Synthesis of deuterium-labelled 6-[5-(4-amidinophenyl)furan-2-yl]nicotinamidine and N-alkoxy-6-{5-[4-(N-alkoxyamidino)phenyl]-furan-2-yl}-nicotinamidines

Article abstract of DOI:10.1002/jlcr.817

6-[5-(4-Amidinophenyl)furan-2-yl]nicotinamidine-d₄ (5) was synthesized from 6-[5-(4-cyanophenyl)furan-2-yl]nicotinonitrile-d₄ (3), through the bis-O-acetoxy-amidoxime followed by hydrogenation. Compound 3 was prepared from 6-(furan-2

Full text of DOI:10.1002/jlcr.817

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS
J Label Compd Radiopharm 2004; 47: 233–242.
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jlcr.817
Research Article
Synthesis of deuterium-labelled 6-[5-(4-
amidinophenyl)furan-2-yl]nicotinamidine and
N-alkoxy-6-{5-[4-(N-alkoxyamidino)phenyl]-
furan-2-yl}-nicotinamidines
Mohamed A. Ismail and David W. Boykin*
Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
Summary
6-[5-(4-Amidinophenyl)furan-2-yl]nicotinamidine-d4 (5) was synthesized from 6-[5-
(4-cyanophenyl)furan-2-yl]nicotinonitrile-d4 (3), through the bis-O-acetoxy-amidox-
ime followed by hydrogenation. Compound 3 was prepared from 6-(furan-2-yl)-
nicotinonitrile by a Heck coupling reaction with 4-bromobenzonitrile-d4, a product of
selective cyanation reaction of 1,4-dibromobenzene-d4 with Cu(1)CN. Deuterium-
labelled N-methoxy-6-{5-[4-(N-methoxy-amidinophenyl]-furan-2-yl}-nicotinamidines
were prepared via methylation of their respective amidoximes with dimethyl
sulfate-d6 in aqueous sodium hydroxide in good yields. Copyright # 2004 John
Wiley & Sons, Ltd.
Key Words: deuterium-labelled; prodrug; cyanation; Heck reaction; Suzuki coupling
Introduction
2,5-Bis[4-methoxy-amidinophenyl]furan (I), a prodrug, is an orally effective
antitrypanosomal compound which is currently entered into Phase II clinical
trials.1,2 The prodrug undergoes a multistep bioconversion in vivo to yield the
active drug furamidine (II).3–6 The establishment of the bioconversion
pathway of I into II was significantly aided by the synthesis of deuterium
labelled I and II (Figure 1).7
As part of an effort to develop antitrypanosomal compounds that are more
effective than I/II we have found that aza-analogs of these compounds show
excellent activity against Trypanosoma brucei rhodesiense (T. b. r.) both in vitro
and in vivo in a mouse model.8 Specifically, III which is a prodrug of IV, has
*Correspondence to. D. W. Boykin, Department of Chemistry, Georgia State University, Atlanta, GA
30303, USA. E-mail: dboykin@gsu.edu
Contract/grant sponser: Bill and Melinda Gates Foundation
Copyright # 2004 John Wiley & Sons, Ltd.
Received 11 September 2003
Revised 10 November 2003
Accepted 21 January 2004

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M. A. ISMAIL AND D. W. BOYKIN
shown very promising oral activity giving cures in the virulent STIB900 mouse
model T. b. r. at the low dosage of 5 mg/kg which is superior to the activity of I
in the same model. In view of the efficacy of III against T. b. r., preclinical
toxicity and metabolism studies have been initiated in anticipation of clinical
trials. It is expected that labelling of the phenyl group of III and IV with
deuterium (d4-analog) will serve as reasonable mass spectroscopy internal
standards for metabolism studies. For comparative metabolism studies, we
also require the d-4 substituted O-ethyl analog of III. It is hypothesized that
metabolism of III will likely be similar to that of I. However, because III is a
disymmetric molecule it will be necessary to determine if one of the two
different methoximes is preferentially metabolized. Studies focusing on the
in vivo fate of the two different methoxime methyl groups should be greatly
aided by having samples of the di-O-methyl-d3 analog and the two isomeric
mono-O-methyl-d3 analogs of III. Consequently, in this report we describe the
syntheses of the novel isotopically labelled compounds 5-d4, 6a-d4, 6b-d4, 11,
12, 16-d3 and 18-d6 for use in preclinical studies.
Figure 1.
Results and discussion
As outlined in Scheme 1, 6-[5-(4-amidinophenyl)furan-2-yl]nicotinamidine-d4
(5) was synthesized from 6-[5-(4-cyanophenyl)furan-2-yl]nicotinonitrile-d4 (3),
through the bis-O-acetoxyamidoxime followed by hydrogenation. Compound
3 was obtained from 6-(furan-2-yl)nicotinonitrile (1) via Heck reaction with 4-
bromobenzonitrile-d4, a product of selective temperature-dependent cyanation
of the commercially available 1,4-dibromobenzene-d4 with an equimolar
amount of Cu(1)CN at 110–1208C. The prodrugs, N-methoxy- and N-ethoxy-
6-{5-[4-(N-alkoxyamidino)phenyl]-furan-2-yl}-nicotinamidine-d4 (6a, 6b) were
prepared via alkylation of the di-amidoxime 4 with the appropriate dialkyl
sulfate in aqueous sodium hydroxide solution at 08C in good yields.
As shown in Scheme 2, N-methoxy-6-{5-[4-(N-methoxyamidino-phenyl]-
furan-2-yl}-nicotinamidine-d3 (12) bearing a deuterium-labelled methoxy
group on the pyridine sector was obtained in five steps starting with
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235
Scheme 1. Reagents and conditions: (i) Cu(1)CN, DMF, 110-1208C; (ii)
Pd(PPh3)4, DMF; (iii) NH2 OH.HCl/KO-t-Bu, DMSO’ (iv) AcOH/Ac2O; (v)
H2/Pd-C, AcOH. (vi) (R)2 SO4/NaOH, dioxane, 08C
amidoxime formation from readily available 6-(5-bromo-furan-2-yl)-nicotino-
nitrile (7).8 Methylation of the amidoxime 8 with dimethyl sulfate-d6 furnished
6-(5-bromo-furan-2-yl)-N-methoxy-nicotinamidine-d3 (9). Suzuki coupling of
9 with 4-cyanophenyl boronic acid gave 10 in good yield. Again, treatment of
10 with hydroxylamine hydrochloride and potassium tert-butoxide in DMSO
at ambient temperature gave 6-{5-[4-(N-hydroxy-amidinophenyl]-furan-2-yl}-
N-methoxy-nicotinamidine-d3 (11) in 92% yield. Subsequent methylation of 11
with dimethyl sulfate afforded 12.
A multi-step synthesis similar to that described for 12, outlined in Scheme 3,
shows the preparation of N-methoxy-6-{5-[4-(N-methoxyamidino-phenyl]-
furan-2-yl}-nicotinamidine-d3 (16), which bears a deuterium-labelled methoxy
group on the phenyl sector. The only difference was that methylation with
(i)
D3CON
H2N
NOCD3
NH2
HON
H2N
NOH
NH2
O
O
N
N
18
17
Reagents and conditions: (i) (CD3)2SO4/NaOH, dioxane, 0 o
C
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M. A. ISMAIL AND D. W. BOYKIN
Scheme 2. Reagents and conditions: (i) NH2OH.HCl/KO-t-Bu, DMSO; (ii)
(CD3)2SO4/NaOH, dioxane, 08C (iii) Pd(PPh3)4, 4-cyanophenylboronic acid
(iv) (CH3)2SO4/NaOH, dioxane, 08C
Scheme 3. Reagents and conditions: (i) (CH3)2SO4/NaOH, dioxane, 08C, (ii)
Pd(PPh3)4, 4-cyanophenylboronic acid; (iii) NH2OH.HCl/KO-t-Bu, DMSO;
(iv) (CD3)2SO4/NaOH, dioxane, 08C
dimethyl sulfate-d6 was conducted in the last step. N-Methoxy-6-{5-[4-(N-
methoxyamidino-phenyl]-furan-2-yl}-nicotinamidine-d6 (18) was prepared by
direct methylation of the N-hydroxy-6-{5-[4-(N-hydroxyamidino-phenyl]-
furan-2-yl}-nicotinamidine (17)8 with dimethyl sulfate-d6 (Equation (1)). The
hydrochloride salts of all the oximes, 4-d4, 6a-d4, 6b-d4, 11, 12, 16-d3 and 18-d6
were made by passing hydrogen chloride gas into an ethanolic solution of their
free bases.
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DEUTERIUM-LABELLED AZA-FURAMIDINE ANALOGS
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Conclusion
An efficient five-step synthesis of 5 and four-step syntheses of 6a and 6b
starting from 1,4-dibromobenzene-d4 have been developed. Selective labelling
of the two different methoxyamidine groups of IV has been achieved using
dimethyl sulfate-d6 as the source of deuterium. A five-step approach for the
synthesis of 12 starting from 7 has been described. Similarly a five-step process
also starting from 7 yields the other isomeric O-methyl-d3 compound 16.
Direct methylation of 17 with dimethyl sulfate-d6 provided 18-d6. No
detectable loss of deuterium was observed during the synthesis of any of the
target compounds. The use of these deuterium labelled compounds in
metabolism and pharmacokinetic studies will be described in due course.
Experimental section
Melting points were recorded using a Mel-Temp 3.0 capillary melting point
apparatus and are uncorrected. TLC analysis was carried out on silica gel 60
1
F254 precoated aluminum sheets and detected under UV light. H and 13C
NMR spectra were recorded employing a Varian GX400 or Varian Unity Plus
300 spectrometer, and chemical shifts (d) are in ppm relative to TMS as
internal standard. Mass spectra were obtained from the Georgia Institute of
Technology, Atlanta, GA. Elemental analyses were obtained from Atlantic
Microlab Inc. (Norcross, GA) and are within Æ 0.31 of the theoretical values.
The compounds reported as salts frequently analyzed correctly for fractional
moles of waters of hydration. All chemicals and solvents were purchased from
Aldrich Chemical Co., Fisher Scientific or Icons isotopes. 1,4-Dibromoben-
zene-d4 (98 atom% D) and dimethyl sulfate-d6 (99 atom% D) were obtained
from Aldrich. All solvents were reagent grade.
4-Bromobenzonitrile-d4 (2): A mixture of 1,4-dibromobenzene-d4 (8.4 g,
35 mmol) and Cu(1)CN (3.14 g, 35 mmol) in DMF (150 ml) was heated at 110–
1208C for 24 h. The reaction mixture was poured onto water and the solid
which formed was extracted by using ethylacetate (300 ml, 3 times) from aq.
NH4OH. The solvent was evaporated and the precipitate purified by
chromatography (SiO2, hexanes/ether 90:10). Yield 54%, mp 110–1118C. IR
(cmÀ1); 2224, 1560, 1550, 1375, 1309, 1141, 1021, 703. EIMS (m/z, rel.int.):
185 (M+, 100), 132 (10), 106 (80), 92 (5), 78 (25). High resolution EIMS calcd.
for C7D4NBr: 184.9778. Observed 184.97978.
6-[5-(4-Cyano-phenyl)-furan-2-yl]-nicotinonitrile-d4 (3): A mixture of 6-
(furan-2-yl)nicotinonitrile (1) (3.4 g, 20 mmol), 4-bromobenzonitrile-d4 (2)
(3.7 g, 20 mmol), tetrakis(triphenylphosphine)-palladium(0) (600 mg) and
potassium acetate (5 g, 50 mmol) in dry DMF (60 ml) was heated under
nitrogen at 1208C for overnight. The reaction mixture was then poured onto
cold water. The precipitate which formed was collected, dissolved in methylene
chloride, and the solution was passed through celite to remove Pd. The
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solution was evaporated, the solid was filtered and purified to afford 3 (SiO2,
1
hexanes/EtOAc, 30:70), in 61% yield; mp 297–2998C. H NMR (DMSO-d6);
d 7.41 (d, J=3.6 Hz, 1 H), 7.47 (d, J=3.6 Hz, 1 H), 8.09 (d, J=8.1 Hz 1 H),
8.34 (d, J=8.1 Hz, 1 H), 8.99 (s, 1 H). EIMS (m/z, rel.int.): 275 (M+, 100), 247
(5), 144 (20), 103 (20). High resolution EIMS calcd. for C17H5D4N3O:
275.09967. Observed 275.09948. Anal. Calcd. for C17H5D4N3O: C, 74.16; H +
D as H, 3.27. Found: C, 73.88; H + D as H, 3.33.
N-Hydroxy-6-{5-[4-N-hydroxyamidino-phenyl]-furan-2-yl}-nicotinamidine-
d4 (4): A mixture of hydroxylamine hydrochloride (10.4 g, 150 mmol, 10 eq.)
in anhydrous DMSO (80 ml) was cooled to 58C under nitrogen and potassium
t-butoxide (16.8 g, 150 mmol, 10 eq.) was added in portions. The mixture was
stirred for 30 min. To this mixture was added the bis-cyano derivative 3 (4.12
g; 15 mmol, 1 eq.). The reaction mixture was stirred for 24 h at room
temperature. The reaction mixture was then poured slowly onto ice-water
(200 ml water and 200 ml ice). The precipitate was filtered and washed with
water and then ethanol to afford 4 (as free base) in 94% yield; mp 245–2478C.
1H NMR (DMSO-d6); d 5.79 (s, 2 H), 5.93 (s, 2 H), 7.18 (d, J=3.6 Hz, 1 H),
7.26 (d, J=3.6 Hz, 1 H), 7.91 (d, J=8.1 Hz, 1 H), 8.11 (d, J=8.1 Hz, 1 H). 8.89
(s, 1 H), 9.64 (s, 1 H), 9.81 (s, 1 H). 13C NMR; d 153.6, 152.5, 150.3, 148.7,
148.2, 146.7, 133.6, 132.4, 129.8, 127.2, 117.7, 111.7, 109. (4 hydrochloride salt);
mp 281–2838C dec. MS (m/z, rel.int, Fab., thioglycerol); 342 (M++1, 100),
326 (40), 293 (5), 267 (5). High resolution mass calcd. for C17H12D4N5O3:
342.15042. Observed 342.14950. Anal. Calcd. for C17H11D4N5O3-3.0HCl-
1.0H2O: C, 43.55; H + D as H, 4.27; N, 14.94. Found: C, 43.46; H + D as H,
4.28; N, 14.70.
6-[5-(4-Amidino-phenyl)-furan-2-yl]-nicotinamidine-d4 acetate salt (5): To a
solution of 4 (0.341 g, 1 mmol) in glacial acetic acid (10 ml) was slowly added
acetic anhydride (0.35 ml). After stirring overnight, TLC indicated complete
acylation of the starting material. The reaction mixture was poured onto ice-
water, the precipitate was filtered, washed with water and dried. To the
precipitate in glacial acetic acid (13 ml), and ethanol (20 ml) was added 10%
palladium on carbon (80 mg). The mixture was placed on a Parr hydrogena-
tion apparatus at 50 psi for 4 h at room temperature. The mixture was filtered
through hyflo and the filter pad washed with water. The filtrate was
evaporated under reduced pressure and the precipitate was collected and
washed with ether to give 5 in 79% yield, mp 263–2658C dec. 1H NMR (D2O/
DMSO-d6); d 1.89 (s, 2xCH3), 7.28 (s, 1H), 7.33 (s, 1H), 7.98 (s, 1H), 8.24 (s,
1H), 8.99 (s, 1H). MS (m/z, rel.int, Fab., thioglycerol); 310 (M++1, 100), 273
(20), 237 (40). High resolution mass calcd. for C17H12D4N5O: 310.16059.
Observed 310.16000. Anal. Calcd. for C17H11D4N5O-2.0AcOH-2.0H2O: C,
54.18; H + D as H, 5.80; N, 15.04. Found: C, 54.31; H + D as H, 5.77; N,
14.82.
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N-Methoxy-6-{5-[4-(N-methoxyamidino-phenyl]-furan-2-yl}-nicotinamidine-
d4 (6a): To a solution of 4 (0.511 g, 1.5 mmol) in dioxane (6 ml) and 2 N
NaOH (12 ml) at 0–58C, was slowly added dimethyl sulfate (0.568 g, 4.5 mmol)
in dioxane (5 ml). The reaction mixture was further stirred for 2 h at room
temperature and then extracted with ethylacetate (150 ml, 3 times). The solvent
was evaporated and the residue was purified by chromatography (SiO2,
hexanes/EtOAc, 40:60) to give 6a (free base) in 58% yield; mp 162–1638C. 1H
NMR (DMSO-d6); d 3.77 (s, 3H), 3.79 (s, 3H), 6.14 (s, 2H), 6.30 (s, 2H), 7.24
(d, J=3.6 Hz, 1H), 7.30 (d, J=3.6 Hz, 1H), 7.94 (d, J=8.4 Hz, 1H), 8.11 (dd,
J=8.4, 2.4 Hz, 1H), 8.87 (d, J=2.4 Hz, 1H). 13C NMR; d 153.6, 152.5, 150.5,
149.0, 148.5, 146.9, 134.1, 131.6, 130.2, 126.5, 117.7, 112.0, 109.2, 60.7, 60.6.
EIMS (m/z, rel.int.); 369 (M+, 65), 322 (30), 275 (100), 247 (5). High
resolution EIMS calcd. for C19H15D4N5O3: 369.17390. Observed 369.17379.
(6a hydrochloride salt); mp 206–2088C dec. Anal. Calcd. for C19H15D4N5O3-
3.0HCl-0.75H2O: C, 46.35; H + D as H, 4.78; N, 14.22. Found: C, 46.57; H +
D as H, 4.93; N, 14.01.
N-Ethoxy-6-{5-[4-(N-ethoxyamidino-phenyl]-furan-2-yl}-nicotinamidine-d4
(6b): The same procedure described for 6a was used by employing diethyl
sulfate instead of dimethyl sulfate. Free base of 6b, yield 75%; mp 175–
176.58C. 1H NMR (DMSO-d6); d 1.25 (m, 6H), 4.03 (m, 4H), 6.07 (s, 2H), 6.22
(s, 2H), 7.23 (d, J=3.6 Hz, 1H), 7.30 (d, J=3.6 Hz, 1H), 7.93 (d, J=8.7 Hz,
1H), 8.11 (dd, J=8.7, 2.4 Hz, 1H), 8.86 (d, J=2.4 Hz, 1H). 13C NMR; d 153.6,
152.5, 150.4, 148.8, 148.5, 146.9, 134.0, 131.8, 130.1, 126.7, 117.7, 111.9, 109.2,
68.0, 67.8, 14.8. EIMS (m/z, rel.int.); 397 (M+, 40), 336 (15), 275 (100), 247
(5), 144 (10). High resolution EIMS calcd. for C21H19D4N5O3: 397.20520.
Observed 397.20470. (6b hydrochloride salt); mp 200–201.58C dec. Anal. Calcd.
for C21H19D4N5O3-3.0HCl-1.2H2O: C, 47.73; H + D as H, 5.38; N, 13.25.
Found: C, 47.91; H+D as H, 5.45; N, 12.94.
6-(5-Bromo-furan-2-yl)-N-hydroxy-nicotinamidine (8): The same procedure
described for 4 was used, starting with 6-(5-bromo-furan-2-yl)-nicotinonitrile
(7).8 Yield 97%; mp 217–2188C. 1H NMR (DMSO-d6); d 6.02 (s, 2H), 6.80 (d,
J=3.6 Hz, 1H), 7.20 (d, J=3.6 Hz, 1H), 7.73 (d, J=8.4 Hz 1H), 8.09 (dd,
J=8.4, 2.1 Hz, 1H), 8.86 (d, J=2.1 Hz, 1H), 9.92 (s, 1H). EIMS (m/z, rel.int.);
281 (M+, 100), 265 (70), 250 (50), 186 (50), 169 (30). High resolution EIMS
calcd. for C10H8BrN3O2: 280.97999. Observed 280.98038.
6-(5-Bromo-furan-2-yl)-N-methoxy-nicotinamidine-d3 (9): The same proce-
dure described for 6a was used, starting with 8 and employing dimethyl
sulfate-d6 instead of dimethyl sulfate. Yield 86%; mp 171.5–172oC (analyti-
1
cally pure from the reaction mixture). H NMR (DMSO-d6); d 6.26 (s, 2H),
6.78 (d, J=3.6 Hz, 1H), 7.19 (d, J=3.6 Hz, 1H), 7.71 (d, J=8.4 Hz 1H), 8.07
(dd, J=8.4, 2.4 Hz, 1H), 8.82 (d, J=2.4 Hz, 1H). 13C NMR; d 154.6, 148.8,
147.7, 146.8, 134.2, 126.9, 123.3, 117.6, 114.5, 112.0. Anal. Calcd. for
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C11H7D3BrN3O2: C, 44.16; H + D as H, 3.34; N, 14.04. Found: C, 44.09; H
+ D as H, 3.33; N, 13.89.
6-[5-(4-Cyano-phenyl)-furan-2-yl]-N-methoxy-nicotinamidine-d3 (10): To a
stirred solution of 9 (2.99 g, 10 mmol), and tetrakis(triphenylphosphine)
palladium (300 mg) in toluene (20 ml) under a nitrogen atmosphere was added
10 ml of a 2 M aqueous solution of Na2CO3 followed by 4-cyanophenyl
boronic acid (2.14 g, 12 mmol) in 8 ml of methanol. The vigorously stirred
mixture was warmed to 808C for 24 h, then concentrated, and partitioned
between ethylacetate (300 ml) and 2 M aqueous Na2CO3 (50 ml) containing
5 ml of concentrated ammonia. The organic layer was dried (Na2SO4), and
then concentrated to dryness under reduced pressure to afford 10 in 71% yield
1
after chromatography (SiO2, hexanes/EtOAc, 30:70); mp 196–196.58C. H
NMR (DMSO-d6); d 6.29 (s, 2H), 7.31 (d, J=3.6 Hz, 1H), 7.42 (d, J=3.6 Hz,
1H), 7.92 (d, J=8.4 Hz, 2H), 7.96 (d, J=8.4 Hz, 1H). 8.04 (d, J=8.4 Hz, 2H),
8.12 (dd, J=8.4, 1.5 Hz, 1H), 8.86 (d, J=1.5 Hz, 1H). 13C NMR; d 153.6,
152.2, 148.9, 148.2, 147.0, 134.1, 133.6, 132.9, 126.9, 124.2, 118.8, 118.1, 112.1,
111.8, 109.8. EIMS (m/z, rel.int.); 321 (M+, 100), 287 (30), 271 (30), 245 (5),
218 (15). High resolution EIMS calcd. for C18H11D3N4O2: 321.13051.
Observed 321.13106. Anal. Calcd. for C18H11D3N4O2: C, 67.28; H + D as
H, 4.36. Found: C, 67.37; H + D as H, 4.50.
6-{5-[4-(N-Hydroxyamidino-phenyl]-furan-2-yl}-N-methoxy-nicotinamidine-
d3 (11): The same procedure described for 4 was used, starting with 10. Free
1
base of 11, yield 92%, mp 201–2038C. H NMR (DMSO-d6); d 5.90 (s, 2H),
6.28 (s, 2H), 7.21 (d, J=3.6 Hz, 1H), 7.28 (d, J=3.6 Hz, 1H), 7.78 (d,
J=8.4 Hz, 2H), 7.87 (d, J=8.4 Hz, 2H), 7.93 (d, J=8.4 Hz, 1H), 8.10 (dd,
J=8.4, 1.5 Hz, 1H), 8.85 (d, J=1.5 Hz, 1H), 9.74 (s, 1H). 13C NMR; d 153.7,
152.4, 150.4, 149.0, 148.5, 146.9, 134.1, 132.6, 130.0, 126.5, 125.8, 123.5, 117.7,
111.9, 109.0. EIMS (m/z, rel.int.); 354 (M+, 40), 338 (80), 321 (1 0 0), 304 (10),
272 (35). High resolution EIMS calcd. for C18H14D3N5O3: 354.15197.
Observed 354.15339. (11 hydrochloride salt); mp 233–2358C. Anal. Calcd. for
C18H14D3N5O3-3.0HCl-0.5H2O: C, 45.72; H + D as H, 4.44; N, 14.81.
Found: C, 45.69; H + D as H, 4.42; N, 14.78.
N-Methoxy-6-{5-[4-(N-methoxyamidino-phenyl]-furan-2-yl}-nicotinamidine-
d3 (12): The same procedure described for 6a was used, starting with 11. Free
base of 12, yield 65%, mp 169–169.5oC. 1H NMR (DMSO-d6); d 3.76 (s, 3H),
6.13 (s, 2H), 6.28 (s, 2H), 7.21 (d, J=3.6 Hz, 1H), 7.28 (d, J=3.6 Hz, 1H), 7.76
(d, J=8.4 Hz, 2H), 7.86 (d, J=8.4 Hz, 2H), 7.93 (d, J=8.4 Hz, 1H), 8.09 (dd,
J=8.4, 2.1 Hz, 1H), 8.85 (d, J=2.1 Hz, 1H). 13C NMR; d 153.6, 152.5, 150.5,
148.9, 148.5, 146.9, 134.0, 131.8, 130.3, 126.4, 126.1, 123.4, 117.7, 111.9, 109.1,
60.5. EIMS (m/z, rel.int.); 368 (M+, 100), 338 (10), 321 (15), 287 (40), 245 (10).
High resolution EIMS calcd. for C19H16D3N5O3: 368.16762. Observed
368.16896. (12 hydrochloride salt); mp 224–2268C. Anal. Calcd. for
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C19H16D3N5O3-3.0HCl-1.3H2O: C, 45.53; H + D as H, 4.91; N, 13.97.
Found: C, 45.53; H + D as H, 4.98; N, 13.83.
6-(5-Bromo-furan-2-yl)-N-methoxy-nicotinamidine (13): The same proce-
dure described for 6a was used, starting with 8. Yield 90%; mp 170.5–1718C
(analytically pure from the reaction mixture). 1H NMR (DMSO-d6); d 3.78 (s,
3H), 6.29 (s, 2H), 6.80 (d, J=3.6 Hz, 1H), 7.21 (d, J=3.6 Hz, 1H), 7.73 (d,
J=8.4 Hz, 1H), 8.08 (dd, J=8.4, 2.1 Hz, 1H), 8.83 (d, J=2.1 Hz, 1H). 13C
NMR; d 154.6, 148.8, 147.6, 146.8, 134.2, 126.8, 123.2, 117.5, 114.4, 111.9,
60.7. Anal. Calcd. for C11H10BrN3O2: C, 44.62; H, 3.40. Found: C, 44.70; H,
3.34.
6-[5-(4-Cyano-phenyl)-furan-2-yl]-N-methoxy-nicotinamidine (14): The same
procedure described for 10 was used, starting with 13. Yield 68%; mp
1
196–1978C after chromatography (SiO2, hexanes/EtOAc, 30:70). H NMR
(DMSO-d6); d 3.79 (s, 3H), 6.31 (s, 2H), 7.35 (d, J=3.6 Hz, 1H), 7.45 (d,
J=3.6 Hz, 1H), 7.94 (d, J=8.4 Hz, 2H), 7.98 (d, J=8.4 Hz, 1H). 8.07 (d,
J=8.4 Hz, 2H), 8.13 (dd, J=8.4, 2.1 Hz, 1H), 8.88 (d, J=2.1 Hz, 1H). 13C
NMR; d 153.6, 152.2, 148.9, 148.2, 147.0, 134.1, 133.6, 132.9, 126.9, 124.2,
118.8, 118.1, 112.1, 111.8, 109.8, 60.8. Anal. Calcd. for C18H14N4O2: C, 67.91;
H, 4.43. Found: C, 67.84; H, 4.47.
6-{5-[4-(N-Hydroxyamidino-phenyl]-furan-2-yl}-N-methoxy-nicotinamidine
(15): The same procedure described for 4 was used, starting with 14. Free base
of 15, yield 92%, mp 212–213.5oC. 1H NMR (DMSO-d6); d 3.79 (s, 3H), 5.90
(s, 2H), 6.30 (s, 2H), 7.22 (d, J=3.6 Hz, 1H), 7.30 (d, J=3.6 Hz, 1H), 7.79 (d,
J=8.4 Hz, 2H), 7.89 (d, J=8.4 Hz, 2H), 7.94 (d, J=8.1 Hz, 1H), 8.10 (dd,
J=8.1, 2.1 Hz, 1H), 8.85 (d, J=2.1 Hz, 1H), 9.75 (s, 1H). 13C NMR; d 153.8,
152.4, 150.3, 149.0, 148.6, 146.9, 134.1, 132.7, 130.0, 126.5, 125.8, 123.5, 117.7,
112.0, 109.0, 60.8. EIMS (m/z, rel.int.); 351 (M+, 45), 335 (46), 318 (100), 271
(50). High resolution EIMS calcd. for C18H17N5O3: 351.13314. Observed
351.13815. (15 hydrochloride salt); mp 239–2418C dec. Anal. Calcd. for
C18H17N5O3-3.0HCl-0.7H2O: C, 45.67; H, 4.55; N, 14.79. Found: C, 45.64; H,
4.46; N, 14.65.
N-Methoxy-6-{5-[4-(N-methoxyamidino-phenyl]-furan-2-yl}-nicotinamidine-
d3 (16): The same procedure described for 6a was used, starting with 15 and
employing dimethyl sulfate-d6 instead of dimethyl sulfate. Free base of 16,
1
yield 60%, mp 168.5–169.58C. H NMR (DMSO-d6); d 3.79 (s, 3H), 6.14 (s,
2H), 6.30 (s, 2H), 7.24 (d, J=3.6 Hz, 1H), 7.30 (d, J=3.6 Hz, 1H), 7.77 (d,
J=8.4 Hz, 2H), 7.88 (d, J=8.4 Hz, 2H), 7.94 (d, J=8.4 Hz, 1H), 8.10 (dd,
J=8.4, 2.1 Hz, 1H), 8.86 (d, J=2.1 Hz, 1H). 13C NMR; d 153.7, 152.5, 150.5,
149.0, 148.5, 146.9, 134.1, 131.8, 130.3, 126.5, 126.2, 123.5, 117.8, 112.0, 109.2,
60.7. EIMS (m/z, rel.int.); 368 (M+, 100), 338 (10), 321 (15), 287 (35), 245 (10).
High resolution EIMS calcd. for C19H16D3N5O3: 368.16762. Observed
368.16933. (16 hydrochloride salt); mp 208–2108C. Anal. Calcd. for
Copyright # 2004 John Wiley & Sons, Ltd.
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242
M. A. ISMAIL AND D. W. BOYKIN
C19H16D3N5O3-3.0HCl-1.9H2O: C, 44.57; H+D as H, 5.04; N, 13.67. Found:
C, 44.51; H+D as H, 5.04; N, 13.42.
N-Methoxy-6-{5-[4-(N-methoxyamidino-phenyl]-furan-2-yl}-nicotinamidine-
d6 (18): The same procedure described for 6a was used, starting with 17 and
employing dimethyl sulfate-d6 instead of dimethyl sulfate. Free base of 18,
yield 57%, mp 168.5–1698C. 1H NMR (DMSO-d6); d 6.12 (s, 2H), 6.28 (s, 2H),
7.23 (d, J=3.6 Hz, 1H), 7.29 (d, J=3.6 Hz, 1H), 7.76 (d, J=8.4 Hz, 2H), 7.87
(d, J=8.4 Hz, 2H), 7.92 (d, J=8.4 Hz, 1H), 8.10 (dd, J=8.4, 2.1 Hz, 1H), 8.84
(d, J=2.1 Hz, 1H). 13C NMR; d 153.6, 152.5, 150.5, 149.0, 148.5, 146.9, 134.1,
131.8, 130.3, 126.5, 126.2, 123.5, 117.7, 112.0, 109.2. EIMS (m/z, rel.int.); 371
(M+, 100), 338 (20), 321 (25), 287 (35), 245 (5). High resolution EIMS calcd.
for C19H13D6N5O3: 371.18645. Observed 371.18789. (18 hydrochloride salt);
mp 225–226.58C. Anal. Calcd. for C19H13D6N5O3-3.0HCl-2.0H2O: C, 44.15;
H + D as H, 5.03; N, 13.55. Found: C, 44.24; H + D as H, 5.16; N, 13.49.
Acknowledgement
This work was supported by the Bill and Melinda Gates Foundation.
References
1. Tidwell RR, Boykin DW. Dicationic DNA minor groove binders as antimicrobial
agents. In Small Molecule DNA and RNA Binders: From Synthesis to Nucleic Acid
Complexes, Demeunynck M, Bailly C, Wilson WD. (eds), vol 2. Wiley-VCH: New
York, 2003; 416–460.
2. Boykin DW, Kumar A, Bender BK, Hall JE, Tidwell RR. Bioorg Med Chem Lett
1996; 6: 3017–3020.
3. Das BP, Boykin DW. J Med Chem 1976; 20: 531–536.
4. Steck EA, Kinnamon KE, Davidson DE, Duxbury RE, Johnson AJ, Masters RE.
Exp Parasitol 1982; 3: 133–134.
5. Zhou L, Voyksner RD, Stephans CE, Anbazhagen M, Boykin DW, Hall JE,
Tidwell RR. Rapid Commun Mass Spectrosc 2002; 16: 1078–1085.
6. Zhou L, Lee K, Thakker DR, Boykin DW, Tidwell RR, Hall JE. Pharmaceut Res
2002; 19: 1689–1695.
7. Stephens CE, Patrick DA, Chen H, Tidwell RR, Boykin DW. J Label Compd
Radiopharm 2001; 44: 197–208.
8. Ismail MA, Brun R, Easterbrook JD, Tanious FA, Wilson WD, Boykin DW.
J Med Chem 2003; 46: 4761–4769.
Copyright # 2004 John Wiley & Sons, Ltd.
J Label Compd Radiopharm 2004; 47: 233–242