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5.3. 6-(2-Ethylidene-1-phenylhydrazinyl)-9H-purine (9)
and O-benzylhydroxylamine hydrochloride (5.57 g,
34.9 mmol) in EtOH/H2O (1:1) (20 mL) and diisopro-
pylethylamine (6.0 mL, 34.6 mmol), heated at 60 ꢁC
for 24 h, to give the desired product (0.75 g, 48%) as
a white solid; mp 134–136 ꢁC. m/z (HRMS). Found:
(M+Na)+, 264.0858, C12H11N5ONa requires (M+Na)+
264.0861, deviation ꢀ1.3 ppm. UV: kmax (nm) (10%
MeOH in H2O) 272 (4700); kmin 236; pH 1: kmax 277
(4400); kmin 242; pH 12: kmax 277 (10100); kmin 241;
e260 (M) 3700. dC (CD3OD) 164.0, 151.9, 150.3,
144.8, 137.3, 127.5 (3· C), 127.0 (2· C), 117.8, 75.3.
To a solution of N6-amino-N6-phenyladenine (6c2,
243 mg, 1.07 mmol) in DMF, acetaldehyde (72 lL,
1.29 mmol) was added. After stirring at room tempera-
ture for 2 h, the organic solvent was evaporated under
reduced pressure. The resulting crude product was puri-
fied by flash column chromatography eluting with 5%
MeOH/DCM to give product (195 mg, 72%) as a pale
yellow solid; mp 163–165 ꢁC; dH 8.43 (1H, s, H8), 8.23
(1H, s, H2), 7.65 (2H, t, J 7.4, 2· ArH), 7.56 (1H, t, J
7.3, ArH), 7.32 (2H, d, J 7.3, 2· ArH), 6.80 (1H, q, J
5.4, CH3C@N), 2.11 (3H, d, J 5.4, CH3); dC (CD3OD)
158.6, 151.0, 150.8, 143.8, 143.6, 135.5, 130.1, 129.9,
129.4, 128.9, 16.5; m/z (HRMS). Found: (M+H)+,
253.1188, C13H12N6 requires (M+H)+ 253.1196, devia-
tion ꢀ3.2 ppm. UV kmax (nm) (H2O) 294 (16720), kmin
244; pH 1: kmax 304 (23570); kmin 252; pH 12: kmax 297
(20370); kmin 254.
1H NMR showed
tautomers.
a 2:1 ratio of imino-amino
Major tautomer. dH 13.02 (1H, s, NH), 11.23 (1H, s,
NH), 7.85 (1H, s, H8), 7.57 (1H, s, H2), 7.44–7.28
(5H, m, 5· ArH), 5.06 (2H, s, OCH2).
Minor tautomer. dH 12.85 (1H, s, NH), 11.13 (1H, s,
NH), 7.77 (1H, s, H8), 7.57 (1H, s, H2), 7.44–7.28
(5H, m, 5· ArH), 5.03 (2H, s, OCH2).
5.3.1. N6-Benzyloxyadenosine (7a). Prepared by general
procedure from 6-chloro-9-ribofuranosylpurine (0.43 g,
1.5 mmol) and O-benzylhydroxylamine hydrochloride
(1.0 g, 6.3 mmol) in EtOH/H2O (1:1) (10 mL) and trieth-
ylamine (1.5 mL, 10.5 mmol), heated at 60 ꢁC for 24 h,
to give product (0.26 g, 46%) as a white solid; dH
(MeOD) 8.35 (1H, br s, NH), 8.01 (1H, s, H8), 7.59
(1H, s, H2), 7.44–7.41 (2H, m, 2· ArH), 7.35–7.26
(3H, m, 3· ArH), 5.85 (1H, d, J 6.0, 10-H), 5.07 (2H,
s, OCH2), 4.57 (1H, app t, J 5.5, 20-H), 4.27 (1H, m,
30-H), 4.11 (1H, m, 40-H), 3.84 (1H, dd, J 12.4, 2.2, 50-
Ha), 3.71 (1H, dd. J 12.4, 2.5, 50-Hb); dC 164.0, 151.9,
148.8, 141.9, 137.3, 129.2, 129.1 128.9, 128.6, 128.5,
118.9, 88.2, 86.4, 75.5, 74.9, 71.2, 62.3; m/z (HRMS).
Found: (M+Na)+, 396.1276, C17H19N5O5Na requires
(M+Na)+ 312.1284, deviation ꢀ1.9 ppm. UV: kmax
(nm) (10% MeOH in H2O) 268 (12400); kmin 235; pH
1: kmax 268 (14600); kmin 236; pH 12: kmax 285 (12000);
kmin 236; e260 (M) 10700.
5.3.4. N6-Allyloxyadenosine (8a). Prepared by general
procedure from 6-chloro-9-ribofuranosylpurine (1.13 g,
3.95 mmol) and O-allylhydroxylamine hydrochloride
(2.60 g, 23.7 mmol) in EtOH (10 mL) and diisopropyl-
ethylamine (5.5 mL, 31.6 mmol), heated at 60 ꢁC for
24 h, to give the desired product (0.67 g, 53%) as a white
solid; mp 147–149 ꢁC; m/z (HRMS). Found: (M+H)+,
324.1307, C13H18N5O5 requires (M+H)+ 324.1308,
deviation ꢀ0.4 ppm. UV: kmax (nm) (10% MeOH in
H2O) 268 (e = 13800); kmin 235; pH 1: kmax 268
(17700); kmin 235; pH 12: kmax 283 (11700); kmin 244;
e260 (M) 12010. dC (CD3OD) 164.0, 151.9, 148.8,
141.9, 138.1, 118.9, 119.1, 89.2, 86.5, 74.6, 71.2, 62.1,
54.8. 1H NMR showed a 4:1 ratio of imino-amino
tautomers.
Major tautomer. dH 11.23 (1H, d, J 3.5, NH), 8.08 (1H,
s, H8), 7.58 (1H, d, J 3.5, H2), 6.00 (1H, m,
OCH2CH@CH2), 5.73 (1H, d, J 5.9, 10-H), 5.44 (1H,
d, J 6.2, 20-OH), 5.35 and 5.29 (2· 1H, 2· dd, J 3.4,
1.6, CH@CH2), 5.17 (1H, m, 30-OH), 5.08 (1H, t, J
5.9, 50-OH), 4.47 (2H, dd, J 6.2, 1.3, OCH2), 4.41 (2H,
dd, J 11.2, 5.9, 20-H), 4.07 (1H, app dd, J 8.3, 4.8, 30-
H), 3.89 (1H, app dd, J 7.2, 3.7, 40-H), 3.60 and 3.50
(2· 1H, 2· m, 50-Ha and 50-Hb).
5.3.2. 2-Amino-N6-benzyloxyadenosine (7b). Prepared by
general procedure from 2-amino-6-chloro-9-ribofurano-
sylpurine (0.59 g, 1.95 mmol) and O-benzylhydroxyl-
amine hydrochloride (1.86 g, 11.7 mmol) in EtOH/H2O
(1:1) (10 mL) and diisopropylethylamine (2.71 mL,
15.6 mmol), heated at 60 ꢁC for 24 h, to give product
(0.68 g, 90%) as a white solid; mp 109–111 ꢁC; dH
(D2O) 7.74 (1H, s, H8), 7.46 (2H, d, J 7.4, 2· ArH),
7.36 (2H, t, J 7.4, 2· ArH), 7.30 (1H, t, J 7.2, benzyl-
H), 5.77 (1H, d, J 6.2, 10-H), 5.06 (2H, s, OCH2), 4.66
(1H, app t, J 5.5, 20-H), 4.30 (1H, dd, J 5.0, 2.5, 30-H),
4.13 (1H, m, 40-H), 3.87 (1H, dd, J 12.4, 2.4, 50-Ha),
3.73 (1H, m, 50-Hb); dC (CD3OD) 164.0, 153.9, 148.8,
141.9, 137.3, 128.8, 128.4, 128.1, 127.9, 127.5, 114.0,
89.7, 85.5, 74.4, 70.6, 62.6, 55.0; m/z (HRMS). Found:
(M+H)+, 389.1574, C17H21N6O5 requires (M+H)+
389.1573, deviation 0.1 ppm. UV: kmax (nm) (10%
MeOH in H2O) 280 (11800); kmin 242; pH 1: kmax 297
(9000), 257 (7000); kmin 273, 241; pH 12: kmax 290
(10100); kmin 253; e260 (M) 8200.
Minor tautomer. dH 11.00 (1H, br s, NH), 8.45 (1H, s,
H8), 8.29 (1H, s, H2), 6.00 (1H, m, OCH2CH@CH2),
5.90 (1H, d, J 5.3, 10-H), 5.47 (1H, d, J 6.2, 20-OH),
5.35 and 5.29 (2· 1H, 2· m, CH@CH2), 5.19 (1H, m,
30-OH), 5.15 (1H, t, J 5.9, 50-OH), 4.58 (2H, dd, J
11.0, 5.7, 20-H), 4.47 (2H, m, OCH2), 4.11 (1H, app
dd, J 9.8, 4.8, 30-H), 3.94 (1H, m, 40-H), 3.60 and 3.50
(2· 1H, 2· m, 50-Ha and 50-Hb).
5.4. In vitro parasite growth inhibition assays
In vitro parasite growth inhibition was assessed by the
incorporation of [3H] hypoxanthine based on the meth-
od used by Desjardins42 and modified as described.43 All
assays included chloroquine diphosphate as a standard
5.3.3. N6-Benzyloxyadenine (7c). Prepared by general
procedure from 6-chloropurine (0.99 g, 6.41 mmol)