Synthesis of halogen-substituted 3-deazaadenosine and 3-deazaguanosine analogues as potential antitumor/antiviral agents

Article abstract of DOI:10.1081/NCN-100108327

Various 2-halogen-substituted analogues (38, 39, 43 and 44), 3-halogensubstituted analogues (51 and 52), and 2′,3′ -dihalogen- substituted analogues (57-60) of 3-deazaadenosine and 3-halogen-substituted analogues (61 and 62) of 3-deazaguanosine have been synthesized as potential anticancer and/or antiviral agents. Among these compounds, 3-deaza-3-bromoguanosine (62) showed significant cytotoxicity against L1210, P388, CCRF-CEM and B₁₆F₁₀ cell lines in vitro, producing IC₅₀ values of 3, 7, 9 and 7μM, respectively. Several 3-deazaadenosine analogues (38, 51, 57 and 59) showed moderate to weak activity against hepatitis B virus.

Full text of DOI:10.1081/NCN-100108327

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SYNTHESIS OF HALOGEN-SUBSTITUTED 3-
DEAZAADENOSINE AND 3-DEAZAGUANOSINE ANALOGUES
AS POTENTIAL ANTITUMOR/ANTIVIRAL AGENTS
Mao-Chin Liu a , Mei-Zhen Luo a , Diane E. Mozdziesz a , Tai-Shun Lin† a , Ginger E.
Dutschman a , Elizabeth A. Gullen a , Yung-Chi Cheng a & Alan C. Sartorelli b
a Department of Pharmacology and Developmental Therapeutics Progam, Cancer Center,
Yale University School of Medicine, New Haven, Connecticut, 06520-8066, U.S.A.
b Department of Pharmacology and Developmental Therapeutics Progam, Cancer Center,
Yale University School of Medicine, New Haven, Connecticut, 06520-8066, U.S.A.
Available online: 17 Aug 2006
To cite this article: Mao-Chin Liu, Mei-Zhen Luo, Diane E. Mozdziesz, Tai-Shun Lin† , Ginger E. Dutschman, Elizabeth A.
Gullen, Yung-Chi Cheng & Alan C. Sartorelli (2001): SYNTHESIS OF HALOGEN-SUBSTITUTED 3-DEAZAADENOSINE AND 3-
DEAZAGUANOSINE ANALOGUES AS POTENTIAL ANTITUMOR/ANTIVIRAL AGENTS, Nucleosides, Nucleotides and Nucleic Acids,
20:12, 1975-2000
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NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS, 20(12), 1975–2000 (2001)
SYNTHESIS OF HALOGEN-SUBSTITUTED
3-DEAZAADENOSINE AND
3-DEAZAGUANOSINE ANALOGUES AS
POTENTIAL ANTITUMOR/ANTIVIRAL AGENTS
Mao-Chin Liu, Mei-Zhen Luo, Diane E. Mozdziesz, Tai-Shun Lin,{
Ginger E. Dutschman, Elizabeth A. Gullen, Yung-Chi Cheng, and
Alan C. Sartorelli*
Department of Pharmacology and Developmental Therapeutics
Progam, Cancer Center, Yale University School of Medicine, New
Haven, Connecticut 06520-8066, USA
ABSTRACT
Various 2-halogen-substituted analogues (38, 39, 43 and 44), 3-halogen-
substituted analogues (51 and 52), and 20,30-dihalogen-substituted ana-
logues (57–60) of 3-deazaadenosine and 3-halogen-substituted analogues
(61 and 62) of 3-deazaguanosine have been synthesized as potential an-
ticancer and=or antiviral agents. Among these compounds,
3-deaza-3-bromoguanosine (62) showed significant cytotoxicity against
L1210, P388, CCRF-CEM and B16F10 cell lines in vitro, producing IC50
values of 3, 7, 9 and 7 mM, respectively. Several 3-deazaadenosine ana-
logues (38, 51, 57 and 59) showed moderate to weak activity against
hepatitis B virus.
Considerable progress has been made in the search for novel nucleoside
structures with anticancer and=or antiviral activity by modifications in the
base portion of the molecule. For example, 3-deazaadenosine1–3, a potent
inhibitor of adenosylhomocysteine hydrolase4, showed significant activity
{Deceased.
*Corresponding author.
1975
Copyright # 2001 by Marcel Dekker, Inc.
www.dekker.com

1976
LIU ET AL.
against herpes simplex type-15, human immunodeficiency virus6 and onco-
genic DNA viruses7,8. 3-Deazaguanosine has been reported to possess broad
spectrum antiviral activity against a variety of DNA and RNA viruses, as
well as antitumor activity against the L1210 leukemia and several mammary
adenocarcinomas in mice9–11. Certain 2-halogen-substituted purine nucleo-
sides have exhibited cytotoxicity in vitro and anticancer activity in vivo12–15
.
Among these analogues, Fludarabine phosphate (9-b-D-arabinofuranosyl-2-
fluoroadenine 50-O-phosphate) and Cladribine (2-chloro-20-deoxy-b-D-ade-
nosine) are currently used as anticancer agents. On the basis of these findings,
we chose to prepare a series of halogen-substituted analogues of 3-deazaa-
denosine and 3-deazaguanosine, which combine the structural features of 3-
deazapurine nucleosides and halogen-substituted purine nucleosides. In this
report, we describe the synthesis and biological evaluation of these nucleoside
analogues.
CHEMISTRY
The halogen-substituted 4-aminopyridines were synthesized as depicted
in Scheme 1. Treatment of commercially available 3-chlorotetra-
fluoropyridine (1) and 3,5-dichlorotrifluoropyridine (4) with ammonium
hydroxide at room temperature gave almost quantitatively 4-amino-3-chloro-
2,5,6-trifluoropyridine (2) and 4-amino-3,5-dichloro-2,6-difluoropyridine (5),
respectively16. Catalytic hydrogenation of 2 afforded 4-amino-2,3,6-tri-
fluoropyridine (3) in high yield. Catalytic hydrogenation of 5 was reported to
give 4-amino-2,6-difluoropyridine (7)17; however, when the reaction was
stopped at an early stage, a mixture of 4-amino-3-chloro-2,6-difluoropyridine
(6) and 7 were produced, which was easily separated by flash silica gel col-
umn chromatography.
2-Chloro-5-fluoropyridine (9), a highly volatile substance, was synthe-
sized from thermolysis of 2-chloro-5-pyridinediazonium tetrafluoroborate
(8)18. The isolation of 9 by the literature procedure was very complicated, in
that it included repeated extractions, repeated distillations, treatment with
sulfuric acid and sodium hydroxide, and steam distillation. In our hands, the
reported yield of 70% was difficult to obtain after these operations. To im-
prove upon these complicated procedures, following the thermolysis of
compound 8, the reaction mixture was directly treated with 50% hydrogen
peroxide and trifluoroacetic acid to give 2-chloro-5-fluoropyridine-N-oxide
(10), which was easily isolated, with a total yield of 73%. Nitration of 10,
followed by catalytic hydrogenation of the resulting 2-chloro-5-fluoro-4-
nitropyridine-1-oxide (11) removed the N-oxide function, as well as reduced
the nitro group to give the desired 4-amino-2-chloro-5-fluoropyridine (12).
N-Oxidation of commercially available 2,5-dichloropyridine (13), followed
by nitration and reduction yielded 4-amino-2,5-dichloropyridine (16).

ANTITUMOR=ANTIVIRAL AGENTS
1977
Scheme 1.
Various halogen-substituted imidazo[4,5-c]pyridines (32–36) were synthe-
sized from the corresponding halogen-substituted 4-pyridinamines according
to methodology similar to that reported by Rousseau and Robins19 for the
synthesis of 4,6-dichloroimidazo[4,5-c]pyridine, with modifications as
illustrated in Scheme 2. Nitration of compounds 3, 6, 7, 12 and 16 with
potassium nitrate in sulfuric acid gave the respective 4-nitraminopyridines
(17–21). Rearrangement of compounds 17–21 in concentrated sulfuric acid
produced the respective 4-amino-3-nitropyridine derivatives 22–26. Catalytic
hydrogenation of 22–26 in the presence of Raney nickel afforded the

1978
LIU ET AL.
Scheme 2.
corresponding 3,4-diaminopyridine derivatives 27–31. Ring closure of com-
pounds 27–31 by reaction with diethoxymethyl acetate gave the desired ha-
logen-substituted imidazo[4,5c]pyridines 32–3620 and N-1 substituted
compounds 32a–36a which were separated by silica gel column chromato-
graphy; these by-products were easily converted back to compounds 32–36
by reaction with trimethylsilyl trifluoromethanesulfonate. The synthesis of
4,6-difluoroimidazo[4,5-c]pyridine (34) has been previous reported by a dif-
ferent synthetic route; however, this method was rather lengthy and the
overall yield was quite low20.
Treatment of 4,6-difluoroimidazo[4,5-c]pyridine (34) with excess hex-
amethyldisilazane and a catalytic amount of ammonium sulfate gave
the trimethylsilyl derivative, which was treated with 1-O-acetyl-2,3,5-
tri-O-benzoyl-b-D-ribofuranose in 1,2-dichloroethane using trimethylsilyl
trifluoromethanesulfonate (TMSOTf) as a catalyst at room temperature to
give the tribenzoyl-protected nucleoside derivative 37 (Scheme 3). Treatment
of 37 with either saturated ethanolic ammonia or 40% methylamine removed
the protecting groups and displaced the 4-fluoro group in one step to produce

ANTITUMOR=ANTIVIRAL AGENTS
1979
Scheme 3.

1980
LIU ET AL.
the respective target nucleosides 38 and 39. Refluxing of silylated 34 with
2,3,5-tri-O-benzyl-1-O-(4-nitro-benzoyl)-D-arabinofuranose in 1,2-dichloroe-
thane in the presence of TMSOTf under nitrogen afforded a mixture of a-
and b-nucleosides 40. Treatment of 40 with ammonia saturated ethanol gave
the 4-amino-6-fluoro-1-(2,3,5-tri-O-benzyl-b-D-arabinofuranosyl)imidazo[4,
5-c]pyridine (41) and its a-analogue 42, which were separated by silica gel
chromatography. Debenzylation of 41 and 42 with palladium (II) oxide hy-
drate and cyclohexene in ethanol afforded the target compound 43 and its a-
analogue 44.
The assignment of the anomeric configurations of these nucleosides
(41–44) was made on the basis of the characteristics of the proton NMR
spectra (Table 1). The 40-Hprotons of the a-anomers appear at a lower
field than those of the b-anomers. Conversely, the 50-Hprotons of the a-
anomers appear at a higher field than those of the b-anomers. These shifts
are attributed to the fact that protons at the syn-position relative to the
base are more deshielded than those in the anti-position relative to the base.
The 40-Hprotons of the a-anomers and the bases are on the same side of
the sugar ring and those of b-anomers are on the opposite side. In contrast,
the 50-Hprotons of the a-anomers and the bases are on the opposite side of
the sugar ring and those of b-anomers are on the same side. The findings
are consistent with reports by others with both pyrimidine and purine
nucleosides21–23
.
The synthesis of 3-halogen-substituted 3-deazaadenosine analogues 51
and 52 is shown in Scheme 4. Condensation of silylated 4-chloro-7-fluor-
oimidazo[4,5-c]pyridine (35) and silylated 4,7-dichloroimidazo[4,5-c]pyridine
(36) with 1-O-acetyl-2,3,5-tri-O-benzoyl-b-D-ribofuranose in 1,2-dichloroe
thane in the presence of TMSOTf gave the 3-deaza-3-halogen-substituted
purine nucleosides 45 and 46, respectively. Deblocking of 45 and 46 with
sodium methoxide in methanol yielded the corresponding nucleoside deri-
vatives 47 and 48. Attempts at conversion of the 4-chloro substituents on 45
Table 1. Proton NMR Chemical Shifts d (ppm)
Compound
40-Ha
Dd
50-Ha
Dd
41 (b)b
4.10 (anti)
3.70 (syn)
0.15
0.29
0.12
0.13
42 (a)b
43 (b)c
4.25 (syn)
3.73 (anti)
3.58 (anti)
3.65 (syn)
44 (a)c
4.02 (syn)
3.52 (anti)
a
b
stereochemistry relative to the base. spectra were recorded in CDCl3; in DMSO-d6.
c

ANTITUMOR=ANTIVIRAL AGENTS
1981
Scheme 4.
and 46 to the corresponding amino functions by either ammonia saturated
ethanol or liquid ammonia at various temperatures were unsuccessful and
resulted in either a decomposed by-product or recovery of the starting ma-
terial. However, treatment of 47 and 48 with anhydrous hydrazine24, fol-
lowed by catalytic hydrogenation of compounds 49 and 50 with Raney
nickel furnished 51 and 52.
The synthesis of 2,3-dihalogen-substituted 3-deazaadenosine analogues
57–60 is depicted in Scheme 5. Condensation of silylated 4,6,7-trifluo
roimidazo[4,5-c]pyridine (32) and silylated 7-chloro-4,6-difluoroimidazo
[4,5-c]pyridine (33) with 1-O-acetyl-2,3,5-tri-O-benzoyl-b-D-ribofuranose in
1,2-dichloroethane in the presence of TMSOTf gave the corresponding
protected 1-ribosides 53 and 55, and 3-ribosides 54 and 56. Treatment of
compounds 53–56, with ammonia saturated ethanol afforded the respective
target compounds 57–60. The assignment of the N-glycosidic linkage of the
N1- and N3-isomers of compounds 57–60 was based upon the UV spectra
of these derivatives. The UV spectra of the N1-3-deazapurine nucleoside

1982
LIU ET AL.
Scheme 5.
isomers showed a maximum peak at 274 nm (57 and 59), while the N3-
isomers showed a maximum peak at 292 nm (58 and 60). Furthermore,
the NMR spectra of the 2-Hprotons of the N3-isomers were downfield
from those of the corresponding N1-isomers. For example, the chemical
shifts of the 2-Hprotons of the N3-isomers 58 and 60 appeared at 8.54
and 8.55 ppm and for the N1-isomers 57 and 59 at 8.43 and 8.51 ppm,
respectively. These results are similar to those obtained with other 3-dea-
zapurine nucleosides25,26
.
The synthesis of 3-deaza-3-halogen-substituted 3-deazaguanosine ana-
logues is illustrated in Scheme 6. Halogenation of 3-deazaguanosine, which
was synthesized by a known procedure11,27, with N-chlorosuccinimide in
water and bromine-water, respectively, gave the corresponding 3-deaza-3-
chloroguanosine (61) and 3-deaza-3-bromoguanosine (62).

ANTITUMOR=ANTIVIRAL AGENTS
1983
Scheme 6.
BIOLOGICAL EVALUATION
The synthesized compounds were evaluated in vitro for their cyto-
toxicity against the L1210 and P388 leukemias, the CCRF-CEM lym-
phoblastic leukemia, and the B16F10 melanoma cell lines and the results are
shown in Table 2. Among these compounds, 3-deaza-3-chloroguanosine
(61) showed activity with IC50 values of 12, 40, 30 and 35 mM and 3-
deaza-3-bromoguanosine (62) produced IC50 values of 3, 7, 9 and 7 mM
against L1210, P388, CCRF-CEM and B16F10 cells, respectively. The ha-
logen-substituted 3-deazaadenosine derivatives 38, 51, 57 and 59 showed
moderate to weak activities, and the other compounds had only slight or
no activity in concentrations up to 100 mM against these neoplastic cell
lines.
Antiviral assays were performed against hepatitis B virus (HBV) and
human immunodeficiency virus (HIV-IIIB) in vitro as previously described28.
Among these compounds, 3-deaza-3-chloro-2-fluoroadenosine (59), 3-deaza-
3-fluoroadenosine (51) and 4-amino-6,7-difluoro-3-(b-D-ribfuranosyl)imida
zo[4,5c]pyridine (58) showed moderate activity against HBV with EC50

1984
LIU ET AL.
Table 2. Evaluation of the Cytotoxicity of Halogen-Substituted 3-Deazaadenosine and 3-
Deazaguanosine Analogues Against L1210, P388, CCRF-CEM, and B16F10 Cell Lines In
Vitro
IC50(mM)a
Compound
L1210
P388
CCRF-CEM
B16F10
38
39
35
> 100
50
> 100
100
100
40
> 100
43
44
> 100
> 100
> 100
> 100
> 100
> 100
> 100
> 100
51
52
15
> 100
100
> 100
60
> 100
45
> 100
57
58
90
> 100
90
> 100
40
> 100
100
> 100
59
60
55
> 100
90
> 100
60
> 100
100
> 100
61
62
12
3
40
7
30
9
35
7
a IC50 values represent the drug concentration (mM) required to inhibit cancer cell replication
by 50%. The compounds were tested up to a concentration of 100 mM.
values of 7.5, 9.2 and 10 mM, respectively. The remaining compounds showed
little or no activity against HBV and HIV-IIIB up to their maximum tested
concentrations of 10 and 100 mM, respectively.
EXPERIMENTAL SECTION
Melting points were determined with a Thomas-Hoover Unimelt ap-
1
paratus and are uncorrected. HNMR spectra were recorded on a Varian
EM-390 (90 MHz) or Gemini-300 (300 MHz) NMR spectrometer with
Me4Si as the internal reference. The UV spectra were recorded on a Beck-
man-25 spectrophotometer. Mass spectra were recorded on a VG-ZAB-SE
mass spectrometer in the fast bombardment (FAB) mode (glycerol matrix).
Column chromatography was conducted with Merck silica gel 60, 230–400
mesh. TLC was performed on EM precoated silica gel sheets containing a
fluorescent indicator. Elemental analyses were carried out by the Baron
Consulting Co., Orange, CT, USA.
4-Amino-3-chloro-2,5,6-trifluoropyridine(2). This compound was pre-
pared by a modification of the procedure of Chambers et al.16 A mixture of

ANTITUMOR=ANTIVIRAL AGENTS
1985
3-chloro-2,4,5,6-tetrafluoropyridine (1, 37.4 g, 201 mmol) and 150 mL of
28% ammonium hydroxide was stirred at room temperature for 5 h. The
resulting white crystals were collected and carefully washed with ice water to
give 2 as a white solid (35 g). The combined filtrate and washings were
extracted with ether. The ether extract was dried (MgSO4), filtered and
evaporated in vacuo to give additional 2 (1.3 g); total yield: 26.3 g (99%).
The product was used directly for the next step in the reaction. A small
sample was purified by silica gel column chromatography: mp 118-120ꢀC
(Lit.16 mp 117-118ꢀC).
4-Amino-3,5-dichloro-2,6-difluoropyridine(5).
This compound was
prepared from 3,5-dichloro-2,4,6-trifluoropyridine (24.5 g) by a procedure
similar to that described for compound 2: yield, 23.7 g (98%); mp 110ꢀC
(Lit16. mp 112–113ꢀC).
4-Amino-2,3,6-trifluoropyridine(3). A suspension of 4-amino-3-chloro-
2,5,6-trifluoropyridine (2, 19.7 g, 108 mmol), 10% Pd=C (1.8 g) and trie-
thylamine (20 mL, 140 mmol) in 150 mL of anhydrous ethanol was hydro-
genated at 50 psi in a Parr hydrogenation apparatus until TLC showed the
reaction was completed (ꢁ 18 h). The catalyst was removed by filtration and
carefully washed with ethanol. The combined filtrate and washings were
evaporated to dryness in vacuo. The residue was stirred with 80 mL of water
for 1 h, filtered, and washed with water to give 3 (14 g) as a white solid. The
filtrate and washings were combined and extracted with ether. The combined
ether layers were then dried (MgSO4) and concentrated to give an additional
1.3 g of 3 (total yield: 15.3 g, 96%). A small analytical sample was purified
1
by silica gel column chromatography (Rf 0.47, CH2Cl2): mp 94–96ꢀC; H
NMR (CDCl3) d 4.78 (br s, 2 H, 4-NH2, D2O exchangeable), 6.20 (d, 1 H, 5-
H). Anal. Calcd. for C5H3F3N2: C, 40.55; H, 2.04; N, 18.92. Found: C,
40.60; H, 2.16; N, 18.67.
4-Amino-3-chloro-2,6-difluoropyridine(6) and 4-amino-2,6-difluoropyri-
dine(7). A suspension of 19.9 g (100 mmol) of 5, 2.2 g of 10% Pd=C and
27 mL (190 mmol) of triethylamine in 100 mL of anhydrous ethanol was
hydrogenated at 50 psi in a Parr hydrogenation apparatus overnight (ꢁ 18 h).
The catalyst was filtered and carefully washed with ethanol. The combined
filtrate and washings were evaporated to dryness in vacuo. The residue was
partitioned between ether and water, and the water layer was extracted with
ether. The combined ether layers were dried (MgSO4) and concentrated to
dryness. The residue was dissolved in ethanol and the solution was treated
with 50 g of silica gel. The solvent was removed in vacuo to give a powder,
which was purified by silica gel column chromatography, eluted with CH2Cl2
to afford 9.4 g (57%) of 6 and 4.3 g (33%) of 7.
Compound 6 was isolated as a white solid: mp 84–85ꢀC; TLC, Rf 0.55
1
(CH2Cl2); HNMR (CDCl ) d 5.15 (br s, 2 H, NH2, D2O exchangeable),
3

1986
LIU ET AL.
6.20 (s, 1 H, 5-H). Anal. Calcd. for C2H3ClF2N2: C, 36.49; H, 1.84; N, 17.02.
Found: C, 36.78; H, 2.09; N, 16.89.
Compound 7 was isolated as a white solid: mp 126–128ꢀC (Lit.14 mp
1
125–127ꢀC); TLC, Rf 0.37 (CH2Cl2); HNMR (DMSO- d6) d 6.00 (s, 2 H,
3- and 5-H), 6.70 (br s, 2H, NH2, D2O exchangeable). Anal. Calcd. for
C5H4F2N2: C, 46.16; H, 3.10; N, 21.54. Found: C, 46.01; H, 3.39; N,
21.29.
2-Chloro-5-fluoropyridine-1-oxide (10). A suspension of 2-chloro-5-
pyridinediazonium tetrafluoroborate18 (8, 7.6 g, 33.4 mmol) in dry heptane
(50 mL) was heated to 105ꢀC (oil bath temperature) for 2 h. A rapid evo-
lution of nitrogen was observed after 10–15 min, which lasted for about
30 min. The reaction mixture formed two layers: the clear upper heptane
layer and the blackened dark lower layer. The temperature was then lowered
to 70ꢀC, and 100 mL of trifluoroacetic acid and 11 mL of 50% hydrogen
peroxide were subsequently added from the top of the condenser. The
reaction mixture was stirred at 70–75ꢀC until TLC showed that the reaction
was complete (ꢁ20 h). The lower dark layer gradually changed to a clear
orange solution during the reaction process. The two-layer mixture was
evaporated to dryness in vacuo and co-evaporated with toluene (50 mL). To
the residue were added 20 mL of water and 100 mL of methylene chloride,
and the mixture was neutralized by dropwise addition of 28% ammonium
hydroxide solution with stirring. The aqueous layer was further extracted
with methylene chloride and the combined organic layer was dried, filtered
and evaporated to give the crude product, which was purified by silica gel
column chromatography (CH2Cl2=EtOAc, 1:1, v=v, Rf 0.23) to give 3.6 g
1
(73%) of product as a white solid: mp 98–100ꢀC; HNMR (CDCl ) d 7.15
3
(m, 1 H, 3-H), 7.60 (m, 1H, 4-H), 8.40 (dd, 1 H, 6-H, J ¼ 2:0 Hz, 8.5 Hz).
Anal. Calcd. for C5H3ClFNOÁ0.5 H2O: C, 38.36; H, 2.56; N, 8.95. Found: C,
38.13; H, 2.19; N, 8.65.
2-Chloro-5-fluoro-4-nitropyridine-1-oxide (11). 2-Chloro-5-fluoropyri
dine-N-oxide (10, 3.5 g, 23.7 mmol) was gradually added to 46 mL of con-
centrated sulfuric acid, followed by 10 g of potassium nitrate with stirring.
The reaction mixture was heated at 120ꢀC for 2 h, cooled and poured onto
160 g of crushed ice. The solution was neutralized by dropwise addition of
28% ammonium hydroxide with stirring, while the temperature was main-
tained below 15ꢀC with an ice bath. The light yellow crystals which pre-
cipitated were collected by filtration, washed with ice water, and dried to
yield 2.7 g (59%) of product. A small sample was purified by silica gel col-
umn chromatography (CH2Cl2=EtOAc, 4:1, v=v, Rf 0.71): mp 131–132ꢀC; 1H
NMR (DMSO-d6) d 8.70 (m, 1 H, 3-H), 9.12 (m, 1 H, 6-H). Anal. Calcd. for
C5H2ClFN2O3: C, 31.19; H, 1.05; N, 14.55. Found: C, 31.36; H, 1.16; N,
14.75.

ANTITUMOR=ANTIVIRAL AGENTS
1987
4-Amino-2-chloro-5-fluoropyridine(12).
A mixture of 2-chloro-5-
fluoro-4-nitropyridine-1-oxide (11, 1.3 g, 6.8 mmol) and 1.6 g of Raney
nickel in 80 mL of anhydrous ethyl alcohol was hydrogenated at 40 psi in a
Parr hydrogenation apparatus for 3 h when TLC showed that the starting
material had disappeared and a new spot was detected (CH2Cl2=EtOAc, 4:1,
v=v, Rf 0.78 and 0.71, for the starting material and the product, respectively).
The catalyst was removed by filtration and washed carefully with ethyl
alcohol. The filtrate and washings were combined and evaporated in vacuo to
give 0.9 g (91%) of product as an off-white solid. A small analytical sample
was purified by recrystallization from hot water to afford white crystals: mp
1
110–111ꢀC; HNMR (CDCl ) d 4.50 (br s, 2 H, NH2, D2O exchangeable),
3
7.15 (d, 1H, 3-H, J ¼ 6 Hz), 7.95 (d, 1H, 6-H, J ¼ 2 Hz). Anal. Calcd. for
C5H4ClFN2: C, 40.97; H, 2.75; N, 19.12. Found: C, 41.18; H, 2.39; N, 18.89.
2,5-Dichloropyridine-1-oxide (14). A mixture of 2,5-dichloropyridine
(10 g, 67 mmol), 180 mL of trifluoroacetic acid and 22 mL of 50% hydrogen
peroxide was heated at 70–75ꢀC with stirring until TLC showed the reaction
to be complete. The reaction mixture was evaporated to dryness in vacuo and
co-evaporated with water twice. The residue was stirred with 40 mL of water
and 200 mL of methylene chloride and neutralized by dropwise addition of
28% ammonium hydroxide solution. The aqueous layer was further extrac-
ted with methylene chloride and the combined organic layer was dried, fil-
tered and evaporated to give 10 g (91%) of product, which was used directly
for the next step. A small sample was purified by silica gel column chro-
1
matography (CH2Cl2=EtOAc, 10:1, v=v, Rf 0.24): mp 73–75ꢀC; HNMR
(CDCl3) d 7.13 (dd, 1 H, 4-H, J ¼ 10 Hz, 2 Hz), 7.45 (d, 1H, 3-H, J ¼ 10 Hz),
8.35 (d, 1 H, 6-H, J ¼ 2 Hz). Anal. Calcd. for C5H3Cl2NOÁ0.5 H2O: C, 36.62;
H, 1.84; N, 8.54. Found: C, 36.43; H, 2.01; N, 8.25.
Compounds 15 and 16 were synthesized by methodology similar to that
described for compounds 11 and 12, respectively.
2,5-Dichloro-4-nitropyridine-1-oxide (15). Compound 15 was isolated
as light yellow crystals (6.5 g, 50.5%): mp 137–139ꢀC; 1HNMR (DMSO- d6)
d 8.70 (s, 1 H, 3-H), 9.05 (s, 1 H, 6-H). Anal. Calcd. for C5H2Cl2N2O3: C,
28.73; H, 0.96; N, 13.41. Found: C, 28.39; H, 1.06; N, 13.55.
2,5-Dichloro-4-aminopyridine(16).
Compound 16 was isolated as a
white solid (4.0 g, 85%): mp 122–123ꢀC; 1HNMR (CDCl 3) d 4.75 (br s, 2 H,
NH2, D2O exchangeable), 6.63 (s, 1 H, 3-H), 8.05 (s, 1H, 6-H). Anal. Calcd.
for C5H4Cl2N2: C, 36.84; H, 2.47; N, 17.19. Found: C, 36.58; H, 2.30; N,
16.88.
4-Nitramino-2,3,6-trifluoropyridine(17). 4-Amino-2,4,6-trifluoropyri
dine (3, 7 g, 47.3 mmol) was carefully added to 75 mL of concentrated

1988
LIU ET AL.
sulfuric acid at 0–5ꢀC (ice-bath) with stirring to form a solution. Potassium
nitrate (10.1 g, 100 mmol) was gradually added to the solution during a
period of 20 min while the internal temperature was maintained below 5ꢀC.
The reaction mixture was further stirred at 0–5ꢀC for 1 h and at room
temperature for 15 min, then poured onto 300 g of crushed ice. The resulting
acidic solution was extracted with methylene chloride. The methylene
chloride extracts were combined, dried, filtered and concentrated to give 8 g
(88%) of product as a yellow solid. It was used directly for the next step in
the reaction without further purification. A small analytical sample was
1
purified by silica gel chromatography: mp 135–137ꢀC; HNMR (CDCl ) d
3
7.55 (d, 1 H, 3-H, J ¼ 2 Hz), 10.70 (br s, 1H, NH, D2O exchangeable). Anal.
Calcd. for C5H2F3N3O2: C, 31.10; H, 1.04; N, 21.76. Found: C, 31.23; H,
1.23; N, 21.60.
Compounds 18–21 were synthesized by methodology similar to that
described for compound 17.
3-Chloro-2,6-difluoro-4-nitraminopyridine(18).
Compound 18 was
1
isolated as a light yellow solid (10.7 g, 76.4%): mp 100–102ꢀC; HNMR
(CDCl3) d 7.62 (d, 1 H, 5-H, J ¼ 2 Hz), 10.48 (br s, 1H, NH, D2O
exchangeable). Anal. Calcd. for C5H2ClF2N3O2: C, 28.66; H, 0.96; N, 20.05.
Found: C, 29.02; H, 1.25; N, 20.40.
2,6-Difluoro-4-nitraminopyridine(19). Compound 19 was isolated as
an off-white solid (4.2 g, 76%): mp 140ꢀC (dec.); 1HNMR (CDCl 3) d 6.96 (s,
2 H, 3- and 5-H), 7.62 (br s, 1H, NH, D2O exchangeable). Anal. Calcd. for
C5H3F2N3O2: C, 34.30; H, 1.73; N, 24.00. Found: C, 34.42; H, 1.85; N, 24.05.
2-Chloro-5-fluoro-4-nitraminopyridine(20).
Compound 20 was iso-
lated as a light yellow solid (2.0 g, 83%): mp 160ꢀC (dec.); 1HNMR (CDCl 3)
d 7.90 (s, 1H, 3-H), 8.32 (d, 1H, 6-H, J ¼ 2 Hz), 12.70 (br s, 1H, NH, D2O
exchangeable). Anal. Calcd. for C5H3ClFN3O2: C, 37.17; H, 3.12; N, 26.01.
Found: C, 37.36; H, 3.16; N, 25.75.
2,5-Dichloro-4-nitraminopyridine(21). Compound 21 was isolated as a
light yellow solid (1.2 g, 65%): mp 154ꢀC (dec.) 1HNMR (DMSO- d6) d 6.90
(br s, 1H, NH, D2O exchangeable), 7.85 (s, 1H, 3-H), 8.45 (s, 1H, 6-H). Anal.
Calcd. for C5H3Cl2N3O2: C, 28.87; H, 1.45; N, 20.20. Found: C, 28.55; H,
1.26; N, 20.45.
4-Amino-3-nitro-2,5,6-trifluoropyridine(22).
4-Nitramino-2,3,6-trifluo
ropyridine (17, 9.3 g, 48 mmol) was carefully added to 70 mL of con-
centrated sulfuric acid. The mixture was stirred at room temperature over-
night (18 h), then poured onto 170 g of crushed ice with stirring. The
resulting acidic solution was mixed with 100 mL of methylene chloride and

ANTITUMOR=ANTIVIRAL AGENTS
1989
neutralized by dropwise addition of 28% ammonium hydroxide with stirring
while the internal temperature was maintained below 5ꢀC in a salted ice bath.
The organic layer was separated and the aqueous layer was extracted with
methylene chloride. The combined organic extracts were dried, filtered,
evaporated in vacuo to dryness and purified by silica gel column chroma-
tography (CH2Cl2=hexane, 1:1, v=v) to give 3.7 g (40%) of off-white crystals:
1
mp 99–100ꢀC; HNMR (CDCl ) d 6.80 (br s, 2H, 4-NH2, D2O exchange-
able). Anal. Calcd. for C5H2F3N3O2: C, 31.10; H, 1.04; N, 21.76. Found: C,
3
31.01; H, 1.34; N, 21.43.
Compounds 23–26 were synthesized by a procedure similar to that
described for compound 22.
4-Amino-3-chloro-2,6-difluoro-5-nitropyridine(23). Compound 23 was
isolated as an off-white solid (4.1 g, 82%): mp 84–85ꢀC; 1HNMR (CDCl 3) d
6.20 (br s, 2H, 4-NH2, D2O exchangeable). Anal. Calcd. for C5H2ClF2N3O2: C,
28.66; H, 0.96; N, 20.05. Found: C, 28.99; H, 0.78; N, 19.66.
4-Amino-2,6-difluoro-5-nitropyridine(24). Compound 24 was isolated
1
as an off-white solid (1.7 g, 89%): mp 149–150ꢀC (lit.20 147ꢀC); HNMR
(DMSO-d6) d 6.40 (s, 1 H, 5-H), 8.20 (br s, 2H, 4-NH2, D2O exchangeable).
4-Amino-2-chloro-5-fluoro-3-nitropyridine(25).
Compound 25 was
isolated as an off-white solid (1.7 g, 90%): mp 154–155ꢀC; 1HNMR (CDCl 3)
d 6.70 (br s, 2 H, 4-NH2, D2O exchangeable), 8.00 (d, 1 H, 6-H, J ¼ 2 Hz).
Anal. Calcd. for C5H3ClFN3O2: C, 31.35; H, 1.58; N, 21.94. Found: C, 31.55;
H, 1.60; N, 21.77.
4-Amino-2,5-dichloro-3-nitropyridine(26). Compound 26 was isolated
1
as an off-white solid (1.8 g, 97%): mp 168–170ꢀC; HNMR (DMSO- d6) d
7.45 (br s, 2H, 4-NH2, D2O exchangeable), 8.20 (s, 1 H, 6-H). Anal. Calcd.
for C5H3Cl2N3O2: C, 28.87; H, 1.45; N, 20.20. Found: C, 28.60; H, 1.31; N,
20.02.
3,4-Diamino-2,5,6-trifluoropyridine(27).
A mixture of 4-amino-3-
nitro-2,5,6-trifluoropyridine (22, 1.08 g, 5.6 mmol) and 1.5 g of Raney nickel
in 50 mL of anhydrous ethyl alcohol was hydrogenated at 36 psi in a Parr
hydrogenation apparatus for 2 h. The catalyst was removed by filtration and
washed carefully with ethyl alcohol. The filtrate and washings were combined
and evaporated in vacuo to give 0.9 g (98%) of product as an off-white solid.
A small analytical sample was purified by silica gel chromatography
(CH2Cl2=EtOH, 20:1, v=v, Rf 0.48) to give white crystals: mp 116–117ꢀC; 1H
NMR (DMSO-d6) d 3.35 (br s, 2 H, NH2, D2O exchangeable), 5.10 (br s,
2 H , NH, D2O exchangeable). Anal. Calcd. for C5H4F3N3: C, 36.82; H,
2.47; N, 25.76. Found: C, 37.20; H, 2.59; N, 25.40.
2

1990
LIU ET AL.
Compounds 28–31 were synthesized by methodology similar to that
described for compound 27.
5-Chloro-3,4-diamino-2,6-difluoropyridine(28).
Compound 28 was
isolated as a white solid (2.9 g, 92%): mp 178–179ꢀC; 1HNMR (DMSO- d6) d
3.00 (br s, 2 H, NH2, D2O exchangeable), 4.80 (br s, 2 H, NH2, D2O
exchangeable). Anal. Calcd. for C5H4Cl F2N3: C, 3.44; H, 2.24; N, 23.40.
Found: C, 33.80; H, 2.45; N, 23.03.
3,4-Diamino-2,6-difluoropyridine(29). Compound 29 was isolated as a
white solid (3.3 g, 92%): mp 135–136ꢀC (lit.17 mp 132ꢀC); 1HNMR
(DMSO-d6) d 4.23 (br s, 2 H, NH2, D2O exchangeable), 6.05 (s, 1 H, 5-H),
6.20 (br s, 2 H, NH2, D2O exchangeable). Anal. Calcd. for C5H5F2N3: C,
41.38; H, 3.47; N, 28.96. Found: C, 41.10; H, 3.68; N, 28.64.
2-Chloro-3,4-diamino-5-fluoropyridine(30).
Compound 30 was iso-
1
lated as an off-white solid (1.4 g, 94%): mp 178–179ꢀC; HNMR (DMSO-
d6) d 4.95 (br s, 2 H, NH2, D2O exchangeable), 5.80 (br s, 2 H, NH2, D2O
exchangeable), 7.42 (d, 1 H, 6-H, J ¼ 2 Hz). Anal. Calcd. for C5H5ClFN3: C,
37.17; H, 3.12; N, 26.01. Found: C, 37.36; H, 3.16; N, 25.75.
3,4-Diamino-2,5-dichloropyridine(31).
Compound 31 was isolated
as a white solid (1.9 g, 94%): mp 197–199ꢀC; 1HNMR (DMSO- d6) d 5.05 (br
s, 2 H, NH2, D2O exchangeable), 5.95 (br s, 2 H, NH2, D2O exchangeable),
7.45 (s, 1 H, 6-H). Anal. Calcd. for C5H5Cl2N3: C, 33.73; H, 2.83; N, 23.60.
Found: C, 33.60; H, 3.11; N, 23.22.
4,6,7-Trifluoroimidazo[4,5-c]pyridine (32) and 1-[(1-acetyloxy-1-ethoxy)
methyl]-4,6,7-trifluoroimidazo[4,5-c]pyridine (32a). A mixture of 3,4-dia-
mino-2,5,6-trifluoropyridine (27, 0.9 g, 5.5 mmol) and 9 mL of diethox-
ymethyl acetate was heated at 100ꢀC for 1 h with exclusion of moisture. The
reaction mixture was then evaporated to dryness in vacuo and the residue
was purified on a silica gel column, eluted with CH2Cl2=EtOAc, first (10:1,
v=v), then (1:1, v=v) to give compounds 32 (0.45 g, 47%) and 32a (0.45 g,
28%).
Compound 32 was isolated as white crystals: TLC, Rf 0.35
1
(CH2Cl2=EtOH, 20:1, v=v); mp 182–184ꢀC; HNMR (DMSO- d6) d 8.55 (s,
1 H, 2-H), 10.60 (br s, 1 H, NH, D2O exchangeable). Anal. Calcd. for
C6H2F3N3: C, 41.90; H, 1.16; N, 24.27. Found: C, 42.00; H, 1.42; N, 23.87.
Compound 32a was isolated as a syrup: TLC, Rf 0.77 (CH2Cl2=EtOAc,
10:1, v=v); 1HNMR (CDCl 3) d 1.42 (t, 3 H, CH3), 2.25 (s, 3 H, acetyl), 4.20
(m, 2 H, CH2), 7.62 (s, 1 H, CH), 8.45 (d, 1 H, 2-H); MS, m=e 290 (Mþ þ 1).
Compound 32a in methylene chloride (30 mL) was treated with trimethylsilyl
trifluoromethanesulfonate (1 mL). The mixture was stirred at room

ANTITUMOR=ANTIVIRAL AGENTS
1991
temperature overnight, then neutralized with 10% sodium bicarbonate
solution and co-evaporated with 5 g of silica gel. The residue was purified
by silica gel column chromatography to give 0.25 g of 32. The total yield of
32 was 0.7 g (74%).
Compounds 33–36 were synthesized by methodology similar to that
described for compound 32.
7-Chloro-4,6-difluoroimidazo[4,5-c]pyridine(33).
isolated as off-white crystals (2.07; g, 74%): TLC, Rf 0.45 (CH2Cl2=EtOH,
Compound 33 was
1
20:1, v=v); mp 225–227ꢀC; HNMR (DMSO- d6) d 8.50 (s, 1 H, 2-H), 10.45
(br s, 1 H, NH, D2O exchangeable). Anal. Calcd. for C6H2ClF2N3: C, 38.02;
H, 1.06; N, 22.17. Found: C, 38.33; H, 1.08; N, 21.84.
1-[(1-Acetyloxy-1-ethoxy)methyl]-7-chloro-4,6-difluoroimidazo[4,5-c]pyri
dine(33a). Compound 33a was isolated as a syrup: TLC, Rf 0.77 (CH2Cl2=
1
EtOAc, 10:1, v=v); HNMR (CDCl ) d 1.40 (t, 3 H, CH3), 2.23 (s, 3 H,
3
acetyl), 4.18 (m, 2 H, CH2), 7.58 (s, 1 H, CH), 8.42 (d, 1 H, 2-H); MS, m=e
307 (Mþ þ 1).
4,6-Difluoroimidazo[4,5-c]pyridine(34). Compound 34 was isolated as
a white solid (0.96 g, 90%): TLC, Rf 0.35 (CH2Cl2=EtOH, 20:1, v=v); mp
170–171ꢀC (lit.20 169ꢀC); 1HNMR (DMSO- d6) d 7.15 (t, 1 H, 2-H,
J ¼ 1:5 Hz), 8.40 (s, 1 H, 7-H), 12.60 (br s, 1 H, NH, D2O exchangeable).
1-[(1-Acetyloxy-1-ethoxy)methyl]-4,6-difluoroimidazo[4,5-c]pyridine
(34a). Compound 34a was isolated as
a syrup: TLC, Rf 0.84
(CH2Cl2=EtOH, 20:1, v=v); 1HNMR (CDCl 3) d 1.30 (t, 3 H, CH3), 2.20 (s, 3
H, acetyl), 3.90 (q, 2 H, CH2), 7.05 (d, 1 H, 7 H, J ¼ 2 Hz), 7.32 (s, 1 H, CH),
8.21 (d, 1 H, 2-H); MS, m=e 272 (Mþþ1).
4-Chloro-7-fluoroimidazo[4,5-c]pyridine(35).
Compound 35 was iso-
lated as white crystals (1.11 g, 80%): TLC, Rf 0.19 (CH2Cl2=EtOAc, 1:1,
v=v); mp 232–234ꢀC; 1HNMR (DMSO- d6) d 8.12 (d, 1 H, 6-H, J ¼ 2 Hz),
8.56 (s, 1 H, 2-H), 13.80 (br s, 1 H, NH, D2O exchangeable). Anal. Calcd. for
C6H3ClFN3: C, 37.17; H, 3.12; N, 26.01. Found: C, 37.36; H, 3.16; N, 25.75.
1-[(1-Acetyloxy-1-ethoxy)methyl]-4-chloro-7-fluoroimidazo[4,5-c]pyridine
(35a). Compound 35a was isolated as a syrup: TLC, Rf 0.29 (CH2
Cl2=EtOAc, 10:1, v=v); 1HNMR (CDCl 3) d 1.37 (t, 3 H, CH3), 2.20 (s, 3 H,
acetyl), 3.95 (q, 2 H, CH2), 7.57 (s, 1 H, CH), 8.15 (d, 1 H, 6-H, J ¼ 2 Hz),
8.35 (s, 1 H, 2-H); MS, m=e 289 (Mþþ1).
4,7-Dichloroimidazo[4,5-c]pyridine(36). Compound 36 was isolated as
a white solid (1.52 g, 80%): TLC, Rf 0.09 (CH2Cl2=EtOAc, 5:1, v=v); mp
1
270–272ꢀC; HNMR (DMSO- d6) d 8.25 (s, 1 H, 6-H), 8.60 (s, 1 H, 7-H),

1992
LIU ET AL.
13.60 (br s, 1 H, NH, D2O exchangeable). Anal. Calcd. for C6H3Cl2N3: C,
38.33; H, 1.61; N, 22.35. Found: C, 38.52; H, 1.90; N, 22.17.
1-[(1-Acetyloxy-1-ethoxy)methyl]-4,7-dichloroimidazo[4,5-c]pyridine
(36a). Compound 36a was isolated as
a syrup: TLC, Rf 0.58
(CH2Cl2=EtOAc, 5:1, v=v); 1HNMR (CDCl 3) d 1.32 (t, 3 H, CH3), 2.15 (s, 3
H, acetyl), 4.10 (m, 2 H, CH2), 7.95 (s, 1 H, CH), 8.25 (s, 1 H, 2-H), 8.44 (s, 1
H, 6-H); MS, m=e 304 (Mþþ1).
4,6-Difluoro-1-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)imidazo[4,5-c]pyri
dine(37). A suspension of 4,6-difluoroimidazo[4,5-c]pyridine (34, 0.34 g,
2.2 mmol) in hexamethyldisilazane (10 mL) and ammonium sulfate (a cata-
lytic amount) was refluxed for 2 h under anhydrous conditions. The resulting
clear solution was cooled and concentrated in vacuo to yield the silylated
base as a white solid, which was dissolved in 12 mL of dichloroethane. 1-O-
Acetyl-2,3,5-O-benzoyl-D-ribofuranose (1.2 g, 2.4 mmol) was added to the
solution, followed by 1 mL of TMSOTf and the reaction mixture was stirred
at room temperature under nitrogen overnight. The reaction mixture was
quenched by addition of a saturated sodium bicarbonate solution (10 mL)
and further stirred for 10 min at room temperature. The organic layer was
separated and the aqueous layer was extracted with methylene chloride
(30 mL62). The combined organic layers were washed with a saturated
sodium bicarbonate solution, then water and dried (anhydrous MgSO4).
After filtration, the filtrate was concentrated in vacuo and the residue was
purified by silica gel column chromatography (CH2Cl2=EtOAc, 30:1, v=v) to
1
yield 37 (1.0 g, 77%) as a foam: HNMR (CDCl ) d 4.62–4.82 (m, 3 H, 40-
3
and 50-H), 5.85–5.92 (m, 2 H, 20- and 30-H), 6.20 (d, 1 H, 10-H, J ¼ 5 Hz), 7.05
(d, 1 H, 7-H, J ¼ 1.5 Hz), 7.20–7.90 (m, 15 H, ArH), 8.15 (s, 1 H, 2-H). Anal.
Calcd. for C32H23F2N3O7: C, 64.10; H, 3.87; N, 7.01. Found: C, 64.28; H,
4.06; N, 6.93.
4-Amino-6-fluoro-1-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine(38).
A
suspension of 4,6-difluoro-1-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)imida
zo[4,5-c]pyridine (37, 0.6 g, 1 mmol) in 50 mL of saturated ethanolic
ammonia solution was stirred in a pressure bottle at room temperature for 4
days. The cooled reaction mixture was evaporated to dryness and the residue
was purified by silica gel column chromatography (CH2Cl2=EtOH, 10:1, v=v)
to give 0.2 g (70%) of product as a white solid: mp 171–172ꢀC; UV (MeOH)
lmax 274 nm (e 15,026), lmin 234 nm; UV (0.01 N HCl) lmax 276 nm (e
11,863), lmin 236 nm; UV (0.01 N NaOH) lmax 274 nm (e 14,027), lmin
232 nm; 1HNMR (DMSO- d6) d 3.63 (m, 2 H, 50-H), 3.94 (m, 1 H, 40-H), 4.10
(m, 1 H, 30-H), 4.28 (m, 1 H, 20-H), 5.12 [t, 1 H, 50-OH, D2O exchangeable),
5.20 (d, 1 H, OH, D2O exchangeable), 5.45 (d, 1 H, OH, D2O exchangeable),
5.71 (d, 1 H, 10-H, J ¼ 6.0 Hz), 6.55 (d, 1 H, 7-H, J ¼ 1.5 Hz), 6.55 (br s, 2 H,

ANTITUMOR=ANTIVIRAL AGENTS
1993
4-NH2, D2O exchangeable), 8.25 (s, 1 H, 2-H). Anal. Calcd. for
C11H13FN4O4: C, 46.48; H, 4.61; N, 19.70. Found: C, 46.12; H, 4.44;
N, 19.39.
6-Fluoro-4-methylamino-1-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine-(39).
A mixture of 4,6-difluoro-1-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)imidazo-
[4,5-c]pyridine (37, 0.3 g, 0.5 mmol) and 10 mL of 40% methylamine was
stirred at room temperature until TLC showed the reaction to be complete
( ꢁ 3 days). The reaction mixture was evaporated to dryness and purified by
silica gel column chromatography (CH2Cl2=EtOH, 10:1, v=v) to give 0.12 g
(77%) of product as a white solid: mp 175–177ꢀC; UV (MeOH) lmax 280 nm
(e 19,306), lmin 238 nm; UV (0.01 N HCl) lmax 282 nm (e 15,835), lmin
242 nm; UV (0.01 N NaOH) lmax 280 nm (e 18,221), lmin 238 nm; 1HNMR
(DMSO-d6) d 2.88 (d, 3 H, CH3, J ¼ 4.5), 3.62 (m, 2 H, 50-H), 3.75 (m, 1 H, 40-
H), 4.07 (m, 1 H, 30-H), 4.26 (m, 1 H, 20-H), 5.15 [t, 1 H, 50-OH, D2O
exchangeable), 5.20 (d, 1 H, OH, D2O exchangeable), 5.44 (d, 1 H, OH, D2O
exchangeable), 5.71 (d, 1 H, 10-H, J ¼ 6.3 Hz), 6.55 (d, 1 H, 7-H, J ¼ 1.5 Hz),
6.53 (br s, 1 H, 4-NHCH3, D2O exchangeable), 8.25 (s, 1 H, 2-H). Anal.
Calcd. for C12H15FN4O4: C, 48.32; H, 5.07; N, 18.78. Found: C, 47.94; H,
5.01; N, 18.39.
4-Amino-6-fluoro-1-(2,3,5-tri-O-benzyl-b-D-arabinofuranosyl)imidazo[4,
5-c]pyridine(41) and 4-amino-6-fluoro-1-(2,3,5-tri- O-benzyl-a-D-arabinofura
nosyl)imidazo[4,5-c]pyridine(42).
A mixture of 4,6-difluoroimidazo[4,5-
c]pyridine (34, 0.5 g, 3.2 mmol) and ammonium sulfate (a catalytic amount)
in hexamethyldisilazane (15 mL) was refluxed for 2 h. The resulting clear
solution was cooled and concentrated in vacuo under anhydrous conditions
to dryness. The residue was dissolved in 15 mL of dichloroethane, followed
by addition of 1-O-(4-nitrobenzoyl)-2,3,5-tri-O-benzyl-D-arabinofuranose
(2 g, 3.6 mmol) and TMSOTf (1 mL) and the reaction mixture was refluxed
with stirring under nitrogen for 2 h. The reaction mixture was cooled and
stirred with saturated sodium bicarbonate solution (15 mL) for 10 min at
room temperature. The organic layer was separated and the aqueous layer
was extracted with methylene chloride (30 mL62). The combined organic
layer was washed with saturated sodium bicarbonate solution, then water
and dried (anhydrous MgSO4). After filtration, the filtrate was concentrated
in vacuo and the residue was purified by silica gel column chromatography
(CH2Cl2=EtOAc, 20:1, v=v) to yield 40 (1.2 g, 67%) as a syrup. NMR
showed it to be a mixture of a- and b-anomers. Compound 40 (1.1 g,
2.0 mmol) was dissolved in 60 mL of ethanol, saturated with anhydrous
ammonia and heated in a stainless steel bomb at 100–105ꢀC overnight. The
reaction mixture was cooled, evaporated to dryness and separated by silica
gel column chromatography (CH2Cl2=EtOH, 20:1, v=v) to yield 41 (0.30 g,
27%), 42 (0.34 g, 31%) and a mixture of 41 and 42 (0.17 g, 15%).

1994
LIU ET AL.
Compound 41 was isolated as a white foam: TLC, Rf 0.63
(CH2Cl2=EtOH, 20:1, v=v); 1HNMR (CDCl 3) d 3.70 (m, 2 H, 50-H), 4.10 (m,
0
1 H , 4-H), 4.25 (m, 2 H, 20- and 30-H), 4.65 (s, 6 H, ArCH2), 5.75 (br s, 2 H,
NH2, D2O exchangeable), 5.96 (d, 1 H, 10-H, J ¼ 5 Hz), 6.14 (s, 1 H, 7-H),
6.80–7.40 (m, 15 H, ArH), 8.01 (s, 1 H, 2-H). Anal. Calcd. for C32H31FN4O4:
C, 69.28; H, 5.63; N, 10.10. Found: C, 69.10; H, 5.40; N, 9.96.
Compound 42 was isolated as a white foam: TLC, Rf 0.53
(CH2Cl2=EtOH, 20:1, v=v); 1HNMR (CDCl 3) d 3.58 (m, 2 H, 50-H), 4.25 (m,
0
1 H , 4-H), 4.30 (m, 2 H, 20- and 30-H), 4.50 (s, 6 H, ArCH2), 5.60 (br s, 2 H,
NH2, D2O exchangeable), 5.85 (d, 1 H, 10-H, J ¼ 5.2 Hz), 6.20 (s, 1 H, 7-H),
7.00–7.40 (m, 15 H, ArH), 7.84 (s, 1 H, 2-H). Anal. Calcd. for
C32H31FN4O4Á0.05EtOH: C, 69.01; H, 5.67; N, 10.06. Found: C, 68.87; H,
5.30; N, 9.98.
4-Amino-6-fluoro-1-b-D-arabinofuranosylimidazo[4,5-c]pyridine(43).
A
mixture of 4-amino-6-fluoro-1-(2,3,5-tri-O-benzyl-b-D-arabinofuranosyl)
imidazo[4,5-c]pyridine (41, 0.15 g, 0.27 mmol), palladium (II) oxide hydrate
(0.25 g), cyclohexene (20 mL) and ethanol (20 mL) was refluxed overnight.
The reaction mixture was cooled, filtered and washed with ethanol. The
combined filtrate and washings were evaporated in vacuo and the residue was
purified by silica gel column chromatography (CH2Cl2=EtOH, 6:1, v=v) to
give 45 mg (58%) of product as white crystals: mp 215ꢀC (dec.); UV (MeOH)
lmax 274 nm (e 14,127), lmin 234 nm; UV (0.01 N HCl) lmax 275 nm
(e 9,701), lmin 235 nm; UV (0.01 N NaOH) lmax 274 nm (e 12,595), lmin
234 nm; 1HNMR (DMSO- d6) d 3.65 (m, 2 H, 50-H), 3.73 (m, 1 H, 40-H), 4.06
(m, 1 H, 30-H), 4.15 (m, 1 H, 20-H), 5.08 [t, 1 H, 50-OH, D2O exchangeable),
5.05 (d, 1 H, OH, D2O exchangeable), 5.50 (d, 1 H, OH, D2O exchangeable),
6.08 (d, 1 H, 10-H, J ¼ 5.1 Hz), 6.42 (d, 1 H, 7-H, J ¼ 1.2 Hz), 6.59 (br s, 2
H, 4-NH2, D2O exchangeable), 8.17 (s, 1 H, 2-H). Anal. Calcd. for
C11H13FN4O4: C, 46.48; H, 4.61; N, 19.70. Found: C, 46.70; H, 5.00;
N, 19.35.
4-Amino-6-fluoro-1-a-D-arabinofuranosylimidazo[4,5-c]pyridine(44).
This compound was synthesized by a procedure similar to that described for
compound 43. Compound 44 was isolated as white crystals (60 mg, 65%):
mp 198ꢀC (dec.); UV (MeOH) lmax 272 nm (e 12,344), lmin 234 nm; UV
(0.01 N HCl) lmax 274 nm (e 10,232), lmin 234 nm; UV (0.01 N NaOH) lmax
274 nm (e 11,532), lmin 234 nm; 1HNMR (DMSO- d6) d 3.52 (m, 2 H, 50-H),
4.02 (m, 1 H, 40-H), 4.08 (m, 1 H, 30-H), 4.33 (m, 1 H, 20-H), 4.90 (t, 1 H, 50-
OH, D2O exchangeable), 5.50 (d, 1 H, OH, D2O exchangeable), 5.72 (d, 1 H,
10-H, J ¼ 5.4 Hz), 5.84 (d, 1 H, OH, D2O exchangeable), 6.41 (d, 1 H, 7-H,
J ¼ 1.5 Hz), 6.69 (br s, 2 H, 4-NH2, D2O exchangeable), 8.20 (s, 1 H, 2-H).
Anal. Calcd. for C11H13FN4O4: C, 46.48; H, 4.61; N, 19.71. Found: C, 46.68;
H, 4.87; N, 19.43.

ANTITUMOR=ANTIVIRAL AGENTS
1995
Compounds 45 and 46 were synthesized by methodology similar to that
described for compound 37.
4-Chloro-7-fluoro-1-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)imidazo[4,5-
c]pyridine(45). Compound 45 was isolated as a white foam (0.77 g, 61%):
1HNMR (CDCl 3) d 4.82 (m, 2 H, 50-H), 4.92 (m, 1 H, 40-H), 5.94 (m, 2 H, 20-
and 30-H), 6.58 (d, 1 H, 10-H, J ¼ 5 Hz), 7.30–8.10 (m, 15 H, ArH), 8.13 (d, 1
H, 7-H, J ¼ 1.5 Hz), 8.27 (s, 1 H, 2-H). Anal. Calcd. for C32H23ClFN3O7: C,
62.39; H, 3.76; N, 6.82. Found: C, 62.12; H, 4.02; N, 6.63.
4,7-Dichloro-1-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)imidazo[4,5-c]pyri
1
dine(46). Compound 46 was isolated as a foam (2.4 g, 47%): HNMR
(CDCl3) d 4.75 (m, 2 H, 50-H), 4.80 (m, 1 H, 40-H), 5.95 (m, 1 H, 30-H), 6.00
(m, 1 H, 20-H), 7.15 (d, 1 H, 10-H, J ¼ 6 Hz), 7.25–8.00 (m, 15 H, ArH), 8.15
(s, 1 H, 6-H), 8.40 (s, 1 H, 2-H). Anal. Calcd. for C32H23Cl2N3O7: C, 60.87;
H, 3.67; N, 6.66. Found: C, 61.10; H, 3.84; N, 6.30.
4-Chloro-7-fluoro-1-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine(47).
To
a suspension of 4-chloro-7-fluoro-1-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)-
imidazo[4,5-c]pyridine (45, 0.73 g, 1.2 mmol) in dry methanol (50 mL) was
added sodium methoxide until pH10 was reached. The reaction mixture was
refluxed for 30 min, cooled, neutralized with glacial acetic acid, and evapo-
rated to dryness. The residue was purified by silica gel column chromato-
graphy (CH2Cl2=EtOH, 10:1, v=v) to give 0.29 g (78%) as a white solid: mp
1
187–189ꢀC; HNMR (DMSO- d6) d 3.58 (m, 1 H, 50-HA), 3.70 (m, 1 H, 50-
HB), 3.99 (m, 1 H, 40-H), 4.13 (m, 1 H, 30-H), 4.36 (m, 1 H, 20-H), 5.16 (t, 1 H,
50-OH, D2O exchangeable), 5.28 (d, 1 H, OH, D2O exchangeable), 5.63 (d, 1
H , OH , DO exchangeable), 6.03 (d, 1 H, 10-H, J ¼ 5.1 Hz), 8.27 (d, 1 H, 6-H,
2
J ¼ 2.1 Hz), 8.88 (s, 1 H, 2-H). Anal. Calcd. for C11H11ClFN3O4: C, 43.50;
H, 3.65; N, 13.84. Found: C, 43.43; H, 3.26; N, 13.81.
4,7-Dichloro-1-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine(48).
Com-
pound 48 was synthesized by a procedure similar to that described for
compound 47 and was isolated as white crystals (0.2 g, 56%): mp 172–174ꢀC;
1HNMR (DMSO- d6) d 3.53 (m, 1 H, 50-HA), 3.65 (m, 1 H, 50-HB), 4.15 (m, 1
0
H , 4-H), 4.28 (m, 1 H, 30-H), 4.45 (m, 1 H, 20-H), 4.94 (t, 1 H, 50-OH, D2O
exchangeable), 5.27 (d, 1 H, OH, D2O exchangeable), 5.43 (d, 1 H, OH, D2O
exchangeable), 6.79 (d, 1 H, 10-H, J ¼ 5.1 Hz), 8.27 (s, 1 H, 6-H), 8.72 (s, 1 H,
2-H). Anal. Calcd. for C11H11Cl2N3O4: C, 41.27; H, 3.46; N, 13.13. Found:
C, 41.00; H, 3.57; N, 12.91.
4-Amino-7-fluoro-1-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine(51).
A
suspension of 4-chloro-7-fluoro-1-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine
(47, 0.51 g, 1.7 mmol) in 30 mL of anhydrous hydrazine was refluxed for

1996
LIU ET AL.
1 h. The reaction mixture was evaporated in vacuo to dryness and the
residue was co-evaporated with ethanol (30 mL) and deoxygenated water
twice (2630 mL). The residue was dissolved in 40 mL of deoxygenated
water containing 3.0 g (wet weight) of Raney Nickel and was refluxed with
stirring under hydrogen (1 atm) for 8 h. The reaction mixture was filtered
through Celite while hot, and the catalyst was washed with hot deox-
ygenated water. The combined filtrate and washings were evaporated in
vacuo to dryness. The residue was purified by silica gel column chroma-
tography (CH2Cl2=EtOH, 6:1, v=v) to give 0.26 g (54%) of product as a
white solid: mp 160–161ꢀC; UV (MeOH) lmax 270 nm (e 7,145), lmin
238 nm; UV (0.01 N HCl) lmax 268 nm (e 8,077), lmin 238 nm; UV (0.01 N
1
NaOH) lmax 268 nm (e 7,445), lmin 238 nm; HNMR (DMSO- d6) d 3.58
(m, 1 H, 50-HA), 3.62 (m, 1 H, 50-HB), 3.94 (m, 1 H, 40-H), 4.10 (m, 1 H, 30-
H), 4.35 (m, 1 H, 20-H), 5.07 (t, 1 H, 50-OH, D2O exchangeable), 5.24 (d, 1
H , OH , DO exchangeable), 5.54 (d, 1 H, OH, D2O exchangeable), 5.91 (d,
2
0
1 H , 1-H, J ¼ 5.1 Hz), 6.22 (br s, 2 H, NH2, D2O exchangeable), 7.67 (d, 1
H, 6-H, J ¼ 2.1 Hz), 8.48 (s, 1 H, 2-H). Anal. Calcd. for C11H13FN4O4: C,
46.48; H, 4.61; N, 19.71. Found: C, 46.52; H, 4.50; N, 19.50.
4-Amino-7-chloro-1-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine
(52). Compound 52 was synthesized by a procedure similar to that descri-
bed for compound 51 and was isolated as a white solid (0.14 g, 49%): mp
169ꢀC (dec); UV (MeOH) lmax 271 nm (e 7,010), lmin 237 nm; UV (0.01 N
HCl) lmax 269 nm (e 7,900), lmin 236 nm; UV (0.01 N NaOH) lmax 269 nm
(e 7,400), lmin 236 nm; 1HNMR (DMSO- d6) d 3.45 (m, 1 H, 50-HA), 3.56 (m,
0
1 H , 5-HB), 4.12 (m, 1 H, 40-H), 4.20 (m, 1 H, 30-H), 4.34 (m, 1 H, 20-H), 4.92
(t, 1 H, 50-OH, D2O exchangeable), 5.27 (d, 1 H, OH, D2O exchangeable),
5.61 (d, 1 H, OH, D2O exchangeable), 6.08 (br s, 2 H, NH2, D2O
exchangeable), 6.41 (d, 1 H, 10-H, J ¼ 4.5 Hz), 7.72 (s, 1 H, 6-H), 8.41 (s, 1 H,
2-H). Anal. Calcd. for C11H13ClN4O4: C, 43.93; H, 4.36; N, 18.63. Found: C,
43.70; H, 4.32; N, 18.51.
Compounds 53–56 were synthesized by methodology similar to that
described for compound 37.
4,6,7-Trifluoro-1-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)imidazo[4,5-c]py
ridine(53). Compound 53 was isolated as a foam (0.76 g, 36%): TLC, Rf
0.47 (CH2Cl2=EtOAc, 30:1, v=v); 1HNMR (CDCl 3) d 4.80–4.90 (m, 3 H, 40-
and 50-H), 5.94 (m, 2 H, 20- and 30-H), 6.55 (d, 1 H, 10-H, J ¼ 5.2 Hz), 7.30–
8.05 (m, 15 H, ArH), 8.25 (s, 1 H, 2-H). Anal. Calcd. for C32H22F3N3O7: C,
62.24; H, 3.59; N, 6.80. Found: C, 62.25; H, 3.49; N, 6.51.
4,6,7-Trifluoro-3-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)imidazo[4,5-c]py
ridine(54). Compound 54 was isolated as a foam (0.53 g, 25%): TLC,
1
Rf 0.55 (CH2Cl2=EtOAc, 30:1, v=v); HNMR (CDCl ) d 4.80–4.92 (m, 3
3

ANTITUMOR=ANTIVIRAL AGENTS
1997
0
H , 4- and 50-H), 5.95 (m, 2 H, 20- and 30-H), 6.53 (d, 1 H, 10-H, J ¼ 5.5 Hz),
7.30–8.20 (m, 15 H, ArH), 8.43 (s, 1 H, 2-H). Anal. Calcd. for
C32H22F3N3O7: C, 62.24; H, 3.59; N, 6.80. Found: C, 62.06; H, 3.31; N, 6.69.
7-Chloro-4,6-difluoro-1-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)imidazo-
[4,5-c]pyridine(55). Compound 55 was isolated as a foam (0.57 g, 34%):
TLC, Rf 0.38 (CH2Cl2=EtOAc, 30:1, v=v); 1HNMR (CDCl 3) d 4.78–4.90 (m,
0
3 H , 4- and 50-H), 5.97 (m, 2 H, 20- and 30-H), 6.50 (d, 1 H, 10-H, J ¼ 5.1 Hz),
7.30–8.12 (m, 15 H, ArH), 8.35 (s, 1 H, 2-H). Anal. Calcd. for
C32H22ClF2N3O7: C, 60.62; H, 3.50; N, 6.63. Found: C, 60.46; H, 3.40; N,
6.49.
7-Chloro-4,6-difluoro-3-(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)imidazo-
[4,5-c]pyridine(56). Compound 56 was isolated as a foam (0.50 g, 26%):
TLC, Rf 0.47 (CH2Cl2=EtOAc, 30:1, v=v); 1HNMR (CDCl 3) d 4.77–4.85 (m,
0
3 H , 4- and 50-H), 5.92 (m, 2 H, 20- and 30-H), 6.50 (d, 1 H, 10-H, J ¼ 5.2 Hz),
7.25–8.15 (m, 15 H, ArH), 8.40 (s, 1 H, 2-H). Anal. Calcd. for
C32H22ClF2N3O7: C, 60.62; H, 3.50; N, 6.63. Found: C, 60.87; H, 3.39;
N, 6.52.
Compounds 57–60 were synthesized by methodology similar to that
described for compound 38.
4-Amino-6,7-difluoro-1-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine(57).
Compound 57 was isolated as a white solid (0.17 g, 77%): mp 163–165ꢀC; UV
(MeOH) lmax 274 nm (e 13,510), lmin 232 nm; UV (0.01 N HCl) lmax 274 nm
(e 12,256), lmin 232 nm; UV (0.01 N NaOH) lmax 274 nm (e 11,421), lmin
1
232 nm; HNMR (DMSO- d6) d 3.65 (m, 1 H, 50-HA), 3.67 (m, 1 H, 50-HB),
3.93 (m, 1 H, 40-H), 4.02 (m, 1 H, 30-H), 4.32 (m, 1 H, 20-H), 5.07 (t, 1 H, 50-
OH, D2O exchangeable), 5.22 (d, 1 H, OH, D2O exchangeable), 5.54 (d, 1 H,
OH, D2O exchangeable), 5.87 (d, 1 H, 10-H, J ¼ 5.6 Hz), 6.65 (br s, 2 H, NH2,
D2O exchangeable), 8.43 (s, 1 H, 2-H). Anal. Calcd. for C11H12F2N4O4: C,
43.71; H, 4.00; N, 18.54. Found: C, 43.92; H, 3.91; N, 18.59.
4-Amino-6,7-difluoro-3-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine(58).
Compound 58 was isolated as a white solid (0.14 g, 88%): mp 155–157ꢀC;
UV (MeOH) lmax 292 nm (e 5,742), lmin 264 nm; UV (0.01 N HCl) lmax
292 nm (e 6,045), lmin 262 nm; UV (0.01 N NaOH) lmax 292 nm (e 5,440),
1
l
min 262 nm; HNMR (DMSO- d6) d 3.65 (m, 1 H, 50-HA), 3.68 (m, 1 H, 50-
HB), 4.01 (m, 1 H, 40-H), 4.11 (m, 1 H, 30-H), 4.22 (m, 1 H, 20-H), 5.13 (t, 1 H,
50-OH, D2O exchangeable), 5.20 (d, 1 H, OH, D2O exchangeable), 5.30 (d, 1
H , OH , DO exchangeable), 5.90 (d, 1 H, 10-H, J ¼ 6.6 Hz), 6.34 (br s, 2 H,
2
NH2, D2O exchangeable), 8.54 (s, 1 H, 2-H). Anal. Calcd. for
C11H12F2N4O4: C, 43.71; H, 4.00; N, 18.54. Found: C, 43.90; H, 4.02; N,
18.16.

1998
LIU ET AL.
4-Amino-7-chloro-6-fluoro-1-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine(59).
Compound 59 was isolated as a white solid (0.10 g, 85%): mp 175–177ꢀC; UV
(MeOH) lmax 274 nm (e 14,503), lmin 234 nm; UV (0.01 N H Cl)lmax 274 nm
(e 12,997), lmin 236 nm; UV (0.01 N NaOH) lmax 274 nm (e 15,367), lmin
1
235 nm; HNMR (DMSO- d6) d 3.52 (m, 1 H, 50-HA), 3.62 (m, 1 H, 50-HB),
3.95 (m, 1 H, 40-H), 4.10 (m, 1 H, 30-H), 4.37 (m, 1 H, 20-H), 5.12 (t, 1 H, 50-OH,
D2O exchangeable), 5.22 (d, 1 H, OH, D2O exchangeable), 5.58 (d, 1 H, OH,
D2O exchangeable), 6.34 (d, 1 H, 10-H, J ¼ 4.5 H z), 6.94 (br s, 2 H , NH, D2O
2
exchangeable), 8.51 (s, 1 H, 2-H). Anal. Calcd. for C11H12ClFN4O4: C, 41.45;
H, 3.80; N, 17.58. Found: C, 41.17; H, 4.00; N, 17.35.
4-Amino-7-chloro-6-fluoro-3-(b-D-ribofuranosyl)imidazo[4,5-c]pyridine(60).
Compound 60 was isolated as a white solid (0.13 g, 53%): mp 166–168ꢀC; UV
(MeOH) lmax 292 nm (e 8,631), lmin 268 nm; UV (0.01 N HCl) lmax 292 nm (e
8,465), lmin 266 nm; UV (0.01 N NaOH) lmax 292 nm (e 7,967), lmin 268 nm;
1HNMR (DMSO- d6) d 3.55 (m, 1 H, 50-HA), 3.65 (m, 1 H, 50-HB), 3.98 (m, 1
0
H , 4-H), 4.11 (m, 1 H, 30-H), 4.20 (m, 1 H, 20-H), 5.25 (t, 1 H, 50-OH, D2O
exchangeable), 5.35 (d, 1 H, OH, D2O exchangeable), 5.65 (d, 1 H, OH, D2O
exchangeable), 5.87 (d, 1 H, 10-H, J¼ 6.6 H z), 6.63 (br s, 2 H , NH, D2O
2
exchangeable), 8.55 (s, 1 H, 2-H). Anal. Calcd. for C11H12ClFN4O4: C, 41.45;
H, 3.80; N, 17.58. Found: C, 41.31; H, 4.10; N, 17.27.
6-Amino-7-chloro-1,5-dihydro-1-b-D-ribofuranosylimidazo[4,5-c]pyridin-
4-one (3-chloro-3-deazaguanosine, 61). To a stirred suspension of 3-deaza-
guanosine8,24 (0.25 g, 0.9 mmol) in 7 mL of water was added N-chlor-
osuccimide (0.14 g, 1.0 mmol) at 0–5ꢀC in an ice-water bath. The reaction
mixture was stirred at 0–5ꢀC for 1 h. The solid was collected, washed with
cold water and then cold acetone. Crystallization from water provided 0.12 g
(42%) of product: mp 195–196ꢀC (dec.); UV (MeOH) lmax 273 nm (e 11,000),
lmin 238 nm; UV (0.01 N HCl) lmax 285 nm (e 13,200), lmin 242 nm; UV
(0.01 N NaOH) lmax 274 nm (e 11,200), lmin 240 nm; 1HNMR (DMSO- d6)
d 3.52 (m, 2 H, 50-H), 3.90 (m, 1 H, 40-H), 4.10 (m, 1 H, 30-H), 4.25 (m, 1 H,
20-H), 5.02 (d, 1 H, OH, D2O exchangeable), 5.10 (t, 1 H, OH, D2O
exchangeable), 5.40 (d, 1 H, OH, D2O exchangeable), 5.70 (br s, 2 H, NH2,
D2O exchangeable), 6.25 (d, 1 H, 10-H, J ¼ 7.0 Hz), 8.10 (s, 1 H, 2-H), 10.70
(br s, 1 H, NH, D2O exchangeable). Anal. Calcd. for C11H13ClN4O5: C,
41.71; H, 4.14; N, 17.69. Found: C, 41.80; H, 4.00; N, 17.38.
6-Amino-7-bromo-1,5-dihydro-1-b-D-ribofuranosylimidazo[4,5-c]pyridin-
4-one (3-bromo-3-deazaguanosine, 62). To a stirred suspension of 3-deaza-
guanosine8,24 (0.5 g, 1.8 mmol) in 6 mL of water was added gradually 12 mL
of saturated bromine-water at such a rate that the yellow color of the reaction
mixture disappeared between each addition (ꢁ 5 min). The reaction mixture
was stirred for another 5 min and the solid was collected by filtration, and

ANTITUMOR=ANTIVIRAL AGENTS
1999
washed with cold water and cold acetone. The solid was crystallized from
water to give 0.45 g (70%) of product: mp 174ꢀC (dec.); UV (MeOH) lmax
274 nm (e 11,200), lmin 240 nm; UV (0.01 N HCl) lmax 284 nm (e 13,200),
1
lmin 238 nm; UV (0.01 N NaOH) lmax 274 nm (e 11,600), lmin 240 nm; H
NMR (DMSO-d6) d 3.50 (m, 2 H, 50-H), 3.80 (m, 1 H, 40-H), 4.05 (m, 1 H, 30-
H), 4.28 (m, 1 H, 20-H), 5.20-5.40 (br s, 2 H, OH, D2O exchangeable), 5.40
(t, 1 H, OH, D2O exchangeable), 5.62 (br s, 2 H, NH2, D2O exchangeable),
6.38 (d, 1 H, 10-H, J ¼ 6.8 Hz), 8.12 (s, 1 H, 2-H), 10.62 (br s, 1 H, NH, D2O
exchangeable). Anal. Calcd. for C11H13BrN4O5: C, 36.58; H, 3.62; N, 15.51.
Found: C, 36.41; H, 3.43; N, 15.23.
ACKNOWLEDGMENT
This research was supported in part by Connecticut Innovations, Inc.
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Received June 28, 2001
Accepted September 26, 2001