Sulfur containing acyclovir derivatives: Synthesis, cytotoxic activity, and cell phenotype studies

Article abstract of DOI:10.1080/15257770701528354

New 2-amino-6-oxo-8-thioxo-9-substituted purine derivatives were prepared and assayed for the in vitro cytotoxic activity. Some products exhibited moderate activity on HT-1080 cells and rather high activity on MG-22A cells. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15257770701528354

Nucleosides, Nucleotides, and Nucleic Acids, 26:1269–1271, 2007
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1525-7770 print / 1532-2335 online
DOI: 10.1080/15257770701528354
SULFUR CONTAINING ACYCLOVIR DERIVATIVES: SYNTHESIS,
CYTOTOXIC ACTIVITY, AND CELL PHENOTYPE STUDIES
Martins Ikaunieks, Irina Shestakova, Ilona Domracheva, Sergey Belyakov,
and Marina Madre
Latvian Institute of Organic Synthesis, Riga, Latvia
2
New 2-amino-6-oxo-8-thioxo-9-substituted purine derivatives were prepared and assayed for the
2
in vitro cytotoxic activity. Some products exhibited moderate activity on HT-1080 cells and rather
high activity on MG-22A cells.
Keywords Sulfur; acyclovir; antiherpetic drugs
INTRODUCTION
Acyclovir is a well-known highly potent and selective antiherpetic drug.
At the same time, it has been found to have the growth inhibitory ac-
tivity against murine leukemia L 1210,[1a] but some of its 8-substituted
or/and 1,N-2-bridged (tricyclic) analogues have demonstrated moderate
activity and remarkable cytotoxic selectivity against KB and HeLa tumour
cells.[1b] This article describes the synthesis and the in vitro cytotoxic activity
of a series of new 2-amino-6-oxo-8-thioxo-9-(2-hydroxyethoxymethyl)purine
derivatives as well as several 2-amino-6-oxo-8-thioxopurines bearing an alter-
native substituent at position 9 of the heterocycle.
RESULTS AND DISCUSSION
The synthesized derivatives of 2-amino-6-oxo-8-thioxopurine are listed
in Figure 1. Products 2a–c were prepared and described previously.[2a] Com-
pounds 1a–d were obtained by N, O- or N-deacetylation of the correspond-
ing 2-acetamido-9-(2-acetoxyethoxymethyl)-6-oxo-8-thioxopurines.[2a] The
interaction of 8-(2-hydroxyethyl)thiopurine 1b with adipic anhydride led to
the formation of dicarboxylic acid 1f. The N,N-dimethylaminomethylene
protecting group removal in 8-(ethoxycarbonylmethyl)thiopurine
Address correspondence to M. Ikaunieks, Latvian Institute of Organic Synthesis, Riga, Latvia.
E-mail: ikaunieks@osi.lv
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M. Ikaunieks et al.
FIGURE 1 Structural formulas of 2-amino-6-oxo-8-thioxopurine derivatives.
derivative[2b] with hydrazine hydrate brought about simultaneous ami-
dation of the ester fragment yielding product 1g. For the incorporation
of a phenylthio substituent at position 8 of the purine cycle (1e) the
reaction of 2-acetamido-9-(2-acetoxyethoxymethyl)-8-bromo-6-oxopurine
with PhSH/NaOAc/EtOH system was used. Simultaneous splitting of the
N-acetyl protecting group occurred during this reaction yielding 1e in one
step. Scheme 1 presents the synthesis of products 1i, h via intermediate
4 prepared by alkylation of purine 3 (R = Br) with isopropoxymethyl
chloride. The formation of the 9- and 7-alkoxyalkylated products in equal
ratio and in good overall yield (88%) was observed in this reaction.
The transformation of 4 into compound 1i was carried out via routine
thionation and deprotection.[2c] To obtain product 1h intermediate 4
was treated with 3-methoxyphenyl thiol similar to the synthesis of 1e.
7,9- Dibenzyl-8-thioxopurine 2d was obtained by alkylation of 3 (R =
SCH3) with benzyl bromide and isolated alongside with the corresponding
7-benzyl- and 9-benzyl-8-methylthiopurine. The structures of compounds 1,
1
2 were supported by H NMR spectra and elemental analysis data as well
as by single crystal X-ray analysis for product 2d.[3] The cytotoxic activity of
SCHEME 1 Reagents: (a) ClCH2OCH(CH3)2, Et3N, THF; (b) Na2S2O3, AlCl3, H2O; (c) MeNH2, H2O
(d) ArSH, NaOAc, MeOH, H2O; (e) BnBr, K2CO3, DMF.

Sulfur Containing Acyclovir Derivatives
1271
TABLE 1 In vitro cytotoxicity of 8-thioxopurine derivatives 1, 2 on monolayer tumor
cell lines HT-1080, MG-22A, and on normal mouse fibroblasts cells (NIH 3T3)
HT-1080
MG-22A
NO, 100%
NIH 3T3
LD50 mg/kg
a
Cmpd.
TD50
NO, 100%
TD50
TD50
1d
1e
1i
2a
2d
0.024
0.099
0.019
0.200
0.048
367
75
650
28
0.003
NAb
NA
NA
0.018
275
9
20
17
300
0.127
2.664
0.278
2.503
0.036
1000
2403
872
2517
360
233
aTD50-Concentration (mole/l × 103) providing 50% cell killing effect [(CV+
MTT)/2]; NO Concentration (%).
b NA-inactive.
products 1, 2 as well as their influence on cell morphology were tested in
vitro on monolayer tumour cell lines HT-1080 (human fibrosarcoma), MG-
22A (mouse hepatoma) and on normal mouse fibroblasts cells (NIH 3T3).
The results obtained are summarized in Table 1. Compound 1a–c, f; 2b, c
were inactive in both test systems (data not shown). However, the inspection
of the cell morphology demonstrated that one of these compounds, namely
1h dramatically increased the speed of fibrosarcoma cell growth. Products
1d,e,i and 2a,d exhibited moderate cytotoxic effect on HT-1080 cell line but
derivatives 1d, 2d had rather high activity also on MG-22A cells. All cytotoxic
products showed low acute toxicity except for 2d that had similar values on
the three cell lines.
REFERENCES
1. a) Nishimaki, J.; Miyazawa, K.; Gotoh, A.; Yoshikawa, O.; Ohyashiki, K.; Toyama, K. Inhibitory effect
of a nucleoside analog, acyclovir, on leukemia cells. Leukemia Res. 1996, 20, 415–420; b) Hladon, B.;
Goslinski, T.; Laskowska, H.; Baranowski, D.; Ostrowski, T.; Zeidler, J.; Ruskowski, P.; Golankiewicz,
B. In vitro cytostatic activity of 8-substituted and tricycylic analogues of acyclovir. Pol. J. Pharmacol.
2002, 54, 45–53.
2. a) Ikaunieks, M.; Madre, M. Purine nucleoside analogues. 12. Synthesis of new 8,9-disubstituted
guanine derivatives by S-alkylation of 8-thio-9-(2-acetoxyethoxymethyl)-N2-acetylguanine. Chem. Het-
erocycl. Comp. (Engl. Ed.) 2003, 2, 274–280; b) Ikaunieks, M.; Madre, M. Efficient synthesis of 8-
thiosubstituted guanine derivatives as potential tools for biochemical and biological studies. Nucleo-
sides, Nucleotides Nucleic Acids 2003, 22, 755–758; c) Ikaunieks, M.; Madre, M. Reinvestigation of the
reaction of 8-bromoguanine derivatives with sodium thiosulfate. J. Chem. Res. (S) 2002, 226–227.
3. Selected data for the synthesized compounds. 1e: m.p. 215–217◦C. 1H-NMR (if not stated otherwise,
200 MHz, DMSO-d6, δ): 1.91 (s, 2H, CH3); 6.64 (s, 2H, NH2); 7.26–7.38 (m, 5H, ArH), 1h: m.p.
>250◦C, 1H-NMR: 1.07 (d, 6H, 2 × CH3, J = 6.8 Hz); 3.99 (septet, 1H, CH, J = 6.8 Hz); 5.36 (s, 2H,
CH2); 6.70 (s, 2H, NH2); 10.93 (bs, 1H, NH); 12.85 (bs, 1H, NH), 1i: m.p. 218–220◦C. 1H-NMR:
3.71 (s, 3H, CH3); 6.67 (s, 2H, NH2); 6.80–6.90 (m, 3H, ArH); 7.22–7.29 (m, 1H, ArH), 2d: m.p.
259–260◦C, 1H-NMR: 5.28 (s, 2H, CH2); 5.50 (s, 2H, CH2), 6.76 (s, 2H, NH2); 7.20–7.42 (m, 10H,
Ar-H); 10.82 (bs, 1H, NH). X-ray crystal structure CCDC deposition number 289468.