Synthesis of dG-C8 Adducts of HCAs
Chem. Res. Toxicol., Vol. 19, No. 6, 2006 773
(d, J ) 8.8, 1H), 7.60 (d, J ) 8.8, 1H), 7.54 (d, J ) 7.1, 2H),
7.45-7.20 (m, 5H), 6.74 (t, J ) 7.3, 1H), 5.58 (s, 2H), 4.81-4.75
(m, 1H), 4.67 (br, 2H), 3.99-3.95 (m, 1H), 3.92 (dd, J ) 16.6,
6.3, 1H), 3.78 (s, 3H), 3.76 (dt, J ) 10.1, 4.5, 1H), 3.58-3.50 (m,
1H), 2.13 (dq, J ) 13.0, 3.3, 1H), 3.57-3.42 (m, 1H), 2.06 (s,
3H), 0.95 (s, 9H), 0.88 (s, 9H), 0.15 (s, 6H), 0.04 (s, 3H), 0.03 (s,
3H). 13C NMR(CDCl3): 157.3, 155.2, 153.7, 152.6, 151.8, 147.8,
144.6, 136.8, 129.7, 128.8, 128.3, 127.9, 127.8, 122.5, 120.5, 117.8,
112.3, 106.1, 87.0, 82.5, 73.1, 67.2, 63.4, 35.7, 29.7, 28.6, 26.0,
25.9, 18.4, 18.1, 14.2, -4.40, -4.50, -5.15, -5.25. FAB-HRMS
(NBA) m/z: calcd for C40H56N9O4Si2 (M + H), 782.3993; found
782.3959.
N2-(2′-Deoxyguanosin-8-yl)-2-amino-3-methylimidazo[4,5-f]-
quinoline (5e) (19, 31). H NMR (DMSO-d6) δ: 10.98 (s, 1H),
1
8.79 (d, J ) 2.7, 1H), 8.69 (d, J ) 7.8, 1H), 7.86 (d, J ) 9.0, 1H),
7.75 (d, J ) 9.0, 1H), 7.55 (dd, J ) 8.4, 4.2, 1H), 6.48 (s, 2H),
6.46 (t, J ) 7.6, 1H), 4.46 (t, J ) 2.9, 1H), 3.78 (d, J ) 2.7, 1H),
3.70 (s, 3H), 3.65 (dd, J ) 11.7, 5.1, 1H), 3.50 (q, J ) 5.8, 1H),
2.05-2.01 (m, 1H). 13C NMR (DMSO-d6): 153.4, 153.2, 152.5,
148.8, 148.4, 147.5, 143.7, 129.6, 128.2, 121.4, 120.7, 117.3, 113.3,
103.7, 87.3, 81.9, 71.2, 62.2, 35.8, 28.6. FAB-HRMS (NBA) m/z:
calcd for C21H22N9O4 (M + H), 464.1795; found 464.1870.
N2-(2′-Deoxyguanosin-8-yl)-2-amino-6-methyldipyrido[1,2-a:
1
3′,2′-d]imidazole (5f) (Partially Identified in Ref 32). H NMR
N2-(O6-Benzyl-3′,5′-di-t-butyldimethylsilyl-2′-deoxyguanosin-
8-yl)-2-amino-6-methyldipyrido[1,2-a:3′,2′-d]imidazole (3f). 1H
NMR (CDCl3) δ: 8.42 (br, 1H), 8.27-8.15 (m, 2H), 7.50 (d, J )
7.1, 2H), 7.37-7.12 (m, 17H), 6.72 (br, 2H), 6.30 (s, 1H), 5.56
(br, 2H), 4.72 (br, 2H), 4.64 (br, 1H), 4.05 (br, 1H), 3.91 (d, J )
5.1, 2H), 3.02 (s, 1H), 2.65 (s, 3H), 2.30 (s, 1H), 0.90 (s, 9H), 0.80
(s, 9H), 0.12 (s, 6H), 0.04 (s, 3H), -0.02 (s, 3H). 13C NMR
(CDCl3): 158.6, 157.4, 153.3, 147.7, 147.3, 145.5, 139.8, 136.8,
132.2, 129.8, 128.2, 127.7, 127.5, 121.7, 120.6, 112.4, 111.7, 110.4,
87.4, 84.6, 72.0, 67.9, 62.9, 55.1, 38.8, 31.9, 29.7, 25.9, 25.8, 18.4,
18.1, 17.1, 14.2, -4.51, -4.60, -5.28, -5.31. FAB-HRMS (NBA)
m/z: calcd for C40H56N9O4Si2 (M + H), 782.3993; found 782.4252.
N2-(O6-Benzyl-3′,5′-di-t-butyldimethylsilyl-2′-deoxyguanosin-
8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (3g). 1H
NMR (CDCl3) δ: 8.34 (d, J ) 1.4, 1H), 7.57 (d, J ) 7.4, 1H),
7.41 (d, J ) 7.3, 1H), 7.47-7.28 (m, 9H), 7.36-7.17 (m, 17H),
6.73 (t, J ) 7.2, 1H), 5.46 (s, 1H), 4.78 (s, 2H), 4.79-4.76 (m,
1H), 4.63 (s, 2H), 3.98-3.92 (m, 1H), 3.92 (dd, J ) 16.7, 6.2,
1H), 3.76-3.71 (m, 1H), 3.63 (s, 3H), 3.57-3.50 (m, 1H), 2.11
(ddd, J ) 12.9, 6.7, 3.1, 1H), 0.95 (s, 9H), 0.88 (s, 9H), 0.15 (s,
6H), 0.04 (s, 3H), 0.03 (s, 3H). 13C NMR (CDCl3): 157.1, 156.6,
153.1, 152.8, 152.1, 146.5, 140.2, 138.4, 136.5, 130.8, 128.8, 128.4,
128.3, 127.9, 127.3, 127.0, 125.8, 112.5, 109.1, 87.0, 82.6, 73.1,
67.7, 63.5, 60.3, 35.7, 28.0, 25.9, 25.8, 18.4, 18.1, 14.2, -4.55,
-5.20, -5.29. FAB-HRMS (NBA) m/z: calcd for C42H57N9O4Si2
(M + H), 808.4150; found 808.4149.
Deprotection Procedure for O6-Benzyl and Silyl Protective
Groups of 3. The benzyl group at the O6 position of 3 was removed
by catalytic hydrogenation with Pd black/H2. Typically, 3 (0.1
mmol) was dissolved in THF. Pd black (20∼30 mg) was added
into the solution and stirred under a balloon filled with H2 gas until
the initial spot on TLC disappeared. After the reaction was
completed, the catalyst was removed by filtration and washed with
THF. The filtrate was further treated with 300 µL of a triethylamine‚
trihydrogen fluoride (TEA‚3HF) complex. After overnight reaction,
the solvent was evaporated to dryness and the resulting residue
was subjected to octadecylsilyl (ODS) column chromatography to
yield 5 almost quantitatively.
(DMSO-d6) δ: 10.59 (br, 1H), 9.68 (br, 1H), 8.63 (br, 1H), 8.15
(br, 1H), 8.09 (br, 1H), 7.26 (br, 1H), 6.85 (br, 1H), 6.36 (s, 2H),
6.26 (s, 1H), 5.55 (br, 1H), 5.20 (br, 1H), 4.39 (br, 1H), 3.87 (br,
1H), 3.72 (d, J ) 16.8, 2H), 2.75 (s, 1H), 2.49 (s, 3H), 2.03 (s,
1H). 13C NMR (DMSO-d6): 155.6, 152.7, 149.7, 148.8, 146.6,
141.8, 139.4, 130.9, 129.1, 127.3, 126.8, 122.4, 112.6, 110.6, 87.1,
83.2, 71.5, 61.9, 55.1, 16.5. FAB-HRMS (NBA) m/z: calcd for
C21H22N9O4 (M + H), 464.1795; found 464.1885.
N2-(2′-Deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo-
1
[4,5-b]pyridine (5g) (33, 34). H NMR (DMSO-d6) δ: 8.28 (d, J
) 1.8, 1H), 7.88 (d, J ) 1.8, 1H), 7.63 (d, J ) 7.4, 2H), 7.37 (d,
J ) 7.6, 1H), 7.35 (d, J ) 7.6, 1H), 7.25 (t, J ) 7.3, 1H), 6.38 (t,
J ) 7.3, 1H), 6.25 (s, 2H), 4.36 (t, J ) 2.9, 1H), 3.67 (dd, J ) 7.9,
5.1, 1H), 3.55 (dd, J ) 12.8, 6.1, 1H), 3.53 (s, 3H), 3.40 (dd, J )
11.4, 5.7, 1H), 3.18-3.12 (m, 1H), 1.93 (ddd, J ) 12.9, 6.9, 2.5,
1H). 13C NMR (DMSO-d6): 154.1, 152.7, 152.6, 149.6, 148.8,
139.4, 137.9, 129.8, 128.9, 126.7, 125.8, 113.4, 108.6, 87.3, 82.0,
71.2, 62.3, 28.1. FAB-HRMS (NBA) m/z: calcd for C23H24N9O4
(M + H), 490.1951; found 490.1743.
N2-(N2-Dimethylaminomethylene-3′,5′-di-t-butyldimethylsilyl-
2′-deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5-
b]pyridine (6g). Compound 5g (200 mg) was dissolved in a solvent
of N,N-dimethylformamide dimethyl acetal (DMF-DMA, 10 mL)
with N,N-dimethylformamide (DMF, 2 mL) and stirred at room
temperature. As the reaction proceeded, the solid materials were
separated from the solution. The precipitate was collected and
1
washed with methanol (72%). H NMR (DMSO-d6) δ: 9.25 (br,
1H), 8.50 (s, 1H), 8.33 (s, 1H), 7.56 (d, J ) 7.3, 2H), 7.47-7.40
(m, 3H), 6.73 (t, J ) 7.2, 1H), 4.67 (s, 1H), 3.94 (br, 1H), 3.82-
3.77 (m, 2H), 3.61 (s, 3H), 3.57-3.47 (m, 1H), 3.15 (s, 3H), 3.10
(s, 1H), 2.15-2.07 (m, 1H), 0.93 (s, 9H), 0.86 (s, 9H), 0.13 (s,
6H), 0.02 (s, 3H), 0.00 (s, 3H). 13C NMR (DMSO-d6): 157.0, 156.1,
154.6, 151.5, 148.3, 144.8, 140.1, 138.5, 131.0, 128.9, 127.3, 127.0,
125.6, 112.3, 86.9, 82.6, 73.3, 67.9, 63.7, 41.3, 36.8, 35.1, 27.9,
25.9, 25.8, 18.4, 18.0, -4.42, -4.49, -5.06, -5.26. FAB-HRMS
(NBA) m/z: calcd for C38H57N10O4Si2 (M + H), 773.4102; found
773.4642.
N2-(N2-Dimethylaminomethylene-2′-deoxyguanosin-8-yl)-2-
amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (7g). To a stirred
suspension of 6g in THF was added triethylamine trihydrogenfluo-
ride (800 µL). A clear solution was obtained, and it was stirred for
24 h. The resulting precipitate was then recovered by filtration and
washed with methanol to afford pure 7g (85%). 1H NMR (DMSO-
d6) δ: 8.37 (s, 1H), 8.30 (d, J ) 1.7, 1H), 7.90 (d, J ) 1.5, 1H),
7.64 (d, J ) 7.3, 2H), 7.37 (t, J ) 7.6, 2H), 7.26 (t, J ) 7.3, 1H),
6.49 (t, J ) 7.3, 1H), 4.41 (s, 1H), 3.70 (q, J ) 4.1, 1H), 3.57 (d,
J ) 13.3, 6.5, 1H), 3.54 (s, 3H), 3.43 (dd, J ) 10.8, 5.4, 1H), 3.02
N2-(2′-Deoxyguanosin-8-yl)-2-amino-3,8-dimethylimidazo[4,5-
1
f]quinoxaline (5c) (28). H NMR (DMSO-d6) δ: 10.76 (s, 1H),
8.79 (s, 1H), 7.93 (d, J ) 8.8, 1H), 7.85 (d, J ) 8.8, 1H), 6.54 (t,
J ) 7.4, 1H), 6.30 (s, 2H), 4.52-4.45 (m,1H), 3.81 (dd, J ) 7.9,
5.0 1H), 3.73 (s, 3H), 3.69 (dd, J ) 11.5, 4.9, 1H), 3.54 (dd, J )
11.6, 5.0, 1H), 3.35-3.35 (m, 1H), 2.77 (s, 3H), 2.73 (s, 3H), 2.05
(ddd, J ) 13.0, 6.8, 2.6, 1H). 13C NMR (DMSO-d6): 154.3, 153.5,
152.4, 151.4, 150.1, 149.0, 144.2, 136.7, 130.7, 129.1, 124.1, 122.4,
112.4, 109.8, 87.2, 82.0, 71.3, 62.3, 36.2, 28.5, 22.1. FAB-HRMS
(NBA) m/z: calcd for C21H23N10O4 (M + H), 479.1903; found
479.1930.
(s, 3H), 2.91 (s, 3H), 2.85-2.77 (m, 1H), 2.02-1.92 (m, 1H). 13
C
NMR (DMSO-d6): 157.6, 156.1, 155.2, 152.1, 150.3, 147.5, 145.2,
139.4, 137.8, 130.1, 128.8, 127.2, 126.7, 125.6, 113.4, 112.7, 87.2,
82.6, 71.5, 62.2, 45.7, 36.8, 34.5, 28.1. FAB-HRMS (NBA) m/z:
calcd for C26H29N10O4 (M + H), 545.2373; found 545.2404.
N-[N2-Dimethylaminomethylene-5′-(4,4′-dimethoxytrityl)-2′-
deoxyguanosin-8-yl]-2-amino-1-methyl-6-phenylimidazo[4,5-b]-
pyridine (8g). To a suspended solution of 7g (80 mg) in lutidine/
DMF (1:1) were added triethylamine (3 equiv) and 4,4-
dimethoxytrityl chloride (DMTrCl, 3 equiv). After the addition, the
reaction mixture was allowed to warm at 80 °C and stirred for 2 h.
Additional DMTrCl (3 equiv) was then added, and the mixture was
N3-(2′-Deoxyguanosin-8-yl)-3-amino-1,4-dimethyl-5H-pyrido-
1
[4,3-b]indole (5d). H NMR (DMSO-d6) δ: 10.69 (s, 1H), 7.98
(br, 1H), 7.46 (br, 1H), 7.40 (br, 1H), 7.22 (br, 1H), 6.33 (br, 3H),
5.11 (br, 1H), 4.36 (br, 1H), 3.77 (br, 1H), 3.63 (dd, J ) 11.6, 3.8,
1H), 3.55-3.47 (m, 1H), 3.07-3.09 (m, 1H), 2.28 (s, 3H), 2.05-
1.95 (m, 1H). 13C NMR (DMSO-d6): 157.9, 153.1, 141.5, 138.8,
130.1, 127.8, 127.5, 127.2, 127.1, 126.3, 125.6, 122.0, 120.0, 119.6,
112.7, 86.7, 82.9, 73.2, 70.2, 66.8, 31.6. FAB-HRMS (NBA) m/z:
calcd for C23H25N8O4 (M + H), 477.1998; found 477.2076.