Hydantoin derivatives as non-peptidic inhibitors of Ras farnesyl transferase

Article abstract of DOI:10.1016/j.bmcl.2005.12.074

1,3,5,5-Tetrasubstituted 2,4-imidazolinedione (hydantoin) derivatives were evaluated as Ftase inhibitors. Potent Ftase inhibitors without thiol or peptide were obtained in three steps.

Full text of DOI:10.1016/j.bmcl.2005.12.074

Bioorganic & Medicinal Chemistry Letters 16 (2006) 1954–1956
Hydantoin derivatives as non-peptidic inhibitors of Ras
farnesyl transferase
Jinho Lee,a,* Jonghyun Kim,b Jong Sung Koh,b Hyun-Ho Chungb and Kyoung-Hee Kimb
aDepartment of Chemistry, Keimyung University, 1000 Sindang-Dong, Dalseo-Gu, Daegu 704-701, Republic of Korea
bLG Life Sciences, Science Town, Taejon 305-380, Republic of Korea
Received 15 September 2005; revised 8 December 2005; accepted 21 December 2005
Available online 25 January 2006
Abstract—1,3,5,5-Tetrasubstituted 2,4-imidazolinedione (hydantoin) derivatives were evaluated as Ftase inhibitors. Potent Ftase
inhibitors without thiol or peptide were obtained in three steps.
Ó 2006 Elsevier Ltd. All rights reserved.
Ras protein plays an important role in cell growth and
differentiation. Oncogenic Ras has been found in 40%
a
b
O
of human cancers including 90% of pancreatic and
50% of colon carcinomas.1,2 Ras protein needs a series
of post-translational modifications including the farn-
esylation catalyzed by farnesyl transferase (Ftase).3
Inhibitors of Ftase are considered as potential antican-
cer agents.4–6 The observation that Ftase can farnesylate
C-terminal tetrapeptide of Ras (CAAX in which C is
cysteine, A is aliphatic amino acid, and X is serine
or methionine) triggers great efforts to develop
peptidomimetic inhibitors. Substitution of aliphatic
amino acids, AA of CAAX tetrapeptide, with benzodi-
azepine7 3-(aminomethyl)benzoic acid (3-AMBA),8
piperazine,9 and 1,2,3,4-tetrahydroisoquinoline-3-car-
boxylate (Tic)10 had been tried. Conformational analysis
of potent tetrapeptidic inhibitor CVFM (IC50 25 nM)11
renders us to design hydantoin scaffold.
N
N
H
H
O
1
O
O
O
c
R1
R2
N
N
R1
H
N
N
O
O
3
2
Scheme 1. Reagents: (a) KCN, (NH4)2CO3, 90%; (b) R1-OH, DEAD,
Ph3P; (c) NaH, R2-Br.
unobu condition.13 Normal alkylation at the N-1
position provided the desired compound 3.
Hydantoin was synthesized in one step using Sano’s
condition12 in 90% yield (Scheme 1). 5-Methyl-5-(1-
naphthyl)-2,4-imidazolidinedione (hydantoin 1) was ob-
tained as racemic mixtures from the reaction of 10-aceto-
naphthone with potassium cyanide and ammonium
carbonate and it was used without chiral resolution.
Introduction of the substituent at N-3 position was per-
formed with the corresponding alcohol under the Mitz-
Substitution of naphthalene at C-4 position of hydanto-
in improved inhibitory activity about one order of mag-
nitude more than that of phenyl substituent (data not
shown). However, conformational study showed that
naphthalene could accommodate several spatial orienta-
tions relative to the hydantoin ring. Introduction of
methyl group at C-4 position provided the steric restric-
tion which forced the naphthalene to the desired orien-
tation. Also, it removed the easy epimerizing character
of hydantoin structure.
Keywords: Hydantoin; 1,3,5,5-Tetrasubstituted 2,4-imidazolinedione;
Farnesyl transferase; Non-peptidic.
*
As a first step to remove the peptidic character, imidaz-
ole was used at the position of cysteine because it had
Corresponding author. Tel.: +82 53 580 5183; fax: +82 53 580
5164; e-mail: jinho@kmu.ac.kr
0960-894X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.12.074

J. Lee et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1954–1956
1955
been used to replace cysteine for several non-peptidic
small Ftase inhibitors and had been found to interact
with the enzyme-bound Zn ion.10 Introduction of
imidazole with an optimal distance (3 methylene unit)
from hydantoin provided high potency (IC50 0.8 nM,
Table 1).
peptidic character, N-acetylmethionine, of compound 6
had been tried. The variation of N-1 substituent was
performed, while the N-3 position of hydantoin was
fixed with (1H-imidazol-1-yl)propyl group. Among the
hydrophobic substituents, benzyl group provided nM
range inhibitory activity with substituent’s dependency.
Halogens 10a–c were allowed at both meta- and para-
positions, while phenoxy 10d,e was a little bulky to fit
in the enzyme pocket. Cyano group showed that m-po-
sition showed better activity up to 10 times than p-posi-
tion (10g vs 10h). X-ray crystallographic structure
analysis showed that m-cyano group filled the narrow
pocket created by Tyr93, Leu96, Leu103, Asp359,
Phe360, and Tyr361 residues, while the m-carboxyl
group could form H-bond interaction with the Tyr93
residue of the enzyme.16 Cationic substituent at p-posi-
tion was not favored so the protection of amine provid-
ed activity increase by 6 times (10n vs 10o). Sulfide 10k,
10m, sulfone 10l, and sulfonamide 10o–q were tried as
the surrogate of methionine residue, but they did not be-
have as expected. Combination of p-methylsulfide and
m-cyano 10r did not improve the inhibitory activity of
m-cyano 10h (Table 3).
The orientation of imidazole affected the inhibitory
activities of compounds (Table 2). (1H-Imidazol-1-
yl)propyl 9a,b at N-3 position of hydantoin provided
better activity than (1H-imidazol-4-yl)propyl 7a,b or
(1-methyl-1H-imidazol-5-yl)propyl 8 group.15 The bet-
ter potency of (1H-imidazol-1-yl) 9b than (1-methyl-
1H-imidazol-5-yl) 8 suggested that the increment of
basicity was not the only factor of activity gain.
Since the modeling study showed that the naphthalene
at C-4 position of hydantoin overlapped nicely with
the phenyl ring of CVFM, the replacement of remaining
Table 1. The effect of linker between hydantoin and imidazole on the
inhibitory activity of the farnesyl transferasea
Kinetic study showed that hydantoin derivatives were
competitive with Ras protein. X-ray crystal structure
showed that the hydantoin compound binds in the Ras
binding region of enzyme and the nitrogen atom of
imidazole interacts with Zn(II) metal.
S
O
O
N
R
N
n
N
N
N
H
H
O
O
4,5,6
b
IC50 (nM)
Compound
n
R
Table 3. The effect of substituents on the inhibitory activity of the
farnesyl transferase
4a
4b
5a
5b
6a
6b
1
1
2
2
3
3
OCH3
OH
19,000
61
OCH3
OH
2500
4.8
O
OCH3
OH
500
0.8
R1
10a-s
N
N
N
N
a The farnesyl transferase inhibitory assays were performed as descri-
bed in Ref. 14.
R2
O
b Values are means of three experiments.
a
Compound
R1
R2
IC50 (lM)
10a
10b
10c
10d
10e
10f
10g
10h
10i
H
p-Br
m-Br
0.16
0.37
0.24
0.75
0.72
0.2
Table 2. The effect of imidazole on the inhibitory activity of the
farnesyl transferase
H
H
m-Cl
p-OPh
H
H
m-OPh
p-CO2H
p-CN
O
H
H
0.9
R1
N
N
7,8,9
R2
H
m-CN
o-CN
0.09
1.3
H
O
10j
H
m-CF3
p-SCH3
p-SO2CH3
p-CH2SCH3
p-CH2NH2
1.7
0.7
10k
10l
H
H
1.1
Compound R1
R2
IC50
(lM)
a
10m
10n
10o
10p
10q
10r
10s
H
0.21
2.1
H
H
p-CH2NHSO2CH3
m-CH2NHSO2CH3
o-CH2NHSO2CH3
p-SCH3
0.35
1.2
7a
9a
7b
8
1H-Imidazol-4-yl
1H-Imidazol-1-yl
1H-Imidazol-4-yl
H
40
H
H
CH2CO2CH2CH3
7.7
3.8
2.8
1.0
H
0.5
m-CN
m-CN
0.08
0.73
1-Methyl-imidazol-5-yl CH2CO2CH2CH3
1H-Imidazol-1-yl CH2CO2CH2CH3
p-SO2CH3
9b
a Values are means of three experiments.
a Values are means of three experiments.

1956
J. Lee et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1954–1956
10. Hunt, J. T.; Lee, V. G.; Leftheris, K.; Seizinger, B.;
Carboni, J.; Mabus, J.; Ricca, C.; Yan, N.; Manne, V. J.
Med. Chem. 1996, 39, 353.
11. Reiss, Y.; Stradley, S. J.; Gierasch, L. M.; Brown, M. S.;
Goldstein, J. L. Proc. Natl. Acad. Sci. U.S.A. 1991, 88, 732.
12. Sano, H.; Sugai, S. Tetrahedron 1995, 51, 4635.
13. Mitsunobu, O. Synthesis 1981, 1.
In summary, hydantoin was found to be an effective
scaffold that gives rise to a series of potent inhibitors
of farnesyl transferase. Non-peptidic hydantoin deriva-
tives were synthesized in 3 steps and they showed IC50
as low as 80 nM 10r.
14. The assay was done by a modification of the procedure
described by Moores et al. Moores, S. L.; Schaber, M. D.;
Mosser, S. D.; Rands, E.; O’Hara, M. B.; Garsky, V. M.;
Marchall, M. S.; Pompliano, D. L.; Gibbs, J. B. J. Biol.
Chem. 1991, 266, 14603, Briefly, Ras protein (20 lM) was
incubated for 30 min at 37 °C with Ftase enzyme
(16.6 nM), [3H]farnesylpyrophosphate (FPP) (0.3 lM,
20 Ci/mmol, Dupont NEN) and serially diluted test
compounds at a given concentration in the buffer con-
taining 50 mM HEPES, pH 7.4, 250 mM MgCl2, 25 mM
KCl, 0.5% N-octylglucoside, 50 lM ZnCl2, and 10 mM
DTT. The enzyme reactions were then quenched by
adding the solution containing 10% HCl in absolute
ethanol. The [3H]FPP-incorporated Ras was collected by
filter binding (25 mm glass fiber filter, Whatman) and
quantitated by scintillation counter. IC50: the concentra-
tion of compound required to reduce the Ftase-catalyzed
incorporation of [3H]FPP into H-Ras protein by 50%.
15. (a) Synthesis of alcohol derivatives: 3-(1H-imidazol-4-yl)-1-
propanol was obtained by reduction of urocanic acid with
References and notes
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1
LiAlH4 in quantitative yield. H NMR (CDCl3) 1.79 (p,
2H), 2.64 (t, J = 7.3 Hz, 2H), 3.56 (br, 1H), 3.60 (t,
J = 6.1 Hz, 2H), 6.69 (s, 1H), 7.48 (s, 1H).; (b) 3-(1H-
Iimidazol-1-yl)-1-propanol; imidazole 5 g (73.4 mmol) and
methyl acrylate 12.6 g (148.6 mmol) were dissolved in
100 ml of acetonitrile. After refluxing for 8 h, acetonitrile
and unreacted methyl acrylate were removed under reduced
pressure. Ethyl acetate was added to the residue and washed
with saturated NaCl solution. Removal of ethyl acetate
gave methyl 3-(1H-imidazole-1-yl)-1-propionate 11.1 g in
90% yield. Reduction of methyl ester with LiAlH 4 provided
1
´
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desired alcohol in 93% yield. H NMR (CDCl3): 1.97 (p,
2H), 3.57 (t, J = 5.8 Hz, 2H), 4.06 (br, 1H), 4.11 (t,
J = 6.7 Hz, 2H), 6.92 (s, 1H), 7.01 (s, 1H), 7.51 (s, 1H).
16. The coordinate has been deposited in the Protein Data
Bank: PDB ID 2F0Y.
´