C. Pavlik et al. / Dyes and Pigments 89 (2011) 9e15
11
at this temperature for 40 min. After cooling the to room temper-
ature, the inorganic salts were removed by vacuum filtration and
washed with acetonitrile. The filtrate and washings were combined
and the solvents were evaporated in vacuo to give a residue that
was recrystallized from ethyl acetate to yield 10c [24,25] (1.32 g,
d
7.81 (d, J ¼ 1.3 Hz,1H), 7.75e7.41 (m,12H), 7.09 (s,1H), 6.88 (s,1H),
6.7 (t, J ¼ 12.2 Hz, 2H), 6.60 (d, J ¼ 13.2 Hz, 2H), 4.7 (s, 2H), 4.52 (t,
J ¼ 5.4 Hz, 2H), 4.2e4.01 (m, 4H), 3.61 (t, J ¼ 5.3 Hz, 2H), 3.0 (m, 4H),
1.91e1.70 (m, 8H), 1.70e1.57 (m, 12H); 13C NMR (DMSO):
d 206.8,
172.1,168.0,167.6,166.3,159.7,148.9e144.9,144.8,141.0,138.1,130.8,
129.7, 128.3, 127.7, 123.4, 120.2, 110.5, 105.1, 49.8, 44.0, 30.4, 29.8,
27.9, 26.8, 22.4. HR-TOF MS. Calcd for C51H61N8O12S2Na2 (M þ Naþ),
m/z 1087.3646. Found, m/z 1087.3641.
7.16 mmol, 81%). Mp, 95e96 ꢀC. 1H NMR:
5.09 (s, 2H), 3.77 (s, 3H); 13C NMR:
d
7.11 (s, 1H), 7.05 (s, 1H),
d
166.5, 126.5, 127.3, 53.2, 50.7.
2.7. N-(2-Hydroxyethyl)-2-(1H-imidazol-1-yl)acetamide, 11a
2.11. N-(2-Hydroxyethyl)-2-(4-nitro-1H-imidazol-
1-yl)acetamido-ICG, 12b
Methyl 2-(1H-imidazol-1-yl)acetate,10a (0.48 g, 3.39 mmol), was
added to 6 mL of absolute MeOH. The solution was vigorously stirred
while freshly distilled aminoethanol (0.90 mL, 13.59 mmol) was
added slowly, and the reaction was stirred overnight at ambient
temperature [26]. The reaction mixture was then concentrated and
the remaining solid was dissolved in dry acetone and passed through
a plug of silica. The resulting residue was recrystallized from ethyl
acetate to yield 11a (0.396 g, 2.34 mmol, 69%). Mp,132.8e134.0 ꢀC.1H
ICG derivative 9 (0.162 g, 0.216 mmol) was dissolved in 2.49 mL of
DMF. This solution was treated with a catalytic amount of DMAP, and
the solutionwas cooled to 0 ꢀC. DCC (0.094 g, 0.454 mmol) wasadded,
and the mixture was stirred for 30 min [17,28]. Addition of 11b
(0.212 g, 0.990 mmol) was followed by stirring for 2 h at 0 ꢀC,
warming to ambient temperature and then stirring overnight. The
reaction mixture was concentrate and poured into 25 mL of anhy-
drous ether, and the resulting precipitate was collected. Column
chromatography on C18-reverse phase silica using H2O/MeOH
(1:1.1e1:1) gave 12b (0.142 g, 0.121 mmol, 56%). 1H NMR (DMSO):
NMR (MeOD): d 7.70 (s, 1H) 7.14 (s, 1H), 7.01 (s, 1H), 4.74 (s, 2H), 3.63
(t, 2H, J ¼ 5.7 Hz), 3.43 (t, 2H, J ¼ 5.7 Hz, MeOD overlap); 13C NMR
(MeOD):
d 168.1, 138.1, 127.6, 120.3 59.9, 41.8. HR-TOF MS. Calcd for
C7H11N3O2Na (M þ Naþ), m/z 192.0649. Found, m/z 192.0673.
d
8.13 (s, 1H), 7.82 (d, J ¼ 1.3 Hz, 2H), 7.79e7.30 (m, 1H), 6.64 (t,
2.8. N-(2-Hydroxyethyl)-2-(4-nitro-1H-imidazol-
1-yl)acetamide, 11b
J ¼ 12.3 Hz, 2H), 6.53 (d, J ¼ 13.2 Hz, 2H), 4.68 (s, 2H), 4.07 (t, J ¼ 5.7 Hz,
2H), 4.10 (m, 4H), 3.64 (t, J ¼ 5.7 Hz, 2H), 3.05 (m, 4H), 1.87e1.70 (m,
8H),1.70e1.56 (m,12H); 13C NMR (DMSO):
d 204.4,172.8,172.1,168.3,
Methyl 2-(4-nitro-1H-imidazol-1-yl)acetate, 10b (0.636 g,
3.39 mmol), was added to 6 mL of absolute MeOH. The solution was
vigorously stirred while freshly distilled aminoethanol (0.90 mL,
13.59 mmol) was added slowly, and the reaction was stirred over-
night at ambient temperature [26]. The reaction mixture was
concentrated and the resulting solid was recrystallized from ethyl
acetate to yield 11b (0.587 g, 2.74 mmol, 81%). Mp, 136e137 ꢀC. 1H
166.7, 164.8, 152.5, 149.3e146.1, 146.0, 140.9, 138.1, 130.7, 137.9, 136.8,
133.2, 121.0, 110.6, 114.9, 62.7, 49.2, 47.0, 44.3, 34.5, 30.2, 28.3, 27.1,
22.4. HR-TOF MS. Calcd for C51H59N10O16S2Na2 (M þ Naþ), m/z
1177.3347. Found, m/z 1117.3341.
2.12. N-(2-Hydroxyethyl)-2-(2-nitro-1H-imidazol-1-
yl)acetamido-ICG, 12c
NMR (MeOD):
d 8.32 (s, 1H) 8.17 (s, 1H), 7.74 (s, 1H), 4.90 (s, 2H),
4.71 (s, 1H,), 3.62 (t, 2H, J ¼ 5.7 Hz), 3.38 (t, 2H, J ¼ 5.7 Hz); 13C NMR
ICG derivative 9 (0.162 g, 0.216 mmol) was dissolved in 2.49 mL
of DMF. To this solution was added a catalytic amount of DMAP and
the solution was cooled to 0 ꢀC. DCC (0.094 g, 0.454 mmol) was
added, and the mixture was allowed to stir for 30 min [17,28].
Addition of 11c (0.212 g, 0.990 mmol) was followed by stirring for
2 h at 0 ꢀC, warming to ambient temperature and then stirring
overnight. The reaction mixture was concentrate and poured into
25 mL of anhydrous ether, and the resulting precipitate was
collected. Column chromatography on C18-reverse phase silica
using H2O/MeOH (1:1.1e1:1) gave 12c (0.112 g, 0.095 mmol, 44%).
(MeOD): d 172.1, 137.8, 121.33, 59.9, 49.4, 41.8. HR-TOF MS. Calcd for
C7H10N4O4Na (M þ Naþ), m/z 1237.0600. Found, m/z 237.0636.
2.9. N-(2-Hydroxyethyl)-2-(2-nitro-1H-imidazol-
1-yl)acetamide, 11c
Methyl 2-(2-nitro-1H-imidazol-1-yl)acetate, 10c (0.636 g,
3.39 mmol), was added to 6 mL of absolute MeOH. The solution was
vigorously stirred while freshly distilled aminoethanol (0.90 mL,
13.59 mmol) was added slowly, and the reaction was stirred over-
night at ambient temperature [26]. The reaction mixture was
concentrated and the remaining solid was dissolved in dry acetone
and passed through a plug of silica. The resulting residue was
recrystallized from ethyl acetate to give 11c [27] (0.587 g, 2.74 mmol,
1H NMR (DMSO):
d
7.83 (d, J ¼ 1.2 Hz, 2H), 7.8e7.5 (m, 7H), 7.45 (d,
J ¼ 8.5 Hz, 2H), 7.36 (s, 1H), 6.65 (t, J ¼ 12.5 Hz, 2H), 6.53 (d,
J ¼ 13.3 Hz, 2H), 4.69 (s, 2H), 4.51 (t, J ¼ 5.3 Hz, 2H), 4.2e4.0 (m, 4H),
3.65 (t, J ¼ 5.6 Hz, 2H), 3.04 (m, 4H), 1.92e1.70 (m, 8H), 1.70e1.55
(m, 12H); 13C NMR (DMSO):
d 202.3, 171.4, 167.5, 166.8, 166.0, 146.7,
81%). Mp,163.5e164.7 ꢀC.1H NMR (MeOD):
J ¼ 0.9 Hz), 5.36 (s, 2H), 3.85 (t, 2H, J ¼ 5.4 Hz), 3.58 (t, 2H, J ¼ 5.6 Hz);
13C NMR (MeOD):
166.1, 156.3127.5, 127.3, 60.1, 51.4, 41.8.
d 7.52 (s,1H), 7.37 (d,1H,
144.0, 143.9e140.8, 140.7, 140.5, 130.8, 129.8, 128.0, 127.7, 127.2,
121.1, 110.6, 105.2, 63.1, 50.8, 49.7, 49.0, 43.0, 30.5, 27.6, 27.0, 22.4.
HR-TOF MS. Calcd for C51H59N10O16S2Na2 (M þ Naþ), m/z 1177.3307.
Found, m/z 1177.3321.
d
2.10. N-(2-Hydroxyethyl)-2-(1H-imidazol-1-yl)acetamido-ICG, 12a
ICG derivative 9 (0.162 g, 0.216 mmol) was dissolved in 2.49 mL
of DMF. This solution was treated with a catalytic amount of DMAP,
and the solution was cooled to 0 ꢀC. DCC (0.094 g, 0.454 mmol) was
added, and the mixture was stirred for 30 min [17,28]. Addition of
11a (0.167 g, 0.990 mmol) was followed by stirring for 2 h at 0 ꢀC,
warming to ambient temperature and then stirring overnight. The
reaction mixture was concentrate and poured into 25 mL of anhy-
drous ether, and the resulting precipitate was collected. Column
chromatography on C18-reverse phase silica using H2O/MeOH
(1:1.1e1:1) gave 12a (0.102 g, 0.0864 mmol, 40%). NMR (DMSO):
3. Results and discussion
The bioreductive properties of 2-nitroimidazoles lead to selec-
tive cytotoxicity toward hypoxic cells within tumours [29]. Nitro-
imidazoles serve as hypoxic cell radiosensitizers, via a free-radical
mechanism, increasing the sensitivity to radiation of normally
radiation-resistant hypoxic cells [30]. Many nitroimidazole deriv-
atives are known [31,32], and their anti-cancer applications have
been studied. Misonidazole (2) [33], etanidazole (3) [34], and san-
azole (4) [35,36] are important examples, as shown in Scheme 1.