Synthesis and screening of bifunctional radiolabelled carborane-carbohydrate derivatives

Article abstract of DOI:10.1016/j.jorganchem.2008.12.063

A new bifunctional carborane ligand was prepared as a platform for the development of targeted molecular radioimaging and therapy agents. The carborane derivative was synthesized bearing a glucose substituent to increase the water solubility of the ligand

Full text of DOI:10.1016/j.jorganchem.2008.12.063

Journal of Organometallic Chemistry 694 (2009) 1736–1746
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and screening of bifunctional radiolabelled
carborane-carbohydrate derivatives
*
Andrew E.C. Green, Shannon K. Parker, John F. Valliant
Departments of Chemistry and Medical Physics and Applied Radiation Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4M1
a r t i c l e i n f o
a b s t r a c t
Article history:
A new bifunctional carborane ligand was prepared as a platform for the development of targeted molec-
ular radioimaging and therapy agents. The carborane derivative was synthesized bearing a glucose sub-
stituent to increase the water solubility of the ligand and a benzoic acid group as a site for linking to
amine containing targeting vectors. A convenient method to conjugate the ligand and the non-glycosyl-
ated analogue to amino groups was developed using simple active esters which were combined with a
model amine generating two new N,N-diethyl(aminoethyl) benzamide derivatives. These were labelled
with 125I in good yield and the logP values measured for [125I]-15 (logP = 0.82 0.04) and [125I]-16
(logP = 1.53 0.01). The benzamides were also evaluated for their capacity to bind to B16F10 melanoma
cells where the hydrophilic compound showed low binding while [125I]-16 showed modest uptake
(30.7 2.2%) after 24 h.
Received 9 November 2008
Accepted 15 December 2008
Available online 6 January 2009
Keywords:
Carboranes
Molecular imaging
Radioiodine
Benzamides
Melanoma
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
One of the limitations associated with carborane-based radio-
pharmaceuticals is that they are generally lipophilic which can
Targeted radiopharmaceuticals are typically engineered such
that they contain two key components: a vector for achieving high
target-to-non-target ratios and a ligand or prosthetic group to en-
sure that there is a robust covalent linkage between the targeting
moiety and the radionuclide. Radiolabelled carboranes are attrac-
tive synthons in this regard because they can be readily conjugated
to, or incorporated within, targeting vectors using a number of cre-
ative strategies and they are conveniently prepared from virtually
any suitably protected alkyne [1–7]. 7,8-Dicarba-nido-undecab-
orate(-1) or nido-carborane ligands, which can be prepared from
the corresponding closo-carboranes [1,8–12], have a unique feature
in that they can be labelled with both radiometals, including tech-
netium, which is the most widely used radionuclide in diagnostic
medicine [13,14] and radiohalogens. Nido-carboranes form highly
promote non-specific binding. In this paper, we present the syn-
thesis and characterization of a bifunctional carborane-glucose
derivative where the hydrophilic nature of the carbohydrate is de-
signed to mask the non-polar carborane group. Several examples
for other classes of imaging agents have been reported in which
the addition of a carbohydrate reduces non-specific binding and
enhances pharmacokinetics (faster clearance from non-target tis-
sues) versus the underivatized counterparts [36–43].
2. Results and discussion
We recently described the preparation and labelling of simple
carboranyl glycoside derivatives of glucose with both Tc and iodine
[44,45]. Building on the success of the model system, a nido-carb-
oranyl glycoside 1 that contains a benzoic acid group for conjuga-
tion to targeting vectors such as peptides, proteins, or antibodies
was developed (Fig. 1). A non-glycosylated analogue (2) was pre-
pared in parallel so that the impact of the sugar on the overall
polarity of the compounds (i.e. logP) could be determined.
stable
g
5-complexes with metals [15–19] and they can be labelled
with halogens using electrophilic methods analogous to those cur-
rently used to prepare traditional radiopharmaceuticals [20–22].
Iodinated nido-carborane derivatives are attractive platforms for
developing molecular imaging probes because the B–I bond
formed is more robust than aryl C–I bonds, [22–24] thereby cur-
tailing de-iodination in vivo. Not surprisingly, there has been an in-
crease in the number of groups developing targeted
radiopharmaceuticals using radiohalogenated nido-carboranes
[21,22,24–35].
2.1. Preparation of nido-carborane precursors
Compound 1 was prepared in three steps in good overall yield
from the known alkyne 3 [46,47]. A Sonogashira type cross-cou-
pling reaction [48] between 3 and methyl 4-iodo-benzoate [49]
was used to incorporate the benzoic acid group which would later
serve as the location for conjugation to targeting vectors [50–52].
* Corresponding author. Fax: +1 905 522 2509.
E-mail address: valliant@mcmaster.ca (J.F. Valliant).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.12.063

A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
1737
agents would not only be useful imaging agents but they would
also be attractive compounds for targeted radionuclide therapy
which requires robust complexes and high target-to-non-target ra-
tios in order to minimize the radiation dose to healthy tissue (see
Scheme 1).
-
OH
-
H
H
O
OH
OH
O
C
C
C
C
H
OH
H
O
O
The non-glycosylated nido-carboranyl benzamide 7 was pre-
pared from the benzoic acid derivative 2 (Scheme 2) using a conve-
nient active ester coupling strategy. The 2,3,5,6-tetrafluorophenyl
active ester 6 was obtained via DIC coupling and isolated by pre-
parative TLC. The benzamide target 7 was then prepared by com-
bining 6 with N,N-diethylethylenediamine in acetonitrile at room
temperature for 12 h; purification by preparative TLC gave the tar-
get in 26% yield.
An alternative route was established to prepare the glycosyl-
ated target 8 because the polar nature of the compounds compli-
cated the isolation of large quantities of the active ester
precursor. To address this issue, the protecting groups were altered
such that a benzyl ester was used in place of the methyl ester
(Scheme 3). This made it possible to liberate the acid without
removing the acetate protecting groups on the carbohydrate,
thereby making it simpler to purify the active ester and benzamide.
Each step in the synthesis had yields greater than 50% with the
exception of the final step which was 35%. This still represents
an improvement over the yield obtained when trying to prepare
the target directly from nido-carboranyl glycoside 1.
1
2
OH
OH
Fig. 1. Functionalized nido-carborane derivatives 1 and 2.
The corresponding carborane was then prepared using a standard
decaborane-alkyne insertion reaction. Simultaneous carborane
cage degradation and ester saponification was achieved using so-
dium hydroxide in methanol which, following work-up, gave 1 in
29% overall yield. The non-glycosylated nido-carborane-benzoic
acid precursor 2 was prepared via a similar route starting with
methyl 4-[1,2-dicarba-closo-dodecaboranyl] benzoate in excellent
yield.
2.2. Preparation of model conjugates
The optimal method for linking 1 and 2 to targeting amines was
investigated using a simple alkylamine (N,N-diethylethylenedi-
amine). This amine was selected to not only probe the reactivity
of the benzoic acid group but to also produce two novel benzam-
ides for use in targeting melanoma. There is a wealth of data in
the literature indicating that N,N-dialkyl(aminoalkyl) benzamides
have high uptake in melanin positive tumour types [22,53–75].
Moreover, Hawthorne and co-workers have demonstrated the
in vivo stability and rapid clearance in biodistribution studies of
radioiodinated benzamides derived from nido-carboranes [22].
The attractive feature of the target carborane-benzamides pro-
posed here over conventional agents containing aryl halides is that
the strength of the boron-iodine bond should prevent the prema-
ture catabolism while the carbohydrate group should decrease
non-specific binding and promote clearance from non-target tis-
sues. If these hypotheses are in fact valid, then the carborane-based
2.3. Syntheses of iodinated nido-carborane standards
The next step was to isolate the non-radioactive iodinated
derivatives 14–16 (Scheme 4), for which small quantities are
needed as reference standards for the radiolabelled analogues
[20]. A sample of 14 was prepared by treating precursor 1 with I2
in ethanol. Analysis by HPLC and electrospray mass spectrometry
indicated complete consumption of the starting material after 2 h
at room temperature, as evidenced by the absence of the HPLC
and MS signals corresponding to 1. The HPLC chromatogram of
the isolated product contained four peaks (Fig. 2, top), with each
peak showing the target anion mass of m/z = 572 for 14 in the
OAc
OAc
O
O
AcO
AcO
AcO
O
O
a
O
O
AcO
OAc
I
H
+
OAc
H
O
CH3
H
O
CH3
4
3
-
OH
O
OAc
O
H
C
O
H
AcO
AcO
b
c
C
O
C
C
O
O
H
OH
OAc
OH
O
CH3
H
H
O
O
5
1
Scheme 1. Reagents and conditions: (a) 5 mol% (Ph3P)4Pd, 5 mol% CuI, 1:1 THF:NEt3, reflux, 12 h; (b) B10H14 (2.0 equiv.), CH3CN, reflux, 48 h; (c) (i) NaOH (20 equiv.), MeOH,
60 °C, 12 h; (ii) NaOH(aq), 3 h; (iii) 1 M HCl, pH 4.
-
H
C
H
C
-
-
H
C
C
C
F
F
F
F
H
H
C
b
H
N
a
H
OH
O
O
O
N
O
7
2
6
Scheme 2. Reagents and conditions: (a) TFP, DIC, 12 h, CH3CN; (b) N,N-diethylethylenediamine, 12 h, CH3CN.

1738
A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
OAc
OAc
O
O
AcO
AcO
AcO
O
O
a
O
O
AcO
I
H
+
C
OAc
OAc
H
OBn
H
OBn
9
3
OAc
OAc
O
AcO
O
AcO
AcO
C
O
b
c
C
C
O
AcO
OAc
OAc
OBn
OH
H
H
O
11
O
10
OAc
OAc
O
AcO
O
C
C
AcO
AcO
O
d
C
C
O
AcO
e
OAc
H
N
OTFP
OAc
H
H
O
12
O
N
13
Na+
C
1-
-
OH
H
C
f
O
O
H
O
O
H
H
OH
N
H
O
N
8
Scheme 3. Reagents and conditions: (a) 5 mol% (Ph3P)4Pd, 5 mol% CuI, 1:1 v:v THF:NEt3, reflux, 12 h; (b) B10H14, CH3CN, reflux, 48 h; (c) H2 (1 atm), 10% Pd/C, EtOH, 1 h; (d)
2,3,5,6-tetrafluorophenol, EDC ꢁ HCl, CH3CN, 2 h; (e) N,N-diethylethylenediamine, CH3CN, 12 h; (f) NaOH, EtOH, 60 °C, 12 h.
H
I2, RT, 2hr
H
-
-
I
EtOH or
C
C
C
C
R1
R1
1:1 H2O: CH3CN
O
O
+ Isomer(s)
R2
R2
14: R1 = CH2-β-D-glucose, R2 = OH
15: R1 = CH2-β-D-glucose, R2 = NH(CH2)2N(C2H5)2
16: R1 = H, R2 = NH(CH2)2N(C2H5)2
1: R1 = CH2-β-D-glucose, R2 = OH
7: R1 = H, R2 = NH(CH2)2N(C2H5)2
8: R1 = CH2-β-D-glucose, R2 = NH(CH2)2N(C2H5)2
Scheme 4. Synthesis of iodo-nido-carborane derivatives 14–16.
LC/MS spectrum. The 11B{1H} NMR spectrum of 14 was consistent
with the presence of the iodinated carborane cage, with the signal
appearing at ꢀ29.3 ppm [25,76].
in the event that one isomer has higher affinity for the target or
preferable pharmacokinetic properties, the nido-carborane diaste-
reomers can be separated prior to labelling and HPLC purification.
In the case of compound 14, which is intended for use as a pros-
thetic group for linking to a larger targeting vector such as a pep-
tide or antibody, we would expect that the presence of multiple
isomers at the carborane cage would not influence the affinity of
the larger component since it would be located distant to the bind-
ing domain of the agent.
The appearance of four HPLC peaks corresponding to 14 is con-
sistent with the generation of isomers as a result of the iodine
reacting with the two boron atoms adjacent to the two carbon
atoms on the open face of the nido-carborane cage [24,31]. The
other two products are formed because the nido-carborane exists
as a pair of diastereomers. Degradation of mono-substituted clos-
o-carboranes results in the formation of enantiomers, and in the
case of the carbohydrate derivatives which have fixed stereochem-
istry, the products are diastereomers [3,77]. As a result, iodination
of 1 should result in a total of four species for 14. Further spectro-
scopic evidence for this was obtained by the observation of, for
example, four distinct anomeric proton signals in the 1H NMR
spectrum, and four distinct anomeric carbon signals in the 13C
NMR spectrum of 14.
2.4. Radiolabelling with 125I
The radiolabelling of compounds 1, 7, and 8 was undertaken fol-
lowing methods previously established for radioiodination of the
simple carboranyl glycoside derivative [45]. Compound [125I]-14
was prepared and isolated via HPLC in 50% radiochemical yield.
The radiochromatogram for [125I]-14 displayed a series of four
peaks correlating with the non-radioactive standard 14. The rela-
tive intensities of these peaks were consistent with those of the
standard (Fig. 2). The slight discrepancy observed may be due to
different rates of formation of the various isomers of 14 at the tra-
cer level.
The iodinated-nido-carboranyl benzamides 15 and 16 were pre-
pared in a manner analogous to that described for 14. Electrospray
mass spectrometry was consistent with exclusive mono-iodin-
ation. In the case of both benzamides, multiple HPLC peaks were
again observed having the expected target mass, indicating a mix-
ture of four and two isomers for compounds 15 and 16, respec-
tively. The formation of multiple isomers is not desirable
however the peaks can be readily separated by HPLC. Furthermore,
The syntheses of benzamides [125I]-15 and [125I]-16 were ini-
tially explored by using conditions similar to those described
above for 1. For initial experiments, the non-glycosylated precursor

A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
1739
Fig. 2. HPLC analysis for 125I radiolabelling of 1. Top: UV trace of non-radioactive standard 14. Bottom: -HPLC trace of [125I]-14.
c
7 was reacted with Na[125I] in the presence of IodogenÒ in a 1:1
mixture of acetonitrile and water containing 5% acetic acid; the or-
ganic solvent was required to dissolve the starting materials which
were not soluble in water alone. This initial radiolabelling reaction
gave unexpected results, with no radioactive peak observed
corresponding to the target. Following this, a non-radioactive
experiment was also performed with ‘‘cold” sodium iodide under
the same conditions. Analysis of the product mixture by HPLC
and LC/MS revealed the N-dealkylation of the iodinated nido-carb-
oranyl benzamide. Degradation of tertiary amines has been re-
ported to occur in the presence of strong oxidants under acidic
conditions [78]. Further non-radioactive experiments were con-
ducted which showed that the extent of degradation was reduced
when chloramine-T was used as the oxidant. Therefore, this oxi-
dant was used in subsequent preparations involving the benzam-
ide derivatives.
16 remaining intact after 24 h, and >99% of [125I]-15 remaining in-
tact after 72 h.
With the synthesis and isolation of benzamides [125I]-15 and
[
125I]-16 accomplished, the measurement of their logP values
was undertaken to assess the impact of the carbohydrate substi-
tuent [79]. Following isolation, the solutions containing the
products were evaporated by a stream of air and phosphate-buf-
fered saline (pH 7.4) added. As was observed by Wilbur and co-
workers, the radioiodinated nido-carborane derivatives had a
tendency to adhere to glass vessels. In the case of compounds
[
125I]-15 and [125I]-16, the products adhered to both plastic
and glass vessels which could be minimized by silanization of
glass vials with SigmacoteTM (Aldrich). The logP calculated for
compounds
[
125I]-15 and
[
125I]-16 were 0.82 0.04 and
1.53 0.01, respectively. These results confirm that the addition
of the glucose group had a significant impact on the polarity
of the compound. The difference of 0.71 log units is in reason-
able agreement with differences observed for glycopeptides re-
Using chloramine-T (20
lL of a 1 mg/mL solution in water) as
the oxidant, the -HPLC traces showed two peaks that had reten-
c
tion times that corresponded to those for the non-radioactive stan-
dards. Incorporation of activity at the desired target was estimated
to be >95% from peak integration of the crude analytical traces.
Compound [125I]-16 was obtained in 73% radiochemical yield fol-
lowing isolation by semi-preparative HPLC. The glycoside [125I]-
15 was prepared in the same manner and isolated in 92% yield.
HPLC analysis of the isolated products (Figs. 3 and 4) showed that
they were obtained in >99% radiochemical purity, and that their
respective precursors had been removed. For the purposes of rapid
isolation, it was also possible to use solid phase extraction by
employing C18 SepPakTM cartridges. Although the tracers could be
obtained in excellent radiochemical purity (>99%) using this meth-
od, the specific activity was low, as the SPE method did not sepa-
rate the radioiodinated benzamides from their non-radioactive
precursors. This is not a major issue for the subsequent cell binding
studies since the extent of benzamide binding to melanin has been
reported to be independent of specific activity [72]. The radioiodin-
ated compounds also showed excellent stability, with 98% of [125I]-
ported by Haubner and co-workers [37], who noted
difference of approximately 0.5 log units between short peptide
sequences and their glycosylated analogues.
The binding of benzamides 7 and 8 to B16F10 mouse melanoma
cells was also evaluated. For control purposes, [125I]BZA, which has
been shown previously to have high affinity to this particular cell
line [53,72], was prepared and its uptake evaluated in parallel.
The results showed that the glycosylated benzamide [125I]-15
a
bound poorly to the cells with
a maximum binding being
0.62 0.11% of the incubated activity after 24 h (Fig. 5). Mean-
while, [125I]-16 showed improved uptake (30.7 2.2% at 24 h)
which was less than that for [125I]BZA (91.6 0.3% at 24 h). These
results suggest that the increased hydrophilicity of the carbohy-
drate conjugate resulted in reduced uptake by the melanoma cells
and that perhaps the negative charge on the carborane also had a
detrimental impact on binding. This is in agreement with the gen-
eral observation that uptake of radioiodobenzamides by melanotic
melanoma increases with increasing lipophilicity [55].

1740
A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
Fig. 3. HPLC analysis for 125I-radiolabelling of 8. Top:
c
-HPLC trace of [125I]-15. Bottom: UV trace of non-radioactive standard 15.
Fig. 4. HPLC analysis for 125I radiolabelling of 7. Top: UV trace of non-radioactive standard 16. Bottom: -HPLC trace of [125I]-16.
c

A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
1741
and 1% antibiotic/antimycotic (AB/AM) (15240-062; Invitrogen,
Burlington, ON). All cells were maintained at 37 °C in 5% CO2.
3.3. Methyl 40-(2-propynyl-200,300,400,600-tetra-O-acetyl-b-
glucopyranosyloxy)-3-benzoate (4)
D-
Methyl 4-iodo-benzoate (2.53 g, 9.6 mmol) was placed in a 2-
neck round-bottom flask (equipped with a condenser and mag-
netic stir bar) under an atmosphere of nitrogen, and dissolved in
dry THF (50 mL). To this was added Pd(PPh3)4 (560 mg, 0.5 mmol),
CuI (111 mg, 0.6 mmol) and triethylamine (50 mL). A solution of
compound 3 (3.42 g, 8.8 mmol) in dry THF (40 mL) was added
dropwise to the reaction vessel. The reaction mixture was stirred
at reflux for 12 h, during which time the solution changed from
colourless, to light yellow, to dark brown with a white suspended
solid. The solution was filtered through a pad of Celite, concen-
trated on a rotary evaporator and subsequently re-dissolved in
100 mL of dichloromethane and placed in a separatory funnel.
The organic solution was shaken twice with 250 mL of 0.1 M HCl,
followed by 250 mL of brine. The organic layer was then dried over
anhydrous Na2SO4, filtered, and concentrated to a dark orange-
brown oil on the rotary evaporator. Silica gel column chromatogra-
phy (10–50% ethyl acetate/hexanes) was used to isolate the target
compound as an orange oil that was dissolved in a mixture of
diethyl ethyl acetate and hexanes to crystallize the desired prod-
Fig. 5. Binding of [125I]BZA, [125I]-15 and [125I]-16 to B16F10 melanoma cells as a
function of time.
3. Experimental
3.1. Materials and instruments
All reagents used were purchased from Aldrich, except for dec-
aborane [14], which was purchased from Katchem (Czech Rep.).
Solvents were purchased from Caledon and dried using a PureSolv
drying apparatus (Innovative Technology). No-carrier-added 125I
was obtained from the McMaster Nuclear Reactor as Na[125I] in
0.1 N NaOH. NMR spectroscopy was performed on either a Bruker
uct. The target compound was obtained in 64% yield (2.93 g). 1H
NMR (500 MHz, CDCl3): d 8.00 (d, 2H, J2 ;3 ¼ 8:3 Hz, H-20), 7.50
3
0
0
3
3
(d, 2H, H-30), 5.27 (dd, 1H, J2,3 = 9.4 Hz, J3,4 = 9.4 Hz, H-3), 5.12
3
3
(t, 1H, J4,5 = 10.0 Hz, H-4), 5.04 (dd, 1H, J1,2 = 8.0 Hz, H-2), 4.84
DRX-500
(1H
frequency = 500.13 MHz,
or Avance AV-600
13C = 125.77 MHz,
(1H = 600.13 MHz,
2
(d, 1H, H-1), 4.61 (s, 2H, H-7), 4.29 (dd, 1H, J6a,6b = ꢀ12.3 Hz,
11B = 160.46 MHz)
3J5,6a = 4.6 Hz, H-6a), 4.17 (dd, 1H, J5,6b = 2.3 Hz, H-6b), 3.93 (s,
3
13C = 150.90 MHz, 11B = 192.55 MHz) spectrometer. Proton and
carbon assignments were made with the assistance of COSY,
HSQC and HMBC spectra. The residual signal of the NMR solvent
relative to tetramethylsilane was taken as the internal reference
for 1H and 13C spectra. 11B spectra were referenced using a
BF3 ꢁ Et2O external standard. The numbering scheme used for
NMR assignments can be found in Supplementary material. Infra-
red spectra were recorded on a BioRad FTS-40 FT-IR instrument.
Mass spectra were obtained using a Micromass Quattro-LC Triple
Quadrupole mass spectrometer. Radioactivity measurements were
made using either a Capintec CRC-15W dose calibrator or a Per-
kin–Elmer Wizard gamma counter. High-performance liquid chro-
matography was performed with a Varian ProStar HPLC system
3H, H-11), 3.77 (ddd, 1H, H-5), 2.08, 2.04, 2.03, 2.01 (4s, 12H,
CH3). 13C NMR (125 MHz, CDCl3): d 170.5, 170.2, 169.3, 166.3,
131.6, 130.1, 129.5, 126.8, 98.5, 86.4, 86.3, 72.8, 72.0, 71.2, 68.4,
61.8, 56.7, 52.2, 20.6, 20.5. IR (KBr):
m
1758, 1722 cmꢀ1. ESI-MS:
m/z = 538.6 [M+NH4]+. HRMS (ESI): Calculated for C25H28O12NH4:
538.1925. Observed: 538.1915. M.P.: 80–83 °C. TLC (2:1 hex-
anes:ethyl acetate): Rf = 0.24.
3.4. Methyl 40-(1-methyl-(200,300,400,600-tetra-O-acetyl-b-
D-
glucopyranosyloxy)-1,2-dicarba-closo-dodecaboranyl)-2-benzoate (5)
B10H14 (1.35 g, 11.0 mmol) was dried under vacuum for 2 h in a
flame-dried round-bottom flask. Under nitrogen, dry acetonitrile
(50 mL) was added via syringe through a septum, and the resulting
solution stirred at room temperature for 12 h. Compound 4 (2.57 g,
4.94 mmol) was added, and the solution heated to reflux and stir-
red for a further 48 h. The solution was cooled to room tempera-
fitted with an IN/US
c-RAM Model 3 detector. For analysis of
compounds, either a Varian Nucleosil 4.6 ꢂ 250 mm C18 or Phe-
nomenex Gemini 4.6 ꢂ 100 mm C18 column was used. For
semi-preparative HPLC, a Varian Dynamax 10 ꢂ 250 mm C18 col-
umn was used. Elution conditions: Method A: 80:20 A:B to 20:80
A:B; 0–20 min, 20:80 A:B to 100% B; 20–25 min, 100% B; 25–
30 min (A = H2O containing 0.05% TFA, B = CH3CN containing
0.05% TFA), Nucleosil column; Method B: 80:20 A:B to 20:80
A:B; 0–20 min, 20:80 A:B to 100% B; 20–25 min, 100% B; 25–
30 min (A = H2O containing 0.05% TFA, B = CH3CN containing
0.05% TFA), Gemini column. Analytical flow rate was 1.0 mL/
min; semi-preparative flow rate was 4.7 mL/min. Thin-layer chro-
matograms (Merck F254 silica gel on aluminum plates) were visu-
alized using 0.1% PdCl2 in 3 M HCl.
ture and concentrated on
a rotary evaporator, yielding an
orange-brown oil. Column chromatography (10–50% ethyl ace-
tate/hexanes) resulted in the isolation of a slightly yellow solid
which was re-crystallized from ethyl ether and hexanes to give
the desired compound as a white solid in 60% yield (1.89 g). 1H
NMR (500 MHz, CDCl3): d 8.03 (d, 2H, J2 ;3 ¼ 8:5 Hz, H-30), 7.70
3
0
0
3
3
(d, 2H, H-20), 5.13 (t, 1H, J2,3 = 9.5 Hz, J3,4 = 9.5 Hz, H-3), 4.99 (t,
3
3
1H, J4,5 = 9.9 Hz, H-4), 4.95 (dd, 1H, J1,2 = 7.8 Hz, H-2), 4.31 (d,
2
3
1H, H-1), 4.11 (dd, 1H, J6a,6b = ꢀ12.4 Hz, J5,6a = 4.7 Hz, H-6a),
3
3.95 (dd, 1H, J5,6b = 2.3 Hz, H-6b), 3.94 (s, 3H, OCH3 H-11), 3.83
2
(d, 1H, J7a,7b = ꢀ12.6 Hz, H-7a), 3.69 (d, 1H, H-7b), 3.52 (ddd, 1H,
3.2. Cell culture
H-5), 2.12, 2.03, 2.01, 1.99 (4s, 12H, CH3) 1.70–3.20 (br m, B-H).
13C NMR (125 MHz, CDCl3): d 170.3, 170.1, 169.2, 169.0, 165.7,
134.3, 132.4, 131.2, 129.9, 100.2, 81.3, 79.4, 72.3, 72.0, 70.7, 68.1,
67.9, 61.5, 52.5, 20.6, 20.5. 11B{1H} NMR (160 MHz, CDCl3): d
The murine B16F10 melanoma cell line was purchased from
ATCC (Manassas, VA) and maintained in monolayer in DMEM
(11995; Gibco, Burlington, ON, Canada) supplemented with 10% fe-
tal bovine serum (SH30071.03; Hyclone Laboratories, Logan, UT)
ꢀ3.7, ꢀ11.0. IR (KBr):
m
2587, 1758, 1730 cmꢀ1. ESI-MS: m/
z = 657.8 [M+NH4]+. HRMS (ESI): Calculated for C25H38B10O12NH4:

1742
A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
657.3696. Observed: 657.3715. TLC (2:1 hexanes:ethyl acetate):
Rf = 0.27. M.P.: 167–170 °C.
1606. TLC (1:9 CH3OH:CH2Cl2 + 0.1% CH3COOH): Rf = 0.15. HPLC:
tR = 17.4 min (Method A). ESI-MS: m/z = 254.0 [M]ꢀ. HRMS (ESI)
Calculated for C9H16B9O2: 254.2031. Observed: 254.2025.
3.5. 40-(Sodium[7-methyl-b-
D-glucopyranosyloxy-7,8-dicarba-nido-
undecaboranyl])-8-benzoic acid (1)
3.7. 200,300,500,600-Tetrafluorophenyl-40-(sodium[7,8-dicarba-nido-
undecaboranyl])-7-benzoate (6)
Compound 5 (1.57 g, 2.5 mmol) and NaOH (1.03 g, 26 mmol)
were dissolved in methanol (40 mL), and stirred with mild heating
(ꢃ50 °C) for approximately 12 h. The methanol was removed by
rotary evaporation, and the resulting white solid re-dissolved in
10 mL of distilled water, to which was added 2.5 mL of 1.0 M NaOH
(2.5 mmol). The resulting solution was stirred at room temperature
for 3 h whereupon the pH was adjusted to 4 using 1 M HCl. The
solution was dried by rotary evaporation, yielding a white solid
which was dissolved in a minimum amount of methanol and
cooled in a freezer for 2 h. The resulting precipitate was removed
on a pad of Celite on top of a fine glass frit. The filtrate was subse-
quently concentrated by rotary evaporation to give an off-white
solid. This crude product was purified using silica gel column chro-
matography (1:4 MeOH:CH2Cl2 to 2:3 MeOH:CH2Cl2). The fractions
containing the desired product were concentrated by rotary evap-
oration, re-dissolved in a minimum quantity of methanol, and al-
lowed to stand in a freezer overnight. The resulting precipitate
was removed as described above. The solvent was removed by ro-
tary evaporation yielding the desired product as a white solid
Compound 2 (0.1138 g, 0.41 mmol) and 2,3,5,6-tetrafluorophe-
nol (0.15 g, 0.90 mmol) were dissolved in 1 mL of dry acetonitrile.
To this solution was added diisopropylcarbodiimide (100 lL,
0.65 mmol), and the reaction stirred overnight at room tempera-
ture during which time a white precipitate formed. The precipitate
was removed by filtration, and the filtrate solution concentrated by
rotary evaporation. The target compound was isolated by prepara-
tive TLC (15% CH3OH/CH2Cl2), and used without further purifica-
tion. 11B{1H} NMR (160 MHz, acetone): d ꢀ7.4, ꢀ9.2, ꢀ12.6,
ꢀ15.4, ꢀ17.0, ꢀ19.0, ꢀ22.2, ꢀ31.8, ꢀ34.6. ESI-MS: m/z = 402.1
[M]ꢀ. HRMS (ESI): Calculated for C15H16B9O2F4: 402.1971. Ob-
served: 402.1985.
3.8. N,N-Diethyl(aminoethyl)-40-(sodium[7,8-dicarba-nido-
undecaboranyl])-7-benzamide (7)
N,N-Diethylethylenediamine (45.5 lL, 0.32 mmol) was added to
compound 6 (0.13 g, 0.30 mmol) in 1 mL dry acetonitrile. After stir-
ring overnight the desired product was isolated via preparative TLC
(20% CH3OH/CH2Cl2 + 1%NEt3) using acetone to extract the product
from the plate (0.03 g, 26%). 1H NMR (500 MHz, acetone-d6): d 8.25
(0.88 g, 76%). The signals attributed to the second isomer are de-
noted with
0ꢄ;30ꢄ
.
1H NMR (600 MHz, CD3OD):
d
7.76 (d, 2H,
*
3J2
¼ 8:4 Hz, H-20*), 7.74 (d, 2H, J2 ;3 ¼ 8:4 Hz, H-20), 7.43 (d,
3
0
0
3
3
2H, H-30*), 7.38 (d, 2H, H-30), 3.95 (d, 1H, J1,2 = 7.7 Hz), 3.81 (d,
(br, 1H, amide N-H, H-12), 7.64 (d, 2H, J2,3 = 8.5 Hz, H-2), 7.29 (d,
1H, J7aꢄ
ꢄ
¼ ꢀ10:9 Hz, H-7a*), 3.71 (dd, 1H, J6aꢄ
¼ ꢀ12:1 Hz,
2H, H-3), 3.78 (m, 2H, 3J8,9 = 5.4 Hz, H-8), 3.39 (m, 2H, H-9), 3.31 (q,
4H, 3J10,11 = 7.2 Hz, H-10), 2.27 (br s, H-6), 1.33 (t, 6H, H-11), ꢀ0.30
to ꢀ2.80 (br, B-H). 13C NMR (125 MHz, acetone-d6): d 170.5, 152.3,
129.9, 127.3, 127.1, 62.3, 55.4, 49.0, 44.9, 37.8, 10.2. 11B{1H} NMR
(160 MHz, acetone-d6): d ꢀ7.7, ꢀ9.4, ꢀ12.8, ꢀ15.7, ꢀ17.0, ꢀ19.0,
2
2
ꢄ
ꢄ
;7b
;6b
3J5
¼ 2:4 Hz, H-6a*), 3.66 (dd, 1H, 2J6a,6b = ꢀ11.9 Hz,
;6aꢄ
3J5,6a = 2.5 Hz, H-6a), 3.60 (dd, 1H, 3J5
¼ 5:1 Hz, H-6b*), 3.52
ꢄ
2
ꢄ;6b
*
(m, 3H, H-1 , H-7a, H-6b), 3.44 (d, 1H, J7a,7b = ꢀ11.1 Hz, H-7b),
3.24 (m, 4H, H-3,3*,4,4*), 3.18 (dd, 3J1
¼ 7:7 Hz, H-2*), 3.10 (dd,
ꢄ;2ꢄ
3
3
1H, H-2), 3.02 (ddd, J4,5 = 9.3 Hz, J5,6b = 5.4 Hz, H-5), 2.94 (ddd,
1H, H-5*), 2.92 (d, 1H, H-7b*), 2.50 to ꢀ0.30 (br m, 18H, B-H),
ꢀ2.20 (br s, 2H, B-H-B). 13C NMR (151 MHz, CD3OD): d 179.0,
174.2, 147.1, 147.0, 133.5, 132.7, 132.6, 129.2, 129.0, 103.9,
103.5, 77.7, 77.5, 77.4, 75.7, 75.3, 75.0, 74.8, 71.5, 71.5, 66.6,
66.1, 63.3, 62.9, 62.5, 62.3. 11B{1H} NMR (192 MHz, CD3OD): d
ꢀ22.1, ꢀ31.9, ꢀ34.9. IR (KBr pellet):
m 3407, 2527, 1640. TLC
(20% CH3OH/CH2Cl2 + 1%NEt3): Rf = 0.50. HPLC: tR = 13.3 min
(Method B). ESI-MS: m/z = 352.4 [M]ꢀ. HRMS (ESI) Calculated for
C15H30B9ON2: 352.3242. Observed: 352.3251.
3.9. Benzyl 40-(2-propynyl-200,300,400,600-tetra-O-acetyl-b-
glucopyranosyloxy)-3-benzoate (9)
D-
ꢀ8.3, ꢀ10.0, ꢀ14.0, ꢀ16.8, ꢀ33.1, ꢀ36.6. IR (KBr):
m 3433, 2530,
1592 cmꢀ1. TLC (1:3 CH3OH:CH2Cl2 + 0.1% HOAc): Rf = 0.38. HPLC:
tR = 12.6 min (Method A); 11.5 min, 11.7 min (Method B). ESI-MS:
m/z = 446.4 [M]ꢀ. HRMS (ESI): Calculated for C16H28B9O8:
446.2671. Observed: 446.2681.
2-Propynyl-2,3,4,6-tetra-O-acetyl-b-D-glucopyranoside (2.01 g,
5.20 mmol), benzyl 4-iodobenzoate (1.94 g, 5.73 mmol), tetra-
kis(triphenylphosphine) palladium(0) (0.321 g, 0.28 mmol) and
copper(I) iodide (0.053 g, 0.28 mmol) were combined in a round-
bottom flask and dissolved in 100 mL of a 1:1 solution of dry THF
and freshly distilled triethylamine. The resulting mixture was
heated to reflux and allowed to stir overnight (ꢃ12 h), during
which time a white precipitate was formed, and the solution be-
came amber-brown in colour. The solid was removed by filtration,
and the filtrate concentrated by rotary evaporation giving an am-
ber-brown oil. The crude material was dissolved in chloroform
(50 mL) and extracted three times with 50 mL of 0.01 M HCl, fol-
lowed by washing three times with 50 mL of distilled water. The
organic layer was dried over Na2SO4 before filtering through a
pad of silica gel, washing with 100 mL CHCl3, followed by 300 mL
of ethyl acetate. The filtrate was concentrated by rotary evapora-
tion. The resulting oil was re-dissolved in the minimum amount
of ethyl acetate and the target compound isolated via silica gel col-
umn chromatography (10–40% ethyl acetate/hexanes). The frac-
tions containing the product were concentrated to an amber oil
by rotary evaporation. The desired product was crystallized from
3.6. 40-(Sodium [7,8-dicarba-nido-undecaboranyl]-7-benzoic acid (2)
Methyl 4-[1,2-dicarba-closo-dodecaboranyl] benzoate [80]
(1.10 g, 4.0 mmol) and sodium hydroxide (0.86 g, 21.4 mmol) were
combined in a round-bottom flask, and dissolved in methanol
(75 mL). The flask was heated overnight (approximately 12 h) in
an oil bath at 65 °C. The reaction was cooled to room temperature,
and the solvent removed by rotary evaporation. The solid residue
was re-dissolved in distilled water (10 mL) and the resulting solu-
tion stirred at room temperature for 4 h, whereupon the pH was
adjusted to 3 using 1.0 M HCl (14.6 mL). The solution was diluted
with acetonitrile and concentrated to dryness on a rotary evapora-
tor, giving a white solid. The target compound was isolated via sil-
ica gel column chromatography (5–25% CH3OH/CH2Cl2), giving a
thick, light yellow oil. Yield: 1.02 g (93%). 1H NMR (600 MHz, ace-
3
tone-d6): d 7.78 (d, 2H, J2,3 = 8.1 Hz, H-2), 7.25 (d, 2H, H-3), 2.27
(br s, Ccage-H), ꢀ0.30–2.60 (br m, B-H), ꢀ2.42 (br, B-H-B). 13C
NMR (150 MHz, acetone-d6): d 171.0, 151.9, 129.6, 126.7, 62.2,
45.1. 11B{1H} NMR (192 MHz, acetone): d ꢀ7.9, ꢀ9.5, ꢀ12.9,
the oil using ether/hexanes to give an off-white solid (2.02 g,
65%). 1H NMR (500 MHz, CDCl3): d 8.04 (d, 2H, J2 ;3 ¼ 8:4 Hz, H-
3
0
0
ꢀ15.7, ꢀ17.3, ꢀ19.1, ꢀ22.3, ꢀ32.0, ꢀ34.9. IR (KBr):
m
3576, 2526,
20), 7.49 (d, 2H, H-30), 7.39 (m, 5H, OBn Aryl H), 5.37 (s, 2H,

A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
1743
3
3
OCH2C6H5H-11), 5.26 (t, 1H, J2,3 = 9.5 Hz, J3,4 = 9.8 Hz, H-3), 5.12
61.7, 20.6, 20.5. 11B{1H} NMR (160 MHz, CDCl3): d ꢀ2.8, ꢀ10.4. IR
3
3
(t, 1H, J4,5 = 10.0 Hz, H-4), 5.04 (dd, 1H, J1,2 = 8.0 Hz, H-2), 4.83
(KBr pellet): m 3245, 2593, 1758. TLC (ethyl acetate + 0.1% HOAc):
2
(d, 1H, H-1), 4.61 (s, 2H, H-7), 4.29 (dd, 1H, J6a,6b = ꢀ12.3 Hz,
Rf = 0.85. ESI-MS: m/z = 624.4 [MꢀH]ꢀ. HRMS (ESI): Calculated for
3J5,6a = 4.7 Hz, H-6a), 4.17 (dd, 1H, J5,6b = 2.4 Hz, H-6b), 3.76 (ddd,
C24H35B10O12: 624.3113. Observed: 624.3114.
3
1H, H-5), 2.08, 2.04, 2.02, 2.01 (s, 12H, CH3). 13C NMR (125 MHz,
CDCl3) d 170.6, 170.2, 169.4, 165.7, 135.8, 131.6, 130.1, 129.7,
128.6, 128.4, 128.2, 126.9, 98.5, 86.5, 86.3, 72.8, 72.0, 71.2, 68.4,
3.12. 2000,3000,5000,6000-Tetrafluorophenyl-40-(1,2-dicarba-closo-
dodecaboranyl-1-methyl-200,300,400,600-tetra-O-acetyl-b-
glucopyranosyl)-2-benzoate (12)
D-
67.0, 61.8, 56.8, 20.7, 20.6. IR (KBr pellet):
m
1757, 1725. TLC (1:2
ethyl
acetate:hexanes):
Rf = 0.19.
ESI-MS: m/z = 655.3
[M+CH3COO]ꢀ. HRMS (ESI): Calculated for C31H32O12 + CH3COO:
655.2027. Observed: 655.2026.
Compound 11 (0.22 g, 0.35 mmol) and tetrafluorophenol
(0.12 g, 0.75 mmol) were dissolved in 2 mL dry acetonitrile, fol-
lowed by EDC ꢁ HCl (0.082 g, 0.43 mmol). The reaction was allowed
to stir at room temperature for 2 h until TLC indicated consump-
tion of starting material. The solution was concentrated to dryness,
then re-dissolved in 4 mL CH2Cl2 and added to a separatory funnel.
The dichloromethane solution was extracted three times with
0.01 M HCl (4 mL), and washed three times with distilled water
(4 mL). The organic layer was dried over anhydrous Na2SO4, fil-
tered, and concentrated to a light yellow oil by rotary evaporation.
The oil was re-dissolved in a minimum volume of ether, cooled in
an ice bath and hexanes added to induce crystallization, yielding a
3.10. Benzyl 40-(1-methyl-200,300,400,600-tetra-O-acetyl-b-
D-
glucopyranosyl-1,2-dicarba-closo-dodecaboranyl)-2-benzoate (10)
B10H14 (0.49 g, 4.0 mmol) was dried under vacuum for 2 h prior
to addition of 20 mL dry acetonitrile. The resulting solution was
stirred at room temperature overnight. Alkyne 9 (0.79 g, 1.3 mmol)
was added, and the solution heated to reflux for 48 h, giving a deep
yellow solution from which a precipitate formed on cooling. The
precipitate was removed by gravity filtration, and the filtrate con-
centrated by rotary evaporation, giving a yellow solid which was
dissolved in a minimum quantity of ethyl acetate, and the desired
product isolated silica gel column chromatography (1:2 ethyl ace-
tate:hexanes). The fractions containing the desired product were
concentrated by rotary evaporation, giving a light yellow oil which
crystallized slowly at room temperature. The product was re-crys-
tallized from ethyl acetate and hexanes, giving a white, crystalline
white solid (0.19 g, 70%). 1H NMR (500 MHz, CDCl3): d 8.22 (d, 2H,
3
J2 ;3 ¼ 8:6 Hz, H-20), 7.82 (d, 2H, H-30), 7.07 (m, 1H, TFP H-11), 5.15
0
0
3
3
3
(t, 1H, J2,3 = 9.6 Hz, J3,4 = 9.5 Hz, H-3), 5.01 (t, 1H, J4,5 = 10.0 Hz,
3
H-4), 4.97 (dd, 1H, J1,2 = 7.8 Hz, H-2), 4.36 (d, 1H, H-1), 4.15 (dd,
1H, 2J6a,6b = ꢀ12.4 Hz, 3J5,6a = 4.6 Hz, H-6a), 4.00 (dd, 1H,
3J5,6b = 2.4 Hz, H-6b), 3.86 (d, 1H, J7a,7b = ꢀ12.8 Hz, H-7a), 3.77 (d,
2
1H, H-7b), 3.56 (ddd, 1H, H-5), 2.12, 2.02, 2.01, 2.00 (4 s, 12H,
CH3), 1.70–3.30 (br, B-H). 13C NMR (125 MHz, CDCl3): d 170.3,
170.0, 169.2, 169.0, 161.4, 147.1, 145.1, 141.7, 139.7, 136.0,
131.6, 130.9, 129.6, 129.4, 103.6, 100.3, 80.7, 79.5, 72.3, 72.0,
70.7, 68.1, 68.0, 61.4, 20.6, 20.5, 20.4. 11B{1H} NMR (192 MHz,
solid. (0.48 g, 50%). 1H NMR (500 MHz, CDCl3): d 8.06 (d, 2H,
J2 ;3 ¼ 8:4 Hz, H-20), 7.69 (d, 2H, H-30), 7.39 (m, 5H, OBn aryl H),
3
0
0
3
3
5.38 (s, 2H, H-11), 5.12 (dd, 1H, J2,3 = 9.5 Hz, J3,4 = 9.6 Hz, H-3),
3
3
4.99 (dd, 1H, J4,5 = 10.0 Hz, H-4), 4.95 (dd, 1H, J1,2 = 7.8 Hz, H-2),
2
3
4.31 (d, 1H, H-1), 4.10 (dd, 1H, J6a,6b = ꢀ12.3 Hz, J5,6a = 4.7 Hz,
CDCl3): d ꢀ2.8, ꢀ10.3. IR (KBr pellet):
m 2596, 1758. TLC (1:2 ethyl
3
H-6a), 3.96 (dd, 1H, J5,6b = 2.4 Hz, H-6 b), 3.82 (d, 1H,
acetate:hexanes): Rf = 0.31. ESI-MS: m/z = 885.4 [M+TFA]ꢀ. HRMS
(ESI): Calculated for C30H36B10O12F4 + CF3COO: 886.2982. Ob-
served: 886.2977.
2J7a,7b = ꢀ12.7 Hz, H-7a), 3.69 (d, 1H, H-7 b), 3.52 (ddd, 1H, H-5),
2.10, 2.00, 1.99 (4 s, 12H, CH3), 1.70–3.40 (br, B-H). 13C NMR
(125 MHz, CDCl3): d 170.4, 170.1, 169.2, 165.1, 135.6, 134.4,
132.4, 131.2, 130.0, 128.7, 128.5, 128.3, 100.3, 81.4, 79.4, 72.3,
72.0, 70.7, 68.1, 67.9, 67.2, 61.5, 20.6, 20.5. 11B{1H} NMR
3.13. N,N-Diethyl(aminoethyl)-40-(1,2-dicarba-closo-dodecaboranyl-
1-methyl-200,300,400,600-tetra-O-acetyl-b-
benzamide (13)
D-glucopyranosyl)-2-
(160 MHz, CDCl3): d ꢀ3.0, ꢀ10.3. IR (KBr pellet):
m 2594, 1758,
1726. TLC (1:1 ethyl acetate:hexanes): Rf = 0.67. ESI-MS: m/
z = 714.4 [MꢀH]ꢀ. HRMS (ESI): Calculated for C31H41B10O12
:
Compound 12 (0.25 g, 0.32 mmol) was dissolved in 2.5 mL dry
acetonitrile. To this solution was added 47 L (0.33 mmol) of
714.3586. Observed: 714.3588.
l
3.11. 40-(1-Methyl-200,300,400,600-tetra-O-acetyl-b-
1,2-dicarba-closo-dodecaboranyl)-2-benzoic acid (11)
D-glucopyranosylozy-
N,N-diethylethylenediamine. After stirring overnight, the solvent
was removed by rotary evaporation, and the resulting off-white
foam re-dissolved in a minimum volume of DCM. The target was
isolated via silica gel column chromatography (1:4 acetone:DCM
containing 1% (v/v) triethylamine). The target fractions were com-
bined and concentrated by rotary evaporation yielding a colourless
Compound 10 (0.55 g, 0.77 mmol) was dissolved in 100 mL of
absolute ethanol in a round-bottom flask. To this solution was
added slowly 0.11 g of 10 wt% Pd/C. The flask was purged twice
with hydrogen from a balloon, using a long, stainless steel needle
to bubble the gas through the solution. After 1 h, the product mix-
ture was filtered through pad of Celite and the filtrate concentrated
to dryness by rotary evaporation. The solid residue so obtained was
re-dissolved in DCM and filtered through a plug of glass wool to re-
move the last residue of catalyst, and the solution concentrated to
dryness by rotary evaporation, giving a white solid (0.47 g, 98%). 1H
NMR (500 MHz, CDCl3): d 10.39 (br s, 1H, H-10), 8.09 (d, 2H,
oil which formed a white solid upon drying under vacuum (0.20 g,
86%). 1H NMR (600 MHz, CDCl3): d 7.77 (d, 2H, J2 ;3 ¼ 8:4 Hz, H-
3
0
0
20), 7.68 (d, 2H, H-30), 7.08 (br, 1H, amide N-H, H-15), 5.13 (t, 1H,
3
3
3J2,3 = 9.5 Hz, J3,4 = 9.4 Hz, H-3), 5.01 (t, 1H, J4,5 = 10.0 Hz, H-4),
3
4.96 (dd, 1H, J1,2 = 7.8 Hz, H-2), 4.32 (d, 1H, H-1), 4.13 (dd, 1H,
2J6a,6b = ꢀ12.4 Hz,
3J5,6a = 4.6 Hz,
H-6a),
3.99
(dd,
1H,
3J5,6b = 2.3 Hz, H-6b), 3.83 (d, 1H, J7a,7b = ꢀ12.8 Hz, H-7a), 3.68 (d,
2
3
1H, H-7b), 3.54 (ddd, 1H, H-5), 3.49 (m, 2H, J11,15 = 5.3 Hz, H-
3
3
3
J2 ;3 ¼ 8:4 Hz, H-20), 7.74 (d, 2H, H-30), 5.14 (t, 1H, J2,3 = 9.5 Hz,
3
11), 2.67 (t, 2H, J11,12 = 5.8 Hz, H-12), 2.59 (q, 4H, J13,14 = 7.1 Hz,
H-13), 2.13, 2.03, 2.01, 2.00 (4s, 12H, OAc CH3), 1.05 (t, 6H, H-
14), 1.60–3.10 (br, B-H). 13C NMR (150 MHz, CDCl3): d 170.5,
170.1, 169.3, 169.1, 165.8, 137.1, 132.7, 131.3, 127.4, 100.4, 81.7,
79.5, 72.3, 71.9, 70.7, 68.1, 61.5, 51.1, 46.7, 37.3, 20.7, 20.6, 20.5,
11.9. 11B{1H} NMR (160 MHz, CDCl3): d ꢀ2.0, ꢀ9.4. IR (KBr pellet):
0
0
3J3,4 = 9.7 Hz, H-3), 5.00 (t, 1H, J4,5 = 9.9 Hz, H-4), 4.96 (t, 1H,
3J1,2 = 7.8 Hz, H-2), 4.34 (d, 1H, H-1) 4.11 (dd, 1H, 2J6a,6b = ꢀ12.3 Hz,
3J5,6a = 4.6 Hz, H-6a), 3.95 (dd, 1H, 3J5,6b = 2.4 Hz, H-6b), 3.82 (d, 1H,
2J7a,7b = ꢀ12.6, H-7a), 3.73 (d, 1H, H-7b), 3.54 (ddd, 1H, H-5), 2.12,
2.04, 2.01, 1.99 (4s, 12H, CH3), 1.80–3.30 (br, B-H). 13C NMR
(125 MHz, CDCl3): d 170.7, 170.1, 169.9, 169.3, 169.1, 135.0,
134.8, 131.3, 130.4, 100.1, 81.2, 79.3, 72.3, 71.9, 70.7, 68.1, 67.9,
3
m
3406, 2592, 1758, 1652. TLC (1:2 acetone:CH2Cl2 + 1%NEt3):
Rf = 0.70. ESI-MS: m/z = 724.3 [M+H]+, 782.6 [M+CH3COO]ꢀ. HRMS

1744
A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
(ESI): Calculated for C30H50B10O11N2 + CH3COO: 782.4542. Ob-
served: 782.4537.
75.0, 71.3, 71.7, 71.6, 71.5, 67.6, 62.7, 62.6, 62.5, 62.4, 60.0, 57.5,
56.9. 11B{1H} NMR (192 MHz, CD3OD): d ꢀ4.6, ꢀ14.1, ꢀ24.1,
ꢀ29.3, ꢀ36.4. IR (KBr):
m 3433, 2542, 1607. ESI-MS: m/z = 572.1
3.14. N,N-Diethyl(aminoethyl)-40-(sodium[(7-methyl-b-
D-
[M]ꢀ. HRMS (ESI): Calculated for C16H27B9O8I: 572.1638. Observed:
glucopyranosyl-7,8-dicarba-nido-dodecaboranyl])-8-benzamide (8)
572.1639. HPLC: tR = 12.34, 12.50, 12.84, 13.36 (Method B).
Compound 13 (0.19 g, 0.26 mmol) was dissolved in 5 mL of
3.16. N,N-Diethyl(aminoethyl)-40-(sodium[7-methyl-b-
D-
absolute ethanol. To this solution was added 775
lL (1.6 mmol)
glucopyranosyl-(iodo-7,8-dicarba-nido-undecaboranyl])-8-
of a 80 mg/mL solution of NaOH in 17% H2O/ethanol, and the reac-
tion stirred overnight with heating in an oil bath at 60 °C. The reac-
tion was cooled to room temperature and CO2(g) passed through
the solution to precipitate excess NaOH as Na2CO3. The solid was
removed by filtration, washed with ethanol, and the filtrate con-
centrated to a colourless oil by rotary evaporation. Re-dissolution
in methanol, filtration through a plug of glass wool and rotary
evaporation gave a white solid. The crude material was dissolved
in a minimum volume of methanol and the target compound iso-
lated via silica gel column chromatography (gradient 10–20%
CH3OH:CH2Cl2 containing 1% (v/v) NEt3) in 35% yield (0.052 g).
1H NMR (500 MHz, CD3CN): d 7.89, 7.84 (br, 2H, H-15), 7.65, 7.62
benzamide (15)
Compound 8 (9 mg, 15.9
5:1 mixture (v/v) of ethanol and acetonitrile. To this was added
dropwise 544 L of a 0.03 M solution of I2 (16.1 mol) in ethanol
and the reaction stirred at room temperature for 2 h. A 0.1 M solu-
tion of Na2S2O5 (322 L) was added and the mixture concentrated
to dryness by rotary evaporation, giving a clear, colourless residue
which was re-dissolved in 400 L of a 3:1 (v/v) water:acetonitrile
lmol) was dissolved in 1200 lL of a
l
l
l
l
solution. The mixture was loaded onto a C18 SepPakÒ cartridge
and the desired product isolated following elution with 6 mL
H2O, and 3 mL CH3CN that were collected in 1 mL fractions. The
product was found in the acetonitrile fractions, which were com-
bined and lyophilized giving a white solid (2 mg, 18%). 11B{1H}
NMR (192 MHz, CD3CN): d ꢀ5.0, ꢀ14.0, ꢀ14.2, ꢀ19.0, ꢀ23.9,
ꢀ29.2, ꢀ36.3. ESI-MS: m/z = 670.1 [Mꢀ]. HRMS: Calculated for
C22H41B9O7N2I: 670.2849. Observed: 670.2830. HPLC (Method C):
tR = 10.5 min, 11.0 min.
3
(d, 4H, H-20), 7.53, 7.47 (d, 4H, H-30), 3.94 (d, 1H, J1,2 = 7.7 Hz, H-
2
1), 3.77 (d, 1H, J7a,7b = ꢀ10.9 Hz, H-7a), 3.65 (m, 4H, H-11), 3.61
(dd, 1H, H-6a), 3.54–3.40 (m, 6H, H-1, H-6a, H-6 b, H-7), 3.25–
3.14 (m, 16H, 2H-3, 2H-4, H-12, H-13), 3.07 (m, 1H, H-2), 3.00
(m, 2H, H-2, H-5), 2.94 (m, 1H, H-5), 2.90 (d, 1H, H-7b), 1.26 (t,
3
12H, J13,14 = 7.2 Hz, H-14), ꢀ0.40–2.60 (br, B-H), ꢀ2.20 (br, B-H-
B). 13C NMR (125 MHz, CD3CN) d 171.3, 147.9, 147.7, 133.0,
131.3, 131.2, 127.3, 127.1, 103.1, 102.9, 77.4, 76.9, 76.6, 74.9,
74.8, 74.0, 71.7, 71.3, 67.2, 62.7, 62.6, 61.6, 61.3, 55.4, 49.2, 49.0,
37.4, 37.3, 9.6. 11B{1H} NMR (160 MHz, CD3CN): d ꢀ7.1, ꢀ10.0,
3.17. N,N-Diethyl(aminoethyl)-40-(sodium[iodo-7,8-dicarba-nido-
undecaboranyl])-7-benzamide (16)
ꢀ14.8, ꢀ18.0, ꢀ19.7, ꢀ32.9, ꢀ36.4. IR (KBr pellet):
m
3431, 2526,
Compound 7 (4 mg, 10.7
mixture of water and acetonitrile. To this solution was added
366 L of a 0.0295 M solution of I2 in ethanol (10.8 mol) gradually
lmol) was dissolved in 500 lL of a 1:1
1641. TLC (15% CH3OH/CH2Cl2 + 1%NEt3): Rf = 0.55. HPLC:
tR = 8.87 min (Method C). ESI-MS: m/z = 544.3 [M]ꢀ. HRMS (ESI):
Calculated for C22H42B9O7N2: 544.3879. Observed: 544.3882.
l
l
over 1 h. After all the iodine solution was added, the reaction was
allowed to stir a further hour at room temperature before quench-
3.15. 40-(Sodium[7-methyl-b-
D-glycopyranosyl-(iodo-7,8-dicarba-
ing with 216
lL of 0.1 M Na2S2O5, and concentrating to dryness by
nido-undecaboranyl])-8-benzoic acid (14)
rotary evaporation. The crude material was re-dissolved in 200 lL
of 1:1 water:acetonitrile, which was loaded onto a pre-conditioned
C18 SepPakÒ cartridge. The SPE cartridge was eluted first with
5 mL of H2O, then 5 mL CH3CN, into 10 ꢂ 1 mL fractions where
the desired product was in fractions 7 and 8. These fractions were
combined and concentrated by rotary evaporation and lyophilized
giving a white film (1 mg, 19%). ESI-MS: m/z = 478.1 [M]ꢀ. HRMS
(ESI): Calculated for C15H29B9ON2I: 478.2209. Observed:
478.2208. HPLC: tR = 13.96, 14.30 (Method C).
To a solution of compound 1 (37.5 mg, 80.2
(500 lL) was added 2 mL of I2 in EtOH (82.7 lmol) gradually over
l
mol) in ethanol
1 h. After addition of the iodine solution was complete, the reaction
was stirred at room temperature for a further hour, followed by
addition of 1.7 mL of 0.1 M Na2S2O5 to quench the reaction. The
resulting mixture was concentrated to dryness by rotary evapora-
tion. The resulting residue was re-dissolved in 0.5 mL H2O and
loaded onto a pre-conditioned C18 SepPakÒ cartridge (Waters),
which was subsequently eluted with 7 mL H2O, 3 mL 1:1
H2O:CH3CN, and 5 mL CH3CN giving a total of 15 ꢂ 1 mL fractions.
Fractions 10 and 11 contained a single, UV and Pd-active product,
which was confirmed by mass spectrometry to be the desired prod-
uct. These were combined, concentrated by rotary evaporation, and
lyophilized giving a light white solid (15 mg, 32%). Signals for the
3.18. Radiolabelling
A 1.0 mg/mL solution of each ligand was prepared in H2O con-
taining 5% acetic acid (1), or in the case of the benzamides 7 and
8, a 1:1 solution of 5% HOAc/H2O:CH3CN. To a 2 mL reaction vial,
were added 100
ate oxidant (1: IodogenÒ, 7 or 8: chloramine-T as 20
mL solution in water). To these solutions were added Na[125I] (20–
150 Ci, 0.74–5.6 MBq) in 0.1 N NaOH. The solutions were stirred
for five minutes before addition of 10 L 0.1 M Na2S2O5 to reduce
lL of the ligand solution and 20
l
g of an appropri-
other 3 isomers are denoted by , + and ꢂ. 1H NMR (600 MHz,
l
L of a 1.0 mg/
*
3
CD3OD): d 7.81–7.75 (m, 8H, H-20), 7.51 (d, 2H, J = 8.3 Hz, H-30),
3
7.46 (d, 5H, J = 8.3 Hz, H-30), 3.99 (d, 1H, 2J = ꢀ11.0 Hz, H-7), 3.97
l
(d, 1H, 3J = 7.7 Hz, H-1), 3.93 (d, 1H, 2J = ꢀ10.9 Hz, H-7), 3.86 (d,
1H, 3J = 7.6 Hz, H-1), 3.74 (dd, 1H, 2J = ꢀ12.0 Hz, 3J = 2.4 Hz, H-
6(*)), 3.70–3.66 (m, 3H, H-7, H-6, H-6(+)), 3.63 (d, 1H, 3J = 7.6 Hz,
H-1), 3.62–3.52 (m, 7H, 3 H-7, H-6, H-6(*), H-6(ꢂ), H-6(+)), 3.41 (dd,
1H, 2J = ꢀ11.8 Hz, 3J = 5.6 Hz, H-6(ꢂ)), 3.36 (d, 1H, 3J = 7.5 Hz, H-1),
3.30–3.09 (m, 13H, H-7, H-2, H-3, H-4), 3.03 (ddd, 1H, H-5), 2.99
(ddd, 1H, H-5(*)), 2.95 (ddd, 1H, H-5(ꢂ)), 2.88 (ddd, 1H, H-5(+)),
2.87 (d, 1H, 2J = ꢀ10.8 Hz, H-7), 2.80–0.10 (br, B-H), ꢀ2.30, ꢀ2.44
(br, B-H-B). 13C NMR (150 MHz, CD3OD) d 173.0, 147.0, 146.9,
145.9, 145.8, 133.4, 132.5, 132.3, 129.5, 129.2, 129.1, 129.0, 104.1,
104.0, 103.7, 103.3, 77.8, 77.5, 77.4, 76.0, 75.5, 75.4, 75.2, 75.1,
l
any oxidized forms of radioiodine. Products were isolated via
semi-preparative HPLC (Method B, Dynamax 10 ꢂ 250mm C18 col-
umn at 4.7 mL/min). The radioiodinated compounds were charac-
terized by correlation of their HPLC retention times with those of
the non-radioactive analogues (Method B).
3.19. LogP calculations
LogP measurements were made using the ‘‘shake-flask” method
described by Wilson and co-workers [79]. Radioiodinated com-

A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
1745
pounds [125I]-15 and [125I]-16 were concentrated to dryness and
References
reconstituted in 1 mL of phosphate-buffered saline. The saline
was added to a vial containing 2 mL phosphate buffer and 3 mL
of 1-octanol. The flask was shaken on a vortex mixer for 3 min,
and the respective layers separated. The octanol layer was taken,
and divided (0.5 mL) among four ‘‘partitioning” vials containing
1.5 mL phosphate buffer (pH 7.4) and 1.0 mL 1-octanol. These vials
were shaken on a vortex mixer for 10 min, followed by centrifuga-
tion for a further 5 min. Aliquots (0.5 mL) of each layer were trans-
ferred to pre-weighed vials, counted for activity, and counts/mL
calculated from the weight of solution transferred. LogP was
calculated as log {[counts/mL(1-octanol)]/[counts/mL(buffer)]}.
The reported values correspond to the average of four measure-
ments standard deviation.
[1] R.N. Grimes, Carboranes, Academic Press, New York, 1970.
[2] R.A. Wiesboeck, M.F. Hawthorne, J. Am. Chem. Soc. 86 (1964) 1642.
[3] M.F. Hawthorne, D.C. Young, P.M. Garrett, D.A. Owen, S.G. Schwerin, F.N. Tebbe,
P.A. Wegner, J. Am. Chem. Soc. 90 (1968) 862.
[4] L.I. Zakharkin, V.N. Kalinin, Tetrahedron Lett. 7 (1965) 407.
[5] M.A. Fox, W.R. Gill, P.L. Herbertson, J.A.H. MacBride, K. Wade, H.M. Colquoun,
Polyhedron 15 (1996) 565.
[6] M.A. Fox, K. Wade, J. Organomet. Chem. 573 (1999) 279.
[7] J. Yoo, J.-W. Hwang, Y. Do, Inorg. Chem. 40 (2001) 568.
[8] T.L. Heying, J.W.J. Ager, S.L. Clark, D.L. Mangold, H.L. Goldstein, M. Hillman, R.J.
Polak, J.W. Szymanski, Inorg. Chem. 2 (1963) 1089.
[9] M.M. Fein, J. Bobinski, N. Mayes, N. Schwartz, M.S. Cohen, Inorg. Chem. 2
(1963) 1111.
[10] V.I. Bregadze, Chem. Rev. 92 (1992) 209.
[11] I.P. Beletskkaya, V.I. Bregadze, V.A. Ivushkin, P.V. Petrovskii, I.B. Sivaev, S.
Sjoberg, G.G. Zhigareva, J. Organomet. Chem. 689 (2004) 2920.
[12] R. Coult, M.A. Fox, W.R. Gill, P.L. Herbertson, J.A.H. MacBride, K. Wade, J.
Organomet. Chem. 462 (1993) 19.
[13] R. Alberto, R. Schibli, A. Egli, P.A. Schubiger, U. Abram, T.A. Kaden, J. Am. Chem.
Soc. 120 (1998) 7987.
3.20. Cell binding studies
Following similar methods to those reported by Dittmann and
co-workers [72], cells were seeded at a density of 2 ꢂ 105 cells in
25 cm3 vented cap cell culture flasks (430639, Corning) 2 days
[14] N. Lazarova, S. James, J. Babich, J. Zubieta, Inorg. Chem. Commun. 7 (2004)
1023.
[15] M.F. Hawthorne, D.C. Young, P.A. Wegner, J. Am. Chem. Soc. 87 (1965) 1818.
[16] M.F. Hawthorne, D.C. Young, T.D. Andrews, D.V. Howe, R.L. Pilling, A.D. Pitts, M.
Rintjes, L.F. Warren Jr., P.A. Wegner, J. Am. Chem. Soc. 90 (1968) 879.
[17] M.F. Hawthorne, G.B. Dunks, Science 178 (1972) 462.
[18] M.F. Hawthorne, J. Organomet. Chem. 100 (1975) 97.
[19] M. Corsini, F.F. de Biani, P. Zanello, Coord. Chem. Rev. 250 (2006) 1351.
[20] F.P. Olsen, M.F. Hawthorne, Inorg. Chem. 4 (1965) 1839.
[21] M.F. Hawthorne, A. Maderna, Chem. Rev. 99 (1999) 3421.
[22] D.S. Wilbur, M.-K. Chyan, D.K. Hamlin, B.B. Kegley, R. Risler, P.M. Pathare, J.
Quinn, R.L. Vessella, C. Foulton, M. Zalutsky, T.J. Wedge, M.F. Hawthorne,
Bioconjugate Chem. 15 (2004) 203.
[23] J.A. Kerr, in: D.R. Lide (Ed.), CRC Handbook of Chemistry and Physics, CRC
Press, Boca Raton, FL, 1993, p. 9.
[24] S. Ghirmai, J. Malmquist, H. Lundquist, V. Tolmachev, S. Sjoberg, J. Label.
Compd. Radiopharm. 47 (2004) 557.
[25] E.A. Mizusawa, M.R. Thompson, M.F. Hawthorne, Inorg. Chem. 24 (1985) 1911.
[26] A. Varadarajan, R.M. Sharkey, D.M. Goldenberg, M.F. Hawthorne, Bioconjugate
Chem. 2 (1991) 102.
[27] R.J. Paxton, B.G. Beatty, A. Varadarajan, M.F. Hawthorne, Bioconjugate Chem. 3
(1992) 241.
prior to the experiment. L-tyrosine (Sigma, Oakville, ON) was added
to the media to a final concentration of 2 mM. Each time-point had
three replicate flasks, as well as a control flask not receiving radio-
active compound. After 48 h, the 125I-labelled compound
(ꢃ25 kBq) was added to each flask in a volume of 50
lL and cells
were incubated for 1, 2, 6, 12 or 24 h at 37 °C and 5% CO2. At each
time-point, media was removed from cells and saved for counting.
Cells were washed twice with PBS (each wash being retained for
analysis) and then trypsinized. Once cells had lifted from flask,
they were collected for analysis. The activity in the cells, media
and the wash from each sample were counted for 60 s using the
Perkin–Elmer Wizard Pro gamma counter. Counts per minute
(cpm) were analyzed as percentage of total counts from cells and
wash supernatants. Uptake values represent the percentage of
the initial activity added to the cells and are the average of three
measurements standard deviation.
[28] C.-J. Chen, R.R. Kane, F.J. Primus, G. Szalai, M.F. Hawthorne, J.E. Shively,
Bioconjugate Chem. 5 (1994) 557.
[29] F.J. Primus, R.H. Pak, K.J. Rickard-Dickson, G. Szalai, J. Bolen, R.R. Kane, M.F.
Hawthorne, Bioconjugate Chem. 7 (1996) 532.
[30] D.S. Wilbur, D.K. Hamlin, R.R. Srivastava, J. Label. Compd. Radiopharm. 35
(1994) 199.
4. Conclusion
[31] D.S. Wilbur, D.K. Hamlin, J.C. Livesey, R.R. Srivastava, G.E. Laramore, T.W.
Griffin, Nucl. Med. Biol. 21 (1994) 601.
[32] D.S. Wilbur, D.K. Hamlin, P.M. Pathare, B.B. Kegley, J. Label. Compd.
Radiopharm. 42 (S1) (1999) S288.
[33] D.S. Wilbur, D.K. Hamlin, M.-K. Chyan, B.B. Kegley, J. Quinn, R.L. Vessella,
Bioconjugate Chem. 15 (2004) 601.
[34] D.S. Wilbur, M.-K. Chyan, D.K. Hamlin, R.L. Vessella, T.J. Wedge, M.F.
Hawthorne, Bioconjugate Chem. 18 (2007) 1226.
A bifunctional nido-carborane ligand containing a carbohydrate
group and a benzoic acid substituent for linking the cluster to
amine-bearing targeting vectors was prepared. Benzamide deriva-
tives of the nido-carborane ligand and its non-glycosylated ana-
logue were synthesized as model conjugates, and subsequently
labelled with 125I. Lipophilicity measurements confirmed the in-
crease in hydrophilicity associated with the presence of a carbohy-
drate group. The carbohydrate had a detrimental impact on the
uptake of the benzamides by melanoma cells relative to both the
control compound, [125I]BZA, and the non-glycosylated nido-carbo-
rane-benzamide analogue. The general utility of the reported li-
gands for preparing targeted molecular imaging probes by
conjugating to more specific bio-vectors remains work in progress.
[35] A. Sjostrom, V. Tolmachev, O. Lebeda, J. Koziorowski, J. Carlsson, H. Lundquist,
J. Radioanal. Nucl. Chem. 256 (2003) 191.
[36] R. Haubner, H.-J. Wester, W.A. Weber, C. Mang, S.I. Ziegler, S.L. Goodman, R.
Senekowitsch-Schmidke, H. Kessler, M. Schwaiger, Cancer Res. 61 (2001) 1781.
[37] R. Haubner, H.-J. Wester, F. Burkhart, R. Senekowitsch-Schmidke, W. Weber,
S.L. Goodman, H. Kessler, M. Schwaiger, J. Nucl. Med. 42 (2001) 326.
[38] R. Haubner, B. Kuhnast, C. Mang, W.A. Weber, H. Kessler, H.-J. Wester, M.
Schwaiger, Bioconjugate Chem. 15 (2004) 61.
[39] H.-J. Wester, M. Schottelius, K. Scheidhauer, J.-C. Reubi, I. Wolf, M. Schwaiger,
Eur. J. Nucl. Med. 29 (2002) 28.
[40] H.-J. Wester, M. Schottelius, K. Scheidhauer, G. Meisetschlager, M. Herz, F.C.
Rau, J.-C. Reubi, M. Schwaiger, Eur. J. Nucl. Med. 30 (2003) 117.
[41] M. Schottelius, H.-J. Wester, J.-C. Reubi, R. Senekowitsch-Schmidke, M.
Schwaiger, Bioconjugate Chem. 13 (2002) 1021.
Acknowledgements
[42] M. Schottelius, J.-C. Reubi, V. Eltschinger, M. Schwaiger, H.-J. Wester, J. Med.
Chem. 48 (2005) 2778.
[43] M. Schottelius, F. Rau, J.-C. Reubi, M. Schwaiger, H.-J. Wester, Bioconjugate
Chem. 16 (2005) 429.
[44] O.O. Sogbein, A.E.C. Green, P. Schaffer, R. Chankalal, E. Lee, B.D. Healy, J.F.
Valliant, Inorg. Chem. 44 (2005) 9574.
[45] A.E.C. Green, L.E. Harrington, J.F. Valliant, Can. J. Chem. 86 (2008) 1063.
[46] H.B. Mereyala, S.R. Gurrala, Carbohydr. Res. 307 (1998) 351.
[47] G.B. Giovenzana, L. Lay, D. Monti, G. Palmisano, L. Panza, Tetrahedron 55
(1999) 14123.
This research was funded by NSERC of Canada and the Canadian
Institutes for Health Research. We gratefully acknowledge the
McMaster Nuclear Reactor (125I) for providing isotopes. AECG
wishes to acknowledge Amanda Donovan for helpful discussions
and for the generous gift of synthetic precursors to [125I]BZA.
Appendix A. Supplementary material
[48] K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. 16 (1975) 4467.
[49] Q. Li, A.V. Rukavishnikov, P.A. Petukhov, T.O. Zaikova, C. Jin, J.F. Keana, J. Org.
Chem. 68 (2003) 4862.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2008.12.063.

1746
A.E.C. Green et al. / Journal of Organometallic Chemistry 694 (2009) 1736–1746
[50] R. Roy, S.K. Das, R. Dominique, M.C. Trono, F. Hernandez-Mateo, F. Santoyo-
Gonzalez, Pure Appl. Chem. 71 (1999) 565.
[51] R. Roy, S.K. Das, F. Santoyo-Gonzalez, F. Hernandez-Mateo, T.K. Dam, F.C.
Brewer, Chem. Eur. J. 6 (2000) 1757.
[64] M. Wolf, U. Bauder-Wust, A. Mohammed, F. Schonsiegel, W. Mier, U.
Haberkorn, M. Eisenhut, Melanoma Res. 14 (2004) 353.
[65] M. Wolf, U. Bauder-Wust, U. Haberkorn, W. Mier, M. Eisenhut, Melanoma Res.
15 (2005) 383.
[52] R. Roy, S.K. Das, F. Hernandez-Mateo, F. Santoyo-Gonzalez, Z. Gan, Synthesis 7
(2001) 1049.
[66] M. Wolf, H. Eskerski, U. Bauder-Wust, U. Haberkorn, M. Eisenhut, Melanoma
Res. 16 (2006) 487.
[53] J.M. Michelot, M.F.C. Moreau, P.G. Labarre, J.C. Madelmont, A.J. Veyre, J.M.
Papon, D.F. Parry, J.F. Bonafous, J.Y.P. Boire, G.G. Desplanches, S.J. Bertrand, G.
Meyniel, J. Nucl. Med. 32 (1991) 1573.
[54] M.F. Moreau, J. Michelot, J. Papon, M. Bayle, P. Labarre, J.C. Madelmont, D.
Parry, J.Y. Boire, N. Moins, H. Seguin, A. Veyre, L. Mauclaire, Nucl. Med. Biol. 22
(1995) 737.
[55] N. Moins, J. Papon, H. Seguin, D. Gardette, M.F. Moreau, P. Labarre, M. Bayle, J.
Michelot, J.-C. Gramain, J.C. Madelmont, A. Veyre, Nucl. Med. Biol. 28 (2001)
799.
[56] P. Labarre, J. Papon, M.F. Moreau, N. Moins, M. Bayle, A. Veyre, J.C. Madelmont,
Melanoma Res. 12 (2002) 115.
[57] S. Mansard, J. Papon, M.F. Moreau, E. Miot-Noirault, P. Labarre, M. Bayle, A.
Veyre, J.C. Madelmont, N. Moins, Nucl. Med. Biol. 32 (2005) 451.
[58] M.F. Moreau, J. Papon, P. Labarre, N. Moins, M. Borel, M. Bayle, B. Bouchon, J.C.
Madelmont, Nucl. Med. Biol. 32 (2005) 377.
[59] C.S. John, W.D. Bowen, T. Saga, S. Kinuya, B.J. Vilner, J. Baumgold, C.H. Paik, R.C.
Reba, R.D. Neumann, V.M. Varma, J.G. McAfee, J. Nucl. Med. 34 (1993) 2169.
[60] C.S. John, T. Saga, S. Kinuya, N. Le, J.M. Jeong, C.H. Paik, R.C. Reba, V.M. Varma,
J.G. McAfee, Nucl. Med. Biol. 20 (1993) 75.
[61] C. Nicholl, A. Mohammed, W.E. Hull, B. Bubeck, M. Eisenhut, J. Nucl. Med. 38
(1997) 127.
[62] A. Mohammed, C. Nicholl, U. Titsch, M. Eisenhut, Nucl. Med. Biol. 24 (1997)
373.
[67] W. Brandau, B. Kirchner, P. Bartenstein, J. Sciuk, D. Kamanabrou, O. Schober,
Eur. J. Nucl. Med. 20 (1993) 238.
[68] L. Maffioli, L. Mascheroni, C. Clemente, M. Baldini, M.R. Castellani, J. Nucl. Biol.
Med. 37 (1993) 18.
[69] L. Maffioli, L. Mascheroni, V. Mongioj, M. Gasparini, M.T. Baldini, E. Seregni,
M.R. Castellani, N. Cascinelli, G. Buraggi, J. Nucl. Med. 35 (1994) 1741.
[70] H.H. Coenen, W. Brandau, H. Dittmann, J. Label. Compd. Radiopharm. 37 (1995)
260.
[71] W. Brandau, T. Niehoff, P. Pulawski, M. Jonas, K. Dutschka, J. Sciuk, H.H.
Coenen, O. Schober, J. Nucl. Med. 37 (1996) 1865.
[72] H. Dittmann, H.H. Coenen, F. Zolzer, K. Dutschka, W. Brandau, C. Streffer, Nucl.
Med. Biol. 26 (1999) 51.
[73] R. Larisch, K.-W. Schulte, H. Vosberg, T. Ruzicka, H.-W. Muller-Gartner, J. Nucl.
Med. 39 (1998) 996.
[74] M.M. Edreira, O.R. Pozzi, Melanoma Res. 16 (2006) 37.
[75] T.Q. Pham, I. Greguric, X. Liu, P. Berghofer, P. Ballantyne, J. Chapman, F.
Mattner, B. Dikic, T. Jackson, C. Loc’h, A. Katsifis, J. Med. Chem. 50 (2007) 3561.
[76] S. Hermanek, Chem. Rev. 92 (1992) 325.
[77] R. Brockman, K. Challis, G. Froehner, T.D. Getman, Main Group Met. Chem. 25
(2002) 629.
[78] M. Bietti, A. Cuppoletti, C. Dagostin, C. Florea, C. Galli, P. Gentili, H. Petride, C.R.
Caia, Eur. J. Org. Chem. (1998) 2425.
[79] A.A. Wilson, L. Jin, A. Garcia, J.N. Da Silva, S. Houle, Appl. Radiat. Isot. 54 (2001)
203.
[63] M. Eisenhut, W.E. Hull, A. Mohammed, W. Mier, D. Lay, W. Just, K. Gorgas, W.D.
Lehmann, U. Haberkorn, J. Med. Chem. 43 (2000) 3913.
[80] J.K. Prashar, D.E. Moore, J. Chem. Soc., Perkin Trans. I (1993) 1051.