696
Y.-P. He et al. / Bioorg. Med. Chem. Lett. 21 (2011) 694–697
1b, 1c, 1e and 1f were also displayed higher anti-HIV-1 potency
(EC50 = 1.950, 0.162, 0.025, 0.088 and 0.217 nM, respectively) and
better selectivity index (SI = 116,974, 1,391,975, 3,624,000,
2,538,636 and 515,668, respectively) than those found for NVP
and AZT.
Among those compounds obtained, 1g/1c/1e/1b appear to be the
promising candidates for further anti-HIV-1 agent development.
Further modification and optimization of R1 and R2 groups on 6-
cyclohexylmethylpyrimidoneanalogs willlead to morepotent com-
pounds for active anti-HIV agents.
In the 2-oxoarylethylsulfanyl series, replacing the C-6 benzyl at
the pyrimidine ring by a cyclohexylmethyl caused a dramatic
selectivity index increase. As seen, C-6 cyclohexylmethyl substi-
tuted derivatives (1b, 1c, 1f, and 1g) were 49–410-folds (SI ratio)
more active than their benzyl substituted counterparts (6d, 6c,
6b, and 6a). This is in agreement with the results reported by Hop-
kins et al.9 These results provided further evidence that compared
with aromatic electronic interaction, the C-6 cyclohexylmethyl
group could provide better conformational flexibility and hydro-
phobic interaction with the binding pocket of the HIV-1 reverse
transcriptase which in turn enhanced the anti-HIV activity of the
2-oxoarylethyl-4-pyrimidinone derivatives.
The role of the C-5 substituent in the anti-HIV activity of the
compounds has also been studied. As with the other DABO series,
this S-DACOs unambiguously showed that the inhibitory activity
increased with the modification of the C-5 substituent in the order
of i-Pr > Et > Me, as indicated in the 2-benyl-sulfanyl (1e, 1h, and
1l) and 2-iso-butyl-sulfanyl substituted DACOs (1d, 1i, and 1m)
series. This C-5 hydrophobic contact increase effect has been indi-
cated by D’cruzl and Uckun5 in a computational modeling study.
Our results with this library, as well as the other DABO series,
clearly support it. The only exception occurred in 2-phenyl-
oxoethylsulfanyl DACOs (1c, 1g, and 1k). In this group, the influ-
ence of the ethyl substituent was slightly higher than its isopropyl
counterpart. For example, 1g (EC50 = 0.012 nM) was twofold more
potent than its 5-i-Pr counterpart 1c (EC50 = 0.025 nM). Additional
computational modeling and SAR study are needed to explain this
observation.
In terms of the role of alkyl group substitution at the C-2 side
chain, one thing we noticed was that the (CH3)2CHCH2– substitute
(Table 1) reduced the anti-HIV-1 activity of compounds 1d, 1i, and
1m. This result implied that certain aromaticity was required at
this position in order to get a good affinity for this drug to bind
to the binding pocket. In our previous report, we have indicated
the importance of the C2-b-carbonyl to the anti-HIV-1 catalytic
activity.22,23 However, this is not true in this novel S-DACOs library.
As indicated in Table 1, compound 1e still had a high activity
(EC50 = 0.088 nM) after the b-carbonyl of compound 1c was re-
moved. This information will provide us better guidance in future
structural designs on the S-DACOs development.
We have also chosen active compound 1c to evaluate its
anti-HIV-1 activity in human peripheral blood mononuclear cells
(PBMCs) and the NNRT inhibitor resistant strain A17, which contains
two mutations (Y181C and K103N).24 Results are presented in Table
2. Interestingly, it was found that 1c showed a favorable anti-HIV-1
activity in both human PBMCs and A17 with the EC50 0.031 and
Acknowledgments
This research was supported by the National Natural Science
Foundation of China (Grant No. 30560179 and 30960459), the Sci-
ence Foundation of Chinese academy science (Grant No.
W8090303) and the Science Foundation of Yunnan province (Grant
Nos. 2009BC018 and 2010CI019) and to Dr. Y. P. He, the knowledge
Innovation Program of Chinese Academy of Sciences (KSCX1-YW-
R-24), 973 Program (2006CB504200), Key Scientific and Techno-
logical projects of Yunnan (2004NG12) to Dr. Y. T. Zheng. We
would like to acknowledge MRC AIDS Research Project (UK) for
providing cell lines and virus.
References and notes
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Nakashima, H.; Perno, C. F.; Walker, R. T.; Miyasaka, T. Biochem. Biophys. Res.
Commun. 1989, 165, 1375.
4. Miyasaka, T.; Tanaka, T.; Baba, M.; Hayakawa, H.; Walker, R. T.; Balzarini, J.; De
Clercq, E. J. Med. Chem. 1989, 32, 2507.
5. D’cruz1, O. J.; Uckun, F. M. J. Enzyme Inhib. Med. Chem. 2006, 21, 329.
6. Artico, M. Drugs Future 2002, 27, 159.
7. Marongiu, M. E.; Pani, A.; Musiu, C.; La Colla, P.; Mai, A.; Sbardella, G.; Massa, S.;
Artico, M. Recent Res. Dev. Med. Chem. 2001, 1, 65.
8. Tanaka, H.; Tajashia, H.; Ubasawa, M.; Sekiya, K.; Inouye, N.; Baba, M.; Shigeta,
S.; Wallker, R. T.; De Clercq, E.; Miyasaka, T. J Med. Chem. 1995, 38, 2860.
9. Hopkins, A. L.; Ren, J.; Tanaka, H.; Baba, M.; Okamato, M.; Stuart, D. I.;
Stammers, D. K. J. Med. Chem. 1999, 42, 4500.
10. Vig, R.; Mao, C.; Venkatachalam, T. K.; Tuel-Ahlgren, L.; Uckun, F. M. Bioorg.
Med. Chem. Lett. 1998, 8, 1461.
11. He, Y. P.; Chen, F. R.; Yu, X. J.; Wang, Y. P.; De Clercq, E.; Balzarini, J.;
Pannecouque, C. Bioorg. Chem. 2004, 32, 536.
12. Hopkins, A. L.; Ren, J.; Esnouf, R. M.; Willcox, B. E.; Jones, E. Y.; Ross, C.;
Miyasaka, T.; Walker, R. T.; Tanaka, H.; Stammers, D. K.; Stuart, D. I. J. Med.
Chem. 1996, 39, 1589.
13. Mao, C.; Sudeck, E. A.; Venkatachalam, T. K.; Uckun, F. M. Biochem. Pharmacol.
2000, 6, 1251.
14. Robert, C. R.; Wang, D. P.; Julian, T. R.; William, L. J. J. Am. Chem. Soc. 2000, 122,
12898.
15. Nawrozkij, M. B.; Rotili, D.; Tarantino, D.; Botta, G.; Eremiychuk, A. S.;
Musmuca, I.; Ragno, R.; Samuele, A.; Zanoli, S.; Armand, U. M.; Clotet-Codina, I.;
Novakov, I. A.; Orlinson, B. S.; Maga, G.; Est, J. A.; Artico, M. J. Med. Chem. 2008,
51, 4641.
16. Mai, A.; Artico, M.; Sbardella, G.; Massa, S.; Novellino, E.; Greco, G.; Loi, A. G.;
Tremontano, E.; Marongiu, M. E.; Colla, P. L. J. Med. Chem. 1999, 42, 619.
17. Clay, R. J.; Collom, T. A.; Karrick, G. L.; Wemple, J. A. Synthesis 1993, 290.
18. Blaise, E. E.; Hebd, C. R. Seances Acad. Sci. 1901, 132, 478.
19. Hannick, S. M.; Kishi, Y. J. Org. Chem. 1983, 48, 3833.
20. General procedure for the preparation of compounds 1a–m: Sodium metal (8 g,
0.348 mol) was dissolved in 180 mL of absolute ethanol, and thiourea (19.2 g,
0.252 mol) and b-ketoesters 4a–c (0.084 mol), were added to the clear
solution. The reaction mixture was refluxed for 6–8 h. After cooling, the
solvent was removed under reduced pressure, and the residue was dissolved in
H2O (100 mL) and acidified with 13% HCl. The resulting precipitate was filtered,
washed sequentially with H2O, EtOH, and Et2O, then dried to give 5a–c as a
pure solid. To a solution of 2-thiouracil 5a–c (2 mmol) in anhydrous DMF
(8 mL) were added K2CO3 (2.2 mmol) and halide (R2X) (2.2 mmol). The mixture
was stirred at room temperature for 8–24 h. After TLC (EtOAc/PE) revealed the
disappearance of the starting material, the reaction mixture was filtered. The
suspension was then diluted with cold water and extracted with ethyl acetate.
The combined organic extract was washed with brine, dried with Na2SO4, and
evaporated to furnish crude product, which was purified by flash
chromatography or by crystallization to give the pure target compounds 1a–
m. As an example, spectroscopic data for compound 1b are reported. 1H NMR
0.046 lM, respectively. Further anti-activity evaluation of these
new DACOs is currently undergoing and will be reported upon
completion.
In summary, substitution of a cyclohexylmethyl group to
aromatic group at the C-6 position of the thymine ring and modifica-
tion its C-2 and C-5 positions have led to a series of novel dihydro-
aryl/alkylsulfanyl-cyclohexylmethyl-oxopyrimidines (S-DACOs).
Table 2
(DMSO-d6):
d (ppm) 0.77–0.78 (m, 2H, cyclohexyl), 1.17–1.19 (m, 2H,
Anti-HIV activity of selected title compounds 1C in PBMC and A17
cyclohexyl), 1.26–1.30 (m, 1H, cyclohexyl), 1.29–1.30 (d, 6H, J = 6.9 Hz,
2CH3), 1.58–1.71 (m, 6H, cyclohexyl), 2.26–2.28 (d, 2H, J = 6.6 Hz, CH2–
cyclohexyl), 2.89–2.95 (m, 1H, CHMe2), 3.88 (s, 3H, OCH3), 4.53 (s, 2H, CH2S),
6.97–8.04 (d, 4H, phenyl), 12.6 (s, br s, 1H, NH); 13C NMR (DMSO-d6): d (ppm)
20.23 (2CH3), 26.63 (2CH2, cyclohexyl), 26.74 (CH), 28.12 (2CH2, cyclohexyl),
37.4 (CH2), 37.89 (CH2S), 42.50 (CH2, cyclohexyl), 55.8 (OCH3), 114.29–132.5
Compd
EC50 values (lM)
PBMC
0.031
A17 (Y181C and K103N)
0.046
1c