Copper, nickel, and zinc cyclam-amino acid and cyclam-peptide complexes may be synthesized with "click" chemistry and are noncytotoxic

Article abstract of DOI:10.1021/ic2020012

We describe the synthesis of cyclam metal complexes derivatized with amino acids or a tripeptide using a copper(I)-catalyzed Huisgen "click" reaction. The linker triazole formed during the synthesis plays an active coordinating role in the complexes. The reaction conditions do not racemize the amino acid stereocenters. However, a methylene group adjacent to the triazole is susceptible to H/D exchange under ambient conditions, an observation which has potentially important implications for structures involving stereocenters adjacent to triazoles in click-derived structures. The successful incorporation of several amino acids is described, including reactive tryptophan and cysteine side chains. All complexes are formed rapidly upon introduction of the relevant metal salt, including synthetically convenient cases where trifluoroacetate salts of cyclam derivatives are used directly in the metalation. None of the metal complexes displayed any cytotoxicity to mammalian cells, suggesting that the attachment of such complexes to amino acids and peptides does not induce toxicity, further supporting their potential suitability for labeling/imaging studies. One Cu(II)-cyclam-triazole-cysteine disulfide complex displayed moderate activity against MCF-10A breast nontumorigenic epithelial cells.

Full text of DOI:10.1021/ic2020012

Article
pubs.acs.org/IC
Copper, Nickel, and Zinc Cyclam−Amino Acid and Cyclam−Peptide
Complexes May Be Synthesized with “Click” Chemistry and Are
Noncytotoxic
Mingfeng Yu,† Jason R. Price,‡ Paul Jensen,‡ Carrie J. Lovitt,§ Todd Shelper,§ Sandra Duffy,§
Louisa C. Windus,§ Vicky M. Avery,§ Peter J. Rutledge,† and Matthew H. Todd*,†
†School of Chemistry, The University of Sydney, NSW 2006, Australia
‡Crystal Structure Analysis Facility, School of Chemistry, The University of Sydney, NSW 2006, Australia
§Discovery Biology, Eskitis Institute for Cell and Molecular Therapies, Griffith University, Nathan, QLD 4111, Australia
S
* Supporting Information
ABSTRACT: We describe the synthesis of cyclam metal complexes derivatized
with amino acids or a tripeptide using a copper(I)-catalyzed Huisgen “click”
reaction. The linker triazole formed during the synthesis plays an active
coordinating role in the complexes. The reaction conditions do not racemize the
amino acid stereocenters. However, a methylene group adjacent to the triazole is
susceptible to H/D exchange under ambient conditions, an observation which
has potentially important implications for structures involving stereocenters
adjacent to triazoles in click-derived structures. The successful incorporation of
several amino acids is described, including reactive tryptophan and cysteine side
chains. All complexes are formed rapidly upon introduction of the relevant metal
salt, including synthetically convenient cases where trifluoroacetate salts of cyclam derivatives are used directly in the metalation.
None of the metal complexes displayed any cytotoxicity to mammalian cells, suggesting that the attachment of such complexes to
amino acids and peptides does not induce toxicity, further supporting their potential suitability for labeling/imaging studies. One
Cu(II)−cyclam−triazole−cysteine disulfide complex displayed moderate activity against MCF-10A breast nontumorigenic
epithelial cells.
biomolecule/ligand binding could trigger activation of a metal
complex in vivo. To explore this striking possibility requires, as a
first step, the synthesis of a broader range of derivatized metal
complexes containing the pendant triazole and biological
ligands. We here report the synthesis of amino-acid- and
peptide-derived cyclam complexes via click chemistry. Our
results indicate that such conjugates may be assembled easily
and in high yields and that this approach offers an attractive
complement to more traditional methods of conjugating metal
complexes to peptides that rely on the formation of single
covalent bonds (creating, for example, amides,22 oximes,16 or
maleimides25), coordination events that join peptide and ligand
moieties26 or coordination events of metals into suitably
functionalized amino acid residues.27
INTRODUCTION
■
The combination of metal complexes and amino acids or
peptides holds significant promise for a variety of biological and
medical applications.1−7 There have been a few recent examples
exploiting the copper(I)-catalyzed azide−alkyne Huisgen cyclo-
addition (a “click” reaction) to unite peptides and metal
complexes.8−17 The advantages of such an approach are the
compatibility of the reagents with biologically relevant motifs
and the potential role the resultant triazole can play in the
coordination chemistry of the final complex. Peptides
frequently engage in highly specific interactions with biological
molecules, trafficking metal complexes that may be labeled with
a metal ion that may be monitored (e.g., via magnetic
resonance imaging or positron emission tomography). For
metal complexes to be used in this way, it is usually desirable
for the complex to be inert, and for the peptide to act simply as
a targeting agent.18−22 To date, there are few examples in which
the peptide is anything more than this;23 it would greatly
broaden the scope of potential therapeutic applications if the
metal complex could be chemically active (as opposed to
radioactive) and taken to its site of action by the peptide.
We have shown that a click-derived metal complex,
containing a pendant biotin motif, undergoes a change in
primary coordination geometry upon binding to the cognate
biomolecule avidin.24 This result implies that the act of
EXPERIMENTAL SECTION
■
General Materials. All reactions except solid phase peptide
synthesis were carried out in ordinary glassware. Solid phase peptide
synthesis was performed in 10 mL polypropylene syringes with filters,
purchased from Torviq. All reagents and solvents were purchased from
Sigma-Aldrich, Alfa Aesar, Merck, Mimotopes, GL Biochem, or Ajax
Finechem. Wang resin and HMBA-AM resin were purchased from
Received: September 13, 2011
Published: November 23, 2011
© 2011 American Chemical Society
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Inorganic Chemistry
Article
Novabiochem. Reagents were used as received unless otherwise
specified. Hexane and ethyl acetate were distilled before use;
dichloromethane and methanol were distilled over calcium hydride.
Instrumentation and Methods. 1H and 13C nuclear magnetic
resonance (NMR) spectra were recorded at 300 K on a Bruker
AVANCE 200 spectrometer (1H at 200.13 MHz and 13C at 50.32
MHz), a Bruker AVANCE 300 spectrometer (1H at 300.13 MHz and
13C at 75.47 MHz), or a Bruker DRX 400 spectrometer (1H at 400.13
MHz and 13C at 100.61 MHz). 1H and 13C NMR spectra are
referenced to solvent signals or (for some 1H NMR spectra)
CHCl3 (3×). The combined organic extracts were washed with
H2O (0.5 mL) and concentrated under reduced pressure to give
the desired N-functionalized cyclam.
(ii) Basification of trifluoroacetates was achieved by employing the
above procedure C(i), but using saturated Na2CO3 in place of
5 M KOH or 2 M NaOH.
General Synthetic Procedure D: Metal Complexation.29
(i) A solution of M(ClO4)2·6H2O (M = Cu, Ni, Zn; 1.0 equiv) in
EtOH (0.1 M) was added dropwise to a solution of
N-functionalized cyclam (1.0 equiv) in EtOH (0.1 M) at
room temperature. The reaction mixture was heated at reflux
for 1 h and cooled in an ice bath, and the solvent was decanted.
The remaining solid residue was washed with ice-cold EtOH
(3×) and diethyl ether (3×) and dried in vacuo to give the
desired metal complex.
(ii) Metal complexation was achieved by employing the above
procedure D(i) but using N-functionalized cyclam trifluoro-
acetate in place of N-functionalized cyclam and an extended
reaction time (3 h).
(iii) Metal complexation was achieved by employing the above
procedure D(i) but using N-functionalized cyclam trifluoro-
acetate in place of N-functionalized cyclam, an extended
reaction time (6 h), and a centrifuge to isolate the metal
complex from the suspension.
1
tetramethylsilane. H NMR signals are reported with chemical shift
values δ (ppm), multiplicity (s = singlet, d = doublet, t = triplet, q =
quartet, m = multiplet, and br = broad), relative integral, coupling
constants J (Hz), and assignments. Infrared spectra were recorded on a
Bruker Alpha FT-IR spectrometer. Ultraviolet−visible spectra were
recorded on a Cary 4000 or Cary 1E UV−visible spectrophotometer.
Low-resolution and high-resolution mass spectra were recorded on a
Finnigan LCQ mass spectrometer and a Bruker 7T Fourier Transform
Ion Cyclotron Resonance (FT-ICR) mass spectrometer, respectively.
Ionization of samples was carried out using either electrospray
ionization (ESI) or atmospheric pressure chemical ionization (APCI).
Optical rotation α was measured on a PerkinElmer 341 polarimeter
with a sodium lamp in a semimicro fused silica polarimeter cell
(length, 100 mm; capacity, 3.0 mL) at 20 °C unless otherwise stated.
Melting points were determined on an OptiMelt 100 automated
melting point apparatus. Elemental analyses were carried out by the
Campbell Microanalytical Laboratory (University of Otago,
New Zealand) on a Carlo Erba EA 1108 elemental analyzer. Analytic
reverse phase high-performance liquid chromatography (RP-HPLC)
was carried out on a Waters 2695 separations module with a Waters
2996 photodiode array detector and an Alliance series column heater.
A Waters SunFire C18 column (5 μm, 2.1 × 150 mm) was used at
30 °C at a flow rate of 0.2 mL/min. Preparative RP-HPLC was carried
out on a Waters 600 controller with a Waters 600 pump and a 2998
photodiode array detector. A Waters SunFire C18 OBD column
(5 μm, 19 × 150 mm) was used at a flow rate of 7 mL/min. Mobile
phases of 0.1% TFA in water (solvent A) and 0.1% TFA in acetonitrile
(solvent B) in different ratios were used in both analytic and
preparative HPLC. Enantioselective normal phase HPLC was performed
on a Waters 510 HPLC pump with a 2487 dual λ absorbance detector
and a Waters 410 differential refractometer. A Daicel 19325
CHIRALPAK AD-H analytic column (5 μm, 4.6 × 250 mm) was
eluted with 10% isopropanol/hexane at a flow rate of 0.5 mL/min. Data
acquired from both analytic and enantioselective HPLC were processed
using Waters Empower 2 software. Analytical thin layer chromatography
(TLC) was performed on Merck silica gel 60 F254 precoated aluminum
plates (0.2 mm) and visualized with UV irradiation (254 nm), with
ninhydrin or vanillin staining. Flash column chromatography was carried
out using Merck silica gel 60 (SiO2, 0.040−0.063 mm).
CAUTION! Perchlorate salts of metal complexes with organic ligands
are potentially explosive and should be handled with care. Only small
amounts of material should be prepared.
Tri-tert-butyl-11-((1-(2-(benzylamino)-2-oxoethyl)-1H-1,2,3-
triazol-4-yl)methyl)-1,4,8,11-tetraazacyclotetradecane-1,4,8-
tricarboxylate (5). Propargyl-tri-Boc-cyclam (4, 516 mg, 0.958
mmol) and 2-azido-N-benzylacetamide (3, 183 mg, 0.962 mmol)
were reacted using general synthetic procedure A to give 5 as a white
foam (588 mg, 84%). RF (EtOAc): 0.42. IR: νmax/cm−1 3310, 2973,
1
2930, 1682, 1549, 1455, 1411, 1364, 1241, 1156, 772, 698. H NMR
(300 MHz, CDCl3): δ 1.43 (s, 9H, C(CH3)3), 1.46 (s, 18H, 2 ×
C(CH3)3), 1.60−1.75 (m, 2H, CH2CH2CH2), 1.87 (br s, 2H,
CH2CH2CH2), 2.42 (m, 2H, CH2N(CH2-triazole)CH2), 2.60 (m,
2H, CH2N(CH2-triazole)CH2), 3.20−3.45 (br m, 12H, 3 × CH2C-
(Boc)CH2), 3.78 (s, 2H, NCH2-triazole), 4.43 (d, 2H, J 5.7,
CONHCH2Ph), 5.08 (s, 2H, triazole-CH2CONH), 6.96 (br s, 1H,
CONH), 7.20−7.33 (m, 5H, Ph-H), 7.64 (s, 1H, triazole-H). 13C
NMR (75 MHz, CDCl3): δ 26.6, 28.6, 43.7, 45.5, 46.9, 47.2, 47.5, 51.3,
52.9, 79.7, 124.5, 127.7, 127.8, 128.8, 137.5, 144.1, 155.6, 155.9, 165.2.
MS (ESI): m/z 729.1 ([M + H]+, 100%), 751.1 ([M + Na]+, 48%),
1163.8 (36%), 1457.1 ([2M + H]+, 20%), 1479.2 ([2M + Na]+, 62%),
1496.2 ([2M+K]+, 14%). HRMS (ESI): 751.44886 ([M + Na]+).
Calcd for C37H60N8O7Na ([M + Na]+): 751.44772.
General Synthetic Procedure A: The CuI-Catalyzed Huisgen
1,3-Dipolar Cycloaddition of Azides and Alkynes.24,28 Alkyne
(1.00 equiv) and azide (1.00 equiv) were dissolved in H2O/t-BuOH (1:1,
50 mM in alkyne or azide). A brown cloudy solution of CuSO4·5H2O
(0.05 equiv, 5 mol %) and sodium ascorbate (0.10 equiv, 10 mol %) in
H2O (25 mM in copper) was added. The reaction mixture was stirred at
room temperature for 12 h, quenched with 5% NaHCO3 solution (100
mL/mol copper), and extracted with DCM (3×). The combined organic
extracts were dried over MgSO4 and concentrated under reduced pressure
and the residue purified by flash column chromatography (silica gel,
EtOAc unless otherwise stated) to give the desired triazole.
General Synthetic Procedure B: TFA-Mediated Boc Remov-
al. Boc-protected amine (1.0 equiv) was dissolved in a mixture of
TFA/DCM/H2O (90:5:5, 5 mM). The reaction mixture was stirred at
room temperature for 6 h and concentrated under reduced pressure to
give the desired trifluoroacetate.
11-((1-(2-(Benzylamino)-2-oxoethyl)-1H-1,2,3-triazol-4-yl)-
methyl)-11-aza-1,4,8-triazoniacyclotetradecane-1,4,8-triium-
2,2,2-trifluoroacetate (6). Compound 5 (148 mg, 0.203 mmol) was
deprotected using general synthetic procedure B to give 6 as a
colorless glue (156 mg, 100%). IR: νmax/cm−1 3296, 3032, 2852, 1778,
1
1666, 1562, 1454, 1430, 1128, 1059, 1028, 837, 798, 721, 702. H
NMR (300 MHz, D2O): δ 2.02−2.15 (m, 4H, 2 × CH2CH2CH2),
3.04−3.49 (m, 16H, 2 × CH2CH2CH2 and 2 × NCH2CH2N), 4.21 (s,
2H, NCH2-triazole), 4.34 (s, 2H, CONHCH2Ph), 5.23 (s, 2H,
triazole-CH2CONH), 7.22−7.34 (m, 5H, Ph-H), 8.07 (s, 1H, triazole-
H). 13C NMR (75 MHz, D2O): δ 20.0, 20.3, 39.2, 40.2, 42.5, 43.0,
43.6, 47.2, 47.9, 50.0, 52.5, 110.8, 114.7, 118.6, 122.4, 127.7, 127.9,
128.1, 129.2, 137.8, 139.9, 162.3, 162.7, 163.2, 163.7, 167.6. MS (ESI)
m/z 429.1 ([M − 3TFA + H]+, 100%). HRMS (ESI): 429.30815 ([M −
3TFA + H]+). Calcd for C22H37N8O ([M − 3TFA + H]+):
429.30848.
General Synthetic Procedure C: Basification of Trifluoroa-
cetates.
2-(4-((1,4,8,11-Tetraazacyclotetradecan-1-yl)methyl)-1H-
1,2,3-triazol-1-yl)-N-benzylacetamide (7). Compound 6 (156 mg,
0.202 mmol) was subjected to general synthetic procedure C(i) to
give 7 as a colorless glue (87 mg, 100%). IR: νmax/cm−1 3277, 2928,
(i) Trifluoroacetate was dissolved in H2O (0.5 mL), basified with
5 M KOH or 2 M NaOH to pH 11−12, and extracted with
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Inorganic Chemistry
Article
2885, 2815, 1674, 1556, 1454, 724, 697. 1H NMR (300 MHz, CDCl3):
δ 1.52 (m, 2H, CH2CH2CH2), 1.73 (m, 2H, CH2CH2CH2), 2.43−
2.65 (br m, 16H, 2 × CH2CH2CH2 and 2 × NCH2CH2N), 2.81 (br s,
3H, 3 × CH2NHCH2), 3.64 (s, 2H, NCH2-triazole), 4.29 (s, 2H,
CONHCH2Ph), 4.87 (s, 2H, triazole-CH2CONH), 7.10−7.25
(m, 5H, Ph-H), 7.77 (s, 1H, triazole-H), 8.11 (br s, 1H, CONH).
13C NMR (75 MHz, CDCl3): δ 26.1, 28.7, 43.6, 47.2, 47.7, 48.0, 48.7,
49.5, 49.8, 51.2, 52.6, 53.9, 54.8, 124.4, 127.4, 127.6, 128.6, 137.8,
145.6, 165.5. MS (ESI): m/z 429.1 ([M + H]+, 100%). HRMS (ESI):
429.30812 ([M + H]+). Calcd for C22H37N8O ([M + H]+):
429.30848.
[Cu(7)](ClO4)2 Complex (8). Compound 7 (69 mg, 0.16 mmol)
and Cu(ClO4)2·6H2O (60 mg, 0.16 mmol) were reacted according to
general synthetic procedure D(i) to give 8 as a purple powder (96 mg,
86%). m.p.: 104−109 °C. UV−vis (CH3OH): λmax/nm 574, ε 135. IR:
νmax/cm−1 3594, 3368, 3238, 2941, 2882, 1677, 1543, 1454, 1429,
1365, 1232, 1065, 622. HRMS (ESI): 590.17822, 591.18199,
592.17598, 593.17960, 594.17376, 595.17728 ([M − ClO4]+). Calcd
for C22H36ClCuN8O5 ([M − ClO4]+) 590.17877, 591.18213,
592.17684, 593.18029, 594.17402, 595.17737. Anal. Calcd for
C22H36Cl2CuN8O9: C, 38.24; H, 5.25; N, 16.22. Found: C, 37.98;
H, 5.30; N, 16.44.
[Cu(7)](PF6)2 Complex (9). To a solution of compound 8 (96 mg,
0.14 mmol) in CH3OH (5 mL) was added dropwise excess saturated
KPF6 aqueous solution. The mixture was allowed to evaporate slowly
to give 9 as a dark blue crystal (72 mg, 66%). m.p.: 232−235 °C.
UV−vis (CH3OH): λmax/nm 597, ε 228. IR: νmax/cm−1 3427, 3278,
2939, 2885, 1681, 1542, 1455, 1430, 1366, 1230, 1098, 1066,
1040, 835, 558. HRMS (ESI): 636.19564 ([M − PF6]+). Calcd for
C22H36CuF6N8OP ([M − PF6]+): 636.19444. Anal. Calcd for
C22H36CuF12N8OP2·0.5KPF6: C, 30.23; H, 4.15; N, 12.82. Found:
C, 30.45; H, 4.10; N, 12.82.
(CH2-triazole)CH2), 2.62 (m, 2H CH2N(CH2-triazole)CH2), 3.04
(dd, 1H, J 14.1 and 6.6, CHHPh), 3.13 (dd, 1H, J 13.8 and 5.7,
CHHPh), 3.34 (m, 12H, 3 × CH2C(Boc)CH2), 3.71 (s, 3H,
COOCH3), 3.81 (s, 2H, NCH2-triazole), 4.83 (dd, 1H, J 13.8 and
6.3, CONHCH), 5.02 (s, 2H, triazole-CH2CONH), 6.52 (br s, 1H,
CONH), 7.01−7.04 (m, 2H, Ph-H), 7.20−7.30 (m, 3H, Ph-H), 7.54
(s, 1H, triazole-H). 13C NMR (75 MHz, CDCl3): δ 26.7, 28.6, 37.7,
45.5, 46.9, 47.2, 47.6, 48.6, 51.2, 52.6, 52.8, 53.5, 79.7, 124.3, 127.4,
128.8, 129.2, 135.4, 144.2, 155.6, 155.9, 164.9, 171.3. MS (ESI): m/z
801.1 ([M + H]+, 100%), 823.3 ([M + Na]+, 69%), 1623.3 ([2M +
Na]+, 23%). HRMS (ESI): 801.48798 ([M + H]+). Calcd for
C40H65N8O9 ([M + H]+): 801.48690.
(S)-Tri-tert-butyl-11-((1-(2-((1-methoxy-3-methyl-1-oxobutan-2-
yl)amino)-2-oxoethyl)-1H-1,2,3-triazol-4-yl)methyl)-1,4,8,11-tetraa-
zacyclotetradecane-1,4,8-tricarboxylate (10ii). Propargyl-tri-Boc
cyclam 4 (1.355 g, 2.515 mmol) and (S)-methyl 2-(2-azidoacetami-
do)-3-methylbutanoate (SI-5, 0.539 g, 2.516 mmol) were reacted
using general synthetic procedure A to give 10ii as a white foam (1.696
g, 90%). RF (EtOAc): 0.24. [α]D20: +5.2 (c 1.0, CHCl3). IR: νmax/cm−1
1
3318, 2974, 2933, 1744, 1677, 1542, 1465, 1412, 1365, 1243, 1152. H
NMR (300 MHz, CDCl3): δ 0.86 (d, 3H, J 6.9, CH3CHCH3), 0.90
(d, 3H, J 6.9, CH3CHCH3), 1.44 (s, 9H, C(CH3)3), 1.45 (s, 9H,
C(CH3)3), 1.46 (s, 9H, C(CH3)3), 1.73 (m, 2H, CH2CH2CH2),
1.91 (m, 2H, CH2CH2CH2), 2.12−2.20 (m, 1H, CH(CH3)2), 2.46
(m, 2H, CH2N(CH2-triazole)CH2), 2.64 (m, 2H, CH2N(CH2-triazole)-
CH2), 3.35 (m, 12H, 3 × CH2C(Boc)CH2), 3.73 (s, 3H, COOCH3),
3.85 (s, 2H, NCH2-triazole), 4.52 (dd, 1H, J 8.7 and 5.1, CONHCH),
5.14 (s, 2H, triazole-CH2CONH), 6.84 (br s, 1H, CONH), 7.67
(s, 1H, triazole-H). 13C NMR (75 MHz, CDCl3): δ 17.8, 18.9, 26.6,
28.5, 31.1, 45.4, 46.8, 47.1, 47.5, 51.1, 52.3, 52.7, 57.6 79.6,
124.4, 143.9, 155.6, 155.7, 155.8, 165.3, 171.8. MS (ESI): m/z 753.6
([M + H]+, 100%), 775.6 ([M + Na]+, 34%). HRMS (ESI): 753.48753
([M + H]+). Calcd for C36H65N8O9 ([M + H]+) 753.48690.
CCDC 840171 contains the supplementary crystallographic data for
this compound. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
(S)-Tri-tert-butyl-11-((1-(2-((3-(1H-indol-3-yl)-1-methoxy-1-
oxopropan-2-yl)amino)-2-oxoethyl)-1H-1,2,3-triazol-4-yl)-
methyl)-1,4,8,11-tetraazacyclotetradecane-1,4,8-tricarboxy-
late (10iii). Propargyl-tri-Boc cyclam 4 (1.077 g, 1.999 mmol) and
(S)-methyl 2-(2-azidoacetamido)-3-(1H-indol-3-yl)propanoate (SI-6,
0.602 g, 1.998 mmol) were reacted using general synthetic procedure
A to give 10iii as a white foam (1.510 g, 90%). RF (EtOAc): 0.44.
[α]D20: +14.4 (c 1.0, CHCl3). IR: νmax/cm−1 3311, 2975, 2934, 1744,
[Ni(7)](ClO4)2 Complex. Compound 7 (152 mg, 0.355 mmol)
and Ni(ClO4)2·6H2O (130 mg, 0.355 mmol) were reacted according
to general synthetic procedure D(i) to give the [Ni(7)](ClO4)2
complex as a pink powder (151 mg, 62%). m.p.: 162−167 °C.
UV−vis (CH3OH): λmax/nm 524, ε 13. IR: νmax/cm−1 3366, 3269,
2930, 2875, 1678, 1548, 1455, 1432, 1364, 1247, 1228, 1076, 622.
HRMS (ESI): 585.18417, 586.18777, 587.18018, 588.18369,
589.17691, 590.17996, 591.17744 ([M − ClO4]+). Calcd for C22H36-
ClN8NiO5 ([M − ClO4]+): 585.18452, 586.18788, 587.18014,
588.18334, 589.17702, 590.18036, 591.17458. Anal. Calcd for
C22H36Cl2N8NiO9: C, 38.51; H, 5.29; N, 16.33. Found: C, 38.44;
H, 5.51; N, 15.98.
[Zn(7)](ClO4)2 Complex. Compound 7 (89 mg, 0.21 mmol) and
Zn(ClO4)2·6H2O (78 mg, 0.21 mmol) were reacted according to
general synthetic procedure D(i) to give the [Zn(7)](ClO4)2 complex
as a white powder (102 mg, 71%). m.p.: 124−129 °C. IR: νmax/cm−1
3528, 3370, 3267, 2935, 2880, 1669, 1552, 1455, 1429, 1358, 1295,
1247, 1078, 623. HRMS (ESI): 591.17815, 592.18152, 593.17476,
594.17787, 595.17333, 596.17610, 597.17136, 598.17449 ([M −
ClO4]+). Calcd for C22H36ClN8O5Zn ([M − ClO4]+): 591.17832,
592.18168, 593.17523, 594.17852, 595.17393, 596.17732, 597.17108,
598.17443. Anal. Calcd for C22H36Cl2N8O9Zn: C, 38.14; H, 5.24; N,
16.17. Found: C, 37.80; H, 5.30; N, 15.92.
(S)-Tri-tert-butyl-11-((1-(2-((1-methoxy-1-oxo-3-phenyl-
propan-2-yl)amino)-2-oxo-ethyl)-1H-1,2,3-triazol-4-yl)-
methyl)-1,4,8,11-tetraazacyclotetradecane-1,4,8-tricarboxy-
late (10i). Propargyl-tri-Boc cyclam 4 (1.08 g, 2.00 mmol) and
(S)-methyl 2-(2-azidoacetamido)-3-phenylpropanoate (SI-4, 0.56 g,
2.14 mmol) were reacted using general synthetic procedure A to give
10i as a white foam (1.47 g, 92%). RF (EtOAc): 0.44. [α]D20: +18.0 (c
0.60, CHCl3). IR: νmax/cm−1 3303, 2976, 2933, 1746, 1682, 1538, 1463,
1412, 1365, 1244, 1158, 732, 700. 1H NMR (300 MHz, CDCl3): δ 1.44
(s, 9H, C(CH3)3), 1.46 (s, 18H, 2 × C(CH3)3), 1.65−1.80 (m, 2H,
CH2CH2CH2), 1.90 (m, 2H, CH2CH2CH2), 2.44 (m, 2H, CH2N-
1
1671, 1540, 1462, 1415, 1365, 1242, 1158, 734. H NMR (300 MHz,
CDCl3): δ 1.47 (s, 27H, 3 × C(CH3)3), 1.60−1.75 (m, 2H,
CH2CH2CH2), 1.90 (br s, 2H, CH2CH2CH2), 2.22 (br s, 2H,
CH2N(CH2-triazole)CH2), 2.51 (br s, 2H, CH2N(CH2-triazole)CH2),
3.21−3.50 (br m, 14H, 3 × CH2C(Boc)CH2 and CH2-indole), 3.70
(m, 5H, COOCH3 and NCH2-triazole), 4.85−5.09 (m, 3H,
CONHCH and triazole-CH2CONH), 6.48 (br s, 1H, CONH), 6.83
(br s, 2H, indole-H and triazole-H), 7.05−7.18 (m, 2H, indole-H),
7.34 (d, 1H, J 7.8, indole-H), 7.48 (d, 1H, J 7.8, indole-H), 9.77 (br s,
1H, indole-NH). 13C NMR (75 MHz, CDCl3): δ 26.9, 28.6, 45.5, 47.0,
47.4, 50.3, 52.2, 52.6, 53.1 79.7, 108.7, 111.7, 118.3, 119.4, 121.9,
123.2, 124.0, 127.7, 136.4, 143.2, 155.7, 156.1, 165.2, 171.6. MS (ESI):
m/z 840.0 ([M + H]+, 100%), 862.0 ([M + Na]+, 20%). HRMS
(ESI): 840.49721 ([M + H]+). Calcd for C42H66N9O9 ([M + H]+):
840.49780.
(S)-Methyl-2-(2-(4-((1,4,8,11-tetraazacyclotetradecan-1-yl)-
methyl)-1H-1,2,3-triazol-1-yl)-acetamido)-3-phenylpropanoate
(12i). Compound 10i (160 mg, 0.200 mmol) was deprotected using
general synthetic procedure B, followed by basification using general
synthetic procedure C(ii) to give 12i as a colorless glue (94 mg, 94%).
[α]D20: +12.5 (c 1.0, CH3OH). IR: νmax/cm−1 3282, 3192, 3030, 2948,
2817, 1744, 1683, 1553, 1454, 730, 700. 1H NMR (300 MHz, CDCl3):
δ 1.60−1.75 (m, 2H, CH2CH2CH2), 1.85 (m, 2H, CH2CH2CH2),
2.50−2.65 (m, 4H, CH2N(CH2-triazole)CH2), 2.65−2.95 (m, 12H,
3 × CH2NHCH2), 3.02−3.19 (m, 2H, CH2Ph), 3.65 (s, 3H,
COOCH3), 3.72 (s, 2H, NCH2-triazole), 4.42 (br s, 3H, 3 × NH),
4.70−4.76 (m, 1H, CONHCH), 5.11 (ABq, 2H, J 16.1, Δν 12.9,
triazole-CH2CONH), 7.13−7.28 (m, 5H, Ph-H), 7.71 (s, 1H, triazole-
H), 8.12 (br s, 1H, CONH). 13C NMR (75 MHz, CDCl3): δ 25.3,
27.1, 37.3, 46.7, 46.8, 47.5, 48.1, 48.8, 49.1, 50.4, 52.2, 52.3, 53.5, 53.7,
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53.9, 124.2, 126.8, 128.4, 129.1, 136.2, 144.7, 165.5, 171.5. MS (ESI):
m/z 501.4 ([M + H]+, 100%), 513.4 (18%). HRMS (ESI): 501.32926
([M + H]+). Calcd for C25H41N8O3 ([M + H]+): 501.32961.
(CH3OH): λmax/nm 563, ε 127. IR: νmax/cm−1 3565, 3352, 3240,
2962, 2881, 1737, 1686, 1541, 1456, 1436, 1366, 1226, 1061, 892, 819,
752, 622, 531. HRMS (ESI): 614.19977, 615.20312, 616.19751,
617.20108, 618.19524, 619.19815 ([M − ClO4]+). Calcd for
(S)-Methyl-2-(2-(4-((1,4,8,11-tetraazacyclotetradecan-1-yl)-
methyl)-1H-1,2,3-triazol-1-yl)-acetamido)-3-methylbutanoate
(12ii). Compound 10ii (150 mg, 0.199 mmol) was deprotected using
general synthetic procedure B, followed by basification using general
synthetic procedure C(ii) to give 12ii as a colorless glue (65 mg, 72%).
[α]D20: −18.0 (c 0.82, CH3OH). IR: νmax/cm−1 3262, 3212, 3040,
2953, 2932, 2818, 1742, 1683, 1548, 1463, 1435, 1373, 1336, 1270,
1206, 1148, 1051, 729. 1H NMR (300 MHz, CDCl3): δ 0.89 (d, 3H, J
6.9, CH3CHCH3), 0.92 (d, 3H, J 7.2, CH3CHCH3), 1.70 (m, 2H,
CH2CH2CH2), 1.87 (m, 2H, CH2CH2CH2), 2.10−2.21 (m, 1H,
CH(CH3)2), 2.56 (m, 4H, CH2N(CH2-triazole)CH2), 2.65−2.85 (br
m, 12H, 3 × CH2NHCH2), 3.17 (br s, 3H, 3 × NH), 3.72 (s, 3H,
COOCH3), 3.82 (s, 2H, NCH2-triazole), 4.48 (d, 1H, J 4.5,
CONHCH), 5.17 (s, 2H, triazole-CH2CONH), 7.70 (br s, 1H,
CONH), 7.87 (s, 1H, triazole-H). 13C NMR (75 MHz, CDCl3): δ
17.8, 18.8, 25.8, 28.4, 30.7, 46.9, 47.0, 47.7, 48.5, 49.2, 49.3, 50.7, 52.0,
52.3, 52.7, 54.2, 57.6, 124.2, 144.5, 165.5, 171.7. MS (ESI): m/z 453.3
([M + H]+, 100%), 509.2 (40%). HRMS (ESI): 453.32927 ([M +
H]+). Calcd for C21H41N8O3 ([M + H]+): 453.32961.
C
21H40ClCuN8O7 ([M − ClO4]+): 614.19990, 615.20326,
616.19797, 617.20142, 618.19515, 619.19850. Anal. Calcd for
C21H40Cl2CuN8O11·H2O: C, 34.41; H, 5.77; N, 15.29. Found: C,
34.63; H, 5.60; N, 14.94.
[Cu(12iii)](ClO4)2 Complex (13iii). Compound 12iii (65.4 mg,
0.121 mmol) and Cu(ClO4)2·6H2O (44.9 mg, 0.121 mmol) were
reacted according to general synthetic procedure D(i) to give 13iii as a
purple powder (69.3 mg, 71%). m.p.: 166−171 °C. UV−vis
(CH3CN): λmax/nm 556, ε 139. IR: νmax/cm−1 3570, 3359, 3240,
2954, 2883, 1736, 1698, 1540, 1456, 1434, 1363, 1228, 1060, 752, 621,
531. HRMS (ESI): 701.21037, 702.21370, 703.20854, 704.21145,
705.20660, 706.20879 ([M − ClO4]+). Calcd for C27H41ClCuN9O7
([M − ClO4]+): 701.21080, 702.21416, 703.20888, 704.21231,
705.20605, 706.20940. Anal. Calcd for C27H41Cl2CuN9O11·H2O: C,
39.54; H, 5.28; N, 15.37. Found: C, 39.52; H, 5.15; N, 15.32.
[Ni(12i)](ClO4)2 Complex (14i). Compound 12i (101 mg, 0.202
mmol) and Ni(ClO4)2·6H2O (74 mg, 0.202 mmol) were reacted
according to general synthetic procedure D(i) to give 14i as a pink
powder (77 mg, 50%). m.p.: 226−231 °C. [α]D20: +5.5 (c 1.0,
CH3OH). UV−vis (CH3OH): λmax/nm 516, ε 17. IR: νmax/cm−1
3502, 3336, 3270, 2954, 2877, 1741, 1696, 1541, 1455, 1437, 1365,
1225, 1077, 961, 926, 747, 704, 621, 516. HRMS (ESI): 657.20591,
658.20932, 659.20241, 660.20524, 661.19809, 662.20235, 663.19848
([M − ClO4]+). Calcd for C25H40ClN8NiO7 ([M − ClO4]+):
657.20565, 658.20901, 659.20126, 660.20448, 661.19815, 662.20149,
663.19571. Anal. Calcd for C25H40Cl2N8NiO11: C, 39.60; H, 5.32; N,
14.78. Found: C, 39.29; H, 5.58, N; 14.42.
[Ni(12ii)](ClO4)2 Complex (14ii). Compound 12ii (79.6 mg,
0.176 mmol) and Ni(ClO4)2·6H2O (64.3 mg, 0.176 mmol) were
reacted according to general synthetic procedure D(i) to give 14ii as a
pink powder (30.0 mg, 24%). m.p.: 271−273 °C. [α]D20: −12.7 (c 1.0,
CH3OH). UV−vis (CH3OH): λmax/nm 515, ε 12. IR: νmax/cm−1
3527, 3353, 3271, 2965, 2935, 2878, 1737, 1682, 1543, 1459, 1437,
1368, 1226, 1063, 960, 927, 824, 621. HRMS (ESI): 609.20579,
610.20882, 611.20160, 612.20506, 613.19789, 614.20062, 615.19668
([M − ClO4]+). Calcd for C21H40ClN8NiO7 ([M − ClO4]+):
609.20565, 610.20901, 611.20127, 612.20447, 613.19815, 614.20149,
615.19571. Anal. Calcd for C21H40Cl2N8NiO11: C, 35.52; H, 5.68; N,
15.78. Found: C, 35.80; H, 5.78; N, 15.77.
(S)-Methyl-2-(2-(4-((1,4,8,11-tetraazacyclotetradecan-1-yl)-
methyl)-1H-1,2,3-triazol-1-yl)-acetamido)-3-(1H-indol-3-yl)-
propanoate (12iii). Compound 10iii (168 mg, 0.200 mmol) was
deprotected in a mixture of TFA/EDT/H2O (20 mL, 95:2.5:2.5) at
room temperature for 1.5 h. The reaction solution was concentrated
under reduced pressure to give a brown glue, which was dissolved in
distilled water (50 mL), washed with CHCl3 (6 × 10 mL), and
concentrated under reduced pressure. The residue was dissolved in
distilled water (15 mL) and purified by preparative RP-HPLC
(gradient 0% to 25% B over 45 min). The combined fractions were
concentrated under reduced pressure, dissolved in distilled water
(1.5 mL), taken to pH 11−12 with saturated Na2CO3, and extracted
with CHCl3 (3 × 50 mL). The combined organic layers were washed
with distilled water (1 mL), dried over Na2SO4, and concentrated
under reduced pressure to give a colorless glue, which was dissolved in
MeOH (3 mL) and filtered with a cotton-packed pipet. The filtrate
was concentrated under reduced pressure and in vacuo to give 12iii as
a colorless glue (66 mg, 61%). [α]D20: +19.8 (c 1.0, CH3CN). IR:
νmax/cm−1 3263, 3050, 2926, 2820, 1740, 1678, 1548, 1448, 1345,
1
1214, 1113, 1053, 1012, 818, 738. H NMR (300 MHz, CDCl3): δ
1.72 (br s, 2H, CH2CH2CH2), 1.93 (br s, 2H, CH2CH2CH2), 2.45−
2.95 (br m, 16H, CH2N(CH2-triazole)CH2 and 3 × CH2NHCH2),
3.18−3.32 (m, 2H, CH2-indole), 3.56−3.73 (m, 2H, NCH2-triazole),
3.66 (s, 3H, COOCH3), 3.79 (br s, 3H, 3 × NH), 4.76 (br s, 1H,
CONHCH), 4.93 (ABq, 2H, J 16.2, Δν 39.4, triazole-CH2CONH),
6.69 (s, 1H, indole-H), 6.99−7.12 (m, 3H, CONH and indole-H),
7.25 (d, 1H, J 7.8, indole-H), 7.42 (d, 1H, J 7.8, indole-H), 7.46 (s,
1H, triazole-H), 11.27 (br s, 1H, indole-NH). 13C NMR (75 MHz,
CDCl3): δ 25.7, 27.1, 28.2, 47.0, 47.3, 48.1, 48.4, 49.4, 49.9, 51.2, 52.5,
52.6, 52.8, 54.1, 54.5, 108.1, 111.6, 118.2, 119.0, 121.6, 124.0, 127.3,
136.5, 145.6, 165.3, 171.8. MS (ESI): m/z 540.3 ([M + H]+, 100%),
270.5 ([M + 2H]2+,60%). HRMS (ESI): 540.34067 ([M + H]+).
Calcd for C27H42N9O3 ([M + H]+): 540.34051.
[Cu(12i)](ClO4)2 Complex (13i). Compound 12i (94.0 mg, 0.188
mmol) and Cu(ClO4)2·6H2O (69.6 mg, 0.188 mmol) were reacted
according to general synthetic procedure D(i) to give 13i as a purple
powder (107.7 mg, 75%). m.p.: 126−131 °C. UV−vis (CH3OH):
λmax/nm 559, ε 135. IR: νmax/cm−1 3528, 3354, 3244, 2954, 2931,
2885, 1734, 1679, 1639, 1543, 1454, 1227, 1063, 751, 705, 623. HRMS
(ESI): 662.19932, 663.20309, 664.19705, 665.20115, 666.19600,
667.19967 ([M − ClO4]+). Calcd for C25H40ClCuN8O7 ([M −
ClO4]+): 662.19990, 663.20326, 664.19798, 665.20142, 666.19515,
667.19850. Anal. Calcd for C25H40Cl2CuN8O11·H2O: C, 38.44; H,
5.42; N, 14.35. Found: C, 38.64; H, 5.37; N, 14.26.
CCDC 840172 contains the supplementary crystallographic data for
this compound. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[Ni(12iii)](ClO4)2 Complex (14iii). Compound 12iii (69.3 mg,
0.128 mmol) and Ni(ClO4)2·6H2O (47.0 mg, 0.129 mmol) were
reacted according to general synthetic procedure D(i) to give 14iii as a
pink powder (70.6 mg, 69%). m.p.: 198−203 °C. [α]D20: +14.2 (c 1.0,
CH3CN). UV−vis (CH3CN): λmax/nm 516, ε 11. IR: νmax/cm−1
3530, 3367, 3271, 2957, 2928, 2879, 1738, 1686, 1543, 1458, 1438,
1366, 1227, 1099, 1081, 961, 928, 752, 624. HRMS (ESI): 696.21573,
697.21952, 698.21178, 699.21530, 700.20943, 701.21250, 702.20858,
703.21104 ([M − ClO4]+). Calcd for C27H41ClN9NiO7 ([M −
ClO4]+): 696.21655, 697.21991, 698.21216, 699.21538, 700.20905,
701.21239, 702.20661, 703.20996. Anal. Calcd for
C27H41Cl2N9NiO11·0.5H2O: C, 40.22; H, 5.25; N, 15.63. Found: C,
40.51; H, 5.43; N, 15.39.
[Zn(12i)](ClO4)2 Complex (15i). Compound 12i (95 mg, 0.19
mmol) and Zn(ClO4)2·6H2O (71 mg, 0.19 mmol) were reacted
according to general synthetic procedure D(i) to give 15i as a white
powder (99 mg, 68%). m.p.: 122−127 °C. [α]D20: +6.6 (c 1.0,
CH3OH). IR: νmax/cm−1 3516, 3356, 3272, 2955, 2935, 2880, 1737,
1686, 1543, 1455, 1368, 1228, 1060, 949, 929, 749, 704, 621. HRMS
(ESI): 663.19990, 664.20316, 665.19689, 666.19926, 667.19498,
668.19759, 669.19318, 670.19653 ([M − ClO4]+). Calcd for
[Cu(12ii)](ClO4)2 Complex (13ii). Compound 12ii (65.0 mg,
0.144 mmol) and Cu(ClO4)2·6H2O (53.2 mg, 0.144 mmol) were
reacted according to general synthetic procedure D(i) to give 13ii as a
purple powder (59.8 mg, 58%). m.p.: 128−133 °C. UV−vis
C
25H40ClN8O7Zn ([M − ClO4]+): 663.19945, 664.20281,
665.19636, 666.19965, 667.19507, 668.19845, 669.19221, 670.19556.
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Anal. Calcd for C25H40Cl2N8O11Zn·0.5H2O: C, 38.80; H, 5.34; N,
14.48. Found: C, 38.67; H, 5.37; N, 14.25.
155.5, 155.8, 158.8, 165.2, 170.1. MS (ESI): m/z 891.3 ([M + H]+,
19%), 913.5 ([M + Na]+, 100%). HRMS (ESI): 891.50002 ([M +
H]+). Calcd for C43H71N8O10S ([M + H]+): 891.50084.
[Zn(12ii)](ClO4)2 Complex (15ii). Compound 12ii (66.2 mg,
0.146 mmol) and Zn(ClO4)2·6H2O (54.5 mg, 0.146 mmol) were
reacted according to general synthetic procedure D(i) to give 15ii as a
white powder (57.0 mg, 54%). m.p.: 116−121 °C. [α]D20: −18.8
(c 1.0, CH3OH). IR: νmax/cm−1 3570, 3358, 3241, 3163, 2961, 2937,
2881, 1736, 1684, 1544, 1457, 1436, 1272, 1245, 1081, 624. HRMS
(ESI): 615.20026, 616.20365, 617.19696, 618.19962, 619.19530,
620.19783, 621.19359, 622.19789 ([M − ClO4]+). Calcd for
(R)-Ethyl-2-(2-(4-((1,4,8,11-tetraazacyclotetradecan-1-yl)-
methyl)-1H-1, 2, 3-triazol-1-yl)acetamido)-3-((4-
methoxybenzyl)thio)propanoate (20). Compound 19 (446 mg,
0.500 mmol) was deprotected using general synthetic procedure B,
followed by preparative RP-HPLC purification (gradient 10% to 35%
B over 45 min) and basification using general synthetic procedure
C(ii) to give 20 as a colorless glue (182 mg, 62%). [α]D20: −18.5 (c
1.0, CH3CN). IR: νmax/cm−1 3255, 2931, 2822, 1741, 1688, 1610,
1553, 1512, 1463, 1371, 1341, 1301, 1245, 1214, 1179, 1113, 1031,
C
21H40ClN8O7Zn ([M − ClO4]+): 615.19945, 616.20281,
617.19636, 618.19965, 619.19506, 620.19848, 621.19221, 622.19556.
Anal. Calcd for C21H40Cl2N8O11Zn·H2O: C, 34.32; H, 5.76; N, 15.25.
Found: C, 34.64; H, 5.71; N, 15.07.
1
915, 830, 732. H NMR (300 MHz, CDCl3): δ 1.25 (t, 3H, J 7.2,
COOCH2CH3), 1.75 (m, 2H, CH2CH2CH2), 1.88 (m, 2H,
CH2CH2CH2), 2.50−3.00 (br m, 18H, CH2N(CH2-triazole)CH2
and 3 × CH2NHCH2 and CHCH2S), 3.66 (s, 2H, SCH2Ph), 3.77
(s, 2H, NCH2-triazole), 3.79 (s, 3H, PhOCH3), 3.98 (br s, 3H, 3 ×
NH), 4.17 (q, 2H, J 7.2, COOCH2CH3), 4.67−4.72 (m, 1H,
CONHCH), 5.13 (s, 2H, triazole-CH2CONH), 6.84 (d, 2H, J 8.4,
Ph-H), 7.20 (d, 2H, J 8.7, Ph-H), 7.54 (br s, 1H, CONH), 7.83 (s, 1H,
triazole-H). 13C NMR (75 MHz, CDCl3): δ 14.2, 25.8, 27.7, 32.9, 35.9,
47.1, 47.4, 47.7, 48.5, 49.1, 49.4, 50.7, 52.2, 52.8, 53.7, 54.1, 55.4, 61.9,
114.1, 124.3, 129.6, 130.2, 145.3, 158.9, 165.6, 170.3. HRMS (ESI):
591.34389 ([M + H]+). Calcd for C28H47N8O4S ([M + H]+)
591.34355.
[Zn(12iii)](ClO4)2 Complex (15iii). Compound 12iii (47.3 mg,
0.0876 mmol) and Zn(ClO4)2·6H2O (32.6 mg, 0.0875 mmol) were
reacted according to general synthetic procedure D(i) to give 15iii as a
white powder (52.6 mg, 75%). m.p.: 167−172 °C. [α]D20: +14.3 (c 0.7,
CH3CN). IR: νmax/cm−1 3568, 3368, 3272, 3241, 2953, 2878, 1739,
1690, 1544, 1457, 1434, 1358, 1229, 1084, 754, 624. HRMS (ESI):
702.21178, 703.21522, 704.20889, 705.21178, 706.20759, 707.21034,
708.20629, 709.20994 ([M − ClO4]+). Calcd for C27H41ClN9O7Zn
([M − ClO4]+): 702.21035, 703.21370, 704.20726, 705.21055,
706.20597, 707.20935, 708.20311, 709.20645. Anal. Calcd for
C27H41Cl2N9O11Zn·0.5H2O: C, 39.89; H, 5.21; N, 15.51. Found: C,
39.86; H, 5.15; N, 15.31.
Hexa-tert-butyl-11,11′-((1,1′-((((2R,2′R)-disulfanediylbis(1-
ethoxy-1-oxopropane-3,2-diyl))bis(azanediyl))bis(2-oxoethane-
2,1-diyl))bis(1H-1,2,3-triazole-4,1-diyl))bis(methylene))bis-
(1,4,8,11-tetraazacyclotetradecane-1,4,8-tricarboxylate)
(18). Propargyl-tri-Boc cyclam 4 (252 mg, 0.468 mmol) and (2R,2′R)-
diethyl 3,3′-disulfanediylbis(2-(2-azidoacetamido)propanoate) (17,
108 mg, 0.234 mmol) were reacted using general synthetic procedure
A. The residue was purified by flash column chromatography (silica
gel, EtOAc ramping to EtOAc/MeOH = 95:5) to give 18 as a white
foam (239 mg, 66%). RF (EtOAc/MeOH, 9:1): 0.52. [α]D20: +4.2
(c 0.8, CHCl3). IR: νmax/cm−1 3301, 2975, 2934, 1742, 1676, 1540,
1469, 1414, 1367, 1241, 1157. 1H NMR (300 MHz, CDCl3): δ 1.27 (t,
6H, J 7.2, 2 × CH2CH3), 1.44 (s, 18H, 2 × C(CH3)3), 1.46 (s, 36H,
4 × C(CH3)3), 1.72 (m, 4H, 2 × CH2CH2CH2), 1.91 (m, 4H, 2 ×
CH2CH2CH2), 2.45 (m, 4H, 2 × CH2C(CH2-triazole)CH2), 2.64 (m,
4H, 2 × CH2C(CH2-triazole)CH2), 3.05−3.25 (m, 4H, CH2SSCH2),
3.35 (m, 24H, 6 × CH2C(Boc)CH2), 3.84 (s, 4H, 2 × NCH2-triazole),
4.20 (q, 4H, J 7.2, 2 × CH2CH3), 4.78−4.85 (m, 2H, 2 × CONHCH),
5.23 (ABq, 4H, J 16.5, Δν 34.7, 2 × triazole-CH2CONH), 7.73 (br s,
4H, 2 × CONH and 2 × triazole-H). 13C NMR (75 MHz, CDCl3): δ
14.1, 26.5, 28.5, 40.1, 45.3, 46.8, 47.0, 47.4, 48.0, 50.9, 51.7, 52.5, 62.2,
79.7, 124.7, 143.5, 155.6, 155.9, 165.7, 169.6. MS (ESI): m/z 1508.6
([M − S + Na]+, 47%), 1540.7 ([M + H]+, 100%), 1562.7 ([M + Na]+,
43%). HRMS (ESI): 1539.86001 ([M + H]+). Calcd for C70H123N16O18S2
([M + H]+): 1539.86372.
(R)-11-((1-(2-((1-Ethoxy-3-mercapto-1-oxopropan-2-yl)-
amino)-2-oxoethyl)-1H-1,2,3-triazol-4-yl)methyl)-11-aza-1,4,8-
triazoniacyclotetradecane-1,4,8-triium-2,2,2-trifluoroacetate
(21). To a degassed solution of compound 19 (356 mg, 0.399 mmol)
in TFA (40 mL) was added anisole (2.2 mL, 20.2 mmol). The reaction
mixture was heated at reflux under Ar for 1.5 h, concentrated under
reduced pressure, and azeotroped with toluene. The crude residue was
dissolved in distilled water (40 mL) and washed with ethyl acetate
(2 × 20 mL). The combined organic layers were extracted with water
(2 × 20 mL) and pooled aqueous phases back-washed with ethyl
acetate (20 mL). The combined aqueous extracts were purified by
preparative RP-HPLC (gradient 0% to 25% B over 45 min) to give 21
as a colorless glue (254 mg, 78%). [α]D20: +0.6 (c 1.0, CH3CN). IR:
νmax/cm−1 2996, 2844, 2362, 1739, 1677, 1554, 1464, 1430, 1378,
1
1335, 1199, 1138, 1062, 838, 801, 721. H NMR (300 MHz, D2O): δ
1.04 (t, 3H, J 7.2, COOCH2CH3), 2.00 (m, 4H, 2 × CH2CH2CH2),
2.75−2.80 (m, 2H), 3.10−3.25 (m, 8H), 3.35−3.50 (m, 8H) (total
18H, CH2N(CH2-triazole)CH2 and 3 × CH2NHCH2 and CHCH2S),
4.01 (q, 2H, J 7.2, COOCH2CH3), 4.36 (s, 2H, NCH2-triazole), 4.49
(t, 1H, J 5.7, CONHCH), 5.20 (s, 2H, triazole-CH2CONH), 8.06 (s,
1H, triazole-H). 13C NMR (75 MHz, D2O): δ 13.5, 19.0, 25.3, 38.3,
38.6, 41.5, 41.9, 45.6, 48.9, 49.1, 52.3, 55.5, 63.4, 110.5, 114.4, 118.2,
122.1, 129.0, 137.5, 161.8, 162.3, 162.7, 163.2, 167.7, 171.5. MS (ESI):
m/z 471.3 ([M − 3TFA + H]+, 96%), 236.2 ([M − 3TFA + 2H]2+,
100%). HRMS (ESI): 471.28576 ([M − 3TFA + H]+). Calcd for
C20H39N8O3S ([M − 3TFA + H]+): 471.28603.
(R)-Tri-tert-butyl-11-((1-(2-((1-ethoxy-3-((4-methoxybenzyl)-
thio)-1-oxopropan-2-yl)amino)-2-oxoethyl)-1H-1,2,3-triazol-4-
yl)methyl)-1,4,8,11-tetraazacyclotetradecane-1,4,8-tricarboxy-
late (19). Propargyl-tri-Boc cyclam 4 (73 mg, 0.14 mmol) and (R)-
ethyl 2-(2-azidoacetamido)-3-(4-methoxybenzylthio)propanoate (16,
[Cu(20)](ClO4)2 Complex (22). Compound 20 (77.5 mg, 0.131
mmol) and Cu(ClO4)2·6H2O (48.6 mg, 0.131 mmol) were reacted
according to general synthetic procedure D(i) to give 22 as a purple
powder (81.4 mg, 73%). m.p.: 102−107 °C. UV−vis (CH3CN): λmax
/
nm 560, ε 123. IR: νmax/cm−1 3570, 3336, 3237, 3158, 2939, 2884,
1737, 1700, 1610, 1539, 1513, 1460, 1430, 1364, 1301, 1239, 1184,
1064, 1027, 891, 833, 744, 676, 620, 530. HRMS (ESI): 752.21426,
753.22046, 754.21230, 755.21773, 756.21284, 757.21608, 758.21757
([M − ClO4]+). Calcd for C28H46ClCuN8O8S ([M − ClO4]+):
752.21384, 753.21720, 754.21189, 755.21534, 756.20906, 757.21243,
758.21579. Anal. Calcd for C28H46Cl2CuN8O12S·H2O: C, 38.60; H,
5.55; N, 12.86. Found: C, 38.52; H, 5.45; N, 12.88.
48 mg, 0.14 mmol) were reacted using general synthetic procedure A
20
to give 19 as a white foam (99 mg, 82%). RF (EtOAc): 0.55. [α]D
:
−3.5 (c 1.0, CHCl3). IR: νmax/cm−1 3297, 2975, 2933, 1742, 1682,
1610, 1537, 1511, 1464, 1412, 1365, 1242, 1157. 1H NMR (300 MHz,
CDCl3): δ 1.25 (t, 3H, J 7.2, COOCH2CH3), 1.44 (s, 9H, C(CH3)3),
1.45 (s, 9H, C(CH3)3), 1.46 (s, 9H, C(CH3)3), 1.72 (m, 2H,
CH2CH2CH2), 1.90 (m, 2H, CH2CH2CH2), 2.45 (m, 2H, CH2C-
(CH2-triazole)CH2), 2.63 (m, 2H, 1 CH2C(CH2-triazole)CH2), 2.77−
2.92 (m, 2H, CHCH2S), 3.34 (m, 12H, 3 × CH2C(Boc)CH2), 3.64 (s,
2H, SCH2Ph), 3.79 (s, 3H, OCH3), 3.83 (s, 2H, NCH2-triazole), 4.18
(q, 2H, J 7.2, COOCH2CH3), 4.71−4.78 (m, 1H, CONHCH), 5.10 (s,
2H, triazole-CH2CONH), 6.84 (br d, 2H, J 8.4, Ph-H), 6.94 (br s, 1H,
CONH), 7.19 (d, 2H, J 8.7, Ph-H), 7.65 (s, 1H, triazole-H). 13C NMR
(75 MHz, CDCl3): δ 14.1, 26.6, 28.5, 33.0, 35.9, 45.3, 46.8, 47.0, 47.5,
51.0, 51.9, 52.5, 55.3, 62.0, 79.6, 114.0, 124.3, 129.4, 130.1, 144.0,
[Ni(20)](ClO4)2 Complex (23). Compound 20 (102 mg, 0.172
mmol) and Ni(ClO4)2·6H2O (62.8 mg, 0.172 mmol) were reacted
according to general synthetic procedure D(i) to give 23 as a pink
powder (73.8 mg, 51%). m.p.: 65−70 °C. [α]D20: −13.5 (c 1.0,
CH3CN). UV−vis (CH3CN): λmax/nm 531, ε 9. IR: νmax/cm−1 3525,
3269, 2965, 2929, 2877, 1740, 1701, 1611, 1540, 1513, 1458, 1363,
1304, 1233, 1184, 1072, 962, 926, 837, 744, 675, 620, 527. HRMS
12827
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Inorganic Chemistry
Article
(ESI): 747.22020, 748.22474, 749.21679, 750.22061, 751.21606,
752.21830, 753.21712, 754.21937 ([M − ClO4]+). Calcd for
C28H46ClN8NiO8S ([M − ClO4]+): 747.21958, 748.22294,
749.21519, 750.21842, 751.21208, 752.21543, 753.20964, 754.21299.
Anal. Calcd for C28H46Cl2N8NiO12S: C, 39.64; H, 5.47; N, 13.21.
Found: C, 39.68; H, 5.62; N, 13.21.
[Zn(20)](ClO4)2 Complex (24). Compound 20 (35.2 mg, 0.0596
mmol) and Zn(ClO4)2·6H2O (22.2 mg, 0.0596 mmol) were reacted
according to general synthetic procedure D(i) to give 24 as a white
powder (41.4 mg, 81%). m.p.: 72−77 °C. [α]D20: −14.0 (c 1.0,
CH3CN). IR: νmax/cm−1 3546, 3340, 3250, 2936, 2882, 1737, 1694,
1610, 1541, 1513, 1458, 1367, 1300, 1244, 1183, 1087, 952, 835, 623.
HRMS (ESI): 753.21438, 754.21919, 755.21090, 756.21429,
757.20933, 758.21372, 759.21117, 760.21498 ([M − ClO4]+). Calcd
for C28H46ClN8O8SZn ([M − ClO4]+) 753.21338, 754.21674,
755.21028, 756.21359, 757.20898, 758.21238, 759.20613, 760.20949.
Anal. Calcd for C28H46Cl2N8O12SZn·0.5H2O: C, 38.92; H, 5.48; N,
12.97. Found: C, 38.95; H, 5.45; N, 12.92.
[Cu2((2R,2′R)-diethyl-3,3′-disulfanediylbis(2-(2-(4-((1,4,8,11-
tetraazacyclotetradecan-1-yl)-methyl)-1H-1,2,3-triazol-1-yl)-
acetamido)propanoate)](ClO4)4 Complex (25). Compound 21
(69.5 mg, 0.0855 mmol) and Cu(ClO4)2·6H2O (31.7 mg, 0.0856
mmol) were reacted according to general synthetic procedure D(ii) to
give 25 as a purple powder (52.0 mg, 83%). m.p.: 202−207 °C. UV−
vis (CH3CN): λmax/nm 567, ε 182. IR: νmax/cm−1 3588, 3536, 3244,
2940, 2885, 1735, 1692, 1542, 1461, 1368, 1300, 1229, 1091, 623.
HRMS (ESI): 631.14824, 631.64972, 632.14663, 632.64801,
633.14600, 633.64711, 634.14562, 634.64619, 635.14497 ([M −
2ClO4]2+). Calcd for C40H74Cl2Cu2N16O14S2 ([M − 2ClO4]2+):
631.14850, 631.65018, 632.14753, 632.64924, 633.14612, 633.64779,
634.14520, 634.64688, 635.14374. Anal. Calcd for
C40H74Cl4Cu2N16O22S2·4H2O: C, 31.27; H, 5.38; N, 14.59. Found:
C, 31.22; H, 5.11; N, 14.66.
[Ni(21−3TFA)](ClO4)2 Complex (26). Compound 21 (134 mg,
0.165 mmol) and Ni(ClO4)2·6H2O (60.4 mg, 0.165 mmol) were
reacted according to general synthetic procedure D(ii) to give 26 as a
pink powder (41.0 mg, 34%). m.p.: 150−155 °C. [α]D20: −2.2 (c 1.0,
CH3CN). UV−vis (CH3CN): λmax/nm 518, ε 8. IR: νmax/cm−1 3472,
3271, 2936, 2877, 1737, 1688, 1541, 1461, 1431, 1368, 1308, 1223,
1080, 962, 927, 852, 826, 623. HRMS (ESI): 627.16098, 628.16482,
629.15686, 630.16042, 631.15353, 632.15659, 633.15175 ([M −
ClO4]+). Calcd for C20H38ClN8NiO7S ([M − ClO4]+) 627.16207,
628.16543, 629.15769, 630.16089, 631.15457, 632.15791, 633.15213,
634.15548. Anal. Calcd for C20H38Cl2N8NiO11S·0.5H2O: C, 32.58; H,
5.33; N, 15.20. Found: C, 32.51; H, 5.37; N, 15.02.
3.60 (s, 3H, COOCH3), 3.87 (ABq, 2H, J 15.6, Δν 11.9, N3CH2), 4.14
(t, 1H, J 7.2, CONHCH), 4.23 (t, 1H, J 8.0, CONHCH), 4.30 (t, 1H, J
7.6, CONHCH), 8.00 (d, 1H, J 8.8, CONH), 8.13 (d, 1H, J 6.8,
CONH), 8.15 (d, 1H, J 8.4, CONH). 13C NMR (75 MHz,
(CD3)2SO): δ 18.0, 18.1, 18.3, 18.9, 19.0, 19.1, 29.7, 30.4, 30.7,
50.5, 51.5, 57.3, 57.6, 167.2, 170.5, 171.2, 171.7. MS (ESI): m/z 413.0
([M + H]+, 100%), 435.1 ([M + Na]+, 17%), 824.8 ([2M + H]+,
62%), 846.9 ([2M + Na]+, 36%). HRMS (ESI): 435.23244 ([M +
Na]+). Calcd for C18H32N6NaO5 ([M + Na]+): 435.23264. Anal. Calcd
for C18H32N6O5: C, 52.41; H, 7.82; N, 20.37. Found: C, 52.34; H,
8.00; N, 20.44.
Tri-tert-butyl-11-((1-((4S,7S,10S)-4,7,10-triisopropyl-
3,6,9,12-tetraoxo-2-oxa-5,8,11-triazatri-decan-13-yl)-1H-1,2,3-
triazol-4-yl)methyl)-1,4,8,11-tetraazacyclotetradecane-1,4,8-
tricarboxylate (32). Propargyl-tri-Boc cyclam 4 (52 mg, 0.096
mmol) and compound 31 (40 mg, 0.097 mmol) were reacted using
general synthetic procedure A to give 32 as a white foam (74 mg,
81%). RF (EtOAc): 0.41. [α]D20: −19.5 (c 1.0, CHCl3). IR: νmax/cm−1
3280, 3077, 2969, 2934, 1741, 1681, 1641, 1546, 1466, 1413, 1367,
1
1239, 1158, 915, 729. H NMR (300 MHz, CDCl3): δ 0.82−0.95 (m,
18H, 3 × CH(CH3)2), 1.46 (s, 27H, 3 × C(CH3)3), 1.71 (m, 2H,
CH2CH2CH2), 1.94 (m, 4H, CH2CH2CH2 and 2 × CH(CH3)2), 2.11
(m, 1H, CH(CH3)2), 2.43 (m, 2H, CH2N(CH2-triazole)CH2), 2.62
(m, 2H, CH2N(CH2-triazole)CH2), 3.34 (m, 12H, 3 × CH2C(Boc)-
CH2), 3.75 (s, 3H, COOCH3), 3.81 (s, 2H, NCH2-triazole), 4.58−
4.67 (m, 3H, 3 × NHCHCO), 5.06 (br d, 1 H, J 15.6, triazole-
CH2CONH), 5.39 (br d, 1H, J 15.6, triazole-CH2CONH), 7.84 (br s,
2H, CONH and triazole-H), 8.06 (br s, 1H, CONH), 8.37 (br s, 1H,
CONH). 13C NMR (75 MHz, CDCl3): δ 17.9, 18.7, 19.0, 19.1, 26.5,
28.6, 29.7, 30.8, 31.0, 32.4, 45.2, 46.9, 48.1, 50.8, 52.3, 57.3, 58.5, 58.8,
79.5, 124.6, 143.1, 155.6, 155.9, 165.7, 171.3, 172.0, 172.7. MS (ESI):
m/z 952.0 ([M + H]+, 56%), 973.8 ([M + Na]+, 100%). HRMS
(ESI): 951.62273 ([M + H]+). Calcd for C46H83N10O11 ([M + H]+):
951.62373.
11-((1-((4S,7S,10S)-4,7,10-Triisopropyl-3,6,9,12-tetraoxo-2-
oxa-5,8,11-triazatridecan-13-yl)-1H-1,2,3-triazol-4-yl)methyl)-
11-aza-1,4,8-triazoniacyclotetradecane-1,4,8-triium-2,2,2-tri-
fluoroacetate (33). Compound 32 (290 mg, 0.305 mmol) was
deprotected using general synthetic procedure B, followed by
preparative HPLC purification (gradient 0% to 30% B over 45 min),
to give 33 as a colorless glue (259 mg, 86%). [α]D20: −26.5 (c 1.0,
CH3CN). IR: νmax/cm−1 3286, 3078, 2966, 2874, 1739, 1676, 1647,
1
1550, 1464, 1434, 1397, 1200, 1133, 832, 801, 721. H NMR (400
MHz, D2O): δ 0.83−0.91 (m, 18H, 3 × CH(CH3)2), 1.79 (br s, 2H,
CH2CH2CH2), 1.88−2.02 (m, 4H, CH2CH2CH2 and 2 ×
CH(CH3)2), 2.07−2.14 (m, 1H, CH(CH3)2), 2.70−3.21 (m, 16H,
CH2N(CH2-triazole)CH2 and 3 × CH2NHCH2), 3.67 (s, 3H,
COOCH3), 3.75 (br s, 2H, NCH2-triazole), 4.08 (d, 2H, J 8.0, 2 ×
NHCHCO), 4.18 (d, 1H, J 6.0, NHCHCO), 5.27 (ABq, 2H, J 16.8,
Δν 21.3, triazole-CH2CONH)), 7.89 (s, 1H, triazole-H). 13C NMR
(75 MHz, D2O): δ 17.8, 18.1, 18.4, 18.6, 18.7, 22.8, 24.6, 30.3, 30.5,
30.6, 44.0, 45.4, 46.6, 46.8, 47.3, 48.7, 52.1, 52.7, 53.0, 54.3, 59.0, 59.7,
60.2, 111.0, 114.8, 118.7, 122.6, 126.3, 144.8, 162.6, 163.1, 163.5,
164.0, 168.2, 173.5, 173.8, 174.2. MS (ESI): m/z 326.3 ([M − 3TFA
+2H]2+, 79%), 651.4 ([M − 3TFA + H]+, 100%). HRMS (ESI):
651.46559 ([M − 3TFA + H]+). Calcd for C31H59N10O5 ([M − 3TFA +
H]+): 651.46644
[Zn(21−3TFA)](ClO4)2 Complex (27). Compound 21 (105.8 mg,
0.130 mmol) and Zn(ClO4)2·6H2O (48.5 mg, 0.130 mmol) were
reacted according to general synthetic procedure D(ii) to give 27 as
a white powder (59.9 mg, 63%). m.p.: 109−114 °C. [α]D20: −2.6
(c 1.0, CH3CN). IR: νmax/cm−1 3574, 3266, 2937, 2881, 1736, 1694,
1540, 1457, 1428, 1367, 1302, 1224, 1082, 951, 879, 827, 623.
HRMS (ESI): 633.15390, 634.15766, 635.15024, 636.15331,
637.14900, 638.15167, 639.14659, 640.15012 ([M − ClO4]+). Calcd
for C20H38ClN8O7SZn ([M − ClO4]+): 633.15587, 634.15923,
635.15276, 636.15607, 637.15146, 638.15490, 639.14862, 640.15197.
Anal. Calcd for C20H38Cl2N8O11SZn: C, 32.69; H, 5.21; N, 15.25,
C20H38Cl2N8O11SZn·0.5H2O: C, 32.29; H, 5.28; N, 15.06. Found:
C, 32.34; H, 5.14; N, 15.07.
[Cu(33-3TFA)](ClO4)2 Complex (34). Compound 33 (84.0 mg,
0.0846 mmol) and Cu(ClO4)2·6H2O (31.3 mg, 0.0845 mmol) were
reacted according to general synthetic procedure D(iii) to give 34 as a
purple powder (63.0 mg, 82%). m.p.: 198−203 °C. UV−vis
(CH3CN): λmax/nm 572, ε 183. IR: νmax/cm−1 3591, 3339, 3298,
3234, 2964, 2881, 1733, 1694, 1647, 1541, 1463, 1363, 1222, 1068,
622. HRMS (ESI): 812.33537, 813.33973, 814.33310, 815.33743,
816.33107, 817.33528, 818.33885 ([M − ClO4]+). Calcd for
C31H58ClCuN10O9 ([M − ClO4]+): 812.33673, 813.34001,
814.33501, 815.33821, 816.33215, 817.33534, 818.33867. Anal.
Calcd for C31H58Cl2CuN10O13·H2O: C, 39.98; H, 6.49; N, 15.04.
Found: C, 39.90; H, 6.47; N, 14.94.
(S)-Methyl-2-((S)-2-((S)-2-(2-azidoacetamido)-3-methylbuta-
namido)-3-methylbutanamido)-3-methylbutanoate (31). To a
solution of azide-capped trivaline 30 (159 mg, 0.399 mmol) in
anhydrous methanol (5 mL) was added thionyl chloride (30 μL, 0.413
mmol) dropwise. The reaction mixture was heated at reflux for 6 h and
purified by preparative HPLC (gradient 0% to 50% B over 45 min) to
give 31 as a white solid (83 mg, 50%). RF (CH2Cl2/CH3OH = 95:5):
0.30. m.p.: 207−209 °C. [α]D20: −41.0 (c 1.0, DMSO). IR: νmax/cm−1
3281, 3077, 2962, 2102, 1736, 1668, 1632, 1542, 1432, 1382, 1286,
1
1204, 1143, 1090, 993, 931, 903, 847, 799, 694, 589, 559. H NMR
(400 MHz, (CD3)2SO): δ 0.78−0.88 (m, 18H, 3 × CH(CH3)2),
1.89−1.98 (m, 2H, 2 × CH(CH3)2), 1.98−2.07 (m, 1H, CH(CH3)2),
12828
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[Ni(33-3TFA)](ClO4)2 Complex (35). Compound 33 (137 mg,
0.138 mmol) and Ni(ClO4)2·6H2O (50.5 mg, 0.138 mmol) were
reacted according to general synthetic procedure D(iii) to give 35 as a
pink powder (96 mg, 77%). m.p.: 218−220 °C. [α]D20: −12.0 (c 1.0,
CH3CN). UV−vis (CH3CN): λmax/nm 502, ε 9. IR: νmax/cm−1 3505,
3272, 3084, 2965, 2928, 2878, 1736, 1645, 1542, 1462, 1369, 1312,
1220, 1080, 623. HRMS (ESI): 807.34370, 808.34715, 809.34073,
810.34438, 811.33663, 812.34097, 813.33370 ([M − ClO4]+). Calcd
for C31H58ClN10NiO9 ([M − ClO4]+): 807.34248, 808.34576,
809.33834, 810.34131, 811.33518, 812.33833, 813.33258. Anal.
Calcd for C31H58Cl2N10NiO13: C, 40.99; H, 6.44; N, 15.42. Found:
C, 40.70; H, 6.58; N, 15.18.
[Zn(33-3TFA)](ClO4)2 Complex (36). Compound 33 (122 mg,
0.123 mmol) and Zn(ClO4)2·6H2O (45.8 mg, 0.123 mmol) were
reacted according to general synthetic procedure D(iii) to give 36 as a
white powder (86 mg, 76%). m.p.: 174−176 °C. [α]D20: −23.0 (c 1.0,
CH3CN). IR: νmax/cm−1 3531, 3276, 3083, 2965, 2935, 2880, 1735,
1649, 1543, 1463, 1369, 1274, 1220, 1088, 624. HRMS (ESI):
813.33666, 814.34013, 815.33439, 816.33744, 817.33358, 818.33592,
819.33214, 820.33369, 821.33396 ([M − ClO4]+). Calcd for
C31H58ClN10O9Zn ([M − ClO4]+): 813.33627, 814.33958,
815.33335, 816.33646, 817.33206, 818.33527, 819.32914, 820.33239,
821.33572. Anal. Calcd for C31H58Cl2N10O13Zn·1.5H2O: C, 39.52; H,
6.53; N, 14.87. Found: C, 39.51; H, 6.55; N, 14.84.
Cell Culture. Breast cancer cell lines MDA-MB-231 and BT-474
were cultured in phenol red free DMEM/F12 (1:1; Invitrogen)
supplemented with 10% heat inactivated fetal bovine serum (FBS,
Invitrogen). The nonmalignant breast cell line MCF-10A was cultured
in phenol red free DMEM/F12 (1:1) supplemented with 5% horse
serum (Invitrogen), 20 ng/mL Epidermal Growth Factor (EGF)
(Peprotech), 500 ng/mL hydrocortisone (Sigma-Aldrich), 0.01 mg/
mL bovine insulin (Sigma-Aldrich), and 100 ng/mL cholera toxin
(Sigma-Aldrich). Pancreatic cancer cell lines BxPC-3, PANC-1, and
SU.86.86 were cultured in RPMI-1640 media (Invitrogen) supple-
mented with HEPES (25 mM; Invitrogen) and 10% FBS. Prostate
cancer cell lines LNCaP and PC-3 were maintained in RPMI-1640
supplemented with 10% FBS, and the control RWPE-1 cells were
maintained in Keratinocyte Serum Free Media (KSFM, Gibco)
supplemented with 20 mg/mL bovine pituitary extract (BPE) and
2 ng/mL epidermal growth factor EGF. All cancer cell lines
were purchased from the ATCC and maintained under standard cell
culture conditions (5% CO2, 37 °C, 95% humidity). The normal human
embryonic kidney cell line, HEK-293, was grown in DMEM plus 2 mM
Glutamax (Invitrogen) supplemented with 10% FBS and incubated under
standard cell culture conditions (as above).
Cell Viability Assay. Cells were seeded at appropriate densities
according to their respective growth rates in 384-well black/clear tissue
culture treated plates (Falcon, BD Biosciences) in 45 μL of culture
medium using a multidrop liquid handler (Thermo Scientific) and
were allowed to adhere overnight under standard cell culture
conditions (5% CO2, 37 °C, 95% humidity). Compounds at 10 mM
concentrations were diluted 25-fold in sterile MilliQ water, yielding
400 μM compound stocks with a DMSO (Sigma-Aldrich) level of 4%;
these solutions were further diluted with 4% DMSO to give 200, 100,
50, and 25 μM concentrations. Compound was added to each well to
give final screening concentrations of 40 μM, 20 μM, 10 μM, and
1 μM at 0.4% DMSO for the respective cancer cell lines or 40 μM,
20 μM, 10 μM, 5 μM, and 2.5 μM for the HEK-293 cell line.
Intermediate and final plate dilutions were freshly prepared on the day
of every screen using the Bravo (Agilent) robotic liquid handling
system. Appropriate positive (>10% DMSO or 20 μM Puromycin)
and negative (0.4% DMSO) controls were included for each plate, in
addition to a serial dose response of a reference compound
(Puromycin (Sigma Aldrich)) for determination of IC50. The plates
were incubated for 72 h (37 °C, 5% CO2 and 95% humidity). For the
cancer cell lines, Resazurin (Sigma-Aldrich) was added to a final
concentration of 600 μM per well and incubated for 4 h before a
measurement of fluorescent intensity was recorded on a Perkin-Elmer
EnVision at 530/595 nm. For the HEK-293 cell line, the supernatant
was removed after incubation, and 40 μL of 10% Presto Blue substrate
(Sigma Aldrich) in DMEM plus 2 mM Glutamax was added to each
well. The plates were incubated for a further 3 h and measured on the
Perkin-Elmer EnVision at 530/595 nm. The percent inhibition of
growth was calculated in relation to the maximum and minimum
inhibition of fluorescence caused by >10% DMSO or 20 μM
Puromycin (100% inhibition) and 0.4% DMSO (no inhibition). All
experiments were performed in triplicate, n = 3.
RESULTS AND DISCUSSION
■
The synthesis of cyclam scorpionand conjugates bearing
pendant amino acids requires a synthetic route and conditions
that are compatible with amide bonds. To evaluate the viability
of our proposed approach, a model compound (7, Scheme 1)
was first synthesized with a pendant N-benzylamide sub-
stituent. Azidoacetic acid (2)30,31 and propargyl-tri-Boc cyclam
(4)32,33 were synthesized according to literature procedures.
Amide coupling of benzylamine to the acid was followed by
copper(I)-catalyzed cycloaddition to give the triazole (5) in
84% yield.
Preparation of azamacrocycles containing pendant groups
using a Boc strategy requires the eventual removal of the Boc
groups and basification to recover the free amine ligand.
Removal of the Boc groups from 5 with 20% trifluoroacetic acid
in DCM24,34 frequently led to the formation of tert-butylated
products; use of water or TIS (at 5%, either individually or in
combination) as additives suppressed this. Removal of TIS
could be effected by dissolution of the residue in water and
washing with hexane, but in general the purity of the products
and the stability of the isolated samples were optimal when
water was the only additive, i.e., when the removal of the Boc
groups was effected with 90:5:5 TFA/DCM/H2O in which the
typical protected substrate concentration was 5 mM (concen-
trations of 20−50 mM gave poorer results). While we have no
direct evidence here of the formation of salts via combination
with three (rather than four) equivalents of trifluoroacetic acid,
we do have experimental evidence of this stoichiometry for
related compounds that will be reported in due course; three
equivalents have been presumed previously by us24 and
others.35 Isolation of the free amine ligand 7 was achieved by
basification with 5 M KOH or 2 M NaOH24 and extraction
with CHCl3 in quantitative yield and >98% purity (determined
by analytical HPLC) without further purification.
The click reaction generates an aromatic triazole ring that
1
alters the acidity of the surrounding protons. The H NMR
spectrum of 7 showed H/D exchange at the methylene position
derived from the azidoacetic acid (Figure 1). A decrease in the
intensity of this signal (at 5.19 ppm) was clear after a few hours
at room temperature and was essentially complete after one week
in deuterated methanol. In contrast, no such exchange was visible
for compound 3, containing protons in a similar chemical
environment but in the absence of the triazole. This increased
acidity has important implications for the biological evaluation of
related click-derived compounds in which this position adjacent
to the triazole contains stereochemical information.36,37
The stoichiometry of complexation between Cu(II) and free
amine ligand 7 was determined. A Job’s plot38 of absorbance at
570 nm vs the mole fraction of the ligand unequivocally
verified the stoichiometric ratio of 7/Cu(ClO4)2 to be 1:1
(Figure 2a), consistent with the results of a UV−visible
spectrophotometric titration (Figure 2b). The absorbance at
570 nm in the titration spectra rose with the addition of
Cu(ClO4)2 and reached the maximum value upon addition of
one equivalent of metal salt.
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a
Scheme 1. Synthesis of Model Compound 7 and Its Copper Complexes
a
Reagents and conditions: (a) NaN3, H2O, rt, O/N. (b) Benzylamine, EDC·HCl, HOBt, DIPEA, DCM, rt, O/N. (c) CuSO4·5H2O, sodium ascorbate,
H2O/t-BuOH, rt, O/N. (d) TFA/DCM/H2O (90:5:5), 6 h. (e) 5 M KOH or 2 M NaOH. (f) Cu(ClO4)2·6H2O, EtOH, reflux, 1 h. (g) KPF6,
MeOH/H2O.
Figure 1. Hydrogen/deuterium exchange in CD3OD at the methylene center between triazole and amide in 7.
Bulk reaction of 7 with Cu(ClO4)2 in EtOH gave an isolable
sample of 8. Data obtained for this compound included intense
infrared absorption bands at 1065 and 622 cm−1, indicating
the presence of perchlorate anion and a cluster of peaks with
the correct isotope pattern at m/z 590−596 ([8-ClO4]+) in the
high resolution mass spectrum; these results were further
supported by elemental analysis data. Attempts were made to
crystallize 8 using standard techniques (slow evaporation, slow
cooling, vapor diffusion, liquid−liquid diffusion), but these
failed, leading us to investigate counterion metathesis. Saturated
aqueous solutions of potassium hexafluorophosphate or
chloride were added to methanolic solutions of 8, followed
by slow evaporation, giving in the former case dark blue crystals
suitable for X-ray crystallography (Figure 3). [Formula,
C22H36CuF12N8OP2; M, 782.07; monoclinic; space group
P21/n (#14); a = 9.4510(10), b = 21.342(2), c = 15.342(2)
Å; β = 95.2370(10); V = 3081.6(6) Å3; Dc = 1.686 g cm−3;
Z = 4; crystal size 0.43 × 0.19 × 0.17 mm; color dark blue;
habit prism; temperature 150(2) K; λ(Mo Ka) 0.71073 Å;
μ(Mo Ka) 0.919 mm−1; T(SADABS)min,max = 0.776, 0.859;
2θmax 56.6; hkl range −12 +12, −27 +27, −20 +20; N, 29752;
Nind, 7428(Rmerge = 0.0229); Nobs, 5989(I > 2σ(I)); Nvar., 457;
residuals* R1(F), 0.0465; wR2(F2), 0.1323; GoF(all), 1.030;
Δρmin,max = −0.649, 0.875 e− Å−3. *R1 = ∑||Fo| − |Fc||/∑|Fo|
for Fo > 2σ(Fo); wR2 = (∑w(Fo − Fc2)2/∑(wFc2)2)1/2 all
2
reflections w = 1/[σ2(Fo ) + (0.0641P)2 + 4.7151P] where P =
2
2
(Fo + 2Fc2)/3.]
The complexation of ligand 7 with Ni(ClO4)2 or Zn(ClO4)2
yielded the corresponding complexes as pink and white
powders, respectively. The binding mode between ligand 7
1
and Zn(ClO4)2 was investigated by H NMR spectroscopy
(data not shown). 1H NMR titration of ligand 7 with sequential
addition of up to two equivalents of Zn(ClO4)2 in CD3OD
showed that the main proton signals became more and more
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Figure 2. (a) Job’s plot showing the 1:1 stoichiometry of the binding between ligand 7 and Cu(ClO4)2. (b) UV−vis spectrophotometric titration of
ligand 7 (1.6 μM) with Cu(ClO4)2 (160 μM) in MeOH at room temperature (inset: absorbance at 570 nm vs equivalents of Cu(ClO4)2 added).
Figure 3. An ORTEP plot of the cation 9 at the 50% probability level. The hexafluorophosphate anions are omitted for clarity. Selected bond lengths
(Å) and angles (deg): Cu(1)−N(1), 2.051(2); Cu(1)−N(2), 2.017(3); Cu(1)−N(3), 1.992(3); Cu(1)−N(4), 2.032(2); Cu(1)−N(5), 2.203(2);
N(1)−Cu(1)−N(2), 87.77(12); N(1)−Cu(1)−N(3), 179.06(10); N(1)−Cu(1)−N(4), 93.41(10); N(1)−Cu(1)−N(5), 79.60(9); N(2)−Cu(1)−
N(3), 92.61(13); N(2)−Cu(1)−N(4), 153.71(11); N(2)−Cu(1)−N(5), 103.63(10); N(3)−Cu(1)−N(4), 86.64(11); N(3)−Cu(1)−N(5),
99.47(9); N(4)−Cu(1)−N(5), 102.41(10). Bond lengths are typical for this kind of complex.24
complex and underwent downfield shifts upon addition of up to
one equivalent of Zn(ClO4)2, and further addition of
Zn(ClO4)2 did not result in any appreciable changes, indicating
1:1 stoichiometry of the binding between ligand 7 and
Zn(ClO4)2, as for the copper salt. All of the well-defined
complex also gave a multiplication of signals vs the free ligand,
particularly in the aliphatic regions 20−30 and 40−65 ppm,
implying that the metal chelation increases the rigidity of the
ligand so the carbons in [Zn(7)](ClO4)2 become magnetically
inequivalent (particularly those in the macrocyclic ring).
The synthetic route to the model compound described above
was adapted to the synthesis of metal-cyclam complexes
functionalized with the amino acids phenylalanine, valine, and
tryptophan (Scheme 2).
Successful deployment of the click reaction in these
syntheses requires that the click reaction conditions do not
compromise the stereochemical integrity of the amino acids. To
verify this, (S)-10i and rac-10i were synthesized from (S)-
phenylalanine methyl ester and the racemate, respectively, and
analyzed by enantioselective HPLC. The chromatograms
1
signals in the H NMR spectrum of ligand 7 were split into
unresolvable multiplets in the corresponding spectrum of
[Zn(7)](ClO4)2, except the benzyl group signals, suggesting
that all four nitrogen donors on cyclam and a nitrogen atom on
the triazole ring are involved in the chelation of ligand 7 with
Zn(ClO4)2. The singlet arising from the triazole H in ligand 7
changed to three separate peaks in the spectrum of purified
[Zn(7)](ClO4)2 (Supporting Information), suggesting the
presence of three different diastereomers of the metal
complex.39 The 13C NMR spectrum of the [Zn(7)](ClO4)2
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a
Scheme 2. Synthesis of Metal−Cyclam Complexes Functionalized with Amino Acids
a
Reagents and conditions: (a) 10i and 10ii: TFA/DCM/H2O (90:5:5), rt, 6 h. 10iii: TFA/EDT/H2O (90:5:5), rt, 2 h, followed by RP-HPLC
purification. (b) Saturated Na2CO3, pH 11−12. (c) M(ClO4)2·6H2O, EtOH, reflux, 1 h.
(Supporting Information) showed a single signal for (S)-10i,
two signals of equal area for rac-10i, and two signals in a 3:1
ratio for the coinjection of a 1:1 mixture of (S)-10i and rac-10i,
which unambiguously demonstrated that the conditions
employed in this step do not lead to any measurable
epimerization.
Cysteine was chosen as an amino acid that presents more
challenging synthetic issues, arising from the nucleophilicity
and coordinating ability of the thiol side chain and the tendency
of this group to form disulfides under oxidative conditions.
para-Methoxybenzyl-protected cysteine was coupled with
azidoacetic acid to give 16 (Scheme 3), and the corresponding
disulfide (17) was made by esterification of cystine followed by
amide bond formation with azidoacetic acid. Both of these
azides underwent the Cu(I)-catalyzed cycloaddition smoothly
to yield protected cyclam conjugates in good yields. The route
employing the disulfide 18 was not carried further because it
was found that the cyclam in the protected derivative 19 could
be deprotected orthogonally to or along with the PMB-
protected thiol, to give 20 or 21, respectively. Ligand 21 was
isolated as its trifluoroacetate salt because attempts to isolate
the free ligand led to the formation of a byproduct presumed to
be the disulfide.
Initial attempts to synthesize metal complexes using 12i−iii
in methanol led to difficulties in bulk purification since the
starting materials (free amine ligands and metal perchlorates)
and the resultant metal complexes are all methanol-soluble.
This problem was solved by using ethanol instead since it was
found that the copper(II) and zinc(II) complexes are ethanol-
insoluble, allowing them to be isolated as precipitates in good
yields. The nickel(II) complexes are slightly soluble in ethanol
and were therefore obtained in slightly lower yields. Insertion of
metal salts into the PMB-protected cysteine derivative 20 gave
the expected complexes, as did the complexation of thiol 21
with Ni(II) and Zn(II). In the case of Cu(II), however, reaction
of one equivalent of the copper salt with 21 gave 83% of the
Cu(II)−disulfide complex 25, a result which implies the
involvement of atmospheric oxygen (the reaction of 21 with
Cu(II) was conducted at reflux and open to the air).42 The
synthesis of complexes 25−27 was achieved directly from the
TFA salt 21 and required an extended reaction time. The purity
of all of the metal complexes was confirmed by elemental
analysis.
Removal of Boc groups from 10i and 10ii was achieved using
TFA/DCM/H2O (90:5:5) to afford the water-soluble salts 11i
and 11ii in good to excellent yields and high purities, whereas
application of this deprotection procedure to 10iii failed to give
pure trifluoroacetate salt 11iii. Signals in the mass spectrum of
the crude product from this latter reaction (m/z = 596.5 [MH +
56]+, 652.5 [MH + (56 × 2)]+, and 708.7 [MH + (56 × 3)]+)
and the appearance of new peaks in the analytical HPLC trace
corresponding to compounds less polar than the expected
product suggested the attachment of between one and three
tert-butyl groups to the ligand. This indicated that the water
included as a scavenger in the deprotection mixture was not an
effective quencher for the tert-butyl cation in the presence of an
indole nucleophile. Substitution of 5% DCM with 5%
triisopropylsilane (TIS) in the deprotection cocktail resulted
in reduction of the indole ring (indicated by a signal at m/z =
542.5 ([MH + 2]+) in the mass spectrum), a side reaction
consistent with previous observations that triethylsilane/TFA
can reduce the indole ring of tryptophan.40 Replacement of 5%
DCM with 5% 1,2-ethanedithiol (EDT) gave satisfactory
deprotection. Prior to purification by preparative chromatog-
raphy, the malodorous EDT could be easily removed by
dissolution of the residue in water and washing with chloroform;
EDT removal was assayed by monitoring the organic washes
with PdCl2 reagent (0.5% aq. PdCl2 containing a few drops of
conc. HCl)41 since sulfur-containing compounds give a yellow
color when stained with this reagent.
Basification of 11i−iii to give the corresponding free amine
depended greatly on the base used. The addition of sodium
hydroxide (2 M) or sodium hydrogen carbonate (saturated)
solutions, both of which had been used in previous studies,24,34
resulted in either cleavage of the methyl ester (indicated by a
signal at m/z [MH − 14]+ in the mass spectrum) or
incomplete removal of trifluoroacetate counterions from the
ligands, respectively. Successful isolation of the pure amine
ligands was achieved by basification to pH 11−12 with
saturated aqueous sodium carbonate solution and extraction
with chloroform.
Of these complexes, only compound 14ii gave crystals
suitable for X-ray diffraction, grown via dissolution of the
complex in acetonitrile and forced evaporation under a stream
of nitrogen (Figure 4). [Formula, C21H40Cl2N8NiO11; M,
710.22; monoclinic; space group, P21 (#4); a = 10.9527(5), b =
8.6360(4), c = 16.0493(6) Å; β = 95.490(2); V = 1511.10(11) Å3;
Dc = 1.561 g cm−3; Z = 2; crystal size, 0.275 × 0.077 × 0.060 mm;
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a
Scheme 3. Synthesis of Metal−Cyclam Complexes Functionalized with Cysteine
a
Reagents and conditions: (a) 4, CuSO4·5H2O, sodium ascorbate, H2O/t-BuOH, rt, O/N. (b) TFA/DCM/H2O (90:5:5), rt, 6 h, followed by RP-
HPLC purification. (c) Saturated Na2CO3, pH 11-12. (d) TFA, anisole, Ar, reflux, 1.5 h, followed by RP-HPLC purification. (e) M(ClO4)2·6H2O,
EtOH, reflux, 1 h. (f) as for (e) except for 3 h reaction time.
a
Scheme 4. Synthesis of Metal−Cyclam Complexes Functionalized with a Tripeptide
a
Reagents and conditions: (a) 2-azidoacetic acid, PyBOP, NMM, DMF. (b) TFA/TIS/H2O (90:5:5), rt, 2 h. (c) SOCl2, MeOH, reflux, 6 h. (d) 4,
CuSO4·5H2O, sodium ascorbate, H2O/t-BuOH, rt, O/N. (e) TFA/DCM/H2O (90:5:5), rt, 6 h; (f) M(ClO4)2·6H2O (M = Cu, Ni, Zn), EtOH, reflux, 6 h.
color pink; habit rod; temperature 150(2) K; λ(Mo Kα), 0.71069 Å;
μ(MoKα), 0.888 mm−1; T(SADABS)min,max = 0.850, 1.000;
2θmax, 67.3; hkl range −16 +17, −10 +13, −25 +24; N, 37588;
Nind, 9963(Rmerge 0.0281); Nobs, 8282(I > 2σ(I)); Nvar., 380;
12833
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Figure 4. An ORTEP plot of the cation 14ii at the 50% probability level. The noncoordinated perchlorate anion and minor disordered component of
the coordinated perchlorate anion are omitted for clarity. Selected bond lengths (Å) and angles (deg): Ni(1)−N(1), 2.159(2); Ni(1)−N(2),
2.101(2); Ni(1)−N(3), 2.079(2); Ni(1)−N(4), 2.0881(19); Ni(1)−N(5), 2.0691(19); Ni(1)−O(11A), 2.2501(16); Ni(1)−O(11B), 2.1150(14);
N(1)−Ni(1)−N(2), 91.55(8); N(1)−Ni(1)−N(3), 174.80(8); N(1)−Ni(1)−N(4), 85.39(8); N(1)−Ni(1)−N(5), 81.18(7); N(1)−Ni(1)−
O(11A), 89.01(8); N(1)−Ni(1)−O(11B), 101.32(9); N(2)−Ni(1)−N(3), 84.64(9); N(2)−Ni(1)−N(4), 97.19(7); N(2)−Ni(1)−N(5),
170.12(8); N(2)−Ni(1)−O(11A), 83.94(7); N(2)−Ni(1)−O(11B), 88.55(9); N(3)−Ni(1)−N(4), 91.57(8); N(3)−Ni(1)−N(5), 103.02(8);
N(3)−Ni(1)−O(11A), 94.10(8); N(3)−Ni(1)−O(11B), 82.16(9); N(4)−Ni(1)−N(5), 88.92(8); N(4)−Ni(1)−O(11A), 174.30(7); N(4)−
Ni(1)−O(11B), 171.09(9); N(5)−Ni(1)−O(11A), 89.23(7); N(5)−Ni(1)−O(11B), 86.36(9); O(11A)−Ni(1)−O(11B), 13.25(8). The bond
length between metal center and N donor (2.069 Å) is longer than that seen in a comparable complex (2.044 Å) where there is less steric crowding
around the metal43 but shorter than comparable azamacrocyclic complexes based on scorpionand pyridine donors (2.107 Å).44.
residuals* R1(F), 0.0407; wR2(F2), 0.1145; GoF(all), 1.056;
Δρmin,max, −0.674, 0.903 e− Å−3. *R1 = ∑||Fo| − |Fc||/
amino acids.47 The metabolic stability of metal-bearing ligands
is naturally dependent on the specific coordination environ-
ment employed.48 However, attachment of metal complexes to
a peptide can have dramatic effects on the cellular fate of that
peptide.49,50 In this context, the biological activity of the
present compounds was assayed against normal human
embryonic kidney cells (HEK-293) in triplicate in the range
2.5−40 μM for 3 days. Cell death/viability was measured with
Presto Blue, indicating that none of the metal complexes
exhibited any cytotoxicity at the doses tested (Supporting
Information). The complexes were also assayed against
pancreatic (BxPC-3, PANC-1 and SU.86.86), breast (BT-474,
MDA-MB-231, MCF-10A (control)), and prostate (LNCaP,
PC-3 and RWPE-1 (control)) cancer cell lines. Essentially all
compounds were also found to be nontoxic in these cases. The
single exception was the disulfide copper complex 25, which
showed moderate activity against MCF-10A breast non-
tumorigenic epithelial cells.
The results described in this paper suggest the following: (1)
Azamacrocyclic complexes bearing amino acid or peptide-based
groups may be easily synthesized using click methods, and such
an approach offers an attractive alternative to more traditional
conjugation techniques. (2) Metal insertion into these
conjugates is rapid and proceeds with well-defined stoichiome-
tries. (3) The syntheses do not lead to epimerization of the
amino acid stereocenters, but care must be taken if complexes
involve stereocenters between triazole rings and adjacent
carbonyl groups. (4) A range of amino acids and a tripeptide
have been shown to be compatible with the chemistry, and it is
expected that longer polypeptides and other amino acids will be
similarly compatible. (5) The ligands and their complexes are
∑|Fo| for Fo > 2σ(Fo); wR2 = (∑w(Fo2 − Fc2)2/∑(wFc2)2)1/2
;
all reflections w = 1/[σ2(Fo ) + (0.0674P)2 + 0.0154P] where
2
2
P = (Fo + 2Fc2)/3.]
To extend the approach, we utilized these procedures to
construct metal−cyclam complexes with an oligopeptide arm.
First, an azide-capped tripeptide 30 (Scheme 4) was assem-
bled via Fmoc solid phase peptide synthesis (Supporting
Information).
The tripeptide was cleaved from the solid support after the
synthesis of 29, rather than continuing the synthesis on the
solid phase. While it is possible to use solid supports with
linkers designed to generate esters of cleaved materials,45 initial
experiments with methanolysis of 29 anchored instead to
HMBA resin gave complex mixtures of products, and these
results were inferior to those obtained by solution phase
esterification of tripeptide acid 30. The desired azide-capped
tripeptide 30 was released from the resin in excellent overall
yield and with >95% purity by analytical HPLC. Esterification
of 30 was effected in MeOH in the presence of thionyl chloride,
followed by click reaction and acidolytic deprotection to give
the corresponding trifluoroacetate salt 33, which was not
basified to recover the free amine ligand but directly complexed
with metal perchlorates using an extended reaction time (six
hours) to afford trivaline-functionalized metal-cyclam com-
plexes 34−36. The complexes could be isolated with
centrifugation, a convenient protocol that we expect will be
applicable to a wide range of cyclam−peptide metal complexes.
Azamacrocyclic complexes bearing triazole-linked dyes are
bioavailable,34,46 as are azamacrocyclic complexes bearing single
12834
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(17) Mindt, T. L.; Struthers, H.; Brans, L.; Anguelov, T.;
nontoxic to a range of cell types, and concentrations up to
40 μM, suggesting that labeled complexes of this general design
could be useful tools for imaging and therapeutic applications.
Schweinsberg, C.; Maes, V.; Tourwe,
Soc. 2006, 128, 15096−15097.
(18) Wadas, T. J.; Wong, E. H.; Weisman, G. R.; Anderson, C. J.
Chem. Rev. 2010, 110, 2858−2902.
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D.; Schibli, R. J. Am. Chem.
ASSOCIATED CONTENT
(19) Tweedle, M. F. Acc. Chem. Res. 2009, 42, 958−968.
(20) Major, J. L.; Meade, T. J. Acc. Chem. Res. 2009, 42, 893−903.
(21) Liu, S. Adv. Drug Delivery Rev. 2008, 60, 1347−1370.
(22) Cowley, A. R.; Dilworth, J. R.; Donnelly, P. S.; Heslop, J. M.;
Ratcliffe, S. J. Dalton Trans. 2007, 209−217.
(23) Mizukami, S.; Takikawa, R.; Sugihara, F.; Shirakawa, M.;
Kikuchi, K. Angew. Chem., Int. Ed. 2009, 48, 3641−3643.
(24) Tamanini, E.; Rigby, S. E. J.; Motevalli, M.; Todd, M. H.;
Watkinson, M. Chem.Eur. J. 2009, 15, 3720−3728.
(25) Lattuada, L.; Gabellini, M. Synth. Commun. 2005, 35, 2409−
2413.
■
S
* Supporting Information
Experimental descriptions of the syntheses of known
compounds and all solid phase procedures. Scans of H and
1
13C NMR spectra for all novel compounds, including Zn(II)
complexes. HPLC data for epimerization experiments.
Crystallographic information for compounds 9 and 14ii.
HRMS for all amino acid and peptide metal complexes
compared to simulated spectra. Bioactivity data from
compound screens. This material is available free of charge
via the Internet at http://pubs.acs.org.
(26) Kunstler, J.-U.; Seidel, G.; Pietzsch, H.-J. Appl. Radiat. Isot.
2010, 68, 1728−1733.
(27) Bowen, M. L.; Orvig, C. Chem. Commun. 2008, 5077−5091.
(28) Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless, K. B.
Angew. Chem., Int. Ed. 2002, 41, 2596−2599.
AUTHOR INFORMATION
■
Corresponding Author
(29) Lau, Y. H.; Price, J. R.; Todd, M. H.; Rutledge, P. J. Chem.
*E-mail: matthew.todd@sydney.edu.au.
Eur. J. 2011, 17, 2850−2858.
(30) Cai, J.; Li, X.; Yue, X.; Taylor, J. S. J. Am. Chem. Soc. 2004, 126,
16324−16325.
ACKNOWLEDGMENTS
■
(31) Banaszynski, L. A.; Liu, C. W.; Wandless, T. J. J. Am. Chem. Soc.
2005, 127, 4715−4721.
We thank The University of Sydney for a scholarship (USydIS,
to M.Y.). We thank Professor Len Lindoy (The University of
Sydney) and Dr Mike Watkinson (Queen Mary, University of
London) for helpful comments. This work was supported by a
National Breast Cancer Foundation Novel Concept Award
(NC-10-69).
(32) Fabbrizzi, L.; Foti, F.; Licchelli, M.; Maccarini, P. M.; Sacchi, D.;
Zema, M. Chem.Eur. J. 2002, 8, 4965−4972.
(33) Lo, A. T. S.; Salam, N. K.; Hibbs, D. E.; Rutledge, P. J.; Todd,
M. H. PLoS One 2011, 6, e17446.
(34) Tamanini, E.; Katewa, A.; Sedger, L. M.; Todd, M. H.;
Watkinson, M. Inorg. Chem. 2009, 48, 319−324.
(35) Ritter, S. C.; Eiblmaier, M.; Michlova, V.; Konig, B. Tetrahedron
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