Synthesis and anti-HIV activity of l-2′,3′-Dideoxy-4′-selenonucleosides (l-4′-Se-ddNs)

Article abstract of DOI:10.1007/s12272-019-01157-6

Based on the potent anti-HIV activity of l-2′,3′-dideoxycytidine (l-ddC), l-2′,3′-dideoxy-4′-selenonucleosides (l-4′-Se-ddNs) have been synthesized from natural chiral template, l-glutamic acid, using Pummerer-type condensation as a key step. All synthesized compounds were assayed for anti-HIV-1 activity, but none of them did show any significant antiviral activity up to 100?μM, probably due to conformational differences between l-ddC and l-4′-Se-ddC, induced by the bulky selenium atom, which might play an important role in phosphorylation by cellular kinase.

Full text of DOI:10.1007/s12272-019-01157-6

Arch. Pharm. Res.
Online ISSN 1976-3786
Print ISSN 0253-6269
https://doi.org/10.1007/s12272-019-01157-6
RESEARCH ARTICLE
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0
0
Synthesis and anti-HIV activity of L-2 ,3 -Dideoxy-4 -
0
selenonucleosides (L-4 -Se-ddNs)
1
1,2
1
1
•
Jinha Yu
Lak Shin Jeong
•
Gyudong Kim
1
•
Dnyandev B. Jarhad
•
Hong-Rae Kim
Received: 17 August 2018 / Accepted: 22 April 2019
Ó The Pharmaceutical Society of Korea 2019
0
0
Abstract Based on the potent anti-HIV activity of L-2 ,3 -
0
enzyme, reverse transcriptase (RT) (Deeks et al. 2015).
Thus, the inhibition of RT makes it impossible to replicate
the viral RNA genome, resulting in potent anti-HIV activity.
Nucleos(t)ide reverse transcriptase inhibitors (NRTIs) bind
to the catalytic site of RT after being converted to the
triphosphates and compete with natural substrate, nucleoside
triphosphate (NTP) against viral DNA polymerase (Sluis-
Cremer et al. 2000). So far, total 8 different NRTIs have been
approved by the Food and Drug Administration (FDA) and
0
0
dideoxycytidine (L-ddC), L-2 ,3 -dideoxy-4 -selenonucleo-
0
sides (L-4 -Se-ddNs) have been synthesized from natural
chiral template, L-glutamic acid, using Pummerer-type
condensation as a key step. All synthesized compounds
were assayed for anti-HIV-1 activity, but none of them did
show any significant antiviral activity up to 100 lM,
probably due to conformational differences between L-ddC
0
and L-4 -Se-ddC, induced by the bulky selenium atom,
0
0
0
which might play an important role in phosphorylation by
cellular kinase.
these are 2 ,3 -dideoxyinosine (ddI, didanosine), 2 ,3
0
0
0
-dideoxycytidine (ddC, zalcitabine), 3 -azido-3 -deox-
0
0
0
ythymidine (AZT, zidovudine), 2 ,3 -didehydro-2 ,3
0
0
0
0
0
0
0
0
Keywords Antiviral Á L-2 ,3 -Dideoxy-4 -
-dideoxythymidine (d4T, stavudine), (-)-2 ,3 -dideoxy-3
0
selenonucleosides Á L-Nucleoside Á Pummerer-type
-thiacytidine (lamivudine, (-)-3TC), (-)-5-fluoro-2 ,3
0
0
condensation Á L-4 -Se-ddC
-dideoxy-3 -thiacytidine (emtricitabine, (-)-FTC), aba-
cavir, and tenofovir (De Clercq 2009).
0
0
D-2 ,3 -Dideoxycytidine (D-ddC) is one of the most
potent anti-HIV-1 nucleosides (Mitsuya and Broder 1986).
It exerts the anti-HIV-1 activity by inhibiting RT compet-
itively and/or terminating viral DNA chain after incorpo-
ration (Mitsuya and Broder 1986). Based on the potent
anti-HIV-1 activity of D-ddC, we reported the synthesis of
Introduction
An estimated 36 million people are infected with human
immunodeficiency virus (HIV) worldwide. The HIV is a
member of the retroviridae family, which is transmitted as
single stranded, positive-sense enveloped RNA virus
0
0
0
0
the corresponding D-2 ,3 -dideoxy-4 -selenocytidine (D-4 -
Se-ddC) with anti-HIV-1 activity (Jeong et al. 2008a, b).
(
Deeks et al. 2015). The viral RNA genome is reverse
0
transcribed into double-stranded DNA by a virally encoded
To our disappointment, D-4 -Se-ddC did not exhibit any
anti-HIV-1 activity up to 100 lM although it showed the
same South conformation as D-ddC. No antiviral activity
might be attributed to the conformational differences,
resulting from bulky selenium atom whose steric effects
overwhelm the electronic (gauche) effects (Jeong et al.
2008a, b; Sahu et al. 2014, 2015).
Jinha Yu and Gyudong Kim contributed equally to this work.
&
Lak Shin Jeong
lakjeong@snu.ac.kr
1
2
Research Institute of Pharmaceutical Sciences, College of
Pharmacy, Seoul National University, Seoul 151-742, Korea
On the other hand, since the approval of lamivudine and
emtricitabine for the treatments of HIV-1 and HBV
infections, the unnatural or L-nucleosides have been paid
much attentions for the developments of novel antiviral
College of Pharmacy and Research Institute of Drug
Development, Chonnam National University,
Gwangju 61186, Korea
123

J. Yu et al.
agents because of less toxicity than the corresponding D-
nucleosides, while maintaining the antiviral activity
60F254 plates). Flash column chromatography was per-
formed on silica gel 60 (230–400 mesh, Merck). Unless
otherwise noted, materials were obtained from commercial
suppliers and were used without purification. All solvents
were purified and dried by standard techniques just before
use.
0 0
(
Math e´ and Gosselin 2006). For example, b-L-2 ,3 -
dideoxycytidine (L-ddC) exhibited potent anti-HIV-1 and
anti-HBV activities without the inhibition against mito-
chondrial DNA synthesis up to 100 lM, but the corre-
sponding D-ddC inhibited the mitochondrial DNA synthesis
in CEM cells with an IC50 value of 0.022 lM (Lin et al.
(S)-5-(Hydroxymethyl)dihydrofuran-2(3H)-one (6)
1
994). Another L-nucleoside, b-L-thymidine (L-dT,
Ò
Ò
Tyzeka or Telvivo ) was also approved for the treatment
of HBV (Nash 2009). It was turned out to be more effective
than lamivudine and less likely to cause resistance in
clinical trials.
Cyclization
To a cooled (0 °C) suspension of L-glutamic acid (20.0 g,
135.93 mmol) in H O (50 mL) and 1 N H SO (200 mL)
2
2
4
Thus, as L-ddC was also reported to exhibit potent anti-
HIV-1 and anti-HBV activities without cytotoxicity
endowed with D-ddC, it is very interesting to synthesize the
was dropwise added a solution of NaNO2 (14.1 g,
204.35 mmol) in H O (30 mL). After stirring at room
2
temperature for 15 h, the solvent was evaporated at
0
0
0
corresponding L-4 -Se-ddNs such as L-4 -Se-ddC (2), L-4 -
reduced pressure and diluted with H O (50 mL) and EtOAc
2
0
Se-ddU (3), and L-4 -Se-ddT (4) and to evaluate them for
anti-HIV-1 activity (Fig. 1). Herein, we report the synthe-
(150 mL). The organic layer was separated, and the
aqueous layer was extracted with EtOAc (100 mL 9 2).
The combined organic layers were washed successively
with H O and brine, dried over anhydrous MgSO , and
0
sis and anti-HIV-1 activity of L-4 -Se-ddNs, starting from
L-glutamic acid.
2
4
evaporated to give the crude 5 (14.6 g) as yellowish syrup,
which was used directly for the next step without
purification.
Materials and methods
Chemical synthesis
Reduction
1
13
H NMR (400 MHz, Varian Unity Inova) and C NMR
100 MHz, Varian Unity Inova) spectra were measured in
CDCl or CD OD and chemical shifts are recorded as parts
To a cooled (0 °C) solution of the crude 5 (14.6 g) in THF
(200 mL) was dropwise added BH ,Me S (148 mL, 2 M
(
3
2
solution in THF, 295.90 mmol) under N . After stirring at
3
3
2
per million (d) relative to the solvent peak. Coupling
constants (J) are reported in hertz (Hz). Optical rotations
were determined on Jasco III (Jasco, Sapporo, Japan) in
appropriate solvent. UV spectra were recorded on U-3000
room temperature for 1 h, the reaction mixture was quen-
ched with MeOH (200 mL) and evaporated. The residue
was purified by flash column chromatography (silica gel,
CH Cl /MeOH, 30/1) to give 6 (10.4 g, 61%) as yellowish
2
2
1
(
Hitachi, Tokyo, Japan) in methanol or water. Melting
points were measured on melting point apparatus B-540
B u¨ chi Labortechnik AG, Flawil, Switzerland). Elemental
syrup: H NMR (400 MHz, CDCl ) d 4.61–4.66 (m, 1 H,
3
H-4), 3.92 (dd, J = 2.8, 12.4 Hz, 1 H, H-5), 3.67 (dd, J =
4.8, 12.4 Hz, 1 H, H-5), 2.51–2.67 (m, 2 H, H-2, H-2),
2.23–2.32 (m, 1 H, H-3), 2.10–2.20 (m, 1 H, H-3); LRMS
(
analysis (C, H, and N) were measured on automatic ele-
mental analyzer (ThermoQuest Italia S. p. A.) to determine
the purity of all synthesized compounds, and the results
were within ± 0.4% of the calculated values, confirming
C 95% purity. Mass spectra obtained with VG Trio-2 GC-
MS instrument (a VG instruments group, Altrincham, UK).
Reactions were checked with TLC (Merck precoated
?
1
(FAB) m/z 117 [M?H] ; H NMR and mass spectral data
are consistent with the literature values (Wrona et al.
2010).
Fig. 1 The rationale for the
design of the target nucleosides
2
–4
1
23

0
0
0
0
Synthesis and anti-HIV activity of L-2 ,3 -Dideoxy-4 -selenonucleosides (L-4 -Se-ddNs)
(S)-5-(((tert-Butyldiphenylsilyl)oxy)methyl)
dihydrofuran-2(3H)-one (7)
(S)-5-((tert-Butyldiphenylsilyl)oxy)pentane-1,4-diyl
dimethanesulfonate (9)
To a solution of 6 (2.38 g, 20.45 mmol) in anhydrous
CH Cl (100 mL) were successively added triethylamine
To a cooled (0 °C) solution of 8 (4.09 g, 11.41 mmol) in
anhydrous CH Cl (40 mL) were successively added
2
2
2
2
(
(
(
7.13 mL,
51.13 mmol),
4-(dimethylamino)pyridine
4-(dimethylamino)pyridine (0.279 g, 2.28 mmol), triethy-
lamine (12.72 mL, 91.28 mmol) and methanesulfonyl
0.50 g, 4.09 mmol) and tert-butyl(chloro)diphenylsilane
7.85 mL, 30.68 mmol) at room temperature under N2.
chloride (3.53 mL, 45.64 mmol) under N (g). After stir-
2
After stirring at the same temperature for 2 h, the reaction
ring for 0.5 h at room temperature, the mixture was
mixture was quenched with H O (100 mL), and the organic
2
quenched with saturated NaHCO solution and diluted with
3
layer was separated, and the aqueous layer was extracted
CH Cl . The organic layer was separated, and the aqueous
2
2
with CH Cl (50 mL 9 2). The combined organic layers
2
layer was extracted with CH Cl (50 mL 9 2). The com-
2 2
2
were washed successively with H O and brine, dried over
2
bined organic layers were washed successively with H O
2
anhydrous MgSO , filtered, and evaporated. The residue
4
and saturated brine, dried over anhydrous MgSO , filtered,
4
was purified by column chromatography (silica gel, hex-
and evaporated. The residue was purified by column
anes/EtOAc, 8/1) to give 7 (6.74 g, 93%) as a white solid:
1
chromatography (silica gel, hexanes/EtOAc, 3/1) to give 9
1
(5.17 g, 88%) as colorless syrup: H NMR (400 MHz,
mp 75.9–77.2 °C; H NMR (400 MHz, CDCl ) d
3
7
.65–7.68 (m, 4 H, phenyl in TBDPS), 7.38–7.47 (m, 6 H,
CDCl ) d 7.63–7.67 (m, 4 H, phenyl in TBDPS), 7.39–7.48
3
phenyl in TBDPS), 4.58–4.63 (m, 1 H, H-4), 3.89 (dd, J =
(m, 6 H, phenyl in TBDPS), 4.74–4.78 (m, 1 H, H-4),
4.22–4.27 (m, 2 H, H-5, H-5), 3.83 (dd, J = 6.0, 11.2 Hz, 1
H, H-1), 3.74 (dd, J = 4.0, 11.6 Hz, 1 H, H-1), 2.99 (d, J =
3
5
2
.6, 11.2 Hz, 1 H, H-5), 3.70 (dd, J = 3.6, 11.2 Hz, 1 H, H-
), 2.64–2.73 (m, 1 H, H-2), 2.47–2.56 (m, 1 H, H-2),
.18–2.34 (m, 2 H, H-3, H-3), 1.06 (s, 9 H, 3 9 CH -tert-
3
5.2 Hz, 6 H, 2 9 CH -methanesulfonyl), 1.79–1.89 (m, 4
3
1
3
butyl in TBDPS); C NMR (100 MHz, CDCl ) d 177.6,
H, H-2, H-2, H-3, H-3), 1.07 (s, 9 H, 3 9 CH -tert-butyl in
3
3
1
3
1
35.8, 135.7, 133.2, 132.8, 130.1, 128.1, 80.2, 65.7, 28.8,
24
TBDPS); C NMR (100 MHz, CDCl ) d 135.8, 135.7,
3
?
2
7.0, 23.9, 19.4; LRMS (FAB) m/z 355 [M?H] ; [a]
=
132.9, 132.7, 130.35, 130.29, 128.2, 82.7, 69.3, 65.5, 38.9,
D
?
27.42 (c 0.06, CH OH); Calcd for C H O Si: C, 71.15;
3 21 26 3
37.6, 27.7, 27.1, 24.9, 19.4; LRMS (FAB) m/z 515
23
?
H, 7.39. Found: C, 71.05; H, 7.34.
[M?H] ; [a]D = - 7.75 (c 0.528, CH OH); Calcd for
3
C H O S Si: C, 53.67; H, 6.66. Found: C, 53.85; H, 6.23.
23 34 7 2
(S)-5-(tert-Butyldiphenylsilanyloxy)pentane-1,4-diol (8)
(R)-tert-Butyldiphenyl((tetrahydroselenophen-2-
yl)methoxy)silane (10)
To cooled (0 °C) solution of 7 (35.9 g, 101.21 mmol) in
THF (360 mL) was added lithium borohydride (4.64 g,
2
02.42 mmol) in one portion under N (g). After heating at
2
To a cooled (0 °C) suspension of selenium powder (2.31 g,
29.21 mmol) in EtOH (250.0 mL) was added sodium
borohydride (3.31 g, 87.63 mmol) in 10 portions, until the
color of the reaction mixture changed from black suspen-
sion to colorless solution. To the above-generated solution
was dropwise added dimesylate 9 (10.02 g, 19.47 mmol) in
THF (150 mL). After being heated at 60 °C (bath tem-
perature) with stirring for 15 h, the reaction mixture was
cooled to room temperature and evaporated, and diluted
4
0 °C (bath temperature) with stirring for 2 h, the reaction
mixture was quenched with H O (100 mL), and diluted
2
with EtOAc. The organic layer was separated, and the
aqueous layer was extracted with EtOAc (50 mL 9 2). The
combined organic layers were washed successively with
H O and brine, dried over anhydrous MgSO , filtered, and
2
4
evaporated. The residue was purified by flash column
chromatography (silica gel, hexanes/EtOAc, 2/1) to give 8
(
1
33.8 g, 93%) as colorless syrup: H NMR (400 MHz,
with H O and EtOAc (100 mL). The organic layer was
2
CDCl ) d 7.66–7.69 (m, 4 H, phenyl in TBDPS), 7.38–7.46
separated, and the aqueous layer was extracted with EtOAc
3
(
m, 6 H, phenyl in TBDPS), 3.75–3.79 (m, 1 H, H-4),
.50–3.67 (m, 4 H, H-1, H-1, H-5, H-5), 2.98 (bs, 2 H, 2 9
OH), 1.63–1.68 (m, 2 H, H-2, H-2), 1.53–1.56 (m, 1 H, H-
), 1.43–1.50 (m, 1 H, H-3), 1.08 (s, 9 H, 3 9 CH -tert-
(2 9 100 mL). The combined organic layers were washed
3
successively with H O and saturated brine, dried over
2
anhydrous MgSO , filtered, and evaporated. The residue
4
3
was purified by column chromatography (silica gel, hex-
3
1
3
butyl in TBDPS); C NMR (100 MHz, CDCl ) d 136.1,
anes/EtOAc, 20/1) to give 10 (6.92 g, 88%) as pale yellow
1
3
1
7
3
35.9, 135.7, 133.29, 133.27, 130.0, 128.0, 127.9, 127.8,
syrup: H NMR (400 MHz, CDCl ) d 7.67–7.70 (m, 4 H,
3
2.1, 68.1, 62.9, 29.9, 29.8, 27.0, 19.4; LRMS (FAB) m/z
?
phenyl in TBDPS), 7.37–7.45 (m, 6 H, phenyl in TBDPS),
3.69–3.78 (m, 3 H, H-4, H-5, H-5), 2.85–2.89 (m, 2 H, H-1,
H-1), 1.93–2.04 (m, 4 H, H-2, H-2, H-3, H-3), 1.08 (s, 9 H,
24
59 [M?H] ; [a] = - 5.20 (c 6.87, CH OH); Calcd for
D
3
C H O Si: C, 70.35; H, 8.43. Found: C, 70.47; H, 8.28.
21 30 3
1
3
3
9 CH -tert-butyl in TBDPS); C NMR (100 MHz,
3
123

J. Yu et al.
0 0 0
H-5 , H-5 ), 2.33–2.42 (m, 1 H, H-2 ), 2.14–2.24 (m, 2 H,
CDCl ) d 135.8, 135.7, 133.8, 133.7, 129.8, 127.8, 68.1,
3
0
0
0
4
6.1, 35.1, 31.6, 27.0, 25.0, 19.5; LRMS (FAB) m/z 403
?
H-2 , H-3 ), 1.86–1.92 (m, 1 H, H-3 ), 1.10 (s, 9 H, 3 9
13
24
M?H] ; [a] = - 33.26 (c 5.12, CH OH); Calcd for
[
CH -tert-butyl in TBDPS); C NMR (100 MHz, CDCl ) d
D
3
3
3
C H OSeSi: C, 62.51; H, 6.99. Found: C, 62.73; H, 6.60.
21 28
170.5, 149.1, 135.9, 135.8, 133.9, 130.4, 130.3, 130.0,
1
28.5, 128.1, 96.8, 67.1, 61.3, 50.4, 39.4, 31.8, 27.1, 27.0,
?
23
19.5; LRMS (FAB) m/z 618 [M?H] ; [a]D = ? 40.00
(c 1.78, CH Cl ); Calcd for C H N O SeSi: C, 62.32; H,
(R)-tert-Butyldiphenyl((tetrahydroselenophen-2-
yl)methoxy)silane-1-oxide (11)
2
2
32 35 3 3
5.72; N, 6.81. Found: C, 62.72; H, 5.48; N, 6.99.
To a cooled (- 78 °C) solution of 10 (3.11 g, 7.72 mmol)
in anhydrous CH Cl (60 mL) was dropwise added a
N-(1-((2R,5R)-5-(((tert-butyldiphenylsilyl)oxy)
methyl)tetrahydroselenophen-2-yl)-2-oxo-1,2-
dihydropyrimidin-4-yl)benzamide (13)
2
2
solution of 3-chloroperbenzoic acid (1.90 g, 8.49 mmol,
7%) in anhydrous CH Cl (30 mL) and the reaction
7
2
2
mixture was stirred at the same temperature for 45 min.
The reaction mixture was quenched with saturated
NaHCO solution and diluted with CH Cl . The organic
1
Yield = 8%, UV kmax (CH OH) 260.5 nm; H NMR
3
(400 MHz, CDCl ) d 8.36 (d, J = 7.6 Hz, 1 H, H-6), 7.90-
3
2
2
3
layer was separated, and the aqueous layer was extracted
7.92 (m, 2 H, phenyl in Bz), 7.37–7.69 (m, 14 H, phenyl in
0
with CH Cl (50 mL 9 2). The combined organic layers
2
Bz, phenyl in TBDPS, H-5), 6.57 (t, J = 6.0 Hz, 1 H, H-1 ),
0
2
were washed successively with H O and brine, dried over
2
4.09–4.16 (m, 1 H, H-4 ), 3.84 (dd, J = 7.2, 10.4 Hz, 1 H,
0 0
anhydrous MgSO , filtered, and evaporated. The residue
4
H-5 ), 3.73 (dd, J = 7.2, 10.4 Hz, 1 H, H-5 ), 2.42–2.45 (m,
0 0 0 0
2 H, H-2 , H-2 ), 2.02–2.15 (m, 2 H, H-3 , H-3 ), 1.07 (s, 9
was purified by column chromatography (silica gel, CH2-
1
H, 3 9 CH -tert-butyl in TBDPS); C NMR (100 MHz,
3
Cl /CH OH, 15/1) to give 11 (3.17 g, 98%) as colorless
2 3
3
syrup, which was immediately used for next step.
CDCl ) d 160.1, 151.3, 135.82, 135.76, 133.3, 133.2,
3
1
30.2, 129.4, 128.1, 96.1, 67.1, 61.1, 50.0, 39.2, 32.1, 30.0,
?
23
27.0, 19.5; LRMS (FAB) m/z 618 [M?H] ; [a]D = ?
10.02 (c 1.43, CH Cl ); Calcd for C H N O SeSi: C,
General procedure for the synthesis of 12–15
1
2
2
32 35 3 3
4
To a suspension of N -benzoylcytosine, uracil or thymine
62.32; H, 5.72; N, 6.81. Found: C, 62.66; H, 5.44; N, 7.01.
(
1 equiv) in anhydrous toluene (0.23 M) were added tri-
ethylamine (4 equiv) and trimethylsilyl trifluoromethane-
The mixture of 1-((2R,5R)-5-(((tert-butyldiphenylsilyl)
oxy)methyl)tetrahydroselenophen-2-yl)pyrimidine-
2,4(1H,3H)-dione (a of 14) and 1-((2S,5R)-5-(((tert-
butyldiphenylsilyl)oxy)methyl)tetrahydroselenophen-2-
yl)pyrimidine-2,4(1H,3H)-dione (b of 14)
sulfonate (8 equiv) under N (g). After stirring at room
2
temperature for 1 h, anhydrous CH Cl (0.6 M) was added.
2
2
To a cooled (0 °C) solution of above generated-reaction
mixture was added a solution of 11 (1 equiv) in CH Cl
2
2
(
0.6 M) followed by triethylamine (4 equiv) in anhydrous
toluene (0.6 M). The reaction mixture was heated at 70 °C
bath temperature) with stirring for 15 h, and then cooled,
Yield = 13%, (a ? b mixture); pale brownish syrup; UV
1
(
kmax (CH OH) 265.5 nm; H NMR (400 MHz, CDCl ) d
3
3
quenched with saturated NaHCO3 solution, and diluted
with CH Cl . The organic layer was separated, and the
10.37 (s, 2 H), 7.34–7.81 (m, 20 H), 6.48–6.53 (m, 2 H),
5.80 (d, J = 8.0 Hz, 1 H), 5.62 (d, J = 8.0 Hz, 1 H),
3.68–4.13 (m, 6 H), 1.89–2.40 (m, 10 H), 1.07 (s, 9 H),
1.05 (s, 9 H); Calcd for C H N O SeSi: C, 58.47; H,
2
2
aqueous layer was extracted with CH Cl . The combined
2
2
organic layers were filtered through Celite, washed suc-
2
5 30 2 3
cessively with H O and brine, dried over anhydrous
2
5.89; N, 5.45. Found: C, 58.77; H, 5.75; N, 5.85.
MgSO , filtered, and evaporated. The residue was purified
4
by column chromatography (silica gel, hexanes/EtOAc) to
The mixture of 1-((2R,5R)-5-(((tert-butyldiphenylsilyl)oxy)
methyl)tetrahydroselenophen-2-yl)-5-methylpyrimidine-
give 12–15.
2,4(1H,3H)-dione (a of 15) and 1-((2S,5R)-5-(((tert-
N-(1-((2S,5R)-5-(((tert-butyldiphenylsilyl)oxy)methyl)
tetrahydroselenophen-2-yl)-2-oxo-1,2-dihydropyrimidin-4-
yl)benzamide (12)
butyldiphenylsilyl)oxy)methyl)tetrahydroselenophen-2-yl)-
5-methylpyrimidine-2,4(1H,3H)-dione (b of 15)
Yield = 16%, a ? b mixture; pale brownish syrup; UV
1
1
Yield = 8%, UV kmax (CH OH) 260.0 nm; H NMR
kmax (CH Cl ) 271.5 nm; H NMR (400 MHz, CDCl ) d
3
2
2
3
(
400 MHz, CDCl ) d 8.32 (d, J = 7.6 Hz, 1 H, H-6),
.90–7.92 (m, 2 H, H-5, phenyl in Bz), 7.68–7.73 (m, 4 H,
7.65–7.71 (m, 8 H), 7.58 (d, J = 1.2 Hz, 2 H) 7.38–7.47 (m,
2 H), 6.48–6.54 (m, 2 H), 4.10–4.17 (m, 1 H), 3.84–3.91
(m, 4 H), 3.70–3.74 (m, 1 H), 2.09–2.46 (m, 8 H),
1.83–2.02 (m, 6 H), 1.08 (s, 9 H), 1.06 (s, 9 H); Calcd for
3
7
phenyl in Bz), 7.40–7.61 (m, 10 H, phenyl in TBDPS), 6.57
0 0
pseudo t, J = 4.0 Hz, 1 H, H-1 ), 3.83–4.13 (m, 3 H, H-4 ,
(
1
23

0
0
0
0
Synthesis and anti-HIV activity of L-2 ,3 -Dideoxy-4 -selenonucleosides (L-4 -Se-ddNs)
C H N O SeSi: C, 59.19; H, 6.11; N, 5.31. Found: C,
26 32 2 3
isomer 18a (174 mg, 43%) as white foam and a-isomer
18b (175 mg, 43%) as white foam.
5
8.99; H, 6.32; N, 5.11.
1
For b-Isomer (18a): UV kmax (CH OH) 252.5 nm; H
3
The mixture of 1-((2R,5R)-5-(hydroxymethyl)
tetrahydroselenophen-2-yl)pyrimidine-2,4(1H,3H)-
dione (a of 16) and 1-((2S,5R)-5-(hydroxymethyl)
tetrahydroselenophen-2-yl)pyrimidine-2,4(1H,3H)-
dione (b of 16)
NMR (400 MHz, CDCl ) d 8.04–8.07 (m, 2 H, phenyl in
Bz), 7.99 (d, J = 8.4 Hz, 1 H, H-6), 7.91–7.93 (m, 2 H,
3
phenyl in Bz), 7.58–7.66 (m, 2 H, phenyl in Bz), 7.45–7.50
0
(m, 4 H, phenyl in Bz), 6.52 (t, J = 6.4, 1 H, H-1 ), 5.79 (d,
J = 8.0 Hz, 1 H, H-5), 4.72 (dd, J = 7.2, 11.6 Hz, 1 H, H-
0
0
5
), 4.57 (dd, J = 6.4, 11.6 Hz, 1 H, H-5 ), 4.07–4.11 (m, 1
0 0
To a solution of 14 (0.48 g, 0.93 mmol) in anhydrous THF
(
H, H-4 ), 2.42–2.48 (m, 1 H, H-2 ), 2.26–2.33 (m, 2 H, H-
13
2 , H-3 ), 2.13–2.18 (m, 1 H, H-3 ); C NMR (100 MHz,
0
0
0
20 mL) was dropwise added tetra-n-butylammonium flu-
oride solution (0.74 mL, 1 M in THF) under N (g). After
2
CDCl ) d 171.1, 168.8, 166.4, 162.3, 149.6, 141.7, 135.4,
3
stirring at room temperature for 0.5 h, the reaction mixture
was evaporated and the residue was purified by flash col-
umn chromatography (silica gel, CH Cl /CH OH, 20/1) to
133.8, 133.7, 131.5, 130.7, 130.3, 129.8, 129.7, 129.5,
128.8, 128.6, 102.6, 67.0, 59.3, 45.1, 38.1, 32.9; LRMS
?
23
(FAB) m/z 483 [M?H] ; [a]D = ? 2.50 (c 3.58, CH Cl );
2
2
3
2
2
1
give 16 (0.24 g, 91%, a ? b mixture) as white foam: H
Calcd for C H N O Se: C, 57.15; H, 4.17; N, 5.80.
23 20 2 5
NMR (400 MHz, CDCl ) d 8.13 (d, J = 8.4 Hz, 1 H), 8.03
Found: C, 57.55; H, 4.45; N, 5.47.
3
1
(
d, J = 8.0 Hz, 1 H), 6.46 (t, J = 6.8 Hz, 1 H), 6.42 (t, J =
For a-Isomer (18b): UV kmax (CH OH) 253.5 nm; H
3
6
.0 Hz, 1 H), 5.76 (d, J = 6.0 Hz, 1 H), 5.74 (d, J = 6.0 Hz,
NMR (400 MHz, CDCl ) d 8.02–8.05 (m, 2 H, phenyl in
3
1
H), 4.07–4.14 (m, 1 H), 3.74–3.93 (m, 4 H), 3.57–3.62
Bz), 7.89–7.94 (m, 2 H, phenyl in Bz), 7.63–7.67 (m, 1 H,
(
m, 1 H), 2.43–2.51 (m, 1 H), 2.17–2.39 (m, 5 H),
.06–2.13 (m, 1 H), 1.91–2.00 (m, 1 H); Calcd for C9-
H N O Se: C, 39.28; H, 4.40; N, 10.18. Found: C, 39.45;
phenyl in Bz), 7.56–7.61 (m, 1 H, phenyl in Bz), 7.44–7.51
0
2
(m, 5 H, phenyl in Bz, H-6), 6.58 (t, J = 6.4 Hz, 1 H, H-1 ),
5.90 (d, J = 8.0 Hz, 1 H, H-5), 4.58 (dd, J = 7.2, 10.8 Hz, 1
0 0 0
1
2 2 3
H, 4.16; N, 10.58.
H, H-4 ), 4.31–4.40 (m, 2 H, H-5 , H-5 ), 2.58–2.63 (m, 1
0
0
H, H-2 ), 2.34–2.39 (m, 1 H, H-2 ), 2.04–2.18 (m, 2 H, H-
13
0
0
The mixture of 1-((2R,5R)-5-(hydroxymethyl)
tetrahydroselenophen-2-yl)-5-methylpyrimidine-
3 , H-3 ); C NMR (100 MHz, CDCl ) d 168.8, 166.2,
3
162.0, 149.6, 141.6, 135.4, 133.5, 131.5, 130.7, 129.8,
2
,4(1H,3H)-dione (a of 17) and 1-((2S,5R)-5-
hydroxymethyl)tetrahydroselenophen-2-yl)-5-
129.8, 129.4, 128.7, 102.9, 67.6, 58.6, 44.9, 38.7, 33.6;
?
23
(
LRMS (FAB) m/z 483 [M?H] ; [a]D = - 21.79 (c 0.98,
CH OH); Calcd for C H N O Se: C, 57.15; H, 4.17; N,
methylpyrimidine-2,4(1H,3H)-dione (b of 17)
3
23 20 2 5
5.80. Found: C, 57.54; H, 4.02; N, 5.73.
Compound 15 (0.55 g, 1.04 mmol) was converted to
compound 17 (0.28 g, 95%, a ? b mixture) using a similar
procedure to that used in the preparation of compound 16;
((2R,5S)-5-(3-Benzoyl-5-methyl-2,4-dioxo-3,4-
dihydropyrimidin-1(2H)-yl)tetrahydroselenophen-2-
yl)methyl benzoate (19a) and ((2R,5R)-5-(3-benzoyl-5-
methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-
yl)tetrahydroselenophen-2-yl)methyl benzoate (19b)
1
white foam; H NMR (400 MHz, CDCl ) d 7.94 (s, 1 H),
3
7
.80 (s, 1 H), 6.48 (t, J = 6.8 Hz, 1 H), 6.43 (t, J = 6.0 Hz, 1
H), 4.12–4.15 (m, 1 H), 3.75–3.93 (m, 4 H), 3.58–3.63 (m,
H), 2.13–2.49 (m, 8 H), 1.88–1.93 (m, 6 H); Calcd for
C H N O Se: C, 41.53; H, 4.88; N, 9.69. Found: C,
1
Compound 17 (0.28 g, 0.97 mmol) was converted to
compound 19a (193 mg, 40%) and 19b (202 mg, 42%)
using a similar procedure to that used in the preparation of
compound 18a and 18b; white foam; For b-Isomer (19a):
1
0 14 2 3
4
1.35; H, 4.47; N, 9.34.
(
(2R,5S)-5-(3-Benzoyl-2,4-dioxo-3,4-
1
dihydropyrimidin-1(2H)-yl)tetrahydroselenophen-2-
yl)methyl benzoate (18a) and ((2R,5R)-5-(3-benzoyl-
UV kmax (CH OH) 253.5 nm; H NMR (400 MHz, CDCl )
3
3
d 8.06–8.08 (m, 2 H, phenyl in Bz), 7.90–7.93 (m, 2 H,
phenyl in Bz), 7.73 (s, 1 H, H-6), 7.58–7.66 (m, 2 H, phenyl
2,4-dioxo-3,4-dihydropyrimidin-1(2H)-
yl)tetrahydroselenophen-2-yl)methyl benzoate (18b)
0
in Bz), 7.46–7.50 (m, 4 H, phenyl in Bz, H-1 ), 6.57 (t, J =
0
0
6
.8 Hz, 1 H, H-4 ), 4.71 (dd, J = 8.0, 11.2 Hz, 1 H, H-5 ),
0
To a solution of 16 (0.23 g, 0.84 mmol) in pyridine
(
4.60 (dd, J = 6.8, 11.6 Hz, 1 H, H-5 ), 2.46–2.51 (m, 1 H,
0 0 0 0
12 mL) was dropwise added benzoyl chloride (0.48 mL,
H-2 ), 2.22–2.30 (m, 3 H, H-2 , H-3 , H-3 ), 1.93 (s, 3 H, H-
1
3
4
.20 mmol) under N (g). After heating at 70 °C (bath
7); C NMR (100 MHz, CDCl ) d 172.0, 169.0, 166.5,
2
3
temperature) with stirring for 15 h, the reaction mixture
was evaporated and the residue was purified by column
chromatography (silica gel, hexane/EtOAc, 3/1) to give b-
162.8, 149.7, 137.1, 135.2, 133.9, 133.6, 131.7, 130.7,
130.4, 129.9, 129.8, 129.3, 128.8, 128.7, 111.7, 67.3, 58.6,
?
44.8, 37.5, 33.0, 12.9; LRMS (FAB) m/z 497 [M?H] ;
123

J. Yu et al.
2
D
3
[
a] = ? 55.36 (c 6.34, CH OH); Calcd for C H N
(100 MHz, CD OD) d 167.4, 158.5, 144.5, 96.6, 67.3,
3
24 22 2-
3
?
59.7, 50.0, 38.8, 34.0; LRMS (FAB) m/z 276 [M?H] ;
O Se: C, 57.95; H, 4.46; N, 5.63. Found: C, 57.86; H, 4.58;
5
2
D
3
N, 5.43; For: a-Isomer (19b): UV k
54.0 nm; H NMR (400 MHz, CDCl ) d 8.03–8.06 (m, 2
(CH OH)
3
[a] = - 248.24 (c 0.28, CH OH); Calcd for C H N
max
3
9 13 3-
1
2
O Se: C, 39.43; H, 4.78; N, 15.33. Found: C, 39.83; H,
2
3
H, phenyl in Bz), 7.91–7.93 (m, 2 H, phenyl in Bz),
4.98; N, 14.89.
7
.57–7.67 (m, 3 H, phenyl in Bz, H-6), 7.44–7.51 (m, 4 H,
0
phenyl in Bz), 6.63 (t, J = 6.8 Hz, 1 H, H-1 ), 4.58–4.62 (m,
0 0 0
1-((2S,5R)-5-(Hydroxymethyl)
tetrahydroselenophen-2-yl)pyrimidine-2,4(1H,3H)-
dione (3)
1
H, H-4 ), 4.34–4.42 (m, 2 H, H-5 , H-5 ), 2.60-2.64 (m, 1
0
0
0
H, H-2 ), 2.40–2.45 (m, 2 H, H-2 , H-3 ), 2.10–2.17 (m, 1
13
H, H-3 ), 1.99 (s, 3 H, H-7); C NMR (100 MHz, CDCl3)
0
d 169.0, 166.2, 162.8, 149.6, 137.1, 135.3, 133.5, 131.7,
The solution of 18a (0.38 g, 0.79 mmol) in methanolic
ammonia (5 mL) was stirred at room temperature for 15 h.
The reaction mixture was evaporated and the residue was
purified by column chromatography (silica gel, CH Cl /
1
3
30.7, 129.8, 129.4, 128.7, 111.7, 67.9, 58.1, 45.0, 38.7,
23
?
3.8, 13.0; LRMS (FAB) m/z 497 [M?H] ; [a]
=
D
-
97.98 (c 0.79, CH OH); Calcd for C H N O Se: C,
3 24 22 2 5
2
2
5
7.95; H, 4.46; N, 5.63. Found: C, 57.78; H, 4.34; N, 5.78.
CH OH, 30/1) to give 3 (0.19 g, 90%) as a white solid: mp
3
1
66.5-168.6 °C (from CH OH/ ether); UV k
(CH OH)
max 3
3
1
4-Amino-1-((2S,5R)-5-(hydroxymethyl)
tetrahydroselenophen-2-yl)pyrimidin-2(1H)-one (2)
266.5 nm; H NMR (400 MHz, CD OD) d 8.13 (d, J =
3
0
8.0 Hz, 1 H, H-6), 6.42 (t, J = 6.0 Hz, 1 H, H-1 ), 5.74 (d,
0
0
J = 8.0 Hz, 1 H, H-5), 3.84–3.93 (m, 2 H, H-5 , H-5 ), 3.76
0
0
To a solution of b-isomer 12 (0.46 g, 0.74 mmol) in
anhydrous THF (46 mL) was dropwise added tetra-n-
butylammonium fluoride (1.11 mL, 1 M in THF) under N2
(dd, J = 5.6, 10.4 Hz, 1 H, H-4 ), 2.31–2.37 (m, 2 H, H-2 ,
0
0
0
H-2 ), 2.19–2.24 (m, 1 H, H-3 ), 2.08–2.11 (m, 1 H, H-3 );
1
3
C NMR (100 MHz, CD OD) d 166.2, 152.5, 144.3,
3
(
g). After stirring at room temperature for 0.5 h, the reac-
102.8, 66.7, 59.4, 50.6, 38.5, 33.7; LRMS (FAB) m/z 276
?
23
[M?H] ; [a]D = ? 96.20 (c 0.37, CH OH); Calcd for
tion mixture was evaporated. To this residue, methanolic
ammonia (5 mL) was added and stirred at room tempera-
ture for 15 h. The reaction mixture was evaporated and the
residue was purified by column chromatography (silica gel,
CH Cl /CH OH, 30/1) to give 2 (0.17 g, 83%) as a white
3
C H N O Se: C, 39.28; H, 4.40; N, 10.18. Found: C,
9 12 2 3
39.48; H, 4.84; N, 9.98.
1-((2R,5R)-5-(Hydroxymethyl)tetrahydroselenophen-2-
2
2
3
solid: mp 143.0–146.3 °C (from CH OH/ether); UV k
yl)pyrimidine-2,4(1H,3H)-dione (3a)
3
max
1
(
CH OH) 277.0 nm; H NMR (400 MHz, CD OD) d 8.14
3
3
0
(
d, J = 7.6 Hz, 1 H, H-6), 6.45 (t, J = 5.6 Hz, 1 H, H-1 ),
Compound 18b (175 mg, 0.362 mmol) was converted to
compound 3a (92 mg, 92%) using a similar procedure to
that used in the preparation of compound 3; white solid; mp
0
5
5
.92 (d, J = 7.6 Hz, 1 H, H-5), 3.83–3.92 (m, 2 H, H-5 , H-
0
0
), 3.75 (dd, J = 6.0, 10.4 Hz, 1 H, H-4 ), 2.30–2.36 (m, 2
0
0
0
H, H-2 , H-2 ), 2.20–2.26 (m, 1 H, H-3 ), 2.04–2.07 (m, 1
13
H, H-3 ); C NMR (100 MHz, CD OD) d 167.5, 158.7,
188.3–190.2 °C (from CH OH/ether); UV k
(CH OH)
max 3
3
0
1
266.5 nm; H NMR (400 MHz, CD OD) d 8.03 (d, J =
3
3
0
1
44.5, 96.3, 66.8, 60.5, 50.3, 38.7, 33.7; LRMS (FAB) m/z
23
8.4 Hz, 1 H, H-6), 6.46 (t, J = 6.8 Hz, 1 H, H-1 ), 5.75 (d,
0
?
2
76 [M?H] ; [a]D = ? 188.79 (c 0.11, CH OH); Calcd
J = 7.6 Hz, 1 H, H-5), 4.08–4.14 (m, 1 H, H-4 ), 3.79 (dd,
0
3
for C H N O Se: C, 39.43; H, 4.78; N, 15.33. Found: C,
9 13 3 2
J = 6.8, 10.8 Hz, 1 H, H-5 ), 3.60 (dd, J = 7.2, 11.2 Hz, 1
0 0
3
9.87; H, 4.98; N, 15.18.
H, H-5 ), 2.43–2.51 (m, 1 H, H-2 ), 2.27–2.35 (m, 1 H, H-
0
0 0
13
), 2.17–2.25 (m, 1 H, H-3 ), 1.91–2.00 (m, 1 H, H-3 ); C
2
4
-Amino-1-((2R,5R)-5-(hydroxymethyl)
NMR (100 MHz, CD OD) d 166.2, 152.5, 144.3, 103.1,
3
tetrahydroselenophen-2-yl)pyrimidin-2(1H)-one (2a)
67.3, 58.6, 50.5, 38.8, 34.2; LRMS (FAB) m/z 276
23
?
[
M?H] ; [a]D = - 167.94 (c 0.57, CH OH); Calcd for
3
Compound 13 (0.46 g, 0.746 mmol) was converted to
compound 2a (173 mg, 85%) using a similar procedure to
that used in the preparation of compound 2; Yield = 85%;
C H N O Se: C, 39.28; H, 4.40; N, 10.18. Found: C,
9 12 2 3
39.48; H, 4.33; N, 10.40.
white solid; mp 203.7–205.8 °C (from CH OH/ether); UV
1-((2S,5R)-5-(Hydroxymethyl)tetrahydroselenophen-2-yl)-
3
1
kmax (CH OH) 277.0 nm; H NMR (400 MHz, CD OD) d
5-methylpyrimidine-2,4(1H,3H)-dione (4)
3
3
8
1
4
1
.04 (d, J = 7.6 Hz, 1 H, H-6), 6.49 (t, J = 6.4 Hz, 1 H, H-
0
), 5.94 (d, J = 7.6 Hz, 1 H, H-5), 4.04–4.10 (m, 1 H, H-
0
Compound 19a (193 mg, 0.388 mmol) was converted to
compound 4 (95 mg, 85%) using a similar procedure to
that used in the preparation of compound 3; white solid; mp
0
), 3.78 (dd, J = 6.8, 10.8 Hz, 1 H, H-5 ), 3.60 (dd, J = 7.2,
0
0
1.2 Hz, 1 H, H-5 ), 2.42–2.50 (m, 1 H, H-2 ), 2.15–2.32
13
m, 2 H, H-2 , H-3 ), 1.94–2.02 (m, 1 H, H-3 ); C NMR
0
0
0
(
147.7–149.9 °C (from CH OH/ether); UV k
(CH OH)
max 3
3
1
23

0
0
0
0
Synthesis and anti-HIV activity of L-2 ,3 -Dideoxy-4 -selenonucleosides (L-4 -Se-ddNs)
1
2
6
71.0 nm; H NMR (400 MHz, CD OD) d 7.94 (s, 1 H, H-
50%. The cytotoxic concentration is expressed as the CC50,
which is the concentration of the compound that killed 50%
3
0
0
), 6.43 (t, J = 6.4 Hz, 1 H, H-1 ), 3.84–3.93 (m, 2 H, H-4 ,
0
0
0
0
H-5 ), 3.77 (dd, J = 5.6, 10.4 Hz, 1 H, H-5 ), 2.30–2.35 (m,
0 0 0 0
of the mock-infected cells. 2 ,3 -Dideoxycytidine (ddC)
(Sigma) and azidothymidine (AZT) (Sigma) were used as
references in the anti-HIV tests. All compounds were dis-
solved in 100% dimethyl sulfoxide (DMSO) at a stock con-
centration of 20 mg/mL.
2
H, H-2 , H-2 ), 2.13–2.20 (m, 2 H, H-3 , H-3 ), 1.90 (s, 3
1
3
H, H-7); C NMR (100 MHz, CD OD) d 166.4, 152.7,
3
1
39.8, 111.7, 66.6, 59.2, 50.5, 38.4, 33.7, 12.6; LRMS
?
FAB) m/z 289 [M?H] ; [a]D = ? 67.83 (c 0.31, CH3-
OH); Calcd for C H N O Se: C, 41.53; H, 4.88; N, 9.69.
23
(
1
0 14 2 3
Found: C, 41.66; H, 4.84; N, 9.54.
X-ray structure determination
1
5
-((2R,5R)-5-(Hydroxymethyl)tetrahydroselenophen-2-yl)-
A suitable crystal of L-b-Se-ddC (2) was selected
and determined on a SuperNova, Dual, Cu at home/near,
AtlasS2 diffractometer. The crystal was kept at 294.8(7) K
during data collection. Using Olex2 (Dolomanov et al.
2009), the structure was solved with the ShelXT (Sheldrick
2015a, b) structure solution program using Intrinsic Phas-
ing and refined with the ShelXL (Sheldrick 2015a, b)
refinement package using Least Squares minimization.
Crystal Data for C H N O Se (M = 274.18 g/mol):
-methylpyrimidine-2,4(1H,3H)-dione (4a)
Compound 19b (202 mg, 0.406 mmol) was converted to
compound 4a (103 mg, 88%) using a similar procedure to
that used in the preparation of compound 3; white solid; mp
2
2
6
3
1
10.2–215.3 °C (from CH OH/ ether); UV k
70.5 nm; H NMR (400 MHz, CD OD) d 7.81 (s, 1 H, H-
), 6.48 (t, J = 6.8 Hz, 1 H, H-1 ), 4.10–4.15 (m, 1 H, H-4 ),
0
(CH OH)
max 3
3
1
3
0
0
9
13 3 2
.80 (dd, J = 6.8, 12.8 Hz, 1 H, H-5 ), 3.61 (dd, J = 7.6,
0
orthorhombic,
space
group
P2 2 2 (no.
1
19), a =
1 1
0
˚
9.2920(7) A, b = 10.9925(9) A, c = 11.3141(13) A, V =
˚
˚
1.2 Hz, 1 H, H-5 ), 2.43-2.50 (m, 1 H, H-2 ), 2.31–2.39
0
0
˚
3
(
m, 1 H, H-2 ), 2.17–2.26 (m, 1 H, H-3 ), 1.85–1.94 (m, 4
13
1155.65(18) A , Z = 4, T = 294.8(7) K, l(MoKa) =
0
-1
3
H, H-3 , H-7); C NMR (100 MHz, CD OD) d 139.6,
3.235 mm , Dcalc = 1.576 g/cm , 9541 reflections mea-
sured (5.166° B 2H B 59.404°), 2825 unique (Rint = 0.0391,
Rsigma = 0.0391) which were used in all calculations. The
final R was 0.0326 (I [ 2r(I)) and wR was 0.0771 (all
3
1
12.1, 67.4, 58.2, 50.6, 38.7, 34.4, 12.6; LRMS (FAB) m/z
?
23
89 [M?H] ; [a]D = - 131.61 (c 0.37, CH OH); Calcd
2
3
for C H N O Se: C, 41.53; H, 4.88; N, 9.69. Found: C,
3
1
0
14
2
1
2
4
1.91; H, 4.99; N, 9.48.
data). Further details of the crystal structure investiga-
tion(s) may be obtained from the Cambridge Crystallographic
Data Centre (CCDC, 12 Union Road, Cambridge, CB2 1EZ
Anti-HIV-1 activity
(UK); Tel.: (?44)1223-336-408, fax: (?44)1223-336-033,
Anti-HIV-1 assay was performed as described previously
e-mail: deposit@ccdc.cam.ac.uk) on quoting the Depository
No. CSD-1862312.
(Singh et al. 2016). HIV-1 (HTLV-IIIB strain) was amplified
in MT-4 (HTLV-1-infected human T lymphocytes) cells and
grown in RPMI 1640 medium supplemented with 10% FBS
and 4 lg/mL gentamycin. This medium was used for making
dilutions of the drugs and maintenance of the cultures during
the assays. Aliquots of the virus stocks were stored as culture
supernatants at - 70 °C until used. The virus-induced-CPE
inhibition assay was used to measure the anti-HIV activity.
Log-phase MT-4 cells were plated and infected with the virus
at a multiplicity of infection of 20 to 100 CCID50 (50% cell
culture inhibitory dose) per well. The cells were immediately
resuspended in RPMI 1640 plus 10% FBS at a concentration
of 105 cells/mL. Aliquots of 100 lL of the resuspended cells
were placed in the wells of a 96-well plate containing 100 lL
of twofold-concentrated test samples. After 5 days of incu-
bation at 37 °C, the cells were observed microscopically, and
cell viability was quantified using the MTT assay (Mosmann
Results and discussion
Our synthetic strategy to the final nucleosides 2–4 is to
synthesize the glycosyl donor from the chiral template and
then to condense it with silylated pyrimidine bases under
the Pummerer rearrangement conditions, using the same
procedure used in the preparation of the corresponding D-
nucleosides (Jeong et al. 2008a, b). Firstly, the glycosyl
donor 11 was synthesized from L-glutamic acid, as shown
in Scheme 1.
Diazotization of L-glutamic acid with sodium nitrite
(NaNO ) in the presence of c-H SO yielded the c-lactone
2
2
4
5 as a single stereoisomer (Wrona et al. 2010). Reduction
of the carboxylic acid of 5 with borane-dimethylsulfide
complex afforded the primary alcohol 6 (Wrona et al.
2010). The primary alcohol of 6 was protected with
TBDPS group to give lactone 7, which was reduced with
1983; Pauwels et al. 1988), which is based on the mito-
chondrial reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide. The effective antiviral con-
centration was expressed as the EC , which is the concen-
LiBH to yield the diol 8. Diol 8 was dimesylated with
4
50
tration of compound required to inhibit virus-induced CPE by
MsCl to give 9, which was treated with selenium powder in
123

J. Yu et al.
Scheme 1 Synthesis of the
glycosyl donor 11
the presence of NaBH to give 4-selenosugar 10 with L-
4
n-butylammonium fluoride (TBAF) followed by further
treatment with methanolic ammonia afforded the L-b-Se-
ddC (2) and its L-a-Se-isomer 2a, respectively. The struc-
ture of anomers 2 and 2a were confirmed from their
spectral features and comparison with the spectral data of
configuration. Oxidation of 10 with mCPBA afforded the
L-glycosyl donor 11, which is the condensation substrate
for Pummerer rearrangement conditions.
The L-glycosyl donor 11 was condensed with silylated
N -benzoylcytosine in the presence of trimethylsilyl tri-
4
1
their enantiomers D-Se-ddC (Jeong et al. 2008a, b). The H
fluoromethanesulfonate (TMSOTf) and triethylamine
NMR spectrum of L-b-Se-ddC 2 and L-a-Se-ddC 2a were
identical with those of D-b-Se-ddC and D-a-Se-ddC,
respectively.
(
Et N) to give the L-b-isomer 12 and L-a-isomer 13
3
(
Scheme 2) (a:b = 1:1). Treatment of 12 and 13 with tetra-
Scheme 2 Synthesis of L-b-Se-
ddC (2) and its L-a-isomer 2a
1
23

0
0
0
0
Synthesis and anti-HIV activity of L-2 ,3 -Dideoxy-4 -selenonucleosides (L-4 -Se-ddNs)
Scheme 3 Synthesis of L-b-Se-
ddU (3) and L-b-Se-ddT (4) and
their L-a-isomers 3a and 4a
Next, the L-glycosyl donor 11 was condensed with
silylated uracil and thymine under the same conditions to
give 14 and 15, respectively as inseparable a/b-mixtures
converted into the corresponding triphosphates by cellular
kinases, maybe due to steric repulsion between bulky
selenium atom and cellular kinase (Sahu et al. 2014, 2015).
0
(
Scheme 3). The removal of TBDPS group of 14 and 15
The conformation of a representative synthesized 4 -
with TBAF yielded 16 and 17, respectively, but they were
still obtained as inseparable a/b-mixtures. For the isolation
of inseparable a/b-mixtures, compound 16 was benzoy-
seleno compound, L-b-Se-ddC (2) was analyzed using
spectral data and X-ray crystallography. The X-ray crystal
structure of 2 was obtained as illustrated in Fig. 2. Com-
3
0
0
lated to give the N -benzoates, which were separated by
pound 2 exhibited a 2 -endo/3 -exo (South) conformation,
which is the same of that of L-ddC (Birnbaum 1988). Thus,
silica gel column chromatography to yield the b-benzoate
0
0
1
8a and the a-benzoate 18b. Similarly, compound 17 was
as in the case of 4 -Se-d4T, one-carbon homologation of 4 -
Se-ddNs might reduce steric repulsion between bulky
selenium atom and cellular kinase, and restore the antiviral
activity by phosphorylating them by cellular kinases.
converted to the b-benzoate 19a and the a-benzoate 19b.
The b-anomers 18a and 19a were treated with methanolic
ammonia to afford the final L-b-Se-ddU (3) and L-b-Se-ddT
(
4), respectively. Similarly, the a-anomers 18b and 19b
were converted the corresponding L-a-isomers 3a and 4a,
respectively.
Conclusions
All final compounds 2–4 and 2a–4a were assayed for
their anti-HIV-1 activities in MT-4 cells. Unfortunately,
none of the synthesized compounds did show any antiviral
activity up to 100 lM, indicating that they are not
All final compounds 2–4 and 2a–4a were assayed for their
anti-HIV-1 activity in MT-4 cells. Disappointedly, all
synthesized compounds showed neither anti-HIV-1 activity
123

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Acknowledgements This research was supported by grants from
Mid-career Research Program (2016R1A2B3010164) and Basic Sci-
ence Research Program (2018R1D1A1A02085459) of the National
Research Foundation (NRF), Korea. Antiviral assay by C.-K. Lee
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Sahu PK, Naik S, Yu J, Jeong LS (2015) 4 -Selenonucleosides as
next-generation nucleosides. Eur J Org Chem 28:6115–6124
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Acta Cryst C71:3–8
Compliance with ethical standards
Singh S, Gajulapati V, Kim M, Goo JI, Lee JK, Lee K, Lee CK, Jeong
LS, Choi Y (2016) A divergent approach for the synthesis of
0
Conflict of interest The authors declare no conflict of interest.
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