Synthesis of a new series of purine derivatives and their anti-cyclin-dependent kinase activities

Article abstract of DOI:10.1002/jhet.5570380145

The synthesis of new purine derivatives designed to inhibit cell cycle regulating cyclin-dependent kinases (CDKs), is reported. These compounds, related to olomoucine and roscovitine, are characterised by the presence of a pyrrolidine methanol substituent

Full text of DOI:10.1002/jhet.5570380145

Jan-Feb 2001
Synthesis of a New Series of Purine Derivatives and their
Anti-Cyclin-Dependent Kinase Activities
299
Michel Legraverend* [a], Odile Ludwig [a], Sophie Leclerc [b] and Laurent Meijer [b]
[a] UMR 176 CNRS, Institut Curie, Section de Recherche, Bât. 110-112, Centre Universitaire, 91405 ORSAY cedex, France
[b] CNRS, Station Biologique, B.P. 74, 29682 ROSCOFF cedex, France
Received June 16, 1999
The synthesis of new purine derivatives designed to inhibit cell cycle regulating cyclin-dependent kinases
(CDKs), is reported. These compounds, related to olomoucine and roscovitine, are characterised by the pres-
ence of a pyrrolidine methanol substituent at C-2 and a variety of ortho, meta and/or para substituents on the
C-6 arylamino group.
J. Heterocyclic Chem., 38, 299 (2001).
The preparation of combinatorial purine librairies using
solid-phase methods has been recently reported [8-10] . We
have previously described [11] the synthesis and
CDK1/cyclin B inhibitory activity of various C2-amino
ethanol substituted purines, as well as C2 alkynylated
purines like 4 [12,13] with potent anti-CDK activity in
vitro. It has been established by several groups that this type
of activity can be improved by varying the position and the
nature of the substituent on the N6 phenyl ring. We describe
in the present paper the synthesis of new N6 substituted
purine derivatives with their CDK inhibitory activity in
vitro. The purpose of this work is to study the effect of mod-
ifications of the anilino or benzylamino group at C-6 while
keeping substituents at C-2 and N-9 unchanged (pyrrolidine
methanol and isopropyl respectively).
Cyclin-dependent Kinases (CDK) have raised consider-
able interest in view of their essential role in the regulation
of the cell cycle division [1-3]. Following the identifica-
tion of 6-dimethylaminopurine and isopentenyladenine as
CDK1 [4] inhibitors, Vesely et al. described in 1994 [5]
the purine Olomoucine 1 as a first lead compound which
specifically inhibited the CDK1/cyclin B, CDK2/cyclin A,
CDK2/cyclin E kinases and the brain CDK5/p35 kinase
among 35 kinases tested (IC 's: 7, 7, 7 and 3 µM, respec-
50
tively). An improved compound, Roscovitine 2, described
in 1997 [6] inhibited the same enzymes with IC values
50
of 0.65, 0.7, 0.7 and 0.16 µM, respectively. Reviews on
chemical inhibitors of CDKs have recently appeared [7].
Results.
The synthesis of the compounds described in this article,
was achieved from 6-chloro-2-iodo-9-isopropyl-(9H)-
purine, itself obtained from 2-amino-6-chloro-9-alkyl(9H)-
purine as previously described [14, 15]. Substitution of the
2-amino group in 7, by a 2-iodo atom was performed by
nitrosation using isoamyl nitrite in the presence of iodide
+
i) (CH ) CH-NH , n-BuOH, 100°C ii) CH(OEt) , H , (Me) NCOCH , RT iii) isoamyle nitrite (3 equivalents), CH I (10 equivalents), CuI (1 equivalent),
3 2
2
3
2
3
2 2
I (1 equivalent), THF reflux iv) amine, Ethanol, 45-50°C v) pyrrolidine methanol 120-140°C
2

300
M. Legraverend, O. Ludwig, S. Leclerc and L. Meijer
Vol. 38
Table 3
sources (diiodomethane, cuprous iodide, iodine), according
to the original method of Nair and Richardson [16].
Physical Data
Selective nucleophilic substitution of the 6-chloro group
was obtained below 50 °C, whereas nucleophilic substitution
of the 2-iodo atom by (R)-pyrrolidine methanol was achieved
around 140 °C. The structures as well as the results of in vitro
inhibitory experiments (concentrations giving 50% inhibi-
Compounds Yields
(%)
Mp
(°C)
Molecular
Formula
Analyses %
Calcd./Found
H
C
N
9f
67
69
80
70
72
85
84
78
98
78
65
67
86
87
64
57
88
55
83
79
80
62
98
40
64
65
49
31
53
74
82
150-153
192-194
198-200
153-156
186-188
200-202
136-140
140-142
175-177
140-142
124-126
174-176
153-156
149-151
120-124
141-143
145-147
130-133
138-140
165-167
90-91
C
H
N O I
45.05 4.45 15.45
44.89 4.38 15.37
41.67 3.28 15.18
41.86 3.47 15.14
41.67 3.28 15.18
41.71 3.44 15.15
38.58 2.67 13.23
39.07 2.78 12.98
45.40 4.29 16.55
45.34 4.34 16.58
41.67 3.28 15.18
41.93 3.47 15.33
45.40 4.29 16.55
45.36 4.34 16.41
45.40 4.29 16.55
45.03 4.46 16.47
46.94 4.67 15.91
17 20
5 2
9h
C
C
C
H N F I
tion of starfish oocytes cyclin-dependent kinase, IC ) for
16 15 5 3
50
compounds 11, 12, and 13 are given in Tables 1 and 2.
Physical data are given in Table 3 and 4. CDK1/cyclin B was
purified and assayed as previously described [6,13].
9i
H N F I
16 15 5 3
9j
H N F I
17 14 5 6
9k
C H N OI
16 18 5
Table 1
Inhibition of CDK1/cyclin B Activity by Compounds 11 and 12
9l
C H N F I
16 15 5 3
9m
9q
C H N OI
16 18 5
C
H
N OI
5
16 18
9r
C H N OI
16 18 5 /
1/5 cyclohexane 46.52 4.53 16.35
N I
9s
C
H
54.67 4.59 14.49
54.63 4.66 14.36
36.71 2.86 15.29
36.68 2.93 15.31
36.71 2.86 15.29
36.83 2.91 15.04
63.62 7.12 21.20
63.59 7.08 21.15
61.45 6.38 20.47
61.61 6.23 20.47
55.18 5.56 19.30
54.98 5.26 19.14
59.92 6.29 20.96
59.87 6.21 20.94
61.95 7.09 19.70
62.11 7.13 19.42
58.06 5.80 19.34
58.11 5.79 19.36
58.06 5.80 19.34
58.26 5.79 19.37
52.59 4.81 16.73
52.92 4.97 16.58
63.62 7.12 21.20
63.57 7.08 20.86
58.06 5.80 19.34
58.84 5.72 19.18
63.62 7.12 21.20
63.75 7.25 21.19
64.75 6.86 23.85
65.04 7.11 23.71
58.99 5.99 21.72
58.72 6.07 21.42
54.16 5.26 19.95
54.57 5.25 19.85
53.53 5.55 19.11
22 22
5
10d
10e
11a
11b
11c
11d
11f
11h
11i
11j
11k
11l
11m
12a
12b
12c
12d
12e
13q
13r
13s
C H N BrI
14 13 5
C
C
C
H N BrI
14 13 5
H
N O
6
21 28
2
Compound
R
IC
Compound
R
IC
50
50
(µM)
(µM)
H
N O
6
21 26
3
11a
11b
11c
11d
11e
11f
11g
11h
11i
p-OCH
m, p-OCH O
m,p-di-Cl
p-Cl
0.21
0.35
0.43
0.33
0.65
0.3
0.45
0.7
0.8
1
12a
12b
12c
12d
12e
H
m-Cl
m,p-di-Cl 0.43
m-Br
p-Br
0.30
0.43
3
C
H N OCl
20 24 6 2
2
C
H N OCl
20 25 6
0.33
0.30
H
C
H N O
22 30 6 3
m,m'-di-OCH
m-I
3
C
C
C
H N OF
21 25 6
3
3
6
m-CF
3
p-CF
3
H
N OF
6
21 25
11j
m,m'-di-CF
3
11k
11l
11m
o-OCH
1.8
4
0.3
3
H
N OF
6
22 24
o-CF
1
2
-
-
7
0.65
3
m-OCH
3
C
H N O
21 28 6 2
The o = ortho, m = meta, p = para substituents of the phenyl group.
125
C H N OF
21 25 6
3
Table 2
130-133
151-153
135-137
179-181
125-126
182-185
90-92
C H N O
21 28 6 2
Inhibition of CDK1/cyclin B Activity by Compounds 13
C
H N O
19 24 6
C
H N OCl
19 23 6
C
H N OCl
19 22 6 2
C
H N OBr
19 23 6
1/10 cyclohexane 53.54 5.55 19.41
C
H
N OBr
52.91 5.37 19.48
53.03 5.51 19.44
63.62 7.12 21.20
63.25 7.24 20.82
63.62 7.12 21.20
63.81 7.16 21.17
71.03 7.06 18.41
71.25 7.01 18.69
19 23
6
Compound
R , R
IC (µM)
1
2
50
C
H N O
21 28 6
2
2
13q (S) [a]
13r (R) [a]
13s
R = H; R = CH(CH OH)Phe
0.8
>10
>10
1
2
2
160-162
139-141
C H N O
21 28 6
R = H; R = CH(CH OH)Phe
1
2
2
R = CH Phe; R = CH Phe
1
2
2
2
C
H N O
27 32 6
[a] S and R refer to stereochemical configuration at N-6.

Jan-Feb 2001
Synthesis of a New Series of Purine Derivatives
Table 4
301
1
H NMR Data for compounds 9f-s, 10d, 10e, 11a-m, 12a-e, and 13q-s (δ values in ppm,
Tetramethylsilane as the Internal Standard, in Deuterated Chloroform, 200 MHz)
1
1
Compounds
H NMR
Compounds
H NMR
9f
7.65 (s, 1H, H8), 6.53 (d, 2H, Phe, J = 2.1), 6.36 (t,
1H, Phe, J = 2.1), 6.08 (br s, 1H, NH), 4.83-4.73 (m,
3H, CH(CH ) , CH Phe), 3.77 (s, 6H, 2xOCH ),
11d
7.49 (s, 1H, H-8), 7.30 (m, 4H, Phe), 6.80 (br s,
1H, NH), 4.77 (m, 2H, CH Phe), 4.65-4.55 (m,
2
1H, CH(CH ) ), 4.35-4.25 (m, 1H, H2'), 3.90-3.40
3 2
2
3
3 2
1.54 (d, 6H, CH(CH ) , J = 6.8).
(m, 4H, CH OH, H5'), 2.15-1.60 (m, 4H, H3',
3 2
2
9h
9i
7.88 (br s, 1H, H8), 7.68-7.47 (m, 4H, Phe), 6.8 (br
H4'), 1.53 (d, 6H, CH(CH ) , J = 5.8).
3 2
s, 1H, NH), 4.94-4.80 (m, 3H, CH(CH ) , CH Phe),
11f
6.54 (d, 2H, Ho,o' -Phe, J = 2.2), 6.36 (t, 1H, Hp-
3 2
2
1.59 (d, 6H, CH(CH ) , J = 6.8).
Phe, J = 2.2), 3.76 (s, 6H, 2xOCH ), other protons
3 2
3
7.84 (s, 1H, H8), 7.63-7.48 (m, 4H, Phe), 6.8 (br s,
are identical to 11a.
1H, NH), 4.92-4.82 (m, 3H, CH(CH ) , CH Phe),
11h
11i
11j
7.69 (s, 1H, H-8), 7.70-7.45 (m, 4H, Phe), other
protons are identical to 11a.
7.64-7.43 (m, 5H, Phe, H-8), 4.98-4.75 (m, 2H,
3 2
2
1.58 (d, 6H, CH(CH ) , J = 6.8).
3 2
9j
7.89-7.70 (m, 4H, H-8, Phe), 6.85 (br s, 1H, NH),
4.95-4.78 (m, 3H, CH(CH ) , CH Phe), 1.59 (d, 6H,
CH Phe), other protons are identical to 11a.
3 2
2
2
CH(CH ) , J = 6.8).
7.89 (unresolved d, 2H, Ho,o'-Phe), 7.76 (s, 1H,
3 2
9k
7.66 (s, 1H, H-8), 7.44-7.39 (m, 1H, Phe), 7.27-7.22
(m, 1H, Phe), 6.95-6.85 (m, 2H, Phe), 6.2 (br s, 1H,
NH), 4.85-4.65 (m, 3H, CH(CH ) , CH Phe), 3.87
H-8), 7.56 (unresolved t, 1H, Hp-Phe), 5.00-4.75
(br d, 2H, CH Ph), other protons are identical to
2
11a.
3 2
2
(s, 3H, OCH ), 1.59 (d, 6H, CH(CH ) , J = 6.8).
11k
11l
7.43-6.82 (m, 4H, Phe), 3.87 (s, 3H, OCH ), other
3
3 2
3
9l
7.72-7.68 (m, 3H, H-8, Phe), 7.52 (t, 1H, Phe, J =
7.3), 7.38 (t, 1H, Phe, J = 7.50), 6.09 (br s, 1H, NH),
protons are identical to 11a.
7.70-7.30 (m, 4H, Phe), 5.10-4.92 (br d, 2H,
5.00 (br s, 2H, CH Phe), 4.81 (sept, 1H,
CH Ph), other protons are identical to 11a.
2
2
CH(CH ) ), 1.56 (d, 6H, CH(CH ) , J = 6.8).
11m
7.28-7.20 (m, 1H, Ho-Phe), 6.99-6.78 (m, 3H,
3 2
3 2
9m
7.63 (s, 1H, H-8), 7.25 (t, 1H, Phe, J = 8.1), 6.96-
6.93 (m, 2H, Phe), 6.85-6.81 (m, 1H, Phe), 5.20 (br
s, 2H, CH Phe), 4.88-4.70 (m, 3H, CH(CH ) ,
Ho', m, p-Phe), 3.79 (s, 3H, OCH ); other protons
are identical to 11a.
7.83 (d, 2H, o,o'-Phe, J = 7.8), 7.63 ( s, 1H, H-8),
7.37 (t, 2H, m,m'-Phe, J = 7.8), 7.09 (t, 1H, p-Phe,
3
12a
12b
12c
2
3 2
CH Phe), 3.80 (s, 3H, OCH ), 1.56 (d, 6H,
2
3
CH(CH ) , J = 6.8).
J = 7.3); 4.64 (sept, 1H, CH(CH ) , J = 6.6), 4.45-
3 2
3 2
9q
9r
identical to 9r
4.30 (m, 1H, H-2'), 3.98-3.65 (m, 4H, CH OH,
2
7.90 (s, 1H, H-8), 7.51-7.28 (m, 5H, Phe), 5.45 (br s,
CH -5'), 2.30-1.65 (m, 4H, 2xCH ), 1.58 (d, 6H,
2
2
1H, NH), 4.81 (m, 1H, CH(CH ) ), 4.05 (d, 1H,
CH(CH ) , J = 6.7).
3 2
3 2
CHOH, J = 5.5), 3.70-3.30 (br m, 2H, OH, CHPhe),
8.23 (s, 1H, H-8), 7.95 (br s, 1H, NH), 7.64 (s, 1H,
Phe), 7.47-7.43 (m, 1H, Phe), 7.27-7.20 (m, 1H,
Phe), 7.04-7.00 (m, 1H, Phe), 4.64 (sept, 1H,
1.60-1.54 (dd, 6H, CH(CH ) ).
3 2
9s
7.67 (s, 1H, H-8), 7.30-7.26 (m, 10H, 2xPhe), 5.45
(br s, 2H, CH Phe), 4.89-4.82 (m, 3H, CH Phe,
CH(CH ) , J = 6.6), 4.35 (m,1H, H-2'), 3.9-3.7
2
2
3 2
CH(CH ) ), 1.55 (d, 6H, CH(CH ) , J = 6.7).
(m, 4H, CH OH, CH -5'), 2.10-1.70 (m, 4H,
3 2
3 2
2
2
10d
8.19 (s, 1H, H-8), 7.96 (br s, 1H, NH), 7.79 (m, 1H,
Phe), 7.75-7.68 (m, 1H, Phe), 7.23 (d, 2H, Phe),
2xCH ), 1.56 (d, 6H, CH(CH ) , J = 6.7).
2
3 2
8.38 (s, 1H, H-8), 8.22 (br s, 1H, NH), 7.67 (s, 1H,
Phe), 7.45-7.34 (m, 2H, Phe), 4.65 (sept, 1H,
4.86 (sept, 1H, CH(CH ) , J = 6.7), 1.59 (d, 6H,
3 2
CH(CH ) , J = 6.7).
CH(CH ) , J = 6.6), 4.37 (m,1H, H-2'), 3.79 (m,
3 2
3 2
10e
11a
7.80 (s, 1H, H-8), 7.68-7.46 (m, 4H, Phe), 4.86
4H, CH OH, CH -5'), 2.18-2.01 (m, 5H, OH,
2
2
(sept, 1H, CH(CH ) , J = 6.7), 1.60 (d, 6H,
2xCH ), 1.58 (d, 6H, CH(CH ) , J = 6.8).
3 2
2
3 2
CH(CH ) , J = 6.7).
12d
12e
7.95-7.10 (m, 4H, Phe), 7.62 (s, 1H, H-8), other
protons are identical to 12a.
3 2
7.47 (s, 1H, H-8), 7.30 (d, 2H, Hm,m'-Phe, J = 8.6),
6.85 (d, 2H, Ho, o'-Phe, J = 8.6), 5.95-5.75 (m, 1H,
7.73 (d, 2H, Phe, J = 8.6), 7.64 (s, 1H, H-8), 7.45
(d, 2H, Phe, J = 8.5), other protons are identical to
12a.
NH), 4.8-4.65 (m, 2H, CH Ph), 4.59 (septet, 1H,
2
CH(CH ) , J = 6.7), 4.40-4.24 (m, 1H, H ), 3.79 (s,
3 2
2'
3H, OCH ), 3.85-3.55 (m, 4H, CH OH, CH -5'),
13q
7.66 (s, 1H, H-8), 7.60-7.20 (m, 5H, Phe), 5.60-
3
2
2
2.22-2.02 (m, 1H, H-3'), 2.00-1.80 (m, 2H, CH -4'),
5.15 (m, 1H, CHPhe), 4.62 (sept, 1H, CH(CH ) ,
2
3 2
1.75-1.60 (m, 1H, H-3'), 1.53 (d, 6H, CH(CH ) , J =
J = 6.8); 4.4-4.2 (br m, 1H, H-2' pyrrolidine),
3 2
6.7).
4.10-3.94 (m, 2H, HOCH CHPhe), 3.80-3.55 (m,
2
11b
11c
7.50 (s, 1H, H-8), 6.89-6.73 (m, 3H, Phe), 5.93 (s,
2H, OCH O), 4.70-4.60 (m, 3H, CH Phe,
4H, CH OH, CH -5' pyrrolidine), 2.25-1.50 (m,
2
2
4H, 2xCH ), 1.54 (d, 6H, CH(CH ) , J = 6.8).
2
2
2
3 2
CH(CH ) ), 4.32 (m, 1H, H2'), 3.72-3.68 (m, 4H,
13r
13s
identical to 13q.
3 2
H5', CH OH), 2.07-1.89 (m, 4H, H3', H4'), 1.54 (d,
7.53 (s, 1H, H-8), 7.45-7.15 (m, 10H, 2xPhe),
2
6H, CH(CH ) , J = 6.7).
5.66-5.35 (br s, 2H, CH Phe), 5.06-4.80 (br s, 2H,
3 2
2
7.54 (s, 1H, H-8), 7.51-7.26 (m, 3H, Phe), 6.30 (br s,
CH Phe), 4.88-4.65 (br m, 1H, CH(CH ) ), 4.45-
2
3 2
1H, NH), 4.80 (br s, 2H, CH Phe), 4.63 (m, 1H,
4.25 (br m, 1H, H-2' pyrrolidine), 3.85-3.50 (m,
2
CH(CH ) ), 3.72-3.60 (m, 4H, CH OH, H2'), 2.1-
4H, CH OH, CH -5' pyrrolidine); 2.25-1.55 (m,
3 2
2
2
2
1.6 (m, 5H, H3', H4', OH), 1.55 (d, 6H, CH(CH ) ,
4H, 2xCH ), 1.56 (d, 6H, CH(CH ) , J = 6.8).
3 2
2
3 2
J = 6.7).

302
M. Legraverend, O. Ludwig, S. Leclerc and L. Meijer
Vol. 38
(R)-2-phenylglycinol, dibenzylamine, purchased from Aldrich)
in ethanol containing triethyamine (4 equivalents) under inert
atmosphere at 50 °C for 3-4 hours. After evaporation of the
volatile material in vacuo, the residue was dissolved in
dichloromethane and washed twice with water. The organic
phase was dried (magnesium sulfate), evaporated to dryness and
subjected to colomn chromatography on silica gel eluting with 1-
5% ethanol in dichloromethane. The crude products obtained
after column chromatography were sufficiently pure for the next
step. Yields refer to chromatographically purified products.
Unless otherwise stated, products were recrystallized from hep-
tane to provide an analytical sample. Melting points (mp) refer to
recrystallized samples.
Concluding Remarks.
Interestingly, with the exception of ortho-substitution,
most of the substituents on the 6-benzylamino series
increase activity with respect to the unsubstituted deriva-
tive 11e (Table 1 and 2). The best activity is observed for
para-methoxy and para-chloro derivatives 11a and 11d.
Meta substituted derivatives are intermediate between
ortho and para substituted compounds. The influence of
meta and/or para substituents in the anilino series is less
important. The drop of activity of the N6-disubstituted
compounds 13 should be noticed, and may be explained by
the loss of the capacity of hydrogen bond formation
between NH-6 and the enzyme [13]. However, most of
meta/para substituted compounds are more inhibitory than
the lead compounds, Olomoucine (1) and Roscovitine (2).
Further modifications at N9 and C2 combined with the
best substituents at C6 should lead to improved anti-cyclin
dependent kinase inhibitory activities.
Compounds 9a, 9b, 9c, 9d, 10a, 10b and 10c have already
been described [13] as well as 11e, and 11g [11].
General Procedure for the Preparation of Compounds 11 and 12.
A mixture of iodo-purines 9 or 10 (2 mmoles), in N,N-
dimethylacetamide (40 mL), tripropylamine (1 mL), and 1.5
equivalents of (R)-2-pyrrolidine methanol was stirred at 140 °C
for 24 hours. After evaporation to dryness (oil pump), the residue
was dissolved in dichloromethane, washed with water (twice),
adsorbed on silica gel and chromatographed on silica gel colomn,
eluting successively with dichloromethane and 2-5% ethanol in
dichloromethane. Yields refer to purified compounds after chro-
matography. When necessary, analytical samples were obtained
after recrystallization from heptane. Melting points refer to ana-
lytical samples.
EXPERIMENTAL
The melting points were taken on a Kofler hot stage apparatus
and are uncorrected. Elemental analyses were performed by the
"Service de Microanalyse", CNRS, ICSN, 91198 Gif sur Yvette,
1
France. Proton nuclear magnetic resonance ( H-nmr) spectra
Biological Assays.
were recorded at 200 MHz on a Bruker AC 200 spectrometer in
deuteriochloroform (unless otherwise specified). Chemical shifts
were reported in δ ppm referenced to tetramethylsilane. Coupling
constants were indicated in hertz.
Starfish CDK1/cyclin B was purified from M oocytes by affin-
CKShs1
ity chromatography on p9
was eluted by free p9
-Sepharose beads, from which it
CKShs1
. It was assayed with 1 mg histone H1
32
(Sigma type III-S)/mL, in the presence of 15 µM [γ- P] ATP
(3,000 Ci/mmol; 1 mCi/mL) in a final volume of 30 µL. After 10
minutes incubation at 30°C, 25 µL aliquots of supernatant were
spotted onto 2.5 x 3 cm pieces of Whatman P81 phosphocellulose
paper, and, after 20 seconds, the filters were washed five times
(for at least 5 minutes each time) in a solution of 10 mL phos-
phoric acid/liter of water. The wet filters were transferred into 6
mL plastic scintillation vials, and counted in the presence of 2
mL ACS (Amersham) scintillation fluid. The kinase activity was
expressed in pmoles phosphate incorporated in histone H1/10
2-Amino-6-chloro-9-isopropyl-9H-purine (7) was synthesized
from pyrimidine 5 [14] as previously described [15].
6-Chloro-2-iodo-9-isopropyl-9H-purine (8).
A solution of compound 7 (1 g, 4.72 mmoles) in tetrahydrofu-
ran (40 mL) was stirred under reflux for one hour in the presence
of isoamylnitrite (1.6 g, 14.2 mmoles), diiodomethane (12.6 g, 47
mmoles), iodine (1.2 g, 4.7 mmoles) and cuprous iodide (0.9 g,
4.8 mmoles). The mixture was cooled to room temperature, fil-
tered, and the filtrate was evaporated to dryness before purifica-
tion by colomn chromatography eluting with 5% ethanol in
dichloromethane. Compound 8 was obtained in 80% yield; mp
minute incubation or in % of maximal activity. IC 's were calcu-
50
lated from inhibitor dose-response curves.
1
108-109 °C; H nmr (dimethylsulfoxide-d ) δ 8.76 (s, 1H), 4.83
Acknowledgments.
6
(m, 1H), 1.55 (d, 6H, J = 6.7 Hz).
We are indebted to the "Association pour la Recherche sur le
Cancer" (ARC, subvention N° 9814 to ML, and ARC 9314 to
LM), as well as the "Conseil Régional de Bretagne" (to LM) for
financial support.
Anal. Calcd. for C H N ClI: C, 29.79; H, 2.50; N, 17.37.
8
8 4
Found: C, 30.07; H, 2.65; N, 17.58.
General Procedure for the Preparation of 6-Substituted Purines 9
and 10.
Nucleophilic substitution of the 6-chloro atom in 8 was
achieved by reaction with 1.5 equivalents of the appropriate
amine (4-methoxybenzylamine, piperonylamine, 3,4-
dichlorobenzylamine, 4-chlorobenzylamine, 3,5-dimethoxy-
benzylamine, 3-methoxybenzylamine, 3-trifluoromethyl-
benzylamine, 4-trifluoromethylbenzylamine, 3,5-bis(trifluoro-
methyl)benzylamine, 2-methoxybenzylamine, 2-trifluoromethyl-
benzylamine, benzylamine, aniline, 4-bromoaniline, 3-bromoani-
line, 3-chloroaniline, 3,4-dichloroaniline, (S)-2-phenylglycinol,
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