Synthesis and characterization of a triazine dendrimer that sequesters iron(III) using 12 desferrioxamine B groups

Article abstract of DOI:10.1016/j.bmc.2010.05.039

The synthesis of a third generation triazine dendrimer, 1, containing multiple, iron-sequestering desferrioxamine B (DFO) groups is described. Benzoylation of the hydroxamic acid groups of DFO and formation of a reactive dichlorotriazine provide the intermediate for reaction with the second generation dendrimer displaying twelve amines. This strategy further generalizes the 'functional monomer' approach to generate biologically active triazine dendrimers. Dendrimer 1 is prepared in seven steps in 35% overall yield and displays 12 DFO groups making it 56% drug by weight. Spectrophotometric titrations (UV-vis) show that 1 sequesters iron(III) atoms with neither cooperativity nor significant interference from the dendrimer backbone. Evidence from NMR spectroscopy and mass spectrometry reveals a limitation to this functional monomer approach: trace amounts of O-to-N acyl migration from the protected hydroxamic acids to the amine-terminated dendrimer occurs during the coupling step leading to N-benzoylated dendrimers displaying fewer than 12 DFO groups.

Full text of DOI:10.1016/j.bmc.2010.05.039

Bioorganic & Medicinal Chemistry 18 (2010) 5749–5753
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and characterization of a triazine dendrimer that sequesters
iron(III) using 12 desferrioxamine B groups
*
Jongdoo Lim, Vincent J. Venditto, Eric E. Simanek
Department of Chemistry, Texas A&M University, College Station, TX 77843, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of a third generation triazine dendrimer, 1, containing multiple, iron-sequestering desfer-
rioxamine B (DFO) groups is described. Benzoylation of the hydroxamic acid groups of DFO and formation
of a reactive dichlorotriazine provide the intermediate for reaction with the second generation dendrimer
displaying twelve amines. This strategy further generalizes the ‘functional monomer’ approach to gener-
ate biologically active triazine dendrimers. Dendrimer 1 is prepared in seven steps in 35% overall yield
and displays 12 DFO groups making it 56% drug by weight. Spectrophotometric titrations (UV–vis) show
that 1 sequesters iron(III) atoms with neither cooperativity nor significant interference from the dendri-
mer backbone. Evidence from NMR spectroscopy and mass spectrometry reveals a limitation to this func-
tional monomer approach: trace amounts of O-to-N acyl migration from the protected hydroxamic acids
to the amine-terminated dendrimer occurs during the coupling step leading to N-benzoylated dendri-
mers displaying fewer than 12 DFO groups.
Received 14 April 2010
Revised 12 May 2010
Accepted 14 May 2010
Available online 20 May 2010
Keywords:
Dendrimer
Iron overload
DFO
Chelation
Polymer
Synthesis
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
oxamine, or DesferalÒ), deferiprone (FerriproxÒ), and deferasirox
(ExjadeÒ).6 Desferrioxamine B (DFO) is the most studied and suc-
While an essential element for normal cellular metabolism and
respiration, excess levels of iron in the body are cytotoxic and fatal
if left untreated.1 Iron absorption from the gut and transport
throughout the body involves a complex pathway of proteins
which is not fully understood.2 The body has no active iron excre-
tion system, but desquamation, menstruation, and other mecha-
nisms for blood loss aid in maintaining iron homeostasis.1a,3 The
accumulation of excess iron in tissues occurs in patients with
hereditary hemochromatosis, a condition that derives from a ge-
netic mutation leading to abnormally increased iron absorption
in the intestines. Diseases requiring frequent blood transfusions
also result in excess iron including b-thalassemia major, sickle cell
disease, myelodysplastic syndrome, and Fanconi anemia.4 Iron
overload is the most common, chronic metal toxicity condition
worldwide with the highest morbidity and mortality rate.5 Accord-
ingly, chelating agents have been employed successfully to treat
iron overload disorders.
cessful iron(III) chelating agent since its isolation from Streptomy-
ces pilosus in the early 1960s.7 DFO is orally ineffective and has
short plasma half-life (5–10 min for DFO and 90 min for its iron
complex), thus requiring slow intravenous or subcutaneous infu-
sion over 8–12 h at dose of 25–50 mg/kg/d for 5–7 days/week dur-
ing treatment.7a Poor patient compliance has generated interest in
the development of iron sequestration agents that are either orally
active or show extended circulation times.
Accordingly, macromolecular constructs capable of iron seques-
tration have been investigated to prolong the plasma half-life and
reduce the toxicity associated with some small molecule chelates.
Such architectures include polysaccharide polymers such as dex-
tran and hydroxyethyl starch containing 10–30 wt % DFO.8 These
constructs show promising in vivo data in mice with acute iron
poisoning.9 However, the poorly defined polymeric structure leads
to ambiguous evaluation of pharmacokinetic and pharmacody-
namic data. Other macromolecular iron-sequestering agents using
poly(ethylene glycol), salicylate, catecholate, and hydroxypyridi-
noate have been proposed to improve these drawbacks.10
These iron-sequestering agents actively remove excess iron
from the blood through renal filtration to urine and through biliary
drainage from hepatocytes into fecal matter.4b Several iron(III) spe-
cific chelation therapies have been explored to treat iron overload.
However, only three agents are approved by the FDA for preclinical
or clinical use: desferrioxamine B (also known as DFO, DFOB, defer-
Here, we prepare 1 by incorporating twelve DFO groups into a
second generation dendrimer 2 (R0 = H) that is available on kilo-
gram scale (Fig. 1).11 In addition to deriving from readily available
and inexpensive building blocks, these materials are amenable to
the rigorous characterization typically reserved for small mole-
cules and not normally suited to macromolecules. These materials
show surprising biocompatibility in acute dosing regimes.12 Here,
* Corresponding author. Tel.: +1 979 845 4242.
E-mail address: simanek@tamu.edu (E.E. Simanek).
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.05.039

5750
J. Lim et al. / Bioorg. Med. Chem. 18 (2010) 5749–5753
Figure 1. Dendrimer 1 derives from 2 and displays 12 DFO groups that form hexadentate complexes with Fe(III) using the groups shown in bold.
we pursue DFO constructs based on (i) interests in their intrinsic
biological activity and (ii) the opportunity they present to probe
the scope and limits of synthetic methods aimed at these targets.
DFO appears (and proves) to be markedly more complex from a
reactivity standpoint than either paclitaxel14 or camptothecin.
Accordingly, synthesis and evaluation of a proof-of-concept target
was undertaken.
avoided for fear of rapid O-to-N acyl migration. This reaction is
not observed and accordingly, the free amine can be reacted with
cyanuric chloride, a step that is central to the synthesis of these
dendrimers.18 The resulting dichlorotriazine 4—our functional
monomer—is reacted with 2 to yield the desired product 5. We ex-
pected this reaction to proceed without migration of benzoyl
groups from DFO to the dendrimer. However, SNAr reaction rates
are reduced by steric hindrance and evidence of benzoyl migration
is seen in trace amounts (vide infra). The synthesis concludes with
reaction of poly(monochlorotriazine) 5 with 4-piperidinemethanol
and hydrolysis of the O-acyl groups using a solution of methanol,
water, and triethylamine to yield 1. In summary, 1 is accessed from
2 in seven steps in 35% overall yield and contains 12 DFO groups
predominantly. Dendrimer 1 can be described as having high drug
loading: it is 56 wt % DFO, but not water soluble.
2. Results and discussion
We recently described an iterative route to dendrimer synthesis
wherein three reactions were required to complete a generation.13
To functionalize these dendrimers, two different strategies have
been pursued. The ‘functional monomer’ approach relies on the
incorporation of the drug of interest into a reactive dichlorotri-
azine. This strategy has been used successfully to introduce
paclitaxel onto triazine dendrimers.14 Alternatively, the ‘functional
cap’ strategy relies on elaboration of the dendrimer to yield a reac-
tive poly(chlorotriazine) to which the drug with pendant nucleo-
phile is incorporated. We recently showed that an isonipecotic
ester of camptothecin could be incorporated into dendrimers in
this way.15
Our initial efforts to directly react the amine nucleophile of DFO
with cyanuric chloride failed due to the nucleophilicity of the
hydroxamic acid groups. The result of these reactions are macrocy-
cles and insoluble material presumed to be polymeric. Protection
of the hydroxamic acids was first attempted using iron(III). DFO
shows high binding affinity for a variety of metals including Fe(III),
Al(III), and Ga(III) through the carbonyls and nucleophilic hydroxa-
mic acids.16 Reaction of DFO-Fe(III) complex with cyanuric chloride
generated a mixture of the desired dichlorotriazine product and
macrocyclic monochlorotriazines. The necessity to remove iron in
later steps—especially in light of its high iron-binding constant
(ꢀ1030) over a wide range of pH values17—combined with solubil-
ity challenges led us to pursue alternative strategies including a
‘functional cap’ strategy using an isonipecotic amide of DFO that
also failed. Ultimately, we adopted more conventional protection
strategies of the hydroxamic acid groups.
2.2. Characterization
1H and 13C NMR spectroscopy as well as MALDI-TOF MS are
used to follow all the reactions. For the low molecular weight
intermediates, 3 and 4, thin layer chromatography (TLC) is also
useful to monitor the spot-to-spot conversions of the compounds.
The complexity increases with dendrimers 5 and 1. MALDI-TOF MS
of 5 shows the product ion at m/z 14,762 and lines corresponding
to species missing approximately one to three dichlorotriazine
groups that could result either from incomplete SNAr reaction of
functional monomer 4 with 2, or from benzoyl migration.
As shown in Figure 2, the 1H NMR spectrum of 5 shows no clear
sign of incomplete reaction and/or the migration, but this is far
from definitive due to both spectral broadness and the limit of
detection of the technique. For example, the theoretical H number
of 5 is very close to the integration values. That is, the recorded
integral areas observed throughout the spectra match expectations
(indicated in parentheses) in the aromatic region (o-72H-Ph, p-
36H-Ph, and m-72H-Ph of benzoyl groups at d 8.05, 7.63, and
7.48 ppm, respectively), the aliphatic region populated by the den-
drimer (276H of G2 dendrimer and DFO at d 3.77–3.10 ppm), re-
gions unique to DFO (48Hs for both N(OBz)COCH2CH2 and
N(OBz)COCH2CH2 at d 2.64 and 2.47 ppm, respectively; 36H of
COCH3 at d 2.02 ppm), as well as regions associated with DFO
and dendrimer (306H of G2 dendrimer and DFO at d 1.75–
1.20 ppm). Details including specific assignments are available in
the Supplementary data.
2.1. Synthesis
The successful synthesis of the DFO-displaying dendrimer, 1, is
shown in Scheme 1. In order to improve the poor solubility of DFO
in organic solvents and suppress unwanted side reactions, the che-
lating agent is first masked with Boc and benzoyl groups. DFO mes-
ylate salt is reacted first with BOC anhydride in dioxane/water.
After subsequent installation of the benzoyl groups, the amine is
liberated with trifluoroacetic acid. This strategy was initially
The 1H NMR spectrum of the target, 1, shows lines in the aro-
matic region that integrate for less than 1 benzoyl group (Fig. 2).
An observed value of 2.3H (theoretically 3H for one benzoyl migra-
tion) of p- and m-H-Ph at d 7.58–7.38 ppm represents 0.77 benzoyl
groups. Accordingly, we approximate that each dendrimer displays

J. Lim et al. / Bioorg. Med. Chem. 18 (2010) 5749–5753
5751
OBz
O
O
O
OBz
N
O
O
O
N
N
H
N
N
H
N
1) TFA/DCM
H
O
O
OBz
NH
H
N
O
N
OBz
NHBoc
N
2) C3N3Cl3, DIPEA
THF, rt, 0 oC, 1 h
88% over 2 steps
N
OBz
O
OBz
3
N
N
N
4
Cl
Cl
2, DIPEA
THF/H2O
rt, 48 h
80%
OH
N
O
O
O
N
OBz
O
O
O
N
1) 4-piperinemethanol
DIPEA, THF, rt, 24 h
N
H
N
H
N
H
H
N
O
N
OH
NH
O
O
OBz
NH
2) CH3OH/H2O/TEA
rt, 24 h
74% over 2 steps
N
N
O
OH
OBz
N
N
N
N
N
5
1
HN 12
N
N
HN 12
Cl
OH
Scheme 1. Synthesis of 1 using the functional monomer approach with the dichlorotriazine intermediate 4.
Figure 2. 1H NMR spectra of 1 (500 MHz, DMSO-d6) and 5 (500 MHz, CDCl3).
Figure 3. UV–vis absorbance spectra of (a) the species of interest and (b) a titration plot of absorbance (kmax 442 nm) against [Fe3+]/[1] that is linear up to almost 12 mole
equivalents (black diamonds) before excess iron leads to no significant change (open diamonds).
on average 111 DFO groups. At this time, quantifying the exact
2.3. Chelation
4
distribution of these species is outside the scope of this work.
Although mass spectrometry suggests species that have undergone
up to three acyl transfer reactions, these materials clearly exist in
small amounts relative to 1.
Spectrophotometric titrations corroborate both this migration
and the ability of the dendrimer to behave as intended. Dendrimer
1, FeCl3 and the complex are dissolved in methanol and absorbance

5752
J. Lim et al. / Bioorg. Med. Chem. 18 (2010) 5749–5753
is measured at 25 °C (Fig. 3a). Stoichiometry is established by
titrating 27.8 M of 1 with twelve portions of 27.8 M of FeCl3
under vacuum. The residue was dissolved in dichloromethane,
washed with brine, dried over MgSO4, filtered, and evaporated un-
der vacuum. The crude product was purified by silica gel chroma-
tography (from hexane/EA = 1:1 to acetone/hexane = 1:1) to give 3
(0.80 g, 82%) as a white solid. 1H NMR (300 MHz, CDCl3) d 8.03 (m,
6H), 7.60 (m, 3H), 7.46 (m, 6H), 3.75 (br m, 6H), 3.14 (br m, 4H),
3.03 (br m, 2H), 2.62 (br, 4H), 2.45 (br m, 4H), 2.00 (s, 3H), 1.53
(br, 6H), 1.44 (br m, 6H), 1.36 (br, 15H); 13C NMR (75 MHz, CDCl3)
d 173.0, 171.7, 164.4, 156.0, 134.5, 130.0, 129.9, 128.9, 126.6,
126.5, 78.8, 47.7, 40.3, 39.2, 30.3, 29.5, 28.9, 28.4, 27.9, 27.7,
27.5, 26.6, 23.8, 23.5, 20.4; MS (MALDI-TOF) calcd for
l
l
as plotted with black diamonds in Figure 3b. The absorbance of
Fe(III)-dendrimer complex is linear up to 11 mole equivalents of
Fe(III): 1. After 12 equiv of Fe(III), the absorbance does not change
significantly (open diamonds). The extinction coefficient of the
complexed iron (III) is calculated as
kmax 442 nm. The linear relationship suggests that iron chelation
e
= 2.23 ꢁ 103 Mꢂ1 cmꢂ1 at
by this multivalent host is not cooperative.
3. Experimental section
3.1. General procedures
C
51H68Cl12N6O13 972.4844, found 973.3748 (M+H)+.
3.2.3. Intermediate 4
Dendrimer 2 was prepared as previously reported.11 All other
chemicals were purchased from Aldrich and Acros and used with-
out further purification. All solvents were ACS grade and used
without further purification. Diafiltration purification was per-
formed with Amicon stirred ultrafiltration cell equipment (Model
8050, PLCC membrane, Millipore Corp.) at 35 psi of N2. UV–vis
absorption spectra were obtained with SPECTRAmax Plus384
(Molecular Devices) and analyzed using SoftMax Pro v. 4.7.1.
NMR spectra were recorded on an Inova 300 or 500 MHz spectrom-
eter in CDCl3, CD3OD, or DMSO-d6. Mass spectrometry was carried
out by the Laboratory for Biological Mass Spectrometry at Texas
A&M University.
A solution of 3 (0.65 g, 0.668 mmol) in trifluoroacetic acid
(4 mL) and dichloromethane (8 mL) was stirred for 30 min at room
temperature. The solution was diluted with dichloromethane,
washed with brine, dried over MgSO4, filtered, and evaporated un-
der vacuum. The residue was dissolved in THF (30 mL). Cyanuric
chloride (0.13 g, 0.705 mmol) and DIPEA (0.3 mL, 1.71 mmol) was
added to the solution at 0 °C. The reaction solution was stirred
for 1 h at 0 °C and evaporated under vacuum. The residue was dis-
solved with dichloromethane, washed with brine, dried over
MgSO4, filtered, and evaporated under vacuum. The crude product
was purified by silica gel chromatography (acetone/hexane = 3:2)
to give 4 (0.60 g, 88% over two steps) as a white solid. 1H NMR
(300 MHz, CDCl3) d 8.02 (m, 6H), 7.60 (br m, 3H), 7.45 (br m,
6H), 3.75 (m, 6H), 3.37 (br m, 2H), 3.14 (br m, 4H), 2.62 (br, 4H),
2.46 (br m, 4H), 2.00 (s, 3H), 1.59 (br, 8H), 1.43 (br, 6H), 1.33 (br,
4H); 13C NMR (75 MHz, CDCl3) d 173.1, 171.9, 171.8, 170.4,
169.3, 165.6, 164.4, 134.5, 129.9 (ꢁ2), 128.9, 126.5, 126.4, 47.7,
41.3, 39.2, 30.2, 28.9, 28.4, 27.7, 26.6, 26.4, 23.7, 23.5, 20.3; MS
3.2. Experimental procedures
3.2.1. Dendrimer 1
A solution of 4-piperidinemethanol in THF (10 mL) was added
to a solution of 5 (0.20 g, 0.0135 mmol) and DIPEA (0.3 mL,
1.71 mmol) in THF (20 mL). The solution was stirred for 24 h at
room temperature and evaporated under vacuum. The residue
(MALDI-TOF) calcd for
C49H59Cl2N9O11 1019.3711, found
1020.2622 (M+H)+.
was dissolve in
a solution of triethylamine (1.2 mL), H2O
3.2.4. Intermediate 5
(2.4 mL), and methanol (8 mL). The solution was stirred for 24 h
at room temperature and evaporated under vacuum. The residue
was dissolved in deionized water and filtered. The resulting solu-
tion was subjected to diafiltration to remove low molecular weight
impurities using an Amicon stirred ultrafiltration cell with a PLCC
membrane (MWCO: 5 kDa) in deionized water over 3 days. The
purified solution was evaporated under vacuum to afford 1
A solution of 2 (0.11 g, 0.0372 mmol) in THF (3 mL) and H2O
(2 mL) was slowly added to a solution of 4 (0.55 g, 0.539 mmol)
and DIPEA (0.2 mL, 1.13 mmol) in THF (7 mL). The solution was
stirred for 48 h at room temperature and evaporated under vac-
uum. The residue was dissolved with dichloromethane, washed
with brine, dried over MgSO4, filtered, and evaporated under vac-
uum. The crude product was purified by silica gel chromatography
(from acetone/hexane = 3:2 to DCM/MeOH = 7:1) to give 5 (0.44 g,
80%) as a white solid. 1H NMR (500 MHz, CDCl3) d 8.05 (m, 72H),
7.63 (br, 36H), 7.48 (br m, 72H), 3.77–3.10 (br m, 276H), 2.64
(br, 48H), 2.47 (br, 48H), 2.02 (s, 36H), 1.59–1.35 (br m, 306H);
13C NMR (75 MHz, CDCl3) d 173.1, 171.9, 165.7, 165.4, 164.6,
134.6, 130.1 (ꢁ2), 129.0, 126.8, 126.6, 47.9, 44.3, 43.1, 40.8, 39.3,
30.5, 29.1, 28.6, 27.9, 26.8, 25.9, 25.1, 23.9, 23.7, 20.5; MS (MAL-
DI-TOF) calcd for C729H948Cl12N180O132 14754.93, found 14762.05
(M+H)+.
(0.12 g, 74% over two steps) as
a
colorless solid. 1H NMR
(500 MHz, DMSO-d6) d 4.60 (br, 24H), 3.80–3.05 (br m, 252H),
2.99 (br m, 48H), 2.65–2.57 (br m, 72H), 2.26 (m, 48H), 1.96 (s,
36H), 1.80–1.20 (br m, 366H); 13C NMR (75 MHz, CD3OD) d
174.8, 174.4, 174.3, 173.4, 167.3, 166.7, 165.9, 67.9, 48.7, 45.3,
44.3, 41.4, 40.3, 31.5, 30.6, 30.0, 28.9, 27.3, 25.1, 24.9, 20.4. MS
(MALDI-TOF) calcd for
C549H948N192O108 11959.46, found
11964.65 (M+H)+.
3.2.2. Intermediate 3
A solution of Boc anhydride (0.50 g, 2.29 mmol) in dioxane
(5 mL) was added to a suspension of deferoxamine mesylate
(1.20 g, 1.83 mmol) and triethylamine (0.6 mL, 4.30 mmol) in diox-
ane (7 mL) and H2O (7 mL). The solution was stirred for 16 h at
40 °C and evaporated in vacuum. The residue was suspended in
methanol (5 mL) and precipitated by adding diethyl ether
(70 mL). The precipitate was filtered, washed with diethyl ether,
and dried to give the N-Boc DFO derivative (1.0 g, 83%) that was
used without further purification. Benzoyl chloride (0.694 mL,
5.98 mmol) was slowly added to a solution of the protected inter-
mediate (0.66 g, 1.0 mmol) followed by pyridine (0.51 mL,
6.32 mmol) in DMF (8 mL) at 0 °C. The solution was warmed to
room temperature, stirred under nitrogen for 16 h, and evaporated
4. Conclusion
Here, we add to the number of macromolecular agents that are
able to chelate iron(III). Triazine dendrimer 1 is not only capable of
sequestration, but comprises a significant amount of active agent
by weight (56%). The material, while a multi-component mixture,
is still well-defined for a macromolecule. Limitations of the func-
tional monomer approach have emerged: protecting group migra-
tions suggest that orthogonal conjugation/protecting group
strategies will be needed if single-chemical entity materials are
desired. The dispersity observed, however, is likely to be much nar-
rower than previously described constructs wherein the polymer is

J. Lim et al. / Bioorg. Med. Chem. 18 (2010) 5749–5753
5753
Breuer, W.; Cabantchik, Z. I.; Link, G. Blood 2001, 97, 1115; (d) Barman-Balfour,
J. A.; Foster, R. H. Drugs 1999, 58, 553; (e) Franchini, M.; Veneri, D. Hematology
2005, 10, 145; (f) Neufeld, E. J. Blood 2006, 107, 3436; (g) Bickel, H.; Hall, G. E.;
Keller-Schierlein, W.; Prelog, V.; Vischer, E.; Wettstein, A. Helv. Chim. Acta 1960,
43, 2129.
inherently more disperse prior to derivatization. While the litera-
ture provides numerous examples of small molecule seques-
trants,19 both the synthetic accessibility and opportunities that
this and related macromolecular agents provide compelling moti-
vation for future efforts in this area.
8. (a) Hallaway, P. E.; Eaton, J. W.; Panter, S. S.; Hedlund, B. E. Proc. Natl. Acad. Sci.
U.S.A. 1989, 86, 10108; (b) Dragsten, P. R.; Hallaway, P. E.; Hanson, G. J.; Bergeb,
A. E.; Bernard, B.; Hedlund, B. E. J. Lab. Clin. Med. 2000, 135, 57.
9. Mahoney, J. R.; Hallaway, P. E.; Hedlund, B. E.; Eaton, J. W. J. Clin. Invest. 1989,
84, 1362.
Acknowledgments
10. (a) Rossi, N. A. A.; Mustafa, I.; Jackson, J. K.; Burt, H. M.; Horte, S. A.; Scott, M. D.;
Kizhakkedathu, J. N. Biomaterials 2009, 30, 638; (b) Cohen, S. M.; Petoud, S.;
Raymond, K. N. Chem. Eur. J. 2001, 7, 272.
The authors acknowledge support of the NIH (R01 NIGMS
65640) and the Robert A. Welch Foundation (A 1439).
11. Chouai, A.; Simanek, E. E. J. Org. Chem. 2007, 73, 2357.
12. (a) Zhang, W.; Jiang, J.; Qin, C.; Perez, L. M.; Parrish, A. R.; Safe, S. H.; Simanek, E.
E. Supramol. Chem. 2003, 15, 607; (b) Neerman, M. F.; Zhang, W.; Parrish, A. R.;
Simanek, E. E. Int. J. Pharm. 2004, 281, 129; (c) Chen, H.-T.; Neerman, M. F.;
Parrish, A. R.; Simanek, E. E. J. Am. Chem. Soc. 2004, 126, 10044; (d) Lo, S. -T.;
Stern, S.; Clogston, J. D.; Zheng, J.; Adiseshaiah, P. P.; Dobrovolskaia, M.; Lim, J.;
Patri, A.; Sun, X.; Simanek, E. E. Mol. Pharmacol. 2010, in press.
13. (a) Hollink, E.; Simanek, E. E. Org. Lett. 2006, 8, 2293; (b) Crampton, H.; Hollink,
E.; Perez, L. M.; Simanek, E. E. New J. Chem. 2007, 31, 1283.
Supplementary data
Supplementary data (assignments for 1H and 13C NMR spectra,
and the original NMR and mass spectra) associated with this article
can be found, in the online version, at doi:10.1016/j.bmc.2010.05.
039.
14. Lim, J.; Simanek, E. E. Org. Lett. 2008, 10, 201.
15. Venditto, V. J.; Allred, K.; Allred, C. D.; Simanek, E. E. Chem. Commun. 2009, 37,
5541.
References and notes
16. Ye, Y.; Bloch, S.; Xu, B.; Achilefu, S. Bioconjugate Chem. 2008, 19, 225.
17. (a) Neilands, J. B. Ann. Rev. Biochem. 1981, 50, 715; (b) Mishra, B.; Haack, E. A.;
Maurice, P. A.; Bunker, B. A. Environ. Sci. Technol. 2009, 43, 94.
18. (a) Steffensen, M. B.; Simanek, E. E. Org. Lett. 2003, 5, 2359; (b) Moreno, K. X.;
Simanek, E. E. Tetrahedron Lett. 2008, 49, 1152.
19. (a) Brittenham, G. M. Alcohol 2003, 30, 151; (b) Cappellini, M. D.; Pattoneri, P.
Annu. Rev. Med. 2009, 60, 25; (c) Liu, J.; Obando, D.; Schipanski, L. G.; Groebler,
L. K.; Witting, P. K.; Kalinowski, D. S.; Richardson, D. R.; Codd, R. J. Med. Chem.
2010, 53, 1370; (d) Donovan, J. M.; Plone, M.; Dagher, R.; Bree, M.; Marquis, J.
Ann. N.Y. Acad. Sci. 2005, 1054, 492; (e) Kwiatkowski, J. L. Hematol. Oncol. Clin.
North Am. 2010, 24, 229; (f) Schmid, M. Blood Rev. 2009, 23, S21; (g) Liu, G.;
Men, P.; Perry, G.; Smith, M. A. Methods Mol. Biol. 2010, 610, 123.
1. (a) Cazzola, M.; Della Porta, M. G.; Malcovati, L. Hematol. Am. Soc. Hematol. Educ.
Program 2008, 166; (b) Beutler, E. Blood Cells Mol. Dis. 2007, 39, 140.
2. Wessling-Resnick, M. Annu. Rev. Physiol. 2000, 20, 129.
3. (a) Zhang, A.-S.; Enns, C. A. J. Biol. Chem. 2009, 284, 711; (b) McCance, R. A.;
Widdowson, E. M. Nature 1943, 152, 326.
4. (a) Bring, P.; Partovi, N.; Ford, J.-A. E.; Yoshida, E. M. Pharmacotherapy 2008, 28,
331; (b) Siah, C. W.; Trinder, D.; Olynyk, J. K. Clin. Chim. Acta 2005, 358, 24.
5. (a) Kontoghiorghes, G. J. Drugs Future 2005, 30, 1241; (b) Halliwell, B.;
Gutteridge, J. M. C. Biochem. J. 1984, 219, 1; (c) Slater, T. F. Biochem. J. 1984, 222,
1.
6. (a) Nick, H. Curr. Opin. Chem. Biol. 2007, 11, 419; (b) Alvey, L. FDA News 2005.
7. (a) Kontoghiorghes, G. J. Hemoglobin 2006, 30, 329; (b) Liu, Z. D.; Hider, R.
Coord. Chem. Rev. 2002, 232, 151; (c) Hershko, C.; Konijn, A. M.; Nick, H. P.;