Thioredoxin reductase and cancer cell growth inhibition by organotellurium compounds that could be selectively incorporated into tumor cells

Article abstract of DOI:10.1016/j.bmc.2003.08.021

The thioredoxins are small ubiquitous redox proteins with the conserved redox catalytic sequence-Trp-Cys-Gly-Pro-Cys-Lys, where the Cys residues undergo reversible NADPH dependent reduction by selenocysteine containing flavoprotein thioredoxin reductases. Thioredoxin expression is increased in several human primary cancers including lung, colon, cervix, liver, pancreatic, colorectal and squamous cell cancer. The thioredoxin/thioredoxin reductase pathway therefore provides an attractive target for cancer drug development. Organotellurium steroid, lipid, amino acid, nucleic base, and polyamine inhibitors were synthesized on the basis that they might be selectively or differentially incorporated into tumor cells. Some of the newly prepared classes of tellurium-based inhibitors (lipid-like compounds 3b and 3e, amino acid derivative 5b, nucleic base derivative 8b, and polyamine derivatives 14a and 14b) inhibited TrxR/Trx and cancer cell growth in culture with IC ₅₀ values in the low micromolar range.

Full text of DOI:10.1016/j.bmc.2003.08.021

Bioorganic & Medicinal Chemistry 11 (2003) 5091–5100
Thioredoxin Reductase and Cancer Cell Growth Inhibition by
Organotellurium Compounds that Could be Selectively
Incorporated into Tumor Cells
Lars Engman,a,* Nawaf Al-Maharik,a Michael McNaughton,a Anne Birminghamb
and Garth Powisb
aDepartment of Organic Chemistry, Institute of Chemistry, Uppsala University, PO Box 599, S-751 24, Uppsala, Sweden
bArizona Cancer Center, University of Arizona, Tucson, AZ 85724-5024, USA
Received 3 December 2002; accepted 21 August 2003
Abstract—The thioredoxins are small ubiquitous redox proteins with the conserved redox catalytic sequence-Trp-Cys-Gly-Pro-Cys-
Lys, where the Cys residues undergo reversible NADPH dependent reduction by selenocysteine containing flavoprotein thioredoxin
reductases. Thioredoxin expression is increased in several human primary cancers including lung, colon, cervix, liver, pancreatic,
colorectal and squamous cell cancer. The thioredoxin/thioredoxin reductase pathway therefore provides an attractive target for
cancer drug development. Organotellurium steroid, lipid, amino acid, nucleic base, and polyamine inhibitors were synthesized on
the basis that they might be selectively or differentially incorporated into tumor cells. Some of the newly prepared classes of tell-
urium-based inhibitors (lipid-like compounds 3b and 3e, amino acid derivative 5b, nucleic base derivative 8b, and polyamine deri-
vatives 14a and 14b) inhibited TrxR/Trx and cancer cell growth in culture with IC50 values in the low micromolar range.
# 2003 Elsevier Ltd. All rights reserved.
Introduction
mice.8 Trx-1 transfection of MCF-7 human breast can-
cer and HT-29 colon cancer cells stimulates tumor
growth.9 Trx-1 transfection of mouse WEHI7.2 lym-
phoma cells markedly inhibits both spontaneous and
drug induced apoptosis.10,11 Redox activity is essential
for the biological effects of Trx-1.12 Transfection of
cancer cells with a redox inactive mutant Trx-1 does not
transform cells, inhibits cell growth, potentiates apop-
tosis9,11 and blocks tumor formation by the cells in
immunodeficient scid mice.10 Proteins with activity
dependent on reduction by Trx-1 include the DNA
binding transcription factors NF-kB, AP-1, HIF-1a and
p53.2,11,13,14 The binding of Trx-1 also regulates the
activity of enzymes such as apoptosis signal regulating
kinase-1 (ASK1),15 and protein kinases C a,d,e,z.16
Thioredoxins (Trxs) are small ubiquitous redox proteins
with the conserved redox catalytic sequence -Trp-Cys-
Gly-Pro-Cys-Lys where the Cys residues undergo
reversible NADPH dependent reduction by selenocys-
teine containing flavoprotein thioredoxin reductases.1,2
There are two mammalian Trxs. Human Trx-1 is a 105
amino acid protein found in the cytoplasm and nucleus
of cancer cells.3,4 Trx-1 is also secreted by cells and
accumulates in growth media and in plasma.5,6 The
second thioredoxin, Trx-2, is found in the mitochon-
dria, its functions are unknown but it may protect
mitochondria against oxidative damage.7 Through thiol
disulfide exchange, reduced Trx-1 is able to catalyze the
selective reduction of protein Cys residues resulting in
alterations in their enzymatic and DNA binding prop-
erties. Trx-1 is a protooncogene and nuclear targeted
Trx-1 transforms mouse NIH 3T3 embryonic cells
allowing them to form tumors in immunodeficient
Trx-1 protein levels are significantly elevated in several
human primary cancers including gastric (50%), colon
(55%), pancreas (41%), hepatoma (52%), lung (50%)
and cervical cancer (75%).3,17À22 Human primary gas-
tric cancer shows a highly significant correlation
between elevated increased Trx-1 expression and
increased proliferation and inhibited apoptosis.3
Increased Trx-1 expression is a late event in colon
*Corresponding author. Tel.: +46-18-471-3784; fax: +46-18-471-
3818; e-mail: lars.engman@kemi.uu.se
0968-0896/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2003.08.021

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L. Engman et al. / Bioorg. Med. Chem. 11 (2003) 5091–5100
cancer, occurring in primary and metastatic disease but
not in colon polyps, and is an independent prognostic
factor for poor patient survival in colorectal cancer.23
the most versatile procedures for the synthesis of
unsymmetrical diorganotellurium compounds.27 The
required lithium organyl tellurolates can be readily
obtained by insertion of elemental tellurium into the
carbon–lithium bond of organolithiums, while the cor-
responding sodium tellurolates can be prepared by
reduction of ditellurides with NaBH4. Nucleophilic
substitution of bromide 1a or tosylate 1b with various
lithium- or sodium- organotellurolates was used for the
preparation of steroid derivatives 1c–1f. The materials
were found to oxidise quite rapidly to the corresponding
oxides when exposed to air.
The Trx-1 redox system provides an attractive target for
cancer drug development. Thioredoxin reductase
(TrxR) is a selenocysteine containing flavoenzyme that
catalyzes the reduction of oxidised thioredoxin. This
enzyme could therefore be used for regulating the
activity of the thioredoxin system. Previous studies of
organotellurium inhibitors of thioredoxin (Trx-1) indi-
cated that compounds with antioxidative capacity,
especially peroxide-decomposing ability, were the most
efficient.24 The compounds investigated also inhibited
the growth of human cancer cells in culture. However,
the poor solubility of these materials in water was a
restriction when administered to animals as antitumor
agents. For enhancing hydrophilicity, it was decided to
introduce sulfopropyl groups into this class of com-
pounds. Water soluble organotellurium compounds of
the diaryl telluride, alkyl aryl telluride and dialkyl tell-
uride type, were found to be the most efficient tellurium
based inhibitors of thioredoxin reductase ever tested.25
Some of the compounds inhibited the enzyme at sub-
micromolar levels. The compounds also inhibited the
growth of MCF-7 and HT-29 human cancer cells in
culture at the 5–10 mM level but their hydrophilicity
seemed to restrict cellular uptake. For obtaining more
useful compounds, we thought the next generation of
organotellurium compounds must also possess an addi-
tional quality in addition to thioredoxin reductase inhi-
biting activity, the ability to localize tumor cells. Thus,
various classes of compounds were synthesized on the
basis that they might become selectively or differentially
incorporated into tumor cells. Based on general knowl-
edge about biodelivery, molecular mimicry of a known
cellular constituent or metabolite can be employed for
delivery of organotelluriums to the targeted tumor cell.
As detailed in the following, tellurium containing ster-
oids, lipids, amino acids, nucleic bases, and polyamines
are candidates for such an approach. Provided their
capacity to inhibit thioredoxin reductase is similar to
that observed with compounds previously prepared,
they could be expected to possess superior antitumor
properties.
Tellura fatty-acids have already found use in biomedical
research. They were synthesized with g-emitting tell-
urium isotopes for organ-imaging purposes in nuclear
medicine and have been designed specifically for the
investigation of cardiac disorders.28 Scheme 1 outlines
the preparation of some organotellurium fatty acid
derivatives 3. Alkylation of in situ generated sodium
arenetellurolates with 1.1 equivof alkyl o-bromoalk-
anoates in EtOH resulted in the formation of com-
pounds 2 in 76–94% yields. Basic hydrolysis (LiOH in
MeOH/H2O) afforded compounds 3 in similarly good
yields.
Results and Discussion
Preparation of organotellurium compounds
Organotelluriums conjugated to steroids and lipids.
Receptor–LDL complexes are internalized by endocy-
tosis. The LDL is degraded to cholesterol by lysosomes,
and the receptor returns to the external cell wall.
Malignant cells are expected to use cholesterol at a
much higher rate than normal cells because of higher
replication rates, and therefore to have correspondingly
higher receptor turnover rates.26 This provides a basis
for cellular differentiation and the targeting of tumor
cells with organotellurium compounds if the cholesteryl
esters of the LDL core are replaced with tellurium con-
taining material. The alkylation of tellurolates is one of
Scheme 1. Reagents and conditions: (i) Br(CH2)nCO2R1, EtOH, rt;
(ii) LiOH, MeOH, H2O, rt, 20 h, 1 N HCl.

L. Engman et al. / Bioorg. Med. Chem. 11 (2003) 5091–5100
5093
Organotelluriums conjugated to amino acids. The accel-
erated rate of synthesis of proteins and amino acid
metabolites exhibited by a malignant cell, coupled with
the active transport mechanisms available for amino
acid accumulation within cells,29 provides a bioutiliza-
tion process that may allow organotelluriums to enter
tumor cells preferentially. Concerning tellurium analo-
gues of naturally occurring amino acids, most synthetic
work has been directed to the synthesis of tell-
uromethionine.30À32 However, in non-degassed aqueous
solution at pH 7.0, this material has only a half-life of
ca. 30 min.32 Therefore, for the evaluation of thio-
redoxin reductase inhibiting capacity, the corresponding
N-acetyl derivative seems more attractive from a prac-
tical point of view (t1=2 ca. 20 h). For preparation of
compounds 5, N-acetyl-a-aminobutyrolactone (4) was
treated with 1.1 equivof various lithium organotellur-
olates in THF in the presence of tetra-
methylethylenediamine (TMEDA). The desired lithium
carboxylates 5a–c were isolated in 82, 71 and 92%
yield, respectively (Scheme 2). Attempts to remove the
N-protecting group under various acidic conditions
were unsuccessful (tellurium extrusion). Unfortunately,
the enantioselective enzymatic deacylation of 5a using
aminoacylase-based procedures also failed.32
route to arenetellurenyluracils (8) was used (Scheme 3):
Lithiation of 5-bromo-2,4-(bis-benzyloxy)pyrimidine
(6), followed by addition of diphenyl ditelluride, bis(4-
methoxyphenyl) ditelluride and bis(4-N,N-dimethylami-
nophenyl) ditelluride (1.5 equiv), respectively, afforded
compounds 7a, 7b and 7c in 72, 68 and 63% isolated
yield. The protecting benzyl groups were then removed
by exposure to trimethylsilyl iodide (2.4 equiv) in dry
CH2Cl2 at room temperature to furnish the desired
compounds 8a–c in 70–78% yield.
Organotelluriums conjugated to polyamines. Almost all
cells contain substantial amounts of at least one of the
polyamines putrescine, spermidine and spermine. Poly-
amines are required for the optimum growth and repli-
cation of various cell types and are present in higher
concentrations in rapidly proliferating cells.34 Poly-
amine depletion has growth inhibitory effects.35 Meta-
bolism studies with labelled polyamines in vivo has
shown that they can be taken up from the circulation. It
is also well established that tissues with a high demand
for polyamines such as prostate, tumors or normal but
rapidly dividing cells are accumulating polyamines in
increasing amounts with a specific uptake system.
Incorporation of tumoricidal agents into the polyamine
scaffold has previously produced more active com-
pounds than the parent chemotherapeutic agent.36À39
On the basis of these observations we decided to
prepare tellurium containing polyamines.
Organotelluriums conjugated to nucleic bases. As com-
pared with normal cells, malignant cells show an
increased rate of mitosis.33 This would lead to enhanced
uptake, accumulation and retention of nucleic acids,
nucleosides and nucleotides. Concerning the prepara-
tion of tellurium containing pyrimidines and purines
derivatives, there are only sporadic reports in the litera-
ture. In analogy with the preparation of other organo-
chalcogen derivatives of pyrimidines,33 the following
The hydrochloride 11 was prepared by the reaction
sequence shown in Scheme 4. Bis-O-o-bromoalkylation
of bis(4-hydroxyphenyl)telluride (9) with an excess of
1,4-dibromobutane (2.5 equiv) in dry acetone in the
presence of anhydrous K2CO3 furnished telluride 10 in
45% yield. Changing the solvent to DMF, acetonitrile
or t-butanol and varying the base (NaOH, NaH or
t-BuOK) did not cause any improvement in yield. Bis-
amination of 10 with an excess of 40% aqueous of
HNMe2 in EtOH, followed by addition of HCl furnished
bis-hydrochloride 11 in excellent yield.
The synthesis of tellurium containing spermidine analo-
gues 14 from N1,N10-bis-phthalimidyl spermidine 1240 is
outlined in Scheme 5. The most commonly used procedure
Scheme 2. Reagents and conditions: (i) TMEDA, THF, 4 h, rt.
Scheme 3. Reagents and conditions: (i) n-BuLi, THF, À78 ꢀC; (ii) ArTeTeAr, À78 ꢀC, 2 h; (iii) trimethylsilyl iodide, CH2Cl2.
Scheme 4. Reagents and conditions: (i) K2CO3, 1.4-dibromobutane, acetone, 20 h, reflux; (ii) 40% aq HNMe2, THF, 8 h, rt; (iii) 1 M HCl, rt, 2 h.

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L. Engman et al. / Bioorg. Med. Chem. 11 (2003) 5091–5100
Scheme 5. Reagents and conditions: (i) N-carbethoxyphthalimide, CH2Cl2, rt, 2 h; (ii) in situ prepared ArTe(CH2)nCOOCOO-i-Bu, CH2Cl2, 20 h;
(iii) N2H4, EtOH, 20 h, rt, 2 h.
for amide formation from carboxylic acids and amines
involves in situ formation of acid chloride followed by
addition of the amine. However, due to partial extru-
sion of tellurium, this methodology proved to be unsui-
table in our case. Instead, spermidine derivatives 13
were obtained via treatment of acids 3a, 3d and 3f,
respectively, with i-butyl chloroformate and then pro-
tected spermidine 12. Final removal of phthaloyl groups
using hydrazine in ethanol afforded compounds 14a–c.
(3) proved to be slightly more effective inhibitors. 5-
Phenyltellurenylvaleric acid (3b) inhibited TrxR/Trx
with an IC50 value of 14.6 mM and MCF-7 cell growth
with an IC50 value of 5.6 mM. The more lipid-like com-
pound 3e inhibited TrxR with an IC50 value of 1.0 mM,
but its cell-killing properties were not impressive
(IC50=16.4 mM). Based on the few examples where the
effect of a tellurium containing carboxylic acid (3) and
the corresponding methyl ester (2) could be made, it
seems that the acid is the more efficient inhibitor. Among
the three tellurium derivatives of amino acids (5) tested,
the aryltelluro derivative 5b, carrying an electron donat-
ing dimethylamino group, turned out to be an excellent
inhibitor of TrxR (IC50=0.42 mM). Again, the good
enzyme inhibiting capacity was not quite reflected in the
ability to kill MCF-7 cells (IC50=10.6 mM). Among tell-
urium-containing uracils (8) prepared, the aryltelluro
derivative 8b, carrying a strongly electron donating aryl
substituent, turned out to be a good inhibitor of TrxR
(IC50=2.6 mM). Compound 8c was a similarly good
inhibitor in the combined TrxR/Trx assay
(IC50=2.1 mM). However, none of the uracils prepared
showed any notable capacity to inhibit growth of cancer
cells (IC50 >14 mM). The tellurium containing diamine
derivative 11, as a free base or as a bis-hydrochloride,
was a poor inhibitor of TrxR/Trx. In contrast, spermi-
dine derivatives 14a and 14b were some of the best orga-
notellurium inhibitors of TrxR ever reported (IC50=1.8
and 0.2 mM). For 14a, the inhibiting effect was also lar-
gely reflected in the cell-growth assay (IC50=3.8 mM).
TrxR and cancer cell growth inhibition
TrxR activity was measured as the increase in absor-
bance at 405 nm which occurs as post reaction dithio-
nitrobenzoic acid (DTNB) is reduced by thiols produced
in an incubation containing Trx, TrxR, NADPH, insu-
lin and the inhibitor (Table 1: TrxR/Trx-activity). This
assay reflects the combined effects of the inhibition of
Trx and TrxR. For most of the inhibitors tested, TrxR
activity was also measured in incubations of DTNB,
TrxR, NADPH and inhibitor and measured as the
initial increase in absorbance at 405 nm (Table 1: TrxR-
activity). This assay reflects the inhibition of TrxR only.
With some exceptions (vide infra), the IC50 values
(concentrations required to inhibit thionitrobenzoate
formation by 50%) obtained using the two methods
were similar.
For most of the compounds, the effect on growth of
MCF-7 breast cancer cells in culture was also studied.
Inhibition data expressed as IC50 values (concentration
required to inhibit cell growth by 50% of that observed
in a control incubation) are shown in Table 1.
Organotellurium inhibitor 8c performed much better in
the combined TrxR/Trx-assay than in the TrxR-assay.
This may indicate inhibition of Trx rather than TrxR.
Some of the inhibitors investigated (compounds 3e, 5b,
8b, 14a and 14b) turned out to be significantly poorer
inhibitors in the combined TrxR/Trx-assay than in the
TrxR-assay. This unusual result is difficult to rationalize
but it could indicate some interaction of the organo-
tellurium inhibitor with Trx outside the active-site
cysteine residue.
Organotellurium steroid compounds (cholesterol deri-
vatives 1c–1f) turned out to be poor inhibitors
(IC50>25 mM) in the TrxR/Trx and TrxR assays. Their
cell-killing capacity was therefore not assessed. The
observed reactivity of these materials towards air may in
part explain their poor performance. Some of the
organotellurium derivatives of fatty acids (2) or esters

L. Engman et al. / Bioorg. Med. Chem. 11 (2003) 5091–5100
5095
Table 1. Inhibition of thioredoxin reductase and cancer cell growth by organotellurium compounds
Structure
Compd
Inhibition
TrxR/Trxa IC50 (mM)
TrxRb IC50 (mM)
MCF-7c IC50 (mM)
1c R=a-TePh
d R=b-TePh
e R=a-Te-n-Bu
f R=b-C6H4-p-NMe2
34.6
26.6
34.6
>50
>50
>50
—
—
—
—
—
>25
2b X=H n=4
2c X=H n=11
19.9
—
—
2d X=NMe2 n=4
2e X=NMe2 n=11
24.5
>25
—
—
—
—
3b X=H n=4
3c X=H n=11
3d X=NMe2 n=4
3e X=NMe2 n=11
14.6
>50
17.4
9.4
—
>50
—
5.6
—
>50
16.4
1
5a R=Ph
b R=C6H4-p-NMe2
c R=n-Bu
10.8
>20
5.8
13.8
0.42
9.8
7.8
10.6
>50
8a Ar=Ph
b Ar=C6H4-p-NMe2
c Ar=C6H4-p-OMe
20.6
12.6
2.1
—
2.6
22.4
—
>50
14.2
11 (free base)
31.6
26.7
—
—
—
—
11
14a Ar=Ph n=3
b Ar=C6H4-p-NMe2
n=4
c Ar=C6H4-p-OMe
n=3
8.8
10
1.8
0.2
3.8
10.8
10.4
>20
10.6
aInhibition of thioredoxin reductase in the presence of thioredoxin and insulin.
bInhibition of thioredoxin reductase.
cInhibition of growth of MCF-7 breast cancer cells in culture.
Among the amino acid, nitrogen base and polyamine
classes of tellurium containing inhibitors, it seems that
the compounds carrying a strongly electron donating
substituent in the aryltelluro moiety (dimethylamino
group) show better inhibition characteristics than the
corresponding phenyltelluro derivatives (compounds
5b/5a, 8b/8a, and 14b/14a). This could indicate that the
nucleophilicity/one-electron donating capacity of tell-
urium in the compounds tested could be critical for their
TrxR and cell growth inhibiting capacity. Whether this
is an antioxidative effect, (such as peroxide decomposi-
tion via nucleophilic attack on organic hydroperoxides
or chain-breaking donating activity via one-electron
donation to peroxyl radicals) or if it involves nucleo-
philic attack elsewhere (e.g., on some electrophilic dis-
ulfide bonds) is difficult to say.
structures will be subject to further elaboration and
carried on to in vivo testing.
Experimental
TrxR/Trx-assay
Thioredoxin reductase/thioredoxin-dependent insulin
reducing activity was measured in an incubation with a
final volume of 60 mL containing 100 mM HEPES buffer,
pH 7.2, 5 mM EDTA (HE buffer), 1 mM NADPH, 1.0 mM
human placental thioredoxin reductase, 0.8mM thior-
edoxin, 2.5 mg/mL bovine insulin and inhibitor. Incu-
bations were for 30 min at 37 ꢀC in flat-bottom 96-well
microtiter plates. The reaction was stopped by the addition
of 50 mL of 6M guanidine-HCl, 50mM Tris, pH 8.0, and
10 mM DTNB, and the absorbance measured at 405 nM.
In conclusion, some of the newly prepared classes of
tellurium-based inhibitors with a potential to be selec-
tively incorporated into tumor cells (amino acid, nitro-
gen base and polyamine compounds) show promising
inhibition of TrxR and growth of MCF-7 cells in cul-
ture (IC50 values in the low micromolar range). These
TrxR-assay
Assays of TrxR were carried out in flat-bottom 96-well
microtiter plates. TrxR activity was measured in a final

5096
L. Engman et al. / Bioorg. Med. Chem. 11 (2003) 5091–5100
incubation volume of 60 mL containing HE buffer,
10 mM DTNB, 1.0 mM TrxR and 1 mM NADPH and
inhibitor. Compounds were diluted in HE buffer and
added to the wells as 20-mL aliquots, and TrxR was then
added, also as 20-mL aliquots in HE buffer. To ensure
uniform coverage of the bottom of the well the plate
was spun briefly at 3000 g. To start the reaction,
NADPH and DTNB were added as a 20 mL aliquot in
HE buffer and the plate was moved to the plate reader
which had been preheated to 37 ꢀC. The optical density
at 412 nm was measured every 10 s and initial linear
reaction rates measured.
and PhLi (1.09 mL, 1.85 mmol, 1.7 M in hexane) under a
N2-atmosphere according to literature procedure.29
A
solution of 3-b-tosylcholest-5-ene (1 g, 1.85 mol) in dry
THF (5 mL) was added to the tellurolate solution, and
the resultant reaction mixture was heated at reflux for
6 h. After cooling to rt, the solution was concentrated
and the residue dissolved in CHCl3 (50 mL Â 3). The
combined CHCl3 extracts were filtered through anhy-
drous MgSO4, and the solvent was evaporated under
reduced pressure. The orange viscous oil was purified by
flash chromatography on silica gel using pentane as the
eluent to yield a light yellow viscous oil which was
crystallised from EtOH to furnish the title compound
(0.62 g, 58%) as a pale yellow solid: mp 108–110 ꢀC; H
1
Growth inhibition assay
NMR (CDCl3) d 0.68 (s, 3H), 0.87 (d, J=6.4 Hz, 6H),
0.92 (d, J=6.4 Hz, 3H), 1.01 (s, 3H), 1.64–2.14 (m,
26H), 2.40 (d, J=14.5 Hz, 1H), 2.92 (d, J=14.5 Hz,
1H), 4.07 (bs, 1H), 5.34 (d, J=4.9 Hz, 1H), 7.20–7.35
(m, 3H), 7.74 (dd, J=8.1, 1.5 Hz, 2H); MS m/z (relative
intensity) 576 (M+, 5), 572 (6), 410 (5), 369 (100), 255
(23).
Compound cytotoxicity was measured using modifi-
cations of the MTT assay as described by Mosmann41
and Carmichael.42 Human MCF-7 breast cancer cells
were seeded at 3000 cells/well into 96-well plates in
Dulbecco’s minimum essential medium (DMEM) sup-
plemented with 10% fetal bovine serum (FBS). After 16 h
at 37 ꢀC and 5.5% CO2 in air, drugs were added to the
wells at concentrations ranging from 0.1 to 20 mM. The
cells were further incubated for 72 h after which 40 mL per
well of a 2.5-mg/mL solution MTT (3-(4,5-dimethylthi-
azol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) solu-
tion was added and an additional 3 h, 37 ꢀC, 5.5% CO2 in
air, incubation was performed. At the end of the incu-
bation, the untransformed MTT was removed form each
well by aspiration and 150 mL per well of DMSO (dime-
thyl sulfoxide) was added. The plate was shaken to ensure
full solubilization of the formazan dye followed by dual
optical density readings of 595 and 655 nm using a multi-
well microplate spectrophotometer (Molecular Device
Corp., Menlo Park, CA, USA). Cytoviability of control
cells was considered to be 100%. For the treated cells
viability was expressed as a percentage of control cells.
All determinations were carried out in triplicate.
Compounds 1d–f were synthesised from the corre-
sponding tellurolate and the corresponding 3-tosylchol-
est-5-ene according to the procedure for 1c.
3-ꢁ-Phenyltellurenylcholest-5-ene (1d). Pale yellow solid
(57%): mp 115–117 ꢀC; 1H NMR (CDCl3) d 0.68 (s,
3H), 0.86 (d, J=6.2 Hz, 6H), 0.92 (d, J=6.2 Hz, 3H),
1.02 (s, 3H), 1.09–2.10 (m, 26H), 2.41 (d, J=14.7 Hz,
1H), 2.91 (d, J=14.7 Hz, 1H), 4.03 (bs, 1H), 5.33 (d,
J=4.8 Hz, 1H), 7.18–7.35 (m, 3H), 7.75 (dd, J=8.0,
1.6 Hz, 2H); MS m/z (relative intensity) 576 (M+, 8),
412 (15), 369 (100), 255 (27).
3-ꢁ-n-Butyltellurenylcholest-5-ene (1e). Yellow amor-
1
phous solid (50%); H NMR (CDCl3) d 0.67 (s, 3H),
0.86 (d, J=6.4 Hz, 6H), 0.90 (m, 6H), 0.99 (s, 3H), 1.03–
2.08 (m, 30H), 2.41 (td, J=14.3, 2.1 Hz, 1H), 2.57 (dt,
J=7.2, 1.7 Hz, 2H), 2.84 (d, J=14.3 Hz, 1H), 3.72 (bs,
1H), 5.33 (d, J=5.3 Hz, 1H); MS m/z (relative intensity)
556 (M+, 5), 554 (6), 369 (100), 255 (17).
Preparation of organotellurium compounds
Di-n-butyl ditelluride,43 diphenyl ditelluride,44 bis(4-
hydroxyphenyl) telluride (9),45 bis(4-methoxyphenyl)
ditelluride,44 bis(4-dimethylaminophenyl) ditelluride,44
N1,N10-bis-phthaloylimidyl spermidine,40 and 5-bromo-
3-ꢁ-(4-N,N-Dimethylaminophenyltellurenyl)cholest-5-ene
(1f). Further purification by flash chromatography
(pentane/CH2Cl2, 3:2) afforded the title compound
2,4-bis-(benzyloxy)pyrimidine33
were
synthesised
(40%) as a pale yellow solid: mp 125–127 ꢀC; H NMR
1
according to literature methods. All other chemicals
were purchased commercially and used without further
purification, unless otherwise stated. THF and ether
were distilled under nitrogen from sodium benzophe-
none and were used directly from the still. CH2Cl2 was
dried by distillation from calcium hydride under nitro-
(CDCl3) d 0.68 (s, 3H), 0.87 (d, J=1.9 Hz, 3H), 0.872
(d, J=1.9 Hz, 3H), 0.92 (d, J=6.5 Hz, 3H), 1.00 (s, 3H),
1.34–2.04 (m, 26H), 2.35 (d, J=14.5 Hz, 1H), 2.84 (d,
J=14.5 Hz, 1H), 2.95 (bs, 6H), 3.86 (bs, 1H); 5.33 (d,
J=5.3 Hz, 1H), 6.56 (d, J=8.8 Hz, 2H), 7.64 (d,
J=8.8 Hz, 2H). MS m/z (relative intensity) 620 (M+,
19), 505 (16), 449 (18), 167 (93).
1
gen. H NMR spectra were recorded at 400 MHz. Mass
spectra were recorded by direct inlet on a Finnigan MAT
GCQ, using +ve EI, or on a Finnigan Thermoquest
AQA (ESI 10 eV, probe temperature 300 ꢀC). High reso-
lution mass spectra were recorded by nanospray inlet on
a Quattro LCZ or Bruker Reflex III MALDI-TOF. M+
and (M+H)+ ions are given for 130Te.
Ethyl 4-phenyltellurenylbutyrate (2a). NaBH4 (0.405 g,
10.7 mmol) was added to a well stirred suspension of
diphenyl ditelluride (2.0 g, 4.89 mmol) in abs. EtOH
(20 mL) at ambient temperature under N2-atmosphere.
After 20 min stirring, the orange colour had faded, and
a solution of ethyl 4-bromobutyrate (2.0 g, 10.25 mmol)
in abs EtOH (5 mL) was added dropwise. The reaction
mixture was stirred for a further 6 h at the same
3-ꢀ-Phenyltellurenylcholest-5-ene (1c). A solution of the
lithium salt of benzenetellurolate was prepared from
elemental tellurium (0.236 g, 1.85 mmol) in dry THF

L. Engman et al. / Bioorg. Med. Chem. 11 (2003) 5091–5100
5097
temperature, poured into H2O and extracted with ether
(3 Â 50 mL). The combined ether extracts were washed
with brine (50 mL), dried (MgSO4), filtered and con-
centrated to give an orange oil. Purification by flash
chromatography on silica gel (gradient elution with
pentane: CH2Cl2 and CH2Cl2) furnished the title com-
pound (2.95 g, 94%) as a pale yellow oil; 1H NMR
organic phase was separated and the aqueous phase was
extracted with ether (50 mL Â 3). The combined ether
extracts were washed with brine (50 mL), dried
(MgSO4), filtered and concentrated to furnish the title
compound (1.72 g, 93%) as a yellow semi solid: mp 35–
37 C; H NMR (CDCl3) d 2.09 (quint, J=7.1 Hz, 2H),
2.47 (t, J=7.2 Hz, 2H), 2.91 (t, J=7.2 Hz, 2H), 7.24 (m,
3H), 7.72 (dd, J=8.1, 1.6 Hz, 2H); MS m/z (relative
intensity) 294 (M+, 14), 284 (39), 207 (29), 154 (87), 87
(100).
ꢀ
1
(CDCl3)
d 1.22 (t, J=7.2 Hz, 3H), 2.08 (quint,
J=7.2 Hz, 2H), 2.39 (t, J=7.2 Hz, 2H), 2.89 (t,
J=7.2 Hz, 2H), 4.09 (q, J=7.2 Hz, 2H), 7.22 (m, 3H),
7.71 (dd, J=8.2, 1.4 Hz, 2H).
Compounds 3b–f were synthesised according to the
procedure for 3a.
Compounds 2b–f were synthesised from the corre-
sponding ester according to the procedure for 2a. In the
preparation of 2d and 2e, bis(4-dimethylaminophenyl)
ditelluride, and for 2f, bis(4-methoxyphenyl) ditelluride,
replaced diphenyl ditelluride.
5-Phenyltellurenylvaleric acid (3b). Yellow viscous oil
(92%); 1H NMR (CDCl3) d 1.72 (quint, J=7.3 Hz, 2H),
1.84 (quint, J=7.3 Hz, 2H), 2.35 (t, J=7.3 Hz, 2H), 2.88
(t, J=7.3 Hz, 2H), 7.23 (m, 3H), 7.71 (dd, J=8.2,
1.2 Hz, 2H); HRMS calcd for (C11H15O2Te)+ m/z
308.0057 found m/z 308.0061.
Methyl 5-phenyltellurenylvaleroate (2b). Yellow viscous
1
oil (82%); H NMR (CDCl3) d 1.72 (quint, J=7.3 Hz,
2H), 1.84 (quint, J=7.3 Hz, 2H), 2.29 (t, J=7.3 Hz,
2H), 2.87 (t, J=7.3 Hz, 2H), 3.64 (s, 3H), 7.23 (m, 3H),
7.71 (dd, J=8.2, 1.6 Hz, 2H); MS m/z 322.7 (M+H)+.
12-Phenyltellurenyldodecanoic acid (3c). Yellow viscous
oil (90%); 1H NMR (CDCl3) d 1.24 (m, 14H), 1.62
(quint, J=7.3 Hz, 2H), 1.78 (quint, J=7.3 Hz, 2H), 2.34
(t, J=7.3 Hz, 2H), 2.89 (t, J=7.3 Hz, 2H), 7.22 (m, 3H),
7.70 (dd, J=8.1 Hz, 2H); MS m/z (relative intensity) 406
(M+, 79), 404 (81), 284 (13), 282 (15), 208 (49), 206 (43),
163 (100).
Methyl 12-phenyltellurenyldodecanoate (2c). Yellow vis-
cous oil (94%); 1H NMR (CDCl3) d 1.24 (m, 14H), 1.62
(quint, J=7.4 Hz, 2H), 1.78 (quint, J=7.4 Hz, 2H), 2.34
(t, J=7.4 Hz, 2H), 2.89 (t, J=7.4 Hz, 2H), 3.64 (s, 3H),
7.20 (m, 3H), 7.69 (dd, J=8.0, 1.6 Hz, 2H); MS m/z
(relative intensity) 420 (M+, 39), 418 (39), 181 (50), 163
(100).
5-(4-N,N-Dimethylaminophenyltellurenyl)valeric
acid
1
(3d). Orange viscous oil (94%); H NMR (CDCl3) d
1.74 (m, 4H), 2.33 (t, J=7.1 Hz, 2H), 2.75 (t, J=7.2 Hz,
2H), 2.95 (s, 6H), 6.57 (d, J=8.8 Hz, 2H), 7.64 (d,
J=8.8 Hz, 2H); MS m/z (relative intensity) 351 (M+,
48), 349 (41), 250 (46), 248 (41), 121 (100).
Methyl 5-(4-N,N-dimethylaminophenyltellurenyl)valero-
1
ate (2d). Orange viscous oil (89%); H NMR (CDCl3)
d 1.72 (m, 4H), 2.28 (t, J=7.3 Hz, 2H), 2.75 (t,
J=7.3 Hz, 2H), 2.93 (s, 6H), 3.63 (s, 3H), 6.55 (d,
J=8.9 Hz, 2H), 7.62 (d, J=8.9 Hz, 2H); MS m/z (rela-
tive intensity) 365 (M+, 38), 363 (34), 250 (52), 248 (50),
116 (100).
12 - (4 - N,N - Dimethylaminophenyltellurenyl)dodecanoic
1
acid (3e). Yellow viscous oil (87%); H NMR (CDCl3)
d 1.24 (m, 14H), 1.62 (quint, J=7.5 Hz, 2H), 1.66
(quint, J=7.5 Hz, 2H), 2.34 (t, J=7.5 Hz, 2H), 2.77 (t,
J=7.5 Hz, 2H), 2.95 (s, 6H), 6.58 (d, J=8.9 Hz, 2H),
7.63 (d, J=8.9 Hz, 2H); HRMS calcd for
(C20H34O2Te)+ m/z 450.1653 found m/z 450.1635.
Methyl 12-(4-N,N-dimethylaminophenyltellurenyl)dode-
canoate (2e). Orange viscous oil (76%); 1H NMR
(CDCl3) d 1.23 (m, 14H), 1.63 (m, 4H), 2.28 (t,
J=7.4 Hz, 2H), 2.75 (t, J=7.5 Hz, 2H), 2.93 (s,6H),
3.64 (s, 3H), 6.55 (d, J=8.9 Hz, 2H), 7.61 (d, J=8.9 Hz,
2H); MS m/z (relative intensity) 463 (M+, 36), 361 (35),
250 (67), 248 (66), 121 (100).
4-(4-Methoxyphenyltellurenyl) butyric acid (3f). Yellow
1
oil (21%); H NMR (CDCl3) d 2.08 (quint, J=7.2 Hz,
2H), 2.47 (t, J=7.2 Hz, 2H), 2.86 (t, J=7.6 Hz, 2H),
3.81 (s, 3H), 6.78 (d, J=8.8 Hz, 2H), 7.70 (d, J=8.4 Hz,
2H).
Ethyl
4-(4-methoxyphenyltellurenyl)butyrate
(2f).
Yellow oil (92%); 1H NMR (CDCl3) d 1.23 (t,
J=7.2 Hz, 3H), 2.05 (quint, J=7.2 Hz, 2H), 2.38 (t,
J=7.2 Hz, 2H), 2.83 (t, J=7.2 Hz, 2H), 3.79 (s, 3H),
4.10 (q, J=7.2 Hz, 2H), 6.75 (d, J=8.8 Hz, 2H), 7.67 (d,
J=8.8 Hz, 2H).
N-Acetyl-2-amino-4-phenyltellurenylbutyric acid lithium
salt (5a). To PhTeLi, prepared in dry THF from ele-
mental tellurium (0.41 g, 3.22 mmol) and PhLi (1.89 mL,
3.13 mmol, 1.7 M in hexane) according to a literature
procedure,44 was added a solution of 4 (0.4 g, 2.8 mmol)
and TMEDA (0.47 mL, 3.12 mmol) in THF (10 mL).
After 4 h of stirring at rt, the solvent was evaporated
and the residue washed successively with ether (30 mL)
and CH2Cl2 (30 mL). Flash chromatography on silica
gel using CH2Cl2/MeOH (3:1 and then 2:1) as eluent
furnished the title compound (0.81 g, 82%) as a pale
yellow solid: mp 129–131 ꢀC; 1H NMR (CD3OD) d 1.95
(s, 3H), 2.06–2.36 (m, 2H), 2.82–2.95 (m, 2H), 4.36
4-Phenyltellurenylbutyric acid (3a).
A solution of
LiOH.H2O (1.05 g, 25 mmol) in H2O (10 mL) was added
dropwise to a well stirred solution of 2a (2.0 g,
6.26 mmol) in THF (15 mL). After 24 h stirring at rt
under N2-atmosphere, THF was removed under
reduced pressure, H2O (50 mL) and ether (50 mL) were
added to the light yellow solution, which was acidified
under cooling to pH 6 with pre-cooled 5% HCl. The

5098
L. Engman et al. / Bioorg. Med. Chem. 11 (2003) 5091–5100
(q, J=7.0 Hz, 1H), 7.14–7.26 (m, 3H), 7.70 (dd, J=8.1,
1.5 Hz, 2H); MS m/z (relative intensity) 350 (M+, 4),
282 (45), 207 (25), 154 (100).
5-(Phenyltellurenyl)uracil (8a). To a solution of 7a
(0.3 g, 0.605 mmol) in CH2Cl2 (10 mL) was added tri-
methylsilyl iodide (0.22 mL, 1.57 mmol) at rt under an
argon atmosphere. The orange solution was stirred for
an additional 2 h, then MeOH (2 mL) was added and
the mixture stirred for a further 1 h. The precipitate was
filtered and the yellow solid recrystallised from EtOH to
furnish the title compound (0.145 g, 76%) as a light
Compounds 5b and 5c were synthesised from the corre-
sponding tellurolate according to the procedure for 5a.
N-Acetyl-2-amino-4-(p-N,N-dimethylaminophenyltellure-
nyl)butyꢀric acid lithium salt (5b). Yellow solid (92%):
yellow solid: mp 175 ꢀC (dec); H NMR (DMSO-d6) d
1
1
mp 131 C (dec); H NMR (DMSO-d6) d 1.80 (s, 3H),
7.21–7.31 (m, 3H), 7.44 (s, 1H), 7.63 (d, J=8.2 Hz, 2H),
11.99 (bs, 2H); MS m/z (relative intensity) 318 (M+, 31),
316 (32), 188 (100).
1.88–1.97 (m, 1H), 2.01–2.08 (m, 1H), 2.61–2.69 (m,
2H), 2.87 (s, 6H), 3.99 (q, J=7.0 Hz, 1H), 6.56 (d,
J=8.9 Hz, 2H), 7.47 (d, J=8.9 Hz, 2H), 7.57 (d,
J=7.6 Hz, 1H); MS m/z 401.0 (M+H)+.
Compounds 8b and 8c were synthesised according to the
procedure for 8a.
N-Acetyl-2-amino-4-n-butyltellurenylbutyric acid lithium
salt (5c). Yellow solid (72%): mp 176–178 ꢀC; 1H
NMR (DMSO-d6) d 0.86 (t, J=7.2 Hz, 3H), 1.31 (quint,
J=7.2 Hz, 2H), 1.63 (quint, J=7.2 Hz, 2H), 1.82 (s,
3H), 1.93–2.11 (m, 2H), 2.46–2.59 (m, 4H), 3.98 (q,
J=7.2 Hz, 1H), 7.63 (d, J=7.6 Hz, 1H); MS m/z (rela-
tive intensity) 330 (M+, 2), 284 (43), 256 (19), 207 (34),
154 (100).
5-(4-N,N-Dimethylaminophenyltellurenyl)uracil
(8b).
Yellow solid (77%): mp 168 ꢀC (dec); 1H NMR
(DMSO-d6) d 2.90 (s, 6H), 6.63 (d, J=8.9 Hz, 2H), 6.73
(dt, J=4.2 Hz, 1H), 7.57 (d, J=8.9 Hz, 2H), 10.80 (bs,
1H), 11.24 (bs, 1H); HRMS calcd for (C12H14N3O2Te)+
m/z 362.0149 found m/z 362.0197.
5-(4-Methoxyphenyltellurenyl)uracil (8c). Yellow solid
1
5-(Phenyltellurenyl)-2,4-bis(benzyloxy)pyrimidine (7a).
To a well stirred solution of 5-bromo-2,4-bis(benzylox-
y)pyrimidine (6, 0.50 g, 1.35 mmol) in THF (20 mL) at
À78 ꢀC was added dropwise n-BuLi (0.593 mL,
1.48 mmol, 2.5 M in hexane) under an argon atmos-
phere. The light yellow solution was stirred for 15 min
and a pre-cooled solution of diphenyl ditelluride (0.83 g,
2.02 mmol) in THF (5 mL) was slowly added. After 2 h
stirring at this temperature, the reaction was quenched
with glacial acetic acid (0.3 mL) and the dark red solu-
tion was allowed to warm to rt. The solution was con-
centrated, H2O (50 mL) and CH2Cl2 (50 mL) were
added and the organic layer was separated. The aqu-
eous phase was extracted with CH2Cl2 (50 mL), the
combined organic phases were washed with brine
(50 mL), dried (MgSO4) and filtered. The solvent was
evaporated to dryness in vacuo, and the dark red resi-
due was subjected to flash chromatography on silica gel
using gradient elution (pentane/CH2Cl2 1:1 and then
CH2Cl2) to give a yellow viscous oil which on recrys-
tallisation from EtOH furnished the title compound
(0.48 g, 72%) as white needles: mp 115–117 ꢀC; 1H
NMR (CDCl3) d 5.40 (s, 2H), 5.49 (s, 2H), 7.20–7.46
(m, 13H), 7.77 (dd, J=8.3, 1.4 Hz, 2H), 8.20 (s, 1H).
(79%): mp >280 ꢀC; H NMR (DMSO-d6) d 3.74 (s,
3H), 6.65 (d, J=8.8 Hz, 2H), 7.05 (s, 1H), 7.57 (d,
J=8.8 Hz, 2H), 10.91 (bs, 1H), 11.27 (bs, 1H); MS m/z
(relative intensity) 348 (M+, 25), 346 (23), 255 (35), 237
(43), 218 (95), 214 (100).
Bis[4-(4-bromobutoxy)phenyl] telluride (10). 1,4-Dibro-
mobutane (1.52 mL, 12.8 mmol) was added to a well
stirred suspension of bis(4-hydroxyphenyl)telluride (9,
1.0 g, 3.18 mmol) and anhydrous K2CO3 (1.76 g,
12.74 mmol) in dry acetone at rt under a N2-atmo-
sphere. After 20 h stirring at reflux (TLC monitoring),
the mixture was cooled, and concentrated under
reduced pressure. H2O (100 mL) and CH2Cl2 (100 mL)
were added, the organic phase was separated and the
aqueous phase was extracted with CH2Cl2 (50 mL Â 2).
The combined organic phases were washed with brine
(100 mL), dried (MgSO4), filtered and concentrated to
give a yellow solid. Purification by flash chromatography
(pentane/CH2Cl2, 3:2) and subsequent recrystallisation
from EtOH afforded the title compound (0.87 g, 47%) as
ꢀ
1
a white solid: mp 68–70 C; H NMR (CDCl3) d 1.89–
2.09 (m, 8H), 3.47 (t, J=6.5 Hz, 4H), 3.96 (t, J=6.5 Hz,
4H), 6.74 (d, J=8.8 Hz, 4H), 7.61 (d, J=8.8 Hz, 4H).
Compounds 7b and 7c were synthesised from the corre-
sponding ditelluride according to the procedure for 7a.
Bis[4-(4-dimethylaminobutoxy)phenyl]
A
telluride
hydrochloride (11). solution of dimethylamine
bis-
(1.61 mL 40% aq, 12.84 mmol) was added dropwise to a
stirred solution of 10 (0.50 g, 0.856 mmol) in THF
(20 mL) at ambient temperature under a N2-atmos-
phere. After 8 h stirring, the solution was concentrated
and the solid residue was dissolved in ether (50 mL) and
2 N NaOH (15 mL). The organic layer was separated
and the aqueous phase was extracted with ether (30 mL
 2). The combined organic extracts were washed with
brine (50 mL) and dried over MgSO4. After filtration
and removal of the solvent, the solid residue was
recrystallised from EtOH to furnish bis[4-(4-dimethyl-
aminobutoxy)phenyl] telluride (0.41 g, 93%) as a white
5-(4-N,N-Dimethylaminophenyltellurenyl)-2,4-bis(benzy-
loxy)pyrimidine (7b). Pale yellow solid (63%): mp 143–
145 ꢀC; H NMR (CDCl3) d 2.97 (s, 6H), 5.35 (s, 2H),
1
5.44 (s, 2H), 6.58 (d, J=8.9 Hz, 2H), 7.31–7.41 (m,
10H), 7.70 (d, J=8.9 Hz, 2H), 7.88 (s, 1H).
5-(4-Methoxyphenyltellurenyl)-2,4-bis(benzyloxy)pyrimi-
dine (7c). White needles (68%): mp 118–120 ꢀC; 1H
NMR (CDCl3) d 3.80 (s, 3H), 5.36 (s, 2H), 5.44 (s, 2H),
6.77 (d, J=8.8 Hz, 2H), 7.32–7.41 (m, 10H), 7.73 (d,
J=8.8 Hz, 2H), 7.99 (s, 1H).

L. Engman et al. / Bioorg. Med. Chem. 11 (2003) 5091–5100
5099
1
solid; H NMR (CDCl3) d 1.62 (m, 4H), 1.79 (m, 4H),
2.46–2.56 (m, 2H), 2.96 (t, J=6.8 Hz, 2H), 3.28–3.54
(m, 8H), 7.15–7.27 (m, 3H), 7.70 (dd, J=8.1 Hz, 2H);
HRMS calc for (C17H30N3OTe)+ m/z 422.1452 found
m/z 422.1458.
2.22 (s, 12H), 2.30 (t, J=7.4 Hz, 4H), 3.94 (t, J=6.4 Hz,
4H), 6.74 (d, J=8.8 Hz, 4H), 7.60 (d, J=8.8 Hz, 4H).
Bis[4-(4-dimethylaminobutoxy)phenyl] telluride (0.10 g,
0.292 mmol) and an ether solution of HCl (1 M,
0.69 mL) in ether (10 mL) were stirred at rt for 2 h under
a N2-atmosphere. The precipitate was filtered off and
washed with ether to afford the title compound (0.165 g,
96%) as a white solid.
Compounds 14b and 14c were synthesised according to
the procedure for 14a with subsequent purification by
chromatography (Sigmacell Type 20, ACN/H2O 2:1).
N-(3-Aminopropyl)-N-(4-aminobutyl)-4-(4-N,N-dimethyl-
aminophenyl)tellurenylpentanoic amide (14b). Yellow
viscous oil (23%); H NMR (CD3OD) d 1.60–2.16 (m,
10H), 2.46 (m, 2H), 2.91–3.06 (m, 4H), 3.30 (s, 6H),
3.35–3.51 (m, 6H), 7.61 (d, J=8.8 Hz, 2H), 7.88 (d,
J=8.8 Hz, 2H); MS m/z 479.4 (M+H)+.
N1,N10-Diphthaloyl-N5-(3-phenyltellurenylpropylcarbo-
nyl)spermidine (13a). A stirred solution of 3a (0.30 g,
1.03 mmol) in dry CH2Cl2 (30 mL) was treated with
freshly distilled triethylamine and cooled to 0 ꢀC. To
1
this
mixture
i-butylchloroformate
(0.146 mL,
1.13 mmol) was added and the mixture stirred at rt for
2 h. A solution of 12 (0.50 g, 1.234 mmol) in CH2Cl2
(10 mL) was added and stirring continued at ambient
temperature for 20 h. The reaction mixture was diluted
with CH2Cl2 (20 mL), washed successively with 2%
aqueous Na2CO3 (50 mL) and brine (50 mL), dried
(MgSO4) and concentrated under reduced pressure. The
resulting orange viscous oil was purified by flash chro-
matography using CH2Cl2/EtOAc (4:1) as eluent to
afford the title compound (0.6 g, 74%) as a pale yellow
viscous oil. 1H NMR (CDCl3) d 1.48–1.71 (m, 4H),
1.86–1.96 (m, 2H), 2.04–2.13 (m, 2H), 2.38 (q,
J=7.4 Hz, 4H), 2.86–2.98 (m, 2H), 3.22–3.41(m, 2H),
3.68 (q, J=6.6 Hz, 4H), 7.17–7.24 (m, 3H), 7.65–7.74
(m, 6H), 7.79–7.87 (m, 4H).
N-(3-Aminopropyl)-N-(4-aminobutyl)-3-(4-methoxyphe-
nyl)tellurenylbutanoic amide (14c). Yellow viscous oil
(67%); 1H NMR (DMSO-d6) d 1.60–2.16 (m, 10H), 2.46
(m, 2H), 2.91–3.06 (m, 4H), 3.30 (s, 6H), 3.35–3.51 (m,
6H), 7.61 (d, J=8.8 Hz, 2H), 7.88 (d, J=8.8 Hz, 2H);
MS m/z 452.4 (M+H)+.
Acknowledgements
Financial support from Cancerfonden and the NIH
(CA 77204 and CA 17094) is gratefully acknowledged.
References and Notes
Compounds 13b and 13c were synthesised from 3d and
3f, respectively, according to the procedure for 13a.
1. Mustacich, D.; Powis, G. Biochem. J. 2000, 346, 1.
2. Powis, G.; Mustacich, D.; Coon, A. Free Rad. Biol. Med.
2000, 29, 312.
3. Grogan, T. M.; Fenoglio-Prieser, C.; Zeheb, R.; Bellamy,
W.; Frutiger, Y.; Vela, E.; Stemmerman, G.; MacDonald, J.;
Richter, L.; Gallegos, A.; Powis, G. Human Pathol. 2000, 31,
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4. Hirota, K.; Matsui, M.; Iwata, S.; Nishiyama, A.; Mori,
K.; Yodoi, J. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 3633.
5. Rubartelli, A.; Bajetto, A.; Allavena, G.; Wollman, E.;
Sitia, R. J. Biol. Chem. 1992, 267, 24161.
N1,N10-Diphthaloyl-N5-[4-(4-N,N-dimethylaminophenyl)-
tellurenylbutylcarbonyl]spermidine (13b). Yellow viscous
oil (79%); 1H NMR (CDCl3) d 1.50–1.80 (m, 8H), 1.86–
1.97 (m, 2H), 2.18–2.27 (m, 2H), 2.73 (quint, J=7.6 Hz,
2H), 2.91 (s, 6H), 3.25–3.39 (m, 4H), 3.67 (q, J=7.3 Hz,
4H), 6.54 (d, J=8.8 Hz, 2H), 7.59 (d, J=8.8 Hz, 2H),
7.66–7.72 (m, 4H), 7.79–7.84 (m, 4H).
N1,N10-Diphthaloyl-N5-[3-(4-methoxyphenyl)tellurenyl-
propylcarbonyl]spermidine (13c). Yellow viscous oil
(83%); 1H NMR (CDCl3) d 1.56 (quint, J=7.3 Hz, 2H),
1.65 (quint, J=7.3 Hz, 2H), 1.90 (quint, J=7.3 Hz, 2H),
2.03 (quint, J=7.0 Hz, 2H), 2.34 (quint, J=7.1 Hz, 2H),
2.79 (t, J=7.3 Hz, 2H), 2.84 (t, J=7.3 Hz, 2H), 3.23–
3.38 (m, 4H), 3.63–3.70 (m, 2H), 3.75 (s, 3H), 6.72 (d,
J=8.9 Hz, 2H), 7.61 (dd, J=4.8, 8.5 Hz, 2H), 7.66–7.70
(m, 4H), 7.78–7.83 (m, 4H).
6. Prongay, A. J.; Engelke, D. R.; Williams, C. H., Jr. J. Biol.
Chem. 1989, 264, 2656.
7. Spyrou, G.; Enmark, E.; Miranda-Vizuete, A.; Gustafsson,
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