Synthesis and biological activity of novel 5′-arylamino-nucleosides by microwave-assisted one-pot tandem Staudinger/aza-Wittig/reduction

Article abstract of DOI:10.1016/j.bmcl.2010.10.054

Novel pseudonucleosides with benzylamino group on 5′-position (4) were synthesized by using the microwave-assisted one-pot tandem Staudinger/aza-Wittig/reduction reaction in good yields of 55.2-71.7%. The deacetylation of 4 afforded compounds 5. HIV-1 rev

Full text of DOI:10.1016/j.bmcl.2010.10.054

Bioorganic & Medicinal Chemistry Letters 21 (2011) 574–576
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and biological activity of novel 50-arylamino-nucleosides
by microwave-assisted one-pot tandem Staudinger/aza-Wittig/reduction
Hua Chen a, Jianpeng Zhao a, Yanan Li a, Fengjuan Shen a, Xiaoliu Li a,b, , Qingmei Yin a, Zhanbin Qin a,
⇑
Xinhao Yan a, Yanfei Wang a, Pingzhu Zhang a, Jinchao Zhang a
a Key Laboratory of Chemical Biology of Hebei Province, College of Chemistry and Environmental Science, Hebei University, Baoding 071002, China
b State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing 100191, China
a r t i c l e i n f o
a b s t r a c t
Novel pseudonucleosides with benzylamino group on 50-position (4) were synthesized by using the
microwave-assisted one-pot tandem Staudinger/aza-Wittig/reduction reaction in good yields of 55.2–
71.7%. The deacetylation of 4 afforded compounds 5. HIV-1 reverse transcriptase (RT) inhibitory and anti-
tumor activities were preliminarily evaluated with 5. The results showed that the new pseudonucleosides
(5) could effectively inhibit HIV-1 RT activity, but no antitumor activity.
Article history:
Received 1 August 2010
Revised 9 October 2010
Accepted 13 October 2010
Available online 19 October 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Pseudonucleosides
Staudinger/aza-Wittig/reduction
Microwave-assisted
HIV-RT inhibitory
Antitumor
The analogs of natural nucleoside have been a growing research
topic in the past decades due to their high potential as therapeutic
agents for the treatment of many infectious diseases and tumors.1
To develop novel anti-infective and antitumor drugs, various
chemically modified nucleosides have been proposed to improve
their biological activities. The typical modifications mainly focused
on the bases and sugars of the nucleosides. Some structurally mod-
ified analogs included heterocyclic-sugar nucleosides,2 unnatural
bases nucleosides,3 spirocyclic nucleosides,4 two-headed nucleo-
sides,5 and nucleotide analogs in which the phosphonate linkage
was replaced by amide,6 phosphoramidate,7 or sulphonamide.8
Moreover, it has been reported that in physiological condition,
the anion nucleoside, for example, nucleoside 50-monophosphate
could be hindered to cross the negatively charged cell mem-
branes.9 It would be imaged that the introduction of neutral lipo-
philic or positively charged moieties to the nucleoside might
facilitate the compound to penetrate the cell membrane and
increase its concentration inside of the cell.10 In light of this, we
conceived to synthesize a series of novel 50-arylamino nucleoside
derivatives for investigating their antitumor and antivirus
activities.
amine derivatives12 via the key imine intermediate. Based on the
tandem reaction, we have recently developed a convenient access
to synthesize novel thiazolindinone glycosides.13 Herein, we would
like to report a simple and efficient method to synthesize novel
50-arylamino nucleoside derivatives by the microwave-assisted
one-pot tandem Staudinger/aza-Wittig/reduction from 50-azido
nucleosides and aromatic aldehydes (Scheme 1) and the biological
activities of antitumor and HIV-RT inhibition.
5-Deoxy-5-azido-2,3-diacetyl-ribose (1) was prepared accord-
ing to the reported procedure from D
-ribose.14 Then, N-glycosyla-
tion reaction of 1 with trimethylsilylated uracil or 5-F-uracil
which was in situ generated in the presence of N,O-bis(trimethyl-
silyl)acetamide (BSA) afforded the corresponding 50-deoxy-50-azi-
do-20,30-diaceto-ribonucleosides (2) in good yield.15
Based on our previous works,13 the one-pot tandem Staudinger/
aza-Wittig/reduction reaction was explorated with azidonucleo-
side (2a) and 4-chlorobenzaldehyde (3a) under microwave irradi-
ation as shown in Scheme 2 and Table 1. It was found that the
addition of Molecular Sieves could dramatically improve the reac-
tion efficiency. Thus, as described in Table 1 entry 7, the one-pot
tandem synthesis were firstly performed at 60 °C by stirring the
mixture of the azidonucleoside (2a), triphenylphosphine (Ph3P,
1.2 equiv) and 4 Å MS (2 equiv) in anhydrous THF under micro-
wave irradiation for 5 min, then, 4-chlorobenzaldehyde (3a,
1.2 equiv) was added and the solution was stirred at 90 °C under
microwave irradiation for another 5 min to generate the imine
intermediate via an iminophosphorane, and followed by the reduc-
The tandem Staudinger/aza-Wittig reaction is one of very
important protocol for constructing C@N bond and has been suc-
cessfully used in the synthesis of nitrogenous heterocycle11 and
⇑
Corresponding author. Tel./fax: +86 312 5971116.
E-mail address: lixl@hbu.cn (X. Li).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.10.054

H. Chen et al. / Bioorg. Med. Chem. Lett. 21 (2011) 574–576
575
Base
Base
OAc
O
O
O
Staudinger
N3
N3
Ph3P
Ph3P
N
+
OAc
OAc
OAc
OAc
OAc
OAc
2
1
Ar CHO
3
Aza-Wittig
Base
Base
Reduction
Base
Deprotection
O
O
O
Ar
N
Ar
N
N
H
H
Ar
AcO
AcO
HO
OAc
HO
OAc
4
5
Scheme 1. One-pot tandem Staudinger/aza-Wittig/Reduction reaction for synthesizing 50-arylamino-nucleosides.
Base
Base
Table 2
O
a
O
N3
The yields of compounds 4 and 5
N
H
step 1: Staudinger
step 2: aza-wittig
step 3: reductin.
Yielda (%)
a
b
c
d
e
f
g
h
OAc
2a-b
OAc
X
OAc OAc
4a-h
4
5
70.7
82.3
71.7
71.6
67.6
84.6
69
84.1
66.3
84.3
63.4
80.3
55.2
72
58.1
85.5
Base
O
N
H
a
b
Isolated yield.
X
OH OH
5a-h
4, 5a-d: Base= uridine, X= 4-Cl; 2-Cl-6-F; 2, 6-di-Cl; 2-Cl.
4, 5e-h: Base= 5-F-uridine, X= 4-Cl; 2-Cl- 6-F; 2, 6-di-Cl; 2-Cl.
2a: Base= uridine
active binding site. It is also suggested that the compounds with
a N-linked neutral lipophilic groups at 50-position would be better
for the HIV-RT inhibitory activity. Although compound 5a where
chlorine existed at 4-position on the aromatic ring showed a more
significant HIV-RT inhibitory activity and its IC50 values was
2b: Base= 5-F-uridine
Scheme 2. Reagents and condition: (a) step (1) PPh3, 4 Å MS, THF, MW, 60 °C,
5 min; step (2) compound 3, MW, 90 °C, 5 min; step (3) NaBH3CN–AcOH, 0 °C,
10 min; (b) MeONa, MeOH, 50 °C.
2.82 0.81 lM, the position or the number of halo atoms on the
phenyl ring led to no obvious influence on the anti-HIV-RT activity.
The cytotoxicity of the compounds 5 against Hela cell lines (human
cervical cancer cells) was examined by the modified Mosmann’s
protocol,17 but showed no inhibition against the Hela-tumor cell
tive reaction with NaBH3CN–AcOH (2 equiv) at 0 °C for 10 min to
afford the corresponding 50-(4-chlorobenzylamino)-20,30-diacetyl-
uridine (4a). The total yield for the three steps was 70.7%. Under
the same conditions, the one-pot tandem reactions of 50-azido
nucleosides (2) and aromatic aldehydes (3) produced the corre-
sponding 50-arylamino-20,30-diacetyl-nucleosides 4a–h in good
yields as shown in Scheme 2 and Table 2, providing a convenient
one-pot multi-component tandem synthesis of 50-amino-nucleo-
side derivatives.
The deacetylation of 4a–h was carried out effectively in sodium
methoxide in methanolic solution at room temperature, afforded
the corresponding target products 5a–h in high yields (Table 2),
respectively.
(IC50 >200 lM).
In conclusion, we have designed and synthesized a series of no-
vel pseudonucleosides with benzylamino group on 50-position by
using the microwave-assisted one-pot tandem Staudinger/aza-
Wittig/reduction reaction starting from 50-azido nucleosides and
aromatic aldehydes, providing a convenient protocol for construct-
ing such 50-N-linked nucleoside analogs in good yields. The aimed
Table 3
HIV-1 reverse transcriptase (RT) inhibitory and antitumor activ-
ities were preliminarily evaluated with pseudonucleosides 5. The
RT inhibitory activities of 5 were evaluated by determining their
percentage inhibition of HIV-RT activity in HIV-1-RT kit by com-
parison with AZT,16 and the results were shown in Table 3. It could
be seen from the table that compounds 5 showed significant HIV-
RT inhibitory activity, better than that of positive control AZT,
implying that compound 5 with benzylamino group at 50-position
on nucleosides may be better accommodated into the HIV-1 RT
In vitro HIV-1-RT kit assay for compounds 5
Compounds
IC50
(l
M)
Compounds
IC50 (lM)
(HIV-RT kit assay)
(HIV-RT kit assay)
5a
5b
5c
5d
AZT
2.82 0.81
4.99 2.35
4.72 1.41
6.13 2.54
21.43 1.93
5e
5f
5g
5h
3.75 1.19
3.90 1.65
4.84 1.82
3.53 1.42
Table 1
Conditions optimization of the one-pot Staudinger/aza-Wittig/reduction
Entry
Ph3P (equiv)
Aldehyde (equiv)
Conditions of step 2 (M. W.)
Reduction reagent (equiv)
Conditions of step 3
Yielda (%)
1
2
3
4
1.5
1.5
1.5
1.5
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
2.0
1.2
80 °C, 10 min
90 °C, 5 min
80 °C, 10 min
90 °C, 5 min
90 °C, 5 min
90 °C, 5 min
90 °C, 5 min
NaBH4 (4.0)
NaBH4–AcOH (2.0)
NaBH3CN (4.0)
NaBH3CN–AcOH (4.0)
NaBH3CN–AcOH (2.0)
NaBH3CN–AcOH (2.0)
NaBH3CN–AcOH (2.0)
rt
—
0 °C, 3 min
0 °C, 30 min
0 °C, 10 min
0 °C, 10 min
0 °C, 10 min
0 °C, 10 min
31.2
42.9
46.8
45.2
45.3
70.7
5
6
7b
a
Isolated yield.
2.0 of 4 Å molecular sieves (MS) was added.
b

576
H. Chen et al. / Bioorg. Med. Chem. Lett. 21 (2011) 574–576
J.; Chênevert, R. J. Am. Chem. Soc. 2008, 130, 3264; (d) Xu, Q.; Katkevica, D.;
Rozners, E. J. Org. Chem. 2006, 71, 5906; (e) Plant, A.; Thompson, P.; Williams, D.
M. J. Org. Chem. 2008, 73, 3714; (f) O’ Mahony, G.; Sundgren, A.; Svensson, S.;
Grøtli, M. Tetrahedron 2007, 63, 6901; (g) Babic, A.; Gobec, S.; Gravier-Pelletier,
C.; Le Merrer, Y.; Pecar, S. Tetrahedron. 2008, 64, 9093.
compounds (5) showed notable in vitro anti-HIV-1 RT activity,
higher than that of AZT. The further synthesis and biological activ-
ity evaluation are underway in this laboratory.
7. (a) Cahard, D.; McGuigan, C.; Balzarini, J. Mini-Rev. Med. Chem. 2004, 4, 371; (b)
Drontle, D. P.; Wagner, C. R. Mini-Rev. Med. Chem. 2004, 4, 409.
Acknowledgments
8. (a) Somu, R. V.; Boshoff, H.; Qiao, C.; Bennett, E. M.; Barry, C. E., III; Aldrich, C. C.
J. Med. Chem. 2006, 49, 31; (b) Vannada, J.; Bennett, E. M.; Wilson, D. J.; Boshoff,
H. I.; Barry, C. E.; Aldrich, C. C. Org. Lett. 2006, 8, 4707.
The financial supports from the National Basic Research 973
Pre-research Program of China (2010CB534913), the National
Natural Science Foundations of China (NSFC) (20672027 and
20972039), the Natural Science Foundations of Hebei
(B2008000588), and open research fund of the State Key Laboratory
of Natural and Biomimetic Drugs, Peking University (20080205).
9. Roll, P. M.; Weinfeld, H.; Carroll, E.; Brow, G. B. J. Biol. Chem. 1956, 220, 439.
´
´
10. Romanowska, J.; Szymanska-Michalak, A.; Boryski, J.; Stawinski, J.; Loddo, R.;
Sanna, G.; Collu, G.; Secci, B.; La Colla, P.; Kraszewski, A. Bioorg. Med. Chem.
2009, 17, 3489.
11. (a) Palacios, F.; Alonso, C.; Aparicio, D.; Rubiales, G.; De los Santos, J. M.
Tetrahedron 2007, 63, 523; (b) Timmer, M. S. M.; Risseeuw, M. D. P.;
Verdoes, M.; Filippov, D. V.; Plaisier, J. R.; van der Marel, G. A.; Overkleeft, H.
S.; van Boom, J. H. Tetrahedron: Asymmetry 2005, 16, 177; (c) Singh, P. N. D.;
Klima, R. F.; Muthukrishnan, S.; Murthy, R. S.; Sankaranarayanan, J.;
Stahlecker, H. M.; Patel, B.; Gudmundsdóttir, A. D. Tetrahedron Lett. 2005,
46, 4213; (d) Fuwa, H.; Okamura, Y.; Morohashi, Y.; Tomita, T.; Iwatsubo, T.;
Kan, T.; Fukuyama, T.; Natsugari, H. Tetrahedron Lett. 2004, 45, 2323; (e)
Chen, J. H.; Forsyth, C. J. Org. Lett. 2003, 5, 1281; (f) Luo, Z. S.; Peplowski, K.;
Sulikowski, G. A. Org. Lett. 2007, 9, 5051; (g) Marsden, S. P.; McGonagle, A.
E.; McKeever-Abbas, B. Org. Lett. 2008, 10, 2589; (h) Yang, Y.-Y.; W Shou, G.
Z.; Chen, B.; Hong, D.; Wang, Y.-G. J. Org. Chem. 2008, 73, 3928; (i) Hirota, S.;
Kato, R.; Suzuki, M.; Soneta, Y.; Otani, T.; Saito, T. Eur. J. Org. Chem. 2008,
2075; (j) Freifeld, I.; Shojaei, H.; Dede, R.; Langer, P. J. Org. Chem. 2006, 71,
6165; (k) Eguchi, S. Arkivoc 2005, ii, 98; (l) Bellur, E.; Langer, P. Tetrahedron
Lett. 2006, 47, 2151; (m) Ménand, M.; Blais, J. C.; Valéry, J. M.; Xie, J. J. Org.
Chem. 2006, 71, 3295; (n) Lee, J. W.; Lee, U. Y.; Han, S. C.; Kim, J. H. Bull.
Korean Chem. Soc. 2009, 30(5), 1001.
Supplementary data
Supplementary data associated (experimental procedures and
characterization data for compounds 2, 4, and 5) with this article
can be found, in the online version, at doi:10.1016/j.bmcl.
2010.10.054.
References and notes
1. (a) De Clercq, E. J. Clin. Virol. 2004, 30, 115; (b) Hatse, S.; De Clercq, E.; Balzarini,
J. Biochem. Pharmacol. 1999, 58, 539; (c) Agrofoglio, L. A.; Suhas, E.; Farese, A.;
Condom, R.; Challand, S. R.; Earl, R. A.; Guedj, R. Tetrahedron 1994, 50, 10611;
(d) Khandazhinskaya, A.; Yasko, M.; Shirokova, E. Curr. Med. Chem. 2006, 13,
2953; (e) Oberg, B. Antiviral Res. 2006, 71, 90; (f) Khalil, N. S. A. M. Eur. J. Med.
Chem. 2007, 42, 1193; (g) Parker, W. B. Chem. Rev. 2009, 109, 2880.
2. Romeo, G.; Chiacchio, U.; Corsaro, A.; Merino, P. Chem. Rev. 2010, 110, 3337.
3. (a) Kimoto, M.; Moriyama, K.; Yokoyama, S.; Hirao, I. Bioorg. Med. Chem. Lett.
2007, 17, 5582; (b) Akri, K. E.; Bougrin, K.; Balzarini, J.; Faraj, A.; Benhida, R.
Bioorg. Med. Chem. Lett. 2007, 17, 6656; (c) Liu, W. Y.; Li, H. Y.; Zhao, B. X.; Shin,
D. S.; Lian, S.; Miao, J. Y. Carbohydr. Res. 2009, 344, 1270.
12. (a) Andre, B. C.; Alessandro, A. B.; Marc, K. J. Org. Lett. 2000, 24, 3777; (b)
Menand, M.; Blais, J. C.; Valery, J. J. Org. Chem. 2006, 71, 3295; (c) Maughan, M.
T.; Davies, I. G. Angew. Chem., Int. Ed. 2003, 42, 3788; (d) Timmer, M. M.;
Risseeuw, M. P.; Verdoes, M. Tetrahedron: Asymmetry 2005, 16, 177.
13. Chen, H.; Zhang, H.-H.; Feng, J.-N.; Li, X.-L.; Jiao, L.-L.; Qin, Z.-B.; Yin, Q.-M.;
Zhang, P.-Z.; Zhang, J.-C. Eur. J. Org. Chem. 2009, 6100.
14. (a) Ohrui, H.; Misawa, T.; Meguro, H. J. Org. Chem. 1985, 50, 3007; (b) Zhang, J.;
ˇ
Kovác, P. J. Carbohydr. Chem. 1999, 18(4), 461.
15. Hilbe, G. E.; Johnson, T. B. J. Am. Chem. Soc. 1930, 52, 4489.
16. Reverse Transcriptase Assay, Colorimetric kit, Roche Diagnostics GmbH, Roche
Applied Science, Sandhofer Strasse 116, D-68305 Mannheim, Germany.
17. Mosmann, T. J. Immunol. Methods 1983, 65, 55.
4. Hartung, R.; Paquette, L. A. J. Org. Chem. 2005, 70, 1597.
ˇ
5. Kašnar, B.; škarió, V.; Klaió, B.; Zinic´, M. Tetrahedron Lett. 1993, 34, 4997.
6. (a) Yeager, A. R.; Finney, N. S. J. Org. Chem. 2004, 69, 613; (b) Yeager, A. R.;
Finney, N. S. Bioorg. Med. Chem. 2004, 12, 6451; (c) Balg, C.; Huot, J. L.; Lapointe,