The total synthesis of a technetium chelate - Tamoxifen complex

Article abstract of DOI:10.1139/v98-220

A potential agent for imaging breast cancer has been synthesized by derivatization of the anti-estrogen tamoxifen. A multistep synthesis was required to conjugate a technetium chelate to tamoxifen in such a fashion that the biodistribution of the complex should mimic that of the parent compound.

Full text of DOI:10.1139/v98-220

146
The total synthesis of a technetium chelate –
tamoxifen complex
Russell A. Bell, Kieran C. Dickson, and John F. Valliant
Abstract: A potential agent for imaging breast cancer has been synthesized by derivatization of the anti-estrogen
tamoxifen. A multistep synthesis was required to conjugate a technetium chelate to tamoxifen in such a fashion that the
biodistribution of the complex should mimic that of the parent compound.
Key words: tamoxifen, radioimaging, technetium, synthesis.
Résumé : En procédant à la préparation d’un dérivé du tamoxifène, un anti-estrogène, on a synthétisé un agent
pouvant éventuellement être utilisé dans l’imagerie du cancer du sein. Il a fallu recourir à une synthèse en plusieurs
étapes pour conjuguer un chélate du technétium au tamoxifène d’une façon telle que la biodistribution du complexe
puisse ressembler à celle du composé parent.
Mots clés : tamoxifène, radioimagerie, technétium, synthèse.
[Traduit par la Rédaction] Bell et al. 154
suggests that ring B derivatives alter the pharmacological
activity of tamoxifen (6). From the aforementioned binding
One method of developing a site-specific radioimaging
agent is to derivatize a drug or bioactive molecule with a
chelate – radio nuclide complex (1). To maintain receptor
selectivity the chelate must be attached to the biomolecule at
a point distant from the part of the molecule which binds to
the receptor. One bioactive compound of particular interest
is tamoxifen (Fig. 1), a drug used for the treatment of hor-
mone dependent breast cancer (2). An imaging agent based
on tamoxifen could potentially detect tumours in their in-
fancy, which is crucial if chemotherapy is to be effective (3).
Tamoxifen, (Z-1(p-(2-dimethylaminoethoxy)phenyl)-1,2-di-
phenylbut-1-ene) exerts its biological effect by binding to
estrogen receptors which, for certain types of cancers, are
more numerous in cancer cells than normal cells (4). 131I de-
rivatives of E and Z tamoxifen were used successfully to im-
age tumours in mice (5); however, there was insufficient
uptake in human cancer patients to develop a commercial
imaging agent. The location of the iodine label and the loss
of iodine due to the relatively weak carbon–iodine bond
could explain the insufficient tumour uptake in human breast
cancer tumours. One method of overcoming these problems
is to covalently attach a chelate, the technetium complex of
which is known to be stable in vivo, to a site in which sub-
stituents do not tend to affect the biodistribution of the par-
ent molecule.
studies of tamoxifen derivatives, ring A appears to be a
more attractive location for conjugation to a chelate.
E-2-methyl-tamoxifen, where the methyl substituent was in
the ortho position of ring A, had an estrogen receptor bind-
ing affinity identical to that of tamoxifen (7). From this, we
concluded that the ortho position of ring A would be a logi-
cal site, through a spacer chain, to attach a chelate.
The diamido dithiol (DADT) chelate (4, Scheme 1) (8),
which is known to bind 99mTc (t1/2 = 6.0, γ = 140 KeV), the
most commonly used radionuclide in diagnostic imaging,
was synthesized by modifying the approach used by Bell et
al. (9). 2,3-Diaminopropionic acid (1) was converted to the
methyl ester 2 via a Fisher esterification with p-toluenesul-
fonic acid prior to reaction with the N-hydroxysuccinimido
ester of S-triphenylmethylmercaptoacetic acid (1). In prepa-
ration for conjugation to the tamoxifen derivative (vide in-
fra) the methyl ester 3 was hydrolysed by reaction with
aqueous sodium hydroxide in THF to produce the desired
chelate 4.
Two approaches to the synthesis of DADT-tamoxifen con-
jugate were used; approach A involved the total synthesis of
the tamoxifen derivative before coupling to the chelate,
while strategy B entailed coupling of a chloro-tamoxifen
species to the chelate prior to the addition of the dimethyl-
amine moiety.
Substitution on ring B of tamoxifen is not feasible be-
cause data from binding assays of tamoxifen derivatives
Received June 18, 1998.
The synthesis, based on the approach of McCague and
co-worker (10) (Scheme 2) began by following the literature
procedure for the mono substitution of 1,2-dichloroethane by
phenolate under phase transfer conditions (11). The chloro-
ether was subsequently subjected to Friedel–Crafts acylation
(12) by use of either (±)-2-phenylbutyric acid and trifluoro-
acetic anhydride (TFAA) or the acid chloride of
R.A. Bell, K.C. Dickson, and J.F. Valliant.1 Department of
Chemistry, McMaster University, 1280 Main St. West,
Hamilton, ON L8S 4M1, Canada.
1Author to whom correspondence may be addressed.
Telephone: (905) 525-9140, ext. 23303. Fax: (905) 522-2509.
e-mail: valliant@chemistry.mcmaster.ca
Can. J. Chem. 77: 146–154 (1999)
© 1999 NRC Canada

Bell et al.
147
Scheme 1. Synthesis of DADT (4).
nals belonged to the E-isomer. The COSY spectrum was
then used to assign the remaining signals belonging to that
isomer, and it was concluded that the major isomer, as
Cram’s rules (14) predicted, was the E-isomer in a ratio of
approximately 5:1.
Fig. 1. Tamoxifen.
Fatty acid derivatives were selected as the spacer chain
because the length of the spacer can be altered easily as
there are numerous fatty acid derivatives which are commer-
cially available. Once the general synthetic route was devel-
oped, varying lengths of spacers can be tested until the
optimum length associated with high binding efficiency is
found. In the present synthesis (Scheme 3), bromododeca-
noic acid was converted to the azide prior to reaction with
thionyl chloride. The acid chloride was then converted to an
ester by reaction with alcohol 11. An unexpected advantage
of using the long-chain fatty acid was that small quantities
of each isomer of 12 could be separated by radial chroma-
tography. During the development of the synthetic method-
ology towards 15, a relatively large quantity of 12 was
required, and for practical purposes, the nonenriched 5:1 E:Z
ratio, material was used. Should the results of the biodistri-
bution studies show promise, the isomers of 12 can be sepa-
rated and pure E-15 and Z-15 synthesized. Because of the
ratio of 5:1 for E:Z isomers, it was possible to assign many
of the NMR signals for each isomer in mixtures of com-
pounds 13–17.
In approach A, the azido-chloride species 12 was con-
verted to the dimethylamino species 13 by reaction with
dimethylamine in ethanol at an elevated temperature. If ex-
tensive reaction times were used (greater than 4 days) a mi-
nor byproduct occurred as a result of cleavage of the ester
bond by either a dimethylamine or ethoxide nucleophile
with the resulting species being the phenethyl alcohol 11.
The azide 13 was reduced by the use of triphenylphosphine
(15) because other methods (lithium aluminum hydride and
catalytic hydrogenation) would cause reduction of the alkene
and (or) ester groups. Reduction appeared to occur quantita-
tively as indicated by TLC, however, isolation of the result-
ing amine was difficult, and only a low yield of product was
isolated (25%). The amine 14 was immediately coupled to
the chelate (4) by the use of EDC (16) in good yield, as
judged by thin-layer chromatography. Again, however, puri-
(±)-2-phenylbutyric acid and aluminum trichloride in carbon
disulfide (12) to give 6 in 79 and 57% yields, respectively.
Evidence from 1H and 13C NMR confirmed that the
acylation product was entirely para substituted. The linker
arm for the chelate was now added in the form of the
tert-butyldimethylsilyl ether of 2-bromophenethyl alcohol
(13), the nucleophile being generated by metal halogen ex-
change. The anion reacted with the ketone 6 to generate two
diasteriomeric alcohols 9, which were not normally isolated
but converted directly to the alkenes 10 by reaction with
thionyl chloride and pyridine at –10°C. These milder elimin-
ation conditions were used because the literature procedure
employing concentrated HCl in ethanol caused the loss of
the silyl protecting group and subsequent elimination of the
resultant alcohol. The silyl group of 10 was removed in
good yield (96%) by the use of tetrabutylammonium fluo-
ride in THF (13).
The chemical shift of the proton and carbon atoms of each
diasteriomer of 10, at 200 MHz and 50 MHz, respectively,
were significantly different and each isomer could be distin-
guished readily. To assign the signals of each isomer re-
quired the use of a two-dimensional nuclear Overhauser
1
effect (2-D NOE) experiment (NOESY). From the H spec-
trum the pair of doublets at 6.812 and 6.50 ppm were as-
signed to the AB spin system of ring B. The doublet at
6.812 ppm exhibited a NOE correlation to signals in the aro-
matic region but showed no correlation to the methylene of
the ethyl group of tamoxifen; this confirmed that these sig-
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148
Can. J. Chem. Vol. 77, 1999
Scheme 2. Synthesis of 11.
fication of the product proved difficult and resulted in a low
yield of the desired product (26%).
was no evidence for decomposition of the ester or amide
bonds so long as the reaction time was kept to a reasonable
length (20–24 h).
In an attempt to improve the yields of synthesis A, strat-
egy B was developed. The azide 12 was reduced by the use
of the aforementioned triphenylphosphine approach
(Scheme 4). Formation of the phosphonium salt from the
alkyl chloride fragment was not a concern because the re-
duction was carried out at room temperature. The resulting
amine 16 was coupled to the chelate in good yield (76%),
and replacement of the chloro substituent with
dimethylamine also occurred in good yield (60%). There
The addition of dimethylamine to 17 could be observed in
1
the H NMR as the two singlets at 2.325 and 2.267 ppm,
corresponding to the two isomers, were assigned to the
N-methyl protons. There was also a significant shift of the
methylene protons adjacent to the dimethylamine moiety,
upon substitution, the protons shifted upfield by approxi-
mately 1 ppm. The 13C NMR contained no ambiguities, the
resonances associated with the N-methyl protons were ob-
© 1999 NRC Canada

Bell et al.
149
Scheme 3. Synthesis of 15, approach A.
served at 45.80 ppm. The methylene protons adjacent to the
N-methyl moiety shifted downfield upon substitution of the
chloro group from 41.99 ppm to 58.18 ppm.
and 13C spectra, respectively. Coupling constants are given
in Hertz (Hz). All other NMR spectra were recorded on a
Bruker AC-200 spectrometer. Proton spectra were acquired
at 200.133 MHz with a 5 mm dual frequency probe. Spectra
were obtained in 8 scans in 16K data points over a 2.403
KHz spectral width (3.408 s acquisition time). Spectra were
acquired at ambient probe temperature. The free induction
decay (FID) was processed with exponential multiplication
(line broadening: 0.1 Hz) and was zero-filled to 32K before
Fourier transformation. Carbon-13 NMR spectra were re-
corded at 50.323 MHz with the 5 mm QNP probe. The spec-
tra were acquired over a 12.195 kHz spectral width in 16K
data points (0.672 s acquisition time).
Analytical TLC was performed on silica gel 60-F254
(Merck) with detection by long wavelength ultraviolet light.
Chromatography was performed with a chromatotron (Harri-
son Research Model 7924T) that used a 4 mm plate (EM
Science silica gel 60 PF254 that contained gypsum). All com-
mercial reagents were used as supplied. Solvents were dis-
tilled, under nitrogen, from calcium hydride. Nitrogen was
dried by passing it through calcium sulphate. All reactions
were protected from light and carried out under a slow flow
of nitrogen. Solvents were evaporated with a rotary evapora-
tor (20 mmHg (1 mmHg = 133.3 Pa)) at moderate tempera-
tures (30–50°C).
Synthetic procedures
Methyl 2,3-diaminopropanoate p-toluenesulfonate salt (2)
To 2.0 g (14.28 mmol) of (±) 2,3-diaminopropionic acid
monhydrochloride suspended in methanol (60 mL),
p-toluenesulfonic acid was added (10.82 g, 56.9 mmol). Af-
ter the solution was heated at reflux for 24 h it was evapo-
rated to dryness at reduced pressure, and the remaining solid
was washed with diethyl ether (200 mL), rendering the
methyl ester as colourless crystals. Yield: 6.5 g, 99%; mp
Selected NMR spectra were recorded on a Bruker Avance
DRX-500 spectrometer. Proton spectra were acquired at
500.130 MHz with a 5 mm broadband inverse probe with
triple-axis gradient capability. Spectra were obtained in 8
scans in 32K data points over a 4.006 kHz spectral width
(4.096 s acquisition time). The compounds used in this study
were dissolved in CDCl3 (Isotec, Inc.) to a concentration of
approximately 15.0 mg mL–1. Chemical shifts are reported
in ppm relative to TMS. The residual solvent signals at 7.24
1
200°C (decomp.); H NMR (CD3OD) (200 MHz) δ: 7.719
(d, J = 8.3, 2H, H-ortho), 7.251 (d, 2H, H-meta), 5.003 (brd,
NH), 4.494 (m, 1H, CH), 3.853 (s, 3H, OCH3), 3.529 (m,
2H, CH2), 2.354 (s, 3H, PhCH3); 13C NMR (CD3OD)
1
and 77.0 ppm were used as internal references for the H
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Can. J. Chem. Vol. 77, 1999
Scheme 4. Synthesis of 15, approach B.
(50 MHz) δ: 167.99 (COOMe), 143.00 (C-para), 141.99
(C-ipso), 129.91 (C-meta), 126.90 (C-ortho), 54.55 (CH),
51.14 (OCH3), 39.51 (CH2), 21.32 (Ph-CH3).
pH 3.9 using 6 M HCl, and concentrated to 30 mL under re-
duced pressure. The precipitate that formed was collected by
filtration, and the colourless solid washed with distilled
water (100 mL) and sparingly with ether (5 mL). The filtrate
was concentrated and diluted with methanol (15 mL) and re-
frigerated overnight. The resulting solid was collected by fil-
tration and washed again with distilled water and ether as
above, yielding an additional crop of the title compound.
Yield 900 mg, (97%); mp 214–215°C; TLC: Rf = 0.22 (10%
Methyl 2,3-bis(triphenylmethylthioacetylamino)propanoate
(3)
To 3.62 g (8.40 mmol) of 2-(triphenylmethylthio)ethanoic
acid-N-hydroxysuccinimido ester (1) dissolved in dichloro-
methane (50 mL), 1.92 g (4.16 mmol) of 2 was added. To
the rapidly stirred mixture, diisopropylethylamine (DIPEA)
(1.34 mL, 7.69 mmol) was added and the solution heated to
reflux for 8 h. The solution was cooled and extracted with
1 M HCl (2 × 10 mL), 1 M NaHCO3 (2 × 10 mL), and dis-
tilled water (distilled water) (3 × 15 mL). The solution was
evaporated to dryness at reduced pressure, and the solid was
washed with distilled water (200 mL), methanol (5 mL), and
ether (5 mL). The colourless solid was recrystallized from
acetone and subsequently dried in vacuo to give 2.2 g (78%)
of 3. The compound showed mp 68–70°C; TLC: Rf = 0.44
(2% CH3OH–CH2Cl2); 1H NMR (CDCl3) (200 MHz) δ:
7.324–7.075 (m, 17H, H-aryl), 6.708 (d, J = 6.7, 1H,
CHNH), 6.094 (m, 1H, CH2NH), 4.064 (m, 1H, CH), 3.087
(m, 2H, CHCH2), 2.934 (s, 2H, CH2); 13C NMR (CDCl3)
(50 Mhz) δ: 170.06 (COOMe), 168.55, 168.89 (C(O)NH),
143.87 (C-ipso), 129.50 (C-ortho), 128.09 (C-meta), 126.98
(C-para), 67.71 (Ph3C), 52.72 (CH and OCH3), 41.24
(CHCH2), 35.93 (CH2), 35.72 (SCH2).
1
CH3OH–CH2Cl2); H NMR (CD3OD) (200 MHz) δ: 7.643
(m, 15H, H-aryl), 4.590 (m, 1H, CH), 4.063 (m, 2H,
CH2CH), 3.269 (m, 2H, TrSCH2); 13C NMR (CD3OD)
(50 MHz) δ: 171.21 (C-COOH), 168.90, 168.55 (C(O)NH),
143.87 (C-ipso), 129.50 (C-ortho), 128.09 (C-meta), 126.98
(C-para), 65.88 (Ph3C), 52.05 (CH), 43.96 (CH2CH), 35.85,
32.33 (TrSCH2).
(2-Chloroethoxy)benzene
The procedure described by McCague (10) was used. Phe-
nol (28.2 g, 300 mmol), dimethyldioctadecylammonium bro-
mide (1.8 g, 3.0 mmol), sodium hydroxide (24.0 g,
600 mmol) in distilled water (225 mL), and
1,2-dichloroethane (225 mL) were heated to reflux for 48 h.
The organic phase was separated, dried with magnesium sul-
fate, and concentrated under reduced pressure to produce a
translucent yellow oil. This crude product was subsequently
purified by vacuum distillation to give the title compound as
a colourless oil (35.6 g, 76%). The compound showed bp
1
2,3-Bis(triphenylmethylthioacetylamino)propanoic acid (4)
To 1.0 g (1.33 mmol) of 3 in a 1:1 mixture of THF and
water (80 mL), 100 mg (2.5 mmol) of NaOH was added. Af-
ter the mixture was heated to reflux for 3 h under an atmo-
sphere of nitrogen, the solution was cooled, acidified to
100–102°C @ 12 mmHg; H NMR (CDCl3) (200 MHz)
δ: 7.30 (m, 5H, H-aryl), 4.23 (t, 2H, OCH2), 3.81 (t, 2H,
J = 5.9, CH2Cl); 13C NMR (CDCl3) (50 MHz) δ: 159.8
(C- ipso), 131.0 (C-meta), 122.5 (C-para), 118.3 (C-ortho),
67.86 (OCH2), 41.86 (CH2Cl).
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Bell et al.
151
1-[4-(2-Chloroethoxy)phenyl]-2-phenyl-1-butanone (6)
The procedure developed by McCague was used (10).
1-[4-(2-Chloroethoxy)phenyl]-1-[2-(O-(tert-butyldimethyl-
silyl)ethyl)phenyl]-2-phenyl but-1-ene (10)
1-Chloro-2-phenoxyethane
(21.8
g,
140
mmol),
Compound 9 was dissolved in freshly distilled pyridine
(10 mL) and cooled to –10°C; thionyl chloride (788 µL,
10.8 mmol) was added and the mixture stirred under argon
for 3 h. The yellow–orange coloured solution was diluted
cautiously with distilled water (20 mL) and extracted with
diethyl ether (4 × 40 mL). The organic layers were com-
bined and evaporated to dryness. The product was isolated
by radial chromatography (10:1 low boiling petroleum
ether/ether). The compound, a yellow oil (1.18 g, 64%),
showed TLC: Rf = 0.72 (10:90 v/v ether/petroleum ether);
1H NMR (CDCl3) (200 MHz) δ:7.102 (m, H-aryl), 6.500 (d,
2H, H-ortho ring B), 4.189 (t, J = 3.9, 2H, Z-isomer
OCH2CH2Cl), 4.042 (t, J = 3.8, 2H, E-isomer OCH2CH2Cl),
3.910 (m, 1H, SiOCH2), 3.769 (t, J = 3.9, 2H, Z-isomer
CH2Cl), 3.672 (t, J = 4.0, 2H, E-isomer CH2Cl), 3.449 (m,
TBSOCH2), 2.867 (t, J = 3.6, 2H, E-isomer CH2Ph), 2.787
(m, 1H, E-isomer CH2CH3), 2.686 (t, J = 4.9, 2H, E-isomer
CH2Ph), 2.560 (m, 1H, Z-isomer CH2CH3), 2.276 (m, 2H,
Z-isomer CH2CH3), 1.007 (t, J = 4.9, CH3), 0.814 (m,
SiC(CH3)3), 0.02 (s, Si-CH3); 13C NMR (CDCl3) (50 MHz)
δ: 156.77, 156.06, 142.77, 142.53, 142.16, 141.89, 141.74,
137.55, 136.95, 135.97, 134.77, 131.71, 131.55, 130.65,
130.42, 130.01, 129.73, 129.46, 128.96, 128.26, 127.97,
127.47, 126.95, 126.20, 126.0, 125.36, 120.05, 117.0,
114.18, 113.505 (C-aryl), 67.93 (Z-isomer OCH2CH2Cl),
67.70 (E-isomer OCH2CH2Cl), 63.43 (E-isomer SiOCH2),
63.20 (Z-isomer SiOCH2), 41.76 (CH2Cl), 36.72 (E-isomer
CH2Ph), 36.43 (Z-isomer CH2Ph), 29.51 (CH2CH3), 25.93
(SiC(CH3)3), 18.31 (SiCH3), 13.80 (Z-isomer CH2CH3),
12.93 (E-isomer CH2CH3); MS (NH3 DCI) m/z (RI%): 538
(100) (M + NH3), 520 (80) (M), 406 (85) (M – TBS + H).
(±)-2-phenylbutyric acid (20.2 g, 120 mmol), and
trifluoroacetic anhydride (27.3 g, 130 mmol) were mixed
and stirred magnetically at 20°C for 70 h. The reaction mix-
ture was then poured slowly into distilled water (150 mL) to
give a pink solid which was collected and recrystallized
from ethanol to give colourless crystals (28.8 g, 79%). The
compound showed mp 65–70°C; TLC: Rf = 0.79 (100%
CH2Cl2); 1H NMR (CDCl3) (200 MHz) δ: 7.98–6.85 (m,
9H, H-aryl), 4.39 (t, 1H, J = 7.3, PhCH), 4.24 (t, 2H,
OCH2), 3.80 (t, 2H, J = 5.8, CH2Cl), 2.02 (m, 2H, CH2CH3),
0.89 (t, 3H, J = 7.4, CH3); 13C NMR (CDCl3) (50 MHz) δ:
198.07
(C(O)),
162.11–107.38
(C-aryl),
67.53
(CHPhCH2CH3), 55.17 (OCH2), 41.39 (CH2Cl), 26.48
(CH2), 12.15 (CH3).
2-(2-Bromophenyl)-O-(tert-butyldimethylsilyl)ethan-2-ol (8)
The procedure developed by Corey and Venkateswarlu
(13) was used. 2-Bromophenethyl alcohol (2.0 g, 9.95 mmol)
and imidazole (1.02 g, 14.9 mmol) were dissolved in di-
chloromethane (30 mL) under nitrogen and cooled over ice
before tert-butyldimethylsilyl chloride (2.25 g, 14.9 mmol)
was added. After 8 h the reaction mixture was filtered and
the residue washed with dichloromethane (25 mL). The fil-
trate was extracted with distilled water (3 × 30 mL), concen-
trated to 1 mL, and passed down a silica column (petroleum
ether – dichloromethane). The first band to elute from the
column was collected, evaporated to dryness, and dried un-
der high vacuum until the odour of the silicon starting mate-
rial could no longer be detected (2–3 h). The product, a
colourless oil (2.6 g, 83%), showed TLC: Rf = 0.66 (50:50
v/v CH2Cl2/hexanes); 1H NMR (CDCl3) (200 MHz) δ:
7.58–6.99 (m, 4H, H-aryl), 3.85 (t, 2H, J = 8.8, CH2O), 2.99
(t, 2H, PhCH2), 0.90 (s, 9H, SiC(CH3)3), 0.03 (s, 6H,
Si(CH3)2); 13C NMR (CDCl3) (50 MHz) δ: 138.29 (C-2),
131.7, 132.6 (C-3, C-6), 127.8, 127.1, (C-4, C-5), 124.56
(C-ipso i.e., C-1), 62.40 (CH2O), 53.27 (SiC(CH3)3), 39.59
(PhCH2), 25.89 (SiC(CH3)3), 18.22 (Si(CH3)2); MS (NH3
DCI) m/z (RI%): 334 (100) (M + 2H+ + NH3), 332 (89) (M
+ NH3), 331 (20) (M + NH3 – H+), 317 (100) (M + 2H+),
315 (90) (M).
1-[4-(2-Chloroethoxy)phenyl]-1-[2-(hydroxyethyl)phenyl]-2-
phenyl but-1-ene (11)
The procedure developed by Corey and Venkateswarlu
(13) was used. To compound 10 (800 mg, 1.54 mmol) in
10 mL of THF, tetrabutylammonium fluoride (5.07 mL,
1.0 M solution in THF) was added. The reaction was al-
lowed to stir for 24 h before dilution with distilled water
(20 mL) and extraction with diethyl ether (4 × 25 mL). The
organic layer was concentrated to a volume of 2 mL and the
product isolated by radial chromatography (hexanes–di-
chloromethane). The title compound (600 mg, 96%), an oil,
1-[4-(2-Chloroethoxy)phenyl]-1-[2-(O-(tert-butyldimethyl-
silyl)ethyl)phenyl]-2-phenyl butan-1-ol (9)
1
showed TLC: Rf = 0.15 (100% CH2Cl2); H NMR (CDCl3)
Compound 8 (2.02 g, 6.41 mmol) was dissolved in 5 mL
of dry THF in a flame-dried flask under an argon atmo-
sphere and cooled to –78°C. When n-butyllithium (4.0 mL,
1.6 M solution in hexanes) was added via syringe the solu-
tion became heterogeneous; it was left to stir for an addi-
tional 20 min. After the addition of compound 6 (1.09 g,
3.6 mmol in 5 mL dry THF) the solution cleared. The solu-
tion was allowed to gradually warm to room temperature
and after 12 h the reaction was complete. Distilled water
(50 mL) was added slowly and the solution extracted with
ether (3 × 50 mL). The organic layers were combined, dried
over sodium sulfate, filtered, and evaporated to dryness. The
resulting oil was used without further purification or charac-
terization.
(200 MHz) δ: 7.20 (m, H-aryl), 6.520 (d, 2H, H-ortho ring
B), 4.143 (t, J = 5.9, Z-isomer, OCH2CH2Cl), 3.996 (t, J =
5.9, 2H, E-isomer OCH2CH2Cl), 3.725 (t, J = 5.8, 2H, Z-iso-
mer CH2Cl), 3.629 (t, J = 5.9, 2H, E-isomer CH2Cl), 3.425
(m, E/Z, CH2OH), 2.711, 2.200 (m, overlap, CH2Ph,
CH2CH3), 0.954 (t, J = 7.5, 3H, Z-isomer CH3), 0.769 (t, J =
7.4, 3H, E-isomer CH3); 13C NMR (CDCl3) (50 MHz) δ:
156.10, 156.06, 142.98, 142.69, 142.05, 141.70, 136.65,
136.37, 136.15, 135.86, 134.60, 132.01, 131.50, 130.35,
130.24, 129.65, 128.87, 127.98, 127.52, 127.22, 126.50,
126.26, 126.06, 125.64, 114.24, 113.52 (C-aryl), 67.93
(Z-isomer OCH2CH2Cl), 67.67 (E-isomer OCH2CH2Cl),
62.63 (E-isomer CH2OH), 62.41 (Z-isomer CH2OH), 41.79
(CH2Cl), 36.47 (E-isomer PhCH2), 36.14 (Z-isomer PhCH2),
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Can. J. Chem. Vol. 77, 1999
29.49 (E-isomer CH2CH3), 28.04 (Z-isomer CH2CH3), 13.77
(Z-isomer CH3), 12.92 (E-isomer CH3).
J = 7.0, 2H, CH2N3), 2.801, 2.620, 2.553 (m, overlap,
OCH2CH2Ph and CH2CH3), 2.192 (t, J = 7.6, 2H, CH2C(O)),
1.511, 1.288 (m, CH2), 0.960 (t, J = 7.4, 3H, CH3); 13C
NMR (CDCl3) (125 MHz) δ: 173.60 (COOR), 142.92, 142.01,
137.18, 135.65, 131.95, 130.39, 129.71, 128.95, 127.54,
126.52, 126.12, 125.80, 114.35 (C-aryl), 68.05 (OCH2CH2Cl),
63.72 (OCH2CH2Ph), 51.48 (CH2N3), 41.83 (CH2Cl), 34.33
(CH2OC(O)), 32.05 (OCH2CH2Ph), 29.45, 29.25, 29.13,
28.82 (CH2), 26.70 (CH2CH3), 24.95 (CH2), 13.79 (CH3).
12-Azido-dodecanoic acid
Sodium azide (4.7 g, 72.3 mmol) was added to a solution
of 12-bromododecanoic acid (2.0 g, 7.16 mmol) in DMF
(45 mL). After heating at 80°C for 12 h, the reaction mix-
ture was cooled to room temperature and poured into dis-
tilled water (100 mL). The solution was extracted with ether
(2 × 70 mL) and the organic fractions pooled and evaporated
in vacuo. The resulting yellow oil was diluted with a 3:1
mixture of water/brine (10 mL) and refrigerated overnight.
The resulting colourless precipitate was collected by filtra-
tion, washed with cold water (30 mL), and dried in air. The
compound (1.56 g, 90%) showed 1H NMR (CDCl3)
(200 MHz) δ: 3.320 (t, J = 6.8, 2H, CH2-N3), 2.313 (t, J =
7.4, 2H, CH2COOH), 1.570 (m, 4H, CH2), 1.257 (m, 18H,
CH2); 13C NMR (CDCl3) (50 MHz) δ: 180.04 (COOH),
51.45 (CH2-N3), 34.15 (CH2COOH), 29.40, 29.18, 29.09,
29.02, 28.8, 26.67, 24.68 (CH2); MS(ES) m/z (RI%): 241.4
(18) (M), 240.4 (100) (M – H).
1-[4-(2-Dimethylaminoethoxy)phenyl]-1-{2-[(12-
azidododecanoyl)oxyethyl]phenyl}-2-phenyl but-1-ene (13)
The procedure developed by McCague (10) was used. In a
round-bottom flask fitted with a dry ice condenser, com-
pound 12 (150 mg, 0.235 mmol) was dissolved in dimethyl-
amine (20 mL, 5.6 M solution in ethanol) and the mixture
was heated to reflux for 2 days. The solution was evaporated
to dryness, the residue dissolved in DCM (2 mL), and the ti-
tle compound isolated by centrifugal chromatography
(CHCl3–MeOH). The title compound, a yellow oil (76 mg,
1
50%), showed H NMR (CDCl3) (500 MHz) δ: 7.298 (m,
H-aryl), 6.934 (d, J = 8.9, 2H, H-meta ring A), 6.512 (d, 2H,
H-ortho, ring A), 4.110 (m, OCH2CH2Ph), 3.916 (overlap, t,
J = 6.0, OCH2CH2NMe2, and m, OCH2CH2Ph), 3.242 (t, J =
6.8, 2H, CH2N3), 2.713 (m, OCH2CH2Ph), 2.644 (t, J = 5.7,
2H, CH2NMe2), 2.210 (m, overlap, CH2CH3, CH2COOR,
NCH3), 1.331 (m, (CH2)n), 0.813 (t, J = 7.2, 3H, CH2CH3);
13C NMR (CDCl3) (125 MHz) δ: 173.59 (COOR), 156.69,
142.72, 141.88, 141.74, 136.57, 135.76, 133.68, 131.33,
130.21, 130.11, 129.65, 128.89, 127.90, 127.46, 127.07,
126.34, 126.14, 114.05 (C-aryl), 65.52 (OCH2CH2NMe2),
63.67 (OCH2CH2Ph), 58.13 (CH2N), 51.38 (CH2N3), 45.73
(NCH3), 34.25 (CH2COOR), 32.42 (OCH2CH2Ph), 29.37,
29.18, 29.05 ((CH2)n), 28.75 (CH2CH3), 26.63, 24.88
((CH2)n), 12.90 (CH2CH3); MS (HRDEI): obs: 638.4190,
calcd.: 638.4196.
1-[4-(2-Chloroethoxy)phenyl]-1-[2-[(12-
azidododecanoyl)oxyethyl)phenyl]-2-phenyl but-1-ene (12)
12-Azido-dodecanoic acid (500 mg, 2.07 mmol) was dis-
solved in thionyl chloride (8 mL) and heated to reflux under
nitrogen for 1 h. Residual thionyl chloride was evaporated in
vacuo and the residue dissolved in dry dichloromethane
(25 mL), which was subsequently evaporated. The oily resi-
due was redissolved in dry dichloromethane (20 mL) and
compound 11 (766 mg, 1.89 mmol) in dry dichloromethane
(5 mL) was added. The solution was heated to reflux for
12 h before the slow addition of 10% Na2CO3 (20 mL). The
solution was extracted with chloroform (2 × 50 mL), and the
organic layers were pooled, concentrated to 2 mL, and the
product, a yellow oil (766 mg, 64%), isolated by radial chro-
matography (petroleum ether – ether). Samples of pure E-12
and pure Z-12 can be isolated by using a new chromatatron
plate (activated with petroleum ether), a very gradual gradi-
ent of 100% petroleum ether up to 10% ether and collecting
small aliquots as the major product band elutes from the
chromatatron. The compound showed MS (HRDEI): obs:
1-[4-(2-Dimethylaminoethoxy)phenyl]-1-{2-[(12-
aminododecanoyl)oxyethyl]phenyl]-2-phenyl but-1-ene (14)
To compound 13 (69 mg, 0.108 mmol) in THF (1 mL),
triphenylphosphine (29 mg, 0.110 mmol) followed by dis-
tilled water (3.0 µL) were added. The reaction was allowed
to stir for 24 h whereupon an additional aliquot of triphenyl-
phosphine (29 mg, 0.110 mmol) and water (3.0 µL) were
added. After an additional 24 h the solution was evaporated
to dryness, diluted with chloroform (1 mL), and the title
compound isolated by centrifugal chromatography (16 mg,
1
629.33695, calcd.: 629.3384. E-Isomer: H NMR (CDCl3)
(500 MHz) δ: 7.280 (m, H-aryl), 6.764 (d, J = 9.3, 2H,
H-meta- ring B), 6.512 (d, 2H, H-ortho- ring B), 4.117 (m,
1H, OCH2CH2Ph), 4.063 (m, 2H, OCH2CH2Cl), 3.914 (m,
1H, OCH2CH2Ph), 3.694 (t, 2H, J = 6.0, CH2Cl), 3.233 (t,
2H, CH2N3), 2.734 (m, 2H, OCH2CH2Ph), 2.325 (m, 1H,
CH2CH3), 2.224 (t, J = 6.2, 2H, CH2C(O)), 2.211 (m, 1H,
CH2CH3), 1.564, 1.344, 1.245 (m, CH2), 0.810 (t, J = 7.4,
3H, CH3); 13C NMR (CDCl3) (125 MHz) δ: 173.61 (COOR),
156.13, 142.68, 142.28, 141.76, 136.50, 135.82, 134.48, 131.53,
130.28, 130.20, 129.70, 128.00, 127.20, 126.44, 126.28,
113.60 (C-aryl), 67.78 (OCH2CH2Cl), 63.71 (OCH2CH2Ph),
51.48 (CH2N3), 41.78 (CH2Cl), 34.32 (CH2OC(O)), 32.48
OCH2CH2Ph), 29.42, 29.38, 29.23, 29.10 (CH2), 28.82
1
25%). The compound showed H NMR (CDCl3) (500 MHz)
δ: 7.230 (m, H-aryl), 6.691 (d, J = 8.8, 2H, H-meta ring A),
6.488 (d, 2H, H-ortho, ring A), 4.036 (m, OCH2CH2Ph),
3.832 (overlap, t, J = 5.8, OCH2CH2NMe2, and m,
OCH2CH2Ph), 2.637 (m, overlap, CH2NH2, OCH2CH2Ph,
CH2NMe2), 2.197 (m, CH2CH3, CH2COOR, NCH3), 1.492,
1.353, 1.182 (m, (CH2)n), 0.743 (t, J = 7.2, 3H, CH2CH3);
13C NMR (CDCl3) (125 MHz) δ: 173.64 (COOR), 156.73,
142.72, 141.87, 141.76, 136.58 135.77, 133.66, 131.33,
130.22, 130.22, 130.11, 129.66, 128.25, 127.91, 127.07,
126.34, 126.14, 113.34 (C-aryl), 65.60 (OCH2CH2NMe2),
63.68 (OCH2CH2Ph), 58.18 (CH2N), 45.78 (NCH3), 42.08
(H2NCH2), 34.27 (CH2COOR), 33.69 ((CH2)n), 32.42
1
(CH2CH3), 26.69, 24.94 (CH2), 12.90 (CH3). Z-Isomer: H
NMR (CDCl3) (500 MHz) δ: 7.00 (m, H-aryl), 4.166 (t, J =
6.0, 2H, OCH2CH2Cl), 3.816 (m, OCH2CH2Ph), 3.746 (t, J
= 6.0, 2H, OCH2CH2Cl), 3.652 (m, OCH2CH2Ph), 3.191 (t,
© 1999 NRC Canada

Bell et al.
153
(OCH2CH2Ph) 29.44, 29.21((CH2)n), 29.06 (CH2CH3),
26.82, 24.89 ((CH2)n), 12.91 (CH2CH3); MS (NH3 DCI) m/z
(RI%): 613 (100) (M + 1), 541 (14) (M – CH2CH2NMe2).
(OCH2CH2Ph), 30.81, 29.42, 29.18, 26.79 ((CH2)n), 29.03
(CH2CH3), 26.79, 24.86 ((CH2)n), 13.05 (Z-CH2CH3); 12.85
(E-CH2CH3).
1-[4-(2-Dimethylaminoethoxy)phenyl]-1-{2-[(12-((2,3-bistri-
phenylmethylthioacetylamino)propanamide)dodecanoyl)oxy-
ethyl]phenyl}-2-phenyl but-1-ene (15)
1-[4-(2-Dimethylaminoethoxy)phenyl]-1-{2-[(12-((2,3-bistri-
phenylmethylthioacetylamino)propanamido)dodecanoyl-
oxy)ethyl]phenyl}-2-phenyl but-1-ene (15)
A sample of 300 mg (0.227 mmol) of 17 was dissolved in
a 5.6 M solution of dimethylamine in ethanol (5 mL) in a
round-bottom flask that was fitted with a dry-ice condenser.
The solution was heated to reflux for 24 h when, after cool-
ing, the solvent was evaporated in vacuo. The product, a
dark oily semi-solid (181 mg, 60%), was isolated by radial
chromatography (chloroform–methanol). The compound
Compound 14 (16 mg, 0.026 mmol) was dissolved in
DCM (10 mL) and triethylamine was added (1 mL), fol-
lowed by compound 4 (20 mg, 0.027 mmol). To this well
stirred solution, EDC (19 mg, 0.099 mmol) was added
slowly. The reaction mixture was stirred for 48 h before di-
lution with DCM (10 mL) and extraction with brine (3 ×
10 mL). The organic phase was concentrated to 1 mL and an
impure fraction of the title compound isolated by radial
chromatography (CHCl3–MeOH). This fraction was concen-
trated to 0.5 mL, and a pure sample of the title compound
isolated by preparative TLC (silica). The title compound was
a yellow oil (9 mg, 26%).
1
showed TLC: Rf = 0.36 (10% CH3OH–CH2Cl2); H NMR
(CDCl3) (500 MHz) δ: 7.250 (m, H-aryl), 6.735 (d, J = 8.9,
H, H-meta ring A), 6.505 (d, 2H, H-ortho, ring A), 4.122
(m, overlap, OCH2CH2Ph,CHCH2), 4.055 (m, Z-OCH2CH2N),
3.926 (m, overlap, OCH2CH2Ph), 3.896 (t, J = 5.9,
E-OCH2CH2N), 3.194 (m, CHCH2), 2.985 (s, 4H, CH2S),
2.718 (m, overlap, Z-OCH2CH2N and OCH2CH2Ph), 2.625
(t, J = 5.8, 2H, E-OCH2CH2N), 2.325 (s, Z-NCH3), 2.267
(E-NCH3), 2.211 (m, overlap, E/Z CH2CH3, CH2COOR),
1.540, 1.407, 1.213 (m, (CH2)n), 0.994 (t, J = 7.4, 3H, Z =
CH2CH3), 0.797 (t, J = 7.5, 3H, CH2CH3); 13C NMR
(CDCl3) (125 MHz) δ: 173.63 (ester C(O)), 169.86, 169.21,
168.96 (amide C(O)), 156.73, 143.87, 142.75, 141.92,
136.60, 135.82, 133.72, 131.37, 130.26, 129.69, 129.50,
129.42, 128.94, 128.11, 126.98, 126.38, 126.19, 114.10,
113.39, (C-aryl), 67.73 (CPh3), 65.57 (OCH2CH2N), 63.70
(OCH2CH2Ph), 58.18 (CH2N), 54.55 (NHCH2), 45.80
(NCH3), 42.07 (CHCH2), 39.64 (CHCH2), 36.10, 35.79
(SCH2), 34.31 (CH2COOR), 32.45 (OCH2CH2Ph), 29.48,
29.26 ((CH2)n), 29.03 (CH2CH3), 26.86, 24.94 ((CH2)n),
13.05 (Z-CH2CH3); 12.95 (E-CH2CH3). C, H analysis: calcd.
for C85H94N4S2O6·2.5H2O: C 74.06, H 7.42%; obs.: C 74.18,
H 7.20%.
1-[4-(2-Chloroethoxy)phenyl]-1-{2-[(12-
aminododecanoyl)oxyethyl]phenyl}-2-phenyl but-1-ene (16)
Triphenylphosphine (326 mg, 1.24 mmol) was added to a
solution of compound 12 (710 mg, 1.13 mmol) in THF
(2 mL) and water (50 µL). The solution was stirred (pro-
tected from light) for 12 h before concentration of the sol-
vent under reduced pressure. The oily residue was dissolved
in chloroform (2 mL), and the product, a yellowish oil
(450 mg, 66%), was isolated by radial chromatography
(CHCl3–MeOH) and used immediately after isolation.
1-[4-(2-Chloroethoxy)phenyl]-1-[2-((12-((2,3-
bistriphenylmethylthioacetylamino)propanamide)dodecan-
oyl)oxyethyl)phenyl]-2-phenyl but-1-ene (17)
To a dichloromethane solution (10 mL) of compound 16
(180 mg, 0.298 mmol) and compound 4 (264 mg,
0.36 mmol), EDC (70 mg, 0.36 mmol) and triethylamine
(1 mL) were added. The mixture was allowed to stir for 48 h
whereupon the solvent was evaporated at reduced pressure,
the oily residue dissolved in chloroform (2 mL), and the
product isolated by radial chromatography (hexanes–chloro-
form). The compound, a yellow oil (300 mg, 76%), showed
1H NMR (CDCl3) (500 MHz) δ: 7.250 (m, H-aryl), 6.755
(d, J = 8.9, 2H, H-meta ring A), 6.491 (d, 2H, H-ortho, ring
A), 4.150 (t, J = 5.8, 2H, Z- OCH2CH2Cl), 4.118 (m, over-
lap, OCH2CH2Ph), 4.028 (t, J = 3.9, 2H, E-OCH2CH2Cl),
3.771 (m, overlap, CHCH2 and OCH2CH2Ph), 3.761 (t, J =
4.2, Z-OCH2CH2Cl), 3.665 (t, J = 5.8, 2H, E- OCH2CH2Cl),
3.181 (m, 2H, CHCH2), 2.971 (s, 4H, CH2S), 2.718 (m,
overlap, E/Z OCH2CH2Ph), 2.246 (m, overlap, E/Z
CH2CH3), 2.179 (t, J = 5.6, 2H, CH2COOR), 1.534, 1.385,
1.200 (m, (CH2)n), 0.988 (t, J = 7.5, 3H, Z-CH2CH3), 0.793
(t, J = 7.3, 3H, CH2CH3); 13C NMR (CDCl3) (125 MHz) δ:
173.54 (ester C(O)), 169.71, 169.08, 168.88 (amide C(O)),
156.00, 143.81, 142.78, 142.56, 142.15, 141.63, 136.39,
135.69, 134.32, 131.43, 130.21, 130.08, 129.60, 129.42,
129.35, 128.85, 128.02, 127.45, 127.12, 126.90, 126.36,
126.19, 125.71, 114.22, 113.46 (C-aryl), 83.14 (CPh3), 67.65
(Z-OCH2CH2Cl), 67.62 (E-OCH2CH2Cl), 63.61 (OCH2CH2Ph),
51.11 (CHCH2), 41.99 (Z-CH2Cl), 41.76 (E-CH2Cl), 39.55
(CHCH2), 36.04, 35.74 (SCH2), 34.22 (CH2COOR), 32.38
Using approach B, a 5:1 E:Z sample of compound 15 was
synthesized in 18 steps in reasonable yield. It is was also
discovered that the E and Z isomers of compound 12 could
be separated by radial chromatography. This work is an ex-
ample of a total synthesis of a biomolecule–chelate complex
for the purpose of developing a site-specific radioimaging
agent. Testing of compound 15 in tumour models remains
work in progress.
We acknowledge, with thanks, financial support of this
work by the Natural Sciences and Engineering Research
Council of Canada and the grant of an NSERC postgraduate
fellowship to J.F.V.
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© 1999 NRC Canada

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