Synthesis and in vitro antiviral activity evaluation of 9-(2-azido-2,3-dideoxy-β-D-threo-pentofuranosyl)adenine derivatives

Article abstract of DOI:10.1081/NCN-100002490

9-(2-Azido-2,3-dideoxy-β-D-threo-pentofuranosyl)adenine derivatives (1a-e) containing a lipophilic function at the N-6 position in the purine ring were prepared and evaluated for their antiviral activity. The compounds 1a-e turned out to be inactive as an

Full text of DOI:10.1081/NCN-100002490

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SYNTHESIS AND IN VITRO ANTIVIRAL ACTIVITY
EVALUATION OF 9-(2-AZIDO-2,3-DIDEOXY-β-D-THREO-
PENTOFURANOSYL)ADENINE DERIVATIVES
Satoshi Takamatsu a , Kunisuke Izawa b , Tokumi Maruyama c , Satoshi Katayama a ,
Naoko Hirose a & Erik De Clercq d
a AminoScience Laboratories, Ajinomoto Co., Inc. , 1-1, Suzuki-cho, Kawasaki-ku,
Kawasaki, Kanagawa, 210-8681, Japan
b AminoScience Laboratories, Ajinomoto Co., Inc. , 1-1, Suzuki-cho, Kawasaki-ku,
Kawasaki, Kanagawa, 210-8681, Japan
c Faculty of Pharmaceutical Sciences , Tokushima Bunri University , Yamashiro-cho,
Tokushima, 770-8514, Japan
d Rega Institute for Medical Research, Katholieke Universiteit Leuven ,
Minderbroedersstraat 10, Leuven, B-3000, Belgium
Published online: 07 Feb 2007.
To cite this article: Satoshi Takamatsu , Kunisuke Izawa , Tokumi Maruyama , Satoshi Katayama , Naoko Hirose & Erik
De Clercq (2001) SYNTHESIS AND IN VITRO ANTIVIRAL ACTIVITY EVALUATION OF 9-(2-AZIDO-2,3-DIDEOXY-β-D-THREO-
PENTOFURANOSYL)ADENINE DERIVATIVES, Nucleosides, Nucleotides and Nucleic Acids, 20:4-7, 1053-1057, DOI: 10.1081/
NCN-100002490
To link to this article: http://dx.doi.org/10.1081/NCN-100002490
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NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS, 20(4–7), 1053–1057 (2001)
SYNTHESIS AND IN VITRO ANTIVIRAL ACTIVITY
EVALUATION OF 9-(2-AZIDO-2,3-DIDEOXY-β-D-
THREO-PENTOFURANOSYL)ADENINE
DERIVATIVES
Satoshi Takamatsu, Kunisuke Izawa,1,∗ Tokumi Maruyama,2
Satoshi Katayama,1 Naoko Hirose,1 and Erik De Clercq3
1
AminoScience Laboratories, Ajinomoto Co., Inc. 1-1, Suzuki-cho,
Kawasaki-ku, Kawasaki, Kanagawa 210-8681, Japan
2Faculty of Pharmaceutical Sciences, Tokushima Bunri University,
Yamashiro-cho, Tokushima 770-8514, Japan
3Rega Institute for Medical Research, Katholieke Universiteit Leuven,
Minderbroedersstraat 10, Leuven B-3000, Belgium
ABSTRACT
9-(2-Azido-2,3-dideoxy-β-D-threo-pentofuranosyl)adenine derivatives (1a–e)
containing a lipophilic function at the N-6 position in the purine ring were
prepared and evaluated for their antiviral activity. The compounds 1a–e turned
out to be inactive as antiviral agents.
Dideoxynucleoside analogues in which 2ꢀ- or 3ꢀ-hydrogen in the carbohydrate
part is replaced by another atom or functional group have been extensively inves-
tigated (1) in drug research and biochemistry. This is because such replacement
often enhances biological activity and chemical or metabolic stability of the nucle-
oside. As an anti-HIV agent, 9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)
adenine (FddA, 2, (1,2) is one of the most representative examples of which C2ꢀ-
β-hydrogen in the sugar moiety is substituted with fluorine. Its azido analogue,
9-(2-azido-2,3-dideoxy-β-D-threo-pentofuranosyl)adenine (AzddA, 3) has also
been reported with quite good anti-HIV activity (1).
∗Corresponding author.
1053
ꢁ
C
Copyright 2001 by Marcel Dekker, Inc.
www.dekker.com

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TAKAMATSU ET AL.
In the course of our synthetic investigations (3) on 2, we developed a key inter-
mediate (6) to synthesize C2ꢀ-β substituted purine nucleosides. The intermediate
is applicable not only for the synthesis of C2ꢀ-β fluorinated dideoxynucleosides
such as 2, but also for the synthesis of C2ꢀ-β azidated dideoxynucleosides such
as 3. Since the intermediate has the chlorine at the 6 position of purine, it permits
the introduction of a variety of substituents at the 6 position. Although a series of
6-substituted amino analogue of FddA has received attention (4), we became inter-
ested in the synthesis of AzddA derivatives (1a–e) containing a lipophilic function
at the N-6 position of the purine ring.
Thus, 6-chloro-9-(3-deoxy-β-D-erythro-pentofuranosyl)-9H-purine (5) (5)
was obtained from inosine (4) by the modified Reese method (6) (Fig. 1). The
detail of this synthesis will be reported in due course (3). The 5ꢀ-hydroxyl group
in 5 was selectively protected with 3.3 equivalents of trityl chloride (TrCl) in the
presence of triethylamine (Et3N) and 4-dimethylaminopyridine (DMAP) in DMF
at 50◦C. After usual work-up and purification by silica gel chromatography, pure 6
was obtained in 89% yield.
The pivotal intermediate 7 was prepared through the azidation of the C2ꢀ-β
position of 6 as shown in Figure 1. The 2ꢀ-hydroxyl group of 6 was first reacted
with trifluoromethanesulfonic anhydride, then treated with sodium azide (NaN3)
in N,N-dimethylformamide at room temperature to afford the desired 7. After the
Figure 1.

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ANTIVIRAL ACTIVITY OF ADENINE NUCLEOSIDES
Table 1. Anti-HIV-1 and Anti-HIV-2 Activities of 1a–e
1055
EC50
CC50
Compound
Strain
(µg/ml)
(µg/ml)
SI
1a
IIIB
ROD
>101
107
=100.8
=106.9
<1
<1
1b
1c
1d
1e
IIIB
ROD
>115
>81
=115.1
<1
<1
=80.7
>125
>125
IIIB
ROD
>125
>125
×1
×1
IIIB
ROD
>125
>125
>125
>125
×1
×1
IIIB
ROD
>125
>125
>125
>125
×1
×1
silica gel column separation, the yield of 7 was 74% in 2 steps. The structure of 7
(7) was confirmed by IR spectrum (the 2114 cm−1 absorption showed the presence
of the azido group) and NMR spectrum (the vicinal coupling of H1ꢀ-H2ꢀ showed
the azido substitution at the C2ꢀ-β position). After the replacement of chlorine at
the 6 position of the purine ring in 7 with a variety of mono-alkyl and di-alkyl
amines, the trityl group at the 5ꢀ-hydroxyl group was hydrolyzed to furnish the
desired 1a–e (8). After the preparative silica gel plate separation, the yields of 1a–e
were 62–100% in 2 steps.
Anti-HIV activity and cytotoxicity for the compounds 1a–e were evaluated
(Table 1). The results indicated that all the compounds were inactive against the
replication of HIV-1 (IIIB) and HIV-2 (ROD) at subtoxic concentrations in acutely
infected MT-4 cells. These results may mean that compounds 1a–e are not recog-
nized by adenosine kinase.
In conclusion, 2ꢀ-β-azido-2ꢀ,3ꢀ-dideoxyadenosine derivatives 1a–e containing
a lipophilic function at the N-6 position in the adenine ring were prepared through
the pivotal intermediate 7. The compounds 1a–e were evaluated against the cyto-
pathicity of human immunodeficiency virus (HIV) in MT-4 cells. However, 1a–e
turned out to be inactive as anti-HIV agents.
REFERENCES
1. (a) Herdewijn, P.; Pauwels, R.; Baba, M.; Balzarini, J.; De Clercq, E. J. Med. Chem.
1987, 30, 2131–2137. (b) Pauwels, R.; Baba, M.; Balzarini, J.; Herdewijn, P.; Desmyter,
J.; Robins, M. J.; Zou, R.; Madej, D.; De Clercq, E. Biochem. Pharmacol. 1988, 37,
1317–1325. (c) Herdewijn, P.; Balzarini, J.; Pauwels, R.; Janssen, G.; Van Aerschot,
A.; De Clercq, E. Nucleosides & Nucleotides 1989, 8, 1231–1257.
2. Marquez, V. E.; Tseng, C. K.-H.; Kelley, J. A.; Mitsuya, H.; Broder, S.; Roth, J. S.;
Driscoll, J. S. Biochem. Pharmacol. 1987, 36, 2719–2722.

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TAKAMATSU ET AL.
3. To be submitted.
4. (a) Barchi, Jr., J. J.; Marquez, V. E.; Driscoll, J. S.; Ford, Jr., H.; Mitsuya, H.;
Shirasaka, T.; Aoki, S.; Kelley, J. A. J. Med. Chem. 1991, 34, 1647–1655. (b) Driscoll,
J. S.; Siddiqui, M. A.; Ford, Jr., H.; Kelley, J. A.; Roth, J. S.; Mitsuya, H.; Tanaka, M.;
Marquez, V. E. J. Med. Chem. 1996 39, 1619–1625.
5. Kumamoto, H.; Hayakawa, H.; Tanaka, H.; Shindoh, S.; Kato, K.; Miyasaka, T.; Endo,
K.; Machida, H.; Matsuda, A. Nucleosides & Nucleotides 1998, 17, 15–27.
6. Norman, D. G.; Reese, C. B. Synthesis 1983, 304–306.
1
7. Compound 7: H NMR (300 MHz, DMSO-d6) δ 8.75 (1H, s, H-2), 8.70 (1H, s H-
8), 7.21–7.43 (15H, m, 5ꢀO-Tr), 6.58 (1H, d, J = 6.3 Hz, H-1ꢀ), 4.95 (1H, ddd, J =
9.4, 6.9, 6.3 Hz, H-2ꢀ), 4.36–4.46 (1H, m, H-4ꢀ), 3.46-3.54 (1H, m, H-5ꢀa), 3.20–3.36
(1H, m, H-5ꢀb), 2.50–2.60 (1H, m, H-3ꢀa), 2.20–2.33 (1H, m, H-3ꢀb); 13C NMR
(75 MHz, DMSO-d6) δ 151.9, 151.6, 149.6, 145.8, 143.7, 131.2, 128.4, 128.1, 127.3,
86.4, 84.6, 78.2, 65.1, 61.6, 31.4; IR (KBr): 2114 cm−1; Anal. Calcd for C29H25N7O2Cl:
C, 64.74; H, 4.50; N, 18.22. Found: C, 64.75; H, 4.50; N, 18.19.
8. Compound 1a: 1H NMR (300 MHz, CDCl3) δ 8.38 (1H, s, H-8), 7.93 (1H, s H-2), 6.26
(1H, d, J = 6.2 Hz, H-1ꢀ), 6.08 (1H, bs, 6-NH), 4.90 (1H, bs, 5ꢀ-OH), 4.55 (1H, ddd, J
= 11.2, 5.0, 3.8 Hz, H-2ꢀ), 4.30–4.39 (1H, m, H-4ꢀ), 4.10 (1H, bd, J = 12.2 Hz, H-5ꢀa),
3.81 (1H, bd, J = 12.2 Hz, H-5ꢀb), 3.20 (3H, bs, N-CH3), 2.63 (1H, ddd, J = 15.4,
6.5, 6.5 Hz, H-3ꢀa), 2.44 (1H, ddd, J = 13.1, 6.7, 6.7 Hz, H-3ꢀb); 13C NMR (75 MHz,
CDCl3) δ 155.5, 153.1, 138.7, 120.0, 85.8, 79.5, 62.9, 62.6, 30.9, 27.6; IR (KBr): 2115
cm−1; HRMS (FAB+) calcd for C11H15N8O2 (M + H)+ 291.1318, found 291.1328.
1
Compound 1b: H NMR (300 MHz, CDCl3) δ 8.30 (1H, s, H-8), 7.92 (1H, s H-2),
6.26 (1H, d, J = 6.1 Hz, H-1ꢀ), 4.53 (1H, ddd, J = 11.1, 4.8, 3.7 Hz, H-2ꢀ), 4.44
(1H, bs, 5ꢀ-OH), 4.29–4.36 (1H, m, H-4ꢀ), 4.09 (1H, dd, J = 12.4, 2.3 Hz, H-5ꢀa),
3.81 (1H, bd, J = 12.4 Hz, H-5ꢀb), 3.54 (6H, bs, N(CH3)2), 2.61 (1H, ddd, J = 15.5,
6.5, 6.5 Hz, H-3ꢀa), 2.43 (1H, ddd, J = 12.7, 6.6, 6.6 Hz, H-3ꢀb); 13C NMR (75 MHz,
CDCl3) δ 155.0, 152.2, 150.0, 137.2, 120.4, 85.9, 79.3, 62.9, 62.7, 38.6, 30.7; IR
(KBr): 2115 cm−1; HRMS (FAB+) calcd for C12H17N8O2 (M+H)+ 305.1474, found
305.1479.
1
Compound 1c: H NMR (300 MHz, CDCl3) δ 8.45 (1H, s, H-8), 7.93 (1H, s H-2),
6.25 (1H, d, J = 6.2 Hz, H-1ꢀ), 6.05 (1H, bs, 6-NH), 4.55 (2H, ddd, J = 11.0,
4.9, 3.7 Hz, H-2ꢀ+5ꢀ-OH), 4.31–4.38 (1H, m, H-4ꢀ), 4.11 (1H, bd, J = 12.5 Hz,
H-5ꢀa), 3.78–3.85 (1H, m, H-5ꢀb), 3.02 (1H, bm, cyclopropane), 2.65 (1H, ddd, J = 15.5,
6.5, 6.5Hz, H-3ꢀa), 2.45(1H, ddd, J=13.2, 6.6, 6.6Hz, H-3ꢀb), 0.91–0.98(2H, m, cyclo-
propane), 0.65–0.70 (2H, m, cyclopropane); 13C NMR (75 MHz, CDCl3) δ 155.4, 152.9,
148.2, 138.8, 119.0, 84.4, 79.1, 62.3, 61.9, 30.3, 23.4, 7.0, 6.8; IR (KBr): 2113 cm−1
;
HRMS (FAB+) calcd for C13H17N8O2 (M + H)+ 317.1474, found 317.1472.
1
Compound 1d: H NMR (300 MHz, CDCl3) δ 8.35 (1H, s, H-8), 7.93 (1H, s H-
2), 6.25 (1H, d, J = 6.1 Hz, H-1ꢀ), 5.98 (1H, bs, 6-NH), 4.61 (1H, bs, 5ꢀ-OH), 4.55
(1H, ddd, J = 10.7, 4.9, 3.7 Hz, H-2ꢀ), 4.30–4.38 (1H, m, H-4ꢀ), 4.09 (1H, dd, J =
12.6, 2.2 Hz, H-5ꢀa), 3.81 (1H, dd, J = 12.6, 3.3 Hz, H-5ꢀb), 2.62 (1H, ddd, J =
15.3, 6.5, 6.5 Hz, H-3ꢀa), 2.44 (1H, ddd, J = 13.1, 6.7, 6.7 Hz, H-3ꢀb), 2.06–2.21
(2H, m, cyclopentane), 1.50–1.84 (7H, m, cyclopentane); 13C NMR (75 MHz, CDCl3)
δ 154.6, 153.1, 138.6, 120.1, 86.1, 79.5, 62.9, 62.6, 52.4, 33.4, 30.6, 32.7;IR(KBr):2112
cm−1; HRMS (FAB+) calcd for C15H21N8O2 (M + H)+ 345.1787, found 345.1777.

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ANTIVIRAL ACTIVITY OF ADENINE NUCLEOSIDES
1057
Compound 1e: 1H NMR (300 MHz, CDCl3) δ 8.33 (1H, s, H-8), 7.93 (1H, s H-2), 6.24
(1H, d, J = 6.0 Hz, H-1ꢀ), 5.80 (1H, bs, 6-NH), 4.72 (1H, bs, 5ꢀ-OH), 4.54 (1H, ddd, J =
10.8, 4.8, 3.7 Hz, H-2ꢀ), 4.29–4.38 (1H, m, H-4ꢀ), 4.09 (1H, dd, J = 12.6, 2.2 Hz,
H-5ꢀa), 3.81 (1H, dd, J = 12.6, 3.2 Hz, H-5ꢀb), 2.62 (1H, ddd, J = 15.2, 6.4, 6.4 Hz, H-
3ꢀa), 2.44 (1H, ddd, J = 13.2, 6.7, 6.7 Hz, H-3ꢀb), 2.04–2.16 (2H, m, cyclohexane),
1.20–1.86 (9H, m, cyclohexane); 13C NMR (75 MHz, CDCl3) δ 153.9, 153.1, 148.2,
138.4, 119.0, 85.0, 79.1, 62.5, 62.3, 49.1, 33.0, 30.5, 25.4, 24.7; IR (KBr): 2111 cm−1
;
HRMS (FAB+) calcd for C16H23N8O2 (M + H)+ 359.1944, found 359.1953.

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