5292
M. Hocek et al. / Bioorg. Med. Chem. Lett. 16 (2006) 5290–5293
ˇ´ ´
8. Hocek, M.; Holy´, A.; Votruba, I.; Dvorakova, H. Collect.
Czech. Chem. Commun. 2000, 65, 1683.
9. Ding, Y.; Girardet, J.-L.; Hong, Z.; Lai, V. C. H.; An, H.;
Koh, Y.-h.; Shaw, S. Z.; Zhong, W. Bioorg. Med. Chem.
Lett. 2005, 15, 709.
indicating that the antiviral structure–activity relation-
ships for 6-modified purine L-ribonucleosides are quite
narrow.
To verify the antiviral mode of action, the triphos-
phate of 2h was prepared20 and the in vitro inhibi-
tion of HCV NS5B polymerase evaluated.21
Inhibition was determined using recombinant NS5B
derived from HCV con1 strain (1b), with a C-termi-
nal hexahistidine tag and the last 21 amino acids
deleted, and a heteropolymeric RNA template.22 No
inhibition of the NS5B polymerase activity was
observed up to 100 lM concentration of inhibitor
(Table 2). In addition, the ability of 2h triphosphate
to serve as a NS5B polymerase substrate in a single-
nucleotide incorporation assay was determined.23 The
incorporation assay was performed using recombinant
NS5B from HCV con1 strain (1b), with a C-terminal
hexahistidine tag and the last 55 amino acids deleted,
a dinucleotide primer (GpC), and a RNA oligonu-
cleotide template (50-CAAAAAAAUGC-30).24 No
incorporation of 2h triphosphate by NS5B was
observed up to concentrations of 1 mM. Further-
more, the triphosphate of L-adenosine was also not
incorporated by NS5B polymerase under the same
conditions. Taken together, these results suggest that
purine L-ribonucleosides are not substrates of the vir-
al polymerase and that the antiviral activity of 2h
was not due to incorporation by NS5B polymerase
into the viral RNA and subsequent termination of
further synthesis, but most likely inhibition of other
cellular or viral targets.
10. Fernandez, F.; Garcia-Mera, X.; Morales, M.; Rodriguez-
Borges, J.; De Clercq, E. Synthesis 2002, 1084.
ˇ
ˇ
11. (a) Smejkal, J.; Sorm, F. Collect. Czech. Chem. Commun.
1964, 29, 2809; (b) Acton, E. M.; Ryan, K. J.; Goodman,
ˇ
L. J. Am. Chem. Soc. 1964, 86, 5352; (c) Holy´, A.; Sorm,
F. Collect. Czech. Chem. Commun. 1969, 34, 3383; (d)
Holy´, A. Collect. Czech. Chem. Commun. 1972, 37, 4072.
12. Reviews: (a) Wang, P. Y.; Hong, J. H.; Cooperwood, J. S.;
Chu, C. K. Antiviral Res. 1998, 40, 19; (b) Gumina, G.;
Song, G.-Y.; Chu, C. K. FEMS Microbiol. Lett. 2001, 202,
9; (c) Gumina, G.; Chong, Y.; Choo, H.; Song, G.-Y.;
Chu, C. K. Curr. Top. Med. Chem. 2002, 2, 1065.
13. Bryant, M. L.; Bridges, E. G.; Placidi, L.; Faraj, A.; Loi,
A. G.; Pierra, C.; Dukhan, D.; Gosselin, G.; Imbach, J. L.;
Hernandez, B.; Juodawlkis, A.; Tennant, B.; Korba, B.;
Cote, P.; Marion, P.; Cretton-Scott, E.; Schinazi, R. F.;
Sommadossi, J. P. Antimicrob. Agents Chemother. 2001,
45, 229.
14. Recent examples: (a) Mugnaini, C.; Botta, M.; Coletta,
M.; Corelli, F.; Focher, F.; Marini, S.; Renzulli, M. L.;
Verri, A. Bioorg. Med. Chem. 2003, 11, 357; (b) Zhu, W.;
Chong, Y. H.; Choo, H.; Mathews, J.; Schinazi, R. F.;
Chu, C. K. J. Med. Chem. 2004, 47, 1631; (c) Seela, F.;
Lin, W.; Kazimierczuk, Z.; Rosemeyer, H.; Glacon, V.;
Peng, X.; He, Y.; Ming, X.; Andrzejewska, M.; Gorska,
A.; Zhang, X.; La Colla, P. Nucleosides Nucleotides
Nucleic Acids 2005, 24, 859; (d) Clinch, K.; Evans, G.
B.; Fleet, G. W. J.; Furneaux, R. H.; Johnson, S. W.;
Lenz, D. H.; Mee, S. P. H.; Rands, P. R.; Schramm, V. L.;
Taylor Ringia, E. A.; Tyler, P. C. Org. Biomol. Chem.
2006, 4, 1131; (e) Seela, F.; Peng, Q. Collect. Czech. Chem.
Commun. 2006, 71, 956.
15. Reviews: (a) Hocek, M. Eur. J. Org. Chem. 2003, 245; (b)
Agrofoglio, L. A.; Gillaizeau, I.; Saito, Y. Chem. Rev.
2003, 103, 1875.
Acknowledgments
This work is a part of the research project Z4 055 0506.
It was supported by the ‘Centre for New Antivirals and
Antineoplastics’ (1M0508), by the Programme of
Targeted Projects of Academy of Sciences of the Czech
Republic (1QS400550501), and by Gilead Sciences, Inc.
(Foster City, CA, USA).
16. Compound 3: a mixture of chloropurine (3.8 g, 20 mmol)
and 1,2,3,5-tetra-O-acetyl-b-L-ribose (6.4 g, 20 mmol) in
acetonitrile (100 ml) was stirred at rt and SnCl4 (5 ml) was
added dropwise. The stirring was continued for 10 h and
the solvent was evaporated. The residue was dissolved in
ethyl acetate (250 ml) and washed with satd aq NaHCO3
(2· 250 ml) and H2O (2· 250 ml). The organic phase was
dried, evaporated, and the residue chromatographed on
silica gel (ethyl acetate) to give 3 as yellowish foam (5 g,
61%), [a]D +15.9 (c 0.35, CHCl3). Spectral data were in
accord with those of D-enantiomer: Buck, I.M.; Reese,
C.B. J. Chem. Soc., Perkin Trans. 1 1990, 2937–2942.
17. (a) Hirota, K.; Kitade, Y.; Kanbe, Y.; Maki, Y. J. Org.
References and notes
1. Montgomery, J. A.; Hewson, K. J. Med. Chem. 1968, 11,
48.
ˇ
ˇ
Chem. 1992, 57, 5268; (b) Cesnek, M.; Hocek, M.; Holy´,
A. Collect. Czech. Chem. Commun. 2000, 65, 1357; (c)
´
2. (a) Silhar, P.; Pohl, R.; Votruba, I.; Hocek, M. Org. Lett.
2004, 6, 3225; (b) Silhar, P.; Pohl, R.; Votruba, I.; Hocek,
ˇ
´
ˇ
Silhar, P.; Pohl, R.; Votruba, I.; Klepetarova, B.; Hocek,
´
M. Collect. Czech. Chem. Commun. 2006, 71, 788.
´ˇ
´
M. Collect. Czech. Chem. Commun. 2005, 70, 1669.
ˇ
3. Silhar, P.; Pohl, R.; Votruba, I.; Hocek, M. Org. Biomol.
´
Chem. 2005, 3, 3001.
18. Spectral data of compounds 2 and 4 were in accord with
those of the corresponding D-ribonucleosides. Compari-
son of mp and [a]D values of L-nucleosides 2 with those of
D-nucleosides 1: 2a: mp 229–231 ꢁC, [a]D +60.4 (c 0.34,
DMF) [lit.6a for 1a: mp 228–230 ꢁC, [a]D ꢀ56.1 (c 0.5,
DMF)]. Compound 2b: mp 172–176 ꢁC, [a]D +55.9 (c 0.15,
DMF) [lit.6a for 1b: mp 173–175 ꢁC, [a]D ꢀ61.5 (c 0.5,
DMF)]. Compound 2c: mp 198–200 ꢁC, [a]D +60.8 (c 0.39,
DMF) [lit.7 for 1c: mp 196–199 ꢁC, [a]D ꢀ51.8 (c 0.5,
DMF)]. Compound 2d: mp 225–229 ꢁC, [a]D +68.2 (c 0.33,
DMF) [lit.6b for 1d. H2O: mp 126–129 ꢁC, [a]D ꢀ55.3 (c
0.2, DMF)]. Compound 2e: mp 179–181 ꢁC, [a]D +62.5 (c
ˇ
4. Silhar, P.; Pohl, R.; Votruba, I.; Hocek, M. Synthesis
´
2006, 1848.
´
ˇ´ ´
5. Hockova, D.; Hocek, M.; Dvorakova, H.; Votruba, I.
Tetrahedron 1999, 55, 11109.
6. (a) Hocek, M.; Holy´, A.; Votruba, I.; Dvorakova, H. J.
ˇ´
Med. Chem. 2000, 43, 1817; (b) Hocek, M.; Holy´, A.;
´
ˇ´
Votruba, I.; Dvorakova, H. Collect. Czech. Chem. Com-
mun. 2001, 66, 483.
´
ˇ
7. Hocek, M.; Naus, P.; Pohl, R.; Votruba, I.; Furman, P.
A.; Tharnish, P. M.; Otto, M. J. . J. Med. Chem. 2005, 48,
5869.