Phenothiazine-based CaaX competitive inhibitors of human farnesyltransferase bearing a cysteine, methionine, serine or valine moiety as a new family of antitumoral compounds

Article abstract of DOI:10.1016/j.bmcl.2015.09.008

A new family of CaaX competitive inhibitors of human farnesyltransferase based on phenothiazine and carbazole skeleton bearing a l-cysteine, l-methionine, l-serine or l-valine moiety was designed, synthesized and biologically evaluated. Phenothiazine derivatives proved to be more active than carbazole-based compounds. Phenothiazine 1b with cysteine residue was the most promising inhibitor of human farnesyltransferase in the current study.

Full text of DOI:10.1016/j.bmcl.2015.09.008

Bioorganic & Medicinal Chemistry Letters 25 (2015) 4447–4452
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Phenothiazine-based CaaX competitive inhibitors of human
farnesyltransferase bearing a cysteine, methionine, serine or valine
moiety as a new family of antitumoral compounds
Gina-Mirabela Dumitriu a, Elena Bîcu a, Dalila Belei a, Benoît Rigo b,c, Joëlle Dubois d, Amaury Farce b,e
,
Alina Ghinet a,b,c,
⇑
a Department of Organic Chemistry, Faculty of Chemistry, ‘Al. I. Cuza’ University of Iasi, B-dul Carol I, Nr. 11, Corp A, 700506 Iasi, Romania
b Inserm, LIRIC-U995, Université de Lille 2, CHRU de Lille, Faculté de Médecine—Pôle Recherche, Place Verdun, F-59045 Lille Cedex, France
c Hautes Etudes d’Ingénieur (HEI), UCLille, Laboratoire de pharmacochimie, 13 rue de Toul, BP 41290, F-59014 Lille Cedex, France
d Institut de Chimie des Substances Naturelles, UPR2301 CNRS, Centre de Recherche de Gif, Avenue de la Terrasse, F-91198 Gif-sur-Yvette Cedex, France
e Université de Lille 2, Faculté des Sciences Pharmaceutiques et Biologiques, Laboratoire de Chimie Thérapeutique, 3 rue du Professeur Laguesse, BP 83, F-59006 Lille Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 July 2015
Revised 3 September 2015
Accepted 4 September 2015
Available online 7 September 2015
A new family of CaaX competitive inhibitors of human farnesyltransferase based on phenothiazine and
carbazole skeleton bearing a L-cysteine, L-methionine, L-serine or L-valine moiety was designed, synthe-
sized and biologically evaluated. Phenothiazine derivatives proved to be more active than carbazole-
based compounds. Phenothiazine 1b with cysteine residue was the most promising inhibitor of human
farnesyltransferase in the current study.
Ó 2015 Elsevier Ltd. All rights reserved.
Keywords:
Farnesyltransferase
Phenothiazine
Cysteine
Methionine
Serine
Valine
CAAX inhibitor
The interest in protein farnesyltransferase (FTase) as a potential
cancer target is maintained in recent years.1–6 FTase is a heterodi-
meric zinc metalloenzyme, responsible for posttranslational mod-
ification and activation of Ras proteins. Ras proteins undergo three
sequential enzymatic posttranslational modifications. The first
step of isoprenylation is catalyzed by FTase and consists of a cova-
lent attachment of the farnesyl group of farnesyldiphosphate (FPP)
on the cysteine residue from the C-terminus of tetrapeptidic
(CaaX) sequence of Ras proteins.7 In the CaaX motif, the letter C
represents a cysteine and the letter a denotes an aliphatic amino
acid. FTase recognizes proteins carrying in X a serine, methionine,
glutamine or alanine.8,9 The isoprenylation process plays a key role
in the signaling pathway that allows cell division. Thus, preventing
the farnesylation process by inhibiting FTase can represent an
approach in cancer chemotherapy.
will thus compete with the terminal cysteine of Ras proteins
(replacement of aliphatic amino acids by aromatic amino acids
and modification of the methylation reaction of the C-terminus).
Cell permeability problems have been reported in the past for
some CaaX competitive FTIs, due to their peptide structure,10 sen-
sitive to peptidases (e.g., compound VII, CVIM, Fig. 1). For this rea-
son, currently developed FTIs are nonpeptide. These compounds
are often capable of chelating the zinc cation of FTase and have a
methionine as X residue6,11 (e.g., compound VIII,11 Fig. 1).
Based on our previous efforts in identifying new FTIs (com-
pounds I–VI, Fig. 1)2,12–15 and in order to enrich the existing SAR
on this family of antitumoral agents, we were then interested in
the design and synthesis of CaaX competitive inhibitors of FTase
with phenothiazine or carbazole skeleton bearing a cysteine,
methionine, serine or valine residue as potential zinc chelating unit
(compounds 1a–i and 2a–i, Fig. 1).
The main part of molecules targeting FTase are competitive
inhibitors of CaaX box. CaaX competitive inhibitors of FTase (FTIs)
The title compounds 1a–i, 2a–i were synthesized as outlined in
Scheme 1. Starting acids 6–8 were obtained by Michael addition
reaction of carbazole 12, phenothiazine 13 or 2-chlorophenoth-
iazine 14 with acrylonitrile in the presence of Triton B,16,17
⇑
Corresponding author.
E-mail address: alina.ghinet@hei.fr (A. Ghinet).
http://dx.doi.org/10.1016/j.bmcl.2015.09.008
0960-894X/Ó 2015 Elsevier Ltd. All rights reserved.

4448
G.-M. Dumitriu et al. / Bioorg. Med. Chem. Lett. 25 (2015) 4447–4452
O
H
O
N
N
O
N
II
O
O
SH
O
N
N
O
OH
N
N
N
S
Br
I
O
N
O
O
IC50 (human FTase) = 18.0 µM12
IC50 (human FTase) = 35 µM2
N
O
S
S
III
IV
IC50 (human FTase) = 0.6 µM15
N
IC50 (human FTase) = 1.3 µM13
HO
H3C
N
N
O
N
O
NH
O
N
N
N
S
S
V
VI
IC50 (human FTase) = 4.7 µM15
IC50 (human FTase) = 3.7 µM14
Farnesylpyrophosphate (FPP) chain
O
CO2H
HS
O
O
H
O
N
H
S
N
H2N
N
H
OH
N
N
H
S
O
O
S
S
VIII
IC50 (human FTase) = 0.4 µM11
VII (CVIM)
H
N
H
N
H
N
H
N
COOR1
COOR1
COOR1
CH2OH
COOR1
CH2SH
O
O
O
O
CH(CH3)2
CH2CH2SCH3
N
A
N
A
N
A
N
A
1a-i, 2a-i
cysteine derivatives
methionine derivatives
serine derivatives
valine derivatives
A = bond, S
R
1 = Me, Et, H
Target compounds
Figure 1. Structure of FTase inhibitors discovered in previous research work (compounds I–VIII) and of target compounds (1a–i, 2a–i).
followed by hydrolysis of nitrile 9–11 with aqueous sodium
hydroxide in methanol.16,17 The key intermediates, activated esters
3, 4,2,13 5, were then prepared by reaction between carboxylic acids
6, 7 and 8 with N-hydroxysuccinimide in the presence of EDCI [1-
ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride].18
Furthermore, coupling reactions of activated esters 3 and 4 with
target triazole derivative 20 (Scheme 3), phenothiazine 13 was first
reacted with 1-bromo-3-chloropropane using sodium hydride as
base and provided chloro derivative 15.19 Azide 16 was next
obtained in good yield by action of sodium azide in water/chloro-
form in the presence of TBAB phase-transfer catalysis medium at
room temperature.20 The construction of 1,2,3-triazole ring in
compound 17 was then achieved by click chemistry.21,22 The
saponification of ethyl ester 17 straightforwardly provided car-
boxylic acid 18 which was further coupled, after in situ activation
L-cysteinyl, methionyl, serinyl or valinyl esters provided the corre-
sponding esters 2a–h (Scheme 1). In these reactions, the target cys-
teinyl ester derivative 2b bearing a phenothiazine unit was
obtained in 53% yield by reacting N-hydroxysuccinimide activated
in the presence of 1-hydroxybenzotriazole and EDCI, with L-me-
ester 7 with
L
-cysteine ethyl ester hydrochloride, but the dimer 2bd
thionine methyl ester hydrochloride to obtain intermediate 19 in
69% yield. Synthesis of the target triazole derivative 20 was finally
achieved in very good yield by simple saponification of methyl
ester 19 (Scheme 3).
was also isolated in 43% yield (Scheme 2). Finally, the saponifica-
tion of esters 2a–h furnished carboxylic derivatives 1a–h
(Scheme 1). In the 2-chlorophenothiazine series, only the coupling
reaction of activated ester 5 with
L
-methionine methyl ester
The activity of all synthesized phenothiazine and carbazole
derivatives was evaluated on human FTase.23 Results are reported
in Table 1 and Figures 2 and 3. Examination of the inhibitory profile
of these two series emphasizes, without exception, greater biolog-
ical potential for derivatives bearing a phenothiazine unit (e.g.,
hydrochloride was realized in order to obtain the corresponding
ester 2i, which was then saponified to the corresponding acid 1i
(Scheme 1).
In the interest of exploring the importance on the biological
efficiency of three carbon atoms chain between the phenothiazinic
nitrogen atom and the methionyl residue, the introduction of a tri-
azolyl unit as a different tensor was then envisaged. To reach the
phenothiazine 1b (IC50 (FTase) = 4.7 0.5
(IC50 (FTase) = 65.4 5.1 M); phenothiazine 1d (IC50 (FTase)
= 11.7 0.9 M) vs carbazole 1c (IC50 (FTase) = 40.2 2.2 M),
lM) vs carbazole 1a
l
l
l

G.-M. Dumitriu et al. / Bioorg. Med. Chem. Lett. 25 (2015) 4447–4452
4449
N
C
COOH
H
N
X
X
N
A
X
N
(i)
(ii)
A
A
Lit. 17
A = bond, X = H
6
7
8
Lit. 17
9
A = bond, X = H
12 A = bond, X = H
13 A = S, X = H
14 A = S, X = Cl
A = S, X = H Lit. 16
Lit. 16
10 A = S, X = H
A = S, X = Cl
(iii)
Lit. 16
11 A = S, X = Cl Lit. 16
O
H
H
O
N
COOR1
O
O
O
N
COOH
N
R
R
O
X
N
A
X
N
A
X
N
A
(iv)
(v)
2a A = bond, X = H, R = CH2SH, R1 = Et 85%
2b A = S, X = H, R = CH2SH, R1 = Et 53%
Lit. 2
A = bond, X = H
3
4
5
1a A = bond, X = H, R = CH2SH 70%
1b A = S, X = H, R = CH2SH 90%
A = S, X = H Lit. 13
A = S, X = Cl 69%
2c A = bond, X = H, R = CH2CH2SCH3, R1 = Me 75%
2d A = S, X = H, R = CH2CH2SCH3, R1 = Me 91%
2e A = bond, X = H, R = CH2OH, R1 = Me 79%
2f A = S, X = H, R = CH2OH, R1 = Me 99%
1c A = bond, X = H, R = CH2CH2SCH3 84%
1d A = S, X = H, R = CH2CH2SCH3 85%
1e A = bond, X = H, R = CH2OH 78%
1f A = S, X = H, R = CH2OH 75%
1g A = bond, X = H, R = CH(CH3)2 92%
1h A = S, X = H, R = CH(CH3)2 80%
1i A = S, X = Cl, R = CH2CH2SCH3 82%
2g A = bond, X = H, R = CH(CH3)2, R1 = Me 80%
2h A = S, X = H, R = CH(CH3)2, R1 = Me 89%
2i A = S, X = Cl, R = CH2CH2SCH3, R1 = Me 97%
Scheme 1. Reagents and conditions: (i) acrylonitrile, Triton B, 0 °C to reflux, 2 h; (ii) aqueous NaOH, MeOH, reflux, 15 h; (iii) 1.2 equiv N-hydroxysuccinimide, 1.2 equiv EDCI,
CH2Cl2, rt, 24 h; (iv) 1.2 equiv -cysteine ethyl ester hydrochloride, -methionine methyl ester hydrochloride, -serine methyl ester hydrochloride or -valine methyl ester
L
L
L
L
hydrochloride, 1.2 equiv triethylamine, CH2Cl2, rt, 24 h; (v) 5 equiv NaOH 2 N, 80 °C, 2–5 h.
O
H
N
H
COOEt
O
O
N
O
O
N
COOEt
SH
N
S
N
S
S
COOEt
HN
O
N
S
N
S
(iv)
O
S
4
2b
2bd 43%
Scheme 2. Reagents and conditions: (iv) 1.2 equiv L-cysteine ethyl ester hydrochloride, 1.2 equiv triethylamine, CH2Cl2, rt, 24 h.
Table 1). This result is in accordance with previous reported studies
which highlight the phenothiazine nucleus as well tolerated bulky
unit for the A2 binding site of human farnesyltransferase.12,13,15
The 2-chloro substitution of the phenothiazine unit is tolerated,
but does not improve the activity. Thus, methionine compound
1i has similar FTase affinity as unsubstituted derivative 1d (e.g.,
was thus realized (Scheme 3 and Fig. 3). Since the 2-chloro substi-
tution of the phenothiazine unit in compound 1i did not result in
improved inhibitory properties (Fig. 3), the spacer variation was
realized only on compound 1d. However, the insertion of the tria-
zole unit in compound 20 and consequently, the increase of the
spacer length, was not tolerated and resulted in diminished biolog-
ical potency (e.g., compound 1d vs 20, Fig. 3). The three-carbon
atoms chain between the phenothiazine nitrogen and the amino
group from the aminoacid residue proved to be important for the
FTase inhibition.
compound 1i: IC50 (FTase) = 18.9 3.2
lM vs compound 1d: IC50
(FTase) = 11.7 0.9 M, Table 1). Therefore, this chemical modula-
l
tion was not envisaged in the cysteine, serine or valine series.
Moreover, carboxylic acids 1a–i showed superior inhibitory
potency compared to their ester analogues 2a–i (Table 1 and
Fig. 2). This highlights a better chelating power of the zinc cation
of the enzyme for carboxylic acids versus ethyl or methyl esters.
Similar tendency was previously observed in the FTase inhibitors
domain.12
The study of the nature of the aminoacid residue on the biolog-
ical properties revealed that in the carbazole series, the cysteine
and methionine analogues (e.g., carbazoles 1a and 1c, Table 1)
were more active than derivatives bearing a serine or a valine unit
(e.g., carbazoles 1e and 1g, Table 1). In the phenothiazine series,
cysteine derivative 1b was the best FTase inhibitor. Methionine
and serine analogues (compounds 1c and 1f, respectively) showed
slightly decreased activities and valine derivative 1h presented a
Farnesyltransferase structure24 was taken from the 1LD7 entry
of the RCSB Protein Data Bank.25 The crystallized inhibitor and
water molecules were removed to permit docking of the studied
compounds, built from the standard fragments library of Sybyl
6.9.126 with GOLD 5.1.27 Thirty solutions were generated and
classed through an in-house scoring function based on GoldScore27
and X-Score functions.28 The consistency of the results was
assessed by visually examining the conformation cluster.
Molecular docking was realized on the best candidates issued
from this study 1b, 1d, 1f and 1i (Fig. 4) in order to validate the
zinc-chelating potential of the free carboxylic acids and under-
stand the positioning and interactions of these molecules in the
active site of FTase.
modest activity (IC50 (FTase) = 44.7
l
M) (Table 1).
Phenothiazine derivative bearing a cysteine moiety 1b (Fig. 4
(a)) has a set of conformations placed on the same side and ori-
ented in the same direction in the active site of the protein and
with a score superior to serine derivative 1f. The carboxylic acid
is in a favorable position and interacts with the zinc atom of the
protein, a fact significant for FTase inhibitory properties.
In order to gain supplementary structure–activity relationships
in the current family of CaaX competitive inhibitors of human far-
nesyltransferase, modulations have been envisaged on the spacer
between the nitrogen atom from the phenothiazine unit and the
amide function. The insertion of a 1,2,3-triazole ring as a spacer

4450
G.-M. Dumitriu et al. / Bioorg. Med. Chem. Lett. 25 (2015) 4447–4452
Cl
N3
H
N
N
N
S
(i)
(ii)
S
S
16 80%
Lit. 19
13
15
(iii)
N
N
O
N
N
N
O
N
N
N
N
S
S
COOR
HN
HN
COOH
(iv)
COOMe
(v)
N
S
N
S
N
S
17 R = Et 65%
(iv)
20 80%
19 69%
18 R = H 90%
Scheme 3. Reagents and conditions: (i) 1.2 equiv 1-bromo-3-chloropropane, 1.2 equiv NaH, dimethylformamide;19 (ii) 3 equiv sodium azide, 0.45 equiv tetrabutylammo-
niumbromide (TBAB), CHCl3/H2O 2:1, rt, 24 h; (iii) 1 equiv ethyl propiolate, 0.1 equiv CuSO4Á5H2O, 0.2 equiv sodium ascorbate, t-BuOH/H2O 10:2, rt, 24 h; (iv) 5 equiv NaOH
2 N, 80 °C, 2 h; (v) 1 equiv L-methionine methyl ester hydrochloride, 1.05 equiv 1-hydroxybenzotriazole, 1 equiv EDCI, 1 equiv triethylamine, CH2Cl2, rt, 24 h.
Table 1
Inhibitory activities of compounds 1a–i, 2a–i, 2bd on human FTase
H
N
COOR1
O
R
X
N
A
b
Compound
A
R
R1
X
% Inh (FTase)a,b
IC50
(l
M
SDc)
R2d
1a
1b
1c
1d
1e
1f
1g
1h
1i
Bond
S
Bond
S
Bond
S
Bond
S
CH2SH
CH2SH
CH2CH2SCH3
CH2CH2SCH3
CH2OH
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Cl
H
H
67
92
73
92
33
94
22
76
96
15
10
65.4 5.1
4.7 0.5
40.2 2.2
11.7 0.9
n.d.e
12.0 2.6
n.d.
44.7 3.5
18.9 3.2
n.d.
0.923
0.964
0.759
0.959
—
0.845
—
0.938
0.947
—
CH2OH
CH(CH3)2
CH(CH3)2
CH2CH2SCH3
CH2SH
S
2a
2b
Bond
S
CH2CH3
CH2CH3
CH2SH
n.d.
—
CH2S
2bd
S
CH2CH3
H
0
n.d.
—
2
2c
2d
2e
2f
2g
2h
2i
Bond
S
Bond
S
Bond
S
S
CH2CH2SCH3
CH2CH2SCH3
CH2OH
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
H
H
H
H
H
Cl
51
5
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
—
—
—
—
—
—
—
23
63
12
52
0
CH2OH
CH(CH3)2
CH(CH3)2
CH2CH2SCH3
a
b
c
Inhibition ratio of protein farnesyltransferase at a 100
Values represent mean of two experiments.
SD: standard deviation.
lM concentration.
d
e
R2: regression factor.
Not determined.
The methionine derivative 1d (Fig. 4(b)) occupies globally the
oriented. The conformation with the best score is represented in
Figure 4(d). The tricycle location is not stable, adopting at least
three different positions in the active site.
same place in the active site as compound 1b. Again, carboxylic
acid function is placed next to the zinc cation to insure complexa-
tion and thus, inactivation of the enzyme.
Serine derivative 1f has two possible conformations. One con-
formation seems significantly larger and is depicted in Figure 4
(c). The carboxylic acid interacts with the zinc atom of
farnesyltransferase. The tricycle lodges globally the same place as
derivatives 1b and 1d, explaining the similar biological activity.
2-Chlorophenothiazine derivative 1i is the least active of these
four compounds. It can adopt four different conformations suitably
The comparison of the various compounds seems to indicate a
two point interaction mode. The first and most evident is the interac-
tion with the zinc atom of the enzyme, which is chelated by at least
the acid moiety of all the molecules. Small substituents on the neigh-
boring branch of the side chain are able to form a second interaction,
which may count for a part of the activity of compounds 1b and 1f.
The ethyl linker in the side chain of the amino acid is too long to per-
mit a correct placement of the terminal sulfur of 1d and 1i.

G.-M. Dumitriu et al. / Bioorg. Med. Chem. Lett. 25 (2015) 4447–4452
4451
activity. In fact, none of the compounds with a bond in position A
appears in the best compounds. Interestingly, the difference
between 1b and 1f is the presence of a second conformation for
the last, with the tricycle off to the side of the pocket, along the
FPP. This may explain the diminished activity of compound 1f
compared to compound 1b. This conclusion is further proved by
compound 1i. Substitution at R1 hinders rather seriously the posi-
tioning of the tricycle and therefore has a degrading effect on the
stability of the best interaction conformation of the tricycle, with
compound 1i having three possible placements in the binding site.
A new series of phenothiazine and carbazole derivatives bearing
a
L-cysteine,
L-methionine, L-serine or L-valine moiety was
designed, synthesized and evaluated as human farnesyltransferase
inhibitors. The preferred synthetic strategy appealed primarily to
an activated ester coupling reaction with esters of the four differ-
ent aminoacids mentioned above and provided target esters 2a–i
and 19 in very good yields. A final straightforward saponification
reaction provided corresponding carboxylic acids 1a–i and 20. A
biological screening was assessed on all final compounds in order
to evaluate the ability to inhibit human farnesyltransferase.
Phenothiazine derivative bearing a cysteine residue 1b was the
Figure 2. Comparative inhibitory activity on human FTase in the carbazole and
phenothiazine series at a 100 M concentration: esters 2a–h (in green) versus
corresponding acids 1a–h (in red).
l
The second is less apparent when looking only at the docking
results but is evident when checking the biological results. The
tricyclic base of the compound has a privileged position for a high
N
O
N
N
H
N
H
COOH
COOH
O
N
COOH
S
O
N
N
HN
Spacer variation:
Tricycle functionalization by
2-chlorophenothiazinyl
replacement
insertion of a
1,2,3-triazole ring
S
N
S
Cl
S
S
S
20
1d
1i
Figure 3. Inhibitory activity of 1,2,3-triazole-4-methionine derivative 20 on human FTase compared to phenothiazines 1d and 1i.
(a) 1b
(b) 1d
FPP
Zn
Tyr 361β
Trp 106β
Leu 196β
Tyr 166α
Cys 195β
Trp 102β
(c) 1f
Arg 202β
(d) 1i
Figure 4. Docking of compounds 1b, 1d, 1f and 1i in the active site of FTase: (a) compound 1b, (b) compound 1d, (c) compound 1f, (d) compound 1i.

4452
G.-M. Dumitriu et al. / Bioorg. Med. Chem. Lett. 25 (2015) 4447–4452
5. Moorthy, N. S. H. N.; Sousa, S. F.; Ramos, M. J.; Fernandes, P. A. Curr. Med. Chem.
2013, 20, 4888.
6. Straniero, V.; Pallavicini, M.; Chiodini, G.; Ruggeri, P.; Fumagalli, L.; Bolchi, C.;
Corsini, A.; Ferri, N.; Ricci, C.; Valoti, E. Bioorg. Med. Chem. Lett. 2014, 24, 2924.
7. Russo, P.; Loprevite, M.; Cesario, A.; Ardizzoni, A. Curr. Med. Chem. Anticancer
Agents 2004, 4, 123.
8. Zhang, F. L.; Casey, P. J. Annu. Rev. Biochem. 1996, 65, 241.
9. Zhang, H. In Handbook of Metalloproteins; Messerschmidt, Albrecht, Ed.; John
Wiley & Sons Ltd: Chichester, UK, 2004; Vol. 3, p 37.
10. Kral, A. M.; Diekl, R. E.; deSolms, S. J.; Williams, T. M.; Kohl, N. E.; Omer, C. A. J.
Biol. Chem. 1997, 272, 27319.
11. Bolchia, C.; Pallavicinia, M.; Berninib, S. K.; Chiodinia, G.; Corsinib, A.; Ferrib,
N.; Fumagallia, L.; Straniero, V.; Valoti, E. Bioorg. Med. Chem. Lett. 2011, 21,
5408.
12. Dumitriu, G. M.; Ghinet, A.; Bîcu, E.; Rigo, B.; Dubois, J.; Farce, A.; Belei, D.
Bioorg. Med. Chem. Lett. 2014, 24, 3180.
13. Belei, D.; Dumea, C.; Samson, A.; Farce, A.; Dubois, J.; Bîcu, E.; Ghinet, A. Bioorg.
Med. Chem. Lett. 2012, 22, 4517.
14. Baciu-Atudosie, L.; Ghinet, A.; Farce, A.; Dubois, J.; Belei, D.; Bîcu, E. Bioorg. Med.
Chem. Lett. 2012, 22, 6896.
most interesting inhibitor of human farnesyltransferase in the cur-
rent study with an IC50 value in the micromolar domain. Some
important QSAR have been established on the basis of the develop-
ment and biological evaluation of this new family of CaaX compet-
itive inhibitors of human farnesyltransferase: (1) the
phenothiazine skeleton has great importance for the biological
activity on human FTase; the replacement by a carbazole unit
resulted in diminished inhibitory potential; (2) the substitution
of the phenothiazine unit in position 2 by a chloro group is toler-
ated and consequently conserves the biological properties; (3) car-
boxylic acid derivatives 1a–i are more active in vitro than
corresponding esters 2a–i, thus suggesting a greater zinc chelating
potential for the free carboxylic group compared to an ester moi-
ety; (4) cysteine derivatives have slightly improved inhibitory
properties compared to methionine and serine analogues; the vali-
nyl-substituted compounds presenting the most modest activity in
the current study; (5) finally, the spacer length between the phe-
nothiazinic nitrogen and the amide group is also important for
the affinity toward FTase; the insertion of a triazole ring, and thus
increase of the spacer length, diminishes the biological potency on
the protein.
15. Abuhaie, C.-M.; Ghinet, A.; Farce, A.; Dubois, J.; Gautret, P.; Rigo, B.; Belei, D.;
Bîcu, E. Eur. J. Med. Chem. 2013, 59, 101.
16. Godefroi, E. F.; Wittle, E. L. J. Org. Chem. 1956, 21, 1163.
17. Tierney, M. T.; Grinstaff, M. W. Org. Lett. 2000, 2, 3413.
18. Nakajima, S.; Ikada, Y. Bioconjugate Chem. 1995, 6, 123.
19. Harrold, M. W.; Chang, Y. A.; Wallace, R. A.; Farooqui, T.; Wallace, L. J.; Uretsky,
N.; Miller, D. D. J. Med. Chem. 1987, 30, 1631.
20. Belei, D.; Bicu, E.; Jones, P. G.; Birsa, M. L. J. Heterocycl. Chem. 2011, 48, 129.
21. Rostovtsev, V.; Green, L.; Fokin, V.; Sharpless, B. Angew. Chem., Int. Ed. 2002, 41,
2596.
The best candidates issued from this study could constitute
strategic hits for developing anticancer agents with improved
characteristics.
22. Li, Z.; Seo, T.; Ju, J. Tetrahedron Lett. 2004, 45, 3143.
23. Farnesyltransferase assay: Assays were carried out in 96-well plates, prepared
with a Biomek NKMC and a Biomek 3000 from Beckman Coulter and read on a
Acknowledgements
Wallac Victor fluorimeter from Perkin–Elmer. per well, 20
farnesylpyrophosphate (10 M) was added to 180 L of a solution containing
L of varied concentrations of potential inhibitors (dissolved in DMSO) and
178 L of a solution composed by 10 L of partially purified recombinant
human FTase (1.5 mg/mL) and 1.0 mL of dansyl-GCVLS peptide (in the
following buffer: 5.6 mM DTT, 5.6 mM MgCl2, 12 M ZnCl2 and 0.2% (w/v)
octyl-b- -glucopyranoside, 52 mM Tris/HCl, pH 7.5). Fluorescence
development was recorded for 15 min (0.7 s per well, 20 repeats) at 30 °C
with an excitation filter to 340 nm and an emission filter of 486 nm. Each
measurement was realized twice, in duplicate or in triplicate. The kinetic
experiments were realized under the same conditions, either with FPP as
l
L
of
l
l
2
l
This work was supported by the strategic grant POS-
DRU/159/1.5/S/137750, Project ‘‘Doctoral and Postdoctoral pro-
grams support for increased competitiveness in Exact Sciences
research” cofinanced by the European Social Found within the Sec-
torial Operational Program Human Resources Development 2007–
2013 (PhD scholarship G.-M.D.).
l
l
l
D
varied substrate with a constant concentration of Dns-GCVLS of 2.5
with Dns-GCVLS as varied substrate with a constant concentration of FPP of
10 M. Nonlinear regressions were performed by KaleidaGraph 4.03 software.
lM, or
Supplementary data
l
Coudray, L.; de Figueiredo, R. M.; Duez, S.; Cortial, S.; Dubois, J. J. Enzyme Inhib.
Med. Chem. 2009, 24, 972.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2015.09.
008.
24. Bell, I. M.; Gallicchio, S. N.; Abrams, M.; Beese, L. S.; Beshore, D. C.;
Bhimnathwala, H.; Bogusky, M. J.; Buser, C. A.; Culberson, J. C.; Davide, J.;
Ellis-Hutchings, M.; Fernandes, C.; Gibbs, J. B.; Graham, S. L.; Hamilton, K. A.;
Hartman, G. D.; Heimbrook, D. C.; Homnick, C. F.; Huber, H. E.; Huff, J. R.;
Kassahun, K.; Koblan, K. S.; Kohl, N. E.; Lobell, R. B.; Lynch, J. J., Jr.; Robinson, R.;
Rodrigues, A. D.; Taylor, J. S.; Walsh, E. S.; Williams, T. M.; Zartman, C. B. J. Med.
Chem. 2002, 45, 2388.
25. Berman, H. M.; Westbrook, J.; Feng, Z.; Gary, G.; Bhat, T. N.; Weissig, H.;
Shindyalov, I. N.; Bourne, P. E. Nucleic Acids Res. 2000, 28, 235.
26. SYBYL 6.9.1, Tripos Associates, 1699 South Hanley Road, St. Louis, MO 63144.
27. Jones, G.; Willett, P.; Glen, R. C.; Leach, A. R.; Taylor, R. J. Mol. Biol. 1997, 267,
727.
References and notes
1. Yang, L.; Liu, W.; Mei, H.; Zhang, Y.; Yu, X.; Xu, Y.; Li, H.; Huang, J.; Zhao, Z.
MedChemComm 2015, 6, 671.
2. Dumitriu, G.-M.; Ghinet, A.; Belei, D.; Rigo, B.; Gautret, P.; Dubois, J.; Bîcu, E.
Lett. Drug Des. Discovery 2015, 12, 85.
3. Shen, M.; Pan, P.; Li, Y.; Li, D.; Yu, H.; Hou, T. Drug Discovery Today 2015, 20, 267.
4. Holland, A. J.; Cleveland, D. W.; Desai, A.; Reis, R. M.; Pereira, C.; Gassmann, R.;
Niessen, S.; Andres, D. A.; Spielmann, H. P. Mol. Biol. Cell 1845, 2015, 26.
28. Wang, R.; Lai, L.; Wang, S. J. Comput. Aided Mol. Des. 2002, 16, 11.