A Pd(0) based cross-coupling approach to the synthesis of 2-amidopurines and their evaluation as CDK inhibitors

Article abstract of DOI:10.1016/j.bmc.2006.10.003

Two new series of 2-amido- and 2-aminocarbonylpurines have been synthesized using a Pd catalyst cross-coupling reaction either with amides or amines in the presence of CO. Moderate in vitro inhibitory activity against CDK1 and CDK5 was observed with IC

Full text of DOI:10.1016/j.bmc.2006.10.003

Bioorganic & Medicinal Chemistry 15 (2007) 130–141
A Pd(0) based cross-coupling approach to the synthesis of
2-amidopurines and their evaluation as CDK inhibitors
Lucie Vandromme,a Michel Legraverend,a,* Sergio Kreimerman,a Olivier Lozach,b
Laurent Meijerb and David S. Griersona
a
ˆ
UMR 176, Institut Curie, Bat. 110-112, Centre Universitaire, 91405 Orsay, France
bCNRS, Cell Cycle Group, Station Biologique, BP 74, 29682 Roscoff, France
Received 26 June 2006; revised 27 September 2006; accepted 4 October 2006
Available online 6 October 2006
Abstract—Two new series of 2-amido- and 2-aminocarbonylpurines have been synthesized using a Pd catalyst cross-coupling reac-
tion either with amides or amines in the presence of CO. Moderate in vitro inhibitory activity against CDK1 and CDK5 was
observed with IC50 of 0.9 lM for the most active compound (18c).
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
sive number of other potential applications of purines as
therapeutic agents and/or biological tools.17
The cyclin-dependent kinases (CDKs) are a family of
serine/threonine kinases that play a crucial role in cell
cycle division.1 In many forms of cancer a deregulation
of CDK function and consequent loss of cell cycle con-
trol are observed. This suggests that the development of
pharmacological inhibitors of CDKs may be an antican-
cer strategy.2 Abnormalities in CDK activity and regula-
tion are similarly observed in pain signaling and in
neurodegenerative disorders such as Alzheimer’s, Par-
kinson’s, and Nieman-Pick’s diseases. This provides fur-
ther impetus for the development of potent and selective
pharmacological inhibitors of these kinases.3,4 However,
it remains to be established what selectivity profile a
CDK inhibitor, and in particular CDK1 inhibitors,
should have for anti-cancer activity.5 Although many
families of CDK inhibitors are already known,6–12 pur-
ine CDK inhibitors3,13–16 are attractive because the pur-
Given the important influence of the side chain at C-2,
C-6, and N-9 on the potency and selectivity profile in
purine CDK inhibitors,4,13,18,19 it is of continued interest
to study new types of substituents at these positions in
order to delineate the specificity profile and scope of
applications of purine inhibitors. One option that has
received relatively little attention are purine compounds
with an amide or urea functions in their structure
(Fig. 1).20–27 In this context, compounds 1 and 2 were
found to be potent p38 MAP kinase inhibitors,26 and
unlike other trisubstituted purine analogues, compound
3 shows a good affinity for GSK3.27 The related furo-
pyrimidine 4 is also a potent inhibitor of GSK-3b21
and displays submicromolar activity (IC50 = 457 nM)
against CDK2. The presence of amide functionality is
central to the affinity of the Sugen type indolinones 5
and 6 for different kinases, and it was found that inhibi-
tion of CDK4/cyclin D1 and CDK2/cyclin E by com-
pound 7 was dramatically improved by incorporation
of an amide containing motif in its structure
(7 ! 8 ! 9).23 Replacing the anilinophthalizine unit in
the KDR/Flt1 inhibitor 10 by a simple benzamide sys-
tem as in 11 was also found to be possible.20
ine scaffold allows
a great variety of structural
modifications to be made at the 2, 6, and 9 positions. In-
deed, the synthesis and screening of a wide range of
polyfunctionalized purine compounds (purine libraries)
has permitted an optimization of their activity relative
to the CDK’s, and it has also brought to light an impres-
Based upon these results, it was considered pertinent to
develop methodology for the synthesis of 2,6,9-trisubsti-
tuted purines incorporating either a –NHCOR or a
CONHR motif at C-2, and to evaluate such compounds
Keywords: Purine; CDK inhibitors; Amidation; Carbonylative amina-
tion; Amidopurine.
*
Corresponding author. Tel.: +1 69 86 30 85; fax: +1 69 0753 81;
e-mail: Michel.Legraverend@curie.u-psud.fr
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.10.003

L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
131
CF
3
F
O
N
F
O
H N
2
N
F
N
HN
NH
N
N
N
N
N
N
O
O
N
O
O
N
N
R
N
H N
2
R = CH -N(CH )
IC = 82nM
50
1
2
3
4
2
3 2
GSK-3β : IC50 = 5 nM
CDK2 : IC = 457 nM
VEGFR-2 : IC = 24000 nM
R = Phenyl
IC = 16nM
50
50
50
GSK3 inhibitor
p38 MAP kinase inhibitor
NEt
O
2
CDK4/D1: IC = 23 μM
7
8
50
R = NH
2
CDK2/E: IC50 = 8.4 μM
4'
N
R'
R
(SU-11248)
H
O
N
CDK4/D1: IC = 0,46 μM
H
R = NHCOCH
50
3
O
CDK2/E: IC50 = 0,51 μM
N
F
H
N
O
H
(SU5416)
CDK4/D1: IC = 0,026 μM
N
R = NHCOCH -
2
4-amidopiperazine
5
6
50
9
N
N
H
50
H
CDK2/E: IC50 = 0,007 μM
VEGFR-2 : IC = 2,43 μM
= 80 nM; PDGF-Rβ : IC = 2 nM
VEGFR-2 : IC
Cl
50
50
Cl
NH
NH
O
HN
N
N
10
11
KDR and Flt -1(VEGFR)
N
N
IC = 37 nM and 77nM
50
IC = 20 nM and 180 nM
50
Figure 1. Examples of kinase inhibitors which have been improved by the presence of an amide chain in their structure.
for their capacity to inhibit CDK1/cyclinB, CDK5/p25,
and GSK-3b. Given the ready availability of 2-iodo-6-
chloro and 6-benzylsulfanylpurines bearing diverse
functionality at N-9, attention was directed to the use
of Pd(0)-catalyzed cross-coupling reactions involving
these 2-iodo purines for this purpose. Palladium-cata-
lyzed amidations of aryl halides have been reported by
Buchwald,28–31 Hartwig32–34 and others35,36 and were
recently applied to 6-bromopurine.37 To our knowledge,
the Pd(0)-mediated amidation and carbonylative amina-
tion of purine substrates at C-2 have not been reported.
derivative along with a 2-amido-6-oxo purine derivative
in low yield.
To obtain the trisubstituted ‘amidopurines’ 18, 19, and
20 the option was thus taken to functionalize the C-6
position prior to the key amidation reaction at C-2
through reaction of 12 with p-methoxybenzylamine, p-
chlorobenzylamine, and methoxyethylamine in EtOH
containing Et3N at 60 ꢁC. Intermediates 14–16 were ob-
tained in this way in 67–90% yields. Subsequent reaction
of 14 with isovaleramide, isobutyramide, acetoaceta-
mide, and p-methoxybenzamide as representative
amides using the Buchwald conditions led to formation
of purines 18b–e (57–82%). In the same way compounds
19e and 20d,e were obtained.
2. Chemistry
The objective initially set in our study was to determine
whether compound 12, available in four steps and high
yield from commercial 6-chloropurine,38–40 would react
in the desired manner under Pd(0)-catalyzed amidation
conditions to give the C-2 amide product. This reaction
was of particular interest as it would provide a means to
introduce an amine/amide type motif at C-2 in a 2,6-dih-
alopurine rather than at the more reactive C-6 position,
as is observed under SNAr conditions. The fact that this
intermediate reacts in Sonogashira,41 Stille,42 and Suzu-
ki43 type palladium-catalyzed reactions to regioselective-
ly give the C-2 cross-coupling products suggested that
this would be the case. In preliminary experiments, how-
ever, the reaction of purine 12 in THF with different
amides using Pd2(dba)3 as catalyst, Xantphos as the
ligand, and cesium carbonate as the base (Buchwald
conditions)30,31 led to the expected 2-mono-substituted
Returning to the idea of introducing the amide function
at C-2 in the first step, the 6-benzylsulfanyl purine deriv-
ative 1338 was reacted with n-butyramide and the four
other test amides under the Pd(0) catalysis conditions
to give compounds 17a-e in good to excellent yields
(65–98%). The interest in using compound 13 as the
starting material is that the C-6 S-benzyl substituent is
much less susceptible to displacement (SNAr) reactions
than is the chloro substituent in 12, and as the results
show, this motif is also not reactive in the cross-coupling
reactions. The other interesting attribute to the use of
compound 13 is that, as we44 and Schultz et al.45 inde-
pendently showed, the S-benzyl group can be activated
with respect to reaction with amine nucleophiles by
simple S-oxidation. Indeed, the corresponding sulfones
obtained by reacting intermediates 17a–c with m-CPBA

132
L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
underwent facile conversion to products 19a–c and 20a–
c upon reaction with the requisite amine in EtOH at
room temperature. In a similar way, compound 18a
was prepared in two steps from 17a in 67% overall yield.
However, a limiting feature which surfaced in this study
was that amides 17d and 17e were unstable toward the
treatment with m-CPBA during the S-oxidation step.
Perhaps with other oxidants and lower temperature con-
S
Cl
N
N
N
N
N
I
N
N
N
I
13
12
p-MeO-Bn-NH
2
Xantphos, Pd (dba) ,
2
3
p-Cl-Bn-NH or
2
Cs CO , THF, amide
2
3
MeO-(CH ) -NH
2 2
2
80˚C, 3h
EtOH,NEt , 60˚C
3
R
N
S
N
NH
N
O
(90%)
(67%)
(90%)
14 : R =
15 : R =
16 : R =
N
N
N
N
O
Cl
O
N
N
R
I
H
17 a-c
a: R = CH CH CH (82%)
2
2
3
1) m-CPBA, CH Cl RT
2
2,
b: R = CH CH(CH ) (96%)
2
3 2
2) p-MeO-Bn-NH
2
c: R = CH(CH ) (71%)
3 2
p-Cl-Bn-NH or
2
Xantphos, Pd (dba) ,
2
3
d: R = CH COCH
2
3
MeO-(CH ) -NH
Cs CO , THF, amide
2 2
2
2
3
e: R = p-methoxyphenyl
EtOH, RT
80˚C, 4h
O
HN
N
HN
N
HN
O
Cl
N
N
N
N
N
N
O
O
O
N
N
N
N
N
N
N
R
R
R
H
H
H
18
from 14-16: 18 b-e (57-82%)
from 17a-c: 18 a (67%), 19a-c (35-56%) or 20a-c (43-64%)
19
20
,
19 e (88%) or 20 d (57%), e (51%)
Scheme 1. Routes to 2-amidopurine derivatives 18–20.
Pd(PPh ) , CO bubbling, NEt , THF
3 4
3
14, 15 or 16
iso-butylamine, or iso-propylamine
50˚C, 2-3 h
O
HN
HN
HN
Cl
O
b: R = CH CH(CH )
N
N
N
N
N
2
3 2
N
N
N
c: R = CH(CH )
H
N
H
N
H
3 2
N
N
N
N
N
R
R
R
O
O
O
21 b (85%), c (77%)
22c (76%)
23b (95%), c 90%)
Scheme 2. Synthesis of amides 21–23.

L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
Table 1. Enzymatic evaluation (IC50, lM) on CDK1 and CDK5
133
ditions this will no longer be a problem for these and
other amide-containing derivatives which are of interest
for certain biological applications.
Compound
CDK1/cyclin B
CDK5/p25
18a
18b
18c
18d
18e
19a
19b
19c
19e
20a
20b
20c
20d
20e
21b
21c
22c
23b
23c
4.4
2.3
0.94
2.4
4.6
2.9
3
3.9
1.8
1.3
1.6
3.4
2.1
1.6
0.9
The Pd(0)-catalyzed amino carbonylation of aryl halides
proved to be particularly well adapted and direct meth-
od for the preparation of the corresponding inverted C-2
amides (Scheme 2). In the experiments, the reaction of
the 2-iodopurine intermediates 14, 15, and 16 with iso-
propylamine or isobutylamine and CO (atmospheric
pressure) in the presence of Pd(PPh3)4 (cat) led to the
formation of the mono-carbonylated compounds
21b,c, 22c, and 23b,c in a single step and in high yields.
1.2
40
19
10
6.6
13
9.6
7
7
>10
>10
2.4
2.3
1.7
7.2
8.3
NT
NT
2.1
2.4
2
As shown in Table 1 the new amide substituents at posi-
tion 2 did not improve the inhibitory activity, as com-
pared to other 2-iodo- or 2-pyrrolidine methanol
purine derivatives,46 but this structural modification is
not detrimental to the inhibitory activity. The best
inhibitors (18c, 19c, and 22c) bear a short amide chain
(isopropyl) at C2, and a p-methoxybenzylamino- or a
p-chlorobenzylamino- group at C6. They inhibit
CDK1 and CDK5 to a similar extent. In contrast, the
presence of a bulky p-methoxyphenyl substituent at C-
2 (18e, 19e, and 20e) decreases the anti-CDK activity.
The presence of the acyclic methoxyethyl-amino substi-
tuent at C-647 gave consistently less active inhibitors as
compared to the corresponding C-6 benzylamino deriv-
atives (20 less active than 18 or 19; 23 less active than 21
or 22). In addition, as the majority of non-purine inhib-
itors of CDK1/Cyclin B inhibit GSK-3b to a similar ex-
tent48 it was of interest to screen our compounds against
GSK3. As found for Roscovitine and Purvalanol no
inhibition of GSK3 was observed.48 As suggested by
the structure of N-9 methyl substituted purine com-
pound 3 (Scheme 1), this may simply be the conse-
quence of unfavorable interactions between the bulky
N-9 i-propyl group in our purine derivatives with the
gatekeeper residue and the hydrophobic 1 pocket. This
intriguing point requires further investigation.
16
13
4.2. Buffers
Homogenization buffer: 60 mM b-glycerophosphate,
15 mM p-nitrophenylphosphate, 25 mM Mops (pH
7.2), 15 mM EGTA, 15 mM MgCl2, 1 mM DTT,
1 mM sodium vanadate, 1 mM NaF, 1 mM phenylphos-
phate, 10 lg leupeptin/ml, 10 lg aprotinin/ml, 10 lg soy-
bean trypsin inhibitor/ml, and 100 lM benzamidine.
Bead buffer: 50 mM Tris, pH 7.4, 5 mM NaF, 250 mM
NaCl, 5 mM EDTA, 5 mM EGTA, 0.1% Nonidet
P-40, 10 lg leupeptin/ml, 10 lg aprotinin/ml, 10 lg
soybean trypsin inhibitor/ml, and 100 lM benzamidine.
Buffer A: 10 mM MgCl2, 1 mM EGTA, 1 mM DTT,
25 mM Tris–HCl, pH 7.5, and 50 lg heparin/ml.
Buffer C: homogenization buffer but 5 mM EGTA, no
NaF, and no protease inhibitors.
Tris-buffered saline–Tween 20 (TBST): 50 mM Tris, pH
7.4, 150 mM NaCl, and 0.1% Tween 20.
3. Biological results
See Table 1.
Hypotonic lysis buffer (HLB): 50 mM Tris–HCl, pH 7.4,
120 mM NaCl, 10% glycerol, 1% Nonidet-P40, 5 mM
DTT, 1 mM EGTA, 20 mM NaF, 1 mM orthovana-
date, 5 lM microcystin, and 100 lg/ml each of leupep-
tin, aprotinin, and pepstatin.
4. Experimental
4.1. Biochemical reagents
4.3. Kinase preparations and assays
Sodium orthovanadate, EGTA, EDTA, Mops, b-glycer-
ophosphate, phenylphosphate, sodium fluoride, dithio-
threitol (DTT), glutathione–agarose, glutathione,
bovine serum albumin (BSA), nitrophenylphosphate,
leupeptin, aprotinin, pepstatin, soybean trypsin inhibi-
tor, benzamidine, and histone H1 (type III-S) were
obtained from Sigma Chemicals. [c-33P]ATP was
obtained from Amersham. The GS-1 peptide
(YRRAAVPPSPSLSRHSSPHQSpEDEEE) was syn-
thesized by the Peptide Synthesis Unit, Institute of Bio-
molecular Sciences, University of Southampton,
Southampton SO16 7PX, U.K.
Kinase activities were assayed in Buffer A or C (unless
otherwise stated), at 30 ꢁC, at a final ATP concentration
of 15 lM. Blank values were subtracted and activities
calculated as pmoles of phosphate incorporated for a
10 min. incubation. The activities are usually expressed
in % of the maximal activity, that is, in the absence of
inhibitors. Controls were performed with appropriate
dilutions of dimethylsulfoxide. In a few cases phosphor-
ylation of the substrate was assessed by autoradiogra-
phy after SDS–PAGE.

134
L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
GSK-3b was purified from porcine brain.49 It was as-
sayed, following a 1/100 dilution in 1 mg BSA/ml of
10 mM DTT, with 5 ll of 40 lM GS-1 peptide as a sub-
strate, in buffer A, in the presence of 15 lM [c-33P] ATP
(3,000 Ci/mmol; 1 mCi/ml) in a final volume of 30 ll.
After 30 min incubation at 30 ꢁC, 25 ll aliquots of
supernatant were spotted onto 2.5 · 3 cm pieces of
Whatman P81 phosphocellulose paper, and, 20 s later,
the filters were washed five times (for at least 5 min each
time) in a solution of 10 ml phosphoric acid/liter of
water. The wet filters were counted in the presence of
1 ml ACS (Amersham) scintillation fluid.
To a solution of 6-benzylsulfanyl-2-iodo-9-(tetrahydro-
pyran-2-yl)-9H-purine (5.5 g, 12.1 mmol) described
above, in dry CH2Cl2 was added dropwise TFA 99%
(9 equiv, 109 mmol, 8 mL). The resultant solution was
stirred at room temperature for 10 min and turned deep
red. Then the solution was concentrated, the residue dis-
solved in EtOAc and washed with a saturated solution
of NaHCO3. The organic layers were combined, dried
on MgSO4, and concentrated, and the resultant solid
was washed with CH2Cl2 to afford the expected product
(2-iodo-6-benzylsulfanylpurine) as a white solid, 77%;
Rf: 0.45 (EtOAc/heptane 6:4); mp: 251 ꢁC. 1H NMR
(DMSO) d: 13.64 (br s, 1H, NH); 8.38 (s, 1H, H8);
7.50–7.22 (m, 5H ar); 4.56 (s, 2H, CH2S). 13C NMR
(DMSO) d: 159.4 (C6); 150.3 (C4); 143.1 (CH, C8);
137.6 (Cq ar); 130.0 (C5); 129.9 (2CH ar); 128.3 (2CH
ar); 127.2 (CH ar); 118.9 (C2); 32.2 (CH2S). MS (electro-
spray): m/z 759.1 [2M+Na]; 391.1 [M+Na]; 369.1 [M+H].
Anal. Calcd for C12H9IN4S: C, 39.15; H, 2.46; N, 15.22;
S, 8.71. Found: C, 38.91; H, 2.44; N, 15.11; S, 8.29.
CDK1/cyclin B was extracted in homogenization buffer
from M phase starfish (Marthasterias glacialis) oocytes
and purified by affinity chromatography on p9CKShs1-Se-
pharose beads, from which it was eluted by free p9CKShs1
as previously described.50,51 The kinase activity was as-
sayed in buffer C, with 1 mg histone H1/ml, in the presence
of 15 lM [c-33P] ATP (3000 Ci/mmol; 1 mCi/ml) in a final
volume of 30 ll. After 10 min. incubation at 30 ꢁC, 25 ll
aliquots of supernatant were spotted onto P81 phospho-
cellulose papers and treated as described above.
To a stirred solution of PPh3 (1.3 equiv, 17.7 mmol,
4.63 g) in dry THF (40 mL) under argon, cooled at
ꢀ50 ꢁC, was added dropwise DIAD (1.3 equiv,
17.7 mmol, 3.48 mL). The reaction mixture was stirred
for 10 min (a yellow precipitate appears). Then, isopropa-
nol (1.3 equiv, 17.7 mmol, 1.35 mL) was added. After stir-
ring at ꢀ50 ꢁC for 10 min, 2-iodo-6-benzylsulfanylpurine
(1 equiv, 13.6 mmol, 5 g) in a solution of dry THF
(20 mL) was added, and the resultant solution was stirred
at room temperature overnight. After concentration of
the reaction mixture, the resultant yellow oil was purified
by silica gel column chromatography (CH2Cl2) to afford
the expected product (13) as a slightly yellow solid, 80%;
Rf: 0.63 (CH2Cl2/EtOH 95:5); mp: 124 ꢁC. 1H NMR
(CDCl3) d: 7.89 (s, 1H, H8); 7.52 (d, 2H ar, J = 7.2 Hz);
7.50–7.22 (m, 3H ar); 4.84 (sept, 1H, CH-i-PrN,
J = 6.8 Hz); 4.57 (s, 2H, CH2Ph); 1.58 (d, 6H, 2CH3-i-
Pr, J = 6.8 Hz). 13C NMR (CDCl3) d: 161.3 (C6); 148.9
(C4); 140.0 (CH, C8); 137.2 (Cq ar); 131.1 (C5); 129.3
(2CH ar); 128.5 (2CH ar); 127.2 (CH ar); 118.0 (C2);
47.3 (CH-i-PrN); 33.4 (CH2S); 22.7 (2CH3-i-Pr). MS
(electrospray): m/z 433.1 [M+Na]; 411.1 [M+H]. Anal.
Calcd for C15H15IN4S: C, 43.91; H, 3.69; N, 13.66; S,
7.82. Found: C, 43.75; H, 3.64; N, 13.68; S, 7.71.
CDK5/p25 was reconstituted by mixing equal amounts
of recombinant mammalian CDK5 and p25 expressed
in E. coli as GST (glutathione-S-transferase) fusion pro-
teins and purified by affinity chromatography on gluta-
thione–agarose (vectors kindly provided by Dr. J.H.
Wang) (p25 is a truncated version of p35, the 35 kDa
CDK5 activator). Its activity was assayed in buffer C
as described for CDK1/cyclin B.
4.4. Chemistry
1H and 13C NMR spectra were recorded on a Bruker
AC300 spectrometer (300 and 75.3 MHz, respectively).
Mass spectra were recorded on a WATERS ZQ 2000
spectrometer with direct injection.
4.5. 6-Benzylsulfanyl-2-iodo-9-isopropyl-9H-purine (13)
To a stirred solution of 6-chloro-2-iodo-9-tetrahydro-
pyranepurine38 (5 g, 13.7 mmol) in ethanol (50 mL)
were added benzylmercaptan (2 equiv, 27.4 mmol,
3.2 mL) and triethylamine (2 equiv, 27.4 mmol,
3.8 mL). The reaction mixture was stirred at 60 ꢁC
for 10 min. Then the resultant white precipitate was
filtered and washed with absolute ethanol to afford
the expected product, 97%; Rf: 0.53 (EtOAc/heptane
4.6. (2-Iodo-9-isopropyl-9H-purin-6-yl)-(4-methoxyben-
zyl)-amine (14)
A
solution of 6-chloro-2-iodo-9-isopropylpurine
1
6:4); mp: 186–187 ꢁC. H NMR (CDCl3) d: 8.06 (s, 1H,
(12)38–40 (4 g, 12.4 mmol), triethylamine (1 equiv), and
p-methoxybenzylamine (1.5 equiv, 18.6 mmol, 2.42 mL)
in absolute ethanol (60 ml) was stirred for 18 h at
60 ꢁC. The mixture was evaporated to dryness and the
resulting solid was purified by flash chromatography
(CH2Cl2/EtOH: 95:5) to give 14 (3.8 g, 90%) as a white
solid after washing with pentane: Rf: 0.68 (CH2Cl2/
H8); 7.52–7.48 (m, 2H ar); 7.35–7.22 (m, 3H ar); 5.71
(dd, 1H, NCHO, J = 10.4 Hz, J0 = 2.1 Hz); 4.57 (s, 2H,
CH2S); 4.75 (dd, 1H, CHO, J = 10.0 Hz, J0 = 2.1 Hz);
4.14 (td, 1H, CHO, J = 11.5 Hz, J0 = 3.2 Hz); 1.94–1.63
(m, 6H, 3CH2). 13C NMR (CDCl3) d: 161.6 (C6); 148.4
(C4); 140.3 (CH, C8); 137.2 (Cq ar); 131.0 (C5); 129.5
(2CH ar); 128.4 (2CH ar); 127.4 (CH ar); 118.4 (C2);
81.8 (NCHO a); 68.8 (CH2O e); 33.3 (CH2S); 32.2 (CH2
b); 24.8 (CH2 d); 22.6 (CH2 c). MS (IC/NH3): m/z 453
[M+H]. Anal. Calcd for C17H17IN4OS: C, 45.14; H,
3.79; N, 12.39; S, 7.09. Found: C, 44.81; H, 3.71; N,
12.14; S, 7.21.
1
EtOH 98:2); mp: 165 ꢁC. H NMR (CDCl3) d: 7.67 (s,
1H, H8); 7.31 (d, 2H ar, J = 8.5 Hz); 6.88 (d, 2H ar,
J = 8.5 Hz); 6.00 (br s, 1H, NH); 4.82 (m, 1H, CH-i-
PrN, J = 6.8 Hz); 4.72 (br s, 2H, CH2N); 3.81 (s, 3H,
CH3O); 1.56 (d, 6H, 2CH3-i-Pr, J = 6.8 Hz). 13C NMR
(CDCl3) d: 159.1 (Cq ar-OMe); 153.9 (C4); 149.2 (C6);

L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
135
136.9 (CH, C8); 130.1 (Cq ar); 120.2 (C5); 114.2 (C2);
114.0 (4CH ar); 55.3 (CH3O); 46.8 (CH-i-PrN); 44.2
(CH2N); 22.8 (2CH3-i-Pr). MS (electrospray): m/z 424
(100%) [M+H]; 316 (29%) [MꢀCH2OPh]; HRMS calcd
for C16H18IN5O: m/z [M+H], 424.0629, Found
424.0628. Anal. Calcd for C16H18IN5O: C, 45.40; H,
4.29; N, 16.55. Found: C, 45.69; H, 4.37; N, 16.87.
ford the expected product as a white solid: 739 mg, 82%.
Rf: 0.31 (CH2Cl2/EtOH 98:2). Mp: 118 ꢁC. H NMR
1
(CDCl3) d: 7.96 (br s, 1H, NHCO); 7.89 (s, 1H, H8);
7.44 (d, 2H ar, J = 7.0 Hz); 7.34–7.22 (m, 3H ar); 4.76
(sept, 1H, CH-i-PrN, J = 6.8 Hz); 4.59 (s, 2H, CH2S);
2.89 (t, 2H, CH2 a, J = 7.4 Hz); 1.80 (sext, 2H, CH2 b,
J = 7.4 Hz); 1.61 (d, 6H, 2CH3-i-Pr, J = 6.8 Hz); 1.03
(t, 3H, CH3 c, J = 7.4 Hz). 13C NMR (CDCl3) d: 173.4
(CO); 161.4 (C6); 151.6 (C2); 149.1 (C4); 139.9 (CH,
C8); 137.2 (C5); 129.0 (2CH ar); 128.5 (2CH ar); 128.1
(Cq ar); 127.3 (CH ar); 47.5 (CH-i-PrN); 39.2 (CH2 a);
32.9 (CH2S); 22.4 (2CH3-i-Pr); 18.3 (CH2 b); 13.9
(CH3 c). MS (electrospray): m/z 392 (17%) [M+Na];
371 (24%) [M+2H]; 370 (100%) [M+H]. HRMS calcd
for C19H23N5OSN: m/z 370.1696 [M+H]. Found:
370.1704.
4.7. (4-Chlorobenzyl)-(2-iodo-9-isopropyl-9H-purin-6-yl)-
amine (15)
A solution of 6-chloro-2-iodo-9-isopropylpurine (12)
(500 mg, 1.55 mmol) in absolute ethanol (20 mL) was
stirred at 60 ꢁC for 2 days in the presence of triethyl-
amine (1 equiv, 1.55 mmol, 216 lL), p-chlorobenzyl-
amine (2 equiv, 3.1 mmol, 378 lL). After concentration
in vacuo, the oily residue was purified by silica gel col-
umn chromatography, eluting with CH2Cl2/EtOH
(100:0–98:2) to give 15 as a white solid after washing
with heptane, 67%; Rf: 0.44 (CH2Cl2/EtOH 98:2); mp:
4.10. N-(6-Benzylsulfanyl-9-isopropyl-9H-purin-2-yl)-3-
methyl-butyramide (17b)
1
116 ꢁC; H NMR (CDCl3): d: 7.59 (s, 1H, H8); 7.33
In the same conditions as for the preparation of 17a, the 3-
methylbutyramide derivative 17b was obtained from 13 as
a slightly orange solid, 96%. Rf: 0.29 (CH2Cl2/EtOH
98:2). Mp: 97 ꢁC. 1H NMR (CDCl3) d: 8.41 (s, 1H,
NHCO); 7.92 (s, 1H, H8); 7.45–7.21 (m, 5H ar); 4.77 (sept,
1H, CH-i-PrN, J = 6.8 Hz); 4.59 (s, 2H, CH2S); 2.78 (d,
2H, CH2CO, J = 6.9 Hz); 1.60 (d, 6H, 2CH3-i-PrN,
J = 6.8 Hz); 1.04 (d, 6H, 2CH3-i-PrCH2, J = 6.6 Hz).
13C NMR (CDCl3) d: 172.7 (CO); 161.4 (C6); 151.6
(C2); 149.1 (C4); 139.9 (CH, C8); 137.2 (Cq ar); 129.0
(2CH ar); 128.5 (2CH ar); 128.1 (C5); 127.3 (CH ar);
47.4 (CH-i-PrN); 46.2 (CH2, CH2CO); 32.9 (CH2S);
25.3 (CH-i-Pr); 22.6 (2CH3-i-PrN); 22.4 (2CH3-i-Pr).
MS (electrospray): m/z 406 (100%) [M+Na]; 384 (39%)
[M+H]. HRMS calcd for C20H25N5OS: m/z 406.1672
[M+Na]. Found: 406.1682.
(d, 2H ar, J = 8.4 Hz); 7.25 (d, 2H ar, J = 8.4 Hz); 4.94
(m, 2H, CH2N, J = 6.2 Hz); 4.76 (sept, 1H, CH-i-PrN,
J = 6.8 Hz); 1.52 (d, 6H, 2CH3-i-Pr, J = 6.8 Hz). 13C
NMR (CDCl3) d: 156.2 (C4); 148.0 (C6); 137.2 (CH,
C8); 133.4 (Cq ar); 129.4 (Cq ar); 128.8 (4CH ar);
120.4 (C5); 116.0 (C2); 46.9 (CH-i-PrN); 43.5 (CH2N);
22.8 (2CH3-i-Pr). MS (electrospray): m/z 428 (100%)
[M+H]; m/z 301 (25%) [MꢀI]. HRMS calcd for
C15H15ClIN5: m/z [M+H], 428.0133. Found: 428.0135.
4.8. (2-Iodo-9-isopropyl-9H-purin-6-yl)-(methoxyethyl)-
amine (16)
A solution of 12 (500 mg, 1.55 mmol) in absolute etha-
nol (20 mL) was stirred at 60 ꢁC for 2 days in the pres-
ence of triethylamine (1 equiv, 1.55 mmol, 216 lL), 2-
methoxyethylamine (2 equiv, 3.1 mmol, 404 lL). After
concentration in vacuo, the crude yellow solid was
washed with pentane to give 16 as a white solid, 90%;
Rf: 0.42 (CH2Cl2/EtOH 98:2); mp: 112 ꢁC. 1H NMR
(CDCl3) d: 7.70 (s, 1H, H8); 6.16 (br s, NH); 4.80 (sept,
1H, CH-i-PrN, J = 6.8 Hz); 3.80 (br s, 2H, CH2N); 3.59
(t, 2H, CH2O, J = 5.1 Hz); 3.38 (s, 3H, CH3O); 1.55 (d,
6H, 2CH3-i-Pr, J = 6.8 Hz). 13C NMR (CDCl3) d: 154.1
(C4); 149.1 (C6); 137.0 (CH, C8); 120.1 (C5); 119.7 (C2);
71.0 (CH2O); 58.7 (CH3O); 46.7 (CH-i-PrN); 40.3
(CH2N); 22.8 (2CH3-i-Pr). MS (electrospray): m/z 362
(100%) [M+H]; 330 (25%) [M+H–CH3O]; 320 (39%)
[Mꢀi-Pr]. HRMS calcd for C11H16IN5O: m/z [M+H]
362.0472. Found: 362.0479.
4.11. N-(6-Benzylsulfanyl-9-isopropyl-9H-purin-2-yl)-
isobutyramide (17c)
In the same conditions as for the preparation of 17a, the
isobutyramide derivative 17c was obtained from 13 as a
white solid, 71%. Rf: 0.34 (CH2Cl2/EtOH 98:2). Mp:
1
124 ꢁC. H NMR (CDCl3) d: 8.13 (br s, 1H, NHCO);
7.90 (s, 1H, H8); 7.45 (d, 2H ar, J = 6.9 Hz); 7.34–7.22
(m, 3H ar); 4.78 (sept, 1H, CH-i-PrN, J = 6.8 Hz);
4.60 (s, 2H, CH2S); 2.04 (br s, 1H, CHCO); 1.60 (d,
6H, 2CH3-i-PrN, J = 6.8 Hz); 1.29 (d, 6H, 2CH3-i-
PrCO, J = 6.8 Hz). 13C NMR (CDCl3) d: 161.3 (C6);
151.5 (C2); 149.2 (C4); 139.9 (CH, C8); 137.2 (Cq ar);
129.0 (2CH ar); 128.5 (2CH ar); 128.2 (C5); 127.3 (CH
ar); 47.4 (CH-i-PrN); 35.3 (CHCO); 32.9 (CH2S); 22.5
(2CH3-i-PrN); 19.3 (2CH3-i-Pr). MS (electrospray):
m/z 392 (10%) [M+Na]; 370 (100%) [M+H] HRMS
calcd for C19H23N5OS: m/z 370.1696 [M+H]. Found:
370.1706.
4.9. N-(6-Benzylsulfanyl-9-isopropyl-9H-purin-2-yl)-
butyramide (17a)
A mixture of 2-iodopurine 13 (1 g, 2.44 mmol), Cs2CO3
(3 equiv, 7.32 mmol, 2.38 g), butyramide (2 equiv,
4.88 mmol, 425 mg), Pd2(dba)3 (0.02 equiv, 0.05 mmol,
45 mg), and XantPhos (0.03 equiv, 0.07 mmol, 42 mg)
in dry and degassed THF (23 mL) was stirred at 80 ꢁC
for 3 h. The solution was concentrated, and, after the
usual work up, the red oil was purified by silica gel col-
umn chromatography (CH2Cl2/EtOH 1:0 to 95:5) to af-
4.12. N-[9-Isopropyl-6-(4-methoxy-benzylamino)-9H-
purin-2-yl]-butyramide (18a)
A solution of 17a (664 mg, 1.79 mmol) and 3 equiv of
m-CPBA (621 mg, 3.59 mmol) in dry CH2Cl2 (10 ml)
was stirred at room temperature for 2 h. After addition

136
L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
of water (2 ml), the organic layer was separated, dried
(MgSO4), concentrated, and purified by silica gel col-
umn chromatography eluting with CH2Cl2 followed by
CH2Cl2/EtOH 95:5 to afford N-(9-isopropyl-6-phen-
2H ar, J = 8.7 Hz); 7.06 (br s, 1H, NH); 6.84 (d, 2H
ar, J = 8.6 Hz); 4.73–4.62 (m, 3H, PhCH2N and CH-i-
PrN); 3.79 (s, 3H, OCH3); 2.82 (br d, 2H, CH2CO,
J = 5.2 Hz); 2.28 (sept, 1H, CH-i-Pr, J = 6.7 Hz); 1.54
(d, 6H, 2CH3-i-PrN, J = 6.8 Hz); 1.00 (d, 6H, 2CH3-i-
Pr, J = 6.6 Hz). 13C NMR (CDCl3) d: 173.6 (CO);
158.8 (Cq ar-OMe); 154.8 (C4); 152.7 (C2); 149.6 (C6);
136.7 (CH, C8); 130.7 (Cq ar); 128.8 (2CH ar); 116.7
(C5); 113.8 (2CH ar OMe); 55.1 (CH3O); 46.8 (CH-i-
PrN); 45.8 (CH2 a); 43.7 (CH2N); 25.2 (CH-i-Pr); 22.6
(2CH3-i-PrN); 22.4 (2CH3-i-Pr). MS (electrospray):
m/z 419 (18%) [M+Na]; 397 (100%) [M+H]. HRMS
calcd for C21H28N6O2: m/z 397.2349 [M+H]. Found
397.2347. Anal. Calcd for C21H28N6O2: C, 63.62; H,
7.12; N, 21.20. Found: C, 63.71; H, 7.14; N, 21.13.
ylmethanesulfonyl-9H-purin-2-yl)-butyramide as
a
white solid: 504 mg, 70%. Rf: 0.64 (CH2Cl2/EtOH
95:5). Mp: 116 ꢁC. 1H NMR (CDCl3) d: 8.48 (br s,
1H, NHCO); 8.28 (s, 1H, H8); 7.45–7.22 (m, 5H ar);
4.95 (m, 1H, CH-i-PrN); 4.91 (s, 2H, CH2S); 2.70 (t,
2H, CH2 a, J = 7.3 Hz); 1.80 (sext, 2H, CH2 b,
J = 7.4 Hz); 1.67 (d, 6H, 2CH3-i-Pr, J = 6.8 Hz); 1.04
(t, 3H, CH3 c, J = 7.3 Hz). 13C NMR (CDCl3) d: 172.8
(CO); 155.2 (C2); 151.5 (C4); 145.1 (CH, C8); 131.2
(2CH ar); 129.0 (CH ar); 128.8 (2CH ar); 126.9 (C6);
126.4 (C5); 59.7 (CH2S); 48.3 (CH-i-Pr); 39.4 (CH2 a);
22.4 (2CH3-i-Pr); 18.3 (CH2 b); 13.8 (CH3 c). MS (elec-
trospray): m/z 424 (100%) [M+Na]; 402 (12%) [M+H].
HRMS calcd for C19H23N5O3S: m/z 424.1414 [M+Na].
Found: 424.1418. It was used without further purifica-
tion in the next step.
4.14. N-[9-Isopropyl-6-(4-methoxy-benzylamino)-9H-purin-
2-yl]-isobutyramide (18c)
Compound 18c was prepared from 2-iodopurine deriva-
tive 14 (200 mg, 0.47 mmol), and isobutyramide
(2 equiv, 0.94 mmol 82 mg). See preparation of 18b for
details. After stirring at 80 ꢁC for 3 h and work up, a yel-
low solid was obtained, 140 mg, 77%. Rf: 0.26 (CH2Cl2/
A solution of the preceding 6-benzylsulfonepurine
(190 mg, 0.47 mmol), 4-methoxybenzylamine (1.5 equiv,
0.94 mmol, 124 lL) in absolute ethanol (10 mL) was
stirred at room temperature for 1 h. After evaporation
to dryness, the crude solid was purified by silica gel col-
umn chromatography (CH2Cl2/EtOH 1:0–98:2) to af-
ford the expected product (18a) as a white solid:
172 mg, 95%. Rf: 0.28 (CH2Cl2/EtOH 98:2). Mp:
1
EtOH 98:2). Mp: 104 ꢁC. H NMR (CDCl3) d: 8.18 (br
s, 1H, NHCO); 7.52 (s, 1H, H8); 7.27 (d, 2H ar,
J = 8.7 Hz); 6.93 (br s, 1H, NH); 6.84 (d, 2H ar,
J = 8.7 Hz); 4.74–4.65 (m, 3H, PhCH2N and CH-i-
PrN); 3.79 (s, 3H, OCH3); 3.45 (br s, 1H, CHCO);
1.54 (d, 6H, 2CH3-i-PrN, J = 6.8 Hz); 1.25 (d, 6H,
2CH3-i-Pr, J = 6.8 Hz). 13C NMR (CDCl3) d: 177.6
(CO); 158.8 (Cq ar OMe); 154.8 (C4); 152.6 (C2);
149.7 (C6); 136.8 (CH, C8); 129.8 (Cq ar); 128.8 (2CH
ar); 116.8 (C5); 113.9 (2CH ar OMe); 58.0 (CH3O);
46.8 (CH-i-PrN); 43.8 (CH2N); 34.5 (CH, CHCO);
22.5 (2CH3-i-PrN); 19.2 (2CH3-i-Pr). MS (electrospray):
m/z 405 (22%) [M+Na]; 383 (100%) [M+H]. HRMS
calcd for C20H26N6O2: m/z 383.2202 [M+Na]. Found
383.2190. Anal. Calcd for C20H26N6O2: C, 62.81; H,
6.85; N, 21.97. Found: C, 62.43; H, 6.67; N, 21.41.
1
115 ꢁC. H NMR (CDCl3) d: 7.81 (br s, 1H, NHCO);
7.66 (s, 1H, H8); 7.30 (d, 2H ar); 6.87 (d, 2H ar,
J = 8.4 Hz); 6.10 (br s, 1H, NH); 4.80–4.65 (m, 3H,
CH2N and CH-i-PrN); 3.80 (s, 3H); 2.91 (br t, 2H,
CH2 a); 1.78 (sext, 2H, CH2 b, J = 7.4 Hz); 1.58 (d,
6H, 2CH3-i-Pr, J = 6.7 Hz); 1.01 (t, 3H, CH3 c,
J = 7.4 Hz). 13C NMR (CDCl3) d: 174.7 (CO); 159.0
(Cq ar); 154.7 (C4); 152.7 (C2); 150.0 (C6); 136.8 (CH,
C8); 130.5 (Cq ar); 129.0 (2CH ar); 116.9 (C5); 114.0
(2CH ar OMe); 55.3 (CH3O); 47.1 (CH-i-PrN); 42.6
(CH2N); 39.0 (CH2 a); 22.5 (2CH3-i-Pr); 18.4 (CH2 b);
13.9 (CH3 c). MS (electrospray): m/z 384 (24%)
[M+2H]; 383 (100%) [M+H]. HRMS calcd for
C20H26N6O2: m/z [M+H] 383.2195. Found: 383.2190.
Anal. Calcd for C20H26N6O2: C, 62.81; H, 6.85; N,
21.97. Found: C, 62.55; H, 6.64; N, 21.53.
4.15. N-[9-Isopropyl-6-(4-methoxy-benzylamino)-9H-purin-
2-yl]-3-oxo-butyramide (18d)
Compound 18d was prepared from 2-iodopurine deriva-
tive 14 (200 mg, 0.47 mmol) and acetoacetamide
(2 equiv, 0.94 mmol, 95 mg). See preparation of 18b
for details. After the usual work up, the red oil was puri-
fied by silica gel column chromatography (CH2Cl2/
EtOH 1:0–98:2) to afford the expected product as a yel-
low solid: 106 mg, 57%. Rf: 0.28 (CH2Cl2/EtOH 98:2).
Mp: 158 ꢁC. 1H NMR (CDCl3) d: 8.38 (br s, 1H,
NHCO); 7.72 (s, 1H, H8); 6.26 (br s, 1H, NH); 4.67
(sept, 1H, CH-i-PrN, J = 6.8 Hz); 4.11 (s, 2H, CH2CO);
3.75 (br s, 2H, CH2N); 3.59 (t, 2H, CH2O, J = 5.1 Hz);
3.38 (s, 3H, CH3O); 2.30 (s, 3H, CH3CO); 1.55 (d, 6H,
2CH3-i-Pr, J = 6.8 Hz). 13C NMR (CDCl3) d: 205.0
(CO); 171.9 (CONH); 155.0 (C4); 152.0 (C2); 136.8
(CH, C8); 117.1 (C5); 71.0 (CH2O); 58.8 (CH3O); 52.5
(CH2CO); 46.8 (CH-i-Pr); 40.5 (CH2N); 30.1 (CH3CO);
22.6 (2CH3-i-Pr). MS (electrospray): m/z 357 (42%)
[M+Na]; 335 (100%) [M+H]. HRMS calcd for
C15H22N6O3: m/z 335.1838 [M+H]. Found: 335.1826.
4.13. N-[9-Isopropyl-6-(4-methoxy-benzylamino)-9H-purin-
2-yl]-3-methyl-butyramide (18b)
A mixture of 2-iodopurine derivative 14 (100 mg,
0.24 mmol), Cs2CO3 (3 equiv, 0.72 mmol, 234 mg),
isovaleramide (2 equiv, 0.48 mmol, 48 mg), Pd2(dba)3
(0.02 equiv, 0.005 mmol, 4.4 mg), and XantPhos
(0.03 equiv, 0.007 mmol, 4 mg) in THF (12 mL) was stir-
red at 80 ꢁC for 4 h. After concentration, the residue was
dissolved in CH2Cl2 and washed twice with an aqueous
saturated solution of NaHCO3. The organic layers were
combined, dried (MgSO4), and evaporated in vacuo.
The red oil was purified by silica gel column chromatog-
raphy (CH2Cl2/EtOH 100:0–98:2) to afford the expected
product (18b) as a yellow solid: 65 mg, 70%. Rf: 0.46
1
(CH2Cl2/EtOH 98:2). Mp: 145 ꢁC. H NMR (CDCl3)
d: 8.32 (br s, 1H, NHCO); 7.53 (s, 1H, H8); 7.27 (d,

L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
137
Anal. Calcd for C15H22N6O3: C, 53.88; H, 6.63; N,
25.13. Found: C, 54.14; H, 6.62; N, 24.96.
1H, NHCO); 8.27 (s, 1H, H8); 7.37–7.22 (m, 5H ar);
4.98–4.88 (m, 1H, CH-i-PrN); 4.93 (s, 2H, CH2S); 2.57
(d, 2H, CH2CO, J = 7.1 Hz); 2.26 (sept, 1H, CH-i-Pr,
J = 6.7 Hz); 1.65 (d, 6H, CH3-i-PrN, J = 6.8 Hz); 1.03
(d, 6H, 2CH3-i-Pr, J = 6.6 Hz). 13C NMR (CDCl3) d:
176.2 (CO); 153.3 (C2); 149.4 (C4); 147.5 (CH, C8);
130.0 (2CH ar); 129.7 (CH ar); 129.0 (2CH ar); 127.9
(C6); 126.3 (C5); 69.6 (CH2S); 49.6 (CH-i-PrN); 45.8
(CH2CO); 25.8 (CH-i-Pr); 22.3 (2CH3-i-PrN); 22.1
(2CH3-i-Pr). It was used without further purification in
the next step. Substitution of the 6-benzylsulfonyl group
was achieved on 130 mg (0.313 mmol) with 4-chloroben-
zylamine (1.5 equiv, 0.469 mmol, 57 lL) in absolute eth-
anol (3 mL). See the preparation of 18a for details.
Work up and purification by silica gel column chroma-
tography (CH2Cl2) gave the expected product (19b) as a
beige solid: 100 mg, 80%. Rf: 0.30 (CH2Cl2/EtOH 98:2).
Mp: 160 ꢁC. 1H NMR (CDCl3) d: 7.83 (br s, 1H,
NHCO); 7.66 (s, 1H, H8); 7.29 (s, 4H ar); 6.30 (br s,
1H, NH); 4.76 (br s, 2H, CH2N); 4.71 (sept, 1H, CH-
i-PrN, J = 6.8 Hz); 2.77 (d, 2H, CH2CO, J = 6.2 Hz);
2.26 (sept, 1H, CH-i-Pr, J = 6.7 Hz); 1.58 (d, 6H,
2CH3-i-PrN, J = 6.8 Hz); 0.99 (d, 6H, 2CH3-i-Pr,
J = 6.6 Hz). 13C NMR (CDCl3) d: 173.6 (CO); 154.8
(C4); 152.7 (C2); 149.6 (C6); 137.6 (Cq ar); 136.9 (CH,
C8); 132.9 (Cq ar); 128.8 (2CH ar); 128.5 (2CH ar);
116.7 (C5); 46.9 (CH-i-PrN); 45.8 (CH2 a); 43.5
(CH2N); 25.1 (CH i-Pr); 22.5 (2CH3-i-PrN); 22.4
(2CH3-i-Pr). MS (electrospray): m/z 423 (15%)
[M+Na]; 401 (100%) [M+H]. HRMS calcd for
C20H25ClN6O: m/z 401.1856 [M+H]. Found: 401.1851.
Anal. Calcd for C20H25ClN6O: C, 59.92; H, 6.29; N,
20.96. Found: C, 59.71; H, 6.28; N, 20.66.
4.16. N-[9-Isopropyl-6-(4-methoxy-benzylamino)-9H-
purin-2-yl]-4-methoxy-benzamide (18e)
Compound 18e was prepared from 2-iodopurine deriva-
tive 14 (300 mg, 0.709 mmol), and p-methoxybenzamide
(2 equiv, 1.42 mmol 214 mg). See preparation of 18b for
details. After the usual work up, the red oil was purified
by silica gel column chromatography (CH2Cl2/EtOH
100:0–98:2) to afford 18e as a white solid: 259.5 mg,
82%. Rf: 0.36 (CH2Cl2/EtOH 98:2). Mp: 123 ꢁC. 1H
NMR (CDCl3) d: 8.56 (s, 1H, NHCO); 7.90 (d, 2H ar,
J = 8.7 Hz); 7.56 (s, 1H, H8); 7.30 (d, 2H0 ar,
J = 8.5 Hz); 6.94 (d, 2H ar, J = 8.8 Hz); 6.85 (d, 2H0ar,
J = 8.5 Hz); 6.10 (br s, 1H, NH); 4.86–4.68 (m, 3H,
CH2N and CH-i-PrN); 3.86 (s, 3H, CH3O); 3.78 (s,
3H, CH3O); 1.55 (d, 6H, 2CH3-i-Pr, J = 6.8 Hz). 13C
NMR (CDCl3) d: 162.6 (CO); 159.0 (Cq ar OMe);
154.8 (C4); 152.8 (C2); 151.0 (C6); 136.9 (CH, C8);
130.6 (Cq ar); 129.4 (2CH ar); 129.2 (2CH ar); 117.2
(C5); 114.0 (2CH ar); 113.8 (2CH ar); 55.4 (OMe);
55.3 (OMe); 46.7 (CH-i-PrN); 22.8 (2CH3-i-Pr). MS
(electrospray): m/z 469 (100%) [M+Na]; 447 (34%)
[M+H]. HRMS calcd for C24H26N6O3: m/z 469.1967
[M+Na]. Found 469.1959. Anal. Calcd for
C24H26N6O3: C, 64.56; H, 5.87; N, 18.82. Found: C,
64.31; H, 6.03; N, 18.61.
4.17. N-[6-(4-Chlorobenzylamino)-9-isopropyl-9H-purin-2-
yl]-butyramide (19a)
Compound 19a was prepared from 17a (see preparation
of 18a for conditions) (150 mg, 0.374 mmol) and 4-chlo-
robenzylamine (1.5 equiv, 0.560 mmol, 68 lL) in abso-
lute ethanol (5 mL). Work up and purification by
silica gel column chromatography (CH2Cl2/EtOH
100:0–95:5) gave the expected product (19a) as a white
solid: 70 mg, 49%. Rf: 0.56 (CH2Cl2/EtOH 95:5). Mp:
4.19. N-[6-(4-Chloro-benzylamino)-9-isopropyl-9H-purin-
2-yl]-isobutyramide (19c)
Compound 19c was prepared from 17c which was oxi-
dized to the 6-benzylsulfone derivative which was ob-
tained as an oil in 98% yield (213 mg) in the same
conditions as 19a. Rf: 0.28 (CH2Cl2/EtOH 98:2). Mp:
1
167 ꢁC. H NMR (CDCl3) d: 8.48 (br s, 1H, NHCO);
1
7.60 (s, 1H, H8); 7.30 (s, 4H ar); 4.75 (br s, 1H, NH);
4.68 (sept, 1H, CH-i-PrN, J = 6.8 Hz); 3.84 (br s, 2H,
CH2N); 2.87 (t, 2H, CH2 a, J = 7.2 Hz); 1.75 (sext,
2H, CH2 b, J = 7.4 Hz); 1.56 (d, 6H, 2CH3-i-Pr,
J = 6.8 Hz); 0.99 (t, 3H, CH3 c, J = 7.4 Hz). 13C NMR
(CDCl3) d: 174.2 (CO); 154.7 (C4); 152.6 (C2); 137.0
(CH, C8); 133.2 (Cq ar); 128.9 (2CH ar); 128.8 (2CH
ar); 128.6 (Cq ar); 117.4 (C5); 47.1 (CH-i-PrN); 43.7
(CH2N); 39.0 (CH2 a); 22.5 (2CH3-i-Pr); 18.4 (CH2 b);
13.9 (CH3 c). MS (electrospray): m/z 409 (13%)
[M+Na]; 387 (100%) [M+H] HRMS calcd for
C19H23ClN6O: m/z 387.1705 [M+H]. Found: 387.1695.
Anal. Calcd for C19H23ClN6O: C, 58.99; H, 5.99; N,
21.72. Found: C, 58.81; H, 6.09; N, 21.45.
64 ꢁC. H NMR (CDCl3) d: 8.80 (br s, 1H, NHCO);
8.32 (s, 1H, H8); 7.37–7.22 (m, 5H ar); 4.95 (br sept,
1H, CH-i-PrN, J = 6.8 Hz); 4.92 (s, 2H, CH2S); 2.94
(quint, 1H, CHCO, J = 6.7 Hz); 1.64 (d, 6H, 2CH3-i-
PrN, J = 6.8 Hz); 1.28 (d, 6H, 2CH3-i-Pr, J = 6.8 Hz).
13C NMR (CDCl3) d: 176.1 (CO); 155.1 (C2); 151.7
(C4); 145.5 (CH, C8); 134.4 (C5); 131.5 (2CH ar);
130.4 (CH ar); 128.9 (2CH ar); 126.6 (C6); 126.2 (C5);
59.6 (CH2S); 48.2 (CH-i-PrN); 35.9 (CH, CHCO); 22.3
(2CH3-i-PrN); 18.8 (2CH3-i-Pr). It was used without fur-
ther purification in the next step.
Sulfonyl substitution was carried out on 200 mg
(0.498 mmol) of the above sulfone and 4-chlorobenzyl-
amine (1.5 equiv, 0.747 mmol, 91 lL) in absolute etha-
nol (5 mL). See the preparation of 18a for details.
Work up and purification by silica gel column chroma-
tography (CH2Cl2/EtOH 100:0–95:5) gave the expected
product (19c) as a white solid: 105 mg, 55%. Rf: 0.25
(CH2Cl2/EtOH 98:2). Mp: 158–159 ꢁC. 1H NMR
(CDCl3) d: 8.13 (br s, 1H, NHCO); 7.61 (s, 1H, H8);
7.28 (s, 4H ar); 7.04 (br s, 1H, NH); 4.76 (br s, 2H,
4.18. N-[6-(4-Chloro-benzylamino)-9-isopropyl-9H-purin-
2-yl]-3-methyl-butyramide (19b)
Compound 19b was prepared from 17b which was oxi-
dized to the 6-benzylsulfone-purine derivative in 66%
yield (573 mg) in the same conditions as 19a. Rf: 0.28
1
(CH2Cl2/EtOH 98:2). H NMR (CDCl3) d: 8.68 (br s,

138
L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
CH2N); 4.74 (sept, 1H, CH-i-PrN, J = 6.8 Hz); 3.70 (q,
1H, CHCO, J = 7.0 Hz); 1.55 (d, 6H, 2CH3-i-PrN,
J = 6.8 Hz); 1.23 (d, 6H, 2CH3-i-Pr, J = 7.4 Hz). 13C
NMR (CDCl3) d: 177.4 (CO); 154.7 (C4); 152.6 (C2);
149.9 (C6); 137.2 (Cq ar); 136.9 (CH, C8); 133.1 (Cq
ar); 128.9 (2CH ar); 128.7 (2CH ar); 116.8 (C5); 47.0
(CH-i-PrN); 43.8 (CH2N); 34.7 (CH, CHCO); 22.6
(2CH3-i-PrN); 22.3 (2CH3-i-Pr). MS (electrospray):
m/z 409 (11%) [M+Na]; 387 (100%) [M+H]. HRMS
calcd for C19H23ClN6O: m/z 387.1706 [M+H]. Found:
387.1695. Anal. Calcd for C19H23ClN6O: C, 58.99; H,
5.99; N, 21.72. Found: C, 59.22; H, 6.02; N, 21.29.
4.22. N-[9-Isopropyl-6-(methoxy-ethylamino)-9H-purin-2-
yl]-3-methyl-butyramide (20b)
Compound 20b was prepared from 17b (100 mg,
0.240 mmol) which was oxidized to the 6-benzylsulf-
one-purine derivative and subsequently substituted with
2-methoxyethylamine (1.5 equiv, 0.361 mmol, 32 lL) in
absolute ethanol (2 mL). See the preparation of 18a
for details. Work up and purification by silica gel col-
umn chromatography (CH2Cl2/EtOH 100:0–95:5) gave
the expected product as a white solid: 73 mg, 90%. Rf:
0.09 (CH2Cl2/EtOH 98:2). Mp: 165 ꢁC. 1H NMR
(CDCl3) d: 8.05 (br s, 1H, NHCO); 7.73 (s, 1H, H8);
6.47 (br s, 1H, NH); 4.70 (sept, 1H, CH-i-PrN,
J = 6.7 Hz); 3.73 (br s, 2H, CH2N); 3.59 (t, 2H, CH2O,
J = 5.0 Hz); 3.37 (s, 3H, CH3O); 2.79 (br s, 2H,
CH2CO); 2.27 (sept, 1H, CH-i-Pr, J = 6.7 Hz); 1.57 (d,
6H, 2CH3-i-PrN, J = 6.7 Hz); 1.01 (d, 6H, 2CH3-i-Pr,
J = 6.6 Hz). 13C NMR (CDCl3) d: 173.3 (CO); 154.9
(C4); 152.5 (C2); 149.7 (C6); 136.8 (CH, C8); 116.9
(C5); 71.1 (CH2O); 58.8 (CH3O); 46.9 (CH-i-PrN);
45.9 (CH2CO); 40.4 (CH2N); 25.3 (CH-i-Pr); 22.6
(2CH3-i-PrN); 22.4 (2CH3-i-Pr). MS (electrospray): m/
4.20. N-[6-(4-Chloro-benzylamino)-9-isopropyl-9H-purin-
2-yl]-4- methoxy-benzamide (19e)
Compound 19e was prepared from 2-iodopurine deriva-
tive 15e (200 mg, 0.498 mmol) and p-methoxybenzamide
(2 equiv, 0.996 mmol, 150 mg) in THF (8 mL). See the
preparation of 18b for details. Work up and purification
by silica gel column chromatography (CH2Cl2/EtOH:
100:0–98:2) gave the expected product as a yellowish sol-
id: 185 mg, 88%. Rf: 0.16 (CH2Cl2/EtOH 98:2). Mp:
1
102 ꢁC. H NMR (CDCl3) d: 8.45 (br s, 1H, NHCO);
z
357 [M+Na]; 335 [M+H]. Anal. Calcd for
7.88 (d, 2H ar, J = 8.7 Hz); 7.77 (d, 2H ar, J = 8.7 Hz);
7.64 (s, 1H, H8); 7.30 (d, 2H ar, J = 8.4 Hz); 6.89 (d,
2H ar, J = 8.9 Hz); 6.16 (br s, 1H, NH); 4.80 (m, 3H,
PhCH2N and CH-i-PrN); 3.83 (s, 3H, CH3O); 1.54 (d,
6H, 2CH3-i-PrN, J = 6.8 Hz). 13C NMR (CDCl3) d:
162.5 (CO); 159.1 (Cq ar OMe); 154.6 (C4); 152.9
(C2); 136.6 (CH, C8); 129.5 (2CH ar); 129.3 (2CH ar
OMe); 116.8 (C5); 55.3 (CH3O); 46.8 (CH-i-PrN); 43.7
(CH2N); 22.5 (2CH3-i-PrN). MS (electrospray): m/z
451 (100%) [M+H]. HRMS calcd for C23H23ClN6O2:
m/z 451.1648 [M+H]. Found: 451.1644.
C16H26N6O2: C, 57.46; H, 7.84; N, 25.13. Found: C,
56.93; H, 7.87; N, 24.98.
4.23. N-[9-Isopropyl-6-(methoxy-ethylamino)-9H-purin-
2-yl]-isobutyramide (20c)
Compound 20c was prepared from 17c (100 mg,
0.249 mmol) which was oxidized to its 6-benzylsulfone-
purine derivative and subsequently substituted with 2-
methoxyethylamine (1.5 equiv, 0.374 mmol, 33 lL) in
absolute ethanol (2 mL). See the preparation of 18a
for details. Work up and purification by silica gel col-
umn chromatography (CH2Cl2/EtOH 100:0–95:5) gave
the expected product as a white solid: 50 mg, 63%. Rf:
0.23 (CH2Cl2/EtOH 98:2). Mp: 128 ꢁC. 1H NMR
(CDCl3) d: 8.09 (br s, 1H, NHCO); 7.71 (s, 1H, H8);
6.36 (br s, 1H, NH); 4.73 (sept, 1H, CH-i-PrN,
J = 6.8 Hz); 3.77 (br s, 2H, CH2N); 3.58 (t, 2H, CH2O,
J = 5.2 Hz); 3.42 (br s, 1H, CH-i-Pr); 3.36 (s, 3H,
CH3O); 1.55 (d, 6H, 2CH3-i-PrN, J = 6.8 Hz); 1.25 (d,
6H, 2CH3-i-Pr, J = 6.8 Hz). 13C NMR (CDCl3) d:
166.4 (CO); 154.9 (C4); 152.5 (C2); 136.8 (CH, C8);
117.2 (C5); 71.1 (CH2O); 58.8 (CH3O); 46.9 (CH-i-
PrN); 40.5 (CH2N); 22.5 (2CH3-i-PrN); 19.3 (2CH3-i-
Pr). MS (electrospray): m/z 343 (24%) [M+Na]; 321
(100%) [M+H]. HRMS calcd for C15H24N6O2: m/z
321.2034 [M+H]. Found: 321.2034. Anal. Calcd for
C15H24N6O2: C, 56.23; H, 7.55; N, 26.23. Found: C,
55.79; H, 7.24; N, 25.84.
4.21. N-[9-Isopropyl-6-(methoxy-ethylamino)-9H-purin-
2-yl]- butyramide (20a)
Compound 20a was prepared from purine 17a which
was oxidized as described previously to afford the sulfo-
nyl intermediate, that was reacted (150 mg, 0.374 mmol)
with 2-methoxyethylamine (1.5 equiv, 0.560 mmol,
50 lL) in absolute ethanol (5 mL). See the preparation
of 18a for details. Work up and purification by silica
gel column chromatography (CH2Cl2/EtOH: 100:0–
95:5) gave the expected product as a white solid:
63 mg, 53%. Rf: 0.52 (CH2Cl2/EtOH 95:5). Mp:
1
164 ꢁC. H NMR (CDCl3) d: 7.91 (br s, 1H, NHCO);
7.71 (s, 1H, H8); 6.21 (br s, 1H, NH); 4.70 (sept, 1H,
CH-i-PrN, J = 6.7 Hz); 3.79 (br s, 2H, CH2N); 3.60 (t,
2H, CH2O, J = 4.8 Hz); 3.39 (s, 3H, CH3O); 2.90 (br s,
2H, CH2 a); 1.79 (sext, 2H, CH2 b, J = 7.4 Hz); 1.58
(d, 6H, 2CH3-i-Pr, J = 6.7 Hz); 1.02 (t, 3H, CH3 c,
J = 7.3 Hz). 13C NMR (CDCl3) d: 174.1 (CO); 154.8
(C4); 152.5 (C2); 149.5 (C6); 136.8 (CH, C8); 116.9
(C5); 71.1 (CH2O); 58.8 (CH3O); 47.0 (CH-i-PrN);
39.1 (CH2 a); 22.5 (2CH3-i-Pr); 18.4 (CH2 b); 13.9
(CH3 c). MS (electrospray): m/z 343 (26%) [M+Na];
321 (100%) [M+H]. HRMS calcd for C15H24N6O2: m/z
321.2037 [M+H]. Found: 321.2034. Anal. Calcd for
C15H24N6O2: C, 56.23; H, 7.55; N, 26.23. Found: C,
56.57; H, 7.68; N, 26.20.
4.24. N-[9-Isopropyl-6-(methoxy-ethylamino)-9H-purin-
2-yl]-3-oxo-butyramide (20d)
Compound 20d was prepared from 2-iodopurine deriva-
tive 16 (200 mg, 0.498 mmol) and acetoacetamide
(2 equiv, 1.11 mmol, 112 mg) in THF (8 mL). See the
preparation of 18b for details. Work up and purification
by silica gel column chromatography (CH2Cl2/EtOH
100:0–98:2) gave the expected product as a yellow solid:

L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
139
105 mg, 57%. Rf: 0.28 (CH2Cl2/EtOH 98:2). Mp: 158 ꢁC.
1H NMR (CDCl3) d: 8.38 (br s, 1H, NHCO); 7.72 (s,
1H, H8); 6.26 (br s, 1H, NH); 4.67 (sept, 1H, CH-i-
PrN, J = 6.8 Hz); 4.11 (s, 2H, CH2CO); 3.75 (br s, 2H,
CH2N); 3.59 (t, 2H, CH2O, J = 5.1 Hz); 3.38 (s, 3H,
CH3O); 2.30 (s, 3H, CH3CO); 1.55 (d, 6H, 2CH3-i-Pr,
J = 6.8 Hz). 13C NMR (CDCl3) d: 205.0 (CO); 171.9
(CONH); 155.0 (C4); 152.0 (C2); 136.8 (CH, C8);
117.1 (C5); 71.0 (CH2O); 58.8 (CH3O); 52.5 (CH2CO);
46.8 (CH-i-Pr); 40.5 (CH2N); 30.1 (CH3CO); 22.6
(2CH3-i-Pr). MS (electrospray): m/z 357 (42%)
[M+Na]; 335 (100%) [M+H]. HRMS calcd for
C15H22N6O3: m/z 335.1838 [M+H]. Found: 335.1826.
Anal. Calcd for C15H22N6O3: C, 53.88; H, 6.63; N,
25.13. Found: C, 54.14; H, 6.62; N, 24.96.
NMR (CDCl3) d: 163.4 (CO); 159.1 (Cq ar); 156.4
(C2); 153.7 (C6); 152.1 (C4); 138.9 (CH, C8); 130.3
(Cq ar); 129.0 (2CH ar); 120.5 (C5); 114.1 (2CH ar);
55.3 (CH3O); 47.0 (CH2-i-Pr); 46.5 (CH-i-PrN); 44.3
(CH2N); 28.6 (CH-i-Pr); 23.1 (2CH3-i-PrN); 20.2
(2CH3-i-Pr). MS (electrospray): m/z 793 (2%) [2M+H];
419 (7%) [M+Na]; 397 (100%) [M+H]. HRMS calcd
for C21H28N6O2: m/z 397.2347 [M+H]. Found:
397.2349. Anal. Calcd for C21H28N6O2: C, 63.62; H,
7.12; N, 21.20. Found: C, 63.26; H, 7.18; N, 20.98.
4.27. 9-Isopropyl-6-(4-methoxy-benzylamino)-9H-purine-
2-carboxylic acid isopropylamide (21c)
Following the same procedure as for 21b, with 2-iodopu-
rine derivative 14 (500 mg, 1.18 mmol) and isopropyl-
amine (3 equiv, 3.5 mmol, 302 lL), a yellow solid was
obtained: 350 mg, 77%. Rf: 0.43 (CH2Cl2/EtOH 95:5).
Mp: 165 ꢁC. 1H NMR (CDCl3) d: 7.89 (s, 1H, H8); 7.81
(br d, 1H, NHCO, J = 8.0 Hz); 7.32 (d, 2H ar, J =
8.6 Hz); 6.87 (d, 2H ar, J = 8.6 Hz); 6.21 (br s, 1H, NH);
5.07 (sept, 1H, CH-i-PrN, J = 6.8 Hz); 4.79 (br s, 2H,
CH2N); 4.24 (m, 1H, CH-i-PrNCO, J = 6.6 Hz); 3.80 (s,
3H, CH3O); 1.57 (d, 6H, 2CH3-i-PrN, J = 6.8 Hz); 1.27
(d, 6H, 2CH3-i-Pr, J = 6.6 Hz). 13C NMR (CDCl3) d:
162.5 (CO); 159.1 (Cq ar); 152.2 (C4); 138.9 (CH, C8);
130.4 (Cq ar); 129.0 (2CH ar); 114.1 (2CH ar); 55.3
(CH3O); 46.4 (CH-i-PrN); 41.6 (CH-i-PrNH); 23.2
(2CH3-i-PrN); 22.7 (2CH3-i-PrNH). MS (electrospray):
m/z 787 (24%) [2M+Na]; 383 (100%) [M+H]. HRMS
calcd for C20H26N6O2: m/z 383.2190 [M+H]. Found:
383.2202. Anal. Calcd for C20H26N6O2: C, 62.81; H,
6.85; N, 21.97. Found: C, 62.81; H, 6.83; N, 21.93.
4.25. N-[9-Isopropyl-6-(methoxy-ethylamino)-9H-purin-2-
yl]-4-methoxy-benzamide (20e)
Compound 20e was prepared from 2-iodopurine deriva-
tive 16 (200 mg, 0.554 mmol) and p-methoxybenzamide
(2 equiv, 1.11 mmol, 167 mg) in THF (8 mL). See the
preparation of 18b for details. Work up and purification
by silica gel column chromatography (CH2Cl2) gave the
expected product as a yellow solid: 110 mg, 51%. Rf:
0.41 (CH2Cl2/EtOH 95:5). Mp: 166 ꢁC. 1H NMR
(CDCl3) d: 8.51 (br s, 1H, NHCO); 7.86 (d, 2H ar,
J = 8.7 Hz); 7.72 (s, 1H, H8); 6.91 (d, 2H ar,
J = 8.7 Hz); 6.38 (br s, 1H, NH); 4.78 (sept, 1H, CH-i-
PrN, J = 6.7 Hz); 3.82 (s, 3H, CH3OPh); 3.80 (br s,
2H, CH2N); 3.57 (t, 2H, CH2O, J = 5.0 Hz); 3.34 (s,
3H, CH3O); 1.53 (d, 6H, 2CH3-i-Pr, J = 6.8 Hz). 13C
NMR (CDCl3) d: 164.7 (CO); 162.4 (Cq ar OMe);
154.9 (C4); 152.7 (C2); 149.6 (C6); 136.8 (CH, C8);
129.3 (2CH ar); 127.2 (Cq ar); 117.2 (C5); 113.5 (2CH
ar); 71.2 (CH2O); 58.7 (CH3O); 55.3 (CH3OPh); 46.5
(CH-i-Pr); 40.3 (CH2N); 22.7 (2CH3-i-Pr). MS (electro-
spray): m/z 385 (100%) [M+H]; 325 (90%) [M-methoxy-
ethyl]. HRMS calcd for C19H24N6O3: m/z 385.1989
[M+H]. Found: 385.1983.
4.28. 6-(4-Chloro-benzylamino)-9-isopropyl-9H-purine-2-
carboxylic acid isopropylamide (22c)
Following the same procedure as for 21b, with 2-iodop-
urine derivative 15 (80 mg, 0.19 mmol) and isopropyl-
amine (3 equiv, 0.56 mmol, 50 lL), a white solid was
obtained: 55 mg, 76%. Rf: 0.43 (CH2Cl2/EtOH 95:5).
Mp: 152 ꢁC. 1H NMR (CDCl3) d: 7.93 (s, 1H, H8);
7.69 (br s, 1H, NHCO); 7.33 (s, 4H ar); 6.22 (br s, 1H,
NH); 5.09 (sept, 1H, NCH-i-Pr, J = 6.8 Hz); 4.86 (br s,
2H, CH2N); 4.24 (m, 1H, CH-i-PrNH, J = 6.6 Hz);
1.59 (d, 6H, 2CH3-i-PrN, J = 6.8 Hz); 1.25 (d, 6H,
2CH3-i-PrNH, J = 6.5 Hz). 13C NMR (CDCl3) d:
162.4 (CO); 153.8 (C2); 152.1 (C4); 148.9 (C6); 139.1
(CH, C8); 137.1 (Cq ar); 133.2 (Cq ar); 128.9 (2CH
ar); 128.8 (2CH ar); 120.4 (C5); 46.5 (CH-i-PrN); 44.4
(CH2N); 41.5 (CH-i-PrNH); 23.1 (2CH3-i-Pr); 22.7
(2CH3-i-Pr). MS (electrospray): m/z 797 (34%)
[2(M+H)+Na]; 795 (45%) [2M+Na]; 409 (30%)
[M+Na]; 387 (100) [M+H]. HRMS calcd for
C19H23ClN6O: m/z 387.1695 [M+H]. Found: 383.1706.
Anal. Calcd for C19H23ClN6O: C, 58.99; H, 5.99; N,
21.72. Found: C, 58.88; H, 6.25; N, 21.57.
4.26. 9-Isopropyl-6-(4-methoxy-benzylamino)-9H-purine-
2- carboxylic acid isobutylamide (21b)
A stirred mixture of 2-iodopurine derivative 14 (500 mg,
1.18 mmol) and Pd(PPh3)4 (0.05 equiv, 0.06 mmol,
68 mg) in dry THF (10 mL) was degassed with CO bub-
bling and maintained under CO atmosphere. Triethyl-
amine (2 equiv, 2.36 mmol, 329 lL) and isobutylamine
(3 equiv, 3.5 mmol, 352 lL) were then added, and the
resulting mixture was stirred at 50 ꢁC under CO atmo-
sphere for 2 h 30 min. The volatile material was evapo-
rated and the crude oil purified by silica gel column
chromatography (CH2Cl2/EtOH 100:0–95:5) to afford
the expected product as a white solid: 400 mg, 85%.
1
Rf: 0.68 (CH2Cl2/EtOH 95:5). Mp: 154 ꢁC. H NMR
(CDCl3) d: 8.08 (br s, 1H, NHCO); 7.90 (s, 1H, H8);
7.31 (d, 2H ar, J = 8.6 Hz); 6.87 (d, 2H ar, J = 8.6 Hz);
6.17 (br s, 1H, NH); 5.09 (sept, 1H, CH-i-PrN,
J = 6.7 HZ); 4.80 (br s, 2H, CH2NH); 3.79 (s, 3H,
CH3O); 3.30 (t, 2H, CH2-i-Pr, J = 6.5 Hz); 1.91 (sept,
1H, CH-i-Pr, J = 6.7 Hz); 1.58 (d, 6H, 2CH3-i-PrN,
J = 6.8 Hz); 0.96 (d, 6H, 2CH3-i-Pr, J = 6.7 Hz). 13C
4.29. 9-Isopropyl-6-(2-methoxy-ethylamino)-9H-purine-
2-carboxylic acid isobutylamide (23b)
Following the same procedure as for 21b, with 2-iodop-
urine derivative 16 (500 mg, 1.18 mmol) and isobutyl-

140
L. Vandromme et al. / Bioorg. Med. Chem. 15 (2007) 130–141
3. Meijer, L.; Raymond, E. Acc. Chem. Res. 2003, 36, 417.
4. Knockaert, M.; Greengard, P.; Meijer, L. Trends Phar-
macol. Sci. 2002, 23, 417.
amine (3 equiv, 3.5 mmol, 352 lL) a slightly yellow solid
was obtained: 440 mg, 95%. Rf: 0.32 (CH2Cl2/EtOH
95:5). Mp: 112 ꢁC. 1H NMR (CDCl3) d: 8.09 (br s,
1H, NHCO); 7.91 (s, 1H, H8); 6.48 (br s, 1H, NH);
4.97 (sept, 1H, CH-i-PrN, J = 6.8 HZ); 3.83 (br s, 2H,
CH2NH); 3.57 (t, 2H, CH2O, J = 5.2 Hz); 3.31 (s, 3H,
CH3O); 3.23 (t, 2H, CH2-i-Pr, J = 6.5 Hz); 1.85 (sept,
1H, CH-i-Pr, J = 6.7 Hz); 1.50 (d, 6H, 2CH3-i-PrN,
J = 6.8 Hz); 0.90 (d, 6H, 2CH3-i-Pr, J = 6.7 Hz). 13C
NMR (CDCl3) d: 163.3 (CO); 153.9 (C2); 151.8 (C4);
149.0 (C6); 138.8 (CH, C8); 120.3 (C5); 70.9 (CH2O);
58.6 (CH3O); 46.8 (CH2-i-Pr); 46.3 (CH-i-PrN); 40.3
(CH2NH); 28.4 (CH-i-Pr); 22.9 (2CH3-i-PrN); 19.9
(2CH3-i-Pr). MS (electrospray): m/z 691 (10%)
[2M+Na]; 357 (33%) [M+Na]; 335 (100%) [M+H].
HRMS calcd for C16H26N6O2: m/z 335.2190 [M+H].
Found: 335.2199. Anal. Calcd for C16H26N6O2: C,
57.46; H, 7.84; N, 25.13. Found: C, 56.94; H, 7.87; N,
24.81.
5. Wang, S.; Meades, C.; Wood, G.; Osnowski, A.; Ander-
son, S.; Yuill, R.; Thomas, M.; Mezna, M.; Jackson, W.;
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7. Anderson, M.; Beattie, J. F.; Breault, G. A.; Breed, J.;
Byth, K. F.; Culshaw, J. D.; Ellston, R. P. A.; Green, S.;
Minshull, C. A.; Norman, R. A. Bioorg. Med. Chem. Lett.
2003, 13, 3021.
8. Sayle, K. L.; Bentley, J.; Boyle, F. T.; Calvert, A. H.;
Cheng, Y.; Curtin, N. J.; Endicott, J. A.; Golding, B. T.;
Hardcastle, I. R.; Jewsbury, P. Bioorg. Med. Chem. Lett.
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Washio, Y.; Nishigaki, N. Bioorg. Med. Chem. Lett. 2003,
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4.30. 9-Isopropyl-6-(2-methoxy-ethylamino)-9H-purine-
2-carboxylic acid isopropylamide (23c)
Following the same procedure as for 21b, with 2-iodop-
urine derivative 16 (500 mg, 1.38 mmol) and isopropyl-
amine (3 equiv, 3.5 mmol, 354 lL) a white solid was
obtained: 400 mg, 90%. Rf: 0.35 (CH2Cl2/EtOH 95:5).
Mp: 122 ꢁC. 1H NMR (CDCl3) d: 7.88 (s, 1H, H8);
7.80 (br d, 1H, NHCO, J = 7.9 Hz); 6.53 (br s, 1H,
NH); 4.95 (sept, 1H, CH-i-PrN, J = 6.8 Hz); 4.14 (m,
1H, CH-i-PrNH, J = 6.6 Hz); 3.81 (br s, 2H, CH2N);
3.55 (t, 2H, CH2O, J = 5.3 Hz); 3.30 (s, 3H, CH3O);
1.49 (d, 6H, 2CH3-i-PrN, J = 6.8 Hz); 1.29 (d, 6H,
2CH3-i-Pr, J = 6.4 Hz). 13C NMR (CDCl3) d: 162.5
(CO); 154.5 (C4); 152.5 (C2); 149.7 (C6); 139.3 (CH,
C8); 120.8 (C5); 71.6 (CH2O); 59.2 (CH3O); 46.8 (CH-
i-PrN); 41.9 (CH-i-PrNH); 40.9 (CH2N); 23.5 (2CH3 i-
PrN); 23.1 (2CH3-i-PrNH). MS (electrospray): m/z 663
(21%) [2M+Na]; 343 (70%) [M+Na]; 321 (100%)
[M+H]. HRMS calcd for C15H24N6O2: m/z 321.2034
[M+H]. Found: 321.2046. Anal. Calcd for
C15H24N6O2: C, 56.23; H, 7.55; N, 26.23. Found: C,
56.17; H, 7.72; N, 26.02.
15. Davies, T. G.; Bentley, J.; Arris, C. E.; Boyle, F. T.;
Curtin, N. J.; Endicott, J. A.; Gibson, A. E.; Golding, B.
T.; Griffin, R. J.; Hardcastle, I. R.; Jewsbury, P.; Johnson,
L. N.; Mesguiche, V.; Newell, D. R.; Noble, M. E. M.;
Tucker, J. A.; Wang, L.; Whitfield, H. J. Nat. Struct. Biol.
2002, 9, 745.
16. Krystof, V.; Lenobel, R.; Havlicek, L.; Kuzma, M.;
Strnad, M. Bioorg. Med. Chem. Lett. 2002, 12, 3283.
17. Legraverend, M.; Grierson, D. S. Bioorg. Med. Chem.
2006, 14, 3987.
18. Ruetz, S.; Fabbro, D.; Zimmerman, J.; Meyer, T.; Gray,
N. S. Curr. Med. Chem.—Anti-Cancer Agents 2003, 3, 1.
19. Vandromme, L.; Piguel, S.; Lozach, O.; Meijer, L.;
Legraverend, M.; Grierson, D. S. Bioorg. Med. Chem.
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20. Furet, P.; Bold, G.; Hofmann, F.; Manley, P.; Meyer, T.;
Altmann, K.-H. Bioorg. Med. Chem. Lett. 2003, 13, 2967.
21. Maeda, Y.; Nakano, M.; Sato, H.; Miyazaki, Y.; Schwe-
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Acknowledgments
The authors thank ARC (Association pour la Recherche
sur le Cancer, France) for financial support (Contract
No. 4660), the French Ministry of Research (MENRT
fellowship for L.V.) and Institut Curie (Fellowship for
S.K.). This research was also supported by a grant from
the EEC (FP6-2002-Life Sciences & Health, PRO-KI-
´
NASE Research Project) (L.M.), and the ‘Canceropole
Grand-Ouest’ (L.M.).
22. Yue, E. W.; DiMeo, S. V.; Higley, C. A.; Markwalder, J.
A.; Burton, C. R.; Benfield, P. A.; Grafstrom, R. H.; Cox,
S.; Muckelbauer, J. K.; Smallwood, A. M. Bioorg. Med.
Chem. Lett. 2004, 14, 343.
23. Nugiel, D. A.; Vidwans, A.; Etzkorn, A.-M.; Rossi, K. A.;
Benfield, P. A.; Burton, C. R.; Cox, S.; Doleniak, D.;
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