Desferrithiocin analogues and nephrotoxicity

Article abstract of DOI:10.1021/jm8003398

The syntheses of a series of 4′-O-alkylated (S)-4,5-dihydro-2-(2,4- dihydroxyphenyl)-4-methyl-4-thiazolecarboxylic acid and 5′-O-alkylated (S)-4,5-dihydro-2-(2,5-dihydroxyphenyl)-4-methyl-4-thiazolecarboxylic acid ligands are described. Their partition between octanol and water, log P _app, is determined, along with their iron-clearing efficiency (ICE) in both non-iron-overloaded, bile duct-cannulated rodents and in iron-overloaded primates. The ligand-promoted biliary ferrokinetics in rats are described for each of the chelators. Plots of log P_app versus ICE in a rodent model for both the 4′-O-alkylated 2,4-dihydroxy and 5′-O-alkylated 2,5-dihydroxy series produced an inverse parabola plot with r² values of 0.97 and 0.81, respectively. The plots indicate an optimum log P _app/ICE relationship. Because of the nature of the data spread in the 4′-O-alkylated 2,4-dihydroxy series, it will be used to help assess the origin of nephrotoxicity in desferrithiocin analogues: is toxicity simply related to lipophilicity, ICE, or a combination of these properties?

Full text of DOI:10.1021/jm8003398

J. Med. Chem. 2008, 51, 5993–6004
5993
Desferrithiocin Analogues and Nephrotoxicity
Raymond J. Bergeron,* Jan Wiegand, James S. McManis, Neelam Bharti, and Shailendra Singh
Department of Medicinal Chemistry, UniVersity of Florida, GainesVille, Florida 32610-0485
ReceiVed March 25, 2008
The syntheses of a series of 4′-O-alkylated (S)-4,5-dihydro-2-(2,4-dihydroxyphenyl)-4-methyl-4-thiazole-
carboxylic acid and 5′-O-alkylated (S)-4,5-dihydro-2-(2,5-dihydroxyphenyl)-4-methyl-4-thiazolecarboxylic
acid ligands are described. Their partition between octanol and water, log Papp, is determined, along with
their iron-clearing efficiency (ICE) in both non-iron-overloaded, bile duct-cannulated rodents and in iron-
overloaded primates. The ligand-promoted biliary ferrokinetics in rats are described for each of the chelators.
Plots of log Papp versus ICE in a rodent model for both the 4′-O-alkylated 2,4-dihydroxy and 5′-O-alkylated
2,5-dihydroxy series produced an inverse parabola plot with r2 values of 0.97 and 0.81, respectively. The
plots indicate an optimum log Papp/ICE relationship. Because of the nature of the data spread in the 4′-O-
alkylated 2,4-dihydroxy series, it will be used to help assess the origin of nephrotoxicity in desferrithiocin
analogues: is toxicity simply related to lipophilicity, ICE, or a combination of these properties?
Introduction
not found in hepatocytes or Kupffer cells.20 These differences
in modes of iron uptake also may underlie clinical observations
of differences in the course and pace of iron deposition and
damage to the liver, pancreas, and heart in patients with all forms
of iron overload.6
The toxicity associated with excess iron, whether a systemic
or a focal problem, derives from its interaction with reactive
oxygen species, for instance, endogenous hydrogen peroxide
(H2O2).21–24 In the presence of Fe(II), H2O2 is reduced to the
hydroxyl radical (HO•) and HO-, a process known as the Fenton
reaction. The hydroxyl radical reacts very quickly with a variety
of cellular constituents and can initiate free radicals and radical-
mediated chain processes that damage DNA and membranes,
as well as produce carcinogens.22,25,26 The Fe(III) liberated in
the peroxide reduction can be converted back to Fe(II) via a
variety of biological reductants, for example, ascorbate or
glutathione, exacerbating the situation.
In the majority of patients with thalassemia major or other
transfusion-dependent refractory anemias, treatment with a
chelating agent capable of sequestering iron and permitting its
excretion from the body is the only therapeutic approach
available. Some of the iron-chelating agents that are now in
use or that have been clinically evaluated include desferriox-
amine B mesylate (DFO), 1,2-dimethyl-3-hydroxypyridin-4-one
(deferiprone, L1),27–30 4-[3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-
1-yl]benzoic acid (deferasirox, ICL670A),31–34 and the desfer-
rithiocin (DFT) analogue, (S)-2-(2,4-dihydroxyphenyl)-4,5-
dihydro-4-methyl-4-thiazolecarboxylic acid [deferitrin35 (1),
Table 1]. Each of these agents chelates iron derived predomi-
nantly from systemic storage sites, that is, from iron released
by macrophages after catabolism of senescent red blood cells,
from iron in hepatic pools, or from both; each has significant
shortcomings.36
Desferrioxamine B (DFO), a hexacoordinate hydroxamate
iron chelator produced by Streptomyces pilosus,37 is not orally
active and is best administered subcutaneously (sc) by continu-
ous infusion over long periods of time,7,38 a patient compliance
issue.7,39 Deferiprone, while orally active, does not remove
enough iron to keep patients in a negative iron balance.27–30
The Novartis drug deferasirox did not show noninferiority to
DFO and is associated with numerous side effects;31–34 it has a
narrow therapeutic window. The clinical trial on the desfer-
Although iron comprises 5% of the earth’s crust, living
systems have great difficulty in accessing and managing this
vital micronutrient. It is essential to redox processes in all
prokaryotes and eukaryotes. The very poor solubility of Fe(III)
hydroxide, the predominant form of the metal in the biosphere
(Ksp ) 1 × 10-39),1 has led to the development of sophisticated
iron storage and transport systems in nature. Microorganisms
utilize low molecular weight, virtually ferric iron specific
ligands, siderophores.2 Higher life forms, animals, tend to
employ proteins to transport and store iron (e.g., transferrin and
ferritin, respectively).3–5
Humans have developed a highly efficient iron management
system in which we absorb and excrete only about 1 mg of the
metal daily; there is no mechanism for the excretion of excess
iron.6 Whether derived from transfused red blood cells7–9 or
from increased absorption of dietary iron,10,11 without effective
treatment, body iron progressively increases with deposition in
the liver, heart, pancreas, and elsewhere. Iron accumulation
eventually produces (i) liver disease that may progress to
cirrhosis,12–14 (ii) diabetes related both to iron-induced decreases
in pancreatic ꢀ-cell secretion and to increases in hepatic insulin
resistance,15,16 and (iii) heart disease, still the leading cause of
death in thalassemia major and related forms of transfusional
iron overload.6,17,18 Non-transferrin-bound plasma iron (NTBIa),
a heterogeneous pool of iron in the circulation that is not bound
to the physiological iron transporter transferrin, seems to be a
principal source of the abnormal tissue distribution of iron that
develops with chronic iron overload. NTBI is rapidly taken up
by hepatocytes in the liver, the major iron storage organ, perhaps
through the divalent metal transporter 119 and other pathways
that remain poorly characterized. NTBI also seems to gain entry
into cardiomyocytes, pancreatic ꢀ-cells, and anterior pituitary
cells specifically via L-type voltage-dependent Ca2+ channels
* To whom correspondence should be addressed. Phone: (352) 273-7725.
Fax: (352) 392-8406. E-mail: rayb@ufl.edu.
a Abbreviations: b.i.d., twice a day; DFO, desferrioxamine B mesylate;
DFT, desferrithiocin (S)-4,5-dihydro-2-(3-hydroxy-2-pyridinyl)-4-methyl-
4-thiazolecarboxylic acid; DTPA, diethylenetriaminepentaacetic acid; ICE,
iron-clearing efficiency; log Papp, octanol-water partition coefficient (li-
pophilicity); MIC, maximum iron clearance; NTBI, non-transferrin bound
iron; s.i.d., once a day.
10.1021/jm8003398 CCC: $40.75
2008 American Chemical Society
Published on Web 09/13/2008

5994 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19
Bergeron et al.
Table 1. Iron-Clearing Activity of Desferrithiocin Analogues Administered Orally to Rodents and Primates and the Partition Coefficients of the
Compounds
a In the rodents [n ) 3 (6, 10), 4 (3, 4, 7-9, 11, 12), 5 (2, 5), or 8 (1)]. The rats were given a single 300 µmol/kg dose of the ligands orally by gavage.
The compounds were given as their sodium salts, prepared by the addition of 1 equiv of NaOH to a suspension of the free acid in distilled water. The
efficiency of each compound was calculated by subtracting the iron excretion of control animals from the iron excretion of the treated animals. The number
was then divided by the theoretical output; the result is expressed as a percent. The relative percentage of the iron excreted in the bile and urine are in
brackets. Compound 2 was solubilized in distilled water. b In the primates [n ) 3 (12), 4 (2, 5, 7-9, 11), 6 (1), or 7 (3, 4)]. The doses were [37.5 µmol/kg
(5, 12), 75 µmol/kg (3, 7, 11), or 150 µmol/kg (1, 2, 4, 8, 9)]. Ligands 6 and 10 were not given to the primates because of toxicity observed in the rodents.
The compounds were prepared as for the rodents except that 4 was solubilized in 40% Cremophor RH-40. The efficiency of each compound was calculated
by averaging the iron output for 4 days before the drug, subtracting these numbers from the 2-day iron clearance after the administration of the drug, and
then dividing by the theoretical output; the result is expressed as a percent. The relative percentage of the iron excreted in the feces and urine are in brackets.
c Data are expressed as the log of the fraction in the octanol layer (log Papp); measurements were done in Tris buffer, pH 7.4, using a “shake flask” direct
method. The values obtained for compounds 1 and 4 are from ref 46; the value for 2 is from ref 42; the value for 3 is from ref 55; the values for 8 and 9
are from ref 47. d Data are from ref 42. e Data are from ref 44. f Data are from ref 55. g Data are from ref 46. h Data are from ref 47.

Desferrithiocin Analogues and Nephrotoxicity
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19 5995
rithiocin analogue 1 (Table 1) has now been abandoned by
Genzyme because of renal toxicity.35
compound was shown to be an excellent deferration agent when
given orally to rodents51 and Cebus apella primates,52,53 it
caused severe nephrotoxicity in rats.53 However, the compound’s
oral activity spurred a structure-activity relationship (SAR)
study focused on the desferrithiocin platform aimed at identify-
ing an analogue with similar iron clearing properties but without
the attendant nephrotoxicity.44,46,54
The most common toxicity seen in animals treated with iron
chelators is nephrotoxicity. This has been the case with
diethylenetriaminepentaacetic acid (DTPA),40 deferasirox,31–34
the catecholamides,41 and 1.35,42 The renal toxicity has by and
large been limited to the proximal tubules. The animal preclini-
cal toxicity data have been predictive of human outcomes.43
The origin of 1-induced renal toxicity remains elusive.
Although 1 was profoundly less toxic than desferrithiocin
itself,44 it seemed likely that nephrotoxicity would be the dose-
limiting factor.42 In fact, nephrotoxicity was shown to be the
dose-limiting issue with 1 clinically.35 However, there was an
interesting clinical caveat: the nephrotoxicity appeared to be
very much dependent on chelator dosing schedule. Although 1
was well tolerated in patients at doses of 5, 10, or 15 mg/kg/d
once daily (s.i.d.) for up to 12 weeks, unacceptable renal toxicity
was observed in three patients after only 4-5 weeks of treatment
when the drug was given twice daily (b.i.d) at a dose of 12.5
mg/kg (25 mg/kg/d).35
In the course of these SAR studies, we discovered that the
lipophilicity of a ligand, as determined by its partition between
octanol and water, log Papp, could have a profound effect on
the ligand’s iron-clearing efficiency (ICE), organ distribution,
and toxicity profile.47 The more lipophilic a chelator, the better
the ICE; often, the more lipophilic the chelator, the more toxic
it was.42 This is best exemplified by (S)-4,5-dihydro-2-(2-
hydroxy-4-methoxyphenyl)-4-methyl-4-thiazolecarboxylic acid
(4, Table 1).42,46 This ligand is lipophilic, log Papp) -0.70, and
a very effective iron chelator when given orally to rodents or
primates; the ICE values in rodents and primates were 6.6 (
2.8%42 and 24.4 ( 10.8%,46 respectively. Unfortunately, the
ligand was also very toxic. All of the rats given the drug po at
a dose of 384 µmol/kg/d (equivalent to 100 mg/kg of the DFT
sodium salt) were dead by day 6 of a planned 10-d study.42
The rats presented with nephrotoxicity, which was acute, diffuse,
severe, and characterized by proximal tubular epithelial necrosis
and sloughing. Chelator 4 was indeed a worst-case scenario:
lipophilic, high ICE values, and very toxic, a perfect candidate
for assessing toxicity mechanisms.
We confirmed this finding in a recent study45 in rodents in
which the rats were given 1 orally by gavage s.i.d. at a dose of
474 µmol/kg/d for 7 days. This dose is equivalent to 120 mg/
kg/d of the parent 1. An additional group of animals was given
the drug b.i.d. at 237 µmol/kg/dose (474 µmol/kg/d) for 7
days.42,45 Untreated rats served as age-matched controls. One
day postdrug, the rodents were anesthetized and the kidneys
were perfusion-fixed; one kidney from each rat was dissected.
The differences in proximal tubule damage were profound. The
kidneys of animals treated s.i.d. had mild proximal tubule
vacuolization, while the kidneys of animals treated b.i.d.
presented significant architectural changes. Vacuolization was
now severe.42,45
Under an identical dosing regimen, rodents were given the
desferrithiocin polyether analogues (S)-4,5-dihydro-2-[2-hydro-
xy-4-(3,6,9-trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxy-
lic acid42 (2, Table 1) and (S)-4,5-dihydro-2-[2-hydroxy-3-(3,6,9-
trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxylic acid45 (3,
Table 1) orally by gavage at a dose of 237 µmol/kg b.i.d. (474
µmol/kg/d) for 7 days. There was little if any damage to the
proximal tubules, only occasional pale, refractile inclusions in
the S1 segments, which were more prevalent in the rats treated
with 2, a surprising finding. While these polyether analogues
are undergoing further preclinical development, we are never-
theless compelled to look at additional desferrithiocin analogue
platforms in the hopes of better understanding structure-activity
issues that regulate nephrotoxicity.
Previous studies were consistent with the idea that within a
family of ligands, the more lipophilic analogues are generally
more efficient iron chelators.42,46,47 However, the more lipophilic
ligands are also more toxic. The reason for this was not clear.
Was the increase in toxicity due to lipophilicity or ICE? In order
to develop a better understanding of the relationship between
ICE, lipophilicity, and chelator-induced renal toxicity, a basis
set of ligands with variable log Papps was synthesized (Table
1). Their iron clearing properties were evaluated in rodents and
primates. With this information in hand, these ligands can now
be evaluated for proximal tubule damage as a function of both
ICE and log Papp; this will be the subject of a future manuscript.
Ultimately, it was demonstrated that substituting the 4′-
methoxy group of 4 with a 3,6,9-trioxadecyloxy group, provid-
ing 2, reduced the lipophilicity from -0.70 log Papp for 4 to
-1.10 and virtually eliminated nephrotoxicity in a rodent
model.42 The ICE of the 4′-polyether 2 (5.5 ( 1.9%) was within
error of the ICE for the 4′-methoxy ligand 4 (6.6 ( 2.8%) upon
po administration to rats at a dose of 300 µmol/kg (p > 0.05).42
The ICEs of the two chelators in the iron-loaded primates were
also similar, 25.4 ( 7.4%42 for 2 versus 24.4 ( 10.8%46 for 4
(p > 0.05). This encouraged the synthesis of an additional
ligand, the 3′-(3,6,9)-trioxadecyloxy analogue 3.55 This chelator
had a higher ICE in rodents than 2, 10.6 ( 4.4%, at a dose of
300 µmol/kg po, and did not present any nephrotoxicity.55 These
findings elicited a series of extensive comparative dose-response
iron clearance studies and toxicity trials between the polyether
analogues and 1.45
The most important observations to come out of the toxicity
studies were the profound difference in nephrotoxicity between
the polyether analogues and deferitrin and how dependent
1-induced renal damage was on dosing schedule. 1 given to
rodents po s.i.d. at a dose of 474 µmol/kg/d for 7 days caused
vacuolization of the renal proximal tubules.42,45 However, 1
given b.i.d. po to rodents at 237 µmol/kg/dose (474 µmol/kg/
d) for 7 days caused extensive and profound architectural
changes (vacuolization) of the proximal tubules.45 This was not
the case with either of the polyether analogues in identical b.i.d.
dosing experiments.45 There were little, if any, changes in the
cellular architecture of the proximal tubules of rats treated with
3 and only some minor inclusions in the proximal tubules of
rodents treated with 2.42,45
These findings encouraged additional toxicity and dose-re-
sponse studies45 of the 3′- and 4′-polyethers in order to identify
which ligand would be best to take forward to GLP preclinical
trials. Although these results further underscore the importance
of lipophilicity on how a chelator performs in animals, what
remains unclear is the extent to which lipophilicity can impact
on ligand ICE and toxicity. In order to settle this issue, we have
Design Concept
Desferrithiocin is a natural product tridentate iron chelator
isolated from Streptomyces antibioticus.48 It forms a tight 2:1
complex with Fe(III), ꢀ2 ) 4 × 1029 M-1 49,50
.
Although the

5996 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19
Bergeron et al.
Scheme 1. Synthesis of (S)-4′-Alkoxy Desazadesferrithiocin
Analogues 5-7a
Scheme 2. Synthesis of (S)-5′-Butoxy Desazadesferrithiocin 10a
a Reagents: (a) CH3CH2I (1.8 equiv), DIEA (1.8 equiv), DMF, 88%;
(b) CH3(CH2)3I (1.9 equiv), K2CO3 (2.1 equiv), acetone, 79%; (c) NaOH
(aq) (16 equiv), MeOH, 92%.
a Reagents: (a) CH3CH2I (1.8 equiv), K2CO3 (2.1 equiv), acetone, 65
°C, 84%; (b) CH3(CH2)3I (1.7 equiv), K2CO3 (1.6 equiv), acetone, 94%;
(c) CH3(CH2)7I (0.95 equiv), NaOEt (0.95 equiv), EtOH, 64%; (d) NaOH
(aq) (12-14 equiv), MeOH, 90% (5), 92% (6), 80% (7).
tyloxy)phenol (22) in 96% yield. Regiospecific formylation of
22 employing hexamethylenetetramine (1.0 equiv) in trifluo-
roacetic acid (TFA) produced substituted salicylaldehyde 23 in
39% yield. Aldehyde 23 was derivatized as oxime 24 (96%
yield), which was converted to nitrile 25 under standard
conditions (Ac2O at reflux and then NaOH) in 72% yield.
Cyclocondensation of 25 with (S)-R-methylcysteine hydrochlo-
ride (26, 1.4 equiv) at pH 6 followed by an esterification reaction
(CH3CH2I, DIEA, DMF) gave ethyl (S)-2-[4,5-bis(octyloxy)-
2-hydroxyphenyl]-4,5-dihydro-4-thiazolecarboxylate (27) in 90%
yield. Alkaline hydrolysis of ester 27 and acidification completed
the synthesis of lipophilic chelator 12 in 92% yield. The overall
yield to 12 was 21%.
elected to first assemble a group of alkoxydesazadesferrithiocin
analogues with large differences in log Papp and measure their
ICE values in rodents and primates (Table 1). This will then be
followed by extensive ligand organ distribution and toxicity/
histopathology studies. The focus of the current study is to
develop a basis set of ligands to help define more precisely the
relationship between log Papp, ICE, and toxicity. This will help
to establish whether chelator-induced renal toxicity is derived
from lipophilicity, ICE, or some combination thereof.
Synthetic Methods
DFT analogues 1-4, 8, and 9 were synthesized using methods
published by this laboratory.44–47 The key step in the synthesis
of (S)-4,5-dihydro-2-(4-ethoxy-2-hydroxyphenyl)-4-methyl-4-
thiazolecarboxylic acid (5), (S)-2-(4-butoxy-2-hydroxyphenyl)-
4,5-dihydro-4-thiazolecarboxylic acid (6), and (S)-4,5-dihydro-
2-[2-hydroxy-4-(octyloxy)phenyl]-4-methyl-4-
thiazolecarboxylic acid (7, Table 1) was alkylation of the ethyl
ester 1356 at the less hindered hydroxy group (Scheme 1).
Specifically, resorcinol system 13 was heated with K2CO3 (2.1
equiv) and iodoethane (1.8 equiv) in acetone, giving ethyl ester
14 in 84% yield. Similarly, refluxing 13 with K2CO3 and
1-iodobutane in acetone provided masked DFT analogue 15 in
94% yield. When ethyl ester 13 was heated with sodium
ethoxide and 1-iodooctane (0.95 equiv each) in EtOH, monoalky-
lated product 16 was obtained in 64% yield. Hydrolysis of the
ethyl ester group in 14-16 using excess 50% NaOH (aqueous)
in CH3OH at room temperature and then acidification generated
lipophilic DFT analogues 5-7 as solids in yields of at least
80%.
Partition Properties
The partition values between octanol and water (at pH 7.4,
Tris buffer) were determined using a “shake flask” direct method
of measuring log Papp values.58 The fraction of drug in the
octanol is then expressed as log Papp. These values varied widely
among the basis set (Table 1) from log Papp ) -1.22 for 3′-
polyether 3 to log Papp ) 2.05 for 12. This represents a greater
than1800-fold difference in partition. As described above, there
are three structural groups: the 4′-substituted compounds 1, 2,
4-7, the 5′-substituted compounds 8-11, and the 4′,5′-
disubstituted ligand 12. Of the 4′-substituted compounds, the
most lipophilic chelator is 7, 380 times more lipophilic than
the parent 1. Of the 5′-substituted ligands, 11 is the most
lipophilic, 500 times more lipophilic than the parent ligand 8.
However, the most lipophilic of all the ligands, not unexpect-
edly, is the dioctoxy compound 12, over 1200 or 1500 times
more lipophilic than the 4′- or 5′-hydroxy parent 1 or 8,
respectively.
After conversion of 847 to its ethyl ester 17 in 88% yield
[CH3CH2I, N,N-diisopropylethylamine (DIEA), DMF], selective
O-butylation of the hydroquinone system using 1-iodobutane
and K2CO3 in acetone at reflux gave protected DFT analogue
18 in 79% yield. Ester hydrolysis generated (S)-2-(5-butoxy-
2-hydroxyphenyl)-4,5-dihydro-4-thiazolecarboxylic acid (10) in
92% yield (Scheme 2). The same strategy was employed to
make (S)-4,5-dihydro-2-[2-hydroxy-5-(octyloxy)phenyl)-4-meth-
yl-4-thiazolecarboxylic acid (11, Scheme 3). The isopropyl ester
1955 was alkylated at the less hindered hydroxyl using 1-io-
dooctane and sodium isopropoxide in refluxing 2-propanol,
affording masked chelator 20 in 35% yield. Base-promoted
removal of the ester protecting group furnished chelator 11 in
96% yield.
Chelator-Induced Iron Clearance in
Non-Iron-Overloaded Rodents
Bile duct-cannulated rodents were given a single 300 µmol/
kg dose of the respective chelators orally by gavage. The data
in Table 1 include the iron-clearing efficiency (ICE) and the
fraction of iron excreted in the bile and urine for each ligand.
The parent drug 1 performed poorly in rodents with an ICE of
1.1 ( 0.8%;42 all of the metal was cleared in the bile. Virtually
any alkylation of the 4′-hydroxy of 1 led to a more efficient
iron chelator. Simple methylation of the 4′-hydroxy to produce
4 increased the ICE to 6.6 ( 2.8%,42 while ethylation providing
5 raised the ICE to 18.0 ( 0.9%. When the alkyl group gets
much longer, for example, butoxy compound 6, the ICE
decreases relative to ethyl analogue 5, 13.1 ( 3.3%. This is
also the case moving to the 4′-octyloxy analogue 7; the ICE
further decreases to 6.4 ( 2.3% (Table 1). Thus, within the
series of 4′-hydroxy substituted compounds, the optimum chain
length seems to be a two-carbon fragment. A plot of the rodent
The synthesis of (S)-2-[4,5-bis(octyloxy)-2-hydroxyphenyl]-
4,5-dihydro-4-thiazolecarboxylic acid (12) followed the meth-
odology of Scheme 4. Oxidative cleavage of the formyl group
of 3,4-bis(octyloxy)benzaldehyde (21)57 using 35% H2O2 and
concentrated sulfuric acid in CH3OH/CHCl3 gave 3,4-bis(oc-

Desferrithiocin Analogues and Nephrotoxicity
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19 5997
Scheme 3. Synthesis of (S)-5′-Octoxy Desazadesferrithiocin 11a
a Reagents: (a) CH3(CH2)7I (1.0 equiv), Na (1.0 equiv), i-PrOH, 35%; (b) NaOH (aq) (13 equiv), MeOH, 96%.
Scheme 4. Synthesis of (S)-4′,5′-Dioctoxy Desazadesferrithiocin 12a
a Reagents: (a) 35% H2O2, concentrated H2SO4, CHCl3, MeOH, 96%; (b) (CH2)6N4 (1.0 equiv), TFA, 39%; (c) H2NOH·HCl, NaOAc, MeOH, 96%; (d)
Ac2O, reflux then NaOH (aq), MeOH, 72%; (e) NaHCO3, CH3OH, phosphate buffer (pH 6.0), reflux; (f) CH3CH2I, DIEA, DMF, 90%; (g) NaOH (aq) (11
equiv), MeOH and then HCl, 92%.
ICE versus the log Papp for the 4′-hydroxy analogues generated
a well-defined curve (r2 ) 0.97), clearly indicating the optimum
log Papp value for ICE (Figure 1). Chelators with log Papps above
or below this value can have profoundly different iron-clearance
properties. Figure 1 defines an excellent relationship between
lipophilicity and ICE and will provide a strong foundation for
investigating the source of nephrotoxicity in desferrithiocin-
based ligands.
Alkylation of the 5′-hydroxy analogues resulted in ligands
with ICE trends similar to what was seen when the 4′-hydroxy
analogues were alkylated (Table 1). The parent drug 8 was the
least effective, with an ICE of 1.0 ( 0.9%.47 Fixing a methyl
group to 8, providing derivative 9, increased the ICE to 6.3 (
1.2%.47 Butylation of the 5′-hydroxy of 8 to produce 10 was
very effective at increasing the ICE (21.0 ( 4.0%) relative to
the parent drug 8. The 5′-octoxy analogue 11 was profoundly
more lipophilic than the parent but was not as effective a
deferration agent (4.0 ( 1.2% ICE) as methoxy derivative 9 or
Figure 1. Iron-clearing efficiency versus log Papp for (S)-4′-hydroxy
butoxy compound 10 (Table 1). A plot of the rodent ICE versus
desazadesferrithiocin analogues 1, 4-7 in bile duct-cannulated rats.
log Papp for the 5′-hydroxy series also suggests an optimum
The compounds were administered po.
lipophilicity, but the curve fit (r2 ) 0.81, Figure 2) was not
nearly as good as for the corresponding 4′-hydroxy series.
Finally, the dioctoxy ligand 12 was generated. This compound
was over 1200 times more lipophilic than either the 4′- or the
5′-hydroxy parents. However, there was no improvement in ICE
relative to the parent drugs. In fact, iron excretion was virtually
baseline. It is important to note that both the 4′- and 5′-butoxy

5998 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19
Bergeron et al.
Figure 2. Iron-clearing efficiency versus log Papp for (S)-5′-hydroxy
desazadesferrithiocin analogues 8-11 in bile duct-cannulated rats. The
compounds were administered po.
Figure 3. Biliary ferrokinetics of (S)-4′-hydroxy analogues 1, 4-7 in
bile duct-cannulated rats. The compounds were administered po.
analogues, 6 and 10, were found to be toxic in the bile duct-
cannulated rodents; in each instance, two of five rats given a
single 300 µmol/kg po dose of the chelators either died or were
sacrificed in moribund condition during the course of the 24 h
sample collection period. Thus, these ligands were not given to
the primates.
Iron Clearance in Iron-Loaded Primates
Iron-loaded primates were given the ligands orally by gavage.
Prior to exposure to any compound, a complete hematologic
and metabolic screen was run on each animal as previously
described.59 The same screen is also run after the iron clearing
study is complete in order to identify any untoward effects of
the chelator. The parent drug of the 4′-hydroxy series (1) was
given po at a dose of 150 µmol/kg and had an ICE of 16.8 (
7.2%42 (Table 1). The corresponding 4′-methoxy ligand 4, also
given po at 150 µmol/kg, had an ICE of 24.4 ( 10.8%.46 The
4′-ethoxy analogue 5 was given to the monkeys po at a dose of
37.5 µmol/kg and had an ICE of 25.1 ( 6.7%. This ligand was
given to the primates at a lower dose because of concerns about
potential toxicity associated with its lipophilicity. However, the
hematologic and metabolic screens taken after exposure to the
chelator were normal. As described above, the butoxy analogue
6 was not given to the primates because it was toxic in the bile
duct-cannulated rodents. Finally, the octoxy ligand 7 was
administered to the monkeys po at a dose of 75 µmol/kg. The
ICE was 17.8 ( 2.1%, and all hematologic and metabolic
screens were normal.
Figure 4. Biliary ferrokinetics of (S)-5′-hydroxy analogues 8-11 and
4′,5′-dioctoxy analogue 12 in bile duct-cannulated rats. The compounds
were administered po.
non-iron-loaded rodents (Table 1). While it is tempting to
attribute these differences solely to the fact that the primates
are iron-overloaded and the rodents are not, this is not likely
the case. In an earlier paper,55 we pointed out that the
performance ratios of the ligands (ICErodent/ICEprimate) can be
very different, even within a structurally similar family, and
thus are not consistent with the idea that iron overload is the
only explanation.
Biliary Ferrokinetics of Desferrithiocin Analogues
The relative ICE values of the 4′- and 5′-hydroxydesazades-
ferrithiocin analogues in the primates were similar to the rodent
results; the 4′-hydroxy series was consistently more efficient
(Table 1). The 5′-hydroxy parent 8 at 150 µmol/kg provided an
ICE of 12.6 ( 3.0%.47 Methylation of the 5′-hydroxy to give 9
increased the parent ICE; at 150 µmol/kg the ICE rose to 18.9
( 2.3%.47 Again, butoxy analogue 10 was not given to the
primates because of toxicity issues in the rodents. Octoxy
analogue 11 was given to the monkeys po at 75 µmol/kg. The
ICE was similar to the parent drug 8, ICE 12.6 ( 3.0% versus
12.3 ( 6.9% (p > 0.05) for the octoxy analogue 11. Again,
there were no untoward hematologic or metabolic screen
numbers for the octoxy analogue. Finally, the dioctoxy analogue
12 was given po to the primates at a dose of 37.5 µmol/kg. It
was only minimally effective, ICE 2.9 ( 2.5% (Table 1).
There is a consistent difference in ICE values seen for
primates versus rodents. In every instance the ligands’ ICE
values were higher in the iron-overloaded primates than in the
Non-iron-overloaded, bile duct-cannulated rats were given a
single 300 µmol/kg dose of ligands 1 and 4-12 orally by
gavage. Bile samples were collected at 3 h intervals for 24 h.
Iron content was evaluated by atomic absorption spectroscopy.
The biliary ferrokinetics were followed for all of the ligands in
the 4′- and 5′-hydroxydesazadesferrithiocin series (Figures 3 and
4). The areas under the curves reflect the relatiVe iron-clearing
efficiencies of the ligands.
The parent drug 1, achieves maximum iron clearance (MIC)
at 3 h, faster than any of the analogues in this series (Figure 3).
However, the iron clearance is also over sooner than with the
other ligands, complete by 9 h postdrug. The 4′-octoxy analogue
7 is next in terms of ICE, with an MIC at 9 h. It has a protracted
iron clearance time and is still not back to baseline levels at
24 h. The 4′-methoxy ligand 4 is a more efficient chelator than
the octoxy chelator 7 and has an MIC between 3 and 6 h; iron
excretion is essentially back to baseline at 15 h. The 4′-butoxy

Desferrithiocin Analogues and Nephrotoxicity
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19 5999
chelator 6 presents an MIC between 6 and 9 h, but significant
quantities of iron are still being excreted 24 h postdrug. It is
the second most efficient of the 4′-hydroxy analogues (Table
1). Finally, the 4′-ethoxy compound 5 is the most efficient of
the 4′-substituted ligands with a clear MIC at 6 h, and like the
ligands other than the parent 1 and 4, iron clearance is not back
to baseline levels at 24 h (Figure 3). The reasons for the
geometry of these curves will later be correlated with pharma-
cokinetic and chelator organ distribution data.
With the 5′-hydroxy parent 8, MIC is achieved at 3 h (Figure
4); like the 4′-hydroxy analogue 1, iron clearance is completed
at 9 h. The (S)-5′-octoxy analogue 11, like its 4′-octoxy
counterpart 7, is slow to reach MIC, not doing so until 12 h
postdrug and returning to baseline at 24 h. The 5′-methoxy
analogue 9 presents a sharply defined MIC at 3 h; iron clearance
is complete at 15 h. The 5′-butoxy analogue 10, the most
efficient iron chelator in both families, had an MIC at 9 h, and
iron clearance is still not back to baseline at 24 h. Finally, the
4′,5′-dioctoxy compound 12 did not induce any iron excretion
beyond baseline levels (Figure 4).
log Papp varied from -1.14 for the parent 8 to 1.56 for octoxy
compound 11, an array similar in magnitude to the 4′-hydroxy
series. The rodent ICE varied from 1.0 ( 0.9%47 for 8 to 21.0
( 4.0% for 5′-butoxy 10, a range similar to the 4′-hydroxy series
(Figure 2).
The biliary ferrokinetics of the 4′-hydroxy analogues pre-
sented a number of notable features (Figure 3). The parent 1
iron clearance was over by 9 h, with an MIC at 3 h. Methoxy
compound 4-induced iron clearance was also complete relatively
early, 15 h, with an MIC at 6 h. All of the other 4′-hydroxy
analogues (5-7) presented protracted iron clearance times;
deferration was ongoing even at 24 h postdrug.
The biliary ferrokinetics of 5′-hydroxy analogue 8 are similar
to 4′-hydroxy analogue 1, complete by 9 h with an MIC at 3 h.
The similarities between the two families end here. The MIC
of 5′-methoxylated analogue 9 occurs at 3 h, much earlier than
that of the corresponding 4′-methoxylated derivative 4; however,
the ICEs of the two ligands are within error of each other (p >
0.05). The 5′-butoxy ligand 10 induces the excretion of
significantly more iron than its 4′-counterpart 6, although its
MIC also occurs at 9 h. The 5′-octoxy analogue 11 has an MIC
slightly later than its 4′-counterpart 7, 12 h versus 9 h; overall
iron excretion is also lower. Finally, the ferrokinetics “curve”
of the 4′,5′-dioctoxy analogue 12 is almost a flat line, which is
in agreement with its poor ICE, <0.5%.
As in previous studies, the ligands in general performed very
well in the iron-overloaded primate model. The relationship
between log Papp and ICE is not nearly as obvious with the
monkeys as it is with the rodents. Again, while it is tempting
to ascribe the difference in ICE between the rodents and the
primates to iron overload, this may not be the whole story. The
performance ratios of the ligands (ICErodent/ICEprimate) can be
very different,55 even within a structurally similar family, and
thus are not consistent with the idea that iron overload is the
only explanation.
While there are two families of chelators to choose from in
explaining the relationship between ligand ICE, ferrokinetics,
organ distribution, lipophilicity, and nephrotoxicity, the 4′-
hydroxy analogues 1 and 4-7 (Table 1) are more attractive.
The curve of the 4′-hydroxy ligands relating rodent ICE and
log Papp is smoother, r2 ) 0.97 (Figure 1), than for the
corresponding 5′-hydroxy analogues 8-11, r2 ) 0.81 (Figure
2). The discrepancy is largely due to the ICE of the 5′-butoxy
ligand 10; its ICE is much greater than would have been
predicted based on its log Papp and is out of sync with the curve.
We thus have defined a set of desferrithiocin analogues from
which to launch a study focused on the origin of ligand-induced
renal toxicity. It will now be possible to evaluate the relationship
between ICE and log Papp on architectural changes in the
proximal tubules. This will be the subject of a future manuscript.
Conclusion
Although previous structure-activity studies led to the
identification of a number of desferrithiocin analogues that were
profoundly less nephrotoxic than desferrithiocin itself,42,44,47 for
example, 1, nephrotoxicity was still a concern. Indeed, the dose-
limiting property of 1 in both animal models and in patients
would prove to be nephrotoxicity.35 Furthermore, studies in both
rodents and in human clinical trials identified a significant
relationship between nephrotoxicity, not only at a total dose
level, but more importantly as a function of dose scheduling.
For example, the kidneys of rodents given 1 po s.i.d. at a dose
of 474 µmol/kg/d for 7 days presented moderate damage to the
proximal tubules.45 However, when the rats were given the drug
po b.i.d. at 237 µmol/kg/dose (474 µmol/kg/d) for 7 days, the
architectural changes to the proximal tubules were profoundly
more severe.42 The same phenomenon occurred clinically;
although the s.i.d. regimen (5, 10 or 15 mg/kg/d) was well
tolerated, b.i.d. dosing (12.5 mg/kg/dose, 25 mg/kg/d) led to
unacceptable nephrotoxicity, and the clinical study was termi-
nated.35
Further SAR studies of 1 itself led to the discovery that the
more lipophilic a ligand is, the better the ICE, but the more
toxic.42 This finding was translated into the syntheses of the
4′- and 3′- polyether analogues,42,55 2 and 3, respectively, which
were less lipophilic, less toxic, and had significantly greater ICE
than the parent 1 in rodent models.45 Histopathology studies
revealed little, if any, damage to the kidneys of rodents treated
with either of the polyether ligands.42,45 Both short-term (10 d)
and protracted toxicity (up to 30 d) trials underscore this idea.
The conundrum then became “How does one reconcile the
reduced lipophilicity and increased ICE of these ligands in view
of previous findings?” In order to settle this issue and to gain
a better understanding of the ligand structural parameters that
impact a chelator’s toxicity profile, a basis set of desferrithiocin
analogues was constructed (Table 1).
Experimental Section
C. apella monkeys were obtained from World Wide Primates
(Miami, FL). Male Sprague-Dawley rats were procured from
Harlan Sprague-Dawley (Indianapolis, IN). Cremophor RH-40 was
acquired from BASF (Parsippany, NJ). Ultrapure salts were
purchased from Johnson Matthey Electronics (Royston, U.K.). All
hematological and biochemical studies53 were performed by Antech
Diagnostics (Tampa, FL). Atomic absorption (AA) measurements
were made on a Perkin-Elmer model 5100 PC (Norwalk, CT).
Histopathological analysis was carried out by Florida Vet Path
(Bushnell, FL).
Two basis sets were assembled, one predicated on 4′-hydroxy
analogue 1 and a second based on the corresponding 5′-hydroxy
compound 8. One additional derivative was generated, the 4′,5′
dioctoxy analogue 12, a very lipophilic chelator. In the
4′-hydroxy series, the log Papp varied from -1.05 for the parent
1 to 1.53 for the octoxy derivative 7. In rodents the ICE was as
low as 1.1 ( 0.8%42 for 1 and as high as 18.0 ( 0.9% for
4′-ethoxy analogue 5 (Figure 1). In the 5′-hydroxy series, the
Cannulation of Bile Duct in Non-Iron-Overloaded Rats. The
cannulation has been described previously.52,53 Bile samples were
collected from male Sprague-Dawley rats (400-450 g) at 3 h

6000 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19
Bergeron et al.
intervals for 24 h. The urine sample was taken at 24 h. Sample
collection and handling are as previously described.52,53
4.07 (q, 2 H, J ) 6.8), 6.49 (d, 1 H, J ) 2.4), 6.52 (dd, 1 H, J )
8.4, 2.4), 7.32 (d, 1 H, J ) 8.4), 12.74 (s, 1 H), 13.18 (br s, 1 H);
13C NMR (DMSO-d6) δ 14.48, 24.13, 63.56, 82.45, 101.12, 107.24,
108.98, 131.62, 160.51, 162.83, 170.08, 173.77; HRMS m/z calcd
for C13H16NO4S, 282.0800 (M + H); found, 282.0763. Anal.
(C13H15NO4S) C, H, N.
Iron Loading of C. apella Monkeys. The monkeys (3.5-4 kg)
were iron overloaded with intravenous iron dextran as specified in
an earlier publication to provide about 500 mg of iron per kg of
body weight;59 the serum transferrin iron saturation rose to between
70% and 80%. At least 20 half-lives, 60 d,60 elapsed before any of
the animals were used in experiments evaluating iron-chelating
agents.
Primate Fecal and Urine Samples. Fecal and urine samples
were collected at 24 h intervals and processed as described
previously.52,53,61 Briefly, the collections began 4 d prior to the
administration of the test drug and continued for an additional 5 d
after the drug was given. Iron concentrations were determined by
flame atomic absorption spectroscopy as presented in other
publications.52,62
(S)-2-(4-Butoxy-2-hydroxyphenyl)-4,5-dihydro-4-methyl-4-
thiazolecarboxylic Acid (6). A solution of 50% (w/w) NaOH
(19.11 g, 239 mmol) in CH3OH (150 mL) was added over 17 min
to 15 (5.472 g, 16.22 mmol) in CH3OH (150 mL) with ice bath
cooling. The reaction mixture was stirred at room temperature for
1 d, and the bulk of the solvent was removed by rotary evaporation.
The residue was treated with dilute NaCl (200 mL), cooled in ice,
acidified with cold 2 N HCl (150 mL), and extracted with EtOAc
(200 mL, 2 × 100 mL). The EtOAc extracts were washed with
H2O (150 mL) and saturated NaCl (80 mL) and were concentrated
in vacuo. Recrystallization from EtOAc/hexanes generated 4.62 g
of 6 (92%) as a yellow solid, mp 138-140 °C: [R]24 +57.8° (c
Drug Preparation and Administration. In the iron-clearing
experiments, the rats were given a single 300 µmol/kg dose of drugs
1-12 orally (po). The compounds were administered as the
monosodium salt of the compound of interest (prepared by the
addition of 1 equiv of NaOH to a suspension of the free acid in
distilled water). Compound 2 was solubilized in distilled water.
The drugs were given to the monkeys po at a dose of 37.5 µmol/
kg (5, 12), 75 µmol/kg (3, 7, 11), or 150 µmol/kg (1, 2, 4, 8, 9).
The drugs were prepared as for the rats except that 4 was solubilized
in 40% Cremophor RH-40/distilled water. Note that 6 and 10 were
not given to the monkeys because of toxicity seen with the drugs
in the bile duct-cannulated rats.
Calculation of Iron Chelator Efficiency. The theoretical iron
outputs of the chelators were generated on the basis of a 2:1
complex. The efficiencies in the rats and monkeys were calculated
as set forth elsewhere.44 Data are presented as the mean ( the
standard error of the mean; p values were generated via a one-
tailed student’s t-test in which the inequality of variances was
assumed, and a p value of <0.05 was considered significant.
Synthetic Methods. DFT analogues 1-4, 8, and 9 were
synthesized using methods published by this laboratory.44–47
Reagents were purchased from Aldrich Chemical Co. (Milwaukee,
WI). Fisher Optima grade solvents were routinely used, and DMF
was distilled. Reactions were run under a nitrogen atmosphere, and
organic extracts were dried with sodium sulfate. Silica gel 40-63
from SiliCycle, Inc. (Quebec City, Quebec, Canada) was used for
column chromatography, and Sephadex LH-20 was obtained from
Amersham Biosciences (Piscataway, NJ). Melting points are
uncorrected. Glassware that was presoaked in 3 N HCl for 15 min,
washed with distilled water and distilled EtOH, and oven-dried was
used during the isolation of 5-7 and 10-12. Optical rotations were
run at 589 nm (sodium D line) utilizing a Perkin-Elmer 341
polarimeter, with c being concentration in grams of compound per
100 mL. Chemical shifts (δ) for 1H NMR spectra at 400 MHz are
given in parts per million downfield from tetramethylsilane (CDCl3
not indicated). Chemical shifts (δ) for 13C NMR spectra at 100
MHz are given in parts per million referenced to the residual solvent
resonance: CDCl3 (δ 77.16), CD3OD (δ 49.00), or DMSO-d6 (δ
39.52). Coupling constants (J) are in hertz. Elemental analyses were
performed by Atlantic Microlabs (Norcross, GA).
1
0.95, DMF); 500 MHz H NMR (DMSO-d6) δ 0.93 (t, 3 H, J )
7.4), 1.42 (sextet, 2 H, J ) 7.5), 1.58 (s, 3 H), 1.65-1.72 (m, 2
H), 3.36 (d, 1 H, J ) 11.5), 3.79 (d, 1 H, J ) 11.5), 4.01 (t, 2 H,
J ) 6.5), 6.50 (d, 1 H, J ) 2.3), 6.52 (dd, 1 H, J ) 8.7, 2.4), 7.32
(d, 1 H, J ) 8.6), 12.7 (s, 1 H), 13.2 (br s, 1 H); 125 MHz 13C
NMR (DMSO-d6) δ 13.55, 18.55, 24.01, 30.44, 67.47, 82.35,
101.15, 107.16, 108.88, 131.46, 160.38, 162.87, 169.91, 173.60;
HRMS m/z calcd for C15H20NO4S, 310.1113 (M + H); found,
310.1112. Anal. (C15H19NO4S) C, H, N.
(S)-4,5-Dihydro-2-[2-hydroxy-4-(octyloxy)phenyl]-4-methyl-
4-thiazolecarboxylic Acid (7). A solution of 50% (w/w) NaOH (7.0
mL, 134 mmol) in CH3OH (70 mL) was added to 16 (4.28 g, 10.88
mmol) in CH3OH (100 mL) with ice bath cooling. The reaction mixture
was stirred at room temperature for 16 h, and the bulk of the solvent
was removed by rotary evaporation. The residue was treated with cold
dilute NaCl (50 mL), acidified with 1 N HCl to pH ∼2, and extracted
with EtOAc (4 × 80 mL). The EtOAc layers were washed with
saturated NaCl (100 mL) and were concentrated by rotary evaporation.
The residue was subjected to a Sephadex LH-20 column, eluting with
10% EtOH/toluene, to furnish 3.2 g of 7 (80%) as an off-white solid:
[R]20 +65.3 (c 0.294, CHCl3); 1H NMR (CD3OD) δ 0.90 (t, 3 H, J )
6.8), 1.25-1.52 (m, 10 H), 1.67 (s, 3 H), 1.72-1.82 (m, 2 H), 3.34
(d, 1 H, J ) 11.6), 3.86 (d, 1 H, J ) 11.2), 4.0 (t, 2 H, J ) 6.6), 6.45
(d, 1 H, J ) 2.4), 6.49 (dd, 1 H, J ) 8.8, 2.4), 7.38 (d, 1 H, J ) 9.2);
13C NMR (CD3OD) δ 14.49, 23.75, 24.77, 27.15, 30.26, 30.43, 30.50,
33.02, 40.56, 69.29, 84.18, 102.29, 108.08, 110.71, 132.83, 162.31,
165.03, 172.31, 176.08; HRMS m/z calcd. for C19H28NO4S, 366.1734
(M + H); found, 366.1728. Anal. (C19H27NO4S) C, H, N.
(S)-2-(5-Butoxy-2-hydroxyphenyl)-4,5-dihydro-4-methyl-4-
thiazolecarboxylic Acid (10). A solution of 50% (w/w) NaOH (17.96
g, 224 mmol) in CH3OH (125 mL) was added to 18 (4.81 g, 14.25
mmol) in CH3OH (125 mL) with ice bath cooling. The reaction mixture
was stirred at room temperature for 1 d, and the bulk of the solvent
was removed by rotary evaporation. The concentrate was treated with
dilute NaCl (165 mL) and was extracted with ether (3 × 60 mL). The
basic aqueous phase was cooled in ice, acidified with 2 N HCl (140
mL), and was extracted with EtOAc (150 mL, 2 × 80 mL). The EtOAc
extracts were washed with H2O (120 mL) and saturated NaCl (75 mL)
and were concentrated in vacuo. Drying under high vacuum at 69 °C
gave 4.40 g of a green, viscous oil, 3.94 g of which was chromato-
graphed on Sephadex LH-20 with 6% EtOH/toluene, affording 3.63
(S)-4,5-Dihydro-2-(4-ethoxy-2-hydroxyphenyl)-4-methyl-4-
thiazolecarboxylic Acid (5). A solution of 50% (w/w) NaOH (17.7
mL, 339 mmol) in CH3OH (215 mL) was added over 12 min to 14
(7.66 g, 24.76 mmol) in CH3OH (250 mL) with ice bath cooling.
The reaction mixture was stirred at room temperature for 18 h,
and the bulk of the solvent was removed by rotary evaporation.
The residue was treated with dilute NaCl (350 mL) and was
extracted with ether (3 × 100 mL). The basic aqueous phase was
cooled in ice, acidified with cold 2 N HCl (225 mL), and was
extracted with EtOAc (250 mL, 2 × 100 mL). The EtOAc extracts
were washed with saturated NaCl (120 mL) and were concentrated
in vacuo. Recrystallization from EtOAc/hexanes furnished 6.289
g of 5 (90%), as small yellow crystals, mp 191.5-192.5 °C: [R]23
1
(92%) of 10: [R]24 +15.6 (c 1.29, DMF); H NMR (DMSO-d6) δ
0.93 (t, 3 H, J ) 7.4), 1.38-1.48 (m, 2 H), 1.59 (s, 3 H), 1.63-1.71
(m, 2 H), 3.41 (d, 1 H, J ) 11.3), 3.83 (d, 1 H, J ) 11.7), 3.93 (t, 2
H, J ) 6.4), 6.87 (d, 1 H, J ) 2.7), 6.92 (d, 1 H, J ) 9.0), 7.09 (dd,
1 H, J ) 9.0, 2.7), 12.0 (s, 1 H), 13.3 (br s, 1 H); 13C NMR (DMSO-
d6) δ 13.75, 18.76, 24.01, 30.82, 39.64, 67.92, 83.01, 114.10, 115.34,
117.84, 121.27, 151.08, 152.56, 170.39, 173.63; HRMS m/z calcd for
C15H20NO4S (M
(C15H19NO4S) C, H, N.
+ H), 310.1108; found, 310.1108. Anal.
(S)-4,5-Dihydro-2-[2-hydroxy-5-(octyloxy)phenyl]-4-methyl-
4-thiazolecarboxylic Acid (11). A solution of 50% (w/w) NaOH
(0.70 mL, 13 mmol) in CH3OH (10 mL) was added to 20 (0.41 g,
1
+61.6° (c 1.20, DMF); H NMR (DMSO-d6) δ 1.32 (t, 3 H, J )
6.8), 1.58 (s, 3 H), 3.36 (d, 1 H, J ) 11.2), 3.79 (d, 1 H, J ) 11.6),

Desferrithiocin Analogues and Nephrotoxicity
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19 6001
1.0 mmol) in CH3OH (20 mL) with ice bath cooling. The reaction
mixture was stirred at room temperature for 20 h and was
concentrated by rotary evaporation. The residue was treated with
dilute NaCl (150 mL) and was extracted with ether (3 × 25 mL).
The basic aqueous phase was cooled in ice, acidified with 2 N HCl
(10 mL), and extracted with EtOAc (50 mL, 2 × 25 mL). The
EtOAc layers were washed with saturated NaCl (25 mL), and
solvent was removed in vacuo. Lyophilization furnished 0.35 g of
11 (96%) as a light-yellow oil: [R]20 +17.7° (c 0.192, CH3OH);
1H NMR (DMSO-d6) δ 0.86 (t, 3 H, J ) 6.8), 1.24-1.44 (m, 10
H), 1.59 (s, 3 H), 1.65-1.72 (m, 2 H), 3.41 (d, 1 H, J ) 11.2),
3.82 (d, 1 H, J ) 11.6), 3.92 (t, 2 H, J ) 6.8), 6.86-6.93 (m, 2
H), 7.08 (dd, 1 H J ) 8.8, 2.4), 11.97 (s, 1 H); 13C NMR (DMSO-
d6) δ 14.13, 22.27, 24.14, 25.65, 28.82, 28.90, 31.40, 68.37, 83.13,
114.25, 115.45, 117.99, 121.44, 151.19, 152.64, 170.53, 173.78;
HRMS m/z calcd for C19H27NO4S, 366.1734 (M + H); found,
366.1723. Anal. (C19H27NO4S) C, H, N.
column chromatography eluting with CH2Cl2 gave 3.18 g of 15
1
(94%) as a yellow oil: [R]25 +50.9 (c 1.02, CHCl3); H NMR δ
0.97 (t, 3 H, J ) 7.2), 1.30 (t, 3 H, J ) 7.2), 1.43-1.53 (m, 2 H),
1.66 (s, 3 H), 1.73-1.81 (m, 2 H), 3.19 (d, 1 H, J ) 11.3), 3.84 (d,
1 H, J ) 11.3), 3.98 (q, 2 H, J ) 6.4), 4.18-4.30 (m, 2 H), 6.43
(dd, 1 H, J ) 8.6, 2.7), 6.48 (d, 1 H, J ) 2.7), 7.28 (d, 1 H, J )
8.6), 12.68 (s, 1 H); 13C NMR δ 13.94, 14.23, 19.30, 24.61, 31.20,
39.95, 62.01, 68.01, 83.21, 101.33, 107.42, 109.67, 131.75, 161.34,
163.54, 170.91, 173.01; HRMS m/z calcd for C17H24NO4S, 338.1426
(M + H); found, 338.1447. Anal. (C17H23NO4S) C, H, N.
Ethyl (S)-4,5-Dihydro-2-[2-hydroxy-4-(octyloxy)phenyl]-4-
methyl-4-thiazolecarboxylate (16). Freshly prepared 0.51 M
sodium ethoxide (40 mL, 20.26 mmol) was added to a mixture of
13 (6.00 g, 21.33 mmol) and 1-iodooctane (4.14 g, 20.26 mmol)
in ethanol (15 mL). The reaction mixture was heated to 70 °C for
24 h and was concentrated in vacuo. The residue was taken up in
1:1 0.5 M citric acid/saturated NaCl (50 mL) and was extracted
with EtOAc (2 × 50 mL). The organic layers were washed with
100 mL portions of 0.5 M citric acid, 1% NaHSO3, H2O, and
saturated NaCl. After solvent removal by rotary evaporation, flash
column chromatography on silica gel eluting with 2% EtOAc/
CH2Cl2 furnished 5.10 g (64%) of 16 as light-yellow oil: [R]20
+49.3° (c 0.27, CHCl3); 1H NMR δ 0.89 (t, 3 H, J ) 7.2),
1.24-1.39 (m, 9 H), 1.40-1.48 (m, 4 H), 1.65 (s, 3 H), 1.74-1.82
(m, 2 H), 3.19 (d, 1 H, J ) 11.2), 3.83 (d, 1 H, J ) 11.6), 3.97 (t,
2 H, J ) 6.6), 4.24 (q, 2 H, J ) 6.8), 6.43 (dd, 1 H, J ) 8.8, 2.4),
6.48 (d, 1 H, J ) 2.4), 7.28 (d, 1 H, J ) 8.4), 12.7 (s, 1 H); 13C
NMR δ 14.24, 22.79, 24.62, 26.10, 29.18, 29.35, 29.45, 31.93,
39.96, 62.01, 68.35, 83.27, 101.35, 107.43, 109.68, 131.76, 161.35,
163.56, 170.92, 173.01; HRMS m/z calcd for C21H32NO4S, 394.2047
(M + H); found, 394.2050. Anal. (C21H31NO4S) C, H, N.
(S)-2-[4,5-Bis(octyloxy)-2-hydroxyphenyl]-4,5-dihydro-4-methyl-
4-thiazolecarboxylic Acid (12). A solution of 50% (w/w) NaOH
(1 mL, 19 mmol) in CH3OH (10 mL) was added to a solution of
27 (0.92 g, 1.76 mmol) in CH3OH (10 mL). The reaction mixture
was stirred at room temperature for 16 h, and the solvent was
removed by rotary evaporation. The residue was treated with dilute
NaCl (5 mL) and was acidified with 2 N HCl to pH ∼1. Extraction
with EtOAc (3 × 20 mL) and solvent removal in vacuo provided
0.80 g of 12 (92%) as a glassy yellow solid: [R]20 +36.2° (c 0.235,
CHCl3); 1H NMR δ 0.89 (2 t, 6 H, J ) 7.2), 1.24-1.38 (m, 16 H),
1.42-1.52 (m, 4 H), 1.72 (s, 3 H), 1.74-1.87 (m, 4 H), 3.24 (d, 1
H, J ) 11.2), 3.88 (d, 1 H, J ) 11.6), 3.91 (t, 2 H, J ) 6.8), 4.01
(t, 2 H, J ) 6.8), 6.56 (s, 1 H), 6.83 (s, 1 H), 9.38 (br s, 1 H); 13
C
NMR δ 14.24, 22.80, 22.82, 24.57, 26.11, 26.14, 29.02, 29.38,
29.42, 29.45, 29.52, 29.54, 31.93, 31.96, 39.78, 69.07, 71.06, 82.13,
101.38, 106.83, 116.07, 141.81, 155.67, 156.55, 172.58, 177.06;
HRMS m/z calcd for C27H44NO5S, 494.2935 (M + H); found,
494.2991. Anal. (C27H43NO5S) C, H, N.
Ethyl (S)-4,5-Dihydro-2-(2,5-dihydroxyphenyl)-4-methyl-4-
thiazolecarboxylate (17). Iodoethane (2.8 mL, 35 mmol) and DIEA
(6.2 mL, 35.6 mmol) were successively added to 8 (5.05 g, 19.9
mmol) in DMF (100 mL), and the solution was stirred at room
temperature for 1 d. After solvent removal under high vacuum, the
residue was treated with 1:1 0.5 M citric acid/saturated NaCl (200
mL) and was extracted with EtOAc (200 mL, 2 × 80 mL). The
combined extracts were washed with 0.25 M citric acid (100 mL),
1% NaHSO3 (100 mL), H2O (100 mL), and saturated NaCl (75
mL), and solvent was evaporated. Purification by flash column
chromatography using 8% EtOAc/CH2Cl2 furnished 4.96 g (88%)
Ethyl (S)-4,5-Dihydro-2-(4-ethoxy-2-hydroxyphenyl)-4-meth-
yl-4-thiazolecarboxylate (14). Flame activated K2CO3 (1.21 g, 8.76
mmol) and iodoethane (0.60 mL, 7.50 mmol) were successively
added to 13 (1.16 g, 4.12 mmol) in acetone (50 mL), and the
mixture was heated at 65 °C for 16 h. After the mixture was cooled
to room temperature, solids were filtered and washed with acetone
(100 mL), and the filtrate was concentrated by rotary evaporation.
The residue was dissolved in 1:1 0.5 M citric acid/saturated NaCl
(150 mL) followed by extraction with EtOAc (150 mL, 2 × 70
mL). The combined organic extracts were washed with 1% NaHSO3
(100 mL), H2O (100 mL), and saturated NaCl (70 mL) and were
concentrated in vacuo. Purification using flash column chromatog-
raphy eluting with 9% EtOAc/petroleum ether generated 1.07 g of
1
of 17 as an orange oil: [R]24 +43.6 (c 1.06, CHCl3); H NMR δ
1.30 (t, 3 H, J ) 7.0), 1.67 (s, 3 H), 3.23 (d, 1 H, J ) 11.3), 3.87
(d, 1 H, J ) 11.3), 4.20-4.31 (m, 2 H), 4.76 (s, 1 H), 6.88-6.92
(m, 3 H), 11.96 (s, 1 H); 13C NMR δ 14.16, 24.48, 40.13, 62.34,
83.70, 115.91, 118.05, 121.64, 148.07, 153.04, 171.43, 173.14;
HRMS m/z calcd for C13H16NO4S, 282.0800 (M + H); found,
282.0837. Anal. (C13H15NO4S) C, H, N.
1
14 (84%) as a yellow oil: [R]25 +54.8 (c 1.16, CHCl3); H NMR
δ 1.30 (t, 3 H, J ) 7.2), 1.42 (t, 3 H, J ) 7.0), 1.66 (s, 3 H), 3.19
(d, 1 H, J ) 10.9), 3.84 (d, 1 H, J ) 11.3), 4.05 (q, 2 H, J ) 7.0),
4.20-4.28 (m, 2 H), 6.43 (dd, 1 H, J ) 8.8, 2.5), 6.48 (d, 1 H, J
) 2.7), 7.29 (d, 1 H, J ) 8.6), 12.69 (s, 1 H); 13C NMR δ 14.22,
14.76, 24.60, 39.94, 62.02, 63.81, 83.21, 101.30, 107.38, 109.72,
131.80, 161.34, 163.33, 170.93, 173.00; HRMS m/z calcd for
C15H20NO4S, 310.1113 (M + H); found, 310.1109. Anal.
(C15H19NO4S) C, H, N.
Ethyl (S)-4,5-Dihydro-2-(4-butoxy-2-hydroxyphenyl)-4-meth-
yl-4-thiazolecarboxylate (15). Flame activated K2CO3 (1.541 g,
11.15 mmol) and 1-iodobutane (1.4 mL, 12.3 mmol) were succes-
sively added to 13 (2.831 g, 10.06 mmol) in acetone (95 mL), and
the mixture was heated at 65 °C for 16 h. Additional K2CO3 (0.620
g, 4.48 mmol) and 1-iodobutane (0.6 mL, 5.3 mmol) were added,
and the reaction mixture was heated at 70 °C for 20 h. After the
mixture was cooled to room temperature, solids were filtered and
washed with acetone (140 mL), and the filtrate was concentrated
by rotary evaporation. The residue was dissolved in 1:1 0.5 M citric
acid/saturated NaCl (150 mL) followed by extraction with EtOAc
(150 mL, 2 × 80 mL). The combined organic extracts were washed
with 1% NaHSO3 (100 mL), H2O (100 mL), and saturated NaCl
(50 mL) and were concentrated in vacuo. Purification using flash
Ethyl (S)-2-(5-Butoxy-2-hydroxyphenyl)-4,5-dihydro-4-meth-
yl-4-thiazolecarboxylate (18). Flame activated K2CO3 (1.888 g,
13.66 mmol) and 1-iodobutane (1.4 mL, 12.3 mmol) were succes-
sively added to 17 (1.85 g, 6.58 mmol) in acetone (35 mL), and
the mixture was heated at 69 °C for 16 h. After the mixture was
cooled to room temperature, solids were filtered and washed with
acetone (100 mL), and the filtrate was concentrated by rotary
evaporation. The residue was dissolved in 1:1 0.5 M citric acid/
saturated NaCl (100 mL) followed by extraction with EtOAc (100
mL, 2 × 60 mL). The combined organic extracts were washed with
1% NaHSO3 (80 mL), H2O (80 mL), and saturated NaCl (50 mL)
and were concentrated in vacuo. Purification using flash column
chromatography eluting with CH2Cl2 gave 4.86 g of 18 (79%): [R]24
+28.8° (c 1.16, CHCl3); 1H NMR δ 0.98 (t, 3 H, J ) 7.4), 1.30 (t,
3 H, J ) 7.2), 1.44-1.55 (m, 2 H), 1.67 (s, 3 H), 1.71-1.79 (m,
2 H), 3.23 (d, 1 H, J ) 11.3), 3.88 (d, 1 H, J ) 11.3), 3.92 (t, 2 H,
J ) 6.4), 4.20-4.29 (m, 2 H), 6.90 (d, 1 H, J ) 3.1), 6.93 (d, 1 H,
J ) 9.0), 6.99 (dd, 1 H, J ) 9.0, 2.7), 11.97 (s, 1 H); 125 MHz
13C NMR δ 14.00, 14.24, 19.39, 24.56, 31.54, 40.19, 62.13, 68.85,
83.85, 115.01, 115.88, 118.08, 121.48, 151.62, 153.60, 171.42,
172.79; HRMS m/z calcd for C17H24NO4S, 338.1426 (M + H);
found, 338.1436. Anal. (C17H23NO4S) C, H, N.

6002 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19
Bergeron et al.
Isopropyl (S)-4,5-Dihydro-2-[2-hydroxy-5-(octyloxy)phenyl]-
4-methyl-4-thiazolecarboxylate (20). Sodium (0.084 g, 3.65 mmol)
was introduced to i-PrOH (10 mL) with ice bath cooling, and the
solution was added to 1-iodooctane (0.88 g, 3.66 mmol) and 19
(1.10 g, 3.72 mmol). The reaction mixture was heated to 70 °C for
24 h and was concentrated in vacuo. The residue was taken up in
EtOAc (50 mL), which was washed with 25 mL portions of 0.1 M
citric acid, 1% NaHSO3, H2O, and saturated NaCl. After solvent
was removed by rotary evaporation, column chromatography on
silica gel, eluting with 1% EtOAc/CH2Cl2, afforded 0.53 g (35%)
of 20 as a light-yellow oil: [R]20 +24.1° (c 0.32, CHCl3); 1H NMR
δ 0.89 (t, 3 H, J ) 6.8), 1.24-1.39 (m, 14 H), 1.40-1.49 (m, 2
H), 1.65 (s, 3 H), 1.73-1.80 (m, 2 H), 3.21 (d, 1 H, J ) 11.6),
3.86 (d, 1 H, J ) 11.2), 3.91 (t, 2 H, J ) 6.8), 5.08 (m, 1 H),
6.89-6.96 (m, 3 H), 11.98 (s, 1 H); 13C NMR δ 14.23, 21.71,
22.77, 24.37, 26.14, 29.35, 29.43, 29.49, 31.93, 39.99, 69.05, 69.67,
83.83, 114.86, 115.83, 117.99, 121.30, 151.50, 153.51, 171.18,
172.16; HRMS m/z calcd for C22H33NNaO4S, 430.2028 (M + Na);
found, 430.2072. Anal. (C22H33NO4S) C, H, N.
3,4-Bis(octyloxy)phenol (22). Methanol (100 mL), 35% hydro-
gen peroxide (6.6 g, 68 mmol), and concentrated H2SO4 (0.6 mL,
11 mmol) were added to 2157 (10.0 g, 27.58 mmol) in CHCl3 (250
mL), and the reaction mixture was stirred at room temperature for
6 h. Water was added until two layers formed. The organic layer
was washed with H2O (100 mL), dried over MgSO4, filtered, and
concentrated in vacuo. Recrystallizion from hexane/CH2Cl2 gave
9.3 g (96%) of 22 as a solid: 600 MHz 1H NMR δ 0.88 (2 t, 6 H,
J ) 7.1), 1.23-1.37 (m, 16 H), 1.40-1.48 (m, 4 H), 1.71-1.83
(m, 4 H), 3.91 (t, 2 H, J ) 6.6), 3.93 (t, 2 H, J ) 6.5), 4.66 (s, 1
H), 6.30 (dd, 1 H, J ) 8.5, 2.8), 6.44 (d, 1 H, J ) 2.8), 6.75 (d, 1
H, J ) 8.5); 150 MHz 13C NMR δ14.10, 22.68, 26.06, 29.22, 29.29,
29.30, 29.38, 29.43, 29.55, 31.84, 31.85, 69.04, 70.83, 102.32,
106.14, 116.43, 143.08, 150.43, 150.61; HRMS m/z calcd for
C22H39O3, 351.2894 (M + H); found, 351.2884. Anal. (C22H38O3)
C, H.
4,5-Bis(octyloxy)-2-hydroxybenzonitrile (25). Compound 24
(1.88 g, 4.78 mmol) was treated with acetic anhydride (4.1 mL)
and heated at reflux for 16 h. The reaction mixture was concentrated
under high vacuum and was partitioned between CHCl3 (30 mL)
and 8% NaHCO3 (25 mL). The aqueous layer was further extracted
with CHCl3 (2 × 20 mL), and the combined organic phase was
washed with 4% NaHCO3 (50 mL) and saturated NaCl (50 mL)
followed by solvent removal. The residue was treated with a 50%
NaOH (1.5 mL, 29 mmol) in CH3OH (30 mL). After the mixture
was stirred for 16 h at room temperature, solvents were removed
under reduced pressure. The concentrate was treated with 2 N HCl
(10 mL) and was extracted with EtOAc (3 × 50 mL). The EtOAc
layers were washed with saturated NaCl (100 mL) and were
concentrated in vacuo, providing 1.29 g (72%) of 25, as a white
1
solid: H NMR δ 0.88 (2 t, 6 H, J ) 7.2), 1.22-1.39 (m, 16 H),
1.40-1.50 (m, 4 H), 1.74-1.86 (m, 4 H), 3.91 (t, 2 H, J ) 6.6),
3.96 (t, 2 H, J ) 6.6), 6.48 (s, 1 H), 6.87 (s, 1 H); 13C NMR δ
14.21, 22.77, 26.03, 26.06, 28.91, 29.29, 29.34, 29.37, 29.40, 29.45,
31.90, 31.92, 69.21, 70.54, 88.78, 101.70, 116.18, 117.38, 142.99,
155.34, 155.50; HRMS m/z calcd for C23H37NNaO3, 398.2671 (M
+ Na); found, 398.2645. Anal. (C23H37NO3) C, H, N.
Ethyl (S)-2-[4,5-Bis(octyloxy)-2-hydroxyphenyl]-4,5-dihydro-
4-methyl-4-thiazolecarboxylate (27). Compound 26 (0.767 g, 4.47
mmol), pH 6 phosphate buffer (30 mL), and NaHCO3 (0.482 g,
5.74 mmol) were successively added to a solution of 25 (1.2 g,
3.19 mmol) in degassed CH3OH (30 mL). The reaction mixture
was heated at 70 °C for 48 h with stirring, cooled to room
temperature, and concentrated by rotary evaporation. The residue
was dissolved in 8% NaHCO3 (20 mL) and was extracted with
ether (2 × 20 mL). The aqueous layer was acidified with cold 2 N
HCl to pH ∼2 followed by extraction with EtOAc (4 × 30 mL).
The latter organic layers were washed with saturated NaCl (50 mL)
and concentrated in vacuo, resulting in 1.45 g of 12. Iodoethane
(0.569 g, 3.65 mmol) and DIEA (0.471 g, 3.65 mmol) were
successively added to 12 (1.0 g, 2.03 mmol) in DMF (20 mL), and
the solution was stirred at room temperature for 48 h. After solvent
removal under high vacuum, the residue was treated with 1:1 0.5
M citric acid/saturated NaCl (25 mL) followed by extraction with
EtOAc (4 × 20 mL). The EtOAc layers were washed with 50 mL
portions of 1% NaHSO3, H2O, and saturated NaCl, and the solvent
was evaporated. Purification by flash column chromatography using
10% EtOAc/hexane gave 0.93 g of 27 (90%) as a yellow oil: [R]20
+32.0° (c 0.24, CHCl3); 1H NMR δ 0.89 (2 t, 6 H, J ) 6.8),
1.24-1.38 (m, 16 H), 1.42-1.52 (m, 4 H), 1.65 (s, 3 H), 1.74-1.87
(m, 4 H), 3.19 (d, 1 H, J ) 11.2), 3.84 (d, 1 H, J ) 11.6), 3.93 (t,
2 H, J ) 6.6), 4.00 (t, 2 H, J ) 6.8), 4.24 (dq, 2 H, J ) 6.8, 1.2),
6.49 (s, 1 H), 6.86 (s, 1 H), 12.41 (br s, 1 H); 13C NMR δ 14.22,
14.24, 22.79, 22.80, 24.62, 26.10, 26.14, 29.05, 29.38, 29.42, 29.44,
29.54, 29.57, 31.93, 31.96, 40.07, 61.99, 68.91, 71.14, 83.31,
101.27, 107.57, 116.45, 141.58, 154.78, 156.00, 170.75, 173.02;
HRMS m/z calcd for C29H48NO5S, 522.3248 (M + H); found,
522.3231. Anal. (C29H47NO5S) C, H, N.
4,5-Bis(octyloxy)-2-hydroxybenzaldehyde (23). Hexamethyl-
enetetramine (3.60 g, 25.72 mmol) was added to a solution of 22
(9.0 g, 25.67 mmol) in anhydrous TFA (25 mL). The reaction
mixture was heated at reflux using an oil bath at 100 °C for 16 h
and then cooled to room temperature. Cold 1 N HCl (50 mL) was
added, and stirring was continued for 15 min. The aqueous layer
was extracted with CH2Cl2 (2 × 100 mL). The combined organic
layers were washed with 1 N HCl (50 mL) and then saturated NaCl
(50 mL) and were concentrated in vacuo. Column chromatography
eluting with 50% CH2Cl2/hexanes generated 3.80 g of 23 (39%)
1
as a yellow solid: 600 MHz H NMR δ 0.89 (2 t, 6 H, J ) 6.9),
1.25-1.39 (m, 16 H), 1.44-1.50 (m, 4 H), 1.79 (quintet, 2 H, J )
7.7), 1.85 (quintet, 2 H, J ) 7.8), 3.95 (t, 2 H, J ) 6.6), 4.03 (t, 2
H, J ) 6.6), 6.42 (s, 1 H), 6.93 (s, 1 H), 9.65 (s, 1 H), 11.36 (s, 1
H); 150 MHz 13C NMR δ 14.09, 14.10, 22.66, 22.68, 25.94, 26.03,
28.80, 29.23, 29.27, 29.29, 29.35, 29.39, 31.80, 31.84, 69.17, 70.55,
100.80, 112.89, 116.93, 142.51, 158.03, 159.56, 193.92; HRMS
m/z calcd for C23H38NaO4, 401.2668 (M + Na); found, 401.2627.
Anal. (C23H38O4) C, H.
Acknowledgment. The project described was supported by
Grant Number R37DK049108 from the National Institute of
Diabetes and Digestive and Kidney Diseases. The content is
solely the responsibility of the authors and does not necessarily
represent the official views of the National Institute of Diabetes
and Digestive and Kidney Diseases or the National Institutes
of Health. We thank Elizabeth M. Nelson, Tanaya Lindstrom,
and Katie Ratliff-Thompson for their technical assistance and
Carrie A. Blaustein for her editorial and organizational support.
We acknowledge the spectroscopy services in the Chemistry
Department, University of Florida, for the mass spectrometry
analyses.
4,5-Bis(octyloxy)-2-hydroxybenzaldoxime (24). Hydroxylamine
hydrochloride (0.52 g, 7.5 mmol) and NaOAc (0.62 g, 7.5 mmol)
were added to a solution of 23 (1.89 g, 4.99 mmol) in CH3OH (10
mL), and the reaction mixture was heated at reflux for 1 h. Solvent
was removed by rotary evaporation; the residue was treated with
0.05 M citric acid/saturated NaCl (60 mL) and was extracted with
EtOAc (4 × 50 mL). The organic phase was washed with H2O (50
mL) and saturated NaCl (50 mL) and concentrated in vacuo to
1
generate 1.88 g (96%) of 24, as a pale yellow solid: H NMR δ
0.88 (2 t, 6 H, J ) 6.7), 1.25-1.50 (m, 20 H), 1.79-1.85 (m, 4
H), 3.93 (t, 2 H, J ) 6.6), 3.99 (t, 2 H, J ) 6.6), 6.51 (s, 1 H), 6.68
(s, 1 H), 8.09 (s, 1 H); 13C NMR δ 14.15, 14.19, 22.77, 26.09,
26.10, 29.08, 29.36, 29.38, 29.43, 29.50, 29.52, 31.91, 31.93, 68.94,
71.12, 101.74, 107.79, 116.94, 141.97, 152.45, 153.34, 168.16;
HRMS m/z calcd for C22H39O3, 394.2952 (M + H); found,
394.2935.
Supporting Information Available: Elemental analytical data
for synthesized compounds. This material is available free of charge
via the Internet at http://pubs.acs.org.

Desferrithiocin Analogues and Nephrotoxicity
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19 6003
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