Preparation and evaluation of novel pyrazolo[1,5-a]pyrimidine acetamides, closely related to DPA-714, as potent ligands for imaging the TSPO 18 kDa with PET

Article abstract of DOI:10.1016/j.bmcl.2014.01.080

A series of four novel analogues of DPA-714, bearing a fluoroalkynyl side chain (with a length ranging from three to six carbon atoms) in replacement of the fluoroethoxy motif, have been synthetized in six steps from commercially available methyl 4-iodobe

Full text of DOI:10.1016/j.bmcl.2014.01.080

Accepted Manuscript
Preparation and evaluation of novel pyrazolo[1,5-a]pyrimidine acetamides,
closely related to DPA-714, as potent ligands for imaging the TSPO 18 kDa with
PET
Vincent Médran-Navarrete, Annelaure Damont, Marie-Anne Peyronneau,
Bertrand Kuhnast, Nicholas Bernards, Géraldine Pottier, Frank Marguet,
Frédéric Puech, Raphaël Boisgard, Frédéric Dollé
PII:
S0960-894X(14)00120-6
DOI:
http://dx.doi.org/10.1016/j.bmcl.2014.01.080
BMCL 21315
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
29 August 2013
24 January 2014
27 January 2014
Please cite this article as: Médran-Navarrete, V., Damont, A., Peyronneau, M-A., Kuhnast, B., Bernards, N., Pottier,
G., Marguet, F., Puech, F., Boisgard, R., Dollé, F., Preparation and evaluation of novel pyrazolo[1,5-a]pyrimidine
acetamides, closely related to DPA-714, as potent ligands for imaging the TSPO 18 kDa with PET, Bioorganic &
Medicinal Chemistry Letters (2014), doi: http://dx.doi.org/10.1016/j.bmcl.2014.01.080
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Preparation and evaluation of novel pyrazolo[1,5-a]pyrimidine
acetamides, closely related to DPA-714, as potent ligands for
imaging the TSPO 18 kDa with PET
Vincent Médran-Navarrete,a Annelaure Damont,a Marie-Anne Peyronneau,a Bertrand
Kuhnast,a Nicholas Bernards,a,b Géraldine Pottier,a,b Frank Marguet,c Frédéric Puech,c
Raphaël Boisgard,a,b Frédéric Dollé.a
a CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France.
b Inserm, U1023, Université Paris Sud, Orsay, France
c Exploratory Unit, Sanofi, Chilly-Mazarin, France.
ABSTRACT
A series of four novel analogues of DPA-714, bearing a fluoroalkynyl side chain
(with a length ranging from three to six carbon atoms) in replacement of the
fluoroethoxy motif, have been synthetized in six steps from commercially available
methyl 4-iodobenzoate. The synthetic strategy for the preparation of these N,N-diethyl-
2-(2-(4-(ω-fluoroalk-1-ynyl)phenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-
yl)acetamides (7a-d) consisted in derivatizing a key iodinated building block featuring
the pyrazolopyrimidine acetamide backbone of DPA-714, by Sonogashira couplings
with various alkynyl reagents. The resulting alkynols were subsequently fluorinated,
yielding the expected target derivatives. All four analogues exhibited slightly higher
affinity and selectivity towards
the TSPO 18 kDa (Ki vs [3H]PK11195 : 0.35-0.79 nM ; Ki vs [3H]flunitrazepam : >
1000 nM) when compared to DPA-714 (Ki vs [3H]PK11195 : 0.91 nM ; Ki vs
[3H]flunitrazepam : > 1000 nM). Lipophilicities (HPLC, LogD7.4) increased with the
chain length (from 3.6 to 4.3) and were significantly higher than the one determined
for DPA-714 (2.9). Preliminary in vitro metabolism evaluation using rat microsomal
incubations and LC-MS analyses showed, for all four novel analogues, the absence of
defluorinated metabolites. Among them, the fluoropentynyl compound, DPA-C5yne
(7c), was selected, labelled in one single step with fluorine-18 from the corresponding
tosylate and in vivo evaluated with PET on our in-house-developed rat model of acute
local neuroinflammation.
The translocator protein (TSPO 18 kDa), formerly known as the peripheral benzodiazepine
receptor (PBR), is a highly lipophilic tryptophan-rich protein comprising 169 amino acids.1-3
It is located in the outer mitochondrial membrane of cells where it combines with a 32 kDa
voltage-dependent anion channel (VDAC) and a 30 kDa adenine nucleotide carrier (ANC).3,4
This trimeric complex, involved in the mitochondrial permeability transition pore (MPTP),
plays an important role in certain transport processes. For example, it is well-established that
TSPO controls the translocation of cholesterol from the outer to inner mitochondrial
membrane, where it is converted to pregnenolone, a key intermediate for the biosynthesis of
steroids.5 While it is minimally produced in the healthy brain,6 the translocator protein is
overexpressed in inflamed brains.7-9 As a result, TSPO has become over the years an
attractive biological target for imaging neuroinflammatory disorders, for example in
Alzheimer’s or Parkinson’s disease, using PET.10
1

Regarding TSPO tracers, the first PET-radioligand synthesized, the isoquinoline
carboxamide [11C]PK11195 (Figure 1), has been used clinically since 1984.11 Even though it
is still considered as a standard, [11C]PK11195 presents serious limitations for PET imaging
such as a poor signal-to-noise ratio and low brain penetration as well as the short radioactive
half-life of carbon-11 (t1/2 = 20.4 min).12 These drawbacks have encouraged the design of
improved radiotracers.13-18 For instance, in the phenoxyphenyl acetamide class,
[11C]DAA1106 was found to exhibit a higher specificity19-21 and its fluorinated analogue,
FEDAA1106, labelled with the longer half-lived positron-emitter fluorine-18 (t1/2 = 109.8
min), turned out to be also a better radioligand, with a better signal-to-noise ratio compared to
[11C]PK11195.22-23 [18F]PBR06 is another representative of this series that has been labelled
with introduction of the fluorine-18 at the N-acyl function.24,25 Concomitantly, carbon-11 or
fluorine-18-labelled compounds featuring a pyridine motif were developed. Among them,
[11C]PBR28, a ligand displaying encouraging in vivo imaging properties,26-32 and the
fluorinated analogues 6-[18F]fluoro-PBR28 and [18F]FEPPA, were reported in the literature.33-
35
Another class of high affinity TSPO ligands gathers compounds related to the
imidazopyridine alpidem36 (Figure 1). A well-known fluorine-18-labelled example of this
class is [18F]PBR111.37,38 Bioisosteric derivatives such as pyrazolopyrimidine acetamides
have also been developed to target the TSPO. Within this sub-class, the best known
compounds are [11C]DPA-71339-45 and [18F]DPA-71442,43,46-59 (Figure 1), both already in vivo
evaluated at the preclinical and clinical stage. Even though [18F]DPA-714 has a slightly
higher lipophilicity than [11C]DPA-713, which could lead to an increased non-specific
binding, this radioactive compound allows longer imaging protocols and therefore can be
considered as a more suitable radiotracer. The use of radioligands belonging to this class may
also facilitate accurate quantitative interpretation of the PET data. Indeed, pyrazolopyrimidine
acetamides show a relatively low difference in affinity (~ 4 fold) between the high- (HABs)
and the low- or the mixed-affinity binders (LABs / MABs), when compared to the N-benzyl-
N-(2-phenoxyaryl) acetamides PBR06 (~ 17 fold) or PBR28 (~ 50 fold).60-62 Thus, the impact
of inter-individual variations which are linked to the expression of different TSPO binding
sites encoded by the rs6971 polymorphism at the gene level could be reduced, and may not
require subject genotyping.
Recent studies clearly demonstrated [18F]DPA-714 that rapidly and extensively undergoes
in vivo metabolism in both rodents (rats) and non-human primates (baboons). In particular, the
observed fluoroethoxy side chain cleavage leads to the formation of small radiometabolites
entering the brain and lowering PET imaging quality and restraining quantitative analysis.63,64
Regarding this metabolic pathway, we intended to improve DPA-714 stability by replacing
the oxygen atom bridging the phenyl group and the fluoroethyl motif by a methylene unit.
Such a modification gave rise to a new compound named CfO-DPA-714 whose
corresponding fluorine-18-labelled version ([18F]CfO-DPA-714, Figure 1) has recently been
prepared and is currently evaluated in vivo.65
2

Figure 1. Selected TSPO ligands, including, at the right bottom corner, the general structure of the DPA-714 alkynyl analogues synthesized
in the present work.
In this article, we report the chemical synthesis (Scheme 1 and Scheme 2) of a new
subclass of DPA-714 analogues featuring an alkyne triple bond and a short alkane spacer
linking the pyrazolopyrimidine scaffold and the fluorine atom (Figure 1). The series includes
four compounds with a side chain ranging from three to six carbon atoms (7a-d). Preliminary
evaluation of some of their physical and in vitro biological properties (logD7.4, Ki against
[3H]PK11195 and [3H]flunitrazepam) as well as in vitro metabolism studies for all four
compounds are described. In addition, fluorine-18-labelling and first in vivo PET-imaging of
one of them is also presented herein.
The synthesis of DPA-714 alkynyl analogues 7a-d was envisaged from the key
iodopyrazolopyrimidine 5 using the pathway depicted in Scheme 1.
Thus, the synthesis of compounds 7a-d started with a nucleophilic addition of acetonitrile
carbanion on the commercially available methyl 4-iodobenzoate 1, leading to 3-
oxopropanenitrile 2 upon the loss of the methoxide moiety. The reaction, initially performed
with NaOMe in boiling acetonitrile,39 was improved by using n-BuLi as a base at low
temperature.66 This strategy allowed to decrease ester hydrolysis and resulted in an improved
reaction yield of 70 % compared to maximum 45% when using NaOMe. The resulting β-
ketonitrile 2 was then C-alkylated with N,N-diethylchloroacetamide in presence of NaI in
ethanolic sodium hydroxide. This reaction usually took a few days to reach completion and
resulted in the formation of the expected N,N-diethylamide 3 with a modest yield of 40 %. In
the next step, compound 3 was subjected to a first cyclization using monohydrated hydrazine
in refluxing acetic acid to lead to the aminopyrazole 4 which was isolated in a moderate yield
of 39 %. Finally, reaction of compound 4 with acetylacetone in boiling ethanol for 5 h
allowed the pyrazolopyrimidine ring formation in 77% yield, and moreover in a clean and
easy way since no side-product formation was observed. While cooling down the reaction
mixture, the iodopyrazolopyrimidine 5 often crystallized in a pure form (shiny white solid)
that did not require additional purification. In our synthesis strategy, compound 5 was a key
intermediate since it could give access to a wide range of fluorinated alkynyl compounds in a
straightforward (two steps) and versatile way. To generate the analogues 7a-d, first
Sonogashira couplings between 5 and the appropriate alkynyl alcohols were carried out to
3

give the alkynols 6a-d in good to excellent yields (69 to 94 %). Then, compounds 6a-d were
submitted to fluorodeoxygenation using Deoxofluor® in methylene chloride to yield 7b-d
with variable efficiency (19 to 62 %). Typically, the reaction mixture was worked up after 48
h. For analogue 7b, it is important not to run the reaction for too long otherwise a side-product
involving allene formation is produced.
Finally, analogues 7b-d were produced in six steps with chemical purities higher than 95
% (1H NMR). Their structures were confirmed by 1H NMR, 13C NMR and MS (Table 1).67
Scheme 1. Synthesis of the DPA-714 alkynyl analogues 7a-d. Reagents and conditions: (a) n-BuLi, CH3CN, THF, 30 min, -65 °C then
methyl 4-iodobenzoate (1), 2 h, -65 °C to -45 °C; (b) NaOH, EtOH, 15 min then ClCH2C(O)NEt2, NaI, 4 days, r.t.; (c) N2H4.H2O, AcOH,
EtOH, 5-8 h, 80 °C; (d) acetylacetone, EtOH, 5 h, 80 °C; (e) alkynyl alcohol, CuI, Pd(PPh3)2Cl2, Et2NH, 24 h, r.t.; (f) Deoxofluor®, CH2Cl2,
2-4 days, r.t.
Regarding the analogue 7a, since the fluorodeoxygenation turned out to be only partially
successful when applied to alcohol 6a, a different pathway was considered (Scheme 2). For
the preparation of this compound (7a), the major improvement was made by performing the
fluorination at the very beginning of the synthesis as depicted below (Scheme 2).
Thus, starting with the iodoester 1, a Sonogashira coupling using 2-propyn-1-ol was first
carried out to yield the propargylic alcohol 8 in 76 % yield. Then, 8 was submitted to
fluorodeoxygenation using Deoxofluor® at room temperature in methylene chloride. Although
this reaction was not clean (several by-products were observed on TLC), the fluoroester 9 was
successfully isolated with a good purity in 30 % yield. The oxopropanenitrile 10 was then
obtained in good to excellent yields (92 %) using similar conditions to those previously
described. Analogously, C-alkylation with N,N-diethylchloroacetamide gave the amide 11 in a
moderate 47 % yield. Cyclisation with hydrazine led to the aminopyrazole 12 in a moderate
yield of 34 %, and was further converted to the pyrazolopyrimidine 7a (81 % yield). Finally,
the target fluoropropynyl compound 7a was also obtained in six steps with a high purity and
its structure was confirmed by 1H NMR, 13C NMR and MS (Table 1).67
4

Scheme 2. Synthesis of the DPA-714 alkynyl analogue 7a. Reagents and conditions: (a) 2-propyn-1-ol, CuI, Pd(PPh3)2Cl2, Et2NH, 24 h, r.t.;
(b) Deoxofluor®, CH2Cl2, 2 days, r.t.; (c) n-BuLi, CH3CN, THF, 30 min, -60 °C then compound 9, 2 h, -60 °C; (d) NaOH, EtOH, 15 min then
ClCH2C(O)NEt2, NaI, 4 days, r.t.; (e) N2H4.H2O, AcOH, EtOH, 5 h, 80 °C; (f) acetylacetone, EtOH, 8 h, 80 °C.
Table 1
Analytical characterization (MS, 1H NMR and 13C NMR data) of DPA-714 fluoroalkynyl analogues 7a-d.
Fluoroalkynyl side chain 1H NMR
Fluoroalkynyl side chain13C NMR
Compd
7a
R
MW
m/za,b
chemical shifts (δ, ppm, CDCl3)c,d
chemical shifts (δ, ppm, CDCl3)c,d
89.5 [d, J3CF = 12 Hz, C], 83.2 [d, J2
=
CF
CH2-F
392
393
5.20 (d, 2H, J2HF = 47.6 Hz).
22 Hz, C], 71.1 [d, J1CF = 164 Hz, CH2].
4.60 (dt, 2H, J2HF = 46.8 Hz, J3HH = 6.8 Hz),
2.86 (dt, 2H, J3HF = 19.2 Hz, J3HH = 6.8 Hz).
89.4 [C], 85.1 [C], 81.3 [d, J1CF = 171
Hz, CH2], 21.6 [d, J2CF = 24 Hz, CH2].
7b
7c
(CH2)2-F
(CH2)3-F
406
420
407
421
4.62 (dt, 2H, J2HF = 47.2 Hz, J3HH = 6.0 Hz),
89.3 [C], 82.5 [d, J1CF = 164 Hz, CH2],
81.2 [C], 29.5 [d, J2CF = 20 Hz, CH2],
15.4 [d, J3CF = 4 Hz, CH2].
2.59 (t, 2H, J = 7.2 Hz), 2.01 (dq5, 2H, J3
= 25.6 Hz, J3HH = 6.0 Hz).
HF
4.52 (dt, 2H, J2HF = 47.2 Hz, J3HH = 6.0 Hz),
2.50 (t, 2H, J = 7.2 Hz), 1.89 (m, 2H),
1.75 (q5, 2H, J = 7.2 Hz).
90.3 [C], 83.6 [d, J1CF = 164 Hz, CH2],
81.1 [C], 29.5 [d, J2CF = 20 Hz, CH2],
24.4 [d, J3CF = 5 Hz, CH2], 19.1 [CH2].
7d
(CH2)4-F
434
435
a ESI+ ionization ; b value corresponding to the [M+H]+ peak; c Recorded on a 400 MHz Bruker Avance; d See note 67 in the “references and
notes” section for a complete NMR description of compounds 7a-d.
The logD7.4 (n-octanol/buffer pH 7.4 partition coefficient) of compounds 7a-d were
evaluated on the basis of their HPLC retention times68 and were also calculated using the
ACD 11.0 software (Table 2). As expected, both measured and calculated logD7.4 values
where higher than those calculated for DPA-714, and increased as the fluorinated side chain R
lengthened. Additionally, while analogues 7a and 7b exhibited comparable experimental
logD7.4 values, 3.61 and 3.67 respectively, 7c and 7d were found to be significantly more
lipophilic with values slightly above 4.0.
The in vitro binding affinities of compounds 7a-d for the TSPO 18 kDa were determined
by competition with [3H]PK11195 using membrane homogenates from rat heart. All four
analogues exhibited high affinities for the protein with subnanomolar Ki values - all lower
than the one measured for DPA-714 in the same assays - ranging from 0.35 nM (7c) to 0.79
nM (7d), as well as high specificity since no affinity for the central benzodiazepine receptor
(CBR) was observed (Table 2).
5

Table 2
Lipophilicities and binding affinities of the DPA-714 fluoroalkynyl analogues 7a-d.
Ki (TSPO)
(nM)d
Ki (CBR)
(nM)e
b
c
Compd
R
HPLC tR (min)a
logD7.4
clogD7.4
DPA-714
O-(CH2)2-F
1.10
1.19
1.20
1.30
1.33
2.89
3.61
3.67
4.06
4.35
3.21
3.81
4.19
4.58
5.03
0.91
0.54
0.74
0.35
0.79
> 1000
> 1000
> 1000
> 1000
> 1000
7a
7b
7c
7d
C≡C-CH2-F
C≡C-(CH2)2-F
C≡C-(CH2)3-F
C≡C-(CH2)4-F
a HPLC conditions: UPLC/SQD Acquity BEH C18 column, 2.1 x 50 mm, 1.7 µm, mobile phase : H2O (A) / CH3CN + 0.1 % formic
acid (B), gradient: 2 to 100 % (B) in 3 min, 1.0 mL/min; b See note 68 in the “references and notes” section for description of the logD7.4
determination method using HPLC. c Calculated with ACD 11.0 software. d Ki values were determined using membrane homogenates
from rat heart and screened against [3H]PK11195 (Kd = 1.8 nM, C = 0.2 nM); e Ki values were determined using membrane
homogenates from rat cerebral cortex and screened against [3H]flunitrazepam (Kd = 2.1 nM, C = 0.4 nM).
Table 3
Microsomal metabolites of the DPA-714 fluoroalkynyl analogues 7a-d (LC-MS and MS-MS analyses).
7a (m/z 392)
7b (m/z 406)
[M+H]+
Compounds
tR (min)a
[M+H]+
Fragmentsb
tR (min)a
Fragmentsb
Parent
M1
15.66
11.41
11.0
-
393
375, 346, 320, 292
15.81
11.68
11.19
10.01
5.89
407
389, 360, 334, 306
361, 334, 306
347, 320, 292
365 (−28)
379 (−28)
423 (+16)
423 (+16)
439 (+32)
M2
409 (+16)
391, 362, 336, 308
405, 376, 350, 322
405, 376, 350, 322
421, 392, 366, 338
M3
-
-
-
-
M4
-
7c (m/z 420)
7d (m/z 434)
Compounds
tR (min)a
[M+H]+
Fragmentsb
tR (min)a
[M+H]+
Fragmentsb
Parent
M1
17.05
12.08
11.37
8.92
421
403, 348, 320
375, 348, 320
419, 364, 336
419, 364, 336
435, 380, 353
15.81
11.68
11.19
10.01
5.89
435
417, 362, 334
362, 334, 306
393 (−28)
437 (+16)
437 (+16)
453 (+32)
407 (−28)
451 (+16)
451 (+16)
467 (+32)
M2
433, 404, 378, 350
433, 404, 378, 350
449, 420, 394, 366
M3
M4
3.43
a HPLC conditions: Atlantis C18 column, 2.1 x 150 mm, 5 µm, mobile phase : H2O + 0.05% formic acid (A) / CH3CN + 0.05%
formic acid (B), gradient (A / B) : 60:40 to 20:80 (20 min), 200 µL/min, detection at 275 nm. b See reference 69 in the “references
and notes” section for a complete description of the materials and methods used for ESI-MS-MS analyses.
6

The metabolism of the four novel DPA-714 fluoroalkynyl analogues (7a-d) was also studied in vitro in rat liver
microsomes.69 Liquid chromatography-mass spectrometry (LC-MS and MS-MS) analyses, after 30 minutes of
incubation, allowed the detection of the main metabolites formed for each analogue. The formation of two to
four metabolites (M1 to M4) was observed as summarized in Table 3. For all four analogues 7a-d, no
metabolites resulting from the loss of the fluorine atom by cleavage of the fluoroalkynyl side chain was observed
by LC-MS. The predominant metabolites, detected by HPLC at 275 nm and characterised by ESI-MS-MS
analyses according to their fragmentation profiles, resulted from N-deethylation (M1, −28 Da) at the
diethylacetamide position and also from hydroxylation (M2 and M3, +16 Da) or dihydroxylation (M4, +32 Da)
most probably on the methyl groups of the pyrazolo-pyrimidine part of the molecule as already observed for
DPA-714.69
The fluoropentynyl analogue 7c (coded DPA-C5yne), displaying the highest TSPO binding affinity and a
favourable in vitro metabolic profile, was chosen for radiofluorination70,71 and first in vivo evaluation as potential
PET imaging tool. Indeed, despite the good in vitro profile of the fluoropropynyl analogue 7a that features an
improved TSPO affinity in comparison to DPA-714, a better lipophilicity value than 7c and only two main in
vitro metabolites after 30 minutes microsomal incubation, compound 7c was preferred based on i) the difficulties
encountered to generate the corresponding precursor for labelling (tosyloxy derivative of 6a) and ii) our past
experience with compounds bearing comparable motif, e.g. the predicted issues to get efficient radiolabelling.
Thus, the tosylate 13 was prepared from the alkynol 6c by treatment with p-toluenesulfonic
anhydride in dichloromethane in the presence of TEA at room temperature for 2-3 days, and
obtained in 54% yield. Fluorine-18-labelling was then performed in a single-step procedure
by nucleophilic aliphatic substitution using the activated K[18F]F-Kryptofix K222 complex as
the fluorinating reactant, in DMSO and heating at 100°C for 10 minutes72 on a TRACERLab
FX N Pro synthesizer (GEMS). Ready-to-inject 7c (> 99% chemically and radiochemically
pure, 55 to 110 GBq/µmol) was obtained in 20-25% decay-corrected yields (based on starting
[18F]fluoride) and within 50-60 min, semi-preparative HPLC purification and SepPak® Plus-
based formulation included.
Scheme 3. Synthesis of the labelling precursor 13 and radioligand [18F]-7c. Reagents and conditions: (a) Ts2O, CH2Cl2, TEA, r.t., 3h; (b) i)
K[18F]F-K222, K2CO3, DMSO, 100°C, 10 min, ii) cartridge purification (SepPak® Alumina N TM), iii) HPLC purification (Waters Symmetry®
C-18).
First imaging properties of [18F]DPA-C5yne ([18F]-7c) were investigated in vivo with PET (INVEON PET/CT
and PET only tomographes, Siemens) and compared to [18F]DPA-714 on our in-house-developed rat model of
acute local neuroinflammation. MicroPET studies were performed on anesthetized brain-lesioned Wistar rats 7
days after AMPA injection in their right striatum.73 As shown in Figure 2A, the lesion (indicated by the white
cross-cursor) could clearly be identified within the rat’s brain from 5 minutes post-i.v.-injection of [18F]-7c until
the end of the PET acquisition. A relatively high contrast between the lesioned area and the corresponding area
in the intact contralateral hemisphere was also observed. Uptake of [18F]-7c in the lesioned striatum was high
(0.24 percent of injected dose per milliliter (% ID/mL) at 60 min, Figure 2B) but slightly lower than the one
routinely observed for [18F]DPA-714 (0.30 % ID/mL, same time). Uptake of [18F]-7c in the contralateral side
was also significantly lower (0.05 % ID/mL at 60 min) than the one reported for [18F]DPA-714 (0.08 % ID/mL
at 60 min, respectively). Thus, an in vivo ipsilateral-to-contralateral ratio of 4.62 0.4 (p < 0.0001), calculated as
the bound tracer in the lesion versus the bound tracer in the contralateral side at 60 minutes post-injection, was
found for [18F]-7c, a notably higher value than the one measured for [18F]DPA-714 (3.71 0.4 (p < 0.001) or
[11C]PK11195 (1.65 0.2 (p < 0.001), data not shown).
7

Figure 2. (A) MicroPET axial, coronal and sagittal summed images (5 - 60 minutes) following i.v. injection of [18F]DPA-C5yne ([18F]-7c) in
AMPA-lesioned rat. A cross-cursor indicates in each section the visible right-side lesion. (B) Comparative time-activity curves expressed in
between [18F]DPA-C5yne ([18F]-7c) and [18F]DPA-714. Data are expressed in percent of injected dose per milliliter (% ID/mL) versus
minutes (min).
Four novel closely related analogues of DPA-714 (7a-d) featuring a fluoroalkynyl side
chain in replacement of the fluoroethoxy motif, have been synthetized in six steps from
commercially available methyl 4-iodobenzoate. All target derivatives showed a high affinity
and specificity toward the TSPO 18 kDa (as the parent molecule DPA-714). These
compounds (7a-d) exhibited rather high lipophilicities compared to DPA-714, which
nevertheless, keeps in the range favored for good passive cerebral penetration. Preliminary in
vitro metabolism evaluation using rat microsomal incubations and LC-MS analyses have
confirmed, for all derivatives, the stability of the chosen fluorination position, i.e. the alkynyl
side chain. This results portend, in contrast to [18F]DPA-714, the absence in vivo of small
interfering radiofluorinated metabolites formation. Among the four analogues prepared, the
fluoropentynyl compound 7c was successfully labelled with fluorine-18 and its subsequent
first PET in vivo evaluation has demonstrated its potential to image the TSPO 18 kDa.
Additional studies, including in vivo metabolism analysis, in acute and chronic models of
neurodegeneration will be performed in order to further evaluate the potential of this
radioligand as a biomarker of neuroinflammation in neuropathological conditions.
Aknowledgements
The authors wish to thank LGCR Analytical Sciences (Sanofi, Chilly Mazarin) for logD
measurements, Cyrielle Letaillandier for her technical assistance as well as Dr Dirk Roeda for
proof reading the manuscript and suggesting linguistic corrections. This work was supported
by CEA-I2BM intramural programs, as well as the European Union’s Seventh Framework
Programme [FP7/2007-2013] INMiND (Grant agreement n° HEALTH-F2-2011-278850).
PhD students Vincent Médran-Navarrete and Nicholas Bernards were in part supported by a
CEA Irtelis doctoral grant and the EU FP7 INMiND program (see above), respectively.
8

References and notes
1. Beurdeley-Thomas, A.; Miccoli, L.; Oudard, S.; Dutrillaux, B.; Poupon, M. F. J. Neurooncol. 2000, 46, 45.
2. Joseph-Liauzun, E.; Delmas, P.; Shire, D.; Ferrara, P. J. Biol. Chem. 1998, 273, 2146.
3. Papadopoulos, V.; Baraldi, M.; Guilarte, T. R.; Knudsen, T. B.; Lacapere, J.-J.; Lindemann, P.; Norenberg,
M. D.; Nutt, D.; Weizman, A.; Zhang, M.-R.; Gavish, M. Trends Pharmacol. Sci. 2006, 27, 402.
4. Casellas, P.; Galiegue, S.; Basile, A. S. Neurochem. Int. 2002, 40, 475.
5. Papadopoulos, V.; Brown, A. S. J. Steroid Biochem. Mol. Biol. 1995, 53, 103.
6. Gavish, M.; Bachman, I.; Shoukrun, R.; Katz, Y.; Veenman, L.; Weisinger, G.; Weizman, A. Pharmacol.
Rev. 1999, 51, 629.
7. Bourguignon, J. J. in Endogenous and synthetic ligands of mitochondrial benzodiazepine receptors:
structure-affinity relationships, Peripheral Benzodiazepine Receptors (Ed., E. Giensen-Crouse), Academic
Press, London, 1993, 59-85.
8. Kettenmann, H.; Burton, G. A.; Moenning, U. J. in Neuroinflammation - from Bench to Bedside (Ed.: Ernst
Schering Research Foundation), Springer, Berlin, Heidelberg, 2002, 1-234.
9. Raghavendra Rao, V. L.; Dogan, A.; Bowen, K. K.; Dempsey, R. J. Exp. Neurol. 2000, 161, 102.
10. Rupprecht, R.; Papadopoulos, V.; Rammes, G.; Baghai, T. C.; Fan, J.; Akula, N.; Groyer, G.; Adams, D.;
Schumacher, M. Nat. Rev. Drug Discovery 2010, 9, 971.
11. Camsonne, R.; Crouzel, C.; Comar, D.; Mazière, M.; Prenant, C.; Sastre, J.; Moulin, M. A.; Syrota, A. J.
Labelled Compd. Radiopharm. 1984, 21, 985.
12. Banati, R. B.; Newcombe, J.; Gunn, R. N. ; Cagnin, A.; Turkheimer, F.; Heppner, F.; Price, G.; Wegner, F.;
Giovannoni, G.; Miller, D. H.; Perkin, D. G.; Smith, T.; Hewson, A. K.; Bydder, G.; Kreutzberg, G. W.;
Jones, T.; Cuzner, M. L.; Myers, R. Brain 2000, 123, 2321.
13. Chauveau, F.; Boutin, H.; Van Camp, N.; Dollé, F.; Tavitian, B. Eur. J. Nucl. Med. Mol. Imaging. 2008, 35,
2304.
14. Dollé, F.; Luus, C.; Reynolds, A.; Kassiou, M. Curr. Med. Chem. 2009, 16, 2899.
15. Luus, C.; Hanani, R.; Reynolds, A.; Kassiou, M. J. Labelled Compd. Radiopharm. 2010, 53, 501.
16. Scarf, A. M.; Kassiou, M. J. Nucl. Med. 2011, 52, 677.
17. Roeda, D.; Kuhnast, B.; Damont, A.; Dollé, F. J. Fluor. Chem. 2012, 134, 107.
18. Ching, A. S. C.; Kuhnast, B.; Damont, A.; Roeda, D.; Tavitian, B.; Dollé, F. Insights into Imaging 2012, 3,
111.
19. Maeda, J.; Suhara, T.; Zhang, M. R.; Okauki, T.; Yasuno, F.; Ikoma, Y.; Inaji, M.; Nagai, Y.; Takano, A.;
Obayashi, S.; Suzuki, K. Synapse 2004, 52, 283.
20. Chaki, S.; Funakoshi, T.; Yoshikawa, R.; Okuyama, S.; Okubo, T.; Nakazato, A.; Nagamine, M.;
Tomisawa, K. Eur. J. Pharmacol. 1999, 371, 197.
21. Zhang, M. R.; Kida, T.; Noguchi, J.; Furutsuka, K.; Maeda, J.; Suhara, T.; Suzuki, K. Nucl. Med. Biol.
2003, 30, 513.
22. Fujimura, Y.; Ikoma, Y.; Yasuno, F.; Suhara, T.; Ota, M.; Matsumoto, R.; Nozaki, S.; Takano, A.; Kosaka,
J.; Zhang, M. R.; Nakao, R.; Suzuki, K.; Kato, N.; Ito, H. J. Nucl. Med. 2006, 47, 43.
23. Zhang, M. R.; Maeda, J.; Ogawa, M.; Noguchi, J.; Ito, T.; Yoshida, Y.; Okauchi, T.; Obayashi, S.; Suhara,
T.; Suzuki, K. J. Med. Chem. 2004, 47, 228.
24. Briard, E.; Shah, J.; Musachio, J. L.; Zoghbi, S. S.; Fujita, M.; Imaizumi, M.; Cropley, V.; Innis, R. B.;
Pike, V. W. J. Labelled Compd. Radiopharm. 2005, 48, S4.
25. Briard, E.; Zoghbi, S.S.; Simeon, F. G.; Imaizumi, M.; Gourley, J. P.; Shetty, H. U.; Lu, S. Y.; Fujita, M.;
Innis, R. B.; Pike, V. W. J. Med. Chem. 2009, 52, 688.
26. Briard, E.; Hong, J.; Musachio, J. L.; Zoghbi, S. S.; Fujita, M.; Imaizumi, M.; Cropley, V.; Innis, R. B.,
Pike, V. W. J. Labelled Compd. Radiopharm. 2005, 48, S71.
27. Imaizumi, M.; Kim, H.-J.; Zoghbi, S. S.; Briard, E.; Hong, J.; Musachio, J. L.; Ruetzler, C.; Chuang, D. M.;
Pike, V. W.; Innis, R. B.; Fujita, M. Neurosci. Lett. 2007, 411, 200.
28. Brown, A. K.; Fujita, M.; Fujimura, Y.; Liow, J.-S.; Stabin, M.; Ryu, Y. H.; Imaizumi, M.; Hong, J.; Pike,
V. W.; Innis, R. B. J. Nucl. Med. 2007, 48, 2072.
9

29. Briard, E.; Zoghbi, S. S.; Imaizumi, M.; Gourley, J. P.; Hong, J.; Cropley, V.; Fujita, M.; Innis, R. B.; Pike,
V. W. J. Med. Chem. 2008, 51, 17.
30. Imaizumi, M.; Briard, E.; Zoghbi, S. S.; Gourley, J. P.; Hong, J.; Fujimura, Y.; Pike, V. W.; Innis, R. B.;
Fujita, M. NeuroImage 2008, 39, 1289.
31. Fujita, M.; Imaizumi, M.; Zoghbi, S. S.; Fujimura, Y.; Farris, A. G.; Suhara, T.; Hong, J.; Pike, V. W.;
Innis, R. B. NeuroImage 2008, 40, 43.
32. Kreisl, W. C.; Fujita, M.; Fujimura, Y.; Kimura, N.; Jenko, K. J.; Kannan, P.; Hong, J.; Morse, C. L.;
Zoghbi, S. S.; Gladding, R. L.; Jacobson, S.; Oh, U.; Pike, V. W.; Innis, R. B. NeuroImage 2010, 49, 2924.
33. Damont, A.; Boisgard, R.; Kuhnast, B.; Lemée, F.; Raggiri, G.; Scarf, A. M.; Da Pozzo, E.; Selleri, S.;
Martini, C.; Tavitian, B.; Kassiou, M.; Dollé, F. Bioorg. Med. Chem. Lett. 2011, 21, 4819.
34. Wilson, A. A.; Garcia, A.; Parkes, J.; McCormick , P.; Stephenson, K. A.; Houle, S.; Vasdev, N. Nucl.
Med. Biol. 2008, 35, 305.
35. Mizrahi, R.; Rusjan, P. M.; Vitcu, I.; Ng, A.; Wilson, A. A.; Houle, S.; Bloomfield, P. M. Mol. Imaging
Biol. 2013, 15, 353.
36. Selleri, S.; Bruni, F.; Costagli, C.; Costanzo, A.; Guerrini, G.; Ciciani, G.; Costa, B.; Martini, C. Bioorg.
Med. Chem. 2001, 9, 2661.
37. Fookes, C. J. R.; Pham, T. Q.; Mattner, F.; Greguric, I.; Loc'h, C.; Liu, X.; Berghofer, P.; Shepherd, R.;
Grégoire, M.-C.; Katsifis, A. J. Med. Chem. 2008, 51, 3700.
38. Dollé, F.; Hinnen, F.; Damont, A.; Kuhnast, B.; Fookes, C.; Pham, T.; Tavitian, B.; Katsifis, A. J. Labelled
Compd. Radiopharm. 2008, 51, 435.
39. James, M. L.; Fulton, R. R.; Henderson, D. J.; Eberl, S.; Meikle, S. R.; Thomson, R.; Allan, D.; Dollé, F.;
Fulhma, M. J.; Kassiou, M. Bioorg. Med. Chem. 2005, 13, 6188.
40. Thominiaux, C.; Dollé, F.; James, M.; Bramoullé, Y.; Boutin, H.; Besret, L.; Grégoire, M.-C.; Valette, H.;
Bottlaender, M.; Tavitian, B.; Hantraye, P.; Selleri, S.; Kassiou, M. Appl. Radiat. Isot. 2006, 64, 570.
41. Boutin, H.; Chauveau, F.; Thominiaux, C.; Kuhnast, B.; Grégoire, M.-C.; James, M.; Jan, S.; Brulon, V.;
Fontyn, Y.; Selleri, S.; Trébossen, R.; Hantraye, P.; Dollé, F.; Tavitian, B.; Kassiou, M. J. Nucl. Med. 2007,
48, 573.
42. Doorduin, J.; Klein, H. C.; Dierckx, R. A.; James, M.; Kassiou, M.; de Vries, E. F. J. Mol. Imag. Biol.
2009, 11, 386.
43. Chauveau, F.; Van Camp, N.; Dollé, F.; Kuhnast, B.; Hinnen, F.; Damont, A.; Boutin, H.; James, M. L.;
Kassiou, M.; Tavitian, B. J. Nucl. Med. 2009, 50, 468.
44. Leaver, K. R.; Reynolds, A.; Bodard, S.; Guilloteau, D.; Chalon, S.; Kassiou, M. ACS Chemical
Neuroscience 2012, 3, 114.
45. Endres, C. J.; Coughlin, J. M.; Gage, K. L.; Watkins, C. C.; Kassiou, M.; Pomper, M. G. J. Nucl. Med.
2012, 53, 330.
46. James, M. L.; Fulton, R. R.; Vercouillie, J.; Henderson, D. J.; Garreau, L.; Chalon, S.; Dollé, F.; Costa, B.;
Guilloteau, D.; Kassiou. M. J. Nucl. Med. 2008, 49, 814.
47. Damont, A.; Hinnen, F.; Kuhnast, B.; Schollhorn-Peyronneau, M. A.; James, M. L.; Luus, C.; Tavitian, B.;
Kassiou, M.; Dollé, F. J. Labelled Compd. Radiopharm. 2008, 51, 286.
48. Fookes, C.; Pham, T.; Mattner, F.; Greguric, I.; Loc'h, C.; Liu, X.; Berghofer, P.; Shepherd, R.; Grégoire,
M. C.; Katsifis, A. J. Med. Chem. 2008, 51, 3700.
49. Martin, A.; Boisgard, R.; Theze, B.; Van Camp, N.; Kuhnast, B.; Damont, A.; Kassiou, M.; Dollé, F.;
Tavitian, B. J. Cereb. Blood Flow Metab. 2010, 30, 230.
50. Martin, A.; Boisgard, R.; Kassiou, M.; Dollé F.; Tavitian, B. Mol. Imag. Biol. 2011, 13, 10.
51. Zheng, J.; Boisgard, R.; Siquier-Pernet, K.; Decaudin, D.; Dollé, F.; Tavitian, B. Mol. Pharmaceutics 2011,
8, 823.
52. Winkeler, A.; Boisgard, R.; Awde, A. R.; Dubois, A.; Thézé, B.; Zheng, J.; Ciobanu, L.; Dollé, F.; Viel, T.;
Jacobs, A. H.; Tavitian, B. Eur. J. Nucl. Med. Mol. Imaging 2012, 39, 811.
53. Tang, D.; Hight, M. R.; McKinley, E. T.; Fu, A.; Buck, J. R.; Smith, R. A. Tantawy, M. N.; Peterson, T. E.;
Colvin, D. C.; Ansari, M. S.; Nickels, M.; Manning, H. C. J. Nucl. Med. 2012, 53, 287.
54. Arlicot, N.; Vercouillie, J.; Ribeiro, M. J.; Tauber, C., Venel, Y.; Baulieu, J. L.; Maia, S.; Corcia, P.,
Stabin, M. G.; Reynolds, A.; Kassiou, M.; Guilloteau, D. Nuc. Med. Biol. 2012, 39, 570.
55. Abourbeh, G.; Thézé, B.; Maroy, R.; Dubois, A.; Brulon, V.; Fontyn, F.; Dollé, F.; Tavitian, B.; Boisgard,
R. J. Neurosci. 2012, 32, 5728.
10

56. Lavisse, S.; Guillermier, M.; Hérard, A. S., Petit, F.; Delahaye, M.; Van Camp, N.; Ben Haim, L.; Lebon,
V.; Remy, P.; Dollé, F.; Delzescaux, T.; Bonvento, G.; Hantraye, P.; Escartin, C. J. Neurosci. 2012, 32,
10809.
57. Kuhnast, B.; Damont, A.; Hinnen, F.; Catarina, T.; Demphel, S.; Le Helleix, S.; Coulon, C.; Goutal, S.;
Gervais, P.; Dollé, F. Appl. Rad. Isot. 2012, 70, 489.
58. Corcia, P.; Tauber, C.; Vercoullie, J.; Arlicot, N.; Prunier, C.; Praline, J.; Nicolas, G.; Venel, Y.; Hommet,
C.; Baulieu, J. L.; Cottier, J. P.; Roussel, C.; Kassiou, M.; Guilloteau, D.; Ribeiro, M. J. PLoS One 2012, 7,
e52941.
59. Boutin, H.; Prenant, C.; Maroy, R.; Galea, J.; Greenhalgh, A. D.; Smigova, A.; Cawthorne, C.; Julyan, P.;
Wilkinson, S. M.; Banister, S. D.; Brown, G.; Herholz, K.; Kassiou, M.; Rothwell, N. J. PLoS One 2013, 8,
e56441.
60. Owen, D. R.; Howell, O. W.; Tang, S. P.; Wells, L. A.; Bennacef, I.; Bergström, M.; Gunn, R. N.; Rabiner,
E.A.; Wilkins, M. R.; Reynolds, R.; Matthews, P. M.; Parker, C. A. J. Cereb. Blood Flow Metab. 2010, 30,
1608.
61. Owen, D. R.; Gunn, R. N.; Rabiner, E. A.; Bennacef, I.; Fujita, M.; Kreisl, W. C.; Innis, R. B.; Pike, V. W.;
Reynolds, R.; Matthews, P. M.; Parker, C. A. J. Nucl. Med. 2011, 52, 24.
62. Owen, D. R.; Yeo, A. J.; Gunn, R. N.; Song, K.; Wadsworth, G.; Lewis, A.; Rhodes, C.; Pulford, D. J.;
Bennacef, I.; Parker, C. A.; StJean, P. L.; Cardon, L. R.; Mooser, V. E.; Matthews, P. M.; Rabiner, E. A.;
Rubio, J. P. J. Cereb. Blood Flow Metab. 2012, 32, 1.
63. Peyronneau, M. A.; Damont, A.; Valette, H.; Saba, W.; Delforge, J.; Goutal, S.; Bourgeois, S.; Hinnen, F.;
Dollé, F.; Bottlaender, M. J. Labelled Compd. Radiopharm. 2009, 52, S385.
64. Peyronneau, M. A.; Saba, W.; Goutal, S.; Damont, A.; Dollé, F.; Kassiou, M.; Bottlaender, M.; Valette, H.
Drug Metab. Dispos. 2013, 41, 122.
65. Damont, A.; Ching, A. S. C.; Médran-Navarrete, V.; Kuhnast, B.; Gaudy, H.; Dollé, F. J. Labelled Compd.
Radiopharm. 2011, 54, S461.
66. Fernandez, M.-C.; Castaño, A.; Dominguez, E.; Escribano, A.; Jiang, D.; Jimenez, A.; Hong, E.; Hornback,
W. J.; Nisenbaum, E. S.; Rankl, N.; Tromiczak, E.; Vaught, G.; Zarrinmayeh, H.; Zimmerman, D. M.
Bioorg. Med. Chem. Lett. 2006, 16, 5057.
67. Spectroscopic data. Compound 7a: 1H-NMR (CDCl3): δ 7.83 (d, 2H, J = 8.0 Hz), 7.55 (d, 2H, J = 8.0 Hz),
6.55 (s, 1H), 5.20 (d, 2H, J2HF = 47.6 Hz), 3.95 (s, 2H), 3.52 (q, 2H, J = 7.2 Hz), 3.40 (q, 2H, J = 7.2 Hz),
2.75 (s, 3H), 2.56 (s, 3H), 1.23 (t, 3H, J = 7.2 Hz), 1.11 (t, 3H, J = 7.2 Hz). 13C-NMR (CDCl3): δ 169.7
[C], 157.7 [C], 154.2 [C], 147.5 [C], 145.0 [C], 134.4 [C], 131.9 [2xCH], 128.5 [2xCH], 121.5 [d, J4CF = 4
Hz, C], 108.5 [CH], 101.4 [C], 89.5 [d, J3CF = 12 Hz, C], 83.2 [d, J2CF = 22 Hz, C], 71.1 [d, J1CF = 164 Hz,
CH2], 42.3 [CH2], 40.6 [CH2], 27.9 [CH2], 24.4 [CH3], 16.8 [CH3], 14.3 [CH3], 13.0 [CH3]. Compound 7b:
1H-NMR (CDCl3): δ 7.77 (d, 2H, J = 8.0 Hz), 7.48 (d, 2H, J = 8.0 Hz), 6.52 (s, 1H), 4.60 (dt, 2H, J2
=
HF
46.8 Hz, J3HH = 6.8 Hz), 3.94 (s, 2H), 3.50 (q, 2H, J = 7.2 Hz), 3.40 (q, 2H, J = 7.2 Hz), 2.86 (dt, 2H, J3
HF
= 19.2 Hz, J3HH = 6.8 Hz), 2.73 (s, 3H), 2.55 (s, 3H), 1.24 (t, 3H, J = 7.2 Hz), 1.11 (t, 3H, J = 7.2 Hz). 13C-
NMR (CDCl3): δ 169.6 [C], 157.6 [C], 154.0 [C], 147.5 [C], 145.1 [C], 133.2 [C], 131.7 [2xCH], 128.5
[2xCH], 123.1 [C], 108.3 [CH], 101.3 [C], 89.4 [C], 85.1 [d, J3CF = 6 Hz, C], 81.3 [d, J1CF = 171 Hz, CH2],
42.2 [CH2], 40.6 [CH2], 28.0 [CH2], 24.1 [CH3], 21.6 [d, J2CF = 24 Hz, CH2], 16.9 [CH3], 14.3 [CH3], 13.0
[CH3]. Compound 7c: 1H-NMR (CDCl3): δ 7.76 (d, 2H, J = 8.0 Hz), 7.47 (d, 2H, J = 8.0 Hz), 6.54 (s, 1H),
4.62 (dt, 2H, J2HF = 47.2 Hz, J3HH = 6.0 Hz), 3.97 (s, 2H), 3.50 (q, 2H, J = 7.2 Hz), 3.41 (q, 2H, J = 7.2
Hz), 2.76 (s, 3H), 2.59 (t, 2H, J = 7.2 Hz), 2.58 (s, 3H), 2.01 (dq5, 2H, J3HF = 25.6 Hz, J3HH = 6.0 Hz), 1.23
(t, 3H, J = 7.2 Hz), 1.12 (t, 3H, J = 7.2 Hz). 13C-NMR (CDCl3): δ 169.7 [C], 157.6 [C], 154.5 [C], 147.4
[C], 145.2 [C], 133.0 [C], 131.6 [2xCH], 128.4 [2xCH], 123.5 [C], 108.4 [CH], 101.3 [C], 89.3 [C], 82.5
[d, J1CF = 164 Hz, CH2], 81.2 [C], 42.2 [CH2], 40.6 [CH2], 29.5 [d, J2CF = 20 Hz, CH2], 28.0 [CH2], 24.3
[CH3], 16.9 [CH3], 15.4 [d, J3CF = 4 Hz, CH2], 14.3 [CH3], 13.0 [CH3]. Compound 7d: 1H-NMR (CDCl3): δ
7.76 (d, 2H, J = 8.0 Hz), 7.46 (d, 2H, J = 8.0 Hz), 6.54 (s, 1H), 4.52 (dt, 2H, J2HF = 47.2 Hz, J3HH = 6.0
Hz), 3.96 (s, 2H), 3.50 (q, 2H, J = 7.2 Hz), 3.42 (q, 2H, J = 7.2 Hz), 2.75 (s, 3H), 2.58 (s, 3H), 2.50 (t, 2H,
J = 7.2 Hz), 1.89 (m, 2H), 1.75 (q5, 2H, J = 7.2 Hz), 1.20 (t, 3H, J = 7.2 Hz), 1.10 (t, 3H, J = 7.2 Hz). 13C-
NMR (CDCl3): δ 169.6 [C], 157.6 [C], 154.9 [C], 147.5 [C], 146.0 [C], 132.7 [C], 131.6 [2xCH], 128.4
[2xCH], 123.8 [C], 108.3 [CH], 101.3 [C], 90.3 [C], 83.6 [d, J1CF = 164 Hz, CH2], 81.1 [C], 42.2 [CH2],
40.6 [CH2], 29.5 [d, J2CF = 20 Hz, CH2], 28.0 [CH2], 24.4 [d, J3CF = 5 Hz, CH2], 23.9 [CH3], 19.1 [CH2],
16.9 [CH3], 14.2 [CH3], 13.0 [CH3].
68. Determination of logD7.4 (HPLC). The retention time recorded for the tested compound was converted into its
logD7.4 value using a validated, standardized HPLC method (correlation between retention times and
known logD values of similar compounds). HPLC conditions: Alliance 2695 - PDA Waters, X-Terra MS
11

C18 (4.6 x 20 mm, 3.5 µm) column ; mobile phase 5 mM MOPS / (CH3)4NOH pH 7.4 (A), 5 % MOPS /
(CH3)4NOH (100 mM, pH 7.4) / 95 % CH3CN (B) ; gradient (A / B): 98:2 (0.5 min), 0:100 (4.8 min), 98:2
(1.6 min) ; 1.2 mL/min ; 25 °C ; detection at 254 nm.
69. Peyronneau, M. A.; Saba, W.; Goutal, S.; Damont, A.; Dollé, F.; Kassiou, M.; Bottlaender, M.; Valette, H.
Drug Metab. Dispos. 2013, 41, 122.
70. Dollé, F. J. Labelled Compd. Radiopharm. 2013, 56, 63.
71. Damont, A.; Roeda, D.; Dollé, F. J. Labelled Compd. Radiopharm. 2013, 56, 96.
72. Dollé, F.; Roeda, D.; Kuhnast, B.; Lasne, M.-C. In Fluorine and Health: Molecular Imaging, Biomedical
Materials and Pharmaceuticals, Tressaud, A., Haufe, G., Eds.; Elsevier: Amsterdam, 2008; pp 3-65.
73. Chauveau, F.; Van Camp, N.; Dollé, F.; Kuhnast, B.; Hinnen, F.; Damont, A.; Boutin, H.; James, M. L.;
Kassiou, M.; Tavitian, B. J. Nucl. Med. 2009, 50, 468.
12