SYNTHESIS OF 3-(4-PYRIDINYL)-, 3-(2-CHLORO-4-PYRIDINYL)- AND 3-(2-AMINO-4-PYRIDINYL)PROPOXYMETHANEPHOSPHONIC ACID

Article abstract of DOI:10.1135/cccc19950670

Reaction of sodium salt of 4-(3-hydroxypropyl)pyridine (I) with diisopropyl p-toluenesulfonyloxymethanesulfonate (II) afforded diisopropyl ester of the corresponding phosphonomethyl derivative (III) together with 4-cyclopropylpyridine (IV).The ester III w

Full text of DOI:10.1135/cccc19950670

670
Krecmerova, Holy, Masojidkova:
SYNTHESIS OF 3-(4-PYRIDINYL)-, 3-(2-CHLORO-4-PYRIDINYL)- AND
3-(2-AMINO-4-PYRIDINYL)PROPOXYMETHANEPHOSPHONIC ACID
Marcela KRECMEROVA, Antonin HOLY and Milena MASOJIDKOVA
Institute of Organic Chemistry and Biochemistry,
Academy of Sciences of the Czech Republic, 166 10 Prague 6, The Czech Republic
Received February 14, 1995
Accepted February 24, 1995
Reaction of sodium salt of 4-(3-hydroxypropyl)pyridine (I) with diisopropyl p-toluenesulfonyloxy-
methanephosphonate (II) afforded diisopropyl ester of the corresponding phosphonomethyl derivative
(III), together with 4-cyclopropylpyridine (IV). The ester III was converted into free 3-(4-pyri-
dinyl)propoxymethanephosphonic acid (V). The synthesis of 3-(2-amino-4-pyridinyl)propoxymethane-
phosphonic acid (XVI) started from 4-(3-benzoyloxypropyl)pyridine (VII) via the N-oxide VIII which
on heating with phosphoryl chloride afforded the 2-chloro derivative IX. Compound IX was deben-
zoylated with sodium methoxide to give 2-chloro-4-(3-hydroxypropyl)pyridine (XI). Condensation of
sodium salt of XI with tosylate II afforded diisopropyl 3-(2-chloro-4-pyridinyl)propoxymethanephos-
phonate (XIII) and 2-chloro-4-cyclopropylpyridine (XIV). Deprotection of the ester groups in XIII
with bromotrimethylsilane gave 3-(2-chloro-4-pyridinyl)propoxymethanephosphonic acid (XV). The
chlorine atom in position 2 was replaced by reaction of compound XV with aqueous ammonia at 200 °C
under catalysis with copper(II) sulfate. This gave 3-(2-amino-4-pyridinyl)propoxymethanephosphonic
acid (XVI) as the final product.
This study represents a continuation of our previous investigation devoted to the prepa-
ration of phosphonomethyl derivatives of acyclic nucleoside analogs. Particularly
important in this group of compounds proved to be certain adenine derivatives such as
9-(2-phosphonomethoxyethyl)adenine and (S)-9-(3-hydroxy-2-phosphonomethoxy-
propyl)adenine1,2, exhibiting high in vitro and in vivo antiviral activity2–6. Great num-
ber of related phosphonomethoxy compounds were prepared, modified in the
aliphatic7–9 as well as the heterocyclic10,11 part of the molecule, and their structure–activity
relationships were studied.
We focused our attention, inter alia, to the preparation of phosphonomethyl deriva-
tives formally derived from acyclic nucleoside analogs in which, however, the nucleo-
base is replaced by a simple heterocyclic system containing an amino group. Recently,
a related paper appeared dealing with the preparation of such derivatives of guanine
with an open imidazole ring12. Also our preceding paper concerns the synthesis of
phosphonomethyl ethers derived from aminophenethyl alcohols13. The present communi-
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

3-(4-Pyridinyl)propoxymethanephosphonic Acid
671
cation describes derivatives containing a phosphonomethoxy- propyl group attached to a
pyridine system.
As the starting compound we have chosen 3-(4-pyridinyl)propanol (I) which was
prepared in high yield by the reaction of 4-picoline with ethylene oxide in the presence
of sodium amide14. Sodium salt of 3-(4-pyridinyl)propanol reacted with diisopropyl
p-toluenesulfonyloxymethanephosphonate (II, ref.15) to give the desired phosphono-
methyl derivative in the form of diisopropyl ester III. The yield of this product was
significantly reduced by formation of 4-cyclopropylpyridine (IV) which represented the
principal product (the ratio IV to III was about 3 : 1). Although the ratio of IV to III
could be somewhat improved by modification of the reaction conditions, e.g. by work-
ing at lower temperature, the cyclopropyl derivative still remained the main reaction
product. Reaction of the diisopropyl ester III with bromotrimethylsilane afforded free
3-(4-pyridinyl)propoxymethanephosphonic (V).
Our main goal, however, was the synthesis of a phosphonomethyl derivative analo-
gous to compound V which would contain an amino group in the position 2 of the
pyridine ring. The simplest approach seemed to be the Chichibabin amination of alco-
hol I protected with a suitable alkali-stable group. To this end, we synthesized trityl
derivative VI by reaction of compound I with trityl chloride in pyridine. Whereas
various 4-alkylpyridines, such as 4-propylpyridine, undergo the Chichibabin reaction
affording the corresponding 2-amino derivatives in high yields16, in our case heating
the trityl derivative VI with sodium amide in xylene in the presence of N,N-dimethyl-
aniline gave 4-cyclopropylpyridine (IV) as the sole reaction product.
An alternative approach to the 2-amino derivatives consists in the introduction of a
suitable substituent into the position 2, which subsequently could be transformed into
the amino group. Such a substituent might be e.g. a halogen or azido group. Therefore,
we first converted the starting 3-(4-pyridinyl)propanol (I) into benzoyl derivative VII
which on heating with peroxyacetic acid afforded 4-(3-benzoyloxypropyl)pyridine
N-oxide (VIII). The obtained N-oxide VIII reacted with phosphoryl chloride to give
4-(3-benzoyloxypropyl)-2-chloropyridine (IX). The reaction was accompanied with
chlorination of the side chain under formation of 4-(3-benzoyloxy-1-chloropropyl)-
pyridine (X). The products were obtained in the ratio 1 : 1, however, they could be
easily separated by chromatography. The formation of the side chain-chlorinated deri-
vative is analogous to the situation described for reactions of other alkylpyridine N-oxides
with phosphoryl chloride17,18. Our attempts to find other methods leading to the
2-chloro derivative IX without formation of the compound X were unsuccessful. The
recommended method, consisting in heating pyridine N-oxides with sulfuryl
chloride19,20 in a pressure vessel, in our case gave only negligible yield of the 2-chloro
derivative IX. Most of the compound underwent deep degradation to a complex mixture
of polar products. Unsuccessful was also the reaction of N-oxide VIII with phosphorus
trichloride and an attempted preparation of the 2-bromo derivative by reaction of VIII
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

672
Krecmerova, Holy, Masojidkova:
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

3-(4-Pyridinyl)propoxymethanephosphonic Acid
673
with bromotrimethylsilane. In both cases the reaction mixture contained only the un-
changed N-oxide even after several hours of heating.
As an alternative approach, we tried to introduce an azido group into position 2 and
to reduce it to the amine. However, attempts to prepare the azido derivative from N-oxide
VIII by reaction with sodium azide or trimethylsilyl azide were also without success.
Similarly, attempted replacement of chlorine with the azido group in compound IX by
prolonged heating with sodium or lithium azide in dimethylformamide gave no product.
The only successful procedure leading to the 2-amino derivative XII was direct sub-
stitution of the chlorine atom with ammonia under conditions described by Wibaut and
Nicolai21 for 2-chloropyridine: the benzoylated 2-chloro derivative IX on reaction with
sodium methoxide was converted into 2-chloro-4-(3-hydroxypropyl)pyridine (XI)
which was then heated with concentrated aqueous ammonia under high pressure and
temperature in the presence of copper(II) sulfate to afford the desired 2-amino-4-(3-hydroxy-
propyl)pyridine (XII). Because of instability of this compound due to easy oxidation of
the amino group, it was better to prepare the phosphonomethyl derivative not from the
compound XII but to synthesize first the 2-chloro substituted phosphonate and to re-
place the chlorine atom by the amino group only in the free phosphonomethyl deriva-
tive as the last synthetic step.
Reaction of sodium salt of 2-chloro-4-(3-hydroxypropyl)pyridine (XI) with diisopro-
pyl p-toluenesulfonyloxymethanephosphonate (II) gave the desired phosphonate in the
form of its diisopropyl ester XIII, together with 2-chloro-4-cyclopropylpyridine (XIV).
The presence of the chlorine atom in position 2 enhanced strongly the propensity to
formation of the cyclopropyl derivative. Whereas the analogous reaction with unsub-
stituted 4-(3-hydroxypropyl)pyridine (I) can be performed at room temperature, with
the 2-chloro derivative XI the reaction mixture must be cooled (−20 to −10 °C) and the
reaction has to be monitored by thin-layer chromatography. At temperatures higher
than −5 °C the cyclopropyl derivative XIV was practically the sole reaction product.
Reaction of the ester XIII with bromotrimethylsilane afforded free 3-(2-chloro-4-pyri-
dinyl)propoxymethanephosphonic acid (XV). The replacement of the chlorine atom by
amino group was carried out analogously as described for compound XI, i.e., by cop-
per(II) sulfate-catalyzed reaction with aqueous ammonia at high temperature and press-
ure. In this way, we obtained 3-(2-amino-4-pyridinyl)propoxymethanephosphonic acid
(XVI) as the final product in a relatively high yield (57%).
1
The structure of the compounds was determined by H and 13C NMR spectra and
further confirmed by elemental analysis or mass spectrometry. The 13C NMR spectra of
the individual compounds are listed in Table I.
The antiviral activity and cytotoxicity of free phosphonomethyl derivatives was
tested in cell cultures. Compound V was inactive to herpes simplex viruses (HSV-1,
HSV-2), vesicular stomatitis virus (VSV), vaccinia virus (VV) and RNA viruses. The
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

674
Krecmerova, Holy, Masojidkova:
compound is not cytotoxic22. The biological assays of compounds XV and XVI are still
under way.
EXPERIMENTAL
Unless stated otherwise, solvents were evaporated at 40 °C/2 kPa and compounds were dried over
phosphorus pentoxide at 13 Pa. Thin-layer chromatography was performed on Silufol UV 254 foils
(Kavalier, The Czech Republic). The solvent systems are specified in the text. Spots were detected
by UV light at 254 nm or by spraying with 0.5% solution of 4-(4-nitrobenzyl)pyridine in ethanol
with subsequent heating and exposure to ammonia vapours. Preparative column chromatography was
carried out on silica gel (30 – 60 µm, Service Laboratories of the Institute), reversed-phase chroma-
tography on octadecyl-silica gel (20 µm, Laboratorni Pristroje, Prague) with a gradient of methanol;
detection with a Uvicord 4701 A (LKB, Sweden) instrument at 254 nm. Electrophoresis was per-
formed on a Whatman No 3MM paper in 0.1 M triethylammonium hydrogen carbonate for 1 h at 20 V/cm.
The electrophoretic mobilities given in the text (EAMP) are referenced to adenosine 5′-phosphate.
1H NMR spectra (δ, ppm; J, Hz) were measured on Varian UNITY-200 (200.01 MHz) and Varian
TABLE I
13C NMR chemical shifts (δ, ppm) of compounds III – XVI
Compound
C-2
C-3
C-4
C-5
C-6
C-1′
C-2′
C-3′
IIIa
IV
Vb
149.73
149.41
144.02
149.54
149.72
138.50
150.67
150.33
150.59
150.65
150.66
150.58
155.05
124.18
120.84
125.47
124.11
124.06
126.62
124.27
122.21
124.25
124.26
120.94
124.22
111.25
150.80
153.61
158.14
150.65
150.31
139.64
154.84
149.58
155.73
155.13
158.21
155.43
155.01
124.18
120.84
125.47
124.11
124.06
126.62
123.57
122.21
123.62
123.61
120.20
123.67
112.93
149.73
149.41
144.02
149.54
149.72
138.50
149.85
150.33
149.80
149.86
149.53
149.76
145.77
30.95
14.65
30.98
29.93
31.04
30.11
30.87
58.63
30.76
30.65
14.70
30.74
30.73
29.72
10.71
28.41
31.18
28.77
28.80
28.55
37.13
32.95
29.37
11.28
29.65
28.95
71.69
–
71.29
62.08
64.08
64.03
64.13
61.87
59.90
71.50
–
VI
VII
VIII
IX
X
XI
XIIIc
XIV
XVd
XVIe
70.90
71.85
a
Other data: 71.69 d, J(P,C) = 11.7 (C-3′); 70.34 d, J(P,C) = 5.9 (POC); 64.89 d, J(P,C) = 165.0
b
(PC); 24.05 d, J(P,C) = 3.9 (CH3); 23.95 d, J(P,C) = 4.9 (CH3). 71.29 d, J(P,C) = 10.7 (C-3′);
66.63 d, J(P,C) = 155.3 (PC). c 71.50 d, J(P,C) = 10.7 (C-3′); 70.26 d, J(P,C) = 5.8 (POC); 64.83 d,
J(P,C) = 164.1 (PC); 24.01 d, J(P,C) = 3.9 (CH3); 23.91 d, J(P,C) = 4.9 (CH3). d 70.90 d, J(P,C) = 10.7
(C-3′); 68.18 d, J(P,C) = 159.2 (PC). e 71.85 d, J(P,C) = 11.0 (C-3′); 68.42 d, J(P,C) = 149.4 (PC).
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

3-(4-Pyridinyl)propoxymethanephosphonic Acid
675
UNITY-500 (499.8 MHz) instruments in hexadeuteriodimethyl sulfoxide with tetramethylsilane as in-
ternal standard. NMR spectra of compounds V and XVI were taken in deuterium oxide with sodium
3-(trimethylsilyl)-1-propanesulfonate (DSS) as reference. The carbon signals were referenced to the
solvent signal (δ13C (DMSO) = 39.7) or to dioxane as external standard (δ 13C (dioxane) = 66.86) for
solutions in deuterium oxide. Mass spectra were taken on a ZAB-EQ (VG Analytical) spectrometer
using EI (electron energy 70 eV) or FAB (xenone, 8 kV) techniques with glycerol (G) or thioglycerol
(TG) as matrices.
Bis(2-propyl) 3-(4-Pyridinyl)propoxymethanephosphonate (III)
Sodium hydride (60% suspension in oil; 1.76 g, 44 mmol) was added to a solution of alcohol I (2.04 g,
14.9 mmol) in dimethylformamide (70 ml) and the mixture was stirred at room temperature for 30 min.
Tosylate II (7.82 g, 22.3 mmol) was added to the formed suspension of the sodium salt and the stir-
ring at room temperature was continued for 1.5 h. The mixture was neutralized by addition of acetic acid
(2 ml), the solvent was evaporated and the residue was partitioned between water (400 ml) and ethyl
acetate (600 ml). The organic layer was dried over magnesium sulfate, taken down and the residue
was chromatographed on silica gel (750 ml) in ethyl acetate–acetone–ethanol–water (18 : 3 : 1 : 1),
RF 0.40. Yield 1.19 g (25%) of phosphonate III. For C15H26NO4P (315.4) calculated: 57.13% C,
8.31% H, 4.44% N, 9.82% P; found: 56.86% C, 8.60% H, 4.14% N, 9.55% P. Mass spectrum (FAB,
1
CHCl3), m/z: 316 (M + H). H NMR spectrum: 1.24 d, 6 H and 1.25 d, 6 H, J(CH3,CH) = 6.1 (CH3);
1.82 m, 2 H (2′-CH2); 2.62 dd, 2 H, J(1′,2′) = 6.3 and 8.5 (1′-CH2); 3.50 t, 2 H, J(3′,2′) = 6.3 (3′-CH2);
3.71 d, 2 H, J(P,CH) = 8.3 (PCH2); 4.60 d sept, 2 H, J(CH,CH3) = 6.1, J(P,OCH) = 7.8 (POCH);
7.23 d, 2 H, J = 6.1 (H-3 and H-5 pyridine); 8.44 d, 2 H, J = 6.1 (H-2 and H-6, pyridine).
4-Cyclopropylpyridine (IV)
This compound was obtained as the chromatographically more mobile product in the preparation of
diester III. Yield 1.3 g (73%), RF 0.70 (ethyl acetate–acetone–ethanol–water 18 : 3 : 1 : 1). Mass
spectrum (FAB, G + dimethyl sulfoxide), m/z: 120 (M + H). 1H NMR spectrum: 0.77 m, 2 H and
1.04 m, 2 H (2′-CH2); 1.90 tt, 1 H, J(1′,2′-trans) = 5.1, J(1′,2′-cis) = 8.3 (1′-CH); 7.06 d, 2 H, J = 6.1
(H-3 and H-5, pyridine); 8.36 d, 2 H, J = 6.1 (H-2 and H-6, pyridine).
3-(4-Pyridinyl)propoxymethanephosphonic Acid (V)
Bromotrimethylsilane (4.5 ml, 34 mmol) was added in an argon atmosphere to a solution of diisopro-
pyl ester III (1.14 g, 3.6 mmol) in acetonitrile (15 ml) and the mixture was stirred for 24 h in the
dark. The reaction mixture was adjusted to neutrality with 1 M triethylammonium hydrogen carbonate
and the solvent was evaporated. The residue was codistilled with water (50 ml), dissolved in water
(5 ml) and applied onto a column of DEAE-Sephadex A-25 (300 ml; HCO−3 form). The column was
washed with water (1 000 ml) and then with a gradient of triethylammonium hydrogen carbonate
(0 – 0.4 mol/l; 1 000 ml). The product was eluted at buffer concentration 0.2 – 0.3 mol/l. The pro-
duct fractions were evaporated, the residue was codistilled with water (3 × 100 ml) and then purified
by chromatography on a reversed phase (C-18). The pure product was eluted with water, the product
fractions were concentrated to 3 ml and applied onto a column of Dowex 50 (Li+ form; 50 ml). The
column was washed with water. Fractions containing the lithium salt of phosphonate V were evap-
orated, the solid residue was triturated with a methanol–acetone mixture, collected on filter and dried
in vacuo. Yield 400 mg (42%), RF 0.18 (2-propanol–25% aqueous ammonia–water 7 : 1 : 2); EAMP
1.18. For C9H12Li2NO4P . H2O (261.1) calculated: 41.41% C, 5.40% H, 5.36% N, 11.86% P; found:
41.11% C, 5.52% H, 5.23% N, 11.75% P. Mass spectrum (FAB, H2O), m/z: 244 (M + H, dilithium
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

676
Krecmerova, Holy, Masojidkova:
salt), 238 (M + H, monolithium salt), 232 (M + H, free acid). 1H NMR spectrum: 1.96 m, 2 H (2′-
CH2); 2.84 bt, 2 H, J(1′,2′) = 7.6 (1′-CH2); 3.60 d, 2 H, J(P,CH) = 8.7 (PCH2); 3.61 t, 2 H, J(3′,2′)
= 6.4 (3′-CH2); 7.56 d, 2 H, J = 5.5 (H-3 and H-5, pyridine); 8.48 d, 2 H, J = 5.5 (H-2 and H-6,
pyridine).
4-(3-Triphenylmethoxypropyl)pyridine (VI)
Trityl chloride (20.4 g, 73 mmol) was added to a solution of alcohol I (8.76 g, 63.86 mmol) in dry
pyridine (110 ml) and the solution was stirred at room temperature for 48 h. Crystalline pyridine
hydrochloride separated during the reaction. The reaction mixture was slowly added into ice-cold
water (1.5 l). After standing in a refrigerator for 16 h, the solid product was collected and dissolved
in chloroform (1 l). The chloroform solution was washed with water (2 × 500 ml), dried over mag-
nesium sulfate, the solvent was evaporated and the residue crystallized from 2-propanol–methanol. Yield
20.6 g (85%) of crystalline trityl derivative VI, m.p. 110 °C, RF 0.33 (toluene–ethyl acetate 3 : 1). For
C27H25NO (379.5) calculated: 85.45% C, 6.64% H, 3.69% N; found: 85.47% C, 6.62% H, 3.60% N.
Mass spectrum (FAB, CHCl3), m/z: 380 (M + H), 243 (trityl). 1H NMR spectrum: 1.87 m, 2 H (2′-CH2);
2.67 t, 2 H, J(1′,2′) = 7.5 (1′-CH2); 2.96 t, 2 H, J(3′,2′) = 6.3 (3′-CH2); 7.14 d, 2 H, J = 6.1 (H-3
and H-5, pyridine); 7.20 – 7.40 m, 15 H (H-trityl); 8.38 d, 2 H, J = 6.1 (H-2 and H-6, pyridine).
3-(4-Pyridinyl)propyl Benzoate (VII)
Benzoyl chloride (21 ml, 181 mmol) was added at 0 °C to a solution of alcohol I (20.48 g, 149.3 mmol)
in pyridine (100 ml). The mixture was stirred at 0 °C for 30 min and then at room temperature for 3 h.
Ethanol (30 ml) was added and the solvent evaporated. The residue was partitioned between water
(400 ml) and ethyl acetate (750 ml), the organic phase was washed with water (2 × 400 ml), dried
over magnesium sulfate and taken down. The thus-obtained liquid benzoate VII (40 g) was used in
the preparation of N-oxide VIII without further purification. For characterization, a sample (200 mg)
was chromatographed on silica gel (40 ml) in ethyl acetate (RF 0.46) to give 150 mg of pure ben-
zoate VII as a yellowish liquid. For C15H15NO2 (241.3) calculated: 74.67% C, 6.27% H, 5.80% N;
found: 74.49% C, 6.45% H, 5.65% N. Mass spectrum (FAB, dimethyl sulfoxide), m/z: 242 (M + H).
1H NMR spectrum: 2.06 m, 2 H (2′-CH2); 2.76 dd, 2 H, J(1′,2′) = 7.0 and 8.2 (1′-CH2); 4.28 t, 2 H,
J(3′,2′) = 6.4 (3′-CH2); 7.28 d, 2 H, J = 5.8 (H-3 and H-5, pyridine); 7.48 – 7.72 m, 3 H and 7.91 m,
2 H (H-benzoyl); 8.46 d, 2 H, J = 5.8 (H-2 and H-6, pyridine).
4-(3-Benzoyloxypropyl)pyridine N-Oxide (VIII)
The benzoate VII from the preceding preparation was dissolved in a mixture of acetic acid (55 ml)
and 30% hydrogen peroxide (10 ml). The solution was heated at 75 °C for 8 h; during the heating
further portions of hydrogen peroxide (2 × 6 ml) were added. The reaction mixture was diluted with
water (500 ml) and the solvent was evaporated. The residue was codistilled with water (3 × 400 ml)
and ethanol (100 ml) and chromatographed on silica gel (1 500 ml) in ethyl acetate–acetone–ethanol–water
18 : 3 : 2 : 2 (RF 0.36). Yield 16 g (42%, based on compound I); in addition, the starting benzoate
VII (13 g; 36%) was also obtained. The product VII was a white crystalline hygroscopic compound.
Mass spectrum (FAB, chloroform), m/z: 258 (M + H). 1H NMR spectrum: 2.02 m, 2 H (2′-CH2);
2.73 t, 2 H, J(1′,2′) = 7.7 (1′-CH2); 4.27 t, 2 H, J(3′,2′) = 6.3 (3′-CH2); 7.30 d, 2 H, J = 6.8 (H-3
and H-5, pyridine); 7.52 t, 2 H, 7.65 t, 1 H and 7.94 d, 2 H (H-benzoyl); 8.12 d, 2 H, J = 6.8 (H-2
and H-6, pyridine).
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

3-(4-Pyridinyl)propoxymethanephosphonic Acid
677
3-[4-(2-Chloropyridinyl)]propyl Benzoate (IX)
Phosphoryl chloride (70 ml) was added to N-oxide VIII (11.7 g, 45.5 mmol) and the mixture was
refluxed for 3 h. After cooling, the excess phosphoryl chloride was distilled off in vacuo and the
residue was neutralized with a mixture of ice and 25% aqueous ammonia. The product was taken up
in ethyl acetate (500 ml), the organic layer was dried over magnesiun sulfate and the solvent was
evaporated. The residue was chromatographed on a column of silica gel (500 ml) in toluene–ethyl
acetate 2 : 1 (RF of benzoate IX 0.69). Yield 3.84 g (31%), slightly yellow liquid. For C15H14ClNO2
(275.7) calculated: 65.34% C, 5.12% H, 12.86% Cl, 5.08% N; found: 64.99% C, 5.03% H, 12.98% Cl,
1
5.12% N. Mass spectrum (FAB, CHCl3), m/z: 276 (M + H). H NMR spectrum: 2.06 m, 2 H (2′-CH2);
2.78 t, 2 H, J(1′,2′) = 7.6 (1′-CH2); 4.28 t, 2 H, J(3′,2′) = 6.3 (3′-CH2); 7.32 dd, 1 H, J(5,3) = 1.0,
J(5,6) = 5.1 (H-5, pyridine); 7.44 bs, 1 H (H-3, pyridine); 7.50 t, 2 H, 7.65 t, 1 H and 7.91 d, 2 H
(H-benzoyl); 8.28 bd, 1 H, J(6,5) = 5.1 (H-6, pyridine).
3-Chloro-3-(4-pyridinyl)propyl Benzoate (X)
The title compound was obtained as the chromatographically less mobile side product in the prepara-
tion of benzoate IX. Yield 5.14 g (41%); slightly yellow, light-sensitive liquid. RF 0.45 (ethyl
1
acetate–toluene 2 : 1). Mass spectrum (FAB, CHCl3), m/z: 276 (M + H). H NMR spectrum: 2.54 m,
2 H (2′-CH2); 4.36 pent, 1 H, J(3′a,2′) = 5.6, J(gem) = 12.2 (H-3′a); 4.40 ddd, 1 H, J(3′b,2′) = 5.6
and 7.1, J(gem) = 12.2 (H-3′b); 5.40 dd, 1 H, J(1′,2′) = 6.6 and 7.1 (1′-CH2); 7.49 t, 2 H (H-benzoyl);
7.54 d, 2 H, J = 6.1 (H-3 and H-5, pyridine); 7.65 t, 1 H and 7.91 d, 2 H (H-benzoyl); 8.20 d, 2 H,
J = 6.1 (H-2 and H-6, pyridine).
2-Chloro-4-(3-hydroxypropyl)pyridine (XI)
A solution of the benzoyl derivative IX (3.30 g, 12 mmol) was stirred with 0.1 M methanolic sodium
methoxide (200 ml) at room temperature for 2 h. The solution was neutralized with Dowex 50
(H+ form) to pH 7, the ion-exchanger was removed by filtration and washed on the filter with meth-
anol containing 1% of triethylamine until the UV absorption of the filtrate disappeared. The com-
bined filtrates were taken down and the residue was chromatographed on silica gel (260 ml) in ethyl
acetate (RF 0.46). Yield 1.87 g (91%) of alcohol XI (colourless sirup). Mass spectrum (FAB, T + G,
methanol), m/z: 172 (M + H). 1H NMR spectrum: 1.72 m, 2 H (2′-CH2); 2.65 t, 2 H, J(1′,2′) = 7.7
(1′-CH2); 3.39 td, 2 H, J(3′,2′) = 6.3, J(3′,OH) = 5.1 (3′-CH2); 4.55 t, 1 H, J(OH,3′) = 5.1 (OH); 7.26 dd,
1 H, J(5,3) = 1.5, J(5,6) = 5.1 (H-5, pyridine); 7.37 d, 1 H, J(3,5) = 1.5 (H-3, pyridine); 8.27 d, 1 H,
J(6,5) = 5.1 (H-6, pyridine).
2-Amino-4-(3-hydroxypropyl)pyridine (XII)
A mixture of 2-chloro derivative XI (268 mg, 1.6 mmol), 25% ammonium hydroxide (30 ml) and
copper(II) sulfate (50 mg) was heated in an autoclave at 220 °C for 17 h. After cooling, the solution
was taken down and the residue was mixed with a small amount (about 1 – 2 ml) of the solvent
system ethyl acetate–acetone–ethanol–water 18 : 3 : 2 : 2. The soluble portion was applied onto a
column of silica gel (25 ml) and chromatographed in the above-mentioned system. Yield 100 mg
(42%) of amorphous aminopyridine XII, RF 0.4. Mass spectrum (FAB, T + G, CH3OH), m/z: 153 (M + H).
1H NMR spectrum: 1.65 m, 2 H (2′-CH2); 2.41 t, 2 H, J(1′,2′) = 7.5 (1′-CH2); 3.39 t, 2 H, J(3′,2′) = 6.4
(3′-CH2); 4.50 br, 1 H (OH); 6.0 br, 2 H (NH2); 6.03 d, 1 H, J(5,6) = 5.0 (H-5, pyridine); 6.15 s, 1 H
(H-3, pyridine); 7.26 d, 1 H, J(6,5) = 5.0 (H-6, pyridine).
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

678
Krecmerova, Holy, Masojidkova:
Bis(2-propyl) 3-(2-Chloro-4-pyridinyl)propoxymethanephosphonate (XIII)
Tosylate II (4.59 g, 13 mmol) was added to a solution of alcohol XI (1.5 g, 8.74 mmol) in dimethyl-
formamide (20 ml), the solution was cooled to −20 °C and sodium hydride (60% dispersion; 1.05 g,
26 mmol) was added. The suspension was stirred at −20 °C for 15 min and then the temperature was
increased from −20 °C to −10 °C during 1 h. The reaction mixture was neutralized with acetic acid
(3.5 ml) and the solvent was evaporated. The residue was partitioned between water (200 ml) and
ethyl acetate (300 ml). The organic phase was dried over magnesium sulfate, the solvent was evaporated
and the residue was chromatographed on silica gel (200 ml) in ethyl acetate. The elution afforded
successively: cyclopropyl derivative XIV (RF 0.80), minor amount of unreacted starting alcohol XI
(RF 0.46; 205 mg, 14%), and then phosphonate XIII (RF 0.36). Yield of pure product XIII 800 mg
(26%). For C15H25ClNO4P (349.8) calculated: 51.51% C, 7.20% H, 10.14% Cl, 4.00% N, 8.85% P;
found: 51.23% C, 6.96% H, 9.92% Cl, 3.79% N, 8.56% P. Mass spectrum (FAB, T + G, chloro-
1
form), m/z: 350 (M + H). H NMR spectrum: 1.23 d, 6 H and 1.24 d, 6 H, J(CH3,CH) = 6.1 (CH3);
1.83 m, 2 H (2′-CH2); 2.65 t, 2 H, J(1′,2′) = 7.7 (1′-CH2); 3.49 t, 2 H, J(3′,2′) = 6.3 (3′-CH2); 3.71 d,
2 H, J(P,CH) = 8.1 (PCH2); 4.59 d sept, 2 H, J(CH,CH3) = 6.1, J(P,OCH) = 7.5 (POCH); 7.28 dd,
1 H, J(5,3) = 1.5, J(5,6) = 5.1 (H-5, pyridine); 7.38 d, 1 H, J(3,5) = 1.5 (H-3, pyridine); 8.29 bd, 1 H,
J(6,5) = 5.1 (H-6, pyridine).
2-Chloro-4-cyclopropylpyridine (XIV)
This compound was isolated as the side product in the preparation of phosphonate XIII; yield 0.4 g
1
(30%). H NMR spectrum: 0.85 m, 2 H and 1.08 m, 2 H (2′-CH2); 1.97 tt, 1 H, J(1′,2′-trans) = 4.9,
J(1′,2′-cis) = 8.3 (1′-CH)); 7.09 dd, 1 H, J(5,3) = 1.5, J(5,6) = 5.1 (H-5, pyridine); 7.23 d, 1 H, J(3,5) = 1.5
(H-3, pyridine); 8.19 d, 1 H, J(6,5) = 5.1 (H-6, pyridine).
3-(2-Chloro-4-pyridinyl)propoxymethanephosphonic Acid (XV)
Bromotrimethylsilane (3.3 ml, 25 mmol) was added in an argon atmosphere to a solution of com-
pound XIII (900 mg, 2.6 mmol) in acetonitrile (15 ml) and the solution was stirred in the dark for 20 h.
The reaction was quenched by addition of 1 M triethylammonium hydrogen carbonate to neutrality.
The solvent was evaporated, the residue was codistilled with water (2 × 40 ml), dissolved in water
(4 ml) and applied onto a column of DEAE-Sephadex A-25 (HCO−3 form; 300 ml). The column was
washed with water (600 ml) and then with a gradient of triethylammonium hydrogen carbonate
(0 – 0.5 mol/l; 1 000 ml). The product was eluted at concentration 0.3 – 0.4 mol/l. The product frac-
tions were combined, the solvent was evaporated and the residue was codistilled several times with
water until the decomposition of triethylammonium hydrogen carbonate was complete. The final
purification was performed by chromatography on a reversed phase (C-18); the product was eluted
with a gradient of methanol (0 – 100%). The pure phosphonate XV was eluted with 30% methanol.
Yield 650 mg (82%, about 1/3 of the compound as the bis(triethylammonium) salt), RF 0.20
(2-propanol–25% aqueous ammonia–water 7 : 1 : 2); EAMP 1.25. Mass spectrum (FAB, T + G, methanol),
m/z: 468 (M + H, bis(triethylammonium) salt), 367 (M + H, triethylammonium salt), 266 (M + H,
1
free acid). H NMR spectrum: 1.15 t, 6 H, J(CH3,CH2) = 7.3 (CH3); 1.78 m, 2 H (2′-CH2); 2.65 t, 2 H,
J(1′,2′) = 7.8 (1′-CH2); 2.94 q, 4 H, J(CH2,CH3) = 7.3 (CH2); 3.36 d, 2 H, J(P,CH) = 9.0 (PCH2);
3.41 t, 2 H, J(3′,2′) = 6.3 (3′-CH2); 7.28 dd, 1 H, J(5,3) = 1.5, J(5,6) = 5.1 (H-5, pyridine); 7.37 bs,
1 H (H-3, pyridine); 8.27 d, 1 H, J(6,5) = 5.1 (H-6, pyridine).
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

3-(4-Pyridinyl)propoxymethanephosphonic Acid
679
3-(2-Amino-4-pyridinyl)propoxymethanephosphonic Acid (XVI)
Copper(II) sulfate (120 mg) was added to a solution of compound XV (500 mg, 1.1 mmol) in 25%
aqueous ammonia (30 ml) and the mixture was heated at 200 °C for 18 h. After cooling, the solution
was saturated with hydrogen sulfide for 15 min. The precipitated copper sulfide was filtered
through Celite and the filtrate was taken down. The residue was chromatographed on a reversed
phase (C-18) in water. Because of the presence of small amounts of impurities (arising by oxidation
of the amino group) the chromatography was repeated under the same conditions. Yield 150 mg
(57%) of white solid, RF 0.16 (2-propanol–25% aqueous ammonia–water); EAMP 1.21. Mass spec-
trum (FAB, G + water), m/z: 247 (M + H). 1H NMR spectrum (D2O + NaOD): 1.88 m, 2 H (2′-CH2); 2.54 t,
2 H, J(1′,2′) = 7.6 (1′-CH2); 3.48 d, 2 H, J(P,CH) = 8.5 (PCH2); 3.60 t, 2 H, J(3′,2′) = 6.8 (3′-CH2); 6.30 bs,
1 H (H-3, pyridine); 6.48 dd, 1 H, J(5,3) = 1.5, J(5,6) = 5.6 (H-5 pyridine); 7.72 d, 1 H, J(6,5) = 5.6
(H-6, pyridine).
The authors are indebted to Professor E. De Clercq, Rega Institute, Catholic University, Leuven,
Belgium, for the antiviral tests. Their thanks are also due to Mrs A. Sterecova for the technical assist-
ance, to the staff of the Analytical Laboratory of the Institute (Dr V. Pechanec, Head) for the elemental
analyses and to the staff of the Central Laboratory of Mass Spectroscopy (Dr K. Ubik, Head) for the
mass spectra. This work was supported by Grant No. 203/93/0118 of the Czech Grant Agency, Grant No.
455407 of the Grant Agency of the Czech Academy of Sciences, and by Gilead Sciences (California,
U.S.A.).
REFERENCES:
1. De Clercq E., Holy A., Rosenberg I., Sakuma T., Balzarini J., Maudgal P. C.: Nature 323, 464
(1986).
2. Holy A., Rosenberg I.: Collect. Czech. Chem. Commun. 52, 2801 (1987).
3. Holy A., Votruba I., Merta A., Cerny J., Vesely J., Vlach J., Sediva K., Rosenberg I., Otmar M.,
Hrebabecky H., Travnicek M., Vonka V., Snoeck R., De Clercq E.: Antiviral Res. 13, 295
(1990).
4. De Clercq E., Holy A., Rosenberg I.: Antimicrob. Agents Chemother. 33, 185 (1989).
5. Bronson J. J., Kim C. U., Ghazzouli I., Hitchcock M. J. M., Kern E., Martin J. C. in: Nucleotides
as Antiviral Agents (J. C. Martin, Ed.), p. 72. American Chemical Society, Washington D.C.
1989.
6. Pauwels R., Balzarini J., Schols D., Baba M., Desmyter J., Rosenberg I., Holy A., De Clercq E.:
Antimicrob. Agents Chemother. 32, 1025 (1988).
7. Holy A.: Collect. Czech. Chem. Commun. 54, 446 (1989).
8. Jindrich J., Holy A., Dvorakova H.: Collect. Czech. Chem. Commun. 58, 1645 (1993).
9. Dvorakova H., Holy A., Rosenberg I.: Collect. Czech. Chem. Commun. 59, 2069 (1994).
10. Holy A., Rosenberg I., Dvorakova H.: Collect. Czech. Chem. Commun. 54, 2470 (1989).
11. Holy A., Rosenberg. I.: Nucleosides Nucleotides 8, 673 (1989).
12. Eger K., Klunder E. M., Schmidt M.: J. Med. Chem. 37, 3057 (1994).
13. Krecmerova M., Holy A.: Collect. Czech. Chem. Commun. 60, 659 (1995).
14. Cislak F. E.: U.S. 2,789,982 (1957); Chem. Abstr. 51, 12985 (1957).
15. Holy A.: Collect. Czech. Chem. Commun. 58, 649 (1993).
16. Solomon W.: J. Chem. Soc. 1946, 934.
17. Barnes J. H., Hartley F. R., Jones C. E. L.: Tetrahedron 38, 3277 (1982).
18. Ash M. L., Pews R. G.: J. Heterocycl. Chem. 18, 939 (1981).
Collect. Czech. Chem. Commun. (Vol. 60) (1995)

680
Krecmerova, Holy, Masojidkova:
19. Gilman H., Edward J. T.: Can. J. Chem. 31, 457 (1953).
20. Bobranski B., Kochanska L., Kowalewska A.: Chem. Ber. 71, 2385 (1938).
21. Wibaut J. P., Nicolai J. R.: Rec. Trav. Chim. 58, 709 (1939).
22. De Clercq E.: Unpublished results.
Collect. Czech. Chem. Commun. (Vol. 60) (1995)