Activity of nitrogen-containing and non-nitrogen-containing bisphosphonates on tumor cell lines

Article abstract of DOI:10.1021/jm060280e

We synthesized and tested three series of bisphosphonates for their activity in inhibiting the growth of three human tumor cell lines: MCF-7 (breast), NCI-H460 (lung), and SF-268 (CNS). The first series of compounds consisted of 49 nitrogen-containing bis

Full text of DOI:10.1021/jm060280e

5
804
J. Med. Chem. 2006, 49, 5804-5814
Activity of Nitrogen-Containing and Non-Nitrogen-Containing Bisphosphonates on Tumor Cell
Lines
Yonghui Zhang, Annette Leon,‡,§ Yongcheng Song,†,§ Danielle Studer, Christa Haase, Lukasz A. Koscielski, and
†
,§
†
†
†
Eric Oldfield*,
†,‡
Department of Chemistry, UniVersity of Illinois at Urbana-Champaign, 600 South Mathews AVenue, Urbana, Illinois 61801, and
Department of Biophysics, UniVersity of Illinois at Urbana-Champaign, 607 South Mathews AVenue, Urbana, Illinois 61801
ReceiVed March 13, 2006
We synthesized and tested three series of bisphosphonates for their activity in inhibiting the growth of three
human tumor cell lines: MCF-7 (breast), NCI-H460 (lung), and SF-268 (CNS). The first series of compounds
consisted of 49 nitrogen-containing bisphosphonates, the most active species being a tetrakispivaloyloxymethyl
(POM) ester, having an (average) IC50 of 6.8 µM. The second series of compounds consisted of nine
terphenylbisphosphonates, the most active species also being a POM ester, having an IC50 of 2.2 µM. The
third series of compounds consisted of seven halogen or cyanophenylbisphosphonates, the most active species
again being a POM ester, having an IC50 of 500 nM. Taken together, these results are of interest because
they show that bisphosphonate esters can have potent activity against a variety of tumor cell lines, with the
most active terphenyl- and halophenyl-containing species having IC50 values ∼10-40× lower than the
most potent commercially available bisphosphonates.
Introduction
reported that 6 also had activity against a human tumor cell
line and was anti-angiogenic, and in their latest work, this group
reported that the p-bromophenyl bisphosphonate 7 had an IC50
of ∼95 µM against a human squamous cell carcinoma cell line.
a
Nitrogen-containing bisphosphonates (NBPs) such as rise-
dronate (1) and zoledronate (2) are used extensively in the
treatment of osteoporosis, Paget’s disease, and hypercalcemia
25
1
,2
due to malignancy. They are also potent activators of human
3,4
5-10
γδ T cells, as well as having in some cases direct anticancer
1
1-19
and antiparasitic
activity. They function by inhibiting the
enzyme farnesyl diphosphate synthase (FPPS, EC 2.5.1.10), the
enzyme responsible for the synthesis of the FPP used in protein
prenylation, cholesterol, ergosterol, heme a, ubiquinone, and
dolichol production. In addition, the isopentenyl diphosphate
(IPP), which might accumulate on FPPS inhibition, can be
converted to a “toxic ATP analog” (the isopentenyl ester of
ATP) ApppI (3), which inhibits the mitochondrial adenine
nucleotide translocase and is strongly pro-apoptotic.2 A second
class of bisphosphonates used clinically to treat osteoporosis
are the non-nitrogen-containing bisphosphonates (NNBPs), such
as clodronate, etidronate, and tiludronate (4). These compounds
0
do not inhibit FPPS, rather, they also are converted to pro-
apoptotic ATP analogues2
1,22
in which the bisphosphonate
condenses with AMP to form the â,γ-methylenetriphosphates
AppCp (clodronate), AppEp (etidronate), and AppTp (5, tilu-
dronate), which again all inhibit the mitochondrial ADP/ATP
transporter and are pro-apoptotic. There are also a number of
related NNBPs in development, such as the deaza-analogue of
risedronate, 6, which in early work11 we found had activity
against trypanosomatid parasites such as Trypanosoma brucei,
the causative agent of African sleeping sickness, and Plasmo-
dium falciparum, the causative agent of the most serious and
2
3,24
prominent form of malaria. More recently, Lecouvey et al.
A problem with the bisphosphonates is, however, that they
are poorly orally available and are rapidly adsorbed by bone.
While the latter property is of course critical for their use in
treating bone-related diseases, for further more general develop-
ment as anticancer or antiparasitic agents, it might be desirable
to have more lipophilic species. Plus, it would be of interest to
explore the activities of a wider range of bisphosphonates, both
nitrogen-containing and non-nitrogen-containing (NBPs and
NNBPs), against tumor cell lines. Here, we report the synthesis
*
Corresponding author. Phone: 217-333-3374. Fax: 217-244-0997.
E-mail: eo@chad.scs.uiuc.edu.
†
Department of Chemistry.
Department of Biophysics.
These authors contributed equally to this work.
Abbreviations: FPP, farnesyl diphosphate; FPPS, farnesyl diphosphate
‡
26
§
a
synthase; IPP, isopentenyl diphosphate; NBP, nitrogen-containing bisphos-
phonate; NNBP, non-nitrogen-containing bisphosphonate; POC, isopropyl-
oxycarbonyloxymethyl; POM, pivaloyloxymethyl; QSAR, quantitative
structure activity relationship.
1
0.1021/jm060280e CCC: $33.50 © 2006 American Chemical Society
Published on Web 08/24/2006

Bisphosphonate Effects on Tumor Cell Growth
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 19 5805
Figure 1. Structures of the most active nitrogen-containing bisphosphonates rank-ordered by activity from highest (8) to lowest (35).
and testing against three human tumor cell lines (MCF-7, NCI-
H460, and SF-268) of three chemically quite distinct sets of
bisphosphonates, including several which are very lipophilic.
General Synthetic Aspects. We show in Figures 1 and 2
ment with chloromethyl pivalate and sodium iodide,29 followed
by Michael addition of 2-aminopyridine, to give 8.
We also investigated 9 NNBPs containing terphenyl side
chains (55-63), shown in Figure 3. The POM ester 55 was
synthesized according to Scheme 3, while the free acids (56-
63) of the terphenyl-containing NNBPs were synthesized
basically as exemplified in Scheme 4 for the meta, meta-
terphenyls (56, 58, and 61).
(
rank ordered in terms of decreasing activity) the structures of
the 49 NBPs investigated. Most of these compounds are novel
-(pyridinium-1-yl)ethylidene-1,1-bisphosphonates, among which
those bearing a 1-hydroxyl group (9-11, 17-19, 22, 24-28,
6, 37, 40, 43, 44, 46, and 49) were made following the
2
3
The synthesis consists of three parts: (a) Suzuki coupling of
an methyl ester of a bromophenylalkanoic acid with a biphenyl
boronic acid to form a methyl terphenylalkanoate; (b) hydrolysis
of the ester so obtained to yield the corresponding carboxylic
acid, followed by conversion to the acid chloride; and (c)
reaction of the acid chloride with tris(trimethylsilyl) phosphite,
27
protocols described previously, as shown in Scheme 1. Their
synthesis involved the use (when necessary) of Suzuki coupling
to produce a substituted pyridine, which was alkylated with
bromoacetic acid, then phosphonylated with H3PO3/POCl3, as
shown in Scheme 1 (top).
3
0
The other class of pyridinium-1-yl compounds are those
lacking the 1-hydroxyl group (14-16, 20, 21, 29-34, 39, 41,
followed by hydrolysis, to afford the bisphosphonic acid.
Finally, we show in Figure 4 the structures of five pivaloy-
loxymethyl (POM) or isopropoxycarbonyloxymethyl (POC)
esters (64-68) and two free acids (69 and 70) of halophenyl-
or cyanophenyl-containing bisphosphonates (rank ordered in
terms of activity, as described below). The POM esters were
prepared by alkylation of tetramethyl methylenebisphosphonate
with a benzyl bromide, followed by transesterification,29 as
shown in Scheme 5. This strategy was then extended to form
the POC esters. The free acids (69 and 70) were prepared by
4
8, and 50-54), which were prepared by Michael addition of
substituted pyridines (prepared according to Scheme 1) to
vinylidene-1,1-bisphosphonic acid, as is also shown in Scheme
2
8
1
(bottom).
The synthesis of 8, a “pro-drug” of an NBP, containing four
pivaloyloxymethyl (POM) ester groups, was prepared as shown
in Scheme 2. Here tetramethyl vinylidene-1,1-bisphosphonate
was converted to its tetrakis-pivaloyloxymethyl ester by treat-

5
806 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 19
Zhang et al.
Figure 2. Structures of the less active nitrogen-containing bisphosphonates rank-ordered by activity as in Figure 1.
Scheme 1a
particularly active compound (IC50 (avg) ) 16.2 µM) is the
-pyridyl-amino-containing bisphosphonate (12). This com-
pound is known to be a potent FPPS inhibitor whose activity
can be related to the presence of charge delocalization as a result
of resonance with the p-quinonoid species (12a and 12b):
4
3
1
a
Reagents: (i) RB(OH)2, Pd(PPh3)4, K2CO3; (ii) BrCH2COOH; (iii)
H3PO3, POCl3.
The next four most active compounds are zoledronate (2)
and 13-15, all of which have average IC50 values <30 µM
treatment of their tetramethyl esters with bromotrimethylsilane
(TMSBr), followed by hydrolysis.
(
Table 1), followed by risedronate (1), with an average IC50
Full details of the synthesis of each novel compound are
described later in the paper, and microanalytical results are
provided in the Supporting Information.
value of ∼34 µM. All of the other free acid (or salt) compounds
have IC50 values >40 µM, Table 1.
These results are all consistent with our previous pharma-
cophore modeling and QSAR (quantitative structure activity
Results and Discussion
4
,27,31
relationship) studies,
which indicated the importance of
We first investigated the growth inhibition of the three human
tumor cell lines MCF-7 (breast), NCI-H460 (lung), and SF-
68 (CNS) by the nitrogen-containing bisphosphonates shown
having a positive charge located either in an aromatic ring or
in the â-position, two negative ionizable groups, as well as a
hydrophobic feature for optimal activity, and the IC50 values
found are not atypical of those reported for these and other
2
in Figures 1 and 2. The IC50 values so obtained are shown in
Table 1, together with, for ease of comparison, the average IC50
values found, averaged across the three cell lines. The IC50
values for the free bisphosphonic acids (i.e., not including the
POM ester, 8) are all in the range of ∼10 µM to >10 mM. Of
the free acids investigated, the most active compounds are the
three pyridinium-1-yl bisphosphonates (9-11), each containing
a pyridinium-1-yl group and a hydrophobic side chain. Another
5-10
bisphosphonates in other cell lines in the literature.
For
3
2
example, Alvarez et al. found IC50 values for alendronate,
risedronate (1), and pamidronate (38) of >40, >40, and 33.6
µM, in the 13 762 rat mammary carcinoma cell line. Our results
do, however, suggest that obtaining IC50 values of <10 µM for
the NBPs may be difficult, presumably due to their high polarity.
This can be countered to some extent by adding hydrophobic

Bisphosphonate Effects on Tumor Cell Growth
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 19 5807
Scheme 2a
a
Reagents: (i) ClCH2OC(O)-t-Bu, NaI, reflux; (ii) 2-aminopyridine, 20% overall yield.
Figure 3. Structures of the terphenyl, non-nitrogen-containing bisphosphonates, rank-ordered by activity from highest (55) to lowest (63).
Scheme 3a
a
Reagents: (i) 3-biphenylboronic acid, Pd(PPh3)4, K2CO3; (ii) NBS, AIBN; (iii) CH2(POOMe)2, NaH, 64% for three steps; (iv) ClCH2OC(O)-t-Bu, NaI,
reflux, 42% isolated yield.
Scheme 4a
a
Reagents: (i) Pd(PPh3)4, K2CO3; (ii) NaOH, THF-H2O, and then (COCl)2; (iii) P(OTMS)3.
side chain features (9-11), but arguably, an even more
pronounced effect on cell growth inhibition might be obtained
by masking the bisphosphonate group by esterification. POM
esters (prodrugs) of alendronate and pamidronate have been
reported in the patent literature,33 however, we were not able
to obtain these products in high purity.
species is a very potent, low nM inhibitor of FPPS,31,34 due we
believe to its strong amidinium-like resonance stabilization
We therefore investigated the effects of esterification of the
bisphosphonate groups of another bisphosphonate, 35. This
and, unlike other nitrogen-containing bisphonates, 35 can be

5
808 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 19
Zhang et al.
Figure 4. Structures of the benzylbisphosphonates investigated, rank-ordered by activity from highest (64) to lowest (70).
Scheme 5a
a
Reagents: (i) NaH, RC6H4CH2Br; (ii) ClCH2OC(O)-t-Bu, NaI; (iii) ClCH2OC(O)O-i-Pr, NaI; (iv) TMSBr.
readily converted to the tetrakis-POM ester via a mild Michael
addition (Scheme 2).
and 2, Table 1). The most potent growth inhibitors (as the free
acids) are 56 and 57, which have average IC50 values of 45.1
and 78.9 µM, respectively. This is clearly a factor of ∼3-4×
weaker than with the best NBPs. The most active species have
a meta substitution on the ring closest to the bisphosphonate
backbone, while the two para-substituted compounds (62 and
63) have very low (>480 µM) activity. The results shown in
Table 2 indicate that a meta,meta (terphenyl, ring) substitution
pattern with two side chain methylene groups results in the
highest activity (45 µM) and that this activity decreases on
removing these groups (141 µM, 1 CH2 group, 58; 299 µM, no
CH2 groups, 61). Compounds with para substitutions on the
ring attached to the bisphosphonate group are even less active
The parent bisphosphonate, while a potent inhibitor of FPPS,
has however only a 145 µM (average) IC50 value as the free
acid against the three tumor cell lines, Table 1. However, on
esterification, this IC50 value drops to 6.8 µM, Table 1, a factor
of ∼20× improvement in potency due to masking of the highly
polar bisphosphonate group. This is an interesting result because
it implies that esterase activity in these tumor cell lines enables
hydrolysis of the POM ester to the active free acid, opening up
the possibility of developing other, even more potent, lipid
soluble analogues using this approach.
The second series of bisphosphonates investigated were the
nine terphenyl species shown in order of decreasing activity in
Figure 3. The rationale for investigating these species in tumor
cell growth inhibition was 4-fold: First, we previously found
that the simple aryl bisphosphonate 6 had activity in several
cell lines and others have found activity against tumor cell lines
as well, so it seemed logical to investigate modified aryl side
chains to try to improve cell uptake and, perhaps, target
inhibition. Second, because these compounds lack the positive
charge (or basic nitrogen site) found in the NBPs, they should
present less of a challenge for conversion into lipophilic (POM
and POC) esters. Third, in initial work we found that addition
of a single phenyl group (to make m,p-biphenyl ethylidene
bisphosphonates) did not result in active compounds (IC50 >
(62, 482 µM; 63, 622 µM). Interestingly, removal of the 1-OH
group and esterification of the phosphonate groups to form the
POM ester 55 results in a major increase in activity, with 55
having an IC50 of 2.2 µM (Table 2), a 60× increase in potency
over the m,m-terphenyl analogue 58 (IC50 ) 141 µM, Table 2).
While at present we cannot be certain that this effect is
exclusively due to esterification (since the absence of the 1-OH
group could also in principle play a role), the enhanced activity
of the POM ester NNBP compares favorably with the ∼20×
enhancement on esterification seen with the NBPs (35 f 8)
and suggests that investigation of other terphenyl POM esters
may be worthwhile.
The final series of compounds investigated were another set
of NNBPs, this time containing just a single ring, but with
various electron-withdrawing substituents. The rationale for
investigating these compounds is that the halogen-containing
bisphosphonate (4) as well as the phenyl analogue 6 have
activity in cells: tiludronate (4) against osteoclasts and 6 against
T. cruzi and tumor cells. Because 4 is metabolized to 5 in cells
and targets the mitochondrial adenine nucleotide translocase,
we reasoned that 6 (and its halogenated analogues) might also
kill tumor cells in the same way and that, perhaps, halogen
2
50 µM), necessitating incorporation of additional features:
terphenyls, esters, and, as discussed below, halogen substitution.
Fourth, we already had several of these compounds available
in our laboratory.
Figure 3 shows the compounds investigated, and Table 2
shows the IC50 values determined. What can be seen im-
mediately from the results presented in Table 2 is that all of
the free acid NNBPs based on the terphenyl ring system are
less active than are the most active free acid NBPs (Figures 1

Bisphosphonate Effects on Tumor Cell Growth
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 19 5809
Table 1. IC50 Values for Tumor Cell Growth Inhibition by
Table 3. IC50 Values for Tumor Cell Line Growth Inhibition by
Nitrogen-Containing Bisphosphonates
Non-Nitrogen-Containing Benzyl Bisphosphonates
MCF-7
NCI-H460
SF-268
mean IC50a
MCF-7 NCI-H460 SF-268 mean IC50a
compound
(µM)
(µM)
(µM)
(µM)
compound
(µM)
(µM)
(µM)
(µM)
ring
8
9
6.44
5.95
5.60
23.2
14.8
12.6
11.7
5.73
21.5
33.0
43.7
41.3
52.2
74.4
54.5
62.0
62.0
18.5
22.9
71.7
65.8
69.9
66.8
58.1
109
59.0
53.7
92.9
141
142
63.7
117
211
71.8
7.89
6.50
10.4
13.1
14.4
14.3
6.76
9.80
16.0
16.4
16.6
17.9
19.3
23.3
27.9
34.2
39.8
41.2
47.4
47.9
48.2
49.8
51.6
51.6
56.1
57.7
65.4
72.5
79.1
82.4
87.8
88.6
115
133
134
145
154
171
207
225
267
269
272
282
302
406
496
1316
64
65
66
67
68
69
70
0.22
0.34
1.97
15.2
58.6
533
0.62
0.65
1.43
4.78
28.3
7.77
349
0.50
1.49
3.87
21.2
29.7
442
3,4-Br2-Ph
3,4-Cl2-Ph
3,4-Cl2-Ph
3,4-F2-Ph
CN-Ph
17.3
14.5
21.4
22.7
27.7
46.0
25.1
26.5
35.7
34.6
44.2
37.2
33.5
38.1
42.6
69.2
82.5
50.7
58.1
79.4
98.1
121
72.3
132
123
143
125
129
223
171
2.70
4.85
20.1
22.6
446
1
1
1
0
1
2
2
3
4
5
1
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
3,4-Br2-Ph
CN-Ph
1
1
1
6.18
>1000 >1000
>1000
23.2
24.1
23.3
43.6
27.2
30.7
55.7
44.6
44.8
67.0
49.2
45.8
49.3
46.8
52.6
58.3
65.1
72.7
89.3
109
133
132
147
174
111
408
232
261
a
Mean values over the three cell lines.
We show, therefore, in Figure 4 and Table 3 the structures
and IC50 values for a series of such bisphosphonates containing
electron-withdrawing groups. For the free acid/salt species (69
and 70), the IC50 values, not surprisingly, are very high, >400
µM, Table 3. However, on conversion to the POM and POC
esters, there are major increases in potency. Indeed, each of
the five esters investigated have considerable activity against
each cell line, with (average) IC50 values in the range of 500
nM to 30 µM, with the most active compound having the lowest
IC50 value (500 nM) of any of the compounds investigated in
this study. There are also some clear structural trends in activity.
For the POM, the activity is 3,4-Br2Ph (64) > 3,4-Cl2Ph (65);
the activity of the 3,4-Cl2Ph POM (65) is greater than that of
the 3,4-Cl2Ph POC (66); and the activities of each of these
compounds are much greater than those of the 3,4-F2Ph, CN-
Ph POC (67, 68), Table 3. Thus, conversion of the free acids
into more lipid soluble forms appears to result in enhanced
uptake into the tumor cells because, in the case of the free acids,
the IC50 values are much higher (a factor of >800 for the most
active compound, 64, versus its free acid, 69).
Mechanistically, based on what is known about the mode of
action of the NBPs, it seems likely that many of the most active
NBPs target primarily FPPS, resulting in inhibition of protein
prenylation as well as production of the pro-apoptotic species
ApppI (3). On the other hand, the NNBPs clodronate, etidronate,
and tiludronate are thought to act by forming only toxic ATP
analogues (such as 5), and it is possible that this mechanism
also operates with species such as 6, 7, and the benzylbisphos-
phonates shown in Figure 4 because these compounds have
essentially no inhibitory effects on FPPS (data not shown).
Although we cannot rule out other possible mechanisms for
these and indeed the terphenyl bisphosphonates, the observation
that substitution of the bisphosphonate’s methylene group by
Cl2, OH/Me, or a chlorophenylthio group (clodronate, etidronate,
tiludronate) leads in every case to incorporation of these NNBPs
into AppXp analogues, clearly suggests a similar mechanism
with related species (such as 64), with inhibition of the
mitochondrial adenine nucleotide translocase leading to apo-
ptosis.
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
191
141
236
260
280
289
288
304
208
279
284
270
297
312
469
644
243
257
260
290
301
436
399
447
409
339
3209
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
a
Mean values over the three cell lines.
Table 2. IC50 Values for Tumor Cell Growth Inhibition by
Terphenyl-Containing Bisphosphonates
mean IC50a
(µM)
MCF-7
(µM)
NCI-H460
(µM)
SF-268
(µM)
compound
5
5
5
5
5
6
6
6
6
5
6
7
8
9
0
1
2
3
2.62
43.9
92.7
152
146
196
310
412
1063
1.64
46.9
86.1
140
2.38
44.7
58.0
130
2.21
45.1
78.9
141
141
168
299
482
622
However, independent of mechanism, the results presented
above show that NNBPs clearly have activity against these three
human tumor cell lines, with the most active compounds being
considerably more potent than the most active NBPs, due, we
believe at least in part, to their enhanced lipophilicity. For the
NBPs 8 and 35, esterification results in a factor of 20 increase
in potency (6.8 µM versus 145 µM); in the case of the terphenyl
NNBPs, esterification (combined perhaps with removal of the
133
132
285
413
143
175
303
620
329
475
a
Mean values over the three cell lines.
1
-OH group) gives a factor of ∼60× increase in potency, while
substitution might result in enhanced activity (given that both
tiludronate and 7 contain halogen groups). Likewise, halogenated
aryl 1-amino bisphosphonates have been reported in the early
literature35 as herbicides and fungicides and might also have
this mechanism of action.
for the dibromophenyl-containing bisphosphonate, POM ester
formation results in a factor of ∼800× increase in activity, with
IC50 values of 500 nM (64) versus 442 µM (69).
Conclusions. The results we have shown above are of interest
for a number of reasons. First, we have investigated the growth

5
810 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 19
Zhang et al.
overnight under N
2
in dry acetonitrile (5 mL).29 Upon removal of
solvent, the residue was partitioned between water and diethyl ether,
and the organic layer was washed with water and concentrated.
The product was purified by using flash column chromatography
inhibition behavior of 49 nitrogen-containing bisphosphonates
NBPs) against three human tumor cell lines: MCF-7 (breast),
(
NCI-H460 (lung), and SF-268 (CNS). The IC50 values of the
most potent NBPs are in the range 10-20 µM. However,
formation of a POM ester of one NBP resulted in a decrease in
IC50 from 145 to 6.8 µM, suggesting that related ester analogues
may be worth investigating in these and other tumor cell lines.
Second, we synthesized and tested a series of nine novel
bisphosphonates containing the very hydrophobic, terphenyl side
chain. Broadly speaking, these compounds had a similar range
in activity as did the NBPs. However, the most active compound
was again an ester, which was found to have an IC50 value of
(silica gel; hexane/ethyl acetate (10/1), then ethyl acetate).
General Method E (Synthesis of Terphenylbisphosphonates;
Scheme 4): The methyl ester of a carboxylic acid (1 mmol) was
hydrolyzed with 3 N NaOH (1 mL) in methanol (5 mL) at room
temperature for 1 h. After acidification with 2 N HCl, methanol
was removed, and the resulting carboxylic acid was filtered and
then washed with water. The dried acid was dissolved in benzene
(5 mL) and oxalyl chloride (2 mmol) was added, followed by one
drop of DMF. The reaction mixture was then stirred for 1 h. Upon
removal of solvent, the crude acid chloride so obtained was
2
.2 µM. Third, we synthesized a series of bisphosphonates
dissolved in dry THF (5 mL) and P(OTMS)
After 3 h at room temperature, the solvent was removed, methanol-
O (2 mL, 1:1) was added, and the mixture was stirred for 30
3
(2 mmol) was added.
containing electron-withdrawing (halo, cyano) phenyl groups.
The free acids had poor activity (>400 µM), but the POM and
POC esters were much more active, with IC50 values as low as
H
2
min. Concentrated aqueous NaOH was then added to precipitate
the target compound, which was washed thoroughly with methanol
and then ether and dried to afford the bisphosphonic acids as their
sodium salts.
Tetrakis-pivaloyloxymethyl 2-(Pyridin-2-ylamino)ethylidene-
1,1-bisphosphonate (8). The tetrakis-pivaloyloxymethyl ester of
vinylidene-1,1-bisphosphonic acid was made from tetramethyl
vinylidene-1,1-bisphosphonate (488 mg, 2 mmol), following Gen-
eral Method D but without chromatographic purification. The
product was then reacted with 2-aminopyridine (141 mg, 1.5 mmol)
5
00 nM, >800 times the activity of the free acid form and
likewise more active than the most active NBPs. Overall, these
results are of interest because they represent the first report of
the activity of a wide range of novel bisphosphonates against
tumor cell growth. The IC50 values found for the NNBPs (in
their ester forms) are as low as 500 nM (dibromophenyl) or 2.2
µM (terphenyl), considerably lower than the values found for
the free acid NBPs in the same assays. Given the extensive
literature on the effects of NBPs on tumor cell growth inhibition,
further work on the lipid soluble NNBPs may be of interest,
including, for example, their potential use in topical applications
in vivo, as well as their activity against parasitic protozoa.
3
in CHCl (2 mL) at room temperature overnight. The reaction
mixture was subjected to flash chromatography (silica gel; hexane/
ethyl acetate (10/1), then ethyl acetate) to afford 8 (295 mg, 20%
1
1
overall yield). Quantitative H NMR indicated 95% purity. H NMR
400 MHz, CDCl ): δ 1.30-1.40 (m, 36H, CH ), 2.08 (tt, J )
4.4, 6.4 Hz, 1H, NHCH CH), 3.90-4.02 (m, 2H, NHCH ), 5.60-
5.70 (m, 8H, OCH O), 6.47 (d, J ) 8.8 Hz, 1H, aromatic), 6.55-
6.58 (m, 1H, aromatic), 7.35-7.40 (m, 1H, aromatic), 8.01 (dm, J
(
3
3
Experimental Section
2
2
2
All reagents used were purchased from Aldrich (Milwaukee, WI).
The purities of all compounds were routinely monitored by using
2
1
31
31
H and P NMR spectroscopy at 400 or 500 MHz on Varian (Palo
3
) 8.8 Hz, 1H, aromatic). P NMR (CDCl ): δ 19.38.
Alto, CA) Unity spectrometers using, in some instances, absolute
spin-count quantitative analyses. The elemental analysis results for
all new compounds are provided in the Supporting Information
1-Hydroxy-2-[3-(4-fluorophenyl)pyridinium-1-yl]ethylidene-
1,1-bisphosphonic Acid Monosodium Salt (9). Compound 9 was
prepared from 3-bromopyridine (2 mmol) and 4-fluorophenyl
2
7
(Table S1).
boronic acid (2.4 mmol) following a published procedure (303
1
The synthesis of 1, 2, 11-13, 17, 18, 22-27, 35-38, 43, 45,
mg, 38% overall yield). Anal. (C13
H
13FNNaO
7
P
2
) C, H, N. H NMR
), 7.10-7.15 (m,
4
7, and 48 have been described previously,11,13,16,27 and the samples
(400 MHz, D O): δ 4.90 (t, J ) 9.6 Hz, 2H, CH
2
2
used here were from the previous batches. The five following
general methods detailed below were used to make all new
compounds:
General Method A (Suzuki Coupling; Schemes 1, 3, and 4):
An aryl boronic acid or its ester (6 mmol), a bromo-substituted
2H, aromatic), 7.55-7.60 (m, 2H, aromatic), 7.80-7.85 (m, 1H,
aromatic), 8.54 (d, J ) 8.4 Hz, 1H, aromatic), 8.64 (d, J ) 6.4 Hz,
1H, aromatic), 8.94 (s, 1H, aromatic). P NMR (D O): δ 14.06.
2
31
19
2
F NMR (D O): δ -112.46.
1-Hydroxy-2-[3-(4-trifluoromethylphenyl)pyridinium-1-yl]-
aromatic compound (5 mmol), K
(
2
CO
50 mg) in toluene (10 mL) and H O (3 mL) were refluxed under
overnight. Upon extraction with diethyl ether, the product was
3
(15 mmol), and Pd(PPh
3
)
4
ethylidene-1,1-bisphosphonic Acid Disodium Salt (10). Com-
pound 10 was prepared from 3-bromopyridine (2 mmol) and
4-trifluoromethylphenyl boronic acid (2.4 mmol) following a
2
N
2
purified by column chromatgraphy.
published procedure27 (358 mg, 36% overall yield). Anal. (C14
H
12
F
3
-
1
General Method B (Synthesis of 2-(Pyridinium-1-yl)eth-
ylidene-1,1-bisphosphonic Acid): A substituted pyridine (1.2
mmol) and vinylidene-1,1-bisphosphonic acid28 (1 mmol) in water
NNa
(t, J ) 9.6 Hz, 2H, CH
7.95 (m, 1H, aromatic), 8.63 (d, J ) 8.4 Hz, 1H, aromatic), 8.72
O
2 7
P ‚1.5H
2
2
O) C, H, N. H NMR (400 MHz, D
2
O): δ 4.93
2
), 7.70-7.75 (m, 4H, aromatic), 7.90-
3
1
(1 mL) was refluxed for 2 h. Upon removal of solvent, the residue
(d, J ) 6.4 Hz, 1H, aromatic), 9.04 (s, 1H, aromatic). P NMR
(D O): δ -63.14.
O): δ 14.02. 19F NMR (D
2-[3-(4-Biphenyl)pyridinium-1-yl)]ethylidene-1,1-bisphospho-
was triturated with ethanol (3 mL), and the resulting white
suspension was filtered and washed with ethanol (2 × 2 mL),
affording pure 2-(pyridinium-1-yl)ethylidene-1,1-bisphosphonic acid
as a white powder.
General Method C (Alkylation of Tetramethyl Methylene-
bisphosphonate; Schemes 3 and 5): Tetramethyl methylenebi-
sphosphonate (2 mmol) in dry DMF (2 mL) was treated with NaH
2
2
nic Acid (14). Compound 14 was prepared from 3-(4-biphenyl)-
pyridine (1.2 mmol), following General Method B as a white
1
powder (210 mg, 45%). Anal. (C19
(500 MHz, D
(m, 2H, CH ), 7.22-7.43 (m, 3H, aromatic), 7.52-7.76 (m, 7H,
aromatic), 8.26-8.42 (m, 1H, aromatic), 8.67 (s, 1H, aromatic),
9.00 (m, 1H, aromatic). 31P NMR (202 MHz, D
O): δ 15.25.
6 2
H19NO P ) C, H, N. H NMR
2
O): δ 2.20 (tt, J ) 21, 6.5 Hz, 1H, CH), 4.80-4.85
2
(
2.2 mmol) in an ice bath. A benzyl bromide (2 mmol) was added
to the resulting solution. The reaction mixture was stirred at room
temperature for 1 h before being quenched with saturated NH Cl.
2
4
2-(3-Butylpyridinium-1-yl)ethylidene-1,1-bisphosphonic Acid
(15). Compound 15 was prepared from 3-butylpyridine (1.2 mmol)
following General Method B as a white powder (240 mg, 72%).
The product was extracted with diethyl ether and purified by column
chromatography.
General Method D (Transesterification; Schemes 3 and 5):
The tetramethyl ester of a bisphosphonic acid (1 mmol), NaI (4
mmol), and chloromethyl pivalate (5 mmol; or chloromethyl
isopropyl carbonate, when making POC esters) were refluxed
Anal. (C11
O): δ 0.72 (t, J ) 6.5 Hz, 3H, CH
1.45-1.50 (m, 2H, CH ), 2.60-2.80 (m, 3H, CH and CH
4.85 (m, 2H, NCH ), 7.69 (t, J ) 6 Hz, 1H, aromatic), 8.20 (d, J
H19NO
6
P
2
‚0.5H
2
O) C, H, N. 1H NMR (500 MHz,
D
2
3
), 1.10-1.15 (m, 2H, CH
2
),
), 4.65-
2
2
2

Bisphosphonate Effects on Tumor Cell Growth
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 19 5811
)
8 Hz, 1H, aromatic), 8.50-8.60 (m, 2H, aromatic). 31P NMR
202 MHz, D O): δ 14.80.
-(3-Phenylpyridinium-1-yl)ethylidene-1,1-bisphosphonic Acid
16). Compound 16 was prepared from 3-phenylpyridine (1.2 mmol)
2-[4-Benzylpyridinium-1-yl]ethylidene-1,1-bisphosphonic Acid
(33). Compound 33 was prepared from 4-benzylpyridine (1.2 mmol)
following General Procedure B as a white powder (202 mg, 52%).
(
2
2
1
(
Anal. (C14
H
16.25NNa0.75
P
2
O
6
) C, H, N. H NMR (400 MHz, D
2
O):
), 4.70-
4.80 (m, 2H, CH CH), 7.10-7.30 (m, 5H, aromatic), 7.61 (d, J )
following General Method B as a white powder (274 mg, 80%).
δ 2.20 (tt, J ) 21, 6.5 Hz, 1H, CH), 4.08 (s, 2H, PhCH
2
1
Anal. (C13
H15NO
6
P
2
) C, H, N. H NMR (500 MHz, D
2
O): δ 2.48
), 7.40-
.60 (m, 5H, aromatic), 7.80-7.90 (m, 1H, aromatic), 8.58 (d, J )
Hz, 1H, aromatic), 8.66 (d, J ) 6 Hz, 1H, aromatic), 8.97 (s,
H, aromatic). 31P NMR (202 MHz, D
O): δ 14.72.
-Hydroxy-2-[(3-bromoropyridinium-1-yl)]ethylidene-1,1-bis-
2
3
1
(
tt, J ) 21, 6.5 Hz, 1H, CH), 4.80-5.00 (m, 2H, NCH
2
6.8 Hz, 2H, aromatic), 8.46 (d, J ) 6.8 Hz, 2H, aromatic).
NMR (162 MHz, D
2-(3-Trifluoromethylpyridinium-1-yl)ethylidene-1,1-bispho-
P
7
8
1
2
O): δ 14.5.
sphonic Acid (34). Compound 34 was prepared from 3-trifluo-
2
romethylpyridine (1.2 mmol) following General Method B as a
1
1
white powder (231 mg, 69%). Anal. (C
NMR (500 MHz, D
8
H F
10 3
NO
6
P
2
) C, H, N. H
phosphonic Acid Monosodium Salt (19). Compound 19 was
prepared from 3-bromopyridine (1.2 mmol) following a published
2
O): δ 2.84 (tt, J ) 21, 6.5 Hz, 1H, CH), 4.95-
27
5.00 (m, 2H, CH ), 8.12 (t, J ) 6 Hz, 1H, aromatic), 8.77 (d, J )
procedure (168 mg, 42%). Anal. (C
H
7 9
BrNNaO
O): δ 4.67 (t, J ) 8 Hz, 2H, CH
t, J ) 7 Hz, 1H, aromatic), 8.60 (d, J ) 8 Hz, 1H, aromatic), 8.87
d, J ) 6 Hz, 1H, aromatic). 31P NMR (202 MHz, D
O): δ 14.75.
-(3-Methylpyridinium-1-yl)ethylidene-1,1-bisphosphonic Acid
20). Compound 20 was prepared from 3-methylpyridine (1.2 mmol)
P
7 2
‚H
2
O) C, H,
2
1
8 Hz, 1H, aromatic), 9.07 (s, 1H, aromatic), 9.40 (s, 1H, aromatic).
N. H NMR (500 MHz, D
(
(
2
2
), 7.59
3
1
2
P NMR (202 MHz, D O): δ 14.98.
2-[3-(2-Phenylphenyl)pyridinium-1-yl]ethylidene-1,1-bispho-
2
sphonic Acid (39). Compound 39 was prepared from 3-(2-
phenylphenyl)pyridine (1.2 mmol) following General Method B
2
(
as a white powder (200 mg, 48%). Anal. (C19
H
19NO
6
P
2
) C, H, N.
O): δ 2.15 (tt, J ) 21, 6.5 Hz, 1H, CH),
), 6.88-7.03 (m, 2H, aromatic), 7.06-7.16
m, 3H, aromatic), 7.30-7.50 (m, 5H, aromatic), 7.68-7.73 (m,
following General Method B as a white powder (230 mg, 78%).
1
O) C, H, N. 1H NMR (400 MHz,
H NMR (500 MHz, D
.61-4.70 (m, 2H, CH
2
Anal. (C ‚0.75H
O): δ 2.36 (s, 3H, CH ), 2.68 (tt, J ) 25.2, 7.2 Hz, 1H, CH),
.70-4.90 (m, 2H, NCH ), 7.70-7.75 (m, 1H, aromatic), 8.17 (d,
J ) 8 Hz, 1H, aromatic), 8.54 (d, J ) 6 Hz, 1H, aromatic), 8.59
H13NO P
8 6 2
2
4
(
1
2
D
2
3
4
2
3
1
H, aromatic), 8.56 (s, 1H, aromatic), 8.78 (m, 1H, aromatic).
O): δ 15.31.
-Hydroxy-2-[(6-methylquinolinium-1-yl)]ethylidene-1,1-bis-
phosphonic Acid (40). Compound 40 was prepared from 6-
P
s, 1H, aromatic). 3 P NMR (162 MHz, D
1
NMR (202 MHz, D
2
(
2
O): δ 14.85.
1
2-(3-Ethylpyridinium-1-yl)ethylidene-1,1-bisphosphonic Acid
Monosodium Salt (21). Compound 21 was prepared from 3-eth-
ylpyridine (1.2 mmol) following General Method B as a white
2
7
methylquinoline (1 mmol) following a published procedure (66
1
mg, 19%). Anal. (C12
MHz): δ 2.44 (s, 3H, CH
.92 (m, 2H, aromatic), 8.33 (s, 1H, aromatic), 8.70-8.90 (m, 2H,
H
15NO
6
P
2
‚H
2
O) C, H, N. H NMR (500
1
powder (238 mg, 75%). Anal. (C
400 MHz, D O): δ 1.11 (t, J ) 6.4 Hz, 3H, CH
H, CH and CH ), 4.70-4.90 (m, 2H, NCH ), 7.70-7.75 (m, 1H,
aromatic), 8.17 (d, J ) 8 Hz, 1H, aromatic), 8.54 (d, J ) 6 Hz,
H, aromatic), 8.58 (s, 1H, aromatic). 31P NMR (162 MHz, D
O):
δ 14.80.
-Hydroxy-2-[(3-chloropyridinium-1-yl)]ethylidene-1,1-bis-
phosphonic Acid (28). Compound 28 was prepared from 3-chlo-
9
H14NNaO P
6 2
) C, H, N. H NMR
3
), 5.28 (t, J ) 8 Hz, 2H, CH
2
), 7.41-
(
3
2
3
), 2.60-2.80 (m,
7
2
2
3
1
aromatic), 9.08 (d, J ) 6.0 Hz, 1H, aromatic). P NMR (202 MHz,
O): δ 15.15.
-[4-(2-Phenylphenyl)pyridinium-1-yl]ethylidene-1,1-bisphos-
D
2
1
2
2
phonic Acid (41). Compound 41 was prepared from 4-(2-
phenylphenyl)pyridine (1.2 mmol) following General Method B
1
as a white powder (187 mg, 44%). Anal. (C19
H
19NO
6
P
2
‚0.3H
O): δ 2.10 (tt, J ) 21, 6.5 Hz,
), 6.88-7.03 (m, 2H, aromatic),
.04-7.06 (m, 2H, aromatic), 7.06-7.21 (m, 3H, aromatic), 7.37-
2
O)
2
7
ropyridine (1 mmol) following a published procedure (83 mg,
1
C, H, N. H NMR (500 MHz, D
2
1
2
5.4%). Anal. (C
MHz, D O): δ 4.77 (t, J ) 8 Hz, 2H, CH
aromatic), 8.27 (d, J ) 8 Hz, 1H, aromatic), 8.68 (d, J ) 6 Hz,
H, aromatic). 31P NMR (202 MHz, D
O): δ 15.17.
-(Pyridinium-1-yl)ethylidene-1,1-bisphosphonic Acid (29).
Compound 29 was prepared from pyridine (1.2 mmol) following
General Method B as a white powder (228 mg, 85%). Anal. (C
7
H10ClNO
7 2
P
‚0.5H
2
O) C, H, N. H NMR (500
1
7
7
H, CH), 4.61-4.70 (m, 2H, CH
2
2
2
), 7.76 (t, J ) 6 Hz, 1H,
3
1
.51 (m, 4H, aromatic), 8.52 (d, J ) 7 Hz, 2H, aromatic). P NMR
1
2
(
202 MHz, D
2
O): δ 15.31.
2
1
-Hydroxy-2-(7-methylquinolinium-1-yl)ethylidene-1,1-bis-
phosphonic Acid (42). Compound 42 was prepared from 7-
7
H
11
-
27
methylquinoline (1 mmol) following a published procedure (88
1
NO
J ) 25.2, 7.2 Hz, 1H, CH), 4.70-4.90 (m, 2H, NCH
6.4 Hz, 2H, aromatic), 8.37 (t, J ) 8 Hz, 1H, aromatic), 8.75 (d,
P
6 2
‚0.25H
2
O) C, H, N. H NMR (400 MHz, D
2
O): δ 2.71 (tt,
1
mg, 24%). Anal. (C12
O): δ 2.45 (s, 3H, CH
J ) 8.5 Hz, 1H, aromatic), 7.74 (t, J ) 7.5 Hz, 1H, aromatic),
.00 (t, J ) 8.5 Hz, 1H, aromatic), 8.30 (s, 1H, aromatic), 8.84 (d,
8 2
H17NO P ) C, H, N. H NMR (500 MHz,
2
), 7.87 (t, J
D
2
3
2
), 5.31 (t, 2H, J ) 10 Hz, CH ), 7.64 (d,
)
31
J ) 6 Hz, 2H, aromatic). P NMR (162 MHz, D
-[(3-Chloropyridinium-1-yl)]ethylidene-1,1-bisphosphonic Acid
30). Compound 30 was prepared from 3-chloropyridine (1.2 mmol)
following General Procedure B as a white powder (205 mg, 68%).
Anal. (C 10ClNO ‚0.5H
O) C, H, N. 1H NMR (500 MHz,
O): δ 2.15 (tt, J ) 21, 6.5 Hz, 1H, CH), 4.53-4.78 (m, 2H,
CH ), 7.76 (t, J ) 6 Hz, 1H, aromatic), 8.30 (d, J ) 8 Hz, 1H,
aromatic), 8.74 (d, J ) 6 Hz, 1H, aromatic). P NMR (202 MHz,
O): δ 15.03.
-(3-Iodopyridinium-1-yl)ethylidene-1,1-bisphosphonic Acid
31). Compound 31 was prepared from 3-iodopyridine (1.2 mmol)
following General Method B as a white powder (284 mg, 75%).
2
O): δ 14.78.
8
2
31
J ) 7.5 Hz, 1H, aromatic), 9.10 (d, J ) 6.0 Hz, 1H, aromatic).
NMR (202 MHz, D O): δ 15.15.
-Hydroxy-2-(4-phenylpyridinium-1-yl)ethylidene-1,1-bisphos-
phonic Acid (44). Compound 44 was prepared from 4-phenylpy-
P
(
2
1
7
H
P
6 2
2
D
2
27
ridine (1 mmol) following a published procedure (158 mg, 41%
1
2
overall yield). Anal. (C13
H
18NO
P
‚1.5H
O) C, H, N. H NMR (400
CH), 7.10-7.30 (m, 5H,
7
2
2
31
MHz, D O): δ 4.70-4.85 (m, 2H, CH
2
2
D
2
aromatic), 7.71 (d, J ) 6.8 Hz, 2H, aromatic), 8.50 (d, J ) 6.8 Hz,
2H, aromatic). 31P NMR (162 MHz, D2O): δ 14.7.
2
(
1-Hydroxy-2-(4-methoxypyridinium-1-yl)ethylidene-1,1-bis-
phosphonic Acid (46). Compound 46 was prepared from 4-meth-
1
27
Anal. (C
7
H
10INO
6
P
2
) C, H, N. H NMR (500 MHz, D
2
O): δ 2.15
), 7.52 (t, J
7 Hz, 1H, aromatic), 8.58 (d, J ) 8 Hz, 1H, aromatic), 8.77 (d,
oxypyridine (1 mmol) following a published procedure (88 mg,
1
(
tt, J ) 21, 6.5 Hz, 1H, CH), 4.67-4.78 (m, 2H, CH
2
28%). Anal. (C H NO P ) C, H, N. H NMR (500 MHz): δ 3.94
8
13
8 2
)
(s, 3H, OMe), 5.22 (t, J ) 10 Hz, 2H, CH ), 7.22 (d, J ) 6 Hz,
2H, aromatic), 8.44 (d, J ) 6 Hz, 2H, aromatic). P NMR (202
2
31
31
J ) 6 Hz, 1H, aromatic). P NMR (202 MHz, D
2
O): δ 15.32.
-(3-Bromopyridinium-1-yl)ethylidene-1,1-bisphosphonic Acid
32). Compound 32 was prepared from 3-bromopyridine (1.2 mmol)
following General Method B as a white powder (241 mg, 70%).
2
2
MHz, D O): δ 15.15.
(
1-Hydroxy-2-[4-(pyridine-4-yl)pyridinium-1-yl)ethylidene-1,1-
bisphosphonic Acid Disodium Salt (49). Compound 49 was
prepared from 4,4′-bipyridyl (1 mmol) following a published
1
Anal. (C
7
H
10BrNO
6
P
2
) C, H, N. H NMR (500 MHz, D
2
O): δ 2.17
), 7.53 (t, J
7 Hz, 1H, aromatic), 8.57 (d, J ) 8 Hz, 1H, aromatic), 8.77 (d,
2
7
(
tt, J ) 21, 6.5 Hz, 1H, CH), 4.52-4.77 (m, 2H, CH
2
procedure (113 mg, 25%). Anal. (C12
H
13
N
2
Na
O): δ 4.93 (t, J ) 10 Hz, 2H, CH
8.27 (d, J ) 6.5 Hz, 2H, aromatic), 8.36 (d, J ) 6.5 Hz, 2H,
2
O
7
P
2
‚2.5H
2
O) C,
1
)
H, N. H NMR (500 MHz, D
2
2
),
31
J ) 6 Hz, 1H, aromatic). P NMR (202 MHz, D
2
O): δ 14.98.

5
812 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 19
Zhang et al.
aromatic), 8.85 (d, J ) 6.5 Hz, 2H, aromatic), 8.94 (d, J ) 6.5 Hz,
H, aromatic). 31P NMR (202 MHz, D
O): δ 13.68.
-(Isoquinolinium-2-yl)ethylidene-1,1-bisphosphonic Acid (50).
Compound 50 was prepared from isoquinoline (1.2 mmol) following
14
General Method B as a white powder (262 mg, 82%). Anal. (C11H -
1-Hydroxy-2-[3-(2-phenylphenyl)phenyl]ethylidene-1,1-bis-
phosphonic Acid Disodium Salt (57). Compound 57 was prepared
from methyl 3-(2-phenylphenyl)phenylacetate (1 mmol) following
2
2
2
General Method E as a white powder (213 mg, 43%). Anal.
1
(
C
20
H
18
O
7
P
2
Na
2
‚H
2
O) C, H. H NMR (400 MHz, D
2
2
O): δ 3.10 (t,
3
1
1
J ) 12 Hz, 2H, CH ), 6.73-7.40 (m, 13H, aromatic). P NMR
NO
21, 6.5 Hz, 1H, CH), 4.80-5.00 (m, 2H, NCH
H, aromatic), 9.61 (s, 1H, aromatic). 31P NMR (202 MHz, D
δ 15.01.
-(4-Trifluoromethylpyridinium-1-yl)ethylidene-1,1-bisphos-
P
6 2
‚0.5H
2
O) C, H, N. H NMR (500 MHz, D
2
O): δ 2.79 (tt, J
), 7.80-8.40 (m,
O):
(
162 Hz, D
2
O): δ 19.23.
)
6
2
1-Hydroxy-2-[3-(3-phenylphenyl)phenyl]ethylidene-1,1-bis-
2
phosphonic Acid Monosodium Salt (58). Compound 58 was
prepared from methyl 3-(3-phenylphenyl)phenylacetate (1 mmol)
2
following General Method E as a white powder (265 mg, 56%).
phonic Acid (51). Compound 51 was prepared from 4-trifluoro-
methylpyridine (1.2 mmol) following General Method B as a white
1
Anal. (C20
.23 (t, J ) 12 Hz, 2H, CH
NMR (162 Hz, D O): δ 19.20.
-Hydroxy-3-[3-(2-phenylphenyl)phenyl]propylidene-1,1-bis-
H
19NaO
7
P
2
‚H
2
O) C, H. H NMR (400 MHz, D
2
O): δ
3
1
3
2
), 7.20-7.80 (m, 13H, aromatic). P
powder (213 mg, 62%). Anal. (C
8
H
10
F
3
NO
O): δ 2.17 (tt, J ) 21, 6.5 Hz, 1H, CH),
), 8.27 (d, J ) 6.5 Hz, 2H, aromatic), 9.10
6
P
2
‚0.5H
2
O) C, H, N.
1
2
H NMR (500 MHz, D
.94-5.01 (m, 2H, CH
d, J ) 6.5 Hz, 2H, aromatic). P NMR (202 MHz, D
-[3-(Pyrollidin-1-ylsulfonyl)pyridinium-1-yl]ethylidene-1,1-
bisphosphonic Acid (52). Compound 52 was prepared from
-(pyrollidin-1-ylsulfonyl)pyridine36 (1.2 mmol) following General
Method B as a white powder (270 mg, 66%). Anal. (C11 S‚
O) C, H, N. H NMR (500 MHz): δ 1.60-1.65 (m, 4H,
), 2.73 (tt, J ) 21, 6.5 Hz, 1H, CH), 3.10-3.20 (m, 4H, 2CH
), 8.10-8.15 (m, 1H, aromatic), 8.80
d, J ) 6.5 Hz, 1H, aromatic), 9.06 (d, J ) 6.5 Hz, 1H, aromatic),
.43 (s, 1H, aromatic). 31P NMR (202 MHz, D
O): δ 14.19.
-[4-(4-Phenylphenyl)pyridinium-1-yl)]ethylidene-1,1-bisphos-
2
1
4
(
2
31
phosphonic Acid Trisodium Salt (59). Compound 59 was prepared
from methyl 3-(2-phenylphenyl)phenylpropionate (1 mmol) fol-
lowing General Method E as a white powder (271 mg, 51%). Anal.
2
O): δ 14.75.
2
1
(
2
C
21
H
19
O
7
P
2
Na
.10 (m, 2H, CH
Hz, 1H, aromatic), 6.97 (t, J ) 7.5 Hz, 1H, aromatic), 7.04-7.17
3
‚H
2
2
O) C, H. H NMR (500 MHz, D
2
O): δ 1.98-
3
), 2.69-2.72 (m, 2H, ArCH
2
), 6.70 (d, J ) 6.5
18 2 8 2
H N O P
1
0
2
.5H
CH
2
31
(
m, 7H, aromatic), 7.32-7.45 (m, 4H, aromatic). P NMR (202
MHz, D O): δ 19.38.
-Hydroxy-3-[3-(4-phenylphenyl)phenyl]propylidene-1,1-bis-
2
2
-
2
NS), 4.94-5.01 (m, 2H, NCH
2
1
(
phosphonic Acid Disodium Salt (60). Compound 60 was prepared
from methyl 3-(4-phenylphenyl)phenylpropionate (1 mmol) fol-
9
2
2
lowing General Method E as a white powder (270 mg, 55%). Anal.
phonic Acid (53). Compound 53 was prepared from 4-(4-
phenylphenyl)pyridine (1.2 mmol) following General Method B
1
(
(
C
21
H
20
O
7
P
2
Na
2
2
) C, H. H NMR (400 MHz, D
2
O): δ 2.05-2.10
m, 2H, CH
), 2.80-2.85 (m, 2H, ArCH
2
), 7.22-7.32 (m, 6H,
as a white powder (222 mg, 53%). Anal. (C19
H
19NO
6
P
2
) C, H, N.
O): δ 2.19 (tt, J ) 21, 6.5 Hz, 1H, CH),
), 7.31 (t, J ) 6 Hz, 1H, aromatic), 7.38 (t,
J ) 6 Hz, 2H, aromatic), 7.57 (d, J ) 7.5 Hz, 2H, aromatic), 7.66
d, J ) 8.5 Hz, 2H, aromatic), 7.80 (d, J ) 8.5 Hz, 2H, aromatic),
.00 (d, J ) 7 Hz, 2H, aromatic), 8.68 (d, J ) 7 Hz, 2H, aromatic).
31
aromatic), 7.35-7.64 (m, 7H, aromatic). P NMR (162 MHz,
O): δ 19.08.
-Hydroxy-[3-(3-phenylphenyl)phenyl]methylene-1,1-bisphos-
1
H NMR (500 MHz, D
.51-4.60 (m, 2H, CH
2
D
2
4
2
1
phonic Acid Monosodium Salt (61). Compound 61 was prepared
from methyl 3-(3-phenylphenyl)benzoate (1 mmol) following
General Method E as a white powder (174 mg, 40%). Anal.
(
8
31
2
P NMR (202 MHz, D O): δ 15.31.
1
(
C
19
H
17
O
7
P
2
Na‚0.25H
2
O) C, H. H NMR (400 MHz, D
2
O): δ
2-[4-(3-Phenylphenyl)pyridinium-1-yl)]ethylidene-1,1-bisphos-
7
7
7
7
.17-7.25 (m, 2H, aromatic), 7.33 (t, JH-H ) 7.2 Hz, 2H, aromatic),
phonic Acid Monosodium Salt (54). Compound 54 was prepared
from 4-(3-phenylphenyl)pyridine (1.2 mmol) following General
.40 (t, J ) 8 Hz, 1H, aromatic), 7.47 (d, J ) 7.8 Hz, 1H, aromatic),
.56-7.58 (m, 4H, aromatic), 7.65 (d, J ) 8 Hz, 1H, aromatic),
Method B as a white powder (306 mg, 68%). Anal. (C19
H
18NO
6
P
2
-
31
.83 (s, 2H, aromatic). P NMR (162 MHz, D
2
O): δ 17.59.
1
Na‚0.5H
2
O) C, H, N. H NMR (500 MHz, D
1, 6.5 Hz, 1H, CH), 4.49-4.61 (m, 2H, CH ), 7.26 (t, J ) 15 Hz,
H, aromatic), 7.32 (t, J ) 15 Hz, 2H, aromatic), 7.47 (d, J ) 7.5
2
O): δ 2.19 (tt, J )
1
-Hydroxy-2-[4-(3-phenylphenyl)phenyl]ethylidene-1,1-bis-
2
2
2
phosphonic Acid Monosodium Salt (62). Compound 62 was
prepared from methyl 4-(3-phenylphenyl)phenylacetate (1 mmol)
following General Method E as a white powder (201 mg, 44%).
Hz, 2H, aromatic), 7.66 (m, 2H, aromatic), 7.80 (s, 1H, aromatic),
.95 (d, J ) 7 Hz, 2H, aromatic), 8.68 (d, J ) 7 Hz, 2H, aromatic).
7
1
Anal. (C20
J ) 12.4 Hz, CH
19 7 2 2
H O P Na) C, H. H NMR (400 MHz, D O): δ 3.21 (t,
3
1
P NMR (202 MHz, D
Tetrakis-pivaloyloxymethyl 2-[3-(3-Phenylphenyl)phenyl]eth-
ylidene-1,1-bisphosphonate (55). 3-Biphenyl boronic acid (2.0 g,
0 mmol), 3-bromotoluene (1.7 g, 10 mmol), K CO (3.0 g, 21.7
mmol), and Pd(PPh (100 mg) were refluxed in toluene-H
50 mL, 5/1) overnight under N . Upon extraction with diethyl ether,
the crude product was then refluxed overnight with N-bromosuc-
cimide (1.95 g, 11 mmol) and AIBN (100 mg) in anhydrous CCl
2
O): δ 15.24.
2
), 7.27 (t, J ) 7.2 Hz, 1H, aromatic), 7.34-7.60
(m, 11H, aromatic), 7.80 (s, 1H, aromatic). P NMR (162 MHz,
31
D O): δ 19.11.
2
1
2
3
1-Hydroxy-2-[4-(2-phenylphenyl)phenyl]ethylidene-1,1-bis-
phosphonic Acid Disodium Salt (63). Compound 63 was prepared
from methyl 4-(2-phenylphenyl)phenylacetate (1 mmol) following
General Method E as a white powder (232 mg, 45%). Anal.
3
)
4
2
O
(
2
1
4
(C H O P Na ‚2H O) C, H. H NMR (400 MHz, D O): δ 3.06
2
0
18
7
2
2
2
2
(30 mL). After washing successively with 5% HCl then 10%
(t, J ) 12.4 Hz, CH ), 6.94 (d, J ) 8 Hz, 2H, aromatic), 7.01-
2
3
NaHCO , the organic layer was dried and concentrated to give crude
7.07 (m, 2H, aromatic), 7.11-7.17 (m, 4H, aromatic), 7.30-7.39
(m, 5H, aromatic). 31P NMR (162 MHz, D O): δ 18.97.
3-(3-phenylphenyl)benzyl bromide as a white powder. This was
2
then reacted following General Method C, followed by General
Tetrakis-pivaloyloxymethyl 2-(3,4-dibromophenyl)ethylidene-
1,1-bisphosphonate (64). Compound 64 was prepared from 3,4-
dibromobenzyl bromide (1 mmol) following General Method C,
followed by General Method D, as a pale yellow powder (159 mg,
Method D, affording compound 55 as a pale yellow powder (472
1
mg, 27% overall yield). Quantative H NMR indicated 94% purity.
1
H NMR (400 MHz, CDCl
3
): δ 1.2-1.30 (m, 36H, CH
CH), 3.15 (td, J ) 17.2, 6.8 Hz, 2H,
), 5.62-5.69 (m, 8H, POCH ), 7.23-7.85 (m, 13H, aro-
matic). 31P NMR (162 MHz, CDCl3): δ 20.52.
-Hydroxy-3-[3-(3-phenylphenyl)phenyl]propylidene-1,1-bis-
3
), 2.80 (tt,
J ) 24.8, 6.8 Hz, 1H, ArCH
ArCH
2
18% overall yield). Anal. (C H Br O P ) C, H.
1
H NMR (400
3
2
50
2
14 2
2
2
MHz, CDCl ): δ 1.20-1.30 (m, 36H, CH ), 2.79 (tt, J ) 24.8, 6.8
3
3
Hz, 1H, ArCH CH), 3.08 (td, J ) 17.2, 6.8 Hz, 2H, ArCH ), 5.62-
2
2
1
5.69 (m, 8H, POCH
J ) 8.4 Hz, 1H, aromatic), 7.56 (s, 1H, aromatic). P NMR (162
3
MHz, CDCl ): δ 20.35.
2
), 7.10 (d, J ) 8.4 Hz, 1H, aromatic), 7.43 (d,
31
phosphonic Acid Trisodium Salt (56). Compound 56 was prepared
from methyl 3-(3-phenylphenyl)phenylpropionate (1 mmol) fol-
lowing General Method E as a white powder (324 mg, 61%). Anal.
Tetrakis-pivaloyloxymethyl 2-(3,4-dichlorophenyl)ethylidene-
1,1-bisphosphonate (65). Compound 65 was prepared from 3,4-
dichlorobenzyl bromide (1 mmol) following General Method C,
1
(
2
1
C
21
H
19
O
7
P
2
Na
.12 (m, 2H, CH
2H, aromatic), 7.77 (s, 1H, aromatic). P NMR (162 Hz, D
3
‚H
2
2
O) C, H. H NMR (400 Hz, D
2
O): δ 2.01-
), 7.23-7.57 (m,
O):
), 2.80-2.85 (m, 2H, ArCH
2
31
2
followed by General Method D, as a pale yellow powder (153 mg,
1
δ 19.41.
21%). Anal. (C32H50Cl
2
O P
14 2
) C, H. H NMR (400 MHz, CDCl
3
):

Bisphosphonate Effects on Tumor Cell Growth
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 19 5813
δ 1.20-1.30 (m, 36H, CH
3
), 2.80 (tt, J ) 24.8, 6.8 Hz, 1H,
CH), 3.15 (td, J ) 17.2, 6.8 Hz, 2H, ArCH ), 5.62-5.69
m, 8H, POCH ), 7.10 (d, J ) 8.4 Hz, 1H, aromatic), 7.33-7.35
m, 2H, aromatic). P NMR (162 MHz, CDCl
Tetrakis-isopropoxycarbonyloxymethyl 2-(3,4-dichlorophen-
response curves. The DMSO carrier had no effect on cell
proliferation. GraphPad PRISM version 4.0 software for windows
(GraphPad Software, Inc., San Diego, CA, www.graphpad.com)
was used to fit the data to a rectangular hyperbolic function:
ArCH
2
2
(
(
2
3
1
3
): δ 20.41.
yl)ethylidene-1,1-bisphosphonate (66). Compound 66 was pre-
pared from 3,4-dichlorobenzyl bromide (1 mmol) following General
Method C, followed by General Method D, as a pale yellow powder
Imax
C
I )
IC50 + C
1
(
136 mg, 17%). Anal. (C28
CDCl ): δ 1.32 (d, J ) 6.4 Hz, 24H, CH
Hz, 1H, ArCH CH), 3.47 (td, J ) 17.2, 6.8 Hz, 2H, ArCH
.95 (m, 4H, CHMe ), 5.60-5.70 (m, 8H, OCH O), 7.13 (d, J )
.8 Hz, 1H, aromatic), 7.35 (d, J ) 6.8 Hz, 1H, aromatic), 7.38 (s,
H, aromatic). 31P NMR (162 MHz, CDCl
): δ 21.85.
Tetrakis-isopropoxycarbonyloxymethyl 2-(3,4-difluorophen-
H
42Cl
2
O
18
P
2
) C, H. H NMR (500 MHz,
), 2.75 (tt, J ) 24.4, 6.4
where I is the percent inhibition, Imax ) 100% inhibition, C is the
concentration of the inhibitor, and IC50 is the concentration for 50%
growth inhibition. Typical dose-response curves for 2 NBPs, 2
terphenyl, and 2 halophenyl NBPs are shown in the Supporting
Information (Figure S1).
3
3
2
2
), 4.89-
4
6
1
2
2
3
yl)ethylidene-1,1-bisphosphonate (67). Compound 67 was pre-
pared from 3,4-difluorobenzyl bromide (1 mmol) following General
Method C, followed by General Method D, as a pale yellow powder
Acknowledgment. This work was supported by the United
States Public Health Service (NIH Grant GM073216 to E.O.).
Y.Z. is an AHA, Midwest Affiliate, Postdoctoral Fellow. A.L.
was supported by an NIH Institutional NRSA in Molecular
Biophysics (NIH Training Grant GM-08276). Y.S. is a Leuke-
mia and Lymphoma Society Special Fellow. D.S. is a Howard
Hughes Medical Institute Undergraduate Research Scholar.
1
(
107 mg, 14%). Anal. (C28
CDCl ): δ 1.33 (d, J ) 6.4 Hz, 24H, CH
.4 Hz, 1H, ArCH
H
42
F
2
O
18
P
2
) C, H. H NMR (400 MHz,
3
3
), 2.88 (tt, J ) 24.4, J )
CH), 3.40 (td, J ) 17.2, 6.8 Hz, 2H, ArCH ),
O), 6.99-
): δ 21.94.
): -140.79∼ -140.67 (m, 1F),
6
4
7
2
2
.89-4.95 (m, 4H, CHMe1
2
), 5.60-5.72 (m, 8H, OCH
2
.13 (m, 3H, aromatic). 3 P NMR (162 MHz, CDCl
3
1
9
F NMR (376 MHz, CDCl
138.08∼ -137.97 (m, 1F).
Tetrakis-isopropoxycarbonyloxymethyl 2-(3-cyanophenyl)-
3
Supporting Information Available: Microchemical analysis
results for all new compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
-
ethylidene-1,1-bisphosphonate (68). Compound 68 was prepared
from 3-cyanobenzyl bromide (1 mmol) following General Method
C, followed by General Method D, as a pale yellow powder (91
References
1
mg, 12%). Anal. (C29
CDCl
H
43NO18
P
2
) C, H, N. H NMR (400 MHz,
(
1) Reszka, A. A.; Rodan, G. A. Nitrogen-containing bisphosphonate
3
): δ 1.31 (d, J ) 6.4 Hz, 24H, CH
.8 Hz, 1H, ArCH CH), 3.40 (td, J ) 16.8, 6.8 Hz, 2H, ArCH
.89-4.96 (m, 4H, CHMe ), 5.60-5.70 (m, 8H, OCH O), 7.36 (t,
3
), 2.79 (tt, J ) 20.8, J )
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4
2
2
),
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2
(
3) Wilhelm, M.; Kunzmann, V.; Eckstein, S.; Reimer, P.; Weissinger,
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H, aromatic). 31P NMR (162 MHz, CDCl
): δ 21.70.
-(3,4-Dibromophenyl)ethylidene-1,1-bisphosphonic Acid (69).
1
3
2
(
Compound 69 was prepared from 3,4-dibromobenzyl bromide (1
mmol) following General Method C, followed by hydrolysis with
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1
yield). Anal. (C
2
8
H
10Br
2
O
6
P
2
) C, H. H NMR (400 MHz, D
2
O): δ
CH), 3.12 (td, J ) 17.2, 6.8
), 7.10 (d, J ) 8.4 Hz, 1H, aromatic), 7.43 (d, J )
(
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2
Hz, 2H, ArCH
2
8
.4 Hz, 1H, aromatic), 7.56 (s, 1H, aromatic). 31P NMR (162 MHz,
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CDCl ): δ 19.87.
2
-(3-Cyanophenyl)ethylidene-1,1-bisphosphonic Acid Tri-
(
7) Iguchi, T.; Miyakawa, Y.; Yamamoto, K.; Kizaki, M.; Ikeda, Y.
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bromide (1 mmol) following General Method C, followed by
hydrolysis with bromotrimethylsilane, as a white powder (29%).
1
Anal. (C
9
H
8
NNa
3
O
6
P
2
‚H
2
O) C, H, N. H NMR (400 MHz, D
2
O):
CH), 3.40 (td, J ) 16.8,
), 4.89-4.96 (m, 4H, CHMe ), 5.60-5.70 (m,
O), 7.39 (t, J ) 8 Hz, 1H, aromatic), 7.45-7.52 (m, 2H,
(8) Forsea, A. M.; Muller, C.; Riebeling, C.; Orfanos, C. E.; Geilen, C.
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δ 2.79 (tt, J ) 20.8, 6.8 Hz, 1H, ArCH
2
6
8
.8 Hz, 2H, ArCH
H, OCH
2
2
(
9) Kitagawa, Y.; Hiraga, T.; Yura, Y.; Yoneda, T. Suppression by
incadronate of invasion and growth of A-375 human melanoma in
mandible in nude mice. Oncol. Rep. 2005, 13 (2), 211-216.
2
31
aromatic), 7.59 (s, 1H, aromatic). P NMR (162 MHz, D
9.81.
Cell Growth Inhibition Assays. The human tumor cell lines
2
O): δ
1
(10) Chuah, C.; Barnes, D. J.; Kwok, M.; Corbin, A.; Deininger, M. W.;
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cells. Leukemia 2005, 19 (11), 1896-1904.
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the National Cancer Institute. All lines were cultured in RPMI-
(
11) Martin, M. B.; Grimley, J. S.; Lewis, J. C.; Heath, H. T., III; Bailey,
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1640 medium supplemented with 10% fetal bovine serum and 2
mM L-glutamine at 37 °C in a 5% CO atmosphere with 100%
2
humidity. A broth microdilution method was used to determine IC50
values for growth inhibition by each bisphosphonate. Cells were
inoculated at a density of 5000 cells/well into 96-well flat bottom
culture plates containing 10 µL of the test compound, previously
half-log serial diluted (from 0.316 mM to 0.1 pM), for a final
(
12) Yardley, V.; Khan, A. A.; Martin, M. B.; Slifer, T. R.; Araujo, F.
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volume of 100 µL. NBPs were typically initially dissolved in H
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2
O
(
(
13) Martin, M. B.; Sanders, J. M.; Kendrick, H.; de Luca-Fradley, K.;
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2
atmosphere at 100% humidity after which an MTT ((3-(4,5-
dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide) cell pro-
liferation assay (ATCC, Manassas, VA)37 was used to obtain dose-

5
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(
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