Development and characterization of biphenylsulfonamides as novel inhibitors of bone resorption

Article abstract of DOI:10.1021/jm051236m

Increased osteoclastic bone resorption plays a central role in the pathogenesis of many bone diseases, and osteoclast inhibitors are the most widely used treatments for these diseases. We have identified and characterized a series of novel biphenylsulfona

Full text of DOI:10.1021/jm051236m

J. Med. Chem. 2006, 49, 7487-7492
7487
Development and Characterization of Biphenylsulfonamides as Novel Inhibitors of Bone
Resorption
Iain R. Greig,*,† Aymen I. Idris,†,‡ Stuart H. Ralston,‡ and Rob J. van’t Hof†.‡
School of Medicine, Institute of Medical Sciences, UniVersity of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, U.K., and Rheumatic Diseases
Unit, UniVersity of Edinburgh, Molecular Medicine Centre, Edinburgh EH4 2XU, U.K.
ReceiVed December 12, 2005
Increased osteoclastic bone resorption plays a central role in the pathogenesis of many bone diseases, and
osteoclast inhibitors are the most widely used treatments for these diseases. We have identified and
characterized a series of novel biphenylsulfonamide derivatives that have potent inhibitory effects on
osteoclastic bone resorption in vitro and that prevent ovariectomy-induced bone loss in vivo. A number of
aromatic substituted derivatives were prepared and a QSAR model was generated, which allowed accurate
prediction of compound potency. Using this model, we have prepared compounds able to inhibit osteoclast
formation and bone resorption in vitro at concentrations in the nanomolar range. One such compound, 55
(ABD295) (Greig, I. R.; Mohamed, A. I.; Ralston, S. H.; van’t Hof, R. J. Alkyl Aryl Sulfonamides as
Therapeutic Agents for the Treatment of Bone Conditions. GB Patent WO2005118528, 2005), fully reversed
ovariectomy-induced bone loss in mice at a dose of 5 (mg/kg)/day. In conclusion, biphenylsulfonamides
like 55 form a new class of potent antiresorptive agents with possible therapeutic use in diseases characterized
by increased bone resorption.
Introduction
teoclastic bone resorption in vitro and in vivo.18 The mechanism
of action for 67 is not fully understood. However, we have
previously reported that 67 inhibits activation of the transcription
factor nuclear factor κB (NFκB) stimulated by both tumor
necrosis factor (TNF) and the receptor activator of the NFκB
ligand (RANKL), indicating that the molecular target may be a
signaling molecule in the NFκB pathway.18 Our studies showed
that 67 causes osteoclast and macrophage apoptosis at concen-
trations in the range 5-20 µM but had no effect on apoptosis
of unrelated cells such as osteoblasts (IC50 > 100 µM) and
hepatocytes (IC50 > 200 µM). In spite of extensive optimization
of the structure, we were unable to make significant improve-
ments to the potency of 67 derived esters. Since the low potency
and potentially labile ester linkage made 67 unsuitable as a drug
candidate, we have carried out studies involving bioisosteric
replacement of the ester moiety (Figure 1) in an attempt to
identify more promising drug candidates. Here, we report our
findings on a set of sulfonamide derivatives as alternatives to
the ester-linked compounds described in our original report.18
We have developed simple synthetic methods for preparing a
large number of derivatives of this lead compound, which has
allowed us to generate a QSAR model from which we were
able to predict and make large improvements in the potencies
of derivatives. The most promising of these drugs has been
tested in osteoclast cultures in vitro and in an in vivo model
for bone loss.
Bone is a dynamic tissue that is constantly renewed in the
process of bone turnover. Osteoclasts are multinucleated cells
closely related to macrophages, which are responsible for the
resorption of bone.1 Increased osteoclastic bone resorption plays
an important role in the pathogenesis of common bone diseases
such as osteoporosis, Paget’s disease of bone, cancer-associated
bone disease, and periarticular bone loss associated with
inflammatory conditions,2-5 and the most successful forms of
treatment of these disorders are based on osteoclast inhibition.6
Bisphosphonates7 are the most widely used osteoclast inhibi-
tors in clinical practice, but calcitonin has also been used
successfully in the treatment of various conditions characterized
by increased bone loss.8 However, calcitonin appears to be less
effective than the bisphosphonates in the treatment of os-
teoporosis and other bone diseases.9 While the bisphosphonates
are highly effective antiresorptive drugs, intestinal absorption
is poor and inhibited by food. Therefore, bisphosphonates have
to be given on an empty stomach,10 which leads to problems
with compliance, especially in the elderly. Treatment with
aminobisphosphonates is also associated with adverse effects
including gastrointestinal intolerance11,12 and an acute phase
response after initial administration.13
Hormone replacement therapy and selective estrogen receptor
antagonists also act by inhibiting bone resorption, but they are
only effective in the prevention and treatment of osteoporosis
associated with oestrogen deficiency,14 and hormone replace-
ment therapy has been associated with an increased risk for
cancer.15-17 The range of available treatments for diseases
characterized by increased osteoclast activity therefore falls into
relatively few mechanistic classes, highlighting the need to
identify new classes of antiresorptive agents.
Chemistry
All compounds were synthesized using starting materials
purchased from Sigma-Aldrich or Lancaster. 4-Bromo-2-eth-
ylphenylsulfonyl chloride was purchased from Maybridge.
1
Products were characterized using H and 13C NMR obtained
We previously reported that the 4-hydroxybutyl ester of
biphenylcarboxylic acid derivative 67 (ABD56)18 inhibits os-
at 250 or 62.9 MHz, respectively, on a Brucker AC250
spectrometer. Purity was assessed using TLC and LC (column,
HIRPB, C18; mobile phase, 60% 25 mM ammonium acetate,
pH 4, 40% acetonitrile; λmax ) 235-275 nm). Elemental
analysis was performed on all compounds included in the QSAR
* To whom correspondence should be addressed. Phone: 0044 (0)1224
555823. Fax: 0044 (0)1224 559533. E-mail: i.greig@abdn.ac.uk.
† University of Aberdeen.
‡ University of Edinburgh.
10.1021/jm051236m CCC: $33.50 © 2006 American Chemical Society
Published on Web 11/11/2006

7488 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 25
Greig et al.
Scheme 2. Synthesis of Biphenyl Sulfonamides from
Bromophenylsulfonyl Chloridesa
Figure 1. Parent compound 67 and its sulfonamide bioisostere.
Scheme 1. Synthesis of Biphenylsulfonamides from Biphenylsa
a Reaction conditions: (a) CHCl3, SO2Cl2, room temp, 4 h; (b) SOCl2,
reflux, 3 h; (c) CH2Cl2, pyridine, amino alcohol.
a Reaction conditions: (a) CH2Cl2, pyridine, amino alcohol; (b) (Ph3P)4Pd,
Na2CO3, H2O, toluene, ethanol, reflux, 3 h.
model. All samples showed only one component unless
otherwise stated.
Table 1. Effects of Alkyl Chain Length on Drug Potency in the J774
Survival Assay
Sulfonamide derivatives were prepared either by direct
sulfonylation of the required biphenyl,19 which was then
chlorinated19 and coupled with the required amino alcohol in
the presence of pyridine (Scheme 1) to give sulfonamides 15-
26, or when the biphenyl was unavailable or where sulfonylation
was favored at a different site, from the required bromophenyl
sulfonamides 27-35 (Scheme 2), which was then used in
parallel syntheses and coupled to phenylboronic acids by
standard Suzuki coupling methods, to give sulfonamides 36-
61 (Scheme 2)19 and to prepare a sufficiently large and diverse
selection of derivatives to permit determination of the structure-
activity relationship.
compd
n
IC50 (µM)
15
16
17
18
0
1
2
3
>50
18
18
13
three caused a dramatic reduction (Table 1). The five-carbon
starting material 5-aminopentanol has been used for many
derivatives. However, for the most potent compounds we have
found that the four-carbon chain gave compounds with a better
solubility profile for testing in aqueous medium, and 4-ami-
nobutanol has mostly been used for these.
We next studied the importance of the ring orientation as
shown in Table 2. As expected from our studies on biphenyl
carboxylates, only linear structures are highly active, and the
biphenyl-2-sulfonamides and 3-sulfonamides were of much
lower potency. Also studied were the effects of N-alkylation.
We found that such variations had little effect on potency; IC50
values of 30 and 20 µM were obtained for the N-methyl (65)
and N-pentyl (66) derivatives of compound 16, respectively.
To test whether the substitution pattern for the aromatic rings
was important for drug activity, we prepared derivatives with a
wide range of substituents. Substitution on the outer ring showed
that the addition of electron-withdrawing substituents leads to
Results and Discussion
Since osteoclast inhibition assays are time-consuming and
are unsuitable for high-throughput screening, we conducted
initial screening of candidate compounds in cultures of the
mouse macrophage cell line J774. This cell line has been used
before as a model system to screen for inhibitor effects of
bisphosphonates on osteoclast activity,20 and our previous studies
showed that inhibitory effects of biphenyl carboxylate esters
on J774 survival correlated closely with inhibitory effects on
authentic osteoclasts.18 The unsubstituted derivative, compound
16, was tested in this assay and found to inhibit J774 survival
with an IC50 value of approximately 20 µM (Table 1), which is
comparable to that of the original ester-linked compound 67.
We found that increasing the length of the alkyl chain to five
or six carbons had little effect on potency, but reducing it to

Biphenylsulfonamides
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 25 7489
Table 4. Comparison of 2′-, 3′-, and 4′-Substituted Derivatives
Table 2. Effects of Ring Orientation on Potency in J774 Viability
Assays
compd
R
IC50 (µM)
23
24
36
45
48
49
50
51
52
2-nitro
3-nitro
4-methyl
2,4-bis(trifluoromethyl)
3-methyl
2-trifluoromethyl
4-trifluoromethyl
3,4-difluoro
2
33
13
2
28
6
5
16
4.5
compd
R
IC50 (µM)
19
50
63
64
4-(4-fluorophenyl)
4-(4-trifluoromethylphenyl)
2-(4-fluorophenyl)
8
5
>50
>50
3-(4-trifluoromethylphenyl)
Table 3. IC50 of 2′- and 4′-Derivatives in the J774 Survival Assay
2,4-difluoro
Table 5. Influence of Inner Ring Substitution on Drug Potency against
J774 Macrophages
compd
R
n
IC50 (µM)
16
17
19
20
21
22
23
25
36
37
38
39
40
41
42
43
44
45
46
47
49
50
52
62
H
H
1
2
1
1
2
1
1
1
2
2
1
2
2
2
2
2
2
2
1
2
1
1
2
1
18 ( 3
20 ( 3
8 ( 2.5
8 ( 2
4-fluoro
4-bromo
4-bromo
4-bromo-2-fluoro
2-nitro
2-iodo
4-methyl
4-acetyl
4-methylthio
4-cyano
compd
R1
R2
IC50 (µM)
16
19
26
50
52
53
54
55
56
57
58
59
60
61
unsubstituted
4-fluoro
unsubstituted
unsubstituted
3-methoxy
unsubstituted
unsubstituted
3-chloro
3-trifluoromethoxy
2-methyl
2-methyl
18 ( 3
8 ( 1
9 ( 2
3 ( 1
2,4-difluoro
4-trifluoromethyl
2,4-difluoro
2,4-difluoro
2,4-difluoro
2,4-difluoro
4-fluoro
2,4-difluoro
unsubstituted
2,4-difluoro
4-trifluoromethyl
4-trifluoromethyl
33 ( 3
2 ( 0.5
5.5 ( 1.5
13 ( 2
11 ( 2
35 ( 6
12 ( 2
31 ( 4
33 ( 3
32 ( 3
21 ( 3
2.5 ( 0.5
2 ( 0.5
8 ( 1
5 ( 1
4.5 ( 1.5
3.5 ( 0.5
1 ( 0.3
0.8 ( 0.1
2.5 ( 0.25
0.15 ( 0.05
4.5 ( 1
0.7 ( 0.1
5.5 ( 1.5
5 ( 1
2-methoxy
4-carboxy
3-ethyl
3-trifluoromethyl
3-trifluoromethyl
3-fluoro
4-dimethylamino
4-hydroxy
2.4-dichloro
2,4-bis(trifluoromethyl)
4-trifluoromethoxy
4-phenyl
2-trifluoromethyl
4-trifluoromethyl
2,4-difluoro
2-amino
2-fluoro
33 ( 5
6 ( 1.5
5 ( 1
4.5 ( 1
24 ( 3
contrast to the ester derivatives, structural variations of sul-
fonamide derivatives can lead to a dramatic increase in potency
but never resulted in a substantial decrease. All the less potent
sulfonamide derivatives have an IC50 between 30 and 35 µM,
as shown in Table 3. This suggests a nonspecific activity that
is unaffected by structural variations on the aromatic ring.
The presence of nonspecific activity is supported when
considering the 3′-derivatives as shown in Table 4, which also
shows a minimum potency of around 30 µM. The 3′-derivatives
were significantly less potent than their 2′ or 4′ counterparts,
which are of similar potency. The reduced potency of the 3′
derivatives is more likely to be due to electronic rather than
steric effects, as fluorine in particular has very low steric
demands.
We next investigated the effects of adding substituents onto
the inner ring and found that further increases in potency could
be obtained (Table 5). The 2-methyl, 3-trifluoromethyl, and
3-trifluoromethoxy substitutions increased potency 3- to 5 fold,
while addition of 2-fluoro, 3-fluoro, or 3-chloro groups had very
little effect on the potency and a 3-methoxy group caused a
5-fold reduction in potency (Table 5). These results are not easily
explained because trifluoromethyl and chloro groups are often
regarded as being interchangeable22 and have similar electronic,
hydrophobic, and steric characteristics.
increased potency (Table 3), with halogen, haloalkyl, ha-
loalkoxy, or nitro groups giving the most potent compounds.
Comparison of 4′- and 2′,4′-derivatives showed that further
addition of electron-withdrawing substitutions resulted in more
potent compounds. In addition, hydrophobic derivatives were
more potent than hydrophilic derivatives. This was shown by
the relatively lower potency of the hydrophilic cyano, acetyl,
and carboxy derivatives (Table 3), in spite of these substituents
being electron-withdrawing. The most striking anomaly in these
findings is the high potency of the nitro derivative, which has
previously been reported as being either weakly hydrophobic21,22
or hydrophilic.23 Nitro groups are not normally considered to
act as binding groups and therefore are unlikely to form an extra
interaction.24 It is possible therefore that a resonance structure
confers a change in the aromatic nature of the ring itself that is
particularly favorable in promoting interactions within the
putative binding site.
These findings are in accordance with our earlier studies on
ester compounds18 where we noted that addition of electron-
withdrawing substituents such as fluorine resulted in a slight
increase in potency. Addition of an electron-donating substituent
such as methyl to biphenyl carboxylate esters resulted in a
dramatic reduction in potency, while we were unable to find
any derivatives that gave a significant increase in potency. In
Simple QSAR models were generated using the ChemDraw8
add-on for Excel. This allows a regression analysis to be
performed on a range of physicochemical parameters25 with
respect to the observed activity. For the outer ring, we selected
Hansch (π) for the hydrophobic parameter, molar refractivity

7490 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 25
Greig et al.
Figure 3. Effects of compounds 16, 55, and 67 on osteoclast number.
16, 55, and 67 were tested in murine osteoclast cultures. The graph
indicates the number of osteoclasts expressed as percentage of the
vehicle control group. The graph represents the average of three
independent experiments, with n ) 5 in each experiment.
Figure 2. QSAR plot for drug activity in J774 macrophages. The graph
shows observed vs predicted activity using linear regression, for a range
of ortho and para aromatic substituents on biphenylsulfonamide
derivatives. The equation for the regression curve is 0.26πring a
+
0.59Fring a(o/p) - 0.027 MRring a + 3.06πring b - 3.03σring b - 0.23 MR-
ring b + 4.75, where π is the hydrophobicity constant, F is the inductive
constant, σ is the Hammett constant, and MR is the molar refractivity.
R2 ) 0.91; F ) 42.4.
with a ClogP value of more than 5, suggesting they are too
lipophilic to be suitable as oral drugs.
Our results suggest a biological target with a lipophilic
electron-rich binding pocket, which interacts with the outer ring;
a hydrogen bond donating residue, which interacts with one of
the sulfonamide oxygens; and a hydrogen bond donor or
acceptor, which interacts with the terminal hydroxyl group. The
inner ring may also bind to a lipophilic target, but it is uncertain
whether the electronic properties are more important for
regulating this interaction or for modulating the hydrogen-
bonding properties of the sulfonamide. There may also be a
binding role for the sulfonamide nitrogen, which may explain
the large increase in potency seen in certain derivatives relative
to their ester bioisosteres. The lack of significant effect on
potency by N-alkylation indicates that the nitrogen is not
required as an H-bond donor but may still be an H-bond
acceptor. We have not observed a link between biphenyl
conformation and potency.
We selected compound 55 from the studies in J774 mac-
rophages as the most promising agent for further investigation
and studied its effects on survival of authentic osteoclasts in
vitro and ovariectomy induced bone loss in vivo. The effects
of 55 on survival of mouse osteoclasts were compared with those
of 67 and the unsubstituted sulfonamide 16 (Figure 3). This
showed that 55 was about 60 times more potent at inhibiting
osteoclast survival than the unmodified sulfonamide derivative
16 and 67. Thus, 16 had a potency similar to that of the ester
67 (IC50 of 8 µM versus 9 µM) whereas the substituted
compound, 55, had an IC50 of approximately 150 nM. In
addition, all three compounds were considerably more potent
in osteoclast cultures than in J774 macrophage cultures. Because
NFκB activation is crucial for osteoclast formation and survival
but not for macrophages, this supports our original observation18
that these compounds inhibit RANKL- and TNF-induced NFκB
signaling.
(MR) as the steric parameter, and the Swain-Lupton inductive
constant (F) as the electronic parameter. The last was selected
over the more commonly used Hammett constant (σ) because
it better explained the high potency of the fluoro derivatives,
for which the Hammett value would have given a very small
contribution. Conversely for the inner ring, we found that the
Hammett constant gave a better correlation. We feel this is
justified, as the resonance contribution will have a stronger
influence on the sulfonamide moiety with inner ring substituents
and therefore is a much more important factor than for outer
ring substituents.
Figure 2 shows that there is a very strong correlation between
the nature of the ring substituents and the inhibitory effect on
macrophage survival. We found a highly significant relationship
between an increase in potency and substituents on the outer
ring with increasing electron-withdrawing capacity (F) (p <
0.001), increasing hydrophobicity (π) of the substituent (p <
0.0001), and reduced size (MR) of the substituent (p < 0.01).
In spite of the smaller number of derivatives studied, we also
found a strong relationship between substituents on the inner
ring with increased hydrophobicity (π) of the substituent (p <
0.0001), reduced electron-withdrawing capacity (σ) of the
substituent (p < 0.0001), and reduced size (MR) of the
substituent (p < 0.0001) with an increase in potency. However,
we recognize that the values for the inner ring constants are
likely to be unreliable because of the small number of derivatives
made and variations in literatures values. The main outlier in
this model is the 2′-nitro derivative, for which the high potency
clearly is not adequately described, even when using π ) 0.24
rather than -0.28.21-23 As described earlier, this suggests a
further enhancement to the electronic properties of the ring. The
model suggests a balance between hydrophobic properties,
which increase potency, and electron-withdrawing properties,
which decrease potency; groups such as trifluoromethyl or
trifluoromethoxy may have sufficient hydrophobicity to over-
come the electron-withdrawing properties, whereas halogens do
not.
Ovariectomy resulted in a 35% loss in trabecular bone volume
because of a decrease in trabecular thickness and trabecular
number (Figure 4), and 67 (5 (mg/kg)/day) only partially
prevented this bone loss. Compound 55, however, completely
prevented the ovariectomy-induced bone loss at the same dose,
indicating that the observed increase in potency in vitro also
translates into increased in vivo potency.
QSAR models using these compounds suggested a pattern
with potent compounds requiring an electron-donating, hydro-
phobic substituent. Using the equation generated, we were able
to predict a potency of 130 nM for the 3-ethyl derivative 57;
synthesis and testing gave an actual value of 150 nM,
demonstrating that the model can be successfully used to design
highly potent compounds. Our model suggests that further
addition of hydrophobic substituents will further increase
potency; however, these derivatives are likely to prove difficult
to use in aqueous medium and may break the Lipinsky rules26
Conclusion
We have previously shown that 67 represents a novel class
of osteoclast inhibitors. However, the potentially labile ester
bond present in 67, its lack of potency, and the limited scope
to improve upon this led us to develop more potent and stable
bioisosteres of this compound. Our results show that, using

Biphenylsulfonamides
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 25 7491
Blue reagent (Biosource) per well, incubating the cells for a further
3 h, and measuring viability as fluorescence (excitation at 530 nm,
emission at 590 nm) using a Labtech FL600 plate fluorimeter. Each
compound was tested in at least three independent experiments,
with n ) 5 in each experiment. The IC50 was calculated using
Graphpad Prism software.
Murine Osteoclast Generation. Bone marrow was flushed out
of the femora and tibiae of adult mice using Hank’s balanced salt
solution (HBSS). The resulting cell suspension was spun down at
300 g for 3 min, resuspended in 10 mL of culture medium (R-
MEM supplemented with 10% FCS and penicillin/streptomycin),
and cultured in one 10 cm Petri dish per mouse for 3 days at 37 °C
in the presence of 100 ng/mL M-CSF. Subsequently, the Petri dish
was washed three times with PBS, and the adhered cells were
harvested using trypsin digestion. The cells were resuspended in
culture medium supplemented with 100 ng/mL RANKL and 25
ng/mL M-CSF, at a density of 4 × 104 cells/mL, and 125 µL per
well of this suspension was seeded onto dentine slices in a 96-well
plate. The cells were cultured at 37 °C in 5% CO2 for 7 more days,
with medium changes after 2 and 4 days. Compounds to be tested
were added during the second medium change and present for 72
h.
Tartrate-Resistant Acid Phosphatase (TRAcP) Staining. Os-
teoclasts were identified by staining for TRAcP essentially as
described by van’t Hof et al.27 Briefly, at the end of the culture
period dentine slices with adherent cells were fixed in 4%
paraformaldehyde, washed with PBS, and incubated with naphthol-
ASBI-phosphate, pararosanilin, and sodium tartrate in acetate
buffer (30 mM) at 37 °C for 45 min. TRAcP positive cells with
three or more nuclei were considered to be osteoclasts.
Figure 4. Effects of 67 and compound 55 on ovariectomy-induced
bone loss. Both 67 and 55 were administered at 5 (mg/kg)/day by
intraperitoneal injection. Data are expressed as percentage change from
sham operated control animals ( SEM, n ) 6: BV/TV, bone volume
as percentage of total tissue volume; Tb.Th, trabecular thickness; Tb.N,
trabecular number. Statistical significance of the difference to sham
control (ANOVA, Dunnet’s post-test) is indicated by asterisks: (/) p
< 0.05; (///) p < 0.001.
QSAR-aided drug design, we have been able to achieve a 100-
fold increase in potency of our antiresorptive drugs. Furthermore,
one of the optimized compounds completely prevented ova-
riectomy-induced bone loss in vivo. In conclusion, we have
developed a novel class of compounds with sufficient antire-
sorptive potency to be considered clinical candidates for the
treatment of osteoporosis and other bone disorders characterized
by increased osteoclast activity.
Ovariectomy-Induced Bone Loss. Ovariectomy or sham ova-
riectomy was performed in 9-week old adult female C57/BL6 mice
obtained from Harlan Laboratories (U.K.) as previously described.28
Treatment with compounds was commenced 2 days after ovariec-
tomy or sham ovariectomy by intraperitoneal administration of the
drug in corn oil in a dose of 5 (mg/kg)/day. Controls received oil
alone. The treatment was continued for 21 days, and the experiment
was terminated on day 23. Bone mineral density and content was
measured at the right tibial metaphysis by µCT using a Skyscan
1072, at a resolution of 5 µm. The images were reconstructed using
the Skyscan ConeRec program and analyzed using Skyscan CTAN
software. The measurements were taken from 200 slices directly
distal of the growth plate.
Experimental Section
General Methods for Synthesis of Compounds. Method A.
General Method for Suzuki Coupling. 4-Bromophenylsulfonic
acid (4-hydroxybutyl)amide (1 g) was dissolved in a mixture of
toluene (8 mL) and ethanol (8 mL). 2,4-Difluorophenylboronic acid
(1 g) was added followed by 2 M Na2CO3 (8 mL). The mixture
was stirred vigorously under N2, and (PPh3)4Pd (0.2 g) was added.
The mixture was refluxed with stirring for 3 h under an atmosphere
of N2. The solvent was removed under vacuum, and the residue
was dissolved in ethyl acetate and washed with water and saturated
NaCl solution. After the mixture was dried (Na2SO4), the solvent
was evaporated and the resultant oil purified by column chroma-
tography to give a white powder or clear oil.
Method B. General Method Sulfonamide Formation. Biphe-
nyl-4-sulfonyl chloride (1 g) and 4-aminobutanol (1 g) were
dissolved in dichloromethane (30 mL). Pyridine (1 mL) was added,
and the mixture was stirred for 2 h at room temperature. Water
(30 mL) was added, and the organic phase was separated. The
aqueous portion was washed with ethyl acetate (30 mL), and the
organic phases were combined and dried (Na2SO4). The solvents
were evaporated, and the title compound was obtained as a white
solid following trituration with ether or following column chro-
matography (ethyl acetate/petroleum spirit) if required.
Acknowledgment. The authors thank Scottish Enterprise for
funding of this project, and Denise Tosh for assistance with
the cell culture.
Supporting Information Available: Details of compound
synthesis, spectroscopic data (1H and 13C NMR spectra), mass
spectrometry data, and elemental analysis data. This material is
available free of charge via the Internet at http://pubs.acs.org.
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