Preparation and characterization of technetium-99m complexes with new diphosphines containing polyether groups

Article abstract of DOI:10.1002/jlcr.1005

We report the synthesis and characterization of three new diphosphine ligands with polyether groups of general formula R(OCH₂CH ₂)_nPPhCH₂CH₂PPh(CH ₂CH₂O)_nR: 1 (R = Me, n = 3), 2 (R = Bu, n = 3) and 3 (R = Bu, n = 4). trans-[^99mTcO₂L₂] ⁺ complexes were prepared by reaction between the diphosphine ligands and the ^99mTc-gluconate precursor. The homologous rhenium complexes, trans-[ReO₂L₂]Cl (L = 1,2,3), were synthesized by ligand substitution reaction with [ReO₂py₄]Cl and oxorhenium (V) gluconate, and characterized by IR, ESMS and ¹H, ¹³C{ ¹H}, ³¹P{¹H} NMR spectroscopy. All these data are consistent with the formation of diphosphine complexes chelated to the trans-ReO₂ unit. The HPLC analyses of rhenium and ^99mTc complexes display very similar profiles and retention times, consistent with the formation of the homologous complexes. Preliminary biodistribution studies with rats show significant differences between the behaviour of the three ^99mTc complexes. Copyright

Full text of DOI:10.1002/jlcr.1005

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS
J Label Compd Radiopharm 2005; 48: 909–921.
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jlcr.1005
Research Article
Preparation and characterization of technetium-99m
complexes with new diphosphines containing polyether
groups
1
Esteve Valls , David Martin , Carlos Piera and Joan Suades *
1
2
1,
1
Departament de Quı ´m ica, Edifici C, Universitat Auto`noma de Barcelona, 08193
Bellaterra, Spain
2
Catalana de Dispensacio´n S. A., Josep Anselm Clave´ 100, 08950 Esplugues de
Llobregat, Spain
Summary
We report the synthesis and characterization of three new diphosphine ligands with
polyether groups of general formula R(OCH CH ) PPhCH CH PPh(CH CH O) R:
2
2 n
2
2
2
9m
2
n
9
+
1
(R ¼ Me, n ¼ 3), 2 (R ¼ Bu, n ¼ 3) and 3 (R ¼ Bu, n ¼ 4). trans-[ TcO L ]
complexes were prepared by reaction between the diphosphine ligands and the
2
9m
2
9
Tc-
gluconate precursor. The homologous rhenium complexes, trans-[ReO L ]Cl
2
2
(
L=1,2,3), were synthesized by ligand substitution reaction with [ReO py ]Cl and
2 4
1
13
1
31
1
oxorhenium (V) gluconate, and characterized by IR, ESMS and H, Cf Hg, Pf Hg
NMR spectroscopy. All these data are consistent with the formation of diphosphine
9
9m
Tc
complexes chelated to the trans-ReO unit. The HPLC analyses of rhenium and
2
complexes display very similar profiles and retention times, consistent with the
formation of the homologous complexes. Preliminary biodistribution studies with rats
9
9m
show significant differences between the behaviour of the three
Tc complex-
es. Copyright # 2005 John Wiley & Sons, Ltd.
9
9m
Key Words: diphosphine; ether phosphine;
TcO -core; biodistribution
2
Introduction
Technetium-99m complexes with diphosphine ligands have been widely
studied. Some of them, such as the ligand (1,2-bis(bis-2-ethoxyethyl)phos-
9
9m
phino)ethane (tetrofosmin), are used to prepare
Tc radiopharmaceuticals.
This diphosphine with ether groups is commercialized by Amersham as a
*Correspondence to: Joan Suades, Departament de Quımica, Edifici C, Universitat Autonoma de
´ `
Barcelona, 08193 Bellaterra, Spain. E-mail: joan.suades@uab.es
Contract/grant sponsor: Direccion General de Investigacion Cientıfica y Tecnica
´ ´ ´ ´
Copyright # 2005 John Wiley & Sons, Ltd.
Received 24 June 2005
Revised 20 July 2005
Accepted 21 July 2005

9
10
E. VALLS ET AL.
1
1
myocardial imaging agent under the name Myoview . Several studies have
shown that the presence of ether groups in ligands designed for technetium
myocardial imaging improves biodistribution properties such as background
2,3
activity in blood and liver.
With this aim, the synthesis of new ether
diphosphine ligands and the study of their potential use in myocardial
4
perfusion imaging has been reported. To study the effect on the imaging
characteristics of several polyether chains and lipophilic groups linked to
diphosphine ligands, we designed the synthesis of three new diphosphine
5
ligands with polyether groups. These new ether-substituted diphosphine
ligands have a similar structure, but slight differences in the lengths of the
99m
polyether chain. The evaluation of their
Tc complexes in animal studies
may contribute to research into the association between the characteristics of
the ether groups and biodistribution. In addition, the new ligands contain a
butyl or a methyl group bonded to the end of the polyether chain. The
different lipophilic characters of these ligands can supply information about
the influence of the lipophilicity of their technetium complexes on uptake into
3
the heart.
In this paper, we report the preparation of the new polyether diphosphines
9
9m
and their respective
Tc complexes. The homologous rhenium complexes
9
9m
were synthesized and used to characterize the
Tc complexes. Preliminary
biodistribution studies with rats are also reported.
Results and discussion
Preparation of ligands
Ligands 1–3 were synthesized from commercial polyethylene glycol monoalkyl
ethers, CH (OCH CH ) OH and CH (CH ) (OCH CH ) OH. The first step
3
2
2 3
3
2 3
2
2 n
6
consisted of the preparation of CH (OCH CH ) Cl, CH (CH ) (OCH
2
3
2
2 3
3
2 3
CH ) Cl and CH (CH ) (OCH CH ) Cl by reaction of the alcohols with
2
3
3
2 3
2
2 4
excess triphenylphosphine in carbon tetrachloride (Scheme 1). Distillation of
the products obtained from reaction with CH (CH ) (OCH CH ) OH (70%)
3
2 3
2
2 3
led to CH (CH ) (OCH CH ) Cl as a main product and to CH (CH )
2 3
3
2 3
2
2 3
3
(
OCH CH ) Cl as a minor product. Next, the reaction between the alkyl
2 2 4
7
chlorides and Li [PhPCH CH PPh] afforded ligands 1–3 (Scheme 2), which
2
2
2
PPh3
CCl4
O
O
n
R
n
Cl
R
OH
n = 3; R = CH , CH CH CH CH
2
3
3
2
2
n = 4; R = CH CH CH CH
2
3
2
2
Scheme 1.
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

PREPARATION AND CHARACTERIZATION OF TECHNETIUM-99M
R(OCH2CH2)nCl
2 LiCl
911
2
O
O
n
n
R
Ph(Li)P
P(Li)Ph
R
PhP
PPh
-
1
(R = CH3, n = 3)
2
3
(R = CH CH CH CH , n = 3)
2
3
2
2
(R = CH3CH2CH2CH2, n = 4)
Scheme 2.
were obtained as oily products, although various attempts at crystallization
were made. These products were characterized by NMR and mass spectro-
3
1
1
scopy. The Pf Hg NMR spectra of 1–3 were nearly identical. Each
compound showed two signals at ꢀ25.4 and ꢀ25.9 ppm, a chemical shift very
0
6
similar to other PhRP(CH CH O) R phosphines, and no other significant
2
2
n
peaks were observed. This result reveals the absence of other phosphorus
compounds and is consistent with the presence of a mixture of diastereoi-
1
13
1
somers (meso form and racemate). The H and Cf Hg NMR spectra are
consistent with the proposed structures, showing the fragments R(OCH CH )
2
2 n
and PhPCH CH PPh. The most relevant data are the couplings and chemical
2
2
shifts of methylene groups of the R(OCH CH ) fragment placed in alpha and
2 2 n
beta positions with respect to the phosphorus atom. Thus, the signals assigned
to the methylene groups in the alpha position were observed at 1.9–2.0 ppm as
a triplet of doublets separated from the resonances of the other methylene
groups. The methylene groups in the beta position could not be distinguished
1
from the other methylene groups bonded to oxygen in the H NMR spectra
and were seen as a multiplet at 3.3–3.6 ppm. Yet, these methylene groups are
1
13
properly recognized in the Cf Hg NMR spectra as a triplet at nearly 68 ppm.
This chemical shift is consistent with those reported for similar
0
6,8
PhRP(CH CH O) R ligands. The multiplicity of this signal is assigned to
2
2
n
the virtual coupling of the carbon nucleus with the two phosphorus atoms, as
31
9
13
1
described elsewhere. This hypothesis was corroborated by Cf H, Pg
NMR spectra, in which these signals are displayed as singlets, confirming the
1
3
1
previous assignment of the coupling in the Cf Hg NMR spectra to the
phosphorus atoms. Finally, M+1 ions gave the strongest signal in mass
spectroscopy (CI).
Preparation of rhenium complexes
+
The cold rhenium complexes [ReO L ] (L=1,2,3) were prepared at the
2
2
macroscopic level, in order to confirm the structure of the homolo-
9
gous [ TcO L ] (L=1,2,3) by comparison between the HPLC data. The
9m
+
2
2
rhenium complexes were prepared in two approaches, as shown in Scheme 3.
In the first, excess ligand in a dichloromethane solution was added to an
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

9
12
E. VALLS ET AL.
+
O
Re
O
py
py
py
+
py
-
4 py
+
O
Re
O
P
P
P
P
P
P
+
[ReO(gluc)2]-
-
2 [gluc]-
O
O
O
O
Me
Bu
3 P
P
3
Me
(
1)
Ph
Ph
P
P
=
3 P
P
3 Bu
(2)
Ph
Ph
O
O
Bu
4 P
P
4
Bu
(3)
Ph
Ph
-
[
gluc] = gluconate
Scheme 3.
ethanol solution of the dioxorhenium (V) complex [ReO py ]Cl. The resulting
2
4
mixture was refluxed for 4 h, and the colour of the solution turned from orange
to yellow. The residual oil obtained after evaporation was extracted with
hexane to eliminate the ligand excess and other residual products.
Unfortunately, no solid compounds could be obtained from these oily
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

PREPARATION AND CHARACTERIZATION OF TECHNETIUM-99M
913
products, although a large number of attempts were made with different
solvents and with substitution of chloride anion by other anions such as
ꢀ
ꢀ
[
BF ] and [PF ] . This behaviour may be explained by the formation of a
4 6
3
1
1
mixture of diasteroisomers because, as noted in the Pf Hg NMR spectra of
, 2 and 3, all these ligands are a mixture of the meso form and the racemate.
1
Although solid compounds could not be isolated, NMR and mass spectro-
scopy showed that only products with the diphosphine chelated to the metal
3
1
1
by means of the phosphorus atoms were obtained. Thus, the Pf Hg NMR
spectra of all reaction products only displayed a multiplet signal at 12.0–
1
2.6 ppm. The position of this signal shows a significant downfield shift after
coordination of the diphosphine to the metal fragment, as in other reported
+ 10
trans-[ReO (diphosphine) ] complexes. The multiplicity of the signals at
2
2
nearly 12 ppm is explained by the formation of a mixture of diasteroisomers.
The IR spectra are consistent with the presence of the dioxorhenium (V)
fragment in [ReO L ]Cl complexes (L=1,2,3). All prepared complexes had a
2
2
strong IR band at 786–802/cmꢀ that can be assigned to the characteristic
1
n (Re¼¼O) stretch of the trans-ReO fragment. Similar values have been
2
+
10
1
13
1
reported for other [ReO (diphosphine) ] complexes. The H and Cf Hg
2
2
NMR spectra of [ReO L ]Cl complexes (L=1,2,3) are similar to those of the
2
2
corresponding free ligands, but the signals are broader. Nevertheless, we want
to highlight the changes observed after complexation in the resonance assigned
to the carbon atom of the CH O group in the beta position with respect to the
2
phosphorus atom. Though this signal was in a position similar to those of the
free ligand, after complexation to the metal, multiplicity was reduced from a
triplet to two peaks in the 64–66.0 ppm region. The same splitting was
1
3
1
31
observed in Cf H, Pg NMR spectra, indicating that the peaks were due to
distinct diastereoisomers.
Finally, electrospray mass spectra of dichloromethane solutions of
[
ReO L ]Cl complexes (L=1,2,3) in positive ion mode displayed the
2 2
+
predominant signals of [M] ions, with isotope patterns in concordance with
the calculated distribution for the proposed stoichiometry, as shown in Figure
1
for the complex [ReO (1) ]Cl.
2 2
+
The dioxorhenium [ReO L ] complexes (L=1,2,3) were also prepared by
2
2
reaction at room temperature between an aqueous solution of the precursor
oxorhenium (V) gluconate and a solution of excess diphosphine ligands in
9
9m
tetrahydrofuran (thf) (Scheme 3). This precursor and its homologous
complex are widely used as labile complexes for the preparation of target
Tc
1
1
complexes by substitution of the gluconate ligands by more inert ligands.
1
31
The reaction products were studied by Pf Hg NMR spectroscopy and the
position and patterns of the peaks in the 12–13 ppm region were identical to
31
1
the signals observed in the Pf Hg NMR spectra of the [ReO L ]Cl
2
2
complexes (L ¼ 1; 2; 3) prepared from [ReO py ]Cl. This is consistent with
2
4
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

9
14
E. VALLS ET AL.
1
00
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
Figure 1. Positive-ion ES mass spectrum: calculated (white) and observed (grey)
+
isotope pattern for the [ReO (1) ] ion
2
2
the formation of the same complexes on following the two approaches
described in Scheme 3.
9
9m
Preparation of
Tc complexes
9
The [ TcO L ] complexes were prepared with the chelating diphoshine
9m
+
2
2
ligands 1–3 under no-carrier-added conditions by ligand substitution from the
9
9m
Tc-gluconate precursor, as shown in Scheme 4. The precursor was prepared
by reduction of [ TcO4]ꢀ with stannous chloride in the presence of
d-gluconate and monitored by HPLC analysis. The addition of the
diphosphine ligand to this solution at room temperature led to the formation
of the expected complexes, as shown by HPLC analysis. The HPLC analysis of
the three radiocomplexes showed the presence of a single broad peak with a
99m
9
9m
+-
retention time that was consistent with the formation of the [ TcO L ]
2
2
complexes (L=1: 31.9 min; L=2: 36.8 min; L=3: 35.2 min), since the
homologous rhenium complexes show similar retention times (L=1:
3
1.5 min; L=2: 34.9 min; L=3: 35.1 min) and signal profiles (Figure 2). The
RCP of the technetium complexes, evaluated by HPLC chromatography,
ranged between 85 and 90% for all complexes. All these data support the view
9
9m
that
Tc complexes form structurally identical to the rhenium complexes
described in the previous section.
+
O
9
9m
Tc-gluconate
P
P
99mTc
P
P
P
P
O
Scheme 4.
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

PREPARATION AND CHARACTERIZATION OF TECHNETIUM-99M
915
9
9m
+
Figure 2. HPLC profiles for [ TcO (3) ] (left) and [ReO (3) ] (right)
+
2
2
2
2
9
9m
+
Table 1. Biodistribution of [ TcO L ] in rats (% ID/g, N ¼ 3)
2
2
Tissues
L=1
L=2
L=3
Heart
Liver
Kidney
Lung
Muscle
0.20 ꢁ 0.02
0.36 ꢁ 0.03
0.38 ꢁ 0.04
0.15 ꢁ 0.02
0.06 ꢁ 0.03
0.03 ꢁ 0.01
0.29 ꢁ 0.06
0.25 ꢁ 0.05
0.05 ꢁ 0.01
0.02 ꢁ 0.01
0.04 ꢁ 0.01
0.88 ꢁ 0.11
0.78 ꢁ 0.08
0.08 ꢁ 0.02
0.03 ꢁ 0.01
Biological distribution studies
9
9m
+
The biodistribution of [ TcO L ] (L=1,2,3) complexes in rats is shown in
2
2
Table 1. The three compounds have notable differences in their biodistribu-
tion, corroborating that small changes in the molecular structure of the
complexes lead to large modifications in the biodistribution of radio-
complexes. Another point worthy of mention is that only complex with
ligand 1 show significant heart uptake and that this is practically zero for
complexes with ligands 2 and 3. This may be linked to the presence of the butyl
group in these complexes. Therefore, the increase in the lipophilic character of
these cations due to butyl groups does not lead to higher heart uptake, but, on
the contrary, uptake becomes virtually imperceptible. On comparing the
results between ligands 2 and 3, it is clear that the increase in the polyether
chain in complex with ligand 3 involves greater liver and kidney uptake, but
has no effect on heart uptake.
Experimental
Materials and methods
Diphosphine ligands and rhenium complexes were prepared under nitrogen by
standard Schlenk tube techniques. Unless otherwise stated, NMR spectra were
recorded on a Bruker AC250 instrument at the Nuclear Magnetic Resonance
Service at the Autonomous University of Barcelona (UAB). All chemical shift
values are expressed in ppm with respect to residual protons in the solvent for
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

9
16
E. VALLS ET AL.
13
proton spectra, to solvent signals for C spectra, and to external phosphoric
acid for phosphorus spectra. Mass spectra were recorded at the Chemical
Analysis Service of the UAB by a HP59-98X instrument (CI/NH ) and at the
3
Scientific-technical Service of the University of Barcelona (UB) with a VG-
Quattro (Micromass) instrument (ES). The HPLC analysis of labelled reaction
mixtures was performed on a Teknokroma nucleosil100 C-2 column (7 mm,
2
50 mm ꢂ 4 mm) at an isocratic flow rate of 1.0 ml/min of acetonitrile/water
8:2).
CH (CH ) (OCH CH ) OH (70%), NaReO and NH ReO were pur-
(
3
2 3
2
2 3
4
4
4
chased from Fluka, Alfa and Strem, respectively. The rhenium gluconate
1
1
6
7
solution and the compounds CH (OCH CH ) Cl, PhHP(CH ) PHPh and
3
2
2 3
2 2
12
[
ReO py ]Cl ꢃ 2H O were prepared following the published procedures.
2
4
2
The experiments with rats complied with the relevant national laws on
animal experiments. Male Sprague-Dawley rats weighing roughly 350 g were
anaesthetized with an intraperoneal injection of ketamine and isofluorane. A
99m
solution of each
Tc complex was prepared and two aliquots (300–400 mCi/
3
00 ml) were drawn with insulin syringes. One aliquot was used for doses and
the other one was diluted to 1000 ml. Three 1 ml portions of the resulting
solution were used as standards. All doses were administered intravenously to
rats via the tail vein. The animals (N ¼ 3) were sacrificed by asphyxiation using
carbon dioxide 60min post-injection. The heart, liver, muscle, lungs and kidneys
were removed and their activity was measured on a 1282 COMPUGAMMA CS
gamma-counter, LKB Wallac. Results are reported as the percentage injected
dose of organ per gram of the respective organ (% ID/g).
Preparation of the ligands
Synthesis of 1. Butyllithium 2.5 M (4.0 ml, 10.0 mmol) was dropwise added to
a solution of PhPHCH CH PHPh (0.90 g, 3.7 mmol) in thf (70 ml) cooled in
2
2
an ice bath, giving rise to an orange solution that was stirred for a few minutes.
The reaction mixture was kept in the ice bath and a solution of
CH (OCH CH ) Cl (1.35 g, 7.4 mmol) in thf (20 ml) was slowly added. The
3
2
2 3
ice bath was removed and the reaction mixture was allowed to warm to room
temperature. At this point, some drops of water were added to eliminate excess
butyllithium and the solvents were removed in vacuo. Water (50 ml) was added
to the residual oil and the mixture was extracted with hexane (3 ꢂ 50 ml),
which was subsequently dried over anhydrous Na SO and evaporated to
2
4
dryness in vacuo. Diphosphine 1 was obtained as an almost colourless oil.
Yield: 1.76 g (88%).
31
1
1
NMR data (CDCl ). Pf Hg: ꢀ25.9 (s), ꢀ25.4 (s). H: 1.5–1.8 (m, PCH
3
2
3
CH P), 1.91 (td, J =7.3 Hz, J =1.4 Hz, PCH CH O), 3.28 (s, OCH ),
2
2
H,H
H,P
2
2
3
13
1
3
.3–3.6 (m, CH O), 7.2–7.5 (m, Ph). Cf Hg (spectrum registered with a
2
Bruker ARX500 instrument): 23.6 (s, PCH CH O), 27.6 (dd, J =8.6 Hz,
2
2
PC
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

PREPARATION AND CHARACTERIZATION OF TECHNETIUM-99M
917
0
0
J
5
1
=5.7 Hz, PCH CH P), 27.8 (dd, J =8.6 Hz, J =4.8 Hz, PCH CH P),
2
PC
2
2
PC
PC
2
8.7 (s, OCH ), 67.8 (t, PCH CH O, J =10.5 Hz), 69.8–71.6 (m, CH O),
3
1
28.1 (b, Ph, C ), 128.7 (s, Ph, C ), 131.9 (b, Ph, C ), 137.2 (b, Ph, C ).
2
2
PC
2
3
4
2
MS (CI/NH ). m/z (M+1)=540.
3
Synthesis of 2. (a) Synthesis of CH (CH ) (OCH CH ) Cl. Triphenylpho-
2 3
3
2 3
2
sphine (100 g, 0.38 mol) was added to a solution of CH (CH ) (OCH CH ) OH
3
2 3
2
2 3
(59.8 g) in 300 ml of CCl . The alcohol CH (CH ) (OCH CH ) OH
4 3 2 3 2 2 3
was purchased as 70% w/w, and so the number of moles of CH (CH )
3
2 3
(
(
OCH CH ) OH was nearly 0.2. The other main product is CH (CH )
2 3
2
2 3
3
OCH CH ) OH. The resulting mixture was refluxed for 2 h and during this
2 2 4
period, P(O)Ph precipitated as a white solid. The mixture was allowed to cool
3
to room temperature, and pentane (150 ml) was added to complete the
precipitation of P(O)Ph and the remaining PPh . Solids were separated by
3
3
filtration and washed with pentane (75 ml). The resulting solution was
evaporated under vacuum, and a colourless oil was obtained, which was
distilled at reduced pressure (5 Torr), b.p. 100–1068C. Yield: 41.7 g ( ꢄ 90%).
Analysis by gas chromatography revealed the purity to be higher than 97%.
1
3
NMR data (CDCl3). H: 0.74 (t, JHH=7.3 Hz, CH ), 1.19 (sext.,
3
3
3
3
JHH=7.3 Hz, CH CH ), 1.38 (quint., J =7.3 Hz, CH CH CH ), 3.28 (t,
2
3
HH
2
2
3
13
1
JH,H=6.6 Hz, CH CH CH CH O), 3.3–3.7 (m, CH O, CH Cl). Cf Hg:
3
2
2
2
2
2
1
3.6 (s, CH ), 19.0 (s, CH CH ), 31.4 (s, OCH CH CH ), 42.3 (s, CH Cl),
2
3
2
3
2
2
2
6
9.8–71.1 (m, CH O).
2
MS (CI/NH ). m/z (M+18)=242.
3
(
b) Synthesis of [CH (CH ) (OCH CH ) P(Ph)CH ] . This step was
3 2 3 2 2 3 2 2
performed like the synthesis of 1. Particular data for this synthesis
are: PhPHCH CH PHPh (0.90 g, 3.7 mmols), 2.5 M butyllithium (4.0 ml,
2
2
3
0 mmol), CH (CH ) (OCH CH ) Cl, (1.66 g, 7.4 mmol). Yield: 1.95 g (85%).
3 2 3 2 2 3
31
1
1
3
NMR data (CDCl3). Pf Hg: –25.8 (s), ꢀ25.4 (s). H: 0.87 (t, JHH=
.3 Hz, CH ), 1.31 (sext., J =7.3 Hz, CH CH ), 1.50 (quint., J =7.3 Hz,
3
3
7
3
HH
2
3
HH
3
2
CH CH CH ), 1.6–1.8 (m, PCH CH P), 1.95 (td, J =7.3 Hz, JH,P=
2
2
3
2
2
H,H
1
3
1
1
.5 Hz, PCH CH O), 3.3–3.7 (m, CH O), 7.2–7.4 (m, Ph). Cf Hg: 13.7 (s,
2
2
2
CH ), 19.0 (s, CH CH ), 23.7 (s, PCH CH O), 28.2 (b, PCH CH P), 31.5 (s,
2
3
2
3
2
2
2
2
OCH CH CH ), 68.3 (t, PCH CH O, J =10.5 Hz), 69.8–70.9 (m, CH O),
2
2
2
2
2
PC
2
3
4
2
1
28.1 (b, Ph, C ), 128.7 (s, Ph, C ), 132.0 (b, Ph, C ), 137.2 (b, Ph, C ).
1
MS (CI/NH ): m/z (M+1)=624.
3
Synthesis of 3. (a) Synthesis of CH (CH ) (OCH CH ) Cl. This compound
2 4
3
2 3
2
was obtained as a second fraction (b.p. 132–1358C) in the reduced pressure
distillation of CH (CH ) (OCH CH ) Cl described above. Yield: 11.7 g.
3
2 3
2
2 3
Analysis by gas chromatography revealed a purity of ꢄ 93%.
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

9
18
E. VALLS ET AL.
1
NMR data (CDCl ). H: 0.72 (t, J =7.3 Hz, CH ), 1.17 (sext., JHH=
3
3
3
HH
3
3
3
7
6
.3 Hz, CH CH ), 1.37 (quint., J =7.3 Hz, CH CH CH ), 3.26 (t, JH,H=
2 3 HH 2 2 3
1
3
1
.6 Hz, CH CH CH CH O), 3.3–3.6 (m, CH O, CH Cl). Cf Hg: 13.4 (s,
3
2
2
2
2
2
CH ), 18.7 (s, CH CH ), 31.2 (s, OCH CH CH ), 42.1 (s, CH Cl), 69.6–70.8
2
3
2
3
2
2
2
(m, CH O).
2
MS (CI/ NH ). m/z (M+18)=286.
3
(
b) Synthesis of [CH (CH ) (OCH CH ) P(Ph)CH ] . This was per-
3 2 3 2 2 4 2 2
formed like the synthesis of 1. Particular data are: PhPHCH CH PHPh
2
2
(
(
0.90 g, 3.7 mmol), butyllithium 2.5 M (4.0 ml, 10.0 mmol), CH (CH2)3
3
OCH CH ) Cl (2.00 g, 7.4 mmol). Yield: 2.15 g (82%).
2
2 4
31
1
1
3
NMR data (CDCl3). Pf Hg: ꢀ25.9 (s), ꢀ25.4 (s). H: 0.80 (t, JHH=
3
3
7
.3 Hz, CH ), 1.25 (sext., J =7.3 Hz, CH CH ), 1.45 (quint., J =7.3 Hz,
3 HH 2 3 HH
3
2
CH CH CH ), 1.5–1.8 (m, PCH CH P), 1.88 (td, J =7.3 Hz, JH,P=
2
2
3
2
2
H,H
1
3
1
1
.5 Hz, PCH CH O), 3.3–3.6 (m, CH O), 7.2–7.4 (m, Ph). Cf Hg: 13.6 (s,
2
2
2
CH ), 18.9 (s, CH CH ), 23.6 (s, PCH CH O), 28.1 (b, PCH CH P), 31.3 (s,
2
3
2
3
2
2
2
OCH CH CH ), 68.2 (t, PCH CH O, J =10.5 Hz), 69.7–70.7 (m, CH O),
2
2
2
2
2
PC
2
3
28.0 (b, Ph, C ), 128.6 (s, Ph, C ), 131.9 (b, Ph, C ), 137.1 (s, Ph, C ).
4
2
1
1
MS (CI): m/z (M+1)=711.
Preparation of rhenium complexes
a) Reactivity towards [ReO py ]Cl ꢃ 2H O. Ligand 1. A solution of 1
(
2
4
2
(0.260 g, 0.48 mmol) in dichloromethane (5 ml) was added to a solution of
[
ReO py ]Cl ꢃ 2H O (0.100 g, 0.16 mmol) in EtOH (10 ml) and the reaction
2
4
2
mixture was refluxed for 4 h. During this period, the solution changed colour
from orange to yellow. The cold solution was evaporated to dryness and the
oily residue was vigorously extracted with hexane (3 ꢂ 20 ml). The residual oil
was dissolved in a few millilitres of dichloromethane and hexane was added
dropwise until a cloudy liquid was formed. The resulting mixture was cooled
to ꢀ108C and a yellow oil was formed that was separated and evaporated
under vacuum to yield a yellow oily product. Yield: 0.188 g (74%).
Analytically calculated for C H ClO P Re ꢃ 3CH Cl : C, 44.69; H, 5.98.
56
88
14
4
2
2
Found: C, 44.45; H, 5.79.
IR (KBr): n (Re¼¼O) 786/cm.
NMR data (CDCl3). Pf Hg: 12.1, 12.3 and 12.5 ppm. H: 1.5–2.8 (b,
31
1
1
1
3
1
PCH ), 3.3 (b, CH O, OCH ), 5.3 (CH Cl ), 6.9–7.4 (b, Ph). Cf Hg: 22.0 (b,
2
2
3
2
2
PCH CH O), 26.3 (b, PCH CH P), 58.3 (s, OCH ), 64.7 (s, PCH CH O), 65.4
2
2
2
2
3
2
2
3
4
(
(
s, PCH CH O), 69.7 (b, CH O), 71.2 (b, CH O), 128.3 (b, Ph, C , C ), 128.7
2 2 2 2
4
s, Ph, C ), 130.8 (b, Ph, C ).
2
MS(ES): m/z=1295. HPLC (R =31.5 min).
t
The reactions with ligands 2 and 3 were performed following the procedure
described for ligand 1 and the specific data for these preparations are as
follows:
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

PREPARATION AND CHARACTERIZATION OF TECHNETIUM-99M
919
Ligand 2. 2 (0.30 g, 0.48 mmol), [ReO py ]Cl ꢃ 2H O (100 mg, 0.16 mmol).
2
4
2
Yield: 0.210 g (79%).
Analytically calculated for C H ClO P Re ꢃ 2CH Cl : C, 50.37; H, 7.01.
Found: C, 49.88; H, 6.71.
68
112
14
4
2
2
IR (KBr): n (Re ¼¼ O) 802/cm.
NMR data (CDCl3). Pf Hg: 12.2, 12.3 and 12.5 ppm. H: 0.84 (b, CH ),
31
1
1
3
1
5
.29 (b, CH CH ), 1.50 (b, CH CH CH ), 1.9–2.8 (m, PCH ), 3.5 (b, CH O),
2
2
3
2
3
2
2
13
1
.3 (CH Cl ), 7.1–7.6 (m, Ph). Cf Hg: 13.7 (s, CH ), 19.0 (s, CH CH ), 27.2
2
2
3
2
3
(
b, PCH ), 31.5 (s, OCH CH CH ), 65.5 (b, PCH CH O), 69.8–70.9 (m,
2 2 2 2 2 2
3
CH O), 128.8 (b, Ph, C , C ), 131.2 (b, Ph, C ).
4
2
2
MS(ES): m/z=1463. HPLC (R =34.9 min).
t
Ligand 3. 3 (0.34 g, 0.48 mmol), [ReO py ]Cl ꢃ 2H O (100 mg, 0.16 mmol).
2
4
2
Yield: 0.250 g (81%).
Analytically calculated for C H ClO P Re ꢃ 3CH Cl : C, 49.16; H, 7.00.
76
128
18
4
2
2
Found: C, 48.99; H, 6.65.
IR (KBr): n (Re¼¼O) 797/cm.
31
1
1
NMR data (CDCl3). Pf Hg: 12.1, 12.2 and 12.5 ppm. H: 0.75–0.85 (m,
CH ), 1.23 (b, CH CH ), 1.42 (b, CH CH CH ), 1.9–2.8 (m, PCH ), 3.3–3.6
3
2
3
2
2
3
2
1
3
1
(
m, CH O), 5.3 (CH Cl ), 7.0–7.5 (m, Ph). Cf Hg: 13.5 (s, CH ), 18.8 (s,
2
2
2
3
CH CH ), 22.0 (b, PCH CH O), 26.7 (b, PCH CH P), 31.2 (s,
2
2
3
2
2
2
OCH CH CH ), 64.9 (s, PCH CH O), 65.6 (s, PCH CH O), 69.7–70.7 (m,
2
2
2
2
2
2
2
3
CH O), 128.5 (b, Ph, C , C ), 131.1 (b, Ph, C ).
4
2
2
MS(ES): m/z=1640. HPLC (R =35.1 min).
t
(
b) Reactivity towards rhenium (V) gluconate. Ligand 1. A solution of 1
(
(
0.51 g, 0.95 mmol) in thf (5 ml) was added to a solution of rhenium gluconate
5.0 ml, 0.32 mmol) in water. After 4 days of stirring at room temperature,
the initially dark blue mixture changed to pale yellow colour. The reaction
3
1
1
mixture was evaporated in vacuo and an oily residue was obtained. Pf Hg
NMR (CDCl ): 12.2, 12.4 and 12.6 ppm (signals of free ligand were also
3
observed).
Reactions with ligands 2 and 3 were performed as described for 1 and the
specific data are:
+
[
ReO (2) ] : 2 (0.59 g, 0.95 mmol), rhenium (V) gluconate (5.0 ml,
2 2
0
.32 mmol).
1
3
1
Pf Hg NMR (CDCl ): 12.3, 12.5, and 12.7 ppm (signals of free ligand
3
were also observed).
+
[
ReO (3) ] : 3 (0.67 g, 0.95 mmol), rhenium (V) gluconate (5.0 ml,
2 2
0
.32 mmol).
1
3
1
Pf Hg NMR (CDCl ): 12.2, 12.4 and 12.7 ppm (signals of free ligand were
3
also observed).
Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921

9
20
E. VALLS ET AL.
9
9m
Preparation of
Tc complexes
Fifty microlitres of 0.1 M sodium gluconate and 25 ml of 0.005 M stannous
9
9m
chloride in HCl 0.05 M were added to a vial. Then, 1 ml of
TcO (30–
4
4
0 MBq) was added and the mixture was stirred for 10 min at room
9
9m
temperature. The complete reduction of the pertechnetate to
Tc-gluconate
was checked by ITLC-SG and HPLC. Afterwards, 50 ml of an ethanol solution
of the appropriate ligand (0.013 M) was added and the resulting solution was
stirred for 30 min at room temperature. Labelling yield: 85–90%.
9
9m
+
99m
+
HPLC: [ TcO (1) ]
2
(R =31.9 min), [ TcO (2) ]
t
(R =36.8 min),
t
2
2
2
9
[
9m
+
TcO (3) ] (R =35.2 min).
2 2 t
Conclusions
Three new diphosphine ligands were synthesized with polyether groups for
studying the influence of small changes in the structure of ligands in
9
9m
+
biodistribution. The [ TcO L ]
2
complexes were prepared and their
2
structure was established by comparison with studies performed with rhenium
complexes. Biodistribution studies show that the presence of the n-butyl ether
fragment leads to a practically zero heart uptake. It is only significant with the
methyl ether fragment.
Acknowledgements
This research was supported by the Direccio
´
´
n General de Investigacio
´
n
Cientıfica y Tecnica. Thanks are due to J. Martorell (Hospital Clı
´ ´
nic
Veterinari de la UAB) for valuable assistance with the rat experiments.
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Copyright # 2005 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2005; 48: 909–921