The 'Ethereal' nature of TLR4 agonism and antagonism in the AGP class of lipid A mimetics

Article abstract of DOI:10.1016/j.bmcl.2008.09.060

To overcome the chemical and metabolic instability of the secondary fatty acyl residues in the AGP class of lipid A mimetics, the secondary ether lipid analogs of the potent TLR4 agonist CRX-527 (2) and TLR4 antagonist CRX-526 (3) were synthesized and evaluated along with their ester counterparts for agonist/antagonist activity in both in vitro and in vivo models. Like CRX-527, the secondary ether lipid 4 showed potent agonist activity in both murine and human models. Ether lipid 5, on the other hand, showed potent TLR4 antagonist activity similar to CRX-526 in human cell assays, but did not display any antagonist activity in murine models and, in fact, was weakly agonistic. Glycolipids 2, 4, and 5 were synthesized via a new highly convergent method utilizing a common advanced intermediate strategy. A new method for preparing (R)-3-alkyloxytetradecanoic acids, a key component of ether lipids 4 and 5, is also described.

Full text of DOI:10.1016/j.bmcl.2008.09.060

Bioorganic & Medicinal Chemistry Letters 18 (2008) 5350–5354
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
The ‘Ethereal’ nature of TLR4 agonism and antagonism in the AGP class
of lipid A mimetics
Hélène G. Bazin, Tim J. Murray, William S. Bowen, Afsaneh Mozaffarian, Steven P. Fling, Laura S. Bess,
Mark T. Livesay, Jeffrey S. Arnold, Craig L. Johnson, Kendal T. Ryter, Christopher W. Cluff, Jay T. Evans,
*
David A. Johnson
GlaxoSmithKline Biologicals, 553 Old Corvallis Road, Hamilton, MT 59840, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 July 2008
Revised 12 September 2008
Accepted 16 September 2008
Available online 19 September 2008
To overcome the chemical and metabolic instability of the secondary fatty acyl residues in the AGP class
of lipid A mimetics, the secondary ether lipid analogs of the potent TLR4 agonist CRX-527 (2) and TLR4
antagonist CRX-526 (3) were synthesized and evaluated along with their ester counterparts for agonist/
antagonist activity in both in vitro and in vivo models. Like CRX-527, the secondary ether lipid 4 showed
potent agonist activity in both murine and human models. Ether lipid 5, on the other hand, showed
potent TLR4 antagonist activity similar to CRX-526 in human cell assays, but did not display any antag-
onist activity in murine models and, in fact, was weakly agonistic. Glycolipids 2, 4, and 5 were synthe-
sized via a new highly convergent method utilizing a common advanced intermediate strategy. A new
method for preparing (R)-3-alkyloxytetradecanoic acids, a key component of ether lipids 4 and 5, is also
described.
Keywords:
Lipid A mimetics
TLR4 agonist
TLR4 antagonist
AGP
Ó 2008 Elsevier Ltd. All rights reserved.
Glycolipids
Immunostimulants
Reductive alkylation
The discovery of toll-like receptors (TLRs) on cells of the im-
mune system together with the identification of natural TLR li-
gands has led to a great deal of interest in developing synthetic
TLR agonists and antagonists to manipulate innate and adaptive
immune responses.1–3 Targeting TLR receptors and cognate intra-
cellular pathways could potentially lead to more effective vaccines
and novel therapeutic approaches for the treatment of immune
and inflammatory diseases. For example, certain variants of lipo-
polysaccharide (LPS), the main cell-surface component of Gram-
negative bacteria, are potent stimulators of host defense systems
via their interaction with TLR4 and accessory molecules such as
MD-2, but the pathophysiology of LPS and its active principle, lipid
A (1, Fig. 1), have precluded their medicinal use.4 Thus, consider-
able effort has been directed towards the development of synthetic
lipid A mimetics with simplified structures and improved toxicity/
activity profiles for use as vaccine adjuvants and stand-alone
immunotherapeutics.5
close packing8 of fatty acid moieties, facilitating intercalation of
the lipids into the hydrophobic pocket of the TLR4 accessory mol-
ecule MD-2. Further, the carboxyl group of seryl-based AGPs serves
as a stable bioisostere of the labile anomeric phosphate of lipid A,
and—along with the sugar 4-phosphate—presumably binds elec-
trostatically to lysines 128 and 132 along the edge of the hydro-
phobic pocket of MD-2.9 Crystal structures of disaccharide lipid A
antagonists bound to human MD-2 or the TLR4–MD-2 complex
show that these and other positively charged amino acids at the
edge of the hydrophobic pocket interact electrostatically with the
phosphate groups and that the pocket has evolved to accommo-
date large and structurally diverse fatty acyl moieties.10,11 Both
the spacial arrangement of the acyl moieties and distance between
anionic groups appear to be critical determinants for binding of
TLR4 agonists and antagonists to MD-2.12 Secondary fatty acid
chain length in the AGP series, on the other hand, appears to deter-
mine the ability of the putative9 AGP:MD-2 complexes to subse-
quently activate TLR4 and trigger oligomerization of TLR4
molecules.12,13 Oligomerization—aggregation of TLR4 molecules
into lipid rafts—is thought to be prerequisite to signal transduction
and the release of pro-inflammatory cytokines and chemokines
associated with the innate immune response.14
In the course of our own structure–activity studies on lipid A,6,7
we identified a new class of potent monosaccharide immunomod-
ulators known as aminoalkyl glucosaminide 4-phosphates (AGPs),
in which the less-conserved reducing sugar unit of lipid A is substi-
tuted with a flexible N-acyloxyacyl aglycon unit (e.g., 2 and 3,
Fig. 1).7 The flexible AGP motif likely permits energetically favored
Among seryl-based AGPs, CRX-527 (2) containing 10-carbon
secondary acyl residues and CRX-526 (3) possessing 6-carbon acyl
groups have been shown to exhibit potent TLR4 agonist and antag-
onist activity, respectively, in both murine and human mod-
* Corresponding author. Tel.: +1 406 375 2134; fax: +1 406 363 6214.
E-mail address: david.a.johnson@gskbio.com (D.A. Johnson).
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.09.060

H. G. Bazin et al. / Bioorg. Med. Chem. Lett. 18 (2008) 5350–5354
5351
O
P
O
P
OH
O
OH
O
O
P
OH
O
CO2H
NH
CO2H
NH
HO
HO
HO
HO
HO
O
O
O
HO
O
O
O
O
HO
O
O
O
O
O
O
O
O
O
O
P
NH
NH
NH
O
O
OH
OH
O
O
NH
O
O
R
O
O
R
O
R
O
O
O
O
O
O
O
O
R
O
HO
O
HO
R
R
2 R = n-C9H19 CRX-527
3 R = n-C5H11 CRX-526
4 R = n-C9H19
5 R = n-C5H11
1 E. coli lipid A
Figure 1. Structures of Escherichia coli lipid A (1) and AGP lipid A mimetics 2–5.
els.12,13,15 For example, the anti-infective effects of CRX-527 were
demonstrated recently in a preclinical model for respiratory syncy-
tial virus (RSV), a significant pathogen in humans—particularly in-
fants, immunocompromised patients, and the elderly.16 In
contrast, CRX-526 was recently shown to inhibit moderate-to-se-
vere disease in murine models of inflammatory bowel disease
(IBD).15 Increased TLR4 expression on the intestinal epithelium of
human IBD patients may play a key role in the etiology of this
disease.17
multi-step and/or low yielding. Application of the Bajwa–Komatsu
reductive alkylation procedure25,26 to silyl ester 7 derived from hy-
droxy ester 627 using decanal or hexanal in the presence of bis-
muth tribromide and triethylsilane (in situ-formation of
bromotriethylsilane)26 reproducibly gave ether esters 8 and 9 in
70–80% yield on a multi-gram scale along with minor amounts of
(separable) hydroxy ester 6. Base hydrolysis (or reductive depro-
tection)27 of the p-bromophenacyl esters 8 and 9 then gave the de-
sired acids 10 and 11 in >90% yield.28
In an the effort to overcome the inherent chemical and meta-
bolic instability of the ester-linked secondary fatty acids present
in lipid A mimetics18,19 such as CRX-527 (2) and CRX-526 (3) as
well as to further evaluate structural modifications in the AGP ser-
ies, the corresponding ether lipid analogs 4 and 5 (Fig. 1) were syn-
thesized and evaluated for agonist/antagonist activity in both
in vitro and in vivo models.
The target compounds 2, 4, and 5 were assembled from the gly-
cosyl donor/acceptor pair 12/13 using the N-2,2,2-trichloroethoxy-
carbonyl (Troc) method for stereoselective b-glycosylation in the
first step to give b-glycoside 14 in high yield (Scheme 2). To cir-
cumvent transesterification during O-deacetylation, the benzyl
group of 14 was removed hydrogenolytically prior to base-induced
deacetylation and subsequently re-installed under phase-transfer
conditions; 6-O-silylation then gave CAI 15 in 59% overall yield
from 12. Selective carbodiimide-mediated 3-O-acylation of 15 with
(R)-3-decanoyloxytetradecanoic acid,27 10 or 11, followed by
reductive removal of the N-Troc groups and N,N-diacylation with
the appropriate fatty acid, provided triacyl derivatives 19–21.
Compounds 19–21 could also be prepared directly from 15 via
Troc-deprotection and selective27 N,N,O-triacylation, but Troc re-
moval with Zn/AcOH typically led to emulsions during aqueous
workup (required to remove complexed zinc) and low recoveries
of the intermediate diamino diol. Phosphorylation of 19–21 and si-
lyl deprotection gave final intermediates 22–24, which were de-
benzylated by catalytic hydrogenation to afford the desired seryl
AGPs 2, 4, and 5 in >95% purity after silica gel chromatography
and lyophilization of the free acids from aqueous tert-butanol con-
taining triethylamine.29
Earlier, we described the synthesis of CRX-526 and CRX-527 in
15 steps from b-D
-glucosamine pentaacetate,7 but the synthesis
was low yielding and suffered from a number of drawbacks. Most
notably, incorporation of two of the three (R)-3-alkanoyloxytetra-
decanoyl residues onto the AGP scaffold early in the synthesis
led to multiple synthetic and chromatographic steps and precluded
the use of a common advanced intermediate (CAI) for the synthesis
of AGPs comprising the same sugar and aglycon units but different
fatty acyl substituents.
Herein, we describe a new, efficient synthesis of CRX-527 (2) as
well as ether lipid analogs 4 and 5 in 11 linear steps from readily
available 1,3,4,6-tetra-O-acetyl-2-deoxy-2-(2,2,2-trichloroethoxy-
carbonylamino)-b-
trichloroethoxycarbonyl)-
D
-glucopyranoside (12)20 and benzyl N-(2,2,2-
L
-serine (13).21 This new synthesis,
which is convergent with respect to the AGP backbone and the
fatty acid moieties, utilizes a CAI strategy to introduce the fatty
acyl groups near the end of the synthesis. As part of the effort to
make the synthesis of ether lipids 4 and 5 more amenable to large
scale, a new method for preparing the (R)-3-alkyloxytetradecanoic
acids 10 and 11 was also developed (Scheme 1).
CRX-527 (2) and its ether analog 4 were compared for their abil-
ity to induce cytokine production in human primary monocytic
cells as well as their ability to enhance non-specific resistance in
mice to Listeria monocytogenes and influenza infections. The activ-
ities of CRX-527 and ether lipid 4 were similar in these models, as
Although several methods have been reported22–24 for the syn-
thesis of (R)-3-alkyloxytetradecanoic acids we found these to be
exemplified by the induction of TNF-a in human monocytes (Table
1), the reduction of splenic bacteria following Listeria challenge
Br
R2
O
Br
OR1
O
R2
O
O
c
b
CO2H
n-C H23
O
n-C H23
11
n-C11H23
a
O
11
O
O
R2 = n-C9H19
= n-C5
6
7
R1 = H
R1 = TBDMS
10 R2 = n-C9H19
11 R2 = n-C5H11
8
9
R2
H
Scheme 1. Reagents: (a) TBDMS-Cl, imid, DMAP, CH2Cl2, 97%; (b) R2CHO, BiBr3, Et3SiH, CH3CN, 70% (8), 82% (9); (c) aq LiOH, THF, 90% (10), 100% (11).

5352
H. G. Bazin et al. / Bioorg. Med. Chem. Lett. 18 (2008) 5350–5354
OTBDMS
OAc
O
CO2Bn
NHTroc
OAc
O
a
CO2Bn
NHTroc
b-e
HO
HO
CO2Bn
NHTroc
O
O
AcO
AcO
AcO
AcO
O
OAc
NHTroc
+
HO
NHTroc
15
NHTroc
13
12
14
Common Advanced Intermediate
f
O
P
OH
OTBDMS
O
OTBDMS
2
BnO
BnO
CO2Bn
NH
CO2Bn
NH
CO2Bn
O
O
O
HO
O
O
O
O
HO
O
i, j
g, h
k
O
O
RO
O
NHTroc
NH
NH
4
5
NHTroc
O
RO
O
O
O
O
RO
n-C H23
n-C H23
11
11
RO
n-C H23
RO
RO
RO
n-C H23
11
n-C H23
n-C11H23
11
n-C H23
11
11
22 R = n-C9H19CO
23 R = n-C9H19CH2
24 R = n-C5H11CH2
19 R = n-C9H19CO
20 R = n-C9H19CH2
21 R = n-C5H11CH2
16 R = n-C9H19CO
17 R = n-C9H19CH2
18 R = n-C5H11CH2
Scheme 2. Reagents and conditions: (a) BF3–OEt2 (2 equiv), CH2Cl2, 87%; (b) 5% Pd/C, H2, THF; (c) NH4OH, MeOH, 76% (2 steps); (d) BnBr, n-Bu4NBr, CH2Cl2, aq NaHCO3; (e)
TBDMS-Cl, pyr, 89% (2 steps); (f) (R)-3-decanoyloxytetradecanoic acid, 10, or 11, (1 equiv), EDC–MeI (1 equiv), DMAP (0.03 equiv), CH2Cl2, 0 °C ? rt, 2 h, 85% (16), 83% (17),
69% (18); (g) Zn, AcOH, rt, aq THF; (h) (R)-3-decanoyloxytetradecanoic acid, 10, or 11 (2 equiv), EDC–MeI (2 equiv), DMAP (0.03 equiv), CH2Cl2, rt, 66% (19), 42% (20), 48% (21)
(2 steps); (i) i—(BnO)2PNi-Pr2 (1.4 equiv), 4,5-dicyanoimidazole (1.4 equiv), CH2Cl2, rt; ii—m-chloroperbenzoic acid (3 equiv), 0 °C; (j) TFA, CH2Cl2, rt, 71% (23), 59% (24), 85%
(25) (2 steps); (k) 5% Pd(OH)2/C, H2, THF, 65% (2), 85% (4), 80% (5).
Table 1
3
Comparison of the TLR4 agonist activities of CRX-527 (2) and ether lipid 4 and the
antagonist activities of CRX-526 (3) and 5 in primary human monocytes
2.5
Compound TNF-
a
induction in monocytesa
TNF-a
inhibition in monocytesb
IC50, nM (95% CI)
2
1.5
1
ED50, nM (95% CI)
2
4
3
5
0.39 (0.11–0.89)
0.17 (0.07–0.41)
—
—
—
—
CRX-527
2.40 (1.34–6.13)
5.30 (2.87–13.46)
Ether Analog 4
0.5
0
a
Human PBMCs were isolated from whole blood by ficoll-hypaque (Sigma
HistopaqueTM-1077) density gradient. Monocytes were isolated by 2 h adherence to
tissue culture treated plated and stimulated with 0–10,000 nV of compound in 0.2%
aq triethanolamine (TEOA) for 18 h. Supernatants were analyzed for TNF-a induc-
0.001
0.01
0.1
1
AGP Dose (ug):
tion by sandwich ELISA. The results are shown from three replicate samples of one
of three donors tested with similar results. ED50 values were calculated by fitting
data to a four parameter logistic, dose–response model in XLfitTM (IBDS).
Figure 2. Potency comparison of CRX-527 to ether analog 4 in murine intravenous
L. monocytogenes protection model. BALB/c mice received AGP in 100 lL of 0.2% aq
TEOA by iv administration 2 days prior to iv challenge with 105 L. monocytogenes;
CFUs were determined 2 days later by serial dilutions of splenic homogenates. log10
relative protection was calculated by subtracting CFUs/spleen (log10 value) in test
group from CFUs/spleen (log10 value) in control group.
b
Monocytes were incubated with compound for 30 min and then stimulated
with 100 ng/mL E. coli LPS. TNF-a levels were determined in supernatants taken
after 18 h by ELISA and IC50 values were determined as for ED50 values above.
(Fig. 2), and survival to lethal influenza challenge (Table 2). Nota-
bly, intranasal administration of 5 lg of CRX-527 or 4 two days
prior to lethal influenza challenge provided 100% protection in
Table 2
Comparison of the protection from influenza challenge by administration of CRX-527
(2) or 4
each case, and significant protection at lower doses.
Compound
Dosea
(lg)
% Survivalb
In contrast to CRX-527 (2) and its ether analog 4, neither CRX-
526 (3) nor its ether analog 5 induced detectable cytokines in hu-
man cell assays (data not shown). However, both of these AGPs
equally inhibited the LPS-induced production of TNF-
monocytes (Table 1).
TLR4 antagonist CRX-526 (3) and its ether lipid analog 5 were
also evaluated for their ability to inhibit LPS induction of TNF-
in mice and for their ability to antagonize CRX-527-mediated pro-
0.2% TEOA
—
5.0
0.5
0.05
0.005
5.0
0.5
0.05
0.005
0
100
70
70
30
100
80
60
2
2
2
2
4
4
4
4
a in human
a
20
tection against intravenous L. monocytogenes challenge in mice.
a
BALB/c mice (8/group) received indicated dose of AGP in 20
l
L of 0.2% aq TEOA
CRX-526 (3) effectively inhibited serum TNF-
a production when
by intranasal (in) administration 2 days prior to in influenza challenge (2 ꢀ LD50
co-administered intravenously with LPS but 5 did not demonstrate
any antagonist activity (Fig. 3).
infectious influenza A/HK/68).
b
Survival was recorded for 21 days post-viral challenge.
Similarly, CRX-526, but not its ether analog 5, antagonized CRX-
527-mediated protection against intravenous bacterial challenge
in mice in a dose-dependent manner (Fig. 4). A dose–response
comparison of ether lipid 5 and CRX-527 in the Listeria protection
model showed that 5 was about 100 times less potent (i.e., moder-
ately protective) than CRX-527 in reducing splenic bacteria follow-
ing Listeria challenge (data not shown). The weak TLR4 agonist
activity of ether lipid 5 in mice is further exemplified by its ability

H. G. Bazin et al. / Bioorg. Med. Chem. Lett. 18 (2008) 5350–5354
5353
to induce TNF-
comparison of serum TNF-
lipid 5 showed 5 was between 10 and 100 times less active than
CRX-527 as a TLR4 agonist in mice (Fig. 5).
a
when administered iv to mice: a dose–response
levels induced by CRX-527 and ether
1500
1000
500
0
a
The observed species-specific agonist/antagonist activity of
ether lipid 5 is reminiscent of what has been reported for lipid
IVa, a biosynthetic precursor of lipid A, and is likely attributable
to species differences in the structure of MD-2,30,31 particularly
amino acids 57, 61, and 122 located in close proximity to each
other along the edge of the hydrophobic pocket.32 In fact, the co-
crystal structure of human MD-2 and lipid IVa shows hydrogen
bonding between Lys122 and the 20-acyl carbonyl oxygen of lipid
IVa as well as hydrogen bonds between the nearby Ser120 residue
and the 20-and 1-acyl groups.10 Thus, it is possible that one or more
of the secondary ester carbonyls of CRX-526 (3), which are not
present in lipid IVa or ether lipid 5, affect H-bonding of the acyl
groups to this domain in murine MD-2 (which possesses Glu122
in place of Lys122 among other substitutions) and prevent confor-
mational changes in MD-2 required for TLR4 activation/
oligomerization.
PBS
5 ng
LPS
Vehicle
3
5
5 ng LPS
Figure 3. Capacity of CRX-526 (3) and ether lipid 5 to inhibit LPS-induced serum
TNF- production in BALB/c mice (n = 3) challenged with LPS. BALB/c mice were
administered LPS alone or with 0.2% TEOA vehicle, 3 or 5 via iv administration.
a
Serum was collected at 1.5 h post-injection and evaluated for TNF-
a
by ELISA.
In summary, an improved synthesis of the potent TLR4 agonist
CRX-527 (2) has been developed in 11 linear steps and 15% overall
yield from b-acetate 12 and serine 13. This synthesis, which em-
ploys common advanced intermediate 15, was also applied to the
synthesis of novel ether lipids 4 and 5. A new method for preparing
(R)-3-alkyloxytetradecanoic acids, a key component of ether lipids
4 and 5, was also developed using Bajwa–Komatsu reductive alkyl-
ation of silyl ether 7 in the key step.
Ether lipids 4 and 5 exhibited similar TLR4 agonist and antagonist
activities, respectively, to their ester analogs 2 and 3 in human cell
assays; however, unlike the potent TLR4 antagonist CRX-526, ether
lipid 5 was a weak agonist in murine models, suggesting that one
ormoreof theestercarbonylsinCRX-526playsa pivotalroleinbind-
ing to murine MD-2 at the entrance to the hydrophobic pocket and
preventing TLR4 activation. As with subtle structural changes in
MD-2,11 slight modifications to the TLR4 ligand can also have a sig-
nificant impact on the activation of the TLR4–MD-2 complex.
2
1.5
1
0.5
0
)
)
)
)
)
g
g
u
u
ug)
ug)
1
1
1
.
1
0 ug
1
1 ug
0 ug
.
(
(
0
1
(
0
0
.
(
(
5
(
0
26
5
5
(
5
26
+
26
+
og
-
5
-
5
og
X
al
-
og
527
R
n
X
-
al
X
al
X
A
R
n
R
n
C
R
+
)
C
A
C
+
)
A
C
+
+
0
)
)
)
)
ug
1 ug
1
0
.
0
.
0
1 ug
1 ug
1 ug
1 ug
0
.
0
.
0
0
0
.
.
(
(
0
0
(
0
(
(
(
527
527
-
-
527
527
527
527
-
X
X
-
-
X
-
X
R
R
X
X
C
C
R
R
R
R
C
C
C
C
Acknowledgments
Figure 4. Inhibition of CRX-527-mediated protection against intravenous L. mon-
ocytogenes challenge in mice by CRX-526 and ether analog 5. BALB/c mice received
AGPs in 100 lL of 0.2% aq TEOA by iv administration 2 days prior to iv challenge
This work was supported in part by the National Institute of
Allergy and Infectious Diseases (NIAID) under contract HHSN
26620040008C/N01-AI-40008. Any opinions, findings and conclu-
sions or recommendations expressed in this letter are those of
the authors and do not necessarily reflect the views of NIAID.
with 105 L. monocytogenes; CFUs were determined 2 days later by serial dilutions of
splenic homogenates. log10 relative protection was calculated by subtracting CFUs/
spleen (log10 value) in test group from CFUs/spleen (log10 value) in control group.
References and notes
5000
4000
3000
2000
1000
0
1. Ulevitch, R. J. Nat. Rev. Immunol. 2004, 4, 512.
2. Jiang, Z.-H.; Koganty, R . R. Curr. Med. Chem. 2003, 10, 1423.
3. Hawkins, L. D.; Christ, W. J.; Rossignol, D. P. Curr. Top. Med. Chem. 2004, 4, 1147.
4. Johnson, A. G. Clin. Microbiol. Rev. 1994, 7, 277.
5. See, for example: (a) Tamai, R.; Asai, Y.; Hashimoto, M.; Fukase, K.; Kusumoto, S.;
Ishida, H.; Kiso, M.; Ogawa, T. Immunology 2003, 110, 66; (b) Hawkins, L. D.;
Ishizaka, S. T.; McGuinness, P.; Zhang, H.; Gavin, W.; DeCosta, B.; Meng, Z.; Yang,
H.; Mullarkey, M.; Young, D. W.; Yang, H.; Rossignol, D. P.; Nault, A.; Rose, J.;
Przetak, M.; Chow, J. C.; Gusovsky, F. J. Pharmacol. Exp. Ther. 2002, 300, 655; (c)
Jiang, Z.-H.; Budzynski, W. A.;Skeels, L. N.;Krantz, M. J.; Koganty, R. R. Tetrahedron
2002, 58, 8833.
6. Johnson, D. A.; Keegan, D. S.; Sowell, C. G.; Livesay, M. T.; Johnson, C. L.; Taubner, L.
M.; Harris, A.; Myers, K. R.; Thompson, J. D.; Gustafson, G. L.; Rhodes, M. J.; Ulrich,
J. T.; Ward, J. R.; Yorgensen, Y. M.; Cantrell, J. L.; Brookshire, V. G. J. Med. Chem.
1999, 42, 4640.
7. Johnson, D. A.; Sowell, C. G.; Johnson, C. L.; Livesay, M. T.; Keegan, D. S.; Rhodes,
M. J.; Ulrich, J. T.; Ward, J. R.; Cantrell, J. L.; Brookshire, V. G. Bioorg. Med. Chem.
Lett. 1999, 9, 2273.
PBS Vehicle 0.1 ug 1 ug
2
10 ug 0.1 ug 1 ug
5
10 ug
8. Seydel, U.; Labischinski, H.; Kastowsky, M.; Brandenburg, K. Immunobiology
1993, 187, 191.
9. Gioannini, T. L.; Teghanemt, A.; Zhang, D.; Coussens, N. P.; Dockstader, W.;
Ramaswamy, S.; Weiss, J. P. Proc. Natl. Acad. Sci. U.S.A. 2004, 101, 4186.
10. Ohto, U.; Fukase, K.; Miyake, K.; Satow, Y. Science 2007, 316, 1632.
Figure 5. TLR4 agonist activity of CRX-527 (2) and 5 in mice. BALB/c mice (n = 3)
were administered (iv) various amounts of AGP in 0.2% TEOA and serum TNF-
a was
measured by ELISA 1.5 h post-injection.

5354
H. G. Bazin et al. / Bioorg. Med. Chem. Lett. 18 (2008) 5350–5354
11. Kim, H. M.; Park, B. S.; Kim, J.-I.; Kim, S. E.; Lee, J.; Oh, S. C.; Enkhbayar, P.;
Matsushima, N.; Lee, H.; Yoo, O. J.; Lee, J.-O. Cell 2007, 130, 906.
12. Cluff, C. W.; Baldridge, J. R.; Stöver, A. G.; Evans, J. T.; Johnson, D. A.; Lacy, M. J.;
Clawson, V. G.; Yorgensen, Y. M.; Johnson, C. L.; Livesay, M. T.; Hershberg, R. M.;
Persing, D. H. Infect. Immun. 2005, 73, 3044.
13. Stöver, A. G.; Correia, J. D. S.; Evans, J. T.; Cluff, C. W.; Elliott, M. W.; Jeffery, E.
W.; Johnson, D. A.; Lacy, M. J.; Baldridge, J. R.; Probst, P.; Ulevitch, R. J.; Persing,
D. H.; Hershberg, R. M. J. Biol. Chem. 2004, 279, 4440.
ꢁ4.5. To a solution of 7 (500 mg) in MeCN (1.2 mL) at 0 °C was added Et3SiH
(0.17 mL) followed by BiBr3 (100 mg). The resulting black suspension was
treated with hexanal (0.13 mL) and allowed to stir for 10 min. Additional
Et3SiH (0.03 mL), BiBr3 (10 mg) and hexanal (0.03 mL) were then added
sequentially and the mixture was stirred for 10 min, filtered, and concentrated.
Flash chromatography on silica gel afforded 0.39 gm (82%) of 9 as a colorless
oil: 1H NMR (CDCl3, 400 MHz) d 7.78 (d, J = 8.8 Hz, 2H), 7.63 (d, J = 8.8 Hz, 2H),
5.32 (d, J = 16.4 Hz, 1H), 5.25 (d, J = 16.4 Hz, 1H), 3.76 (m, 1H), 3.46 (m, 2H),
2.72 (dd, J = 15.2, 7.2 Hz, 1H), 2.59 (dd, J = 15.2, 5.6 Hz, 1H), 1.50–1.60 (m, 4H),
1.26–1.29 (m, 24H), 0.88 (m, 6H); 13C NMR (CDCl3, 100 MHz) d 191.5, 171.5,
133.2, 132.4, 129.5, 129.3, 76.3, 69.8, 66.0, 39.8, 34.7, 32.2, 31.9, 30.3, 29.9,
29.9, 29.8, 29.6, 26.1, 25.5, 22.9, 22.9, 14.4, 14.3. A solution of 9 (945 mg) in a
mixture of THF (45 mL) and 1 M aq LiOH (9 mL) was stirred at room
temperature for 1 h. Aqueous workup (EtOAc–10% aq HCl) gave an oily
yellow solid which was triturated with hexanes and purified by flash
chromatography to provide 590 mg (quant) of 11 as a colorless oil: 1H NMR
(CDCl3, 400 MHz) d 11.2 (br, 1H), 3.69 (m, 1H), 3.48 (t, J = 6.4 Hz, 2H), 2.53 (m,
2H), 1.5–1.6 (m, 4H), 1.25–1.29 (m, 24H), 0.88 (t, J = 6.8 Hz, 6H); 13C NMR
(CDCl3, 100 MHz) d 176.7, 76.3, 69.8, 54.9, 39.6, 34.3, 32.2, 32.1, 31.8, 30.1,
29.9, 29.9, 29.8, 29.6, 29.3, 26.0, 25.4, 22.9, 22.8, 14.4, 14.3; negative ES TOF-MS
calcd for [MꢁH]ꢁ 327.2899, found 327.2892.
14. Teghanemt, A.; Zhang, D.; Levis, E. N.; Weiss, J. P.; Gioannini, T. L. J. Immunol.
2005, 175, 4669.
15. Fort, M. M.; Mozaffarian, A.; Stöver, A. G.; da Silva Correia, J.; Johnson, D. A.;
Crane, R. T.; Ulevitch, R. J.; Persing, D. H.; Bielefeldt-Ohmann, H.; Probst, P.;
Jeffery, E.; Fling, S. P.; Hershberg, R. M. J. Immunol. 2005, 174, 6416.
16. Baldridge, J. R.; McGowan, P.; Evans, J. T.; Cluff, C.; Mossman, S.; Johnson, D.;
Persing, D. Expert Opin. Biol. Ther. 2004, 4, 1129.
17. Cario, E.; Podolsky, D. K. Infect. Immun. 2000, 68, 7010.
18. Erwin, A. L.; Munford, R. S. J. Biol. Chem. 1990, 265, 16444.
19. Christ, W. J.; Asano, O.; Robidoux, A. L. C.; Perez, M.; Wang, Y.; Dubuc, G. R.;
Gavin, W. E.; Hawkins, L. D.; McGuinness, P. D.; Mullarkey, M. A.; Lewis, M. D.;
Kishi, Y.; Kawata, T.; Bristol, J. R.; Rose, J. R.; Rossingnol, D. P.; Kobayashi, S.;
Hishinuma, I.; Kimura, A.; Asakawa, N.; Katayama, K.; Yamatsu, I. Science 1995,
268, 80.
20. Boullanger, P.; Jouineau, M.; Bouammali, B.; Lafont, D.; Descotes, G. Carbohydr.
Res. 1990, 202, 151.
21. Miyajima, K.; Nekado, T.; Ikeda, K.; Achiwa, K. Chem. Pharm. Bull. 1998, 46,
1676.
22. Christ, W. J.; Hawkins, L. D.; Kawata, T.; Rossignol, D. P.; Kobayashi, S.; Asano,
O. US Patent 5530,113.
23. Jiang, Z. H.; Bach, M. V.; Budzynski, W. A.; Krantz, M. J.; Koganty, R. R.;
Longenecker, B. M. Bioorg. Med. Chem. Lett. 2002, 12, 2193.
24. Watanabe, Y.; Miura, K.; Shiozaki, M.; Kanai, S.; Kurakata, S.; Nishijima, M.
Carbohydr. Res. 2001, 332, 257.
25. Komatsu, N.; Ishida, J.; Suzuki, H. Tetrahedron Lett. 1997, 38, 7219.
26. (a) Bajwa, J. S.; Jiang, X.; Slade, J.; Prasad, K.; Repicˆ, O.; Blacklock, T. J.
Tetrahedron Lett. 2002, 43, 6709; (b) Bajwa, J.; Prasad, K.; Repicˆ, O. Org. Synth.
2006, 83, 155.
29. Spectral data for compounds 4 and 5. Compound 4: 1H NMR (CDCl3, 400 MHz) d
7.08 (d, J = 6.8 Hz, 1H), 6.80 (br, 1H), 5.25(t, J = 10.0 Hz, 1H), 4.67 (m, 1H), 4.49 (m,
1H), 4.30 (q, J = 9.6 Hz, 1H), 4.22 (d, J = 10.4 Hz, 1H), 4.00 (m, 1H), 3.85 (m, 1H),
3.71–3.64 (m, 2H), 3.55–3.42 (m, 2H), 3.39–3.29 (m, 2H), 3.06 (q, J = 7.2 Hz, 6H),
2.67 (dd, J = 15.6, 5.6 Hz, 1H), 2.48–2.41 (m, 2H), 2.36 (dd, J = 14.8, 4.8 Hz, 1H),
2.29–2.17 (m, 2H), 1.52–1.42 (m, 12H), 1.37 (t, J = 7.2 Hz, 9H), 1.25–1.20 (m,
96H), 0.84 (t, J = 6.8 Hz, 12H); 13C NMR (CDCl3, 100 MHz) d 171.9, 171.7, 101.8,
77.5, 76.4, 69.6, 60.6, 53.8, 52.2, 46.7, 46.1, 41.4, 39.2, 34.5, 32.2, 32.2, 30.4, 30.2,
30.2, 30.1, 30.1, 30.0, 30.0, 30.0, 30.0, 29.9, 29.9, 29.9, 29.9, 29.8, 29.8, 29.7, 29.7,
29.7, 29.6, 29.6, 26.5, 26.3, 25.8, 25.7, 25.5, 25.4,14.4, 8.9; negative ES TOF-MS
calcd for [MꢁH]ꢁ 1444.1193, found 1444.1152.Compound 5: 1H NMR (CDCl3,
400 MHz) d 6.95 (d, J = 9.6 Hz, 1H), 6.67 (d, J = 9.6 Hz, 1H), 5.29 (m, 1H), 4.69 (m,
1H), 4.38–4.26 (m, 2H), 4.16 (m, 1H), 3.96 (dd, J = 12.2, 5.2 Hz, 1H), 3.79 (m, 2H),
3.67 (m, 2H), 3.50 (m, 4H), 3.40–3.29 (m, 4H), 3.06 (q, J = 7.2 Hz, 6H), 2.85 (m, 1H),
2.51–2.44 (m, 3H), 2.36 (dd, J = 14.4, 6.0 Hz, 1H), 2.14 (m, 2H), 1.54–1.47 (m,
12H), 1.35–1.19 (m, 81H), 0.89–0.86 (m, 12H); 13C NMR (CDCl3, 100 MHz) d
171.4, 171.2, 77.5, 76.7, 70.0, 69.7, 60.5, 53.4, 46.2, 43.3, 41.7, 39.2, 35.8, 34.7,
32.2, 32.2, 32.2, 32.0, 32.0, 31.9, 30.5, 30.2, 30.2, 30.1, 30.1, 30.0, 30.0, 30.0, 29.9,
29.9, 29.7, 29.7, 29.6, 26.2, 26.2, 26.0, 25.8, 22.9, 22.9, 14.4, 14.3, 8.9, 0.2. negative
ES TOF-MS calcd for [MꢁH]ꢁ 1275.9315, found 1275.9253.
27. Bazin, H. G.; Bess, L. S.; Livesay, M. T.; Ryter, K. T.; Johnson, C. L.; Arnold, J. S.;
Johnson, D. A. Tetrahedron Lett. 2006, 47, 2087.
28. General procedure for the preparation of ether acid 11: A solution of 6 (15.0 g) in
CH2Cl2 (150 mL) was treated with TBDMS-Cl (10.8 g), imidazole (4.86 g), and
DMAP (415 mg) and allowed to stir at room temperature for 24 h. Aqueous
workup followed by flash chromatography on silica gel afforded 18.6 g (98%) of
7 as an oil: 1H NMR (CDCl3, 400 MHz) d 7.78 (d, J = 8.8 Hz, 2H), 7.63 (d,
J = 8.8 Hz, 2H), 5.30 (d, J = 16.4 Hz, 1H), 5.25 (d, J = 16.4 Hz, 1H), 4.18 (m, 1H),
2.63 (d, J = 6.4 Hz), 1.52 (m, 2H), 1.26 (m, 18H), 0.87 (m, 12H), 0.07 (s, 3H), 0.05
(s, 3H); 13C NMR (CDCl3, 100 MHz) d 191.5, 171.4, 133.2, 132.4, 129.5, 129.4,
69.5, 65.9, 42.5, 37.7, 32.2, 29.9, 29.8, 29.6, 26.0, 25.2, 22.9, 18.2, 14.4, ꢁ4.3,
30. Shimazu, R.; Akashi, S.; Ogata, H.; Nagai, Y.; Fukudome, K.; Miyake, K.; Kimoto,
M. J. Exp. Med. 1999, 189, 1777.
31. Akashi, S.; Nagai, Y.; Ogata, H.; Oikawa, M.; Fukase, K.; Kusumoto, S.; Kawasaki,
K.; Nishijima, M.; Hayashi, S.; Kimoto, M.; Miyake, K. Int. Immunol. 2001, 13,
1595.
32. Muroi, M.; Tanamoto, K. J. Biol. Chem. 2006, 281, 5484.