Synthesis and biological evaluation of thymine nucleosides fused with 3′,4′-tetrahydrofuran ring

Article abstract of DOI:10.1016/S0960-894X(03)00730-3

The pyrimidine nucleosides fused with 3′,4′-tetrahydrofuran ring were successfully synthesized, starting from 1,2; 5,6-di-O-isopropylidene-D-glucose and assayed for antiviral activities against HIV-1, HIV-2, EMCV, Cox. B3 and VSV. Thymine analogue (5) and

Full text of DOI:10.1016/S0960-894X(03)00730-3

Bioorganic & Medicinal Chemistry Letters 13 (2003) 3499–3501
Synthesis and Biological Evaluation of Thymine Nucleosides Fused
with 30,40-Tetrahydrofuran Ring
Myong Jung Kim,a Hea Ok Kim,b Hee-Doo Kim,c Joong Hyup Kim,d Lak Shin Jeonge
and Moon Woo Chuna,*
aCollege of Pharmacy, Seoul National University, Seoul 151-742, South Korea
bDivision of Chemistry andMolecular Engineering, Seoul National University, Seoul 151-742, South Korea
cCollege of Pharmacy, Sookmyung Women’s University, Seoul 140-742, South Korea
dKorea Institute of Science andTechnology, Seoul 136-791, South Korea
eCollege of Pharmacy, Ewha Womans University, Seoul 120-750, South Korea
Received 24May 2003; revised 9 July 2003; accepted 10 July 2003
Abstract—The pyrimidine nucleosides fused with 30,40-tetrahydrofuran ring were successfully synthesized, starting from 1,2;5,6-di-
O-isopropylidene-d-glucose and assayed for antiviral activities against HIV-1, HIV-2, EMCV, Cox. B3 and VSV. Thymine ana-
logue (5) and its corresponding 20-deoxy analogue (6) exhibited high cytotoxicity instead of giving antiviral activities.
# 2003 Elsevier Ltd. All rights reserved.
Introduction
group 1,6 oxirane 27 and oxethane 38 have been synthe-
sized and reported to have anti-HIV activity through
inhibition of HIV reversetranscriptase, but 30,40-cyclo-
pentane fused pyrimidine nucleoside 4 did not show
antiviral activity9 (Fig. 1).
A number of 20,30-dideoxy nucleosides such as 30-azido-
30-deoxythymidine (AZT), dideoxycytidine (ddC) and
dideoxyinosine (ddI) have been discovered to possess
significant antiviral activity against HIV1 and have
stimulated considerable interest as potential antiviral
agents.2 It has been suggested that proper conformation
of the dideoxynucleosides is required for them to exhibit
antiviral activity.3 Unmodified nucleosides exist in
either S-type (20-endo/30-exo) or N-type (20-exo/30-endo)
conformation, but due to the low energy barrier
between this two dominating conformers a fast equili-
brium between states exists in solution state.4 Therefore,
many approaches to lock the puckering of the furanose
ring into N-type or S-type have been made since HIV-1
reverse transcriptase is able to discriminate between two
conformationally locked carbocyclic AZT triphosphate
analogues.5
Therefore, based on these finding, novel 30,40-tetra-
hydrofuran fused pyrimidine nucleosides were designed
and synthesized to obtain further information regarding
the correlation between sugar ring conformation and
antiviral activity. Here, we report the synthesis of
Nowdays, a number of nucleoside analogues with fixed
sugar-ring puckering have been synthesized and eval-
uated for antiviral activity. Among them, bicyclic
nucleoside analogues containing a fused methylene
*Corresponding author. Tel.: +82-2880-8132; fax: +-82-2878-9682;
e-mail: mjnuh@hanmail.net
Figure 1. The rationale to the target nucleosides.
0960-894X/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0960-894X(03)00730-3

3500
M. J. Kim et al. / Bioorg. Med. Chem. Lett. 13 (2003) 3499–3501
pyrimidine nucleosides fused with 30,40- tetrahydrofurn
ring, starting from 1,2;5,6-di-O-isopropylidene-d-glu-
cose as potential antiviral agents.
ether 11 in 80% yield. 5,6-O-isopropylidene group of 11
was selectively removed using aqueous 75% acetic acid
to give the diol 12. Oxidative cleavage of 12 with sodium
periodate afforded the corresponding aldehyde 13,
which was immediately alkylated using 37% aqueous
formaldehyde followed by in situ Cannizarro reaction
to give the diol 14 in 70% overall yield. 14 was treated
with methanesulfonyl chloride to give the dimesylate 15
in 73% yield, which was debenzylated by Pd-catalyzed
dehydrogenolysis to afford 16 in 85% yield. The intra-
molecular cyclization of 16 with sodium hydride fol-
lowed by hydroxylation at 5-carbon of the resulting
tricyclic derivative 17 with aqueous sodium hydroxide
gave the bicyclic derivative 18 in 89% overall yield.
Treatment of 18 with acetic anhydride gave the acetate
19 in 91% yield, which was hydrolyzed with aqueous
85% formic acid and then successively acetylated to give
the glycosyl donor 20 in 91% yield as an anomeric
mixture.
Results and Discussion
Our synthetic strategy to the desired 30,40-tetra-
hydrofuran fused pyrimidine nucleosides (5 and 6) is to
synthesize the bicyclo furo[3,4-b]furan derivative (20) as
a glycosyl donor and then to condense with nucleosidic
base. Synthesis of the key glycosyl donor 20 from
1,2;5,6-di-O-isopropylidene-d-glucose (7) is shown in
Scheme 1.
1,2;5,6-Di-O-isopropylidene-d-glucose was oxidized
with PDC to give the ketone 8, which was treated with
methyl triphenylphosphonium bromide in the presence
of n-BuLi to give the olefin 9 in 83% overall yield.
Hydroboration followed by oxidation of the methylene
9 yielded the hydroxymethyl derivative 10 in 77% yield,
which was treated with benzyl bromide gave the benzyl
Condensation of the acetate 20 with silylated thymine
by modified Vorbrugen method10 gave the protected
Scheme 1. Reagents and Conditions: (a) PDC, Ac2O, CH2Cl2, reflux, 2 h; (b) Ph3PCH3Br, BuLi, THF, rt to 55 ꢀC, 3 h; (c) (i) BH3 SMe2, THF, rt,
.
3h; (ii) H2O2, 2N NaOH, rt, 2 h; (d) BnBr, NaH, TBAl, THF, rt, 16 h; (e) 75% AcOH, 55 ꢀC, 2 h; (f) NaiO4/H2O, EtOH, 0 ꢀC, 30 min;
(g) 37% HCHO, 2N NaOH, dioxane, rt, 3 days; (h) MsCl, pyridine, rt, 14h; (i) H , Pd(OH)2, EtOH, rt, 14h; (j) NaH, THF, 55 ꢀC, 1 h; (k) 0.5N
2
NaOH, reflux, 12 h; (l) Ac2O, pyridine, 12 h; (m) (i) 85% HCO2H, 55 ꢀC, 2 h; (ii) Ac2O, pyridine, rt, 16 h.
Scheme 2. Reagents and Conditions: (a) Thymine, BSA, TMSOTf, CH3CN, 60 ꢀC, 4h; (b) NH 4OH/MeOH, rt, 14h; (c) TBDPSCl, imidazole,
DMF, rt, 16 h; (d) PhOC(S)Cl, DMAP, Et3N, CH3CN, 0 ꢀC, 2 h; (e) Bu3SnH, AlBN, toulene, 100 ꢀC, 3 h; (f) TBAF, THF, rt, 1.5 h.

M. J. Kim et al. / Bioorg. Med. Chem. Lett. 13 (2003) 3499–3501
Table 1. Antiviral activities of the synthesized nucleosidesa,b
3501
Compd
Anti-HIV (EC50
)
Cytotoxicity CC50
Anti-PC (EC50
)
Cytotoxicity CC50
IIIB
ROD
EMCV
Cox, B3
VSV
5
6
95.80
>100.00
>0.540.51400.00
100.00
<0.80
1.64—
—
100.00
>4.11
—
100.00
>4.11
—
>100.00
0.01
—
3.45
4.11
AZT
Rib
0.0012
—
–
20.94
181.36
14.41
300.00
aEC50 (mg/mL) is the concentration of test compound required to inhibit virus-induced cytopaticity by 50%.
bCytotoxicity is expressed as the percentage of cell death of MT-4cells or HeLa cells cultured with test compounds. The number of viable cells was
determined by the MTT assay. The CC50 (mg/mL) is the concentration of test compound which cause 50% cytotoxicity to uninfected cells.
nucleosides 21 in 70% yield. Deprotection of ester
group of 21 with NH4OH/MeOH gave the desired
bicyclic nucleosde 511 in 93% yield. Primary hydroxyl
group of 5 was protected to give TBDPS ether 22 in
84% yield. Treatment of 22 with phenoxythiocarbonyl
chloride yielded 23, which upon treatment with tribu-
tyltin hydride in the presence of AIBN furnished the 20-
deoxy derivative 24 in 48% overall yield.12 Deblocking of
50-silyl group of 24 with tetrabutylammonium fluoride
(TBAF) in THF afforded the final 20-deoxy analogue 613
in 88% yield (Scheme 2).
References and Notes
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cited therein..
2. (a) Mitsuya, H.; Yarchoan, R.; Broger, S. Science 1990,
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Antiviral Chem. Chemother. 1990, 1, 163.
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Wang, J.; Wagner, R. W.; Matteucci, M. D. J. Med. Chem.
1996, 39, 3739.
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Ford, H.; Feldman, R. J.; Mitsuya, H.; George, C.; Barchi,
J. J. J. Am. Chem. Soc. 1998, 120, 2780.
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(b) Beard, A. R.; Butler, P. I.; Mann, J.; Partlett, N. K. Car-
bohydr. Res. 1990, 205, 87.
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31, 1475.
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All synthesized bicyclic nucleosides (5 and 6) were eval-
uated for their inhibitory effects on the replication of
HIV-1 (IIIB) and HIV-2 (ROD) in MT-4cells and
encephalomyocaditis virus (EMCV), Coxasakie virus
B3 (Cox. B3) and the vesicular stomatitis virus (VSV) in
HeLa cells cultures. Compound 5 exhibited weak anti-
viral activities against HIV and compound 6 exhibited
moderate and weak antiviral activities against EMCV,
Cox. B3 and VSV as shown in Table 1. But, the activity
of compounds 5 and 6 against tested viruses occurred at
cytotoxic concentration.
9. Bjorsne, M.; Szabo, T.; Samuelsson, B.; Classon, B. Bioorg.
Med. Chem. 1995, 3, 397.
10. Vorbrugen, H.; Krolikiewicz, K.; Bemmua, B. Chem. Ber.
1981, 114, 1234.
In summary, we have successively synthesized novel
bicyclic nucleosides fused with 30,40-tetrahydrofuran
ring, starting from 1,2;5,6-di-O-isopropylidene-d-glu-
cose via intramolecular cyclization. All synthesized
nucleosides exhibited high cytotoxicity without any sig-
nificant antiviral activities. The difference concerning
anti-HIV activity observed between the oxetane fused 3
and the structurally closely related 6 may be due to the
ring size of the fused ring. It is concluded that this class
of conformationally rigid nucleosides can be a new
template for antitumor agents. Synthesis of 30,40-meth-
ylene and oxirane fused nucleosides that are ring con-
tracted analogues of 3 and antitumor assays of 5 and 6
are in progress.
11. Selected data for 5: 1H NMR (300 MHz, DMSO-d6): d
1.78 (3H, d, J=0.72 Hz, CH3), 2.72 (1H, m, H-30), 3.44–3.73
(5H, m, H-50, H-400 and H-300a), 4.22–4.29 (2H, m, H-20 and H-
300b), 5.20 (1H, t, J=5.34Hz, OH), 5.56 (1H, d, J=4.62 Hz,
OH), 5.76 (1H, d, J=8.07, H-10), 7.64(1H, d, J=0.99, H-6),
11.28 (1H, brs, NH). FAB-MS m/z: 285 [M+H]+.
12. Robins, M. J.; Wilson, J. S.; Hansske, F. J. Am. Chem.
Soc. 1983, 105, 4059.
13. Selected data for 5: 1H NMR (300 MHz, DMSO-d6): d
1.77 (3H, d, J=0.99 Hz, CH3), 2.08–2.13 (2H, m, H-20), 2.78
(1H, m, H-30), 3.46–3.78 (6H, m, H-50, H-300 and H-400), 5.19
(1H, t, J=5.43 Hz, OH), 6.16 (1H, t, J=7.30, H-10), 7.70 (1H,
m d, J=1.2 Hz, H-6), 11.27 (1H, brs, NH). FAB-MS m/z: 269
[M+H]+.