Synthesis and biological evaluation of N-mercaptoacylcysteine derivatives as leukotriene A4 hydrolase inhibitors

Article abstract of DOI:10.1016/j.bmcl.2008.11.042

We studied synthetic modifications of N-mercaptoacylamino acid derivatives to develop a new class of leukotriene A₄ (LTA₄) hydrolase inhibitors. S-(4-Dimethylamino)benzyl-l-cysteine derivative 2a (SA6541) showed inhibitory activity against LTA₄ hydrolase (IC₅₀, 270 nM) and selectivity over other metallopeptidases except angiotensin-converting enzyme (ACE, IC₅₀, 520 nM). Modification at the para-substituent of the phenyl ring of compound 2a improved LTA₄ hydrolase inhibitory activity as well as selectivity over ACE. Finally, we obtained S-(4-cyclohexyl)benzy-l-cysteine derivatives 11l and 16i as potent and selective LTA₄ hydrolase inhibitors.

Full text of DOI:10.1016/j.bmcl.2008.11.042

Bioorganic & Medicinal Chemistry Letters 19 (2009) 442–446
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and biological evaluation of N-mercaptoacylcysteine derivatives
as leukotriene A4 hydrolase inhibitors
*
Hiroshi Enomoto , Yuko Morikawa, Yurika Miyake, Fumio Tsuji, Maki Mizuchi, Hiroshi Suhara,
Ken-ichi Fujimura, Masato Horiuchi, Masakazu Ban
Nara Research & Development Center, Santen Pharmaceutical Co., Ltd, 8916-16 Takayama-cho, Ikoma-shi, Nara 630-0101, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
We studied synthetic modifications of N-mercaptoacylamino acid derivatives to develop a new class of
Received 6 October 2008
Revised 10 November 2008
Accepted 13 November 2008
Available online 18 November 2008
leukotriene A4 (LTA4) hydrolase inhibitors. S-(4-Dimethylamino)benzyl-L-cysteine derivative 2a
(SA6541) showed inhibitory activity against LTA4 hydrolase (IC50, 270 nM) and selectivity over other
metallopeptidases except angiotensin-converting enzyme (ACE, IC50, 520 nM). Modification at the
para-substituent of the phenyl ring of compound 2a improved LTA4 hydrolase inhibitory activity as well
as selectivity over ACE. Finally, we obtained S-(4-cyclohexyl)benzy-L-cysteine derivatives 11l and 16i as
potent and selective LTA4 hydrolase inhibitors.
Keywords:
LTA4 hydrolase
LTA4 hydrolase inhibitor
Epoxide hydrolase
N-Mercaptoacylcysteine
Ó 2008 Elsevier Ltd. All rights reserved.
Leukotriene A4 (LTA4) hydrolase (EC 3.3.2.6) is a bifunctional
zinc-containing metalloenzyme.1 One of its functions is a highly
substrate-specific epoxide hydrolase activity, which involves con-
verting an unstable epoxide fatty acid derivative LTA4 into a diol
leukotriene B4 (LTB4), a potent proinflammatory mediator.2 This
catalytic reaction is the final and rate-determining step in LTB4 bio-
synthesis. Therefore, inhibition of LTA4 hydrolase would be a suit-
able approach for treatment of a variety of inflammatory diseases.3
Another function is its intrinsic arginyl aminopeptidase activity.
The biological role of which has not been elucidated thus far.1
Previously, we reported that 4-arylalkylthio-N-[(2S)-3-mer-
selectivity over other metallopeptidases, it still retained the ACE8
inhibitory activity (Table 1). Therefore, we synthesized a new
series of N-mercaptoacylamino acid derivatives to develop more
potent and more selective LTA4 hydrolase inhibitors than
compound 2a.
Compound 2a and all the compounds listed in Table 2–5 were
synthesized as below. Synthesis of 2a was conducted as shown
in Scheme 1.7a 4-Dimethylaminobenzyl alcohol 3 was treated with
R
capto-2-methylpropionyl]-L-proline derivatives had inhibitory
S
activities against LTA4 hydrolase. Compounds 1a and 1b, in partic-
ular, exhibited more potent and selective inhibitory activities
against the enzyme than its lead compound, captopril (Fig. 1).4 This
result prompted us to obtain more selective LTA4 hydrolase inhib-
itors. On the basis of a previous study4 and structural similarities to
the zinc-containing metalloenzyme, we had screened other ACE
inhibitors, N-mercaptoacylamino acid derivatives,5 for inhibitory
activities against LTA4 hydrolase.4,6,7a Among the derivatives, we
HS
N
O
HS
N
O
O
O
OH
OH
Captopril
-R =
LTA4H IC50; 31 nM
ACE IC50; 410 nM
LTA4H IC50; 630000 nM
ACE IC50 ; 23 nM
1a
LTA4H IC50; 34 nM
ACE IC50 ; 280 nM
found that S-(4-dimethylamino)benzyl-L-cysteine derivative 2a
O
H
(SA6541, Fig. 1) possessed the desired inhibitory activity7a (Table
1).
1b
HS
N
OH
O
Compound 2a exhibited good anti-inflammatory effects after
S
oral administration in murine.7 Although the compound showed
2a (SA6541)
LTA H IC ; 270 nM
N
4
50
* Corresponding author. Tel.: +81 743 79 4527; fax: +81 743 79 4608.
E-mail address: hiroshi.enomoto@santen.co.jp (H. Enomoto).
Figure 1. Structures of 4-arylalkylthio-N-[(2S)-3-mercapto-2-methylpropionyl]-
proline derivatives and compound 2a (SA6541).
L-
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.11.042

H. Enomoto et al. / Bioorg. Med. Chem. Lett. 19 (2009) 442–446
443
Table 1
Inhibitory activities of compound 2a against other metallopeptidases
Table 3
R2 modifications of S-(4-dimethylamino)benzyl-L-cysteine
Enzyme
Compound 2a
O
H
N
R2
OH
IC50 or % inhibition at 100 lM
LTA4 hydrolase
Angiotensin-converting enzyme
Aminopeptidase M
Endopeptidase 24.11
Endothelin-1 converting enzyme
Type I collagenase
0.27
0.52
42%
16%
8%
l
l
M
M
S
N
3%
Compound
R2–
IC50 (nM)
Type III collagenase
No inhibition
LTA4 hydrolase
Table 2
HS
R1 modifications of N-[(2S)-3-mercapto-2-methylpropionyl]amino acid
7a
7b
470
O
O
H
HS
N
OH
>10,000
O
R1
HS
O
O
2
Compound
–R1
IC50 (nM)
LTA4 hydrolase
7c
>10,000
>10,000
270
HS
HS
7d
S
2a (SA6541)
270
O
N
HS
2a (SA6541)
O
2b
2c
>10,000
>10,000
S
HS
HS
7e
7f
1500
O
O
N
N
S
S
7400
HS
7g
>10,000
2d
2e
>10,000
>10,000
O
prepared from N-Boc-
D
-cysteine and N-Boc-
L
-homocysteine, respec-
tively. Introduction of the R2 moieties of compounds 7a–g was
accomplished by using corresponding active esters derived from
S-benzoylthioalkanoic acids9 instead of 4-nitrophenyl (2S)-3-ben-
zoylthio-2-methylpropionate in Scheme 1.
N
S
Syntheses of compounds 11a–p and 11r–u in Table 4 were
treated as shown in Scheme 2. Appropriate 4-substituted benzyl
chlorides and bromides (8a–p and 8r–u) were combined with
hydrobromic acid, followed by the reaction of resultant bromide 4
with N-Boc- -cysteine to give N-Boc-S-(4-dimethylamino)benzyl-
-cysteine 5. After removing the N-Boc group of compound 5,
L
L
-cysteine in the presence of aqueous sodium hydroxide to yield
L
S-(4-substituted)benzyl-
L
-cysteine derivatives 9a–p and 9r–u.10
coupling reactions with 4-nitrophenyl (2S)-3-benzoylthio-2-meth-
The resultant compounds were then coupled with 4-nitrophenyl
(2S)-3-benzoylthio-2-methylpropionate to yield N-[(2S)-3-ben-
ylpropionate4 gave N-[(2S)-3-benzoylthio-2-methylpropionyl]-S-
(4-dimethylamino)benzyl-
6 gave S-(4-dimethylamino)benzy-N-[(2S)-3-mercapto-2-methyl-
propionyl]- -cysteine 2a.
Compounds 2b–e (Table 2), 7a–g (Table 3), and 11q (Table 4) were
prepared in a similar way as compound 2a. Compound 2b was
L
-cysteine 6. Ammonolysis of compound
zoylthio-2-methylpropionyl]-S-(4-substituted)benzyl-L-cysteine
derivatives (10a–p and 10r–u). Reaction of compounds 10a–p
and 10r–u with aqueous ammonia gave compounds 11a–p and
11r–u. Compound 12 (Table 5) was synthesized in a similar
L
way by using
Scheme 3 represents the synthesis of compounds 16a–i (Table
5). Corresponding alcohols 13a–i together with -cysteine were
L-penicillamine instead of L-cysteine.
obtained via coupling reaction of S-benzyl-
phenyl (2S)-3-benzoylthio-2-methylpropionate to give N-[(2S)-3-
benzoylthio-2-methylpropionyl]-S-benzyl- -cysteine followed by
L-cysteine with 4-nitro-
L
L
treated with hydrochloric acid at 55–65 °C followed by N-Boc pro-
deprotection with aqueous ammonia yielding the desired com-
pound. Synthesis of compounds 2c and 11q was conducted with
3-dimethylaminobenzyl alcohol and 4-diethylaminobenzyl alcohol
as starting materials, respectively. Compounds 2d and 2e were
tection for isolation and purification by flash chromatography,
yielding N-Boc-S-substituted-L-cysteine derivatives 14a–i. After
removing the N-Boc groups of 14a–i, coupling reactions
with 4-nitrophenyl (2S)-3-benzoylthio-2-methylpropionate gave

444
H. Enomoto et al. / Bioorg. Med. Chem. Lett. 19 (2009) 442–446
Table 4
R3 modifications of S-benzyl-N-[(2S)-3-mercapto-2-methylpropionyl]-L-cysteine
N
. HBr
O
S
N
H
N
O
a
c, d
b
OH
O
H
O
HS
N
OH
5
OH
N
O
Br
S
3
4
O
S
O
S
H
N
R3
H
N
e
HS
N
S
OH
OH
O
Compound
R3
IC50 (nM)
O
O
LTA4 hydrolase
ACE
34
6
2a (SA6541)
N
2b
H
F
Cl
Br
>10,000
>10,000
1700
610
15
7200
140
280
72
200
24
600
79
2400
400
640
1700
270
900
530
4900
46
11a
11b
11c
11d
11e
11f
11g
11h
11i
11j
11k
11l
11m
11n
11o
11p
2a (SA6541)
11q
11r
100
250
280
140
240
340
21
210
300
130
280
4000
100
260
340
370
520
4600
300
320
300
300
Scheme 1. Reagents and conditions: (a) 47% HBr aq 120 °C, 2.5 h; (b) Boc-
L
-Cys-OH,
N,N-diisopropylethylamine, CH2Cl2, rt, 2.5 h; (c) 4 M HCl in dioxane, rt, 1 h; (d) 4-
nitrophenyl (2S)-3-benzoylthio-2-methylpropionate, triethylamine, DMF, CH2Cl2,
rt, overnight; (e) 28% NH3 aq, rt, 1 h.
I
CH3
CF3
C2H5
n-Pr
i-Pr
t-Bu
Ph
c-Hex
OCH3
OCF3
OC2H5
OPh
N(CH3)2
N(C2H5)2
CN
NO2
SCH3
SO2CH3
R3
O
H2N
a
b
OH
S
R3
X
9a-p, 9r-u
X = Cl, Br
8a-p, 8r-u
O
S
O
H
c
H
HS
N
11s
11t
11u
S
N
OH
OH
O
O
O
160
S
11a-p, 11r-u
R3
10a-p, 10r-u
R3
Table 5
R3, R4, R5, R6, and R7 modifications of S-benzyl-N-[(2S)-3-mercapto-2-methylpropi-
Scheme 2. Reagents and conditions: (a)
L
-Cysteine HClÁH2O, 2 M NaOH aq, EtOH,
onyl]-L-cysteine
CHCl3, rt, overnight; (b) 4-nitrophenyl (2S)-3-benzoylthio-2-methylpropionate,
triethylamine, DMF, rt, overnight; (c) 28% NH3 aq, rt, 1 h.
O
H
HS
N
R4
R5
OH
R3
O
H
O
S
R6
O
N
OH
a, b
c, d
R7
O
R3
S
R6
R6
OH
R7
13a-i
R7
Compound
R3
R4
H
R5
H
CH3
H
H
H
H
H
R6
R7
IC50 (nM)
R3
14a-i
LTA4 hydrolase
ACE
O
11i
12
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
H
H
H
H
H
H
H
H
H
H
200
>10,000
55
300
>10,000
200
340
420
O
H
e
H
CH3
HS
N
S
N
OH
OH
16a
16b
16c
16d
16e
16f
16g
11l
16h
16i
H
H
H
H
H
H
H
H
H
H
CH3
C2H5
n-Pr
i-Pr
n-Bu
Ph
CH3
H
Ph
O
O
O
67
S
S
R6
R6
180
520
510
91
79
79
430
16a-i
R7
15a-i
R7
R3
R3
3600
1700
260
4000
>10,000
3000
H
H
H
H
i-Pr
CH3
H
H
Scheme 3. Reagents and conditions: (a)
L
-Cysteine HClÁH2O, 2 M HCl aq, dioxane,
c-Hex
c-Hex
c-Hex
55–65 °C, overnight; (b) (Boc)2O, triethylamine, THF, rt, 4 h; (c) 4 M HCl in dioxane,
rt, 1 h; (d) 4-nitrophenyl (2S)-3-benzoylthio-2-methylpropionate, triethylamine,
DMF, rt; (e) 28% NH3 aq, rt, 1 h.
210
55
H
CH3
CH3
N-[(2S)-3-benzoylthio-2-methylpropionyl]-S-(a-substituted-4-sub-
compound 2a or the desdimethylamino analog (2b) did not show
stituted)benzyl- -cysteine derivatives 15a–i. A reaction of com-
L
the inhibitory activity. Neither did the derivative of L-homocyste-
pounds 15a–i with aqueous ammonia resulted in compounds 16a–i.
Table 2 shows the effect of R1 moiety of N-[(2S)-3-mercapto-2-
methylpropionyl]amino acid derivatives. S-(4-dimethylamino)-
ine (2e) (IC50 > 10,000 nM).
We then studied alterations in the N-mercaptoacyl moiety of the
compound 2a (Table 3). Introduction of the mercaptoacetyl group
(7a) slightly reduced the inhibitory activity. Neither the 2-merca-
ptopropionyl group (7b and 7c) nor the 3-mercaptopropionyl group
benzyl-L-cysteine derivative 2a (SA6541) exhibited LTA4 hydrolase
inhibitory activity. However, a regioisomer (2c), the epimer (2d) of

H. Enomoto et al. / Bioorg. Med. Chem. Lett. 19 (2009) 442–446
445
(7d) were efficacious for raising LTA4 hydrolase inhibitory activity
(IC50 > 10,000 nM). Compound 7e, the epimer of 2a, decreased the
activity. The 3-mercaptobutyryl group (7f) markedly reduced LTA4
hydrolase inhibitory activity, and the 4-mercaptobutyryl group
(7g) decreased it even further (IC50 > 10,000 nM). These results
suggest that the steric requirements of the enzyme surrounding
the acyl moiety is highly stringent—much like those of N-mercap-
(1H6S.pdb). Every compound bound to Arg563 by its carboxyl
group, to Gly268 and Gly269 by its amide carbonyl O and to Zn2+
by its sulfhydryl S. Substituted benzyl portion elongated toward
Phe340 and occupied a similar location within the pose a of com-
pounds 1a and 1b4 (Fig. 2). Another pose, whose substituted benzyl
part heading Arg568 was comparable to pose b of compounds 1a
and 1b,4 was found for those except for compound 11l. In gem-di-
methyl analogs, while active compounds (16g and 16i) docked in
a- and b-like poses, inactive compound 12 did so only in b-like pose.
This fact suggests that the binding of the active compounds occur in
pose a. A docking study of compounds 2b and 11g into ACE
(1UZF.pdb) gave analogous poses to a but not b in LTA4 hydrolase.
We also observed this pattern for the proline type inhibitor 1a in
its docking into ACE. Although estimation of binding free energies
of compound 11j calculated by MM/GBSA16 did not give a clear pref-
erence between the two poses, five different runs indicated that
pose a was more likely than b, and this tendency was also displayed
by compound 1a. Consequently, as a binding pose (active conforma-
tion) of compound 11j as well as compound 1a, pose a is plausible.
The groove of LTA4 hydrolase around the cyclohexylbenzylthio
group of compound 11l in pose a was wide spread and comprised
several amino acid residues (Asn291, Val322, Arg326, Glu348,
Ser380, Glu384, and Lys565). However, the counterpart of ACE
around compound 2b consisting of residues (Thr282, Val379,
Val380, Asp415, Asp453, Lys454, and Phe527) was narrow and lim-
ited. Particularly, Glu376 extends its side chain to obscure the
space. Table 4 displays these results. LTA4 hydrolase inhibitory
activity increased with increasing bulkiness of R3 from compound
2b (R3 = H) to compound 11j (R3 = t-Bu). Interaction between R3
and the surrounding amino acid residues will be essential to ex-
press activity since compound 2b had no activity. On the other
hand, potent ACE inhibition was observed in compounds 2b and
11g, both with small R3. The inhibitory activity appeared to gradu-
ally decrease with increasing bulkiness of R3 and abruptly de-
creased in 11l and 11q. A large symmetrical substituent with
respect to the bonding axis of R3 in compounds 11l and 11q may
not be able to circumvent the Glu376 side chain to effectively bind
to ACE. For the non-active compound (12) with a gem-dimethyl
group at b-position, Lys565 may hamper binding to LTA4 hydrolase
in addition to yielding an unfavorable conformational energy.
When R7 was large, the substituent would bump against His383
and Phe457 in ACE to reduce the inhibitory activity.
toacyl-
acid derivatives which we previously reported.4
Since the S-benzyl- -cysteine derivative 2b and the S-(3-
dimethylamino)benzyl- -cysteine derivative 2c did not show
L-proline and (4R)-N-mercaptoacylthiazolidine-4-carboxylic
L
L
inhibitory activities against LTA4 hydrolase (Table 2), we made ef-
forts only to introduce para-substituents (Table 4). Introduction of
the fluorine atom (11a) did not appear to improve activity against
LTA4 hydrolase. An iodine atom (11d) created the most potent LTA4
hydrolase inhibition in this series. Introduction of the methyl
group (11e) contributed to only weak inhibitory activity against
the enzyme and trifluoromethyl (11f), ethyl (11g), isopropyl
(11i), and phenyl (11k) groups raised the activity moderately.
Introduction of n-propyl (11h), tert-butyl (11j), and cyclohexyl
(11l) groups improved the activities further. Notably, compound
11l showed potent LTA4 hydrolase inhibitory activity (IC50
;
79 nM) with a small inhibition against ACE (IC50, 4000 nM). Intro-
duction of alkoxy and phenoxy groups (11m–p), diethylamino
(11q), cyano (11r), and nitro (11s) groups showed weak or moder-
ate inhibitory activities against LTA4 hydrolase. Adoption of the
methylthio group made the compound (11t) potent; however,
the methanesulfonyl group (11u) did not. Quantitative structure–
activity relationship (QSAR) analysis by multi-regression analysis
of compounds 11b–u suggested a quadratic relation with mr (mo-
lar refractivity) of R3. The optimum value for inhibition was
mropt = 10.36, which corresponded to 11j (R3 = t-Bu).11
To examine the effects of substituents at b- and d-positions on
the S-benzyl-L-cysteine moiety, we modified these portions of
compound 11i. Though introduction of the gem-dimethyl group
at the b-position (compound 12, Table 5) resulted in loss of activity
(IC50 > 10,000 nM), the same group at the d-position improved the
inhibitory activity against LTA4 hydrolase (compound 16g, Table
5). Comparison of conformational energies (D
E)12 among com-
pounds 11i, 12 and 16g taking the active conformation (pose a),
which will be discussed later, suggested that compound 12 had
approximately 2–4 kcal/mol higher energy than the other two, a
possible reason why compound 12 lost its inhibitory activity.
Therefore, we focused on the modification at the benzyl (d-methy-
In conclusion, we studied synthetic modifications of the lead
compound 2a to develop potent and selective LTA4 hydrolase
inhibitors. Modification at the para-substituent of the phenyl ring
of compound 2a improved LTA4 hydrolase inhibitory activity and
made the iodo derivative 11d the most potent (IC50, 15 nM). An-
other modification at this position also improved selectivity for
lene) position (R6 and R7, Table 5) of the S-benzyl-
L-cysteine deriv-
atives. Table 5 outlines these results. For those compounds with
R3 = i-Pr, compounds 16a (R6 = H and R7 = CH3), 16b (R6 = H and
R7 = C2H5), 16f (R6 = H and R7 = Ph), and 16g (R6 and R7 = CH3)
showed higher LTA4 hydrolase inhibitory activities compared with
that of compound 11i (R6 and R7 = H). Among them, compound 16f
inhibited LTA4 hydrolase with nineteen times more potency than
ACE. LTA4 hydrolase inhibitory activities of compounds 16d
(R6 = H, R7 = i-Pr) and 16e (R6 = H and R7 = n-Bu) decreased a little.
When R3 was a cyclohexyl, ACE inhibitory activity of compound
16h (R6 = H and R7 = Ph) markedly decreased, however, maintain-
ing LTA4 hydrolase inhibitory activity. A similar trend was also
found for 11l (R6 and R7 = H) and 16i (R6 and R7 = CH3) compounds.
Structures of LTA4 hydrolase analyzed by X-ray crystallography
have been reported in which most ligands lie along the binding site
of LTA4 with a binding to catalytic Zn2+ 13,14
.
Captopril, a weak LTA4
hydrolase inhibitor, is also known to bind by its terminal S to Zn2+
.
Previously, we described possible binding poses in the enzyme of
mercaptoacylproline derivatives 1a, 1b, and captopril as a refer-
ence.4 Their pyrrolidinyl and the mercaptoacyl parts were located
over each other. In a similar way, docking poses within GOLD15 of
several potent compounds (11d, 11j, 11l, and 11t) were examined
Figure 2. Plausible poses (pose a) of compounds 1a (purple) and 11l (cyan) docked
into LTA4 hydrolase.

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H. Enomoto et al. / Bioorg. Med. Chem. Lett. 19 (2009) 442–446
6. Ohishi, N.; Izumi, T.; Minami, M.; Kitamura, S.; Seyama, Y.; Ohkawa, S.; Terao,
S.; Yotsumoto, H.; Takaku, F.; Shimizu, T. J. Biol. Chem. 1987, 262, 10200. LTA4
hydrolase was purified from guinea pig lung and subjected to the enzyme assay
according to Ref. 6. IC50 values were calculated by linear regression analysis of
at least three independent dose–response titration of each compound in
duplicate.
LTA4 hydrolase versus ACE. In particular, compounds 11l and 16i
containing cyclohexyl group exhibited potent LTA4 hydrolase
inhibitory activities (IC50, 79 and 55 nM, respectively) with a small
inhibition of ACE (IC50, 4000 and 3000 nM, respectively).
7. (a) Tsuji, F.; Miyake, Y.; Horiuchi, M.; Mita, S. Biochem. Pharmacol. 1998, 55,
297; (b) Tsuji, F.; Miyake, Y.; Enomoto, H.; Horiuchi, M.; Mita, S. Eur. J.
Pharmacol. 1998, 346, 81; (c) Tsuji, F.; Oki, K.; Fujisawa, K.; Okahara, A.;
Horiuchi, M.; Mita, S. Life Sci. 1999, 64, PL51.
8. Horiuchi, M.; Fujimura, K.; Terashima, T.; Iso, T. J. Chromatogr. 1982, 233, 123.
ACE activity was measured according to the method of Ref. 8.
9. Oya, M.; Baba, T.; Kato, E.; Kawashima, Y.; Watanabe, T. Chem. Pharm. Bull.
1982, 30, 440.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2008.11.042.
References and notes
10. Frankel, M.; Gertner, D.; Jacobson, H.; Zilkha, A. J. Chem. Soc. 1960, 1390.
11. QSAR analysis is discussed in Supplementary data.
12. Conformational analysis (e = 80) was done within MMFF94 to reach at 100
1. Haeggström, J. Z. J. Biol. Chem. 2004, 279, 50639.
consecutive failures of stochastic search process with MOE (Chemical
Computing Group Inc., 1010 Sherbrooke Street West, Suite 910, Montreal,
Quebec, Canada).
2. Ford-Hutchinson, A. W.; Bray, M. A.; Doig, M. V.; Shipley, M. E.; Smith, M. J. H.
Nature 1980, 286, 264.
3. (a) Klickstein, L. B.; Shapleigh, C.; Goetzl, E. J. J. Clin. Invest. 1980, 66, 1166; (b)
Iversen, L.; Kragballe, K.; Ziboh, V. A. Skin Pharmacol. 1997, 10, 169; (c) Sharon,
P.; Stenson, W. F. Gastroenterology 1984, 86, 453; (d) Rae, S. A.; Davidson, E. M.;
Smith, M. J. H. Lancet 1982, 11, 1122; (e) Bigby, T. D.; Lee, D. M.; Meslier, N.;
Gruenert, D. C. Biochem. Biophys. Res. Commun. 1989, 164, 1.
13. Thunnissen, M. M. G. M.; Nordlund, P.; Haeggström, J. Z. Nat. Struct. Biol. 2001,
8, 131.
14. Thunnissen, M. M. G. M.; Andersson, B.; Samuelsson, B.; Wong, C.-H.;
Haeggström, J. Z. FASEB J. 2002, 16, 1648.
15. GOLD (Version 3.1), Jones, G.; Willett P.; Glen, R. C. J. Mol. Biol. 1995, 245, 43.
16. CHARMm scripts of MM/GBSA calculation was obtained from Accelrys Inc
(Accelrys Inc., 10188 Telesis Court, Suite 100, San Diego, CA, USA). Molecular
dynamics simulation of 1 ns for protein–ligand complex, protein and ligand
with 25 Å water cap or sphere (atoms 16 Å away fixed) around the ligand were
performed.
4. Enomoto, H.; Morikawa, Y.; Miyake, Y.; Tsuji, F.; Mizuchi, M.; Suhara, H.;
Fujimura, K.; Horiuchi, M.; Ban, M. Bioorg. Med. Chem. Lett. 2008, 18, 4529.
5. (a) Oya, M.; Matsumoto, J.; Takashina, H.; Iwao, J.; Funae, Y. Chem. Pharm. Bull.
1981, 29, 63; (b) Oya, M.; Matsumoto, J.; Takashina, H.; Watanabe, T.; Iwao, J.
Chem. Pharm. Bull. 1981, 29, 940; (c) Oya, M.; Kato, E.; Matsumoto, J.;
Kawashima, Y.; Iwao, J. Chem. Pharm. Bull. 1981, 29, 1203.