Synthesis of two potential heterocyclic amine food mutagens

Article abstract of DOI:10.1002/jhet.5570450304

(Chemical Equation Presented) The syntheses of two potential food mutagens formed during cooking, 2-amino-3,6,7-trimethyl-3H-imidazo[4,5-b]pyridine (1) and 2-amino-3,6,7-trimethyl-3H-imidazo[4,5-c]pyridine (2), are described.

Full text of DOI:10.1002/jhet.5570450304

May-Jun 2008
661
Synthesis of Two Potential Heterocyclic Amine Food Mutagens
Mary J. Tanga*, Joseph A. Kozocas and Todd K. Tochimoto
SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025
E-mail: mary.tanga@sri.com
Received February 1, 2007
CH3
CH3
H3C
H3C
N
N
N
N
NH2
NH2
N
N
CH3
CH3
1
2
The syntheses of two potential food mutagens formed during cooking, 2-amino-3,6,7-trimethyl-3H-
imidazo[4,5-b]pyridine (1) and 2-amino-3,6,7-trimethyl-3H-imidazo[4,5-c]pyridine (2), are described.
J. Heterocyclic Chem., 45, 661 (2008).
INTRODUCTION
trimethyl-3H-imidazo[4,5-b]pyridine; 2-amino-3,5,6-
trimethyl-3H-imidazo[4,5-b]pyridine [16]; 2-amino-3,5,7-
trimethyl-3H-imidazo[4,5-b]pyridine; 2-amino-1,4,7-
trimethyl-3H-imidazo[4,5-c]pyridine; 2-amino-1,6,7-
trimethyl-3H-imidazo[4,5-c]pyridine; 2-amino-3,4,6-
trimethyl-3H-imidazo[4,5-c]pyridine [17], 2-amino-1,4,6-
trimethyl-3H-imidazo[4,5-c]pyridine and 2-amino-1,5,7-
trimethyl-3H-imidazo[4,5-b]pyridine [18]. We now report
the syntheses of two other possible isomers-2-amino-3,6,7-
trimethyl-3H-imidazo[4,5-b]pyridine (1) and 2-amino-
3,6,7-trimethyl-3H-imidazo[4,5-c]pyridine (2)—so that
they can be compared and tested against the unknown
mutagen. The syntheses of the two compounds have not
previously been reported in the literature.
Several lines of evidence indicate that cooking
conditions and dietary habits can contribute to human
cancer risk through the ingestion of food mutagens. Our
diet is a complex mixture that provides nutritional
sustenance but may also be important in the causation,
modulation, and prevention of cancer. Heterocyclic
amines are formed in a temperature- and time-dependant
manner during cooking from creatine or creatinine, certain
free amino acids and sugars via the Maillard reaction,
which are present in uncooked meat and fish muscle
[1,2,3]. Heterocyclic amines have the general structure of
two or three rings with an exocyclic amino group attached
to one of the rings. Recent studies have shown an
association with consumption of well-done meats and the
risk of prostate cancer [4], pancreatic cancer [5], breast
cancer [6], and colorectal cancers or adenomas [7-9].
While the amount of heterocyclic amines consumed in
ordinary life is low and perhaps not sufficient to explain
the incidence of human cancer the coexistence of many
other mutagens/carcinogens of either autobiotic or
xenobiotic type and the possibility that these amines
induce genomic instability and heighten sensitivity to
tumor promoters suggest minimizing exposure is prudent
[10].
RESULTS AND DISCUSSION
The initial successful synthesis 2-amino-3,6,7-
trimethyl-3H-imidazo[4,5-b]pyridine (1) is shown in
Scheme I. Commercially available 3,4-dimethylpyridine
(5) was treated with 30% hydrogen peroxide to form 3,4-
dimethylpyridine N-oxide (6). To form the 2-amino
functionality we attempted to nitrate 6 using potassium
nitrate in sulfuric acid without success. We also tried to
brominate 6 without success. We then treated 5 with
sodium amide in a Chichibabin reaction and obtained a
4:1 mixture of 2-amino-4,5-dimethylpyridine (10) and 2-
amino-4,5-dimethylpyridine (11) in 36% yield as shown
in Scheme II. The amines 10 and 11 were difficult to
separate so the mixture was treated with potassium nitrate
in acid, followed by silica gel chromatography to give 7%
of 2-amino-4,5-dimethyl-3-nitropyridine (12).
In an effort to prepare 1 more efficiently we developed
the synthesis shown in Scheme I. The N-oxide 6 was
methylaminated using the reagent 4 to give 4,5-dimethyl-
2-(methylamino)pyridine (7) in 40% yield. The amine 7
was nitrated to form 4,5-dimethyl-2-(methylamino)-3-
nitropyridine (8) in 47% yield. The nitro group of 8 was
quantitatively reduced to form the diamine 9, which was
To understand the risk consuming heterocyclic amines
poses to humans it is critical to isolate, identify, and
synthesize these compounds. Although some of these
compounds have been identified and synthesized, one that
contributes 10-15% of total mutagenic activity of a fried
meat sample [11-15] has only been identified by mass
spectrometry to have a molecular weight of 176 [11,13,14].
From the available preliminary data, the mutagenic
compound has been determined to be one of the twelve
isomers of 2-amino-trimethylimidazopyridine (TMIP)
[11,14]. To investigate the biological risk associated with
ingesting this unidentified compound, we have previously
synthesized eight of the possible isomers: 2-amino-1,5,6-

662
M. J. Tanga, J. A. Kozocas and T. K. Tochimoto
Vol 45
Scheme I
O
Cl
CH3
CH3
SOCl2
N
H
N
3
4
CH3
CH3
CH3
H3C
H3C
H3C
H2O2
HOAc
KNO3
1. 4, !
H2SO4
2. 5% NaOH
N
O
N
NH
N
CH3
7
5
6
CH3
CH3
NH2
CH3
H3C
NO2
H3C
H3C
H2
N
BrCN
EtOH
NH2
10% Pd/C
N
N
NH
N
NH
N
CH3
CH3
CH3
8
9
1
then cyclized using cyanogen bromide to give the desired
final product 1.
The synthesis of 2-amino-3,6,7-trimethyl-3H-imidazo-
[4,5-c]pyridine (2) is shown in Scheme III. Bromination
methylamine resulted in displacement of the nitro group
with methylamine to give 3-bromo-5,6-dimethyl-4-
(methylamino)pyridine (17). By varying the reactions
conditions, it was experimentally determined that by
Scheme II
CH3
N
CH3
N
CH3
N
CH3
N
H3C
H2N
H3C
+
H3C
NO2
NH2
H3C
KNO3
NaNH2
H2SO4
Toluene
NH2
5
10
11
12
of 4-amino-2,3-dimethylpyridine (13), whose synthesis
we have previously published [17] gave 4-amino-3-
bromo-5,6-dimethylpyridine (14) in 59% yield. The
bromo compound 14 was treated with 40% aqueous
methyl amine and copper sulfate at 200° in a stainless
steel bomb to form the diamine 15 in 10% yield, which
was pure only after extensive chromatography. The
reaction was not suitable to be able to prepare enough
material to complete the synthesis. Treatment of 14 with
70% hydrogen peroxide in sulfuric acid provided 3-
bromo-5,6-dimethyl-4-nitropyridine (16) in 32% yield. At
room temperature treatment of 16 with aqueous
using 2 equivalents of copper (I) chloride and 0.1
equivalents of copper (II) chloride at room temperature,
the correct product 18 was formed in 35% yield.
Reduction of the nitro group of 18 gave the desired
diamine 15 in quantitative yield. Ring closure of 15 using
cyanogen bromide in ethanol at 120° in a bomb resulted
in formation of 2-amino-3,6,7-trimethyl-3H-imidazo-
[4,5-c]pyridine (2).
In conclusion, two potential heterocyclic amine food
mutagens were synthesized for biological evaluation
using an approach that is applicable to the preparation of
similar heterocyclic compounds.

May-Jun 2008
Synthesis of Two Potential Heterocyclic Amine Food Mutagens
663
Scheme III
NH2
H2N
NH2
H
N
40% CH3NH2
CuSO4
H3C
H3C
Br
H3C
H3C
H3C
H3C
Br2
CH3
HOAc
N
N
N
200°
13
14
15
70% H2O2
H2SO4
H3C
NH
NO2
40% CH3NH2
EtOH
H3C
Br
H3C
Br
RT
H3C
N
H3C
N
16
17
40% CH3NH2
CuCl/CuCl2
RT
CH3
NO2
H2
H
N
BrCN
EtOH
H3C
H3C
N
N
10% Pd/C
CH3
NH2
15
N
EtOH
H3C
N
120°
CH3
18
2
hydrogen peroxide and 10 mL of glacial acetic acid was heated
at 90° for 18 hours. The excess acetic acid was removed under
high vacuum, and the solution was neutralized with sodium
carbonate, extracted with 3 x 50 mL of chloroform, dried
(sodium sulfate), filtered, and concentrated to give 4.15 g (72%)
of a white solid (6); 1H nmr (deuteriochloroform) δ 2.22 (s, 3H),
2.26 (s, 3H), 7.03 (d, 1H, J = 6.39 Hz), 7.99 (d, 1H, J = 6.39
Hz), 8.04 (s, 1H).
EXPERIMENTAL
Melting points (uncorrected) were obtained using a Thomas-
Hoover melting point apparatus. The ir spectra were recorded on
a Perkin Elmer 1600 FTIR spectrophotometer, the uv spectra on
a Varian DMS-90 spectrometer, and the nmr spectra on a Varian
Gemini 300 MHz spectrometer. All chemical shifts are reported
in parts per million (δ) downfield from tetramethylsilane. The
nmr multiplicities are reported using the following
abbreviations: s, singlet; d, doublet; t, triplet; q, quartet; m,
multiplet; and b, broad. Column chromatography was done
using E. Merck silica gel 40 (70-230 mesh, ASTM). All solvents
were dried over 3Å molecular sieves, except tetrahydrofuran,
which was dried by refluxing over sodium with benzophenone
ketyl as an indicator. Microanalyses were performed by Atlantic
Microlab, Inc., Norcross, GA.
4,5-Dimethyl-2-(methylamino)pyridine (7). To 3.56 g (23.3
mmoles) of N-methylbenzimidoyl chloride (4) and 3,4-
dimethylpyridine-N-oxide (6) was added 25 mL of
trichloroethylene and the solution was heated at reflux under
argon for 12 hours. The solution was cooled to room
temperature, filtered and concentrated under vacuum. To the
residue was added 50 mL of 5% sodium hydroxide solution.
The solution was brought to reflux for 1 hour then steam
distilled to afford 822 mg of a 2:1 mixture of product (7) and
3,4-lutidine (5). This material was combined with the distillation
pot, extracted into chloroform, dried (sodium sulfate) and
evaporated. Vacuum distillation at 0.3 mm Hg gave 1.53 g
(48%) of a 2:1 mixture of product (7) and 3,4-lutidine (5), which
Since 2-amino-3,6,7-trimethyl-3H-imidazo[4,5-b]pyridine (1)
and 2-amino-3,6,7-trimethyl-3H-imidazo[4,5-c]pyridine (2) are
potential carcinogens and mutagens, direct contact should be
avoided.
N-Methylbenzimidoyl chloride (4). A solution of 10.0 g (74
mmoles) of N-methylbenzamide (3) in 10.6 g (89 mmoles) of
thionyl chloride was heated at reflux for 2 hours under argon.
The mixture was vacuum distilled at 65˚ and 0.3 mm Hg to give
1
was used in the next step without further purification; H nmr
(deuteriochloroform) δ 2.09 (s, 3H), 2.17 (s, 3H), 2.88 (d, 3H, J
= 5.31 Hz), 4.32 (br s, 1H), 6.21 (s, 1H), 7.81 (s, 1H).
1
9.21 g (81%) of product (4); H nmr (deuteriochloroform) δ 3.48
(s, 3H), 7.39 (m, 3H), 7.97 (m, 2H).
4,5-Dimethyl-2-(methylamino)-3-nitropyridine (8). To 1.53
g of crude 4,5-dimethyl-2-(methylamino)pyridine (7) dissolved
in 10 mL of concentrated sulfuric acid was added 1.36 g (13.5
mmoles) of potassium nitrate in portions. The mixture was
3,4-Dimethylpyridine N-Oxide (6). A mixture of 5.00 g
(46.7 mmoles) of 3,4-dimethylpyridine (5) in 12 mL of 30%

664
M. J. Tanga, J. A. Kozocas and T. K. Tochimoto
Vol 45
allowed to stir for 16 hours at room temperature, then diluted
with 35 mL of water, neutralized with 10% sodium carbonate
solution and extracted into chloroform (3 x 150 mL), dried
(sodium sulfate) and evaporated. Silica gel chromatography
eluting with 10% ethyl acetate/90% hexanes gave 817 mg (40%)
residue was purified by silica gel chromatography eluting with
5% methanol/95% chloroform to afford 100 mg (7%) of a
1
yellow solid (12); H nmr (deuteriochloroform) δ 2.14 (s, 3H),
2.52 (s, 3H), 5.02 (br s, 2H), 8.68 (s, 1H).
4-Amino-3-bromo-5,6-dimethylpyridine (14). A solution of
2.85 g (23.3 mmoles) of 4-amino-2,3-dimethylpyridine (13) in 7
mL of glacial acetic acid under argon was cooled with a water
bath at room temperature while being treated slowly with a
solution of 2.4 mL (46.6 mmoles) of bromine in 2 mL of glacial
acetic acid. The resulting solution was stirred at room
temperature overnight. The mixture was cooled with an ice bath,
treated with 56 mL of 5 N sodium hydroxide solution and
extracted with dichloromethane (5 × 50 mL). The organic phases
were washed with 50 mL of 0.5 N sodium thiosulfate solution
and 50 mL of water, dried (sodium sulfate), and filtered.
Evaporation of the solvent left 4.89 g of crude product, which
was absorbed onto 30 g of silica gel and Soxhlet extracted
overnight into chloroform. Evaporation of the solvent gave 2.77
g (59%) of product (14); 1H nmr (deuteriochloroform) δ 2.13 (s,
3H), 2.44 (s, 3H), 4.53 (br s, 2H), 8.19 (s, 1H).
4-Amino-5,6-dimethyl-3-(methylamino)pyridine (15). In a
sealed stainless steel bomb under argon, a suspension of 1.66 g
of crude (90% pure, 7.43 mmoles) 4-amino-5-bromo-2,3-
dimethylpyridine (14) and 102 mg (0.41 mmoles) of copper
sulfate pentahydrate in 10 mL of 40% methylamine solution was
heated to 195-200° for 3 hours. The reaction bomb was cooled
to 0°, opened, and the contents treated with 50 mL of ice-cold
10% sodium hydroxide solution. The mixture was extracted with
chloroform (3 × 50 mL), dried (sodium sulfate), and filtered.
Evaporation of the solvent left 1.19 g of crude material, which
was Kugelrohr distilled to give 158 mg (10%) of 70% pure
product (15); bp 95-105° at 2 mm of mercury; 1H nmr
(deuteriochloroform) δ 1.96 (s, 3H), 2.30 (s, 3H), 3.37 (s, 3H),
4.70-4.90 (m, 3H), 7.93 (s, 1H).
1
of desired product (8); H nmr (deuteriochloroform) δ 2.17 (s,
3H), 2.34 (s, 3H), 3.03 (d, 3H, J = 4.86 Hz), 6.69 (br s, 1H), 8.06
(s, 1H); 13C nmr (deuteriochloroform) 16.25, 16.68, 28.40,
121.31, 143.34, 151.33, 152.21, 152.40.
3-Amino-4,5-dimethyl-2-(methylamino)pyridine (9).
A
solution of 620 mg (3.4 mmoles) of 4,5-dimethyl-2-(methyl-
amino)-3-nitropyridine (8) in 150 mL of ethanol was hydro-
genated for 2 hours at 50 psi in the presence of 62 mg of 10%
palladium on carbon at room temperature. The reaction mixture
was filtered through Celite, washing cake with ethanol and then
evaporating to give 514 mg (100%) of product (9); 1H nmr
(deuteriochloroform) δ 2.05 (s, 3H), 2.12 (s, 3H), 2.95 (s, 3H),
3.65 (br s, 3H), 7.56 (s, 1H).
2-Amino-3,6,7-trimethyl-3H-imidazo[4,5-b]pyridine
(1).
To 514 mg (3.4 mmoles) of 3-amino-4,5-dimethyl-2-(methyl-
amino)pyridine (9) dissolved in 6 mL of ethanol was added 1.09
g (10.3 mmoles) of cyanogen bromide. The mixture was heated
for 12 hours in a Teflon-lined bomb submerged in an oil bath set
to 120˚. The cooled material was passed through a plug of C18
reverse phase silica gel eluting with 50 mL of 5% aqueous
ammonia, followed by 150 mL of water, then 100 mL of
methanol. The concentrated methanol eluent was then purified
on a preparative HPLC C18 reverse phase silica gel column
eluting with 40:60:0.5 methanol:water:triethylamine to give 127
mg (21%) of desired final product (1); melting range 220-280°
1
(dec); H nmr (deuteriodimethylsulfoxide) δ 2.20 (s, 3H), 2.28
(s, 3H), 3.45 (s, 3H), 6.62 (br s, 2H), 7.64 (s, 1H); 13C nmr
(deuteriodimethylsulfoxide)) δ 12.45, 15.83, 26.84, 124.30,
129.77, 134.70, 137.74, 145.98, 155.28; ir (potassium bromide)
3264, 3051, 1668, 1615, 1551, 1488, 1400, 1353, 1238, 1173,
3-Bromo-5,6-dimethyl-4-nitropyridine (16). A suspension
of 6.5 g (32.3 mmoles) of 4-amino-3-bromo-5,6-dimethyl-
pyridine (14) in 25 mL of concentrated sulfuric acid was heated
to 90˚. To the reaction was added 6.6 g (194 mmoles) of 70%
hydrogen peroxide solution dropwise over 30 minutes. The
mixture was cooled, diluted with 100 mL of water, then
neutralized with 10% sodium carbonate solution, extracted into
chloroform, dried (sodium sulfate), filtered, and evaporated.
Silica gel chromatography eluting with 20% ethyl acetate/80%
1127, 1023 cm-1; uv (95% ethanol) λ
296 nm (ε 13,784), 256
max
(6,284), 208 (22,745); ms (70 eV, electron impact) m/z (relative
intensity) 176 (100, molecular ion), 161 (30), 148 (17), 134 (6),
107 (7), 92 (6), 80 (7), 65 (26), 53 (25), 42 (37); hrms: Calcd.
for C9H12N4: 176.1062. Found: 176.1065.
2-Amino-3,4-dimethylpyridine (10) and 2-Amino-4,5-
dimethylpyridine (11). To 30.0 g (280 mmoles) of 3,4-
dimethylpyridine (5) was added 42.0 g (560 mmoles) of 50%
sodium amide in anhydrous toluene. The reaction mixture was
heated at 180° for 24 hours under argon. To the cooled mixture
was added 100 mL of water dropwise. After evolution of gas
ceased, the mixture was extracted with ethyl acetate (3 x 150
mL), dried (sodium sulfate), filtered, and concentrated. The
black oil was vacuum distilled at 0.6 mm of mercury to afford
12.30 g (36%) of a 4:1 mixture of 2-amino-3,4-dimethylpyridine
(10) and 2-amino-4,5-dimethylpyridine (11); 1H nmr
(deuteriochloroform) δ 2.09 (s, 3H), 2.15 (s, 3H), 4.26 (br s,
2H), 6.32 (s, 1H), 7.78 (s, 1H).
1
hexanes gave 2.4 g (32%) of product (16) as a yellow solid; H
nmr (deuteriochloroform) δ 2.24 (s, 3H), 2.55 (s, 3H), 8.56 (s,
1H); 13C nmr (deuteriochloroform) δ 14.02, 22.85, 106.94,
123.71, 149.47, 159.26; ms (DCI) mz (relative intensity)
233/231 (100, molecular ion, H+), 219/217 (10), 203/201 (15),
153 (15), 123 (8).
3-Bromo-5,6-dimethyl-4-(methylamino)pyridine (17). To
207 mg (0.89 mmoles) of 3-bromo-5,6-dimethyl-4-nitropyridine
(16) and 6 mL of 40% aqueous methylamine was added 2 mL of
ethanol and the reaction mixture was heated to 70˚ for 1 hour.
The reaction mixture was cooled, then extracted into 25 mL of
chloroform, dried (sodium sulfate), filtered, and evaporated to
2-Amino-4,5-dimethyl-3-nitropyridine (12). A 1.9:1
mixture of 2-amino-3,4-dimethylpyridine (10) and 2-amino-4,5-
dimethylpyridine (11) (965 mg, 7.91 mmoles) was dissolved in 3
mL of concentrated sulfuric acid and treated with 799 mg of
potassium nitrate (7.91 mmoles). The mixture was stirred at
room temperature for 3 hours and at 100° for 1 hour. After
cooling, the mixture was poured onto 30 g of ice, neutralized
with sodium bicarbonate, extracted into ethyl acetate (3 × 75
mL), dried (sodium sulfate), filtered, and concentrated. The
1
give 185 mg (97%) of product (17); H nmr (deuteriochloro-
form) δ 2.22 (s, 3H), 2.39 (s, 3H), 2.95 (d, 3H, J = 4.41 Hz),
4.23 (br s, 1H), 8.19 (s, 1H); 13C nmr (deuteriochloroform) δ
15.62, 22.96, 34.80, 110.12, 120.48, 147.59, 152.60, 157.20.
5,6-Dimethyl-3-(methylamino)-4-nitropyridine (18).
A
solution of 2.90 g (29.3 mmoles) of copper(I) chloride and 200
mg (1.47 mmoles) of copper(II) chloride in 50 mL of 40%

May-Jun 2008
Synthesis of Two Potential Heterocyclic Amine Food Mutagens
665
aqueous ammonia solution was added to a solution of 3.4 g (14.7
mmoles) of 3-bromo-5,6-dimethyl-4-nitropyridine (16) in 15 mL
of ethanol. The resulting solution was allowed to stir for 24
hours at room temperature, then extracted into chloroform (2 x
20 mL), dried (sodium sulfate), filtered, and evaporated. Silica
gel chromatography eluting with 5% methanol/95% chloroform
No. PO1-CA55861. We would also like to thank Mr. M. G.
Knize, Lawrence Livermore National Laboratory, Biomedical
Sciences Division, University of California, for his assistance.
REFERENCES AND NOTES
1
gave 935 mg (35%) of product (18) as a yellow solid; H nmr
[1] Skog, K.; Johansson, M.; Jägerstad, M. Food Chem. Toxicol.
1998, 36, 879.
(deuteriochloroform) δ 2.28 (s, 3H), 2.48 (s, 3H), 2.96 (d, 3H, J
= 5.19 Hz), 5.13 (br s, 1H), 8.07 (s, 1H); ms (70 eV, electron
impact) m/z (relative intensity) 181 (75, molecular ion, H+), 164
(20), 146 (12), 135 (8), 119 (15), 106 (25), 93 (20), 79 (40), 65
(75), 52 (70), 42 (100);
[2] Jägerstad, M.; Skog, K. Mutation Res. 2005, 574, 156.
[3] Knize, M. G.; Felton, J. S. Nutrition Rev. 2005, 63, 158.
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Cancer Sci. 2004, 95, 290.
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M. E. Environ. Mol. Mutagen. 2006, 47, 132.
2-Amino-3,6,7-trimethyl-3H-imidazo[4,5-c]pyridine (2). A
solution of 307 mg (1.7 mmoles) of 5,6-dimethyl-3-(methyl-
amino)-4-nitropyridine (18) in 30 mL of ethanol was
hydrogenated for 18 hours at 50 psi of hydrogen in the presence
of 30 mg of 10% palladium on carbon at room temperature. The
reaction mixture was filtered through Celite, rinsing the cake
with ethanol, then concentrated. Added to the resulting material
dissolved in 6 mL of ethanol was 540 mg (5.1 mmoles) of
cyanogen bromide. The mixture was heated for 12 hours in a
Teflon-lined bomb submerged in an oil bath set to 120˚. The
resulting material was applied to a plug of C18 reverse phase
silica gel and eluted with 50 mL of 10% aqueous ammonia
solution, followed by 100 mL of water, then 100 mL of
methanol. The methanol eluent was concentrated and then
triturated with isopropanol (3 x 3 mL) to give 66 mg (22%) of
1
desired product (2) as a light brown solid; mp >300° (dec); H
nmr (deuteriomethanol) δ 2.40 (s, 3H), 2.53 (s, 3H), 3.61 (s,
3H), 8.15 (s, 1H); 13C nmr (deuteriomethanol) δ 11.76, 19.26,
29.03, 117.30, 121.18, 131.02, 144.27, 151.06, 159.21; ir
(potassium bromide) 3107, 1661, 1549, 1478, 1443, 1261, 1167,
1114, 761 cm-1; uv (95% ethanol) λmax 265 nm (ε 8,273), 215
(32,820); ms (70 eV, electron impact) m/z (relative intensity)
176 (100, molecular ion), 161 (37), 134 (7), 107 (12), 93 (17),
80 (72), 66 (17), 53 (21), 42 (40); hmrs Calcd. for C9H12N4;
176.1062. Found: 176.1067.
[16] Tanga, M. J.; Bupp, J. E.; Tochimoto, T. K. J. Heterocyclic
Chem. 1994, 31, 1641.
[17] Tanga, M. J.; Bupp, J. E.; Tochimoto, T. K. J. Heterocyclic
Chem. 1997, 34, 717.
Acknowledgment. This work was supported by the National
Cancer Institute under Contract No. N01-CB-67257 and Grant
[18] Tanga, M. J.; Bradford, W. W.; Bupp, J. E.; Kozocas, J. A. J.
Heterocyclic Chem. 2003, 40, 569.