Syntheses of novel modified acyclic purine and pyrimidine nucleosides as potential substrates of herpes simplex virus type-1 thymidine kinase for monitoring gene expression

Article abstract of DOI:10.1139/v04-005

Suicide gene therapy with the herpes simplex virus type-1 thymidine kinase gene (HSV-1 tk) is considered to be a promising approach to the treatment of cancer. Making use of the lower specificity of the viral enzyme compared to human thymidine kinase, the

Full text of DOI:10.1139/v04-005

513
Syntheses of novel modified acyclic purine and
pyrimidine nucleosides as potential substrates of
herpes simplex virus type-1 thymidine kinase for
monitoring gene expression
Michaela Grote, Steffi Noll, Bernhard Noll, Bernd Johannsen, and Werner Kraus
Abstract: Suicide gene therapy with the herpes simplex virus type-1 thymidine kinase gene (HSV-1 tk) is considered
to be a promising approach to the treatment of cancer. Making use of the lower specificity of the viral enzyme com-
pared to human thymidine kinase, the therapy involves the administration of antiviral agents (e.g., ganciclovir) as
prodrugs to induce enzymatic cell death in those cells that express the transferred gene. 18F-labelled derivatives have
been described for monitoring location, duration, and magnitude of the viral kinase enzyme activity by positron emis-
sion tomography (PET). Since an optimal radiotracer has not been developed, novel substances were synthesized for
monitoring gene expression. A group of 13 nucleoside analogues were synthesized, among them N1-methyl-9-[(1,3-
dihydroxy-2-propoxy)methyl]guanine (5) and N1-methyl-9-[(4-hydroxy)-3-hydroxymethylbutyl]guanine (7) as methyl an-
alogues of ganciclovir and penciclovir and their related fluoro compounds (6, 8). Further novel derivatives include N6-
methyl-9-[(1,3-dihydroxy-2-propoxy)methyl]-, N6-methyl-9-[(4-hydroxy)-3-hydroxymethylbutyl]adenine (9, 10), as well
as the uracil derivatives 5-hydroxy-1-[(1,3-dihydroxy-2-propoxy)methyl]uracil (11), 6-methyl-1-[(1,3-dihydroxy-2-
propoxy)-methyl]uracil (12), and its 3-fluoro-derivative (13).
Key words: fluorinated nucleoside analogues, gene therapy, PET, thymidine kinase.
Résumé : La thérapie à l’aide de gènes suicidaires dérivés du gène kinase de la thymidine du virus de type-1 de
l’herpès simplex (HSV-1 tk) est considérée comme une approche intéressante au traitement du cancer. En utilisant une
spécificité plus faible de l’enzyme viral par comparaison à celle de la kinase de la thymidine humaine, la thérapie im-
plique l’administration d’agents antiviraux (par exemple le ganciclovir) comme prodrogues pouvant induire la mort de
cellules enzymatiques dans les cellules qui expriment le gène transféré. Des dérivés marqués au 18F ont été décrits pour
la surveillance continue de la location, de la durée et du degré d’activité de l’enzyme kinase virale par tomographie à
émission de positron (« PET »). Considérant qu’un marqueur isotopique optimal n’a pas encore été développé, de nou-
velles substances ont été synthétisées pour la surveillance continue de l’expression génétique. On a synthétisé un
groupe de 13 analogues de nucléosides, dont la N1-méthyl-9-[(1,3-dihydroxy-2-propoxy)méthyl]guanine (5) et la N1-
méthyl-9-[(4-hydroxy)-3-hydroxyméthylbutyl]guanine (7) comme analogues méthylés du ganciclovir et du penciclovir et
les composés fluorés apparentés (6 et 8). On a aussi synthétisé d’autres dérivés nouveaux, dont les N6-méthyl-9-[(1,3-
dihydroxy-2-propoxy)méthyl]- et N6-9-[(4-hydroxy)-3-hydroxyméthylbutyl]adénine (9 et 10) ainsi que les dérivés uraci-
les 5-hydroxy-1-[(1,3-dihydroxy-2-propoxy)méthyl]uracile (11), 6-méthyl-1-[(1,3-dihydroxy-2-propoxy)méthyl]uracile
(12) ainsi que son dérivé 3-fluoro (13).
Mots clés : analogues fluorés du nucléoside, thérapie génétique, « PET », kinase de la thymidine.
[Traduit par la Rédaction] Grote et al. 523
Introduction
herpes simplex virus type-1 thymidine kinase gene (HSV-1
tk) (2, 3). This approach, which is also referred to as virus-
directed enzyme–prodrug therapy (VDEPT) (4) involves
gene delivery into replicating tumor cells, and after suffi-
cient expression of the enzyme herpes simplex virus type-1
Recently, transfer of genes for therapy has become more
of reality for the treatment of human malignancies (1). One
of the promising approaches is suicide gene therapy with the
Received 20 February 2002. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on 16 March 2004.
M. Grote,1 S. Noll, B. Noll, and B. Johannsen. Forschungszentrum Rossendorf, Institut für Bioanorganische und
Radiopharmazeutische Chemie, Postfach 510119, 01314 Dresden, Germany.
W. Kraus. Bundesanstalt für Materialforschung und -prüfung, Röntgenstruktur- und Phasenanalyse, Richard-Willstätter-Str. 11,
12489 Berlin, Germany.
1Corresponding author (e-mail: m.grote@fz-rossendorf.de)
Can. J. Chem. 82: 513–523 (2004)
doi: 10.1139/V04-005
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Fig. 1. Ganciclovir 1, FHPG 2, penciclovir 3, FHBG 4, and their related analogues 5–8; acyclic derivatives of N6-methyladenine 9, 10
and the pyrimidines 11–13.
thymidine kinase (HSV-1 TK), treatment with a prodrug,
which is converted to a cell-toxic product by the viral en-
zyme.
fluorine for hydroxyl involves protection of one of the
hydroxyl groups of the acyclic chain and, in the case of gua-
nine derivatives, also the protection of the amino group in
the 2-position, followed by introduction of a leaving group
for the fluorination.
Unlike the highly substrate-specific human TK, the viral
enzyme (HSV-1 TK) accepts a diversity of pyrimidine- and
purine-based nucleoside analogues, converting them into
monophosphates. Subsequent phosphorylation by human
(host) kinases leads to triphosphates that inhibit DNA poly-
merase and induce cell death. Inadequate site specific trans-
fection and gene expression are some of the issues in gene
therapy (5). Positron emission tomography (PET), a clini-
cally valuable diagnostic modality for a noninvasive visual-
ization of tissue functions in vivo, offers a possibility to
monitor location and magnitude of gene expression, thereby
helping to optimize protocols of gene and prodrug adminis-
tration in humans. Fluorine-18, with a half-life of 110 min,
is the most common isotope used for PET. Several nucleo-
side analogues labeled with 18F for monitoring suicide gene
therapy mediated by HSV-1 tk have been synthesized. They
are usually derivatives of acyclonucleosides, which are se-
lective anti-herpes agents, among them 9-[(3-[18F]-fluoro-1-
hydroxy-2-propoxy)methyl]guanine ([18F]FHPG) 2, derived
from ganciclovir (GCV) 1, and 9-[4-[18F]-fluoro-3-hydroxy-
methylbutyl]guanine ([18F]FHBG) 4, derived from penci-
clovir 3 (6–11). Phosphorylation of these radioactive-labeled
nucleoside analogues by virus-encoded thymidine kinase
leads to metabolites trapped within the infected tumor cells,
and the ensuing accumulation of radioactivity allows moni-
toring of the enzyme activity with PET (12).
Chemistry
Many methods for the preparation of acyclic nucleoside
analogues have been described. In most cases they involve
synthesis of a suitably protected side chain, followed by
coupling to the nucleobase and subsequent deprotection. For
example, Martin et al. (14) started from epichlorohydrin to
obtain GCV via condensation of 2-O-(acetoxymethyl)-1,3-
di-O-benzylglycerol with N2-9-diacetylguanine. We used
1,3-dichloro-2-propanol, sodium hydride, and benzyl alcohol
to produce 1,3-dibenzyloxy-2-propanol, which was added to
1,2-dichloroethane followed by paraformaldehyde and
hydrogen chloride gas, to obtain 1,3-dibenzyloxy-2-chloro-
methoxypropane (15) (15, 16). N6-Methyladenine 14 was
coupled to 15 in dry dimethyl formamide with triethyl amine.
Compound 14 may react with 15 either at the 7-position or
the 9-position of the purine ring, but additional heating of
the reaction mixture afforded only 16. Treatment with
palladium oxide in cyclohexene removed the benzyl protec-
tion groups, yielding N6-methyl-9-[(1,3-dihydroxy-2-pro-
poxy)methyl]adenine (9) (15, 16). The structure of 9 was
1
assigned by its H NMR spectra as the 9-isomer. It was
found that the chemical shifts resulting from the H2C(1′)
(5.64 ppm) and HC(8) (8.23 ppm) were in good agreement
with the almost similar compound 9-[(2-hydroxy-
ethoxy)methyl]adenine (5.67 and 8.27 ppm) (17); also the
NH shift of 9 amounted to 7.73 ppm, which was also analo-
gous to 9-[(2-hydroxyethoxy)methyl]adenine (~7.3 ppm),
taking into account that the downfield shift is caused by a
methyl group. Because our substance showed a weak
downfield shift, we synthesized the 9-substituted guanine
derivative. In contrast, the corresponding signals of 7-[(2-
hydroxyethoxy)methyl]adenine showed a strong downfield
In the search for improved PET radiotracers for gene ther-
apy monitoring, we have synthesized and characterized a se-
ries of novel acyclic nucleosides.
Here we report on the synthesis of acyclic analogues of
guanine (5–8) and adenine (9, 10), as well as the related py-
rimidines (11–13) (Fig. 1).
Guanine-based nucleoside analogues offer several possi-
bilities to be labeled with 18F, e.g., on the 8-position of the
purine ring (13) or by replacement of a hydroxyl group in
the side chain by fluorine (6, 10). Our strategy to replace
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Grote et al.
515
Scheme 1. Synthesis of compounds 9, 11, and 12.
shift (H2C(1′) = 5.79 ppm, HC(8) = 8.60 ppm, NH2
9.2 ppm resp. 10.0 ppm) (17).
=
Fig. 2. X-ray structure of 12.
Nucleoside analogues can also be prepared by a coupling
reaction of an activated base at the halogenated side chain
(18). The pyrimidine derivatives were synthesized by direct
condensation of the appropriate persilylated base with the
chloromethyl ether 15 and tetra-n-butylammonium iodide as
the catalyst to produce 5-hydroxy-1-[(1,3-dibenzyloxy-2-
propoxy)methyl]uracil (19) and 6-methyl-1-[(1,3-dibenzyl-
oxy-2-propoxy)methyl]uracil (20), respectively. Removal of
the benzyl protection groups with palladium oxide resulted
in 5-hydroxy-1-[(1,3-dihydroxy-2-propoxy)methyl]uracil (11)
and
6-methyl-1-[(1,3-dihydroxy-2-propoxy)methyl]uracil)
(12) (Scheme 1).
The molecular structure of 12 (Fig. 2) obtained by X-ray
analysis proved that the acyclic chain has been coupled with
the N1-position of the pyrimidine ring.
The precursor 6-methyl-1-[[1-(p-anisyldiphenylmethoxy)-
3-(p-toluenesulfonyloxy)-2-propoxy]methyl]uracil (22) was
obtained from 12 by treatment with p-anisylchloro-diphenyl-
methane in dimethyl formamide and with traces of dimethyl-
amino pyridine to produce 6-methyl-1-[[1-(p-anisyldiphenyl-
methoxy)-3-hydroxy-2-propoxy]methyl]uracil (21) in 47%
yield, followed by tosylation with tosyl chloride in anhy-
drous pyridine (63%). Fluorination with potassium fluoride
and Kryptofix® 2.2.2 in acetonitrile at 120 °C, afforded
6-methyl-1-[[1-(p-anisyldiphenylmethoxy)-3-fluoro-2-pro-
poxy]methyl]uracil (23) in a yield of 23%. Finally, the
protection group was removed, to give 63% of the fluori-
nated compound 6-methyl-1-[(3-fluoro-1-hydroxy-2-pro-
poxy)methyl]uracil (13) (Scheme 2).
purine derivative that is able to undergo highly
regioselective alkylation at the N-9 position, and transforma-
tion of the resulting alkylated purine derivative into the tar-
get compound. Some of the reported alkylating agents that
The carba-analogue of GCV (18, 19), penciclovir 3 can be
prepared by several procedures. There are three steps, in-
cluding the synthesis of a suitable side chain, coupling to a
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Can. J. Chem. Vol. 82, 2004
Scheme 2. Protection, tosylation, and subsequent fluorination of 12 to obtain 13.
Scheme 3. Synthesis of N6-methyl-9-[(4-hydroxy)-3-hydroxymethylbutyl]adenine (10).
Fig. 3. Several alkylation agents used for the preparation of
penciclovir.
Scheme 4. Methylation of ganciclovir and penciclovir.
have been used are for instance, 4-acetoxy-3-acetoxymethyl-1-
iodobutane (24) (20, 21), 4-acetoxy-3-(acetoxymethyl)butanol
(25) (22), and 2,2-dimethyl-5-(2-p-toluenesulfonyloxyethyl)-
1,3-dioxane (26) (23) (Fig. 3).
We used 5-(2-bromoethyl)-2,2-dimethyl-1,3-dioxane (27)
to synthesize both penciclovir 3 (21, 24) and N6-methyl-9-
[(4-hydroxy)-3-hydroxymethylbutyl]adenine (10), using hy-
drochloric acid under refluxing conditions for deprotection
(Scheme 3). The UV spectra of 10 and 9 were similar and
suggested that it was the N-9 isomer.
We decided to modify the substrate properties of GCV
and penciclovir by introducing a methyl group and therefore
changing the lipophilicity of the molecule (Scheme 4). As
described for acyclovir (25, 26), introduction of a methyl
group resulted in the alteration of the antiviral activities. The
desired products 5 and 7 were obtained from GCV 1 and
penciclovir 3 by treatment with methyl iodide in dimethyl
formamide followed by extensive preparative column chro-
matography.
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Grote et al.
517
Scheme 5. Methylation, followed by fluorination and splitting off of the protection groups to obtain 6 and 8.
To obtain N1-methylated guanine derivatives 6 and 8, we
Table 1. UV data for selected acyclic nucleo-
sides.
started from N2-(p-anisyldiphenylmethyl)-9-[[1-(p-anisyldi-
phenylmethoxy)-3-(p-toluenesulfonyloxy)-2-prop-oxy]methyl]-
guanine (29) or N2-(p-anisyldiphenylmethyl)-9-[(4-(p-
toluenesulfonyloxy))-3-p-anisyldiphenylmethoxy-methyl-
butyl]guanine (30), prepared by modified literature proce-
dures (6, 27). After reaction with methyl iodide yielding
44% of 31 and 29% of 32, fluorination followed. After fluo-
rination, the removal of the methoxytrityl group was carried
out. Details of both sysnthesis steps were described above
(Scheme 5).
No.
max nm (ε)
1
3
5
7
9
10
11
12
258 (13 500)
253 (11 400)
254 (10 400)
255 (7 900)
265 (13 900)
266 (13 600)
278 (7 500)
262 (11 200)
(sh) 274 (9000)
(sh) 274 (8100)
(sh) 273 (7800)
(sh) 272 (6200)
All synthesized substances were characterized by elemen-
1
tal analysis and H NMR spectroscopy, and derivatives con-
taining fluorine were also determined by 19F NMR. The UV
spectra of the compounds 3, 5, 7, and 9–13 are listed in Ta-
ble 1.
Experimental
Instrumentation and reagents
1H NMR spectra were obtained on a Varian Inova-400
(400 MHz) instrument with DMSO-d6 as an internal stan-
dard. The chemical shifts are given as δ in ppm, the coupling
constants as J in Hz. Fluorine 19F NMR spectra were ob-
tained on a Varian Inova-400 (376 MHz) with CFCl3 as the
internal standard. Elemental analyses were carried out with a
LECO CHNS 932 elemental analyzer. Melting points were
determined on a BOËTIUS melting point apparatus and are
uncorrected. UV spectra were recorded on a Specord UV–
vis S10 instrument (Zeiss) in aqueous solution.
The X-ray data were collected at room temperature
(293 K) on a SMART-CCD diffractometer (Siemens),
using graphite-monochromatized Mo-Kα radiation (λ =
0.71073 Å). A summary of the crystallographic data is given
in Table 2. The structure was solved by direct methods. All
hydrogen atoms were located by a difference Fourier synthe-
sis and refined freely. Empirical absorption corrections were
Radiochemistry
To obtain [18F]-labeled tracers the reaction conditions
must consider the half-life of fluorine-18 (110 min). We syn-
thesized the established [18F]FHPG (2) and [18F]FHBG (4)
(6–11), as well as the new tracers [18F]FMHPG (6) (N1-
methyl-9-[(3-[18F]-fluoro-1-hydroxy-2-propoxy)methyl]gua-
nine), [18F]FMHBG (8) (N1-methyl-9-(4-[18F]-fluoro-3-
hydroxymethyl-butyl)guanine), and [18F]FMHPU (13) (6-
methyl-1-[(3-[18F]-fluoro-1-hydroxy-2-propoxy)methyl]-ura-
cil. The tosylated and methoxytritylated precursors (22, 29–
32) were radiolabeled with a K[18F]F/Kryptofix® 2.2.2 com-
plex in acetonitrile, followed by splitting off the protection
groups under acidic conditions. The labeled products were
purified by HPLC. The synthesis time amounted to 90–
110 min, the radiochemical purity was >98%, and an aver-
age specific activity of 19 GBq/µmol were determined.
© 2004 NRC Canada

518
Can. J. Chem. Vol. 82, 2004
Table 2. Crystallographic data for X-ray diffraction studies of 6-
methyl-1-[(1,3-dihydroxy-2-propoxy)methyl]guanine (12).
Table 3. Position parameters of 6-methyl-1-[(1,3-dihydroxy-2-
propoxy)methyl]guanine (12) and the standard deviations.
12
x
y
z
Ueq
831(2)
3098(2)
572(2)
7617(1)
9173(2)
5521(1)
8793(2)
6765(1)
7782(2)
2490(1)
10398(2)
6143(2)
10133(2)
11602(1)
5134(2)
6459(2)
8514(2)
3713(2)
5069(2)
784(2)
Formula
C9H14N2O5·2H2O
N(3)
N(2)
O(7)
C(3)
O(8)
C(2)
O(2)
C(1)
C(6)
C(4)
O(1)
C(8)
O(3)
C(5)
C(9)
C(10)
OW2
OW1
3863(1)
5924(2)
2088(1)
3253(2)
5768(1)
5220(2)
1930(2)
5411(2)
3067(2)
4002(2)
6152(1)
2650(2)
1357(2)
1776(2)
3075(2)
1572(2)
1390(1)
–511(2)
38(1)
41(1)
45(1)
37(1)
57(1)
40(1)
55(1)
41(1)
45(1)
42(1)
60(1)
41(1)
64(1)
52(1)
50(1)
53(1)
51(1)
59(1)
fw
230.22
Triclinic
P-1
Crystal system
Space group
a (Å)
b (Å)
c (Å)
691(3)
2263(2)
2075(3)
1428(2)
2989(3)
–307(3)
1717(3)
3957(2)
2567(3)
4180(3)
–626(4)
2360(3)
3594(4)
4161(2)
2722(2)
6.867(2)
9.508(3)
10.493(4)
101.593(7)
107.857(6)
96.118(7)
626.3(4)
2
293(2)
1.217
0.100
244
α (°)
β (°)
γ (°)
V (Å3)
Z
Temperature (K)
d (g/cm3)
Absorption coefficient (mm–1)
F(000)
Wavelength (Å)
Crystal size (mm3)
2 θ Range (°)
Collection range
0.71073
8028(2)
1.5 × 0.6 × 0.4
2.10–25.00
–8 ≤ h ≤ 8
–7 ≤ k ≤ 11
–12 ≤ l ≤ 12
3100
Knauer, 8 mm × 250 mm) and an analytical C-18-column
(Eurospher, Knauer, 5 mm × 250 mm).
Solvents and reagents were purchased from the following
commercial sources and used without further purification:
Sigma, Fluka, Lancaster, Aldrich, and Merck.
Ganciclovir 1 was obtained by neutralization of the so-
dium salt (Cymeven™) with 0.1 mol L–1 HCl and recry-
stallization from water; penciclovir 3 was synthesized
according to a method of Harnden et al. (21). The precursors
29 and 30 were synthesized in modified procedures (10, 27).
Reflections collected
Independent reflections
2186 (Rint = 0.0344)
GoF
R (I > 2σ(I))
R1
0.984
0.0433
0.1243
wR2
R (all data)
R1
0.0530
0.1289
Syntheses of potential substrate and fluorinated
reference compounds
wR2
N1-Methyl-9-[(1,3-dihydroxy-2-propoxy)methyl]guanine (5)
Ganciclovir (1, 214 mg, 0.838 mmol) and
tetrabutylammonium hydroxide solution (1 mol L–1,
0.88 mL, 0.88 mmol) were dissolved in 20 mL of dry DMF
at room temperature. To this solution methyl iodide (120 µL,
1.93 mmol) in 1.2 mL DMF was slowly added and the mix-
ture was stirred for an additional 45 min. The solvent was
evaporated in vacuum and the crude product was purified by
MPLC (RP-18, acetonitrile–water (1:9, v/v)) to afford 5
(136 mg, 61%), mp 198–200 °C. 1H NMR (DMSO-d6)
δ: 7.79 (s, 1H, 8-CH), 7.04 (s, 2H, -NH2), 5.43 (s, 2H,
-H2C(1′)), 4.58 (t, 2H, J = 5.4 Hz, -OH), 3.53–3.50 (m, 1H,
-CH-O-), 3.44–3.38 (m, 2H, -CH2-), 3.32 (s, 3H, -NCH3),
3.29–3.24 (m, 2H, -CH2-). Anal. calcd. for C10H15N5O4: C
44.61, H 5.62, N 26.01; found: C 44.35, H 5.58, N 25.92.
made using ψ scans. Most of the calculations were carried
out in the SHELXTL system with some local modifications.
Position parameters and relevant bond lengths and angles
are contained in Tables 3 and 4. Atomic positional and ther-
mal parameters, full lists of bond lengths and angles, and
Fo/Fc values have been deposited as supplementary mate-
rial.2
Chromatographic purification was performed using either
Silica gel 60 (Merck) or RP-18 material (LiChroprepTM).
Furthermore, a MPLC (middle pressure liquid chromatogra-
phy) system (Knauer) with two columns (silica gel: Eurosil
Baselect, 25 mm × 200 mm, from Merck; RP-18 material,
30 × 480, from Kronlab) was used with pressures ranging
from 2 to 5 bar (1 bar = 100 kPa). HPLC analysis was per-
formed on a system using a PerkinElmer LC binary pump
250, UV detector (absorbance detector model 759A, Applied
Biosystems) operating at 254 nm, and a radioactivity detec-
tor using a semipreparative C-18-column (Eurospher,
N1-Methyl-9-[(3-fluoro-1-hydroxy-2-propoxy)methyl]gua-
nine (6) (FMHPG)
N1-Methyl-N2-(p-anisyldiphenylmethyl)-9-[[1-(p-anisyldi-
2 Supplementary data may be purchased from the Directory of Unpublished Data, Document Delivery, CISTI, National Research Council
Canada, Ottawa, ON K1A 0S2, Canada (http://www.nrc.ca/cisti/irm/unpub_e.shtml for information on ordering electronically). CCDC
210605 contains the crystallographic data for this manuscript. These data can be obtained, free of charge, via www.ccdc.cam.ac.uk/conts/re-
trieving.html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, U.K.; fax +44 1223 336033; or
deposit@ccdc.cam.ac.uk).
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Grote et al.
519
Table 4. Bond lengths (Å) and angles
for 6-methyl-1-[(1,3-dihydroxy-2-
propoxy)-methyl]guanine (12).
tion of methyl iodide (120 µL, 1.92 mmol) in 1.2 mL DMF
was added under vigorous stirring at room temperature. Af-
ter 2 h, the solvent was evaporated and the residue purified
by MPLC (RP-18, acetonitrile–water (1:9, v/v)) to obtain 7
(48 mg, 21%), mp 221–227 °C. 1H NMR (DMSO-d6) δ: 7.68
(s, 1H, 8-CH), 6.97 (s, 2H, -NH2), 4.42 (t, 2H, J = 5.2 Hz,
-OH), 3.98 (t, 2H, J = 7.4 Hz, -H2C(1′)), 3.44–3.38 (m, 4H,
-CH2(OH)), 3.29 (s, 3H, N-CH3), 1.69 (mc, 2H, -H2C(2′)),
1.45–1.40 (m, 1H, -CH(3′)). Anal. calcd. for C11H17N5O3: C
49.43, H 6.41, N 26.20; found: C 49.35, H 6.30, N 26.12.
Bond lengths (Å)
N(3)—C(2)
N(3)—C(3)
N(3)—C(6)
N(2)—C(2)
N(2)—C(1)
O(7)—C(6)
O(7)—C(8)
C(3)—C(4)
C(3)—C(5)
O(8)—C(2)
O(2)—C(9)
C(1)—O(1)
C(1)—C(4)
C(8)—C(10)
C(8)—C(9)
O(3)—C(10)
1.384(2)
1.394(2)
1.473(2)
1.371(2)
1.378(2)
1.408(2)
1.435(2)
1.343(2)
1.488(3)
1.219(2)
1.420(2)
1.233(2)
1.422(3)
1.500(3)
1.511(3)
1.422(2)
N1-Methyl-9-[(4-fluoro)-3-hydroxymethylbutyl]guanine (8)
(FMHBG)
N1-Methyl-N2-(p-anisyldiphenylmethyl)-9-[(4-fluoro)-3-p-
anisyldiphenylmethoxy-methyl-butyl]guanine (34, 58 mg,
0.072 mmol) was heated under reflux with 5 mL methanol
and 5 mL acetic acid (80%) for 4 h. The solvents were evap-
orated and the residue purified by MPLC (RP-18,
acetonitrile–water (2:8, v/v)) to give 8 (17 mg, 88%), mp
1
135–138 °C. H NMR (DMSO-d6) δ: 7.70 (s, 1H, 8-CH),
6.98 (s, 2H, -NH2), 4.68 (s, 1H, -OH), 4.55–4.34 (m, 2H,
-CH2-F), 4.01 (t, 2H, J = 7.2 Hz, -H2C(1′)), 3.39 (d, 2H, J =
6.4 Hz, -CH2(OH)), 3.29 (s, 3H, N1CH3), 1.78–1.67 (m, 2H,
-H2C(2′)), 1.65–1.61 (m, 1H, -HC(3′)). 19F NMR (DMSO-d6)
δ: –227.4. Anal. calcd. for C11H16N5O2F: C 49.06, H 5.99, N
26.01; found: 49.01, H 5.78, N 25.88.
Bond angles (°)
C(2)-N(3)-C(3)
C(2)-N(3)-C(6)
C(3)-N(3)-C(6)
C(2)-N(2)-C(1)
C(6)-O(7)-C(8)
C(4)-C(3)-N(3)
C(4)-C(3)-C(5)
N(3)-C(3)-C(5)
O(8)-C(2)-N(2)
O(8)-C(2)-N(3)
N(2)-C(2)-N(3)
O(1)-C(1)-N(2)
O(1)-C(1)-C(4)
N(2)-C(1)-C(4)
O(7)-C(6)-N(3)
C(3)-C(4)-C(1)
O(7)-C(8)-C(10)
O(7)-C(8)-C(9)
C(10)-C(8)-C(9)
O(2)-C(9)-C(8)
O(3)-C(10)-C(8)
121.52(14)
117.73(14)
120.73(14)
126.25(16)
115.35(13)
119.82(15)
122.00(16)
118.17(15)
121.44(17)
122.80(16)
115.76(15)
120.47(16)
125.00(17)
114.53(15)
111.99(14)
122.05(16)
107.02(16)
111.31(14)
112.51(16)
112.75(16)
113.39(16)
N6-Methyl-9-[(1,3-dihydroxy-2-propoxy)methyl]adenine (9)
Freshly activated palladium oxide (495 mg) and 10 mL
cyclohexene were added to a solution of N6-methyl-9-[(1,3-
dibenzyloxy-2-propoxy)methyl]adenine (16, 1.0 g,
2.3 mmol) in 20 mL ethanol and refluxed for 30 h. After
that, the reaction mixture was filtered and the solvent evapo-
rated. The residue was washed first with chloroform, then
with diethyl ether and dried. The crude product was
redissolved in hot water, ethanol was added, and the sub-
stance was allowed to precipitate when cooling down to give
1
9 (365 mg, 63%), mp 160 °C. H NMR (DMSO-d6) δ: 8.23
(s, 2H, 2-CH, 8-CH), 7.73 (s, 1H, -NH), 5.64 (s, 2H,
-H2C(1′)), 3.59 (t, 2H, J = 5.5 Hz, -OH), 3.59 (mc, 1H, -CH-O),
3.44–3.38 (m, 2H, -CH2(OH)), 3.31–2.94 (m, 2H, -CH2(OH)),
2.94 (s, 3H, NCH3). Anal. calcd. for C10H15N5O3: C 47.43,
H 5.97, N 27.65; found: C 47.37, H 5.86, N 27.52.
N6-Methyl-9-[(4-hydroxy)-3-hydroxymethylbutyl]adenine
(10)
phenylmethyl)-3-fluoro-2-propoxy]-methyl]guanine (33,
50 mg, 0.061 mmol) was heated under reflux in 5 mL meth-
anol and 5 mL acetic acid (80%) for 4.5 h. The solvent was
evaporated and the residue purified by MPLC (RP-18,
acetonitrile–water (1:9, v/v)) to give 6 (13 mg, 78%), mp
N6-Methyl-9-[(2,2-dimethyl-1,3-dioxane-5-yl)ethyl]purine
(28, 80 mg, 0.27 mmol) was dissolved in 1.5 mL methanol
and 1.5 mL HCl (2 mol L–1) and refluxed for 3 h. After
cooling, the solvent was reduced and the precipitate filtered
off. Crystallization from water gave 10 (23 mg, 34%), mp
1
216–219 °C. H NMR (DMSO-d6) δ: 7.81 (s, 1H, 8-CH),
1
134–136 °C. H NMR (DMSO-d6) δ: 8.22 (s, 1H, 8-CH),
7.08 (s, 2H, -NH2), 5.43 (s, 2H, -H2C(1′)), 4.89 (s, 1H, -OH),
4.54–4.27 (m, 2H, -CH2-F), 3.85–3.77 (m, 1H, -CH-O-), 3.32
(mc, 2H, -CH2-), 3.30 (s, 3H, -NCH3). 19F NMR (DMSO-d6)
δ: –231.0. Anal. calcd. for C10H14N5O3F: C 44.28, H 5.20, N
25.82; found: C 44.17, H 5.34, N 25.70.
8.14 (s, 1H, 2-CH), 7.73 (s, 1H, -NH-), 4.44 (s, 2H, -OH),
4.20 (t, 2H, J = 7.4 Hz, -H2C(1′)), 3.39 (mc, 4H, -CH2(OH)),
2.94 (s, 3H, NCH3), 1.78 (mc, 2H, -H2C(2′)), 1.44–1.40 (m,
1H, -HC(3′)). Anal. calcd. for C11H17N5O2: C 52.58, H 6.82,
N 27.87; found: C 52.43, H 6.73, N 27.72.
N1-Methyl-9-[(4-hydroxy)-3-hydroxymethylbutyl]guanine
(7)
Penciclovir (3, 231 mg, 0.841 mmol) and tetrabutyl-
ammonium hydroxide solution (1 mol L–1, 0.88 mL,
0.88 mmol) were dissolved in 20 mL of dry DMF. A solu-
5-Hydroxy-1-[(1,3-dihydroxy-2-propoxy)methyl]uracil (11)
5-Hydroxy-1-[(1,3-dibenzyloxy-2-propoxy)methyl]uracil
(19, 412 mg, 1.0 mmol) was refluxed with 6 mL of ethanol,
2.4 mL of cyclohexene, and freshly activated palladium ox-
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520
Can. J. Chem. Vol. 82, 2004
ide (170 mg, 1.40 mmol) for 17 h. The catalyst was filtered
off and washed with ethanol and water. The solutions were
collected and the solvents were removed. The residue was
purified by crystallization from ethanol to give 11 (111 mg,
5-Hydroxy-1-[(1,3-dibenzyloxy-2-propoxy)methyl]uracil
(19)
Isobarbituric acid (17, 384 mg, 3.0 mmol) was suspended
in 17 mL of hexamethyldisilazane. Ammonium sulfate
(225 mg, 1.70 mmol) was added and the mixture refluxed
for 70 min. The solvent was evaporated and the residue
suspended in 8 mL of dichloromethane, then tetra-n-butyl-
ammonium iodide (12.0 mg, 0.03 mmol) and 1,3-dibenzyl-
oxy-2-chloro-methoxypropane (15, 1.44 g, 4.5 mmol) were
added and the reaction mixture was refluxed for 90 min. Af-
ter cooling, the solution was treated with 4 mL of methanol
and 1 mL of water. The solvent was distilled off, the residue
solved in CH2Cl2, washed with satd. NaCl solution and wa-
ter. The organic layer was separated, dried, and the solvent
was evaporated. The purification of the reaction product oc-
curred by MPLC (silica gel, dichloromethane–methanol
(25:1, v/v)) resulting in 853 mg (69%) of a yellowish
1
48%), mp 147 to 148 °C. H NMR (DMSO-d6) δ: 11.43 (s,
1H, -NH), 8.68 (s, 1H, 6-CH), 7.14 (s, 1H, -OH), 5.09 (s,
2H, -H2C(1′)), 4.60 (s, 2H, -OH), 3.49 (m, 1H, -CH-), 3.45–
3.29 (m, 4H, -CH2(OH)). Anal. calcd. for C8H12N2O6: C
41.38, H 5.21, N 12.06; found: C 41.27, H 5.09, N 11.91.
6-Methyl-1-[(1,3-dihydroxy-2-propoxy)methyl]uracil (12)
6-Methyl-1-[(1,3-dibenzyloxy-2-propoxy)methyl]uracil
(20, 6.17 g, 15 mmol) was dissolved in 64 mL ethanol and
treated with freshly activated palladium oxide (2.0 g,
16.3 mmol), 20 mL cyclohexene, and stirred for 18 h at
room temperature. Afterwards the mixture was refluxed for
90 min and the catalyst was filtered. Precipitation of the
product proceeded when cooling and recrystallization from
1
viscous liquid of 19. H NMR (DMSO-d6) δ: 11.47 (s, 1H,
-NH), 8.72 (s, 1H, 6-CH), 7.32–7.22 (m, 10H, -CH(arom)),
7.17 (s, 1H, -OH), 5.14 (s, 2H, -H2C(1′)), 4.45 (s, 4H,
-CH2(Bz)), 3.96 (m, 1H, -CH-O), 3.51–3.42 (m, 4H, -CH2-
(OBz)). Anal. calcd. for C22H24N2O6: C 64.07, H 5.87, N
6.79; found: C 63.81, H 5.92, N 6.66.
1
ethanol gave 2.4 g (70%) of 12, mp 147–150 °C. H NMR
(DMSO-d6) δ: 11.20 (s, 1H, -NH), 5.50 (s, 1H, 5-CH), 5.23
(s, 2H, -H2C(1′)), 4.61 (t, 2H, J = 5.6 Hz, -OH), 3.51–3.47
(m, 1H, -CH-O), 3.45–3.39 (m, 2H, -CH2(OH)), 3.35–3.30
(m, 2H, -CH2(OH)), 2.29 (s, 3H, -CH3). Anal. calcd. for
C9H14N2O5: C 46.95, H 6.13, N 12.17; found: 46.77, H 6.09,
N 12.07.
6-Methyl-1-[(1,3-dibenzyloxy-2-propoxy)methyl]uracil (20)
6-Methyluracil (18, 378 mg, 3.0 mmol) was refluxed with
ammonium sulfate (150 mg, 1.14 mmol) and 11 mL of
hexamethyldisilazane. The solvent was removed and the res-
idue was dried. After dissolving the substance in CH2Cl2, it
was treated with tetra-n-butylammonium iodide (12 mg,
0.03 mmol). 1,3-Dibenzyloxy-2-chloromethoxypropane (15,
1.44 g, 4.5 mmol) was added, followed by refluxing for
70 min. The reaction mixture was cooled, 1 mL of water and
4 mL of methanol were added and after stirring for 2 min,
the solvent was removed. The residue was solved in CH2Cl2
and washed with satd. NaCl solution and water. The organic
layer was separated, dried, and the solvent was removed.
The reaction product was purified by column chromatogra-
phy (silica gel, dichloromethane–methanol (25:1, v/v)) to af-
6-Methyl-1-[(3-fluoro-1-hydroxy-2-propoxy)methyl]uracil
(13) (FMHPU)
6-Methyl-1-[[1-(p-anisyldiphenylmethoxy)-3-fluoro-2-
propoxy]methyl]uracil (23, 55.0 mg, 0.109 mmol) was dis-
solved in 5 mL of ethanol and 5 mL of 80% acetic acid and
refluxed for 1 h. The solvent was evaporated and the residue
was dissolved in ethanol. Final purification was carried out
with MPLC (RP-18, acetonitrile–water (1:4, v/v)) affording
13 (16.0 mg, 63%), mp 118–120 °C. 1H NMR (DMSO-d6) δ:
11.24 (s, 1H, -NH), 5.52 (s, 1H, 5-CH), 5.34 (d, 1H, J =
11.0 Hz, -H2C(1′)), 5.30 (d, 1H, J = 11.0 Hz, -H2C(1′)), 4.88
(s, 1H, -OH), 4.58–4.29 (m, 2H, -CH2-F), 3.78 (mc, 1H,
-CH-O-), 3.41 (d, 2H, J = 5.6, -CH2(OH)), 2.27 (s, 3H, 6-
CH3). 19F NMR (DMSO-d6) δ: –232.0. Anal. calcd. for
C9H13N2O4F: C 46.55, H 5.65, N 12.06; found: C 46.42, H
5.59, N 12.02.
1
ford 20 as yellow oil (426 mg, 35%). H NMR (DMSO-d6)
δ: 11.24 (s, 1H, -NH), 7.34–7.25 (m, 10H, -CH(arom)), 5.49
(s, 1H, 5-CH), 5.34 (s, 2H, -H2C(1′)), 4.45 (s, 4H, -CH2(Bz)),
3.95–3.93 (m, 1H, -CH-O), 3.49–3.43 (m, 4H, -CH2-(OBz)),
2.25 (s, 3H, -CH3). Anal. calcd. for C23H26N2O5: C 67.30, H
6.38, N 6.82; found: C 66.98, H 6.34, N 6.51.
N6-Methyl-9-[(1,3-dibenzyloxy-2-propoxy)methyl]adenine
(16)
Triethylamine (3.8 mL) was added to N6-methyladenine
(14, 3.7 g, 24.8 mmol) dissolved in 20 mL of dry DMF un-
der stirring. After addition of 1,3-dibenzyloxy-2-chloro-
methoxypropane (15, 8.0 g, 25.0 mmol) in 12.5 mL DMF,
the solution was stirred for 1 h at room temperature and then
heated for 3 h to 90 °C. The reaction mixture was cooled
down and the precipitated triethylammonium chloride was
removed. The solvent was evaporated and the residue puri-
fied by MPLC (RP-18, methanol–water (8:2, v/v)), yielding
6-Methyl-1-[[1-(p-anisyldiphenylmethoxy)-3-hydroxy-2-
propoxy]methyl]uracil (21)
6-Methyl-1-[(1,3-dihydroxy-2-propoxy)methyl]uracil (12,
460 mg, 2.00 mmol), p-anisylchloro-diphenylmethane
(672 mg, 2.18 mmol), triethylethylamine (418 µL,
3.00 mmol), and DMAP (2.9 mg) in 7 mL DMF were stirred
for 2 h at 50 °C. After removing the DMF, the residue was
dissolved in ethyl acetate, washed with NaHCO3 solution
and water. The combined organic layers were dried, the sol-
vent removed, and the crude product purified by chromatog-
raphy (silica gel, dichloromethane–methanol (25:1, v/v)) to
1
16 (3.4 g, 31%), mp 91 °C. H NMR (DMSO-d6) δ: 8.25 (s,
2H, 2-CH, 8-CH), 7.75 (s, 1H, -NH), 7.31–7.16 (m, 10H,
-CH(arom)), 5.66 (s, 2H, -H2C(1′)), 4.37 (s, 4H, -CH2(Bz)),
4.09 (m, 1H, -CH-O), 3.45–3.39 (m, 4H, -CH2-(OBz)), 2.95
(s, 3H, NCH3). Anal. calcd. for C24H27N5O3: C 66.50, H
6.28, N 16.15; found: C 66.25, H 6.08, N 16.06.
1
give 21 (468 mg, 47%), mp 83 °C. H NMR (DMSO-d6)
δ:11.31 (s, 1H, -NH), 7.36–6.86 (m, 14H, CH(arom)), 5.56
(s, 1H, 5-CH), 5.50 (d, 1H, J = 12.3 Hz, -H2C(1′)), 5.30 (d,
1H, J = 12.3 Hz, -H2C(1′)), 4.71 (t, 1H, J = 5.5 Hz, -OH),
© 2004 NRC Canada

Grote et al.
521
N1-Methyl-N2-(p-anisyldiphenylmethyl)-9-[[1-(p-anisyldi-
phenylmethoxy)-3-(p-toluene-sulfonyloxy)-2-propoxy]methyl]
guanine (31)
3.83 (mc, 1H, -CH-O), 3.73 (s, 3H, -OCH3), 3.36–3.30 (m,
2H, -CH2(OH)), 3.00–2.92 (m, 2H, -CH2-OMTr), 2.32 (s,
3H, -CH3). Anal. calcd. for C29H30N2O6: C 69.31, H 6.02, N
5.57; found: C 69.55, H 6.13, N 5.30.
N2-(p-Anisyldiphenylmethyl)-9-[[1-(p-anisyldiphenylmeth-
oxy)-3-(p-toluenesulfonyloxy)-2-prop-oxy]methyl]guanine
(29, 200 mg, 0.210 mmol), and tetrabutylammonium hy-
droxide solution (1 mol L–1, 0.22 mL, 0.22 mmol) were dis-
solved in 20 mL of dry DMF. A solution of methyl iodide
(30 µL, 0.48 mmol) in 0.30 mL DMF was added under vig-
orous stirring at room temperature. After 45 min, the solvent
was evaporated and the residue purified by MPLC (silica
gel, dichloromethane–methanol (25:1, v/v)) to afford 31
6-Methyl-1-[[1-(p-anisyldiphenylmethoxy)-3-(p-
toluenesulfonyloxy)-2-propoxy]methyl]-uracil (22)
21 (508 mg, 1.01 mmol) and tosyl chloride (858 mg,
4.50 mmol) were suspended in 12 mL pyridine and left for
70 h at 30 °C. Subsequently, 2 mL of water were added and
the reaction mixture was stirred for 2 h at 30 °C. The solvent
was evaporated, the residue dissolved in ethyl acetate, and
washed with water. The organic layer was dried, the solvent
removed and the reaction mixture purified by chromatogra-
phy (silica gel, dichloromethane–methanol (20:1, v/v)),
yielding 22 (420 mg, 63%), mp 79 °C. 1H NMR (DMSO-d6)
δ: 11.30 (s, 1H, -NH), 7.68 (d, 2H, J = 8.2 Hz, -CH, (m-Ts)),
7.41 (d, 2H, J = 8.2 Hz, -CH, (o-Ts)), 7.31–6.85 (m, 14H,
-CH(arom)), 5.52 (s, 1H, 5-CH), 5.33 (d, 1H, J = 12.1 Hz,
-H2C(1′)), 5.21 (d, 1H, J = 12.1 Hz, -H2C(1′)), 4.10–4.04 (m,
1H, -CH-O), 4.02–3.95 (m, 2H, -CH2-OTs), 3.00–2.87 (m,
2H, -CH2-OMTr), 2.38 (s, 3H, -CH3, (Ts)), 2.21 (s, 3H, 6-
CH3). Anal. calcd. for C36H36N2O8S: C 65.84, H 5.53, N
4.27, S 4.88; found: C 65.87, H 5.21, N 4.26, S 4.72.
1
(89.0 mg, 44%), mp 160–162 °C. H NMR (DMSO-d6) δ:
7.81 (s, 1H, 8-CH), 7.67 (d, 2H, J = 8.4 Hz, -CH, (m-Ts)),
7.49 (d, 2H, J = 8.4 Hz, -CH, (o-Ts)), 7.32–6.66 (m, 29H,
-NH, -CH(arom)), 5.08 (d, 1H, J = 11.7 Hz, -H2C(1′)), 4.85
(d, 1H, J = 11.7 Hz, -H2C(1′)), 3.75 (s, 3H, -OCH3), 3.72 (s,
3H, -NCH3), 3.54 (s, 3H, -OCH3), 3.50–3.46 (m, 1H -CH-O-),
2.55–2.52 (m, 2H, -CH2-OMTr), 2.43 (s, 3H, -CH3, (Ts)),
2.37–2.34 (m, 2H, -CH2-OTs). Anal. calcd. for
C57H53N5O8S: C 70.72, H 5.52, N 7.23, S 3.31; found: C
70.28, H 5.42, N 7.15, S 3.19.
N1-Methyl-N2-(p-anisyldiphenylmethyl)-9-[(4-(p-toluene-
sulfonyloxy))-3-p-anisyldiphenylmethoxy-methylbutyl]gua-
nine (32)
N2-(p-Anisyldiphenylmethyl)-9-[(4-(p-toluenesulfonyl-
oxy))-3-p-anisyldiphenylmethoxy-methyl-butyl]guanine (30,
300 mg, 0.315 mmol) and tetrabutylammonium hydroxide
solution (1 mol L–1, 0.33 mL, 0.33 mmol) were dissolved in
7.5 mL of dry DMF. A solution of methyl iodide (45 µL,
0.72 mmol) in 0.45 mL DMF was added under vigorous stir-
ring at room temperature. After 75 min, the solvent was
evaporated and the residue purified by MPLC (silica gel, di-
chloromethane–methanol (25:1, v/v)) to obtain 32 (134 mg,
6-Methyl-1-[[1-(p-anisyldiphenylmethoxy)-3-fluoro-2-
propoxy]methyl]uracil (23)
22 (180 mg, 0.274 mmol), Kryptofix® 2.2.2 (1.00 g,
2.66 mmol), potassium carbonate (125 mg, 0.904 mmol),
and potassium fluoride (1.00 g, 17.2 mmol) were suspended
in 20 mL of dry acetonitrile and heated for 15 min to
120 °C. The mixture was cooled down, the precipitated sub-
stances were filtered off, and the solvent was evaporated.
The residue was purified by column chromatography (RP-
18, acetonitrile–water (2:1, v/v)) to afford 23 (42.9 mg,
31%), mp 80 °C. 1H NMR (DMSO-d6) δ: 11.34 (s, 1H, -NH),
7.35–6.87 (m, 14H, -CH(arom)), 5.47 (d, 1H, J = 11.5 Hz,
-H2C(1′)), 5.32 (d, 1H, J = 11.5 Hz, -H2C(1′)), 4.56–4.41 (m,
2H, -CH2-F), 4.37–4.33 (m, 1H, -CH-O), 3.73 (s, 3H, -OCH3),
3.07–2.97 (m, 2H, -CH2-OMTr), 2.31 (s, 3H, 6-CH3). 19F
NMR (DMSO-d6) δ: –229.5. Anal. calcd. for C29H29N2O4F:
C 69.03, H 5.79, N 5.55; found: C 68.95, H 5.72, N 5.49.
1
44%), mp 117 °C. H NMR (DMSO-d6) δ: 7.73 (d, 2H, J =
8.0 Hz, -CH, (m-Ts)), 7.46 (d, 2H, J = 8.0 Hz, -CH, (o-Ts)),
7.38 (s, 1H, 8-CH), 7.31–6.70 (m, 29H, N2H, -CH(arom)),
3.73 (s, 3H, -OCH3), 3.86–3.68 (m, 2H, -CH2-OTs), 3.64 (s,
3H, N1CH3), 3.63 (s, 3H, -OCH3), 3.29 (mc, 2H, -H2C(1′)),
2.72–2.51 (m, 2H, -CH2-OMTr), 2.38 (s, 3H, -CH3), 1.48
(mc, 1H, -HC(3′)), 0.98–1.03 (m, 2H, -H2C(2′)). Anal. calcd.
for C58H55N5O7S: C 72.10, H 5.74, N 7.25, S 3.32; found: C
72.15, H 5.79, N 7.31, S 3.27.
N6-Methyl-9-[(2,2-dimethyl-1,3-dioxane-5-yl)ethyl]purine (28)
N1-Methyl-N2-(p-anisyldiphenylmethyl)-9-[[1-(p-anisyl-
diphenylmethyl)-3-fluoro-2-propoxy]methyl]guanine (33)
31 (200 mg, 0.207 mmol), potassium fluoride (182 mg,
3.13 mmol), potassium carbonate (125 mg, 0.904 mmol),
and Kryptofix® 2.2.2 (500 mg, 1.32 mmol) in 20 mL
acetonitrile were heated at 120 °C for 60 min. The mixture
was cooled down, the precipitated substances were filtered
off and the solvent was evaporated. The residue was purified
by column chromatography (RP-18, acetonitrile–water (6:1,
5-(2-Bromoethyl)-2,2-dimethyl-1,3-dioxane (27, 167 mg,
0.75 mmol) and potassium carbonate (138 mg, 1.00 mmol)
were added to N6-methyladenine (14, 113 mg, 0.75 mmol)
suspended in 2 mL of dry DMF, and the mixture was stirred
for 5 h at 20 °C. The mixture was then filtered to remove in-
soluble material. The combined filtrates were evaporated and
the residue purified by MPLC (RP-18, water–acetonitrile
1
(7:3, v/v)) yielding 28 (83 mg, 38%), mp 121–123 °C. H
1
NMR (DMSO-d6) δ: 8.23 (s, 1H, 2-CH), 8.15 (s, 1H, 8-CH),
7.69 (s, 1H, -NH), 4.15 (t, 2H, J = 7.2 Hz, -H2C(1′)), 3.76–
3.72 (m, 2H, -CH2-O-), 3.54–3.49 (m, 2H, -CH2-O-), 2.93
(s, 3H, NCH3), 1.77–1.73 (m, 2H, -H2C(2′)), 1.55–1.54 (m,
1H, -HC(3′)), 1.30 (s, 3H, -CH3), 1.23 (s, 3H, -CH3). Anal.
calcd. for C14H21N5O2: C 57.71, H 7.26, N 24.04; found: C
57.62, H 7.15, N 23.97.
v/v)) to afford 33 (37 mg, 22%), mp 121–123 °C. H NMR
(DMSO-d6) δ: 7.83 (s, 1H, 8-CH), 7.35–6.65 (m, 29H, -NH,
-CH(arom)), 5.07 (d, 1H, J = 10.5 Hz, -H2C(1′)), 4.95 (d,
1H, J = 10.5 Hz, -H2C(1′)), 4.60–3.80 (m, 2H, -CH2-F), 3.74
(s, 3H, -OCH3), 3.72 (s, 3H, -NCH3), 3.72–3.46 (m, 1H,
-CH-O-), 3.56 (s, 3H, -OCH3), 2.61–2.52 (m, 2H, -CH2-
OMTr). 19F NMR (DMSO-d6) δ: –229.5. Anal. calcd. for
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Can. J. Chem. Vol. 82, 2004
Table 5. Syntheses times, HPLC conditions, and radiochemical yields of the radio-labelled compounds.
Synthesis time
(after EOB) (min)
HPLC conditions
(water–ethanol)
Radiochemical
yield (d.c.) (%)
Rt (min)
Tracer
[18F]FHPG (2)
90
95
85
95
85
95:5
92:8
90:10
92:8
95:5
15
10
12
19
10
8.0
10.0
7.0
16.0
12.0
[18F]FHBG (4)
[18F]FMHPG (6)
[18F]FMHBG (8)
[18F]FMHPU (13)
Note: EOB is the end of bombardement; d.c. is decay corrected.
C50H46N5O5F: C 73.60, H 5.68, N 8.58; found: C 73.37, H
5.33, N 8.38.
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Acknowledgements
This study was supported by the Saxon Ministry of Sci-
ence and Art (Grant 47531.50–03–844–98/2). The excellent
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© 2004 NRC Canada