (0.39
g, 2.2 mmol) in DMF (20 mL) stirring at room temperature
were added HOBt (0.31 g, 2.2 mmol), EDCI (0.44 g, 2.2.mmol),
and Et3N (0.63 mL, 3.8 mmol). The mixture was stirred at
room temperature for 24 h and partitioned between EtOAc (3
× 25 mL) and water (25 mL). The organic phase was dried
and concentrated, and the residue was purified by column
chromatography (silica; EtOAc/isohexane 1:3 f 1:1) to give
the intermediate amide as a gummy solid (0.29 g, 54%). MS
m/z (ES+): 358 (M + H+). This was dissolved in THF (10 mL),
and LAH powder (60 mg, 1.6 mmol) was added in one portion
at room temperature. After the mixture was stirred for 2 h,
20% KOH solution (3 mL) was added and the mixture
partitioned between EtOAc and water. The residue obtained
Con clu sion s
On the basis of the spirocyclic ether screening lead
5, a series of acyclic sulfones have been identified as
high-affinity, selective 5-HT2A receptor antagonists. Oral
bioavailability, initially lacking in the unsubstituted
derivative 12, has been achieved through aromatic
substitution with cyano- or carboxamide groups leading
to compounds such as 26 and 31. The compounds have
high affinity at both rat and human cloned 5-HT2A
receptors and are brain-penetrant. Thus, they represent
useful tools for the evaluation of 5-HT2A antagonists in
CNS related animal models. N substitution based on
12 also gives rise to bioavailable derivatives such as 35.
IKr activity, which may lead to cardiac dysrhythmias

498 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2
Fletcher et al.
on workup was purified by column chromatography (silica;
EtOAc/isohexane 1:1 f 1:0), and the product was converted
to the hydrochloride salt using 1 M HCl solution in ether to
give 8 (110 mg, 36%). Mp 252-4 °C. 1H NMR δΗ (360 MHz,
CDCl3): 1.64-1.72 (2H, m), 1.78-1.88 (4H, m), 2.50-2.57 (2H,
m), 2.60-2.64 (2H, m), 2.73-2.90 (6H, m), 6.73-6.84 (4H, m),
at 90 °C for 2 h, cooled to room temperature, and concentrated
1
to
/ the volume in vacuo. The mixture was partitioned
3
between water (20 mL) and CH2Cl2 (3 × 100 mL). The
combined organic phase was washed with saturated sodium
thiosulfate solution (20 mL) and brine and dried over sodium
sulfate, filtered, and concentrated to yield a yellow gum (4.2
g), which was dissolved in EtOH (25 mL) at room temperature
under nitrogen. Sodium borohydride (0.65 g, 17 mmol) was
added portionwise, and the mixture was stirred for 12 h at
room temperature. Saturated ammonium chloride solution (50
mL) was then added followed by CH2Cl2 (200 mL). The phases
were separated, and the aqueous phase was extracted with
CH2Cl2 (×2). The combined organic phases were washed with
brine, dried over sodium sulfate, filtered, and concentrated to
yield a semisolid (MS m/z (ES+): 371 (M + H+)), which was
dissolved in toluene (50 mL). p-Toluenesulfonic acid (200 mg)
was added, and the resulting mixture was stirred and heated
at reflux for 72 h. After cooling to room temperature, the
solution was partitioned between saturated sodium carbonate
(20 mL) and CH2Cl2 (100 mL) and the phases were separated.
After extraction with CH2Cl2 (×2) the organic phases were
combined, washed with brine, dried over sodium sulfate,
filtered, and concentrated to yield a yellow syrup (4.2 g), which
was dissolved in EtOH (100 mL), and 6 N HCl (25 mL) was
added. The mixture was heated at 90 °C for 12 h, cooled to
room temperature, concentrated, and azeotroped with toluene
(50 mL) to yield a semisolid that was recrystallized from
methanol to give 60 as a colorless solid. 1H NMR δΗ (free base,
360 MHz, CDCl3): 1.79-1.89 (3H, m), 2.09-2.21 (2H, m),
2.80-2.93 (2H, m), 3.13-3.21 (2H, m), 6.38 (1H, d J ) 11.8
Hz), 6.68 (1H, d J ) 11.8 Hz), 7.28 (1H, d J ) 8.1 Hz), 7.42-
7.61 (2H, m), 8.01 (1H, d J ) 8.1 Hz). A mixture of 60 (0.5 g,
1.7 mmol), 2,4-difluorophenethyl bromide (0.39 g, 1.8 mmol),
and K2CO3 (0.48 g, 3.4 mmol) in CH3CN (20 mL) was heated
at reflux for 18 h. The reaction mixture was then concentrated
and partitioned between EtOAc and water. The residue
obtained from the organic phase was purified by column
chromatography (silica; CH2Cl2/MeOH 99:1 f 95:5) to give 61
7.03-7.26 (3H, m). MS m/z (ES+): 344 (M + H+). Anal. (C21H24
-
ClF2NO) C, H, N.
3,4-Dih yd r o-1′-[2-p h en yleth yl]sp ir o[2H-1-ben zop yr a n -
2,4′-p ip er id in e] (9). Compound 5524 (0.7 g, 2.9 mmol) was
added in one portion to a mixture of phenethyl bromide (0.4
mL, 2.9 mmol), anhydrous K2CO3 (0.81 g, 5.8 mmol), and NaI
(0.48 g, 3.2 mmol) in acetonitrile (10 mL), and the resulting
slurry was heated at 85 °C for 18 h. The mixture was then
partitioned between EtOAc (4 × 15 mL) and water (15 mL).
The organic phase was dried and concentrated, the residue
was purified by column chromatography (silica; EtOAc/iso-
hexane 1:3 f 1:1), and the product was converted to the
hydrochloride salt using 1 M HCl solution in ether to give 9
1
(194 mg, 19%). Mp 275-6 °C. H NMR δΗ (360 MHz, CDCl3):
1.64-1.72 (2H, m), 1.75-1.88 (4H, m), 2.48-2.54 (2H, m),
2.63-2.67 (2H, m), 2.72-2.85 (6H, m), 6.77-6.84 (2H, m),
7.03-7.10 (2H, m), 7.16-7.29 (5H, m). MS m/z (ES+): 308 (M
+ H+). Anal. (C21H26ClNO) C, H, N.
1′-[2-(2,4-Diflu or oph en yl)eth yl]-3,4-dih ydr ospir o[n aph -
th a len e-2(1H),4′-p ip er id in e] (10). To a solution of keto-
spiropiperidine 5723 (0.92 g, 43 mmol) in acetonitrile (50 mL)
was added potassium carbonate (1.48 g, 11 mmol) followed by
sodium iodide (0.77 g, 5.1 mmol) and 2,4-difluorophenethyl
bromide (1.13 g, 5.1 mmol), and the mixture was heated under
nitrogen for 15 h while stirring. After cooling to room tem-
perature, the reaction mixture was partitioned between water
(20 mL) and EtOAc (100 mL) and the phases were separated.
The aqueous layer was extracted again with EtOAc (50 mL),
and the organic phases were combined, washed with brine (20
mL), dried (Na2SO4), filtered, and adsorbed onto silica gel (20
g). Flash chromatography yielded 0.52 g (35%) of the desired
ketone intermediate (MS m/z (ES+): 355 (M + H+)) as a yellow
semisolid, which was dissolved in ethanol (10 mL), and sodium
borohydride (0.4 g, 10.6 mmol) was added under nitrogen over
1 min at room temperature. Stirring was continued for 12 h,
and the reaction was quenched with saturated aqueous am-
monium chloride solution (20 mL). The mixture was concen-
trated under vacuum and the mixture partitioned between
EtOAc and water (50 mL/20 mL). After separation of the
organic phase, the aqueous phase was extracted twice and the
organic phases were combined, washed with brine (10 mL),
dried (Na2SO4), filtered, and evaporated to give 0.5 g of a syrup
that was purified via column chromatography to yield 0.2 g
1
(0.33 g, 47%) as an oil. H NMR δΗ (360 MHz, CDCl3): 1.75-
1.89 (2H, m), 2.29-2.40 (4H, m), 2.59-2.63 (2H, m), 2.77-
2.82 (2H, m), 2.93-3.00 (2H, m), 6.31 (1H, d, J ) 10 Hz), 6.64
(1H, d, J ) 10 Hz), 6.72-6.80 (2H, m), 7.13-7.19 (1H, m), 7.27
(1H, d, J ) 7 Hz), 7.48 (1H, t, J ) 7 Hz), 7.58 (1H, t, J ) 7
Hz), 8.00 (1H, d, J ) 7 Hz). A solution of 61 (0.18 g, 0.46 mmol)
in EtOH (20 mL) was shaken with 10% palladium-on-carbon
(0.05 g) on a Parr hydrogenator at 55 psi of H2 for 18 h. The
catalyst was then removed by filtration and the filtrate
concentrated. The residue was purifed by column chromatog-
raphy (silica; CH2Cl2/MeOH 99:1 f 95:5) followed by recrys-
tallization from EtOAc to give 11 (0.078 g, 43%). HCl salt,
colorless solid; mp 218-20 °C. 1H NMR δΗ (400 MHz, CDCl3):
1.75-1.82 (2H, m), 2.29-2.47 (6H, m), 2.56-2.67 (2H, m),
2.75-2.82 (2H, m), 2.90-3.05 (4H, m), 6.72-6.80 (2H, m),
7.08-7.21 (2H, m), 7.35-7.50 (2H, m), 7.95 (1H, d, J ) 8 Hz).
MS m/z (ES+): 392 (M + H+). Anal. (C21H24ClF2NO2S) C, H,
N.
1
(37%) of alcohol 58 as a foam. H NMR δΗ (360 MHz, CDCl3):
1.19-1.73 (4H, m), 1.92-2.04 (2H, m), 2.48-2.95 (10H, m),
4.38 (1H, broad s), 6.74-6.84 (2H, m), 7.12-7.26 (4H, m),
7.33-7.36 (1H, m).
To a solution of 58 (0.2 g, 0.56 mmol) in CH2Cl2 (5 mL) was
added trifluoroacetic acid (0.25 mL, 3.2 mmol) followed by
triethylsilane (0.4 mL, 5.6 mmol), and the solution was heated
under nitrogen for 12 h while stirring. After cooling to room
temperature, the reaction mixture was concentrated and
partitioned between 2 N NaOH (20 mL) and chloroform (100
mL) and the phases were separated. The aqueous layer was
extracted again with chloroform (50 mL), and the organic
phases were combined, washed with brine (20 mL), dried over
sodium sulfate, filtered, and adsorbed onto silica gel (10 g).
Flash chromatography yielded 10 (0.07 g, 37%) as a colorless
semisolid. HCl salt, mp 270-2 °C. 1H NMR δΗ (360 MHz,
CDCl3): 1.19-1.73 (4H, m), 1.92-2.04 (2H, m), 2.48-2.95
(10H, m), 4.38 (1H, broad s), 6.74-6.84 (2H, m), 7.12-7.26
(4H, m), 7.33-7.36 (1H, m). MS m/z (ES+): 342 (M + H+).
Anal. (C22H26ClF2N‚0.5H2O) C, H, N.
1-(2-(2,4-Diflu or op h en yl)eth yl)-4-(p h en ylsu lfon yl)p ip -
er id in e (12). a . N-BOC 4-(P h en ylth io)p ip er id in e (64a ).
Tri(n-butyl)phosphine (7.4 mL, 0.045 mol) was added to a
solution of N-BOC 4-hydroxypiperidine (62) (4.0 g, 0.02 mol)
and diphenyl disulfide (6.5 g, 0.03 mol) in dry THF (20 mL) at
room temperature, and the resulting mixture was heated at
reflux for 48 h. The mixture was then partitioned between
EtOAc (3 × 40 mL) and 2 N NaOH (40 mL). The organic phase
was washed with brine, dried, and concentrated to give 64a
(3.3 g, 54%) as a solid after trituration with isohexane.
b. N-BOC 4-(P h en ylsu lfon yl)p ip er id in e (65a ). Water (10
mL) was added to alumina (50 g), which was slurried (5 min),
and chloroform (100 mL) added followed by a solution of 64a
(15.8 g, 54 mmol) in chloroform (200 mL). Oxone (100 g, 0.16
mol) was added, and the resulting slurry was stirred and
heated at reflux for 18 h. After cooling to room temperature,
1′-[2-(2,4-Diflu or op h en yl)et h yl]-3,4-d ih yd r osp ir o[2H-
1-ben zoth iop yr a n -2,4′-p ip er id in e]-1,1-d ioxid e (11). Com-
pound 5923 (4.13 g, 12 mmol) was dissolved in glacial acetic
acid (20 mL) at room temperature, and 30% aqueous hydrogen
peroxide (5 mL) was added. The resulting solution was heated

4-(Phenylsulfonyl)piperidines
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 499
the mixture was filtered and the mother liquor washed with
water, dried, and evaporated to give 65a (16.2 g) as a colorless
solid.
0.054 mol) and heated at reflux for 16 h. The solution was then
cooled, treated with 5 N HCl (200 mL), and refluxed for a
further 3.5 h. The resulting solution was concentrated, basified
with 2 N NaOH solution, and extracted into CH2Cl2 (3 × 50
mL). The residue obtained from the organic extracts was
purified by column chromatography (silica; CH2Cl2/MeOH 9:1
f CH2Cl2/MeOH/NH3 90:10:1) to give 47 (1.31 g, 67%) as an
orange oil. 1H NMR δΗ (360 MHz, CDCl3): 1.66-1.78 (2H, m),
1.98-2.01 (2H, m), 2.87-2.94 (2H, m), 3.07-3.25 (3H, m),
5.63-5.66 (1H, d, J ) 10 Hz), 6.57-6.66 (3H, m), 6.99-7.01
(1H, d, J ) 8 Hz). A mixture of 47 (0.5 g, 2.28 mmol), 2,4-
difluorophenethyl bromide (0.656 g, 2.97 mmol), and K2CO3
in CH3CN (7 mL) was heated at reflux for 10 h. The mixture
was then concentrated and partitioned between water (15 mL)
and CH2Cl2 (2 × 15 mL). The residue obtained from the organic
phase was purified by column chromatography (silica; CH2-
Cl2/MeOH 97:3) to give 51 (0.54 g, 65%), a tan solid. Mp 55-7
c. 4-(P h en ylsu lfon yl)p ip er id in e (66a ). N-BOC 4-(phen-
ylsulfonyl)piperidine (65a ) (5.6 g, 0.0175 mol) was dissolved
in methanol (50 mL) and 5 N HCl (10 mL) and heated at reflux
for 3 h. After a warm filtration to remove insolubles, the
solution was poured into saturated aqueous sodium carbonate
solution and extracted with CH2Cl2 to afford 3.2 g of a colorless,
gummy solid as the free base. Trituration with diethyl ether
afforded 66a (3.0 g) as a colorless solid. 1H NMR δΗ (360 MHz,
CDCl3): 1.52-1.64 (2H, m), 1.98 (2H, broad d, J ) 10 Hz),
2.34 (1H, s), 2.49-2.59 (2H, m), 2.98-3.07 (1H, m), 3.19 (2H,
broad d, J ) 10 Hz), 7.42-7.59 (2H, m), 7.59-7.66 (1H, m),
7.87 (2H, d, J ) 4.7 Hz). A mixture of 66a (0.63 g, 2.8 mmol),
2,4-difluorophenethyl bromide (0.74 g, 0.0033 mol), K2CO3
(0.77 g, 5.6 mmol), and NaI (0.5 g, 3.3 mmol) in CH3CN (15
mL) was heated at reflux under nitrogen for 18 h. The reaction
mixture was then concentrated and partitioned between water
and EtOAc. The organic phase was washed with brine, dried
(Na2SO4), and concentrated. Column chromatography (silica;
isohexane/EtOAc 3:1) gave 12 (0.4 g, 39%) as a colorless solid.
Mp 86-87 °C. 1H NMR δΗ (360 MHz, CDCl3): 1.66-1.77 (2H,
m), 1.96-2.04 (4H, m), 2.49-2.53 (2H, m), 2.71-2.75 (2H, m),
2.86-2.95 (1H, m), 3.03-3.07 (2H, m), 6.72-6.80 (2H, m),
7.08-7.15 (1H, m), 7.54-7.59 (2H, m), 7.64-7.68 (1H, m), 7.87
1
°C. H NMR δΗ (360 MHz, CDCl3): 1.74-1.80 (2H, m), 2.03-
2.07 (2H, m), 2.53-2.69 (6H, m), 2.84-2.97 (2H, m), 5.61-
5.63 (1H, d, J ) 10 Hz), 6.56-6.63 (3H, m), 6.74-6.82 (2H,
m), 7.01-7.06 (1H, dd, J ) 7 and 7 Hz), 7.14-7.18 (1H, m).
MS m/z (ES+): 360 (M + H+). Anal. (C21H20F3NO‚0.075H2O)
C, H, N. A solution of 51 (0.394 g, 1 mmol) in 1 N HCl (2 mL)
and EtOH (7 mL) was shaken on a Parr hydrogenator at 55
psi of hydrogen in the presence of 10% palladium-on-carbon
(0.1 g) for 8 h. The catalyst was removed by filtration, the
filtrate concentrated, and the residue purified by recrystalli-
zation from EtOH to give 16 (0.39 g, 99%) as the HCl salt. Mp
216-8 °C. 1H NMR δΗ (360 MHz, CDCl3): 1.91-1.95 (2H, t, J
) 6.5 Hz), 2.01-2.05 (2H, m), 2.54 (2H, m), 2.75-2.79 (2H, t,
J ) 6.5 Hz), 3.18 (4H, broad s), 3.34 (2H, broad s), 3.46 (2H,
m), 6.27-6.61 (2H, dd, J ) 8 and 8 Hz), 6.80-6.87 (2H, m),
7.05-7.11 (1H, m), 7.35-7.36 (1H, m). MS m/z (ES+): 362 (M
+ H+). Anal. (C21H22F3NO‚HCl) C, H, N.
(2H. d J ) 4.2 Hz). MS m/z (ES+): 366 (M + H+). Anal. (C19H22
ClF2NO2S) C, H, N.
-
1-(2-P h en yleth yl)-4-(p h en ylsu lfon yl)p ip er id in e (13). A
mixture of 66a (0.2 g, 0.88 mmol), phenethyl iodide (0.13 mL,
0.88 mmol), and K2CO3 in CH3CN (20 mL) was stirred and
heated at reflux for 18 h. The solvent was then evaporated
and the residue partitioned between EtOAc and water. The
residue obtained from workup was purified by column chro-
matography (silica; CH2Cl2 f CH2Cl2/MeOH 97:3) followed by
recrystallization from EtOAc to give 13 (0.17 g, 59%) as a
Similarly prepared from the appropriate acetophenone were
the following.
1
colorless solid. Mp 116-8 °C. H NMR δΗ (400 MHz, CDCl3):
1′-[2-(2,4-Diflu or op h en yl)et h yl]-3,4-d ih yd r o-7-flu or o-
sp ir o[2H -1-b en zop yr a n -2,4′-p ip er id in e] Hyd r och lor id e
1.66-1.77 (2H, m), 1.96-2.04 (4H, m), 2.52-2.62 (2H, m),
2.71-2.75 (2H, m), 2.86-2.95 (1H, m), 3.03-3.07 (2H, m),
7.14-7.20 (3H, m), 7.20-7.30 (2H, m), 7.54-7.59 (2H, m),
7.64-7.68 (1H, m), 7.88 (2H, d, J ) 7 Hz). MS m/z (ES+): 330
(M + H+). Anal. (C19H23NO2S) C, H, N.
1
(17). Mp 240-3 °C. H NMR δΗ (360 MHz, DMSO-d6): 1.82
(2H, m), 1.97 (4H, m), 2.74 (2H, m), 3.24 (4H, m), 3.32 (2H,
m), 3.48 (2H, m), 6.70 (2H, m), 7.12-7.14 (2H, m), 7.23-7.29
(1H, m), 7.44-7.46 (1H, m). MS m/z (ES+): 362 (M + H+).
Anal. (C21H22F3NO‚HCl) C, H, N.
Similarly prepared using the appropriate bromide were the
following.
1′-[2-(2,4-Diflu or oph en yl}eth yl]-6-flu or ospir o[2H-1-ben -
zop yr a n -2,4′-p ip er id in e] (18). Mp 102-3 °C. 1H NMR δΗ
(360 MHz, CDCl3): 1.75-1.78 (2H, m), 2.02-2.04 (2H, m),
2.54-2.63 (4H, m), 2.70 (2H, m), 2.80-2.84 (2H, m), 5.63-
5.66 (1H, d, J ) 10 Hz), 6.31-6.33 (1H, d, J ) 10 Hz), 6.68-
6.81 (5H, m), 7.14-7.23 (1H, m). MS m/z (ES+): 360 (M + H+).
Anal. (C21H20F3NO) C, H, N.
1-P h en ylm eth yl-4-(p h en ylsu lfon yl)p ip er id in e (14). 1H
NMR δΗ (360 MHz, DMSO-d6): 1.40-1.55 (2H, m), 1.70-1.80
(2H, m), 1.80-1.95 (2H, m), 2.83-2.90 (2H, m), 3.05-3.10 (1H,
m), 3.43 (2H, s), 7.16-7.32 (5H, m), 7.62-7.70 (2H, m), 7.70-
7.80 (1H, m), 7.84 (2H, d, J ) 7 Hz). MS m/z (ES+): 316 (M +
H+). Anal. (C18H21NO2S) C, H, N.
1′-[2-(2,4-Diflu or op h en yl)et h yl]-3,4-d ih yd r o-8-flu or o-
sp ir o[2H -1-b en zop yr a n -2,4′-p ip er id in e] Hyd r och lor id e
(19). H NMR δΗ (360 MHz, CDCl3): 1.97 (2H, m), 2.04-2.08
(2H, m), 2.57 (2H, m), 2.82 (2H, m), 3.2 (4H, broad s), 3.35
(2H, m), 3.46 (2H, m), 6.8-6.95 (5H, m), 7.34 (1H, m). MS m/z
(ES+): 362 (M + H+). Anal. (C21H22F3NO‚HCl) C, H, N.
1-(3-P h en ylp r op yl)-4-(p h en ylsu lfon yl)p ip er id in e (15).
1H NMR, free base δΗ (360 MHz, CDCl3): 1.40-1.55 (2H, m),
1.64-1.80 (2H, m), 1.88 (2H, t, J ) 12 Hz), 2.01 (2H, dd, J )
13 and 7 Hz), 2.31 (2H, t, J ) 7.5 Hz), 2.59 (2H, t, J ) 7.5 Hz),
2.84-2.93 (1H, m), 2.99 (2H, d, J ) 12 Hz), 7.13-7.18 (3H,
m), 7.20-7.28 (2H, m), 7.54-7.58 (2H, m), 7.63-7.71 (1H, m),
7.86 (2H, d, J ) 7 Hz). MS m/z (ES+): 344 (M + H+). Anal.
(C20H25NO2S) C, H, N.
1′-[2-(2,4-Diflu or op h en yl)et h yl]-3,4-d ih yd r o-5-flu or o-
sp ir o[2H-1-ben zop yr a n -2,4′-p ip er id in e] (16). A solution of
6-fluoro-2-hydroxyacetophenone (40) (4.4 g, 0.029 mol) and
pyrrolidine (2.4 mL, 0.029 mol) in MeOH (20 mL) was stirred
at room temperature for 15 min. N-BOC 4-piperidone (42) (5.7
g, 0.029 mol) was added portionwise, and the resulting solution
was stirred at room temperature for 24 h. The mixture was
concentrated and partitioned between EtOAc (3 × 40 mL) and
2 N HCl (40 mL). The organic phase was washed with 1 N
NaOH and brine, dried, and concentrated to give 43 (3.0 g,
31%), a yellow oil that was used without further purification.
1H NMR δΗ (250 MHz, CDCl3): 1.46 (9H, s), 1.56-1.69 (2H,
m), 2.0 (2H, s), 2.72 (2H, s), 3.16-3.26 (2H, m), 3.80-3.96 (2H,
m), 6.70 (1H, dd, J ) 8, 9 Hz), 6.80 (1H, d, J ) 8 Hz), 7.37-
7.47 (1H, m). A solution of 43 in THF (100 mL) was treated
with a solution of borane/THF complex in THF (1 M, 54 mL,
1
1′-(2-(2,4-Diflu or oph en yl)eth yl)-3,4-dih ydr o-4-oxospir o-
[2H-1-ben zopyr an -2,4′-piper idin e]-6-car bon itr ile (20). Pyr-
rolidine (0.082 mL) was added to a solution of 36 (0.16 g, 1
mmol) in EtOH (5 mL) at room temperature. After 15 min 41
(0.24 g, 1 mmol) was added and the mixture was stirred at
room temperature for 18 h. A 2 N HCl (5 mL) solution was
added, and the mixture was concentrated. The residue was
partitioned between CH2Cl2 and NaOH. The residue obtained
after workup was purified by column chromatography (silica;
EtOAc) to give 20 (0.73 g, 20%) as a colorless solid. Mp 125-7
1
°C. H NMR δΗ (360 MHz, CDCl3): 1.74-1.83 (2H, m), 2.04-
2.07 (2H, m), 2.46-2.54 (2H, m), 2.59-2.63 (2H, m), 2.70-
2.84 (6H, m), 6.74-6.85 (2H, m), 7.08-7.19 (2H, m), 7.69-
7.73 (1H, dd, J ) 3 and 8 Hz), 8.18 (1H, d, J ) 3 Hz). MS m/z
(ES+): 383 (M + H+). Anal. (C22H20F2N2O2) C, H, N.
3,4-Dih yd r o-6-m eth oxy-1′-[2-(2-oxo-1-im id a zolid in yl)-
eth yl]sp ir o[2H-1-ben zop yr a n -2,4′-p ip er id in e] (21). A mix-
ture of 5624 (0.23 g, 1 mmol), N-(2-chloroethyl)imidazolidino-

500 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2
Fletcher et al.
ne31 (0.16 g, 1.1 mmol), K2CO3 (0.15 g, 1.1 mmol), and KI (0.18
g, 1.1 mmol) in DMF (10 mL) was heated at 80 °C for 18 h.
The mixture was then cooled and partitioned between water
(50 mL) and EtOAc (3 × 50 mL). The organic extracts were
washed with brine, dried, and concentrated to give a solid that
was purified by recrystallization from EtOAc to give 21 (0.072
g, 21%), a colorless solid. Mp 118-9 °C. 1H NMR δΗ (360 MHz,
CDCl3): 1.57-1.65 (2H, m), 1.65-1.85 (4H, m), 2.45-2.57 (4H,
m), 2.64-2.76 (4H, m), 3.32-3.42 (4H, m), 3.50-3.55 (2H, m),
3.75 (3H, s), 4.36 (1H, s), 6.59 (1H, d, J ) 3 Hz), 6.67 (1H, dd,
J ) 3 and 8 Hz), 6.74 (1H, d, J ) 8 Hz). MS m/z (ES+): 346
(M + H+). Anal. (C19H27N3O3) C, H, N.
3,4-Dih yd r o-6-m et h oxy-1′-[4-oxo-4-(4-flu or op h en yl)-
bu tyl]sp ir o[2H-1-ben zop yr a n -2,4′-p ip er id in e] (23). A mix-
ture of 5624 (0.5 g, 2.1 mmol), 2-(4-fluorophenyl)-2-(1-chloro-
3-propyl)-1,3-dioxolane (0.61 g, 2.5 mmol), K2CO3 (0.3 g, 2.2
mmol), and KI (0.32 g, 2.2 mmol) in CH3CN (20 mL) was
heated at reflux under nitrogen for 18 h. The reaction mixture
was concentrated, and the syrup obtained (MS m/z (ES+) 442
(M + H+)) was dissolved in a mixture of EtOH (10 mL) and 3
N HCl (10 mL). After being heated at reflux for 2 h, the
mixture was cooled to room temperature and the resulting
precipitate collected to give 23 as a colorless solid. Mp 210-2
°C. 1H NMR δΗ (360 MHz, CDCl3): 1.91 (2H, t, J ) 7 Hz),
1.98-2.02 (2H, m), 2.35-2.55 (4H, m), 2.78 (2H, t, J ) 7 Hz),
3.10-3.25 (4H, m), 3.27 (2H, t, J ) 7 Hz), 3.42-3.46 (2H, m),
3.75 (3H, s), 6.62 (1H, d, J ) 3 Hz), 6.69-6.77 (2H, m), 7.13-
7.18 (2H, m), 7.99-8.04 (2H, m). MS m/z (ES+): 398 (M + H+).
Anal. (C24H28FNO3‚HCl) C, H, N.
Oxone (250 g, 0.39 mol) was added and the resulting slurry
stirred and heated at reflux for 18 h. After cooling to room
temperature, the mixture was filtered and the mother liquor
washed with water, dried, and evaporated to give N-BOC 4-(4-
bromophenylsulfonyl)piperidine (65d ), 36 g (69%), as a color-
1
less solid. H NMR δΗ (360 MHz, CDCl3): 1.43 (9H, s), 1.5-
1.7 (2H, m), 1.9-2.0 (2H, m), 2.55-2.7 (2H, m), 2.9-3.1 (1H,
m), 4.15-4.25 (2H, m), 7.73 (4H. s). This material (36 g, 0.09
mol) was dissolved in a mixture of methanol (300 mL) and 5
N HCl (63 mL) and heated at reflux for 3 h. After a warm
filtration to remove insolubles, the solution was cooled to afford
the crystalline 4-(4-bromophenylsulfonyl)piperidine HCl salt
(66d ) (15.4 g), which was collected by filtration. Neutralization
of the mother liquor with sodium carbonate and extraction
with CH2Cl2 afforded 16 g of additional material, a colorless
1
solid, as the free base. H NMR, hydrochloride, δΗ (400 MHz,
DMSO-d6): 1.65-1.8 (2H, m), 1.95-2.05 (2H, m), 1.8-2.9 (2H,
m), 3.25-3.35 (2H, m), 3.6-3.7 (1H, m), 7.8 (2H, d, J ) 8 Hz),
7.9 (2H, d, J ) 8 Hz). Free base (360 MHz, CDCl3): 1.45-1.6
(2H, m), 1.95-2.0 (2H, m), 2.5-2.6 (2H, m), 2.95-3.05 (1H,
m), 3.15-3.25 (2H, m), 7.7 (4H, s). A mixture of 66d (7.6 g,
0.025mol), 2,4-difluorophenethyl bromide (8.3 g, 0.38 mol), K2-
CO3 (7.5 g, 0.054 mol), and NaI (5.6 g, 0.037 mol) in CH3CN
(70 mL) was heated at reflux under nitrogen for 18 h. The
reaction mixture was then concentrated and partitioned
between water and EtOAc. The organic phase was washed
with brine, dried (Na2SO4), and concentrated. Trituration with
hexane gave 6.5 g of N-(2,4-difluorophenethyl) 4-(4-bromophe-
1
nylsulfonyl)piperidine (67d ) as a colorless solid. H NMR δΗ
(360 MHz, CDCl3): 1.55-1.75 (2H, m), 1.95-2.05 (4H, m),
2.45-2.55 (2H, m), 2.7-2.75 (2H, m), 2.85-2.95 (1H, m), 3.05-
3.1 (2H, m), 6.7-6.85 (2H, m), 7.1-7.15 (1H, m), 7.72 (4H, s).
A mixture of 67d (2.2 g, 4.9 mmol) and copper(I) cyanide (2.3
g, 25 mmol) in N-methylpyrrolidinone (3 mL) was heated
under nitrogen at 160 °C for 16 h with stirring. The hot
solution was poured into water/CH2Cl2 (100 mL/200 mL), and
the organic phase was washed with water, dried (Na2SO4), and
evaporated to yield a syrup. Column chromatography (silica;
isohexane/EtAc 1:1) followed by recrystallization from EtOAc
yielded 26 (1.05 g, 55%). Mp 175-6 °C. 1H NMR δΗ (360 MHz,
CDCl3): 1.56-1.76 (2H, m), 1.97-2.04 (4H, m), 2.50-2.54 (2H,
m), 2.71-2.75 (2H, m), 2.90-2.97 (1H, m), 3.05-3.10 (2H, m),
6.72-6.80 (2H, m), 7.08-7.12 (1H, m), 7.87-7.89 (2H, m),
7.99-8.02 (2H, m). MS m/z (ES+): 391 (M + H+). Anal.
(C20H20F2N2O2S) C, H, N.
3,4-Dih ydr o-6-flu or o-1′-[2-h ydr oxy-4-ph en yl)bu tyl]spir o-
[2H-1-ben zop yr a n -2,4′-p ip er id in e] (24). A mixture of 54
(0.22 g, 1.0 mmol) and 2-(phenylethyl)oxirane (0.16 g, 1.1
mmol) in methanol (5 mL) was heated at reflux for 2 h. The
solvent was then evaporated and the residue purified by
column chromatography (silica; CH2Cl2/MeOH 98:2 f 95:5)
to give an oil that was converted to the hydrochloride salt using
1 N HCl in ether, giving 24 (0.28 g, 69%) as a colorless solid.
1
Mp 250-2 °C. H NMR δΗ (360 MHz, DMSO-d6): 1.35-1.45
(2H, m), 1.45-1.50 (2H, m), 1.50-1.80 (4H, m), 2.25-2.55 (4H,
m), 2.70-3.15 (6H, m), 3.60-3.75 (1H, m), 6.45-6.70 (3H, m),
6.80-7.00 (5H, m). MS m/z (ES+): 370 (M + H+). Anal. (C23H28
FNO2‚HCl) C, H, N.
-
3,4-Dih yd r o-6-flu or o-1′-(1,2,3,4-t e t r a h yd r o-2-n a p h -
th a len yl)sp ir o[2H-1-ben zop yr a n -2,4′-p ip er id in e] (25). A
mixture of 54 (0.25 g, 1.1 mmol), â-tetralone (0.26 mL, 1.6
mmol), and 4-toluenesulfonic acid (0.03 g) in toluene (50 mL)
was heated at reflux for 18 h. The reaction mixture was then
concentrated and redissolved in THF (20 mL). A 1 M solution
of HCl in ether (10 mL) was added followed by a solution of
sodium cyanoborohydride (0.1 g) in MeOH (10 mL). After 4 h,
further sodium cyanoborohydride was added (0.1 g) and the
mixture stirred at room temperature for 18 h. The reaction
mixture was then concentrated and partitioned between
EtOAc and water. The residue obtained on workup was purifed
by column chromatography (silica; CH2Cl2 f CH2Cl2/MeOH
95:5) to give 25 as an oil that was characterized as the HCl
salt. Mp 248-50 °C. 1H NMR δΗ (360 MHz, CDCl3): 1.22-
1.27 (4H, m), 1.48-1.52 (2H, m), 1.92-2.04 (2H, m), 2.61-
2.68 (1H, m), 2.78-2.81 (1H, m), 2.90-3.60 (5H, m), 3.69-
3.74 (4H, m), 6.76-6.86 (3H, m), 7.10-7.18 (4H, m). MS m/z
(ES+): 352 (M + H+). Anal. (C23H26FNO‚HCl) C, H, N.
Similarly prepared were the following.
3-[[1-(2-(2,4-Diflu or op h en yl)et h yl)-4-p ip er id in yl]su l-
fon yl]ben zon itr ile (27). Mp 138-9 °C. 1H NMR δΗ (360
MHz, CDCl3): 1.66-1.76 (2H, m), 1.95-2.10 (4H, m), 2.51-
2.54 (2H, m), 2.71-2.75 (2H, m), 2.90-2.97 (1H, m), 3.05-
3.10 (2H, m), 6.72-6.80 (2H, m), 7.08-7.15 (1H, m), 7.72 (1H,
t, J ) 8 Hz), 7.95 (1H, d, J ) 8 Hz), 8.12 (1H, d, J ) 8 Hz),
8.17 (1H, s). MS m/z(ES+): 391 (M +H+). Anal. (C20H20F2N2O2S)
C, H, N.
2-[[1-(2-(2,4-Diflu or op h en yl)et h yl)-4-p ip er id in yl]su l-
fon yl]ben zon itr ile (28). Mp 135-7 °C. 1H NMR δΗ (360
MHz, CDCl3): 1.78-1.90 (2H, m), 1.95-2.10 (4H, m), 2.51-
2.56 (2H, m), 2.72-2.76 (2H, m), 3.05-3.10 (2H, m), 3.20-
3.29 (1H, m), 6.72-6.80 (2H, m), 7.09-7.16 (1H, m), 7.78-
7.82 (2H, m), 7.94 (1H, d, J ) 8 Hz), 8.13 (1H, d, J ) 8 Hz).
MS m/z (ES+): 391 (M + H+). Anal. (C20H20F2N2O2S) C, H, N.
The following were prepared in a manner similar to that
described for 12, replacing diphenyl disulfide with the ap-
propriately substituted derivative.
1-(2-(2,4-Diflu or op h en yl)et h yl)-4-(4-flu or op h en ylsu l-
fon yl)p ip er id in e (29). Mp 136-7 °C. 1H NMR δΗ (400 MHz,
CDCl3): 1.59-1.75 (2H, m), 1.96-2.02 (4H, m), 2.49-2.54 (2H,
m), 2.70-2.75 (2H, m), 2.85-2.92 (1H, m), 3.07-3.17 (2H, m),
6.72-6.85 (2H, m), 7.08-7.18 (1H, m), 7.22-7.28 (2H, m),
7.85-7.92 (2H, m). MS m/z (ES+): 384 (M + H+). Anal.
(C19H20F3NO2S‚0.5H2O) C, H, N.
4-[[1-(2-(2,4-Diflu or op h en yl)et h yl)-4-p ip er id in yl]su l-
fon yl]ben zon itr ile (26). N-BOC 4-mesyloxypiperidine (63)20
(40 g, 0.14 mol), 4-bromothiophenol (32 g, 0.17 mol), and K2-
CO3 (30 g, 0.22 mol) were mixed at room temperature in CH3-
CN (300 mL) and heated at reflux for 18 h. Workup by
partitioning between water and EtOAc afforded 50 g (96%) of
N-BOC 4-(4-bromophenylthio)piperidine (64d ) as a yellow oil.
1H NMR δΗ (360 MHz, CDCl3): 1.44 (9H, s), 1.45-1.55 (2H,
m), 1.85-1.95 (2H, m), 2.85-2.95 (2H, m), 3.1-3.2 (1H, m),
3.95-4.05 (2H, m), 7.25-7.3 (2H, m), 7.4-7.45 (2H, m).
Water (26 mL) was added to alumina (130 g), the mixture
slurried (5 min), and chloroform (500 mL) added, followed by
a solution of 64d (50 g, 0.13 mol) in chloroform (300 mL).
4-(4-Ch lor op h en ylsu lfon yl)-1-(2-(2,4-d iflu or op h en yl)-
eth yl)p ip er id in e (30). Mp 135-6 °C. 1H NMR δΗ (360 MHz,
CDCl3): 1.59-1.75 (2H, m), 1.96-2.02 (4H, m), 2.49-2.54 (2H,

4-(Phenylsulfonyl)piperidines
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 501
m), 2.70-2.75 (2H, m), 2.86-2.95 (1H, m), 3.07-3.19 (2H, m),
6.72-6.80 (2H, m), 7.10-7.15 (1H, m), 7.54-7.56 (2H, d, J )
8.5 Hz), 7.79-7,81 (2H, d, J ) 8.5 Hz). MS m/z (ES+): 400,
402 (M + H+). Anal. (C19H20ClF2NO2S) C, H, N.
and DCM (100 mL). After separation of the phases, the
aqueous phase was extracted twice with DCM (20 mL) and
the combined organic phases were washed with brine, dried
over potassium carbonate, filtered, and concentrated. Column
chromatography (silica; isohexane/EtOAc 1:1) gave 34 (0.23
g, 59%) as a colorless solid. Mp 107-8 °C. 1H NMR δΗ (360
MHz, CDCl3): 1.57-1.67 (2H, m), 1.87-1.97 (6H, m), 2.33-
2.38 (2H, m), 2.83-2.98 (5H, m), 7.08-7.13 (2H, m), 7.54-
7.58 (2H, m), 7.64-7.68 (1H, m), 7.85 (2H, d J ) 5.8 Hz), 7.94-
7.97 (2H, m). MS m/z (ES+): 390 (M + H+). Anal. (C21H24FNO3S)
C, H, N.
1-(4-Flu or oph en yl)-2-[4-(ph en ylsu lfon yl)-1-piper idin yl]-
eth a n on e (35). A mixture of 66a (0.22 g, 1 mmol), 2-bromo-
4′-fluoroacetophenone (0.22 g, 1 mmol), and triethylamine (0.14
g, 1.4 mmol) in CH3CN (20 mL) was stirred at room temper-
ature for 18 h. The solvent then evaporated, and the residue
was partitioned between EtOAc and water. The residue
obtained from workup was purified by recrystallization from
CH3CN to give 35 (0.18 g, 50%). Mp 161-3 °C. 1H NMR δΗ
(400 MHz, CDCl3): 1.75-1.85 (2H, m), 2.00-2.05 (2H, m),
2.19-2.22 (2H, m), 2.89-2.98 (1H, m), 3.05-3.08 (2H, m), 3.74
(2H, s), 7.12 (2H, t, 8 Hz), 7.56 (2H, t, 8 Hz), 7.65-7.69 (1H,
m), 7.87 (2H, d, 8 Hz), 7.98-8.02 (2H, m). MS m/z (ES+): 362
(M + H+). Anal. (C19H20FNO3S) C, H, N.
5-HT2A Recep tor Bin d in g. Chinese hamster ovary (CHO)
cells stably expressing the human or rat 5-HT2A receptor were
lysed by homogenization in 50 mM Tris-HCl buffer (pH 7.5)
and centrifuged at 50000g for 10 min at 4 °C. The resulting
pellet was resuspended in assay buffer (50 mM Tris-HCl) at 2
mg wet weight/mL. Incubations were carried out in 96-well
plates for 15 min at 37 °C in the presence of 1 nM [3H]-
ketanserin (66.4 Ci/mmol, NEN) for displacement studies and
initiated by addition of 200 µL of membranes in a final assay
volume of 500 µL. The reaction was terminated by rapid
filtration over GF/B filters (presoaked in 0.1% BSA) and
washed with ice-cold 50 mM Tris-HCl buffer. Nonspecific
binding was determined with 1 µM Mianserin, and radioactiv-
ity was determined by counting on a Packard Topcount.
Binding parameters were determined by nonlinear least-
squares regression analysis from which the inhibition constant
Ki could be calculated for each compound.
5-HT2C Recep tor Bin d in g. Chinese hamster ovary cells
stably expressing the human 5-HT2C receptors were lysed by
homogenization in 50 mM Tris-HCl containing 0.1% ascorbate
and 10 µM pargyline, pH 7.7, centrifuged at 50000g for 10 min
at 4 °C, and the pellet was resuspended in assay buffer at 10
mg wet weight/mL. Incubations were performed for 30 min at
37 °C in the presence of 1 nM [3H]-mesulergine (77 Ci/mmol,
Amersham, U.K.) and initiated by addition of 400 µL of
membranes in a final assay volume of 500 µL. Nonspecific
binding was determined with 1 µM mianserin, and radioactiv-
ity was determined as described above for [3H]-ketanserin
binding studies.
4-[[1-(2-(2,4-Diflu or op h en yl)et h yl)-4-p ip er id in yl]su l-
fon yl]ben za m id e (31). A solution of 26 (0.5 g, 1.28 mmol) in
85% H2SO4 (10 mL) was heated at 100 °C for 30 min. The
cooled solution was diluted with water (40 mL) and neutralized
with solid KOH. At pH 7 a precipitate was collected and
dissolved in CH2Cl2. The organic phase was dried and con-
centrated to yield 31. Mp 195-197 °C (softens, 186-189 °C).
1H NMR δΗ (360 MHz, CDCl3): 1.7-1.77 (2H, m), 1.97-2.03
(4H, m), 2.5-2.54 (2H, m), 2.71-2.75 (2H, m), 2.89-2.92 (1H,
m), 3.04-3.07 (2H, m), 5.74 (1H, s), 6.15 (1H, s), 6.73-6.8 (2H,
m), 7.08-7.12 (1H, m), 7.94-8.00 (4H, s). MS m/z (ES+): 409
(M + H+). Anal. (C20H22F2N2O3S) C, H, N.
3-[[1-(2-(2,4-Diflu or op h en yl)et h yl)-4-p ip er id in yl]su l-
fon yl]ben zam ide (32). Carbon monoxide was bubbled through
a solution of 67c (3.95 g, 9 mmol), Et3N (2.5 mL, 18 mmol),
palladium(II) acetate (0.06 g, 0.3 mmol), and 1,1-bis(diphe-
nylphosphino)ferrocene (0.3 g, 0.5 mmol) in a mixture of
methanol (30 mL) and DMF (30 mL) at room temperature.
The mixture was heated at 60 °C for 18 h and then partitioned
between EtOAc and water. Product from the organic phase
was purified by column chromatography (silica; EtOAc/iso-
hexane 1:1) to give 2.75 g (73% yield) of methyl ester as a
1
colorless solid. Mp 116-7 °C. H NMR δΗ (360 MHz, CDCl3):
1.72-1.77 (2H, m), 1.97-2.03 (4H, m), 2.49-2.54 (2H, m),
2.70-2.75 (2H, m), 2.90-2.94 (1H, m), 3.04-3.07 (2H, m), 3.97
(3H, s), 6.72-6.80 (2H, m), 7.08-7.12 (1H, m), 7.67 (1H, t, 7.8
Hz), 8.07-8.5 (1H, m), 8.34-8.32 (1H, m), 8.55 (1H, s). A
solution of N-(2,4-difluorophenethyl)-4-(3-(carbomethoxy)phe-
nylsulfonyl)piperidine (0.2 g, 0.47 mmol) in toluene (10 mL)
was added to a mixture of trimethylaluminum (0.71 mL, 1.4
mmol) and ammonium chloride (0.077 g, 1.4 mmol) in toluene
(8 mL) at 0 °C. The mixture was heated at reflux for 18 h,
cooled to room temperature, quenched with 2 M HCl, basified
with 2 M NaOH, and extracted with CH2Cl2. The crude product
obtained from the organic phase was purified by column
chromatography (silica; CH2Cl2/MeOH 97:3) to give 32 (41 mg,
21%). Mp 142-3 °C. 1H NMR δΗ (400 MHz, CDCl3): 1.68-
1.78 (2H, m), 1.97-2.02 (4H, m), 2.50-2.54 (2H, m), 2.71-
2.75 (2H, m), 2.90-3.00 (1H, m), 3.04-3.07 (2H, m), 5.75-
5.85 (1H, s), 6.2-6.3 (1H,s), 6.70-6.80 (2H, m), 7.1-7.15 (1H,
m), 7.7 (1H, t, 7.8 Hz), 8.05 (1H, d, 7.8 Hz), 8.15 (1H, d, 7.8
Hz), 8.28 (1H, s). MS m/z (ES+): 409 (M + H+). Anal.
(C20H22F2N2O3S) C, H, N.
1-[2-(4-(4-P h en ylsu lfon yl)-1-p ip er id in yl)et h yl]-2-im i-
d a zolid in on e (33). A mixture of 66a (0.2 g, 0.88 mmol), N-(2-
chloroethyl)imidazolidinone31 (0.13 g, 0.88 mmol), NaI (0.13
g, 0.88 mol), and K2CO3 (0.12 g, 0.9 mmol) in acetonitrile (20
mL) was heated at reflux for 18 h. The solvent was then
evaporated and the residue partitioned between EtOAc and
water. The residue obtained from workup was purified by
column chromatography (silica; CH2Cl2 f CH2Cl2/MeOH 97:
3) followed by recrystallization from EtOAc to give 33 (0.17 g,
Ra t r1 Recep tor Bin d in g. Rat cortical membranes were
lysed by homogenization in 50 mM Tris-HCl buffer, pH 7.5,
and centrifuged at 50000g for 10 min at 4 °C. The resulting
pellet was suspended in 50 mM Tris-HCl buffer, pH 7.5, at 2
mg original wet weight/mL. Incubations were carried out for
30 min at ambient temperature (22 °C) in the presence of 1
nM [3H]-prazosin (77.2 Ci/mmol, NEN) and initiated by the
addition of microliters of membranes in a final assay volume
of 500 µL. Nonspecific binding was determined by 1 µM
prazosin. The reaction was terminated by rapid filtration over
GF/B filters (presoaked in 0.5% Triton) and washed with ice-
cold 50 mM Tris-HCl, pH 7.5. The radioactivity bound was
determined as described for the [3H]-ketanserin binding stud-
ies.
IKr Bin d in g. Binding to the voltage-dependent potassium
channel (delayed rectifier current, IKr) was evaluated by
displacement of 4 nM [3H]-dofetilide binding to HEK cells
stably expressing hERG, which encodes the IKr potassium
channel. Incubations were carried out in assay buffer (10 mM
HEPES containing 60 mM KCl, 71.5 mM NaCl, 1 mM CaCl2,
2 mM MgCl2, pH 7.4) for 75 min at ambient temperature (22
1
64%). Mp 169-71 °C. H NMR δΗ (400 MHz, CDCl3): 1.59-
1.78 (2H, m), 1.88-1.98 (4H, m), 2.47 (2H, t, J ) 6.5 Hz), 2.84-
2.92 (1H, m), 3.02-3.10 (2H, m), 3.27 (2H, t, J ) 6.5 Hz), 3.35-
3.50 (4H, m), 4.32 (1H, broad s), 7.55-7.63 (2H, m), 7.63-
7.70 (1H, m), 7.87 (2H, d, J ) 8 Hz). MS m/z (ES+): 338 (M +
H+). Anal. (C16H23N3O3S) C, H, N.
1-(4-Flu or oph en yl)-4-[4-(ph en ylsu lfon yl)-1-piper idin yl]-
bu ta n -1-on e (34). A mixture of 66a (0.2 g, 1 mmol), 2-(4-
fluorophenyl)-2-(1-chloro-3-propyl)-1,3-dioxolane (0.3 g, 1.2
mmol), K2CO3 (0.28 g, 2 mmol), and NaI (0.18 g, 1.2 mmol) in
CH3CN (10 mL) was heated at reflux under nitrogen for 18 h.
The reaction mixture was then concentrated and partitioned
between water and EtOAc. The organic phase was washed
with brine, dried (Na2SO4), and concentrated, and the syrup
obtained was redissolved in a mixture of methanol (15 mL)
and 6 N HCl (5 mL). After being heated at reflux for 30 min,
the mixture was cooled to room temperature, concentrated
under vacuum, and partitioned between 1 M NaOH (20 mL)

502 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2
Fletcher et al.
°C) and initiated with the addition of cell membranes (4 µg of
protein/well) in a total assay volume of 400 µL. Nonspecific
binding was determined with 20 µM dofetilide. The reaction
was terminated by rapid filtration over GF/B filters soaked in
0.1% BSA, and radioactivity bound was determined as for the
[3H]-ketanserin binding studies.
compound, and measurement of blood pressure. Heart rate was
derived from the blood pressure signal. The trachea was
cannulated, and animals were artificially respired to maintain
blood gases within normal limits. Body temperature was
maintained between 36 and 37 °C. ECG was measured by a
lead II configuration. All variables were measured using a
po-ne-mah data acquisition system. Recordings were taken,
10 min predose, 10 min postvehicle dose, and at 10 min
intervals, over a 30 min time period with the postinfusion dose
Deter m in a tion of th e Sta bility of Com p ou n d s 16-25
tow a r d Ra t Liver Micr osom es. Rat liver microsomes were
prepared from male Sprague-Dawley rats (final protein con-
centration of 0.4 mg/mL) in Dulbecco’s phosphate-buffered
saline.32 Each compound was preincubated for 5 min at 37 °C.
The reaction was initiated by addition of NADPH (final
concentration of 2 mM) and was allowed to proceed for a
further 30 min at 37 °C before termination with an equal
volume of acetonitrile and centrifugation (6000 rpm for 10
min). The supernatant was analyzed by LC-MS. Each reaction
was carried out in triplicate, turnover being calculated by
comparison of peak areas obtained with those from control
incubations lacking NADPH. For analysis by LC-MS, 5 µL
injections were made onto a KR100-5C18 HPLC column (5 cm
× 4.6 mm i.d.) with an isocratic mobile phase consisting of
appropriate ratios of acetonitrile and 25 mM ammonium
formate, adjusted to pH 3 with formic acid, at a flow rate of
1.0 mL/min split postcolumn 1:10 into a VG Platform II mass
spectrometer operating in the electropositive mode. Detection
was by single-ion recording, monitoring for protonated parent
ions.
Or a l Absor p tion a n d P h a r m a cok in etic Deter m in a -
tion s. Male Sprague-Dawley rats weighing approximately 300
g were surgically prepared at least 36 h prior to dosing.
J ugular veins were cannulated under anaesthesia (Isofluo-
rane), and each rat was given a 100-unit dose of heparin (0.1
mL, 1000 units/mL) via the cannula. Rats were individually
housed after surgery and had free access to food and water.
Test compounds were administered iv to three rats via a bolus
injection into a tail vein (1 mL/kg in a suitable vehicle) and
orally via a gavage to the stomach (5 mL/kg in a suitable
vehicle). Serial blood samples (approximately 400 µL) were
collected from the jugular vein at time points up to 8 h
postdose. In each case, plasma was separated from the blood
by centrifugation and stored at -20 °C until analysis. Systemic
exposure after oral administration was alternatively deter-
mined by administering each test compound to five male
Sprague-Dawley rats via a gavage to the stomach (5 mL/kg of
a 0.5% methocel A4C suspension). At time points up to 4 h
after dosing, one rat per time point was culled and blood was
collected. Samples were analyzed as described below.
P la sm a , Blood , a n d Br a in An a lysis. Typically, to aliquots
of plasma, blood, or brain homogenate (50-200 µL) was added
internal standard (10 µL of a 10 ng/µL solution of a structural
analogue), 100 µL of 0.1 M sodium hydroxide, 1 mL of water,
and 4 mL of ethyl acetate. Samples were vortex mixed and
centrifuged (3000 rpm, 10 min). The supernatant was removed
and evaporated to dryness (70 °C, under nitrogen), and the
residue was dissolved in the mobile phase (100 µL) and
transferred to an HPLC vial. Calibration standards covering
appropriate ranges were prepared by spiking solutions of
analyte at appropriate concentrations into the same volume
of control plasma, blood or brain homogenate, followed by the
same sample preparation procedure. Typically 30 µL injections
were made onto a KR100-5C18 HPLC column (5 cm × 4.6 mm
i.d.) with an isocratic mobile phase consisting of appropriate
ratios of acetonitrile and 25 mM ammonium formate, adjusted
to pH 3 with formic acid, at a flow rate of 1.0 mL/min split
postcolumn 1:10 into a VG Platform II mass spectrometer
operating in the electropositive mode. Detection was by single-
ion recording, monitoring for protonated parent ions. Model
independent pharmacokinetic parameters were determined
using standard formulas in a Microsoft Excel spreadsheet.
at levels of 0.3, 1, 3, and 10 mg kg-1 h-1
.
Su p p or tin g In for m a tion Ava ila ble: Data for compounds
1, 2, 5, 7, 12, 26, and 31 in the DOI-induced head-twitch model,
demonstrating 5HT2A receptor antagonism in vivo. This mate-
rial is available free of charge via the Internet at http://
pubs.acs.org.
Refer en ces
(1) Egan, C. T.; Herrick-Davis, K.; Miller, K.; Glennon, R. A.; Teitler,
M. Agonist activity of LSD and lisuride at cloned 5HT2A and
5HT2C receptors. Psychopharmacology. 1998, 136, 409-414.
(2) Newton, R. A.; Phipps, S. L.; Flanigan, T. P.; Newberry, N. R.;
Carey, J . E.; Kumar, C.; McDonald, B.; Chen, C.; Elliott, J . M.
Characterization of human 5HT2A and 5HT2C receptors ex-
pressed in the human neuroblastoma cell line SH-SY5Y: com-
parative stimulation by hallucinogenic drugs. J . Neurochem.
1996, 67, 2521-2531.
(3) Marek, G. J . A novel approach to the identification of psychiatric
drugs: Serotonin-glutamate interactions in the prefrontal
cortex. CNS Drug Rev. 2000, 6, 203-218.
(4) de Boer, T. The pharmacologic profile of mirtazepine. J Clin.
Psychiatry 1996, 57, 19-25.
(5) Heydom, W. E. Expert Opin. Invest. Drugs 1995, 4, 945.
(6) Hemrick-Luecke, S. K.; Snoddy, H. D. Evaluation of nefazodone
as a serotonin uptake inhibitor and a serotonin antagonist in
vivo. Life Sci. 1994, 55, 479-483.
(7) Zhang, W.; Bymaster, F. P. The in vivo effects of olanzapine and
other antipsychotic agents on receptor occupancy and antago-
nism of D1, D2, D3, 5HT2A and muscarinic receptors. Psychop-
harmacology 1999, 141, 267-278.
(8) Sanchez, C.; Arnt, J . In vivo assessment of 5HT2A and 5HT2C
antagonistic properties of newer antipsychotics. Behav. Phar-
macol. 2000, 11, 291-298.
(9) Leysen, D.; Linders, J . T. M.; Ottenheijm, H. C. J . 5HT2
Antagonists: a concept for the treatment of schizophrenia. Curr.
Pharm. Des. 1997, 3, 367-390.
(10) Heuillet, E.; Petitet, F.; Mignani, S.; Malleron, J .-L.; Lavayre,
J .; Neliat, G.; Doble, A.; Blanchard, J .-C. The naphthosultam
derivative RP 62203 (fananserin) has high affinity for the
dopamine D4 receptor. Eur. J . Pharmacol. 1996, 314, 229-233.
(11) Kehne, J . H.; Baron, B. M.; Carr, A. A.; Chaney, S. F.; Elands,
J .; Feldman, D. J .; Frank, R. A.; Van Giersbergen, P. L. M.;
McCloskey, T. C.; J ohnson, M. P.; McCarthy, D. R.; Poirot, M.;
Senyah, Y.; Siegel, B. W.; Widmaier, C. Preclinical characteriza-
tion of the potential of the putative atypical antipsychotic MDL
100907 as a potent 5-HT2A antagonist with a favorable CNS
safety profile. J Pharmacol. Exp. Ther. 1996, 277, 968-981.
(12) Rinaldi-Carmona, M.; Congy, C.; Santucci, V.; Simiano, J .;
Gautret, B.; Neliat, G.; Labeeuw, B.; Le Fur, G.; Soubrie, P.;
Breliere, J . C. Biochemical and pharmacological properties of
SR 46349B, a new potent and selective 5-hydroxytryptamine2
receptor antagonist. J . Pharmacol. Exp. Ther. 1992, 262, 759-
768.
(13) Trufflnet, P.; Tamminga, C. A.; Fabre, L. F.; Meltzer, H. Y.;
Rivi’ere, M. E.; Papillion-Downey, C. Placebo-controlled study
of the D4/5HT2A antagonist fananserin in the treatment of
schizophrenia. Am. J . Psychiatry 1999, 156, 419-425.
(14) Scrip 1999, 2458 (J uly), 21.
(15) Rowley, M.; Bristow, L. J .; Hutson, P. H. Current and Novel
Approaches to the Drug Treatment of Schizophrenia. J . Med.
Chem. 2001, 44, 477-501.
(16) Talvik-Lotfi, M.; Nyberg, S.; Nordstrom, A.; Ito, H.; Halldin, C.;
Brunner, F.; Farde, L. High 5HT2A receptor occupancy in M
100907-treated schizophrenic patients. Psychopharmacology
2000, 148, 400-403.
(17) Investigational Drugs Database Drug Report; 413342; Ashley
Publications: London, J une 26, 2001.
(18) Rowley, M.; Hallett, D. J .; Goodacre, S.; Moyes, C.; Crawforth,
J .; Sparey, T. J .; Patel, S.; Marwood, R.; Patel, S.; Thomas, S.;
Hitzel, L.; O’Connor, D.; Szeto, N.; Castro, J . L.; Hutson, P. H.;
MacLeod, A. M. 3-(4-Fluoropiperidin-3-yl)-2-phenylindoles as
High Affinity, Selective, and Orally Bioavailable h5-HT2A Recep-
tor Antagonists. J . Med. Chem. 2001, 44, 1603-1614.
(19) Gilligan, P. J .; Kergaye, A. A.; Lewis, B. M.; McElroy, J . F.
Piperidinylteralin σ ligands. J . Med. Chem. 1994, 37, 364-370.
Deter m in a tion of QTc In ter va l Ch a n ges. Three male
ferrets, approximately 1.3 kg, were anaesthetised (pentobar-
bitone sodium 45 mg/kg ip), and both femoral veins and one
femoral artery were cannulated for infusion of maintenance
anaesthetic (pentobarbitone sodium, 18 mg kg-1 h-1), test

4-(Phenylsulfonyl)piperidines
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 503
(20) Cheng, S. K. F.; Fletcher, S. R.; Blurton, P.; Burkamp, F.;
MacLeod, A. M.; van Niel, M. B. Phenylsulfonyl derivatives as
5-HT receptor ligands. Patent WO0053362, J uly 27, 2000.
(21) Cavero, I.; Mestre, M.; Guillon, J .-M.; Crumb, W. Drugs that
prolong QT interval as an unwanted effect: Assessing their
likelihood of inducing hazardous cardiac dysrhythmias. Expert
Opin. Pharmacother. 2000, 1, 947-973.
(22) Testa, B.; Caron, G.; Crivori, P.; Rey, S.; Reist, M.; Carrupt, P.
A. Lipophilicity and related molecular properties as determi-
nants of pharmacokinetic behavior. Chimia 2000, 54, 672-677.
(23) Baldwin, J . J .; Claremon, D. A.; Elliott, J . M.; Ponticello, G. S.;
Selnick, H. G. Preparation of arylheterocyclospiropiperidines as
class III antiarrhythmics. Patent EP 431943, J une 12, 1991.
(24) Yang, L.; Morriello, G.; Prendergast, K.; Cheng, K.; J acks, T.;
Chan, W. W.-S; Schleim, K. D.; Smith, R. G.; Patchett, A. A.
Potent 3-spiropiperidine growth hormone secretagogues. Bioorg.
Med. Chem, Lett. 1998, 8, 107-112.
(25) Nakagawa, I.; Aki, K.; Hata, T. Synthesis of 5′-Alkylthio-5′-
deoxynucleosides from Nucleosides in a One-Pot Reaction. J .
Chem. Soc., Perkin Trans. 1 1983, 1315-1318.
(26) Greenhalgh, R. P. Selective Oxidation of Phenyl Sulphides to
Sulphoxides or Sulphones Using Oxone and Wet Alumina.
Synlett 1992, 235-236.
(27) Berg, K. A.; Clarke, W. P.; Sailstad, A.; Saltzman, A.; Maayani,
S.; Signal transduction differences between 5-hydroxytryptamine
type 2A and type 2C receptor systems. Mol. Pharmacol. 1994,
46, 477-484.
(28) Patel, S.; Freedman, S.; Chapman, K. L.; Emms, F.; Fletcher,
A. E.; Knowles, M.; Marwood, R.; McAllister, G.; Myers, J .; Patel,
S.; Curtius, N.; Kulagowski, J . J .; Leeson, P. D.; Ridgill, M.;
Graham, M.; Matheson, S.; Rathbone, D.; Watt, A.; Bristow, L.
J .; Rupniak, N. M. J .; Baskin, E.; Lynch, J . J .; Ragan, C. I.;
Biological profile of L-745,870, a selective antagonist with high
affinity for the D4 receptor. J . Pharmacol. Exp. Ther. 1997, 283,
636-647.
(29) Morrow, L.; Creese, I. Characterisation of R1 adrenergic receptor
subtypes in rat brain. A re-evaluation of [3H] WB4104 and [3H]
prazosin binding. Mol. Pharmacol. 1986, 29, 321-330.
(30) Freedman, S. B.; Harley, E. A.; Iversen, L. L. Relative affinities
of drugs acting at cholinoceptors in displacing agonist and
antagonist radioligands: the NMS/Oxo-M ratio as an index of
efficacy at cortical muscarinic receptors. Br. J . Pharmacol. 1988,
93, 437-445.
(31) J ohnston, T. P.; McCaleb, G. S.; Montgomery, J . A. The synthesis
of Antineoplastic Agents XXXII. N-Nitrosoureas. J . Med. Chem.
1963, 6, 669-681.
(32) Lake, B. G. Preparation and characterisation of microsomal
fractions for studies on xenobiotic metabolism. In Biochemical
toxicology, a practical approach; Snell, K., Mullock, B., Eds.; IRL
Press: Oxford, 1987; pp 182-215.
J M011030V