Synthesis and anti-HSV activity of new N1-acyclic C4 and C 6-disubstituted pyrazolo[3,4-d]pyrimidine nucleosides

Article abstract of DOI:10.1080/15257770701521102

Several N1-(2-hydroxyethoxy)methyl, (4-hydroxybutyl) and (2,3-dihydroxy-1-propoxy)methyl-C4,C6-disubstituted-1H-pyrozolo[3,4-d] pyrimidines were synthesized. Some of them were evaluated against herpes simplex virus 1 and 2 replications in E6SM cells. Copy

Full text of DOI:10.1080/15257770701521102

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Synthesis and Anti-HSV Activity of new
N1-Acyclic C4 and C6-Disubstituted
Pyrazolo[3,4-D]Pyrimidine Nucleosides
Omar Moukha-chafiq a , Mohamed Labd Taha a & Abdelmalek Mouna a
a Laboratoire de Chimie Bio-Organique Appliquée, Facultes des
Sciences , Agadir, Maroc
Published online: 10 Dec 2007.
To cite this article: Omar Moukha-chafiq , Mohamed Labd Taha & Abdelmalek Mouna (2007)
Synthesis and Anti-HSV Activity of new N1-Acyclic C4 and C6-Disubstituted Pyrazolo[3,4-
D]Pyrimidine Nucleosides, Nucleosides, Nucleotides and Nucleic Acids, 26:8-9, 1107-1110, DOI:
10.1080/15257770701521102
To link to this article: http://dx.doi.org/10.1080/15257770701521102
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Nucleosides, Nucleotides, and Nucleic Acids, 26:1107–1110, 2007
Copyright ꢀ Taylor & Francis Group, LLC
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ISSN: 1525-7770 print / 1532-2335 online
DOI: 10.1080/15257770701521102
SYNTHESIS AND ANTI-HSV ACTIVITY OF NEW N1-ACYCLIC C4
AND C6-DISUBSTITUTED PYRAZOLO[3,4-D]PYRIMIDINE
NUCLEOSIDES
Omar Moukha-chafiq, Mohamed Labd Taha, and Abdelmalek Mouna
2
Laboratoire de Chimie Bio-Organique Applique´e, Facultes des Sciences, Agadir, Maroc
Several N1 -(2-hydroxyethoxy)methyl, (4-hydroxybutyl) and (2,3-dihydroxy-1-propoxy)methyl-
2
C4 ,C6 -disubstituted-1H-pyrozolo[3,4-d]pyrimidines were synthesized. Some of them were evaluated
against herpes simplex virus 1 and 2 replications in E6 SM cells.
Keywords Pyrazolo[3,4-d]pyrimidines; acyclonucleoside analogues
Recently, there have been considerable advances in the chemotherapy of
virus infections. Nevertheless, with the increase in the use of antiviral
drugs, a development of resistance to antivirals has been observed. In the
chemotherapy of herpes simplex virus infections, acyclovir is used clinically
as an anti-herpes drug. However, herpes viruses may sometimes acquire re-
sistance to acyclovir in immunocompromised patients.[1] Many research ap-
proaches currently are aimed at developing new types of antiviral agents that
have a wide range of efficacy without serious adverse effects and are potent
against viral strains resistant to current antiviral agents. The search for more
effective antiviral agents has so far developed only a few compounds that
have reached prominence at clinical level.
Acyclic nucleosides are of interest because of the antiviral activity of a
large number of this class of compounds.[2] Up to now, there have been
only a few reports regarding the synthesis of pyrazolo[3,4-d]pyrimidine acy-
clonucleosides. As an extension of our studies on mono di and trisubstituted
pyrazolo[3,4-d]pyrimidine derivatives[3] in which some of them showed an
interesting antiviral, antitumor and/or antituberculosis activity, we describe
This investigation was supported by Ibn Zoher University, Faculty of Sciences, Agadir Morocco.
We thank Dr. E. De Clercq (Katholieke Universiteit Leuven, Leuven, Belgium) for the antiviral assays.
J. J. Vasseur (Lab. de Chimie Organique Biomoleculaire de Synthese, U.S.T. Montpellier II, France) is
gratefully acknowledged for help with some spectral and elemental analysis.
Address correspondence to Omar Moukha-chafiq, Drug Discovery Division, Southern Research
Institute, 2000 Ninth Avenue South, Birmingham, AL 35205. E-mail: moukhachafiq@sri.org
1107

1108
O. Moukha-chafiq et al.
SCHEME 1
herein the synthesis of the anti-herpes acyclovir, HBG and iso-DHPG 4,6-
disubstituted pyrazolo[3,4-d]pyrimidinic analogues. We also have studied
the effects of some of these acyconucleosides on herpes simplex virus type 1
and 2 replications in E6SM cells.
The approach to the synthesis of acyclonucleosides 12–17 involves cou-
pling pyrazolo[3,4- d]pyrimidines 1 and 2 with acyclic chain moieties 3–5
(Scheme 1).
The coupling pseudo-sugars 3, 4, and 5 can be synthesized from
1,3-dixolane, tetrahydrofuran and glycerol, respectively, as previously
describe.[4−6] The bases used for the direct coupling 4,6-dimethyl
pyrazolo[3,4-d]pyrimidine 1 and 4,6-dibenzyl pyrazolo[3,4-d]pyrimidine 2
were synthesized in 6 steps from commercially available malononitrile and
triethyl orthoformate following a synthetic pathway previously described by
Robins et al.[7] Nucleophilic displacement of the bromine group of the 3–5
with 1–2 in the presence of potassium carbonate in DMF gave regioselec-
tively, 6–11 and small trace of their N2-isomers which easily could be sepa-
rated by silica gel column chromatography. The two regioisomers could be
easily distinguished by their UV spectra. Treatment of the desired isomers
6–11 with methalonic ammonia at room temperature afforded the target
compounds 12–17.
Compounds 12–14 served as precursors for the synthesis of acyclonu-
cleosides 18–32 (Scheme 2). When compounds 12–14 were treated with
methanolic ammonia in a sealed reacting vessel at 100◦C, the 4-amino
derivatives 18–20 were obtained in 86%, 88% and 80% yield, respectively.
Condensation of 12–14 with methyl amine in aqueous solution or benzyl

Synthesis and Anti-HSV Activity
1109
SCHEME 2
amine in ethanol at reflux afforded 21–26 in good yields. Products 27–29
were synthesized in 83%, 87%, and 82% yield, respectively, via treatment of
12–14 with NaOCH3/CH3OH solution at room temperature. Reaction of
12–14 with sodium hydroxide solution (2N) at room temperature during
4–6 hours gave compounds 30–32 in 70%, 72%, and 78% yield respectively.
1
All structures of the synthetic products were identified by H NMR, mass
spectra, UV and/or elemental analysis as for example compound 12.[8]
ANTI-HSV ACTIVITY
The antiviral activity effect of some of the target acyclonucleosides on
herpes simplex virus type 1 (HSV-1) (KOS) and (HSV-2) (G) replications
was determined (Table 1).
TABLE 1 Cytotoxicity and antiviral activity in E6SM cells
Minimum inhibitory concentrationb (µg/ml)
Compound
MCCa (µg/ml)
HSV-1 (KOS)
HSV-2 (G)
>80
12
14
15
16
17
18
19
21
22
24
27
28
400
400
80
400
16
>80
>80
>16
240
>3.2
>80
>400
>400
240
>80
240
>400
400
>80
>16
240
>3.2
>80
240
240
240
>80
240
400
400
80
>400
>400
400
>400
400
>400
>400
>100
Ribavirine
ACV
0.0064
0.0192
aInhibitory concentration required to reduce virus plaque formation by 50%. Virus input was 100
plaque forming units (PFU).
b Minimum cytotoxic concentration required to cause a microscopically detectable alteration of nor-
mal cell morphology.

1110
O. Moukha-chafiq et al.
Data for ribavirine, and ACV are shown for comparison. Our results
show that none of the tested compounds showed any significant activity
except for compounds 16, 19, 21, 22, 27, and 28, which are slightly active
against HSV-1 and/or HSV-2 (Table 1).
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herpetic drugs. Nucleosides and Nucleotides 1996, 15, 821–831.
3. Moukha-chafiq, O.; Taha, M.L.; Lazrek, H.B.; Vasseur, De Clercq, E. Synthesis and antiviral activity
of some C2, C4 and C6-substitued pyrazolo[3,4-d]pyrimidine acyclonucleosides with the alkylating
chains of ACV, HBG and iso-DHPG. Nucleosides Nucleotides Nucleic Acids 2006, 25(8), 849–860.
4. Robins, M.J.; HaMpield, P.W. Nucleic acid related compounds .37. Convenient and high-yield syn-
thesis of N-[2-(hydroxyethoxy)methyl] heterocycles as “acyclic nucleoside” analogues. Can. J. Chem.
1982, 60, 547–553.
5. Taha, M.L.; Lazrek, H.B. Synthesis of some 4-substituted 1-[(4-hydroxybutyl)-1H-pyrazolo-[3,4-
d]pyrimidines analogues of 9-(-[(4-hydroxybutyl)guanine (HBG). Bull. Soc. Chim. Belg. 1995, 104(11),
647–652.
6. Taha, M.L.; Lazrek, H.B. Synthesis of 4-substituted 1-[(2,3-dihydroxy-1-propoxy)methyl]-1H-
pyrazolo[3,4-d]pyrimidines. Bull. Soc. Chim. Belg. 1997, 106(3), 163–168.
7. Robins, R.K. Potential purine antagonists. I. Synthesis of some 4,6-substituted pyrazolo[3,4-
d]pyrimidines. J. Am. Chem. Soc. 1956, 78, 784–790.
8. 1-(2-hydroxyethxy)meythl-4,6-dimethylthio-1H-pyrazolo[3,4-d]pyrimidine 12. Rf: 0.52 (CHCl3:
CH3OH, 90:10). M.p.: 71–72◦C (ethanol). UV (ethanol) λmax: 249 nm (ε: 7 800). 1H-NMR (Me2SO-
d6) δ: 2.53 (s, 3H, 6-SCH3), 2.65 (s, 3H, 4-SCH3), 3.34–3.51 (m, 4H, OCH2CH2O), 4.61 (t, J: 5.39
Hz, 1H, HO, D2O exchangeable), 5.66 (s, 2H, OCH2N), 8.26 (s, 1H, H3). MS (FAB+, GT) m/z: 287
[M+H]+. Elem. Anal. Calcd. for C10H14N4O2S2 (286.38): C 41.94%, H 4.93%, N 19.56%, Found:
C 42.26%, H 5.14%, N 19.82%.