Synthesis and anti-HIV activity of C4-modified pyrimidine nucleosides

Article abstract of DOI:10.1016/S0014-827X(98)00107-4

One-pot syntheses provided a series of triazole- and pentafluorophenyloxy-substituted pyrimidine nucleosides. Most of the compounds in the series displayed anti-HIV activities but none as potent as AZT 2. 1-(β-D-Erythro-pentofuranosyl)-4-pentafluorophenyloxy-2(1H)-pyrimidinone 14 was the most potent and the most selective compound in the series with EC₅₀ = 1.6 μM.

Full text of DOI:10.1016/S0014-827X(98)00107-4

Il Farmaco 54 (1999) 83–89
Synthesis and anti-HIV activity of C4-modified pyrimidine
nucleosides
Mark P. Wallis a, Naheed Mahmood b, William Fraser a,*
a Pharmaceutical Sciences Research Institute, Aston Uni6ersity, Aston Triangle, Birmingham B4 7ET, UK
b Department of Immunology, Rayne Institute, 123 Cold Harbour Lane, London SE5 9NU, UK
Received 21 September 1998; accepted 7 December 1998
Abstract
One-pot syntheses provided a series of triazole- and pentafluorophenyloxy-substituted pyrimidine nucleosides. Most of the
-Erythro-pentofuranosyl)-4-pen-
compounds in the series displayed anti-HIV activities but none as potent as AZT 2. 1-(b-
D
tafluorophenyloxy-2(1H)-pyrimidinone 14 was the most potent and the most selective compound in the series with EC50=1.6 mM.
© 1999 Elsevier Science S.A. All rights reserved.
Keywords: Anti-HIV; Reverse transcriptase; Nucleoside; Pyrimidine; ATAZT; Triazole
1. Introduction
We previously reported on the structure of the
pyrimidine nucleoside ATAZT [9] 1 (Fig. 1). This com-
pound 1 represents an acylated, C4-triazole derivative
of the anti-HIV drug zidovudine (AZT) 2. Although the
original synthesis of ATAZT 1 had been reported in the
literature [10], the compound remained uncharacterised
both structurally and biologically. Our preliminary
evaluation of ATAZT 1 revealed promising anti-HIV
activity, providing a lead compound for development
through the synthesis of analogues. In attempts to
improve antiviral activity, a series of derivatives 9–18
were prepared (Scheme 1) by varying the substituents at
positions C4 and C5 (conventional numbering [11]) of
the pyrimidine ring, and at positions O2%, O3% and O5%
of the sugar ring (Table 1).
In this communication we report on the synthesis
and biological evaluation of a series of C4-substituted
pyrimidine nucleosides. Pyrimidine and purine nu-
cleosides still comprise a significant proportion of mar-
keted drugs against the human immunodeficiency virus
(HIV). Emergence of drug-resistant virus [1] presents a
serious drawback to the sustained clinical use of nu-
cleoside [2] and non-nucleoside [3] inhibitors of the viral
reverse transcriptase (RT) [4]. Inhibition of the viral
protease (PR) [5] is achievable using peptidic [6] and
cyclic non-peptide compounds [7] with every expecta-
tion that recent successes will be augmented by discov-
eries of new PR inhibitors. Clinical trials seek to
demonstrate the value of combining nucleosides and
PR inhibitors to maintain reduction of viral load and
increase in CD4+ lymphocytes in HIV-infected pa-
tients [8]. Thus, there remains an important role for
pyrimidine nucleosides and their analogues in HIV
chemotherapy encouraging searches for potential, new
antiviral nucleosides.
* Corresponding author. Tel.: +44-121-3593611; fax: +44-121-
3590733.
E-mail address: w.fraser@aston.ac.uk (W. Fraser)
Fig. 1. Structures of ATAZT 1 and AZT 2.
0014-827X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0014-827X(98)00107-4

84
M.P. Wallis et al. / Il Farmaco 54 (1999) 83–89
Scheme 1. Reagents and conditions: i, (CF3CO)2O; ii, pyridine; iii, 1,2,4-1H-triazole; iv, ClC6H4P(O)Cl2; v, PfpOH; vi, (CH3)3SiCl.
presence of pyridine and PfpOH, was successful. Com-
pound 18 was isolated in 62% yield although attempts
to prepare its C4-triazolyl analogue failed using either
the transient trifluroacetate or trimethylsilyl protection
methods. Successful preparation of C5-methylated ana-
logues of 9 and 13 from 6 was not achievable using the
methods detailed here. The lability of the triazole and
PfpO substitutents in compounds 12 and 16 precluded
selective de-acylation, frustrating attempts to prepare
C5-methylated analogues of 9 and 13 from these pro-
tected precursors.
2. Chemistry
One-pot syntheses provided a series of C4-modified
nucleosides from 2%-deoxyuridine 3, uridine 5,
thymidine 6, AZT 2 and O-acetates 4, 7 and 8 (Scheme
1). Treatment of 2%-deoxyuridine 3 with trifluoroacetic
anhydride [12–14] in pyridine facilitated transient pro-
tection at O5% and O3%. Subsequent addition of 1,2,4-
1H-triazole to the same reaction pot attached triazole
to 3, via a transient C4-pyridinium intermediate [12].
The C4-triazolyl nucleoside 9 was isolated in 79% yield
after de-acylation of the sugar hydroxyl groups on flash
chromatographic purification of the reaction product.
Under the same reaction conditions but with pen-
tafluorophenol (PfpOH) instead of triazole, 3 gave
PfpO-substituted nucleoside 13 in comparable yield
(78%). Although product yields for the ribose ana-
logues were lower than those for the corresponding
2%-deoxyribose analogues, the presence of the additional
hydroxyl group at the C2% position did not seriously
impede the progress of reactions. Thus, uridine 5 gave
C4-substituted ribose nucleosides 10 (56%) and 14
(59%). X-ray crystal structure analysis of 13 and 14
provided the first example of isomorphous ribose and
2%-deoxyribose nucleosides with the same pyrimidine
base [15].
Acetylated derivatives 11, 12, 15 and 16 were pre-
pared in adequate yields from protected nucleosides 4
and 7, using 4-chlorophenyl phosphodichloridate [16]
and triazole or PfpOH in pyridine. Reaction of 5%-O-
acetyl-AZT [10] 8 gave ATAZT 1 (88% yield). Simi-
larly, reaction of 8 with PfpOH in place of triazole gave
17 (62% yield). Attempted reaction of AZT 2 with
trifluoroacetic anhydride in the presence of PfpOH and
pyridine failed to yield 18. However, transient protec-
tion of 2 as its 5%-O-trimethylsilyl ether, and activation
at C4 using 4-chlorophenyl phosphodichloridate in the
3. Biological results and discussion
With the exception of triazole derivative 9 all of the
compounds evaluated displayed some activity against
HIV-1 (Table 1). None of the compounds was as potent
as AZT 2 against HIV-1 in C8166 cells [17] and none
without cytotoxicity. Replacement of the triazole ring
of 9 by PfpO imparts weak antiviral activity to 13.
However, compound 10, the ribose analogue of 9, did
display moderate antiviral activity and replacement of
its triazole group by PfpO in 14 provided the most
selective compound of the series (EC50=1.6 mM),
equipotent with ATAZT 1. Replacement of the triazole
ring in ATAZT 1 by PfpO resulted in a marginal loss of
antiviral activity with 17 having EC50=2.0 mM but
with no improvement in cytotoxicity. Removal of the
acetyl group from 17 resulted in a substantial loss of
antiviral potency. Although their selectivity was still
poor, protected triazole- and PfpO-substituted nu-
cleosides 11 and 15 did show improved antiviral activi-
ties compared to their unprotected analogues 9 and 13,
as did derivatives 12 and 16 compared to their
demethylated analogues.

M.P. Wallis et al. / Il Farmaco 54 (1999) 83–89
85
Table 1
Antiviral activity of C4-modified pyrimidine nucleosides against HIV-1 in C1866 cells
R4
R5
R5%
R3%
R2%
EC50 (mM)a
TC50 (mM)b
9
10
11
12
1
13
14
15
16
17
18
AZT
1,2,4-Triazole
1,2,4-Triazole
1,2,4-Triazole
1,2,4-Triazole
1,2,4-Triazole
C6F5O
C6F5O
C6F5O
C6F5O
C6F5O
H
H
H
Me
Me
H
H
H
H
H
Ac
Ac
Ac
H
OH
OH
OAc
OAc
N3
OH
OH
OAc
OAc
N3
H
OH
H
H
H
H
OH
H
H
H
\1000
100
400
40
1.6
400
1.6
100
\80
2
400
0.016
\1000
400
\1000
80
80
\1000
200
H
Ac
Ac
Ac
H
100
80
80
400
Me
Me
Me
C6F5O
N3
H
\1000
a EC50 represents the concentration of compound which reduced HIV-1 gp120 formation by 50% in infected cell cultures.
b TC50 represents the concentration of compound which reduced cell growth by 50%.
4. Conclusions
using VG Quatro II or AutoSpec instruments. IR spec-
tra were recorded on a Mattson Galaxy 2020 FT-IR
instrument and UV spectra were recorded on Varian-
Cary 1E UV–Vis or Unicam PU8730 spectrophotome-
ters. The UV spectra of compounds 1, and 9–12 were
nearly identical as were the UV spectra for compounds
13–18, therefore only data for two representative com-
pounds (9 and 13) are given. Melting points were
determined with a Gallenkamp electrothermal digital
apparatus and are uncorrected. Flash column chro-
matography [18] was performed using Sorbsil C60 silica
gel and TLC was performed using plastic-backed
Kieselgel 60 silica gel plates containing a fluorescent
indicator and visualised under UV (254 nm) and with
acidic anisaldehyde solution. Elemental analyses were
performed by Butterworth Laboratories (Middlesex)
and the results from C, H and N analyses were within
90.4% of calculated values.
The series of C4-modified pyrimidine nucleosides de-
scribed here possessed only moderate antiviral activity
compared to AZT 2 with no substantial improvement
in potency compared with the lead compound ATAZT
1. Replacement of triazole at C4 by PfpO neither
compromised nor provided substantial improvements in
antiviral potency, although acylation at C5% provided a
marginal improvement in antiviral activity. The cyto-
toxocity and the lack of pronounced antiviral potency
in the compounds evaluated did not warrant detailed
investigations of their precise biological modes of ac-
tion at this stage.
5. Experimental
5.1. Chemistry
5.1.1. 1-(2-Deoxy-i-D-erythro-pentofuranosyl)-4-
NMR spectra were recorded on a Bruker AC-250
(1,2,4-triazol-1-yl)-2(1H)-pyrimidinone (9)
1
spectrometer at H (250.1 MHz), 13C (62.9 MHz) and
To 2%-deoxyuridine 3 (1.00 g, 4.40 mmol) in dry
pyridine (40 ml) under Ar at 0°C, trifluoroacetic anhy-
dride (1.86 ml, 13.16 mmol) was added and the solution
stirred at room temperature (r.t.) for 24 h after which
time 1,2,4-1H-triazole (3.03 g, 43.86 mmol) in pyridine
(5 ml) was added and the mixture stirred at r.t. for a
further 72 h. The product solution was then concen-
trated under vacuum. Flash column chromatography,
19F (235.3 MHz) with positive chemical shifts downfield
of TMS (1H and 13C) and negative chemical shifts
upfield of CF3CCl3 (19F). Proton and carbon assign-
ments are reported using conventional numbering [11].
The 19F NMR spectra of compounds 13–18 were
nearly identical, therefore only data for a representative
compound (13) are given. Mass spectra were recorded

86
M.P. Wallis et al. / Il Farmaco 54 (1999) 83–89
eluting with CH2Cl2–CH3OH 4:1, gave 9 (904 mg, 79%)
as a colourless solid; m.p.\300°C; TLC (CH2Cl2–
CH3OH 4:1): Rf 0.76.
mmol) and 1,2,4-1H-triazole (3.10 g, 43.90 mmol) in
pyridine (10 ml). Flash column chromatography, eluting
with CH2Cl2–CH3OH 4:1 followed by recrystallization
from DMF, gave 10 (684 mg, 56%) as colourless crystals;
m.p. 216°C; TLC (CH2Cl2–CH3OH 4:1): Rf 0.45.
IR (KBr disc): wmax 3357, 3300, 3118, 3095, 2933, 1697,
UV (95% EtOH): umax 249 nm (8200), 315 nm (4900).
IR (KBr disc): wmax 3303, 3145, 3106, 2951, 2900, 1660,
1550, 1515, 1425, 1282, 1184 cm−1
.
1H NMR [(CD3)2SO]: l 2.10 (m, 1H, 2%-CH), 2.38 (m,
1H, 2%-CH), 3.62 (m, 2H, 5%-CH2), 3.91 (m, 1H, 4%-CH),
4.23 (m, 1H, 3%-CH), 5.13 (t, 1H, J 5.1 Hz, 5%-OH), 5.31
(d, 1H, J 4.3 Hz, 3%-OH), 6.10 (t, 1H, J 6.0 Hz, 1%-CH),
6.96 (d, 1H, J 7.2 Hz, 5-CH), 8.38 (s, 1H, 3-CH), 8.69
(d, 1H, J 7.2 Hz, 6-CH), 9.41 ppm (s, 1H, 5-CH
(triazole)).
1630, 1562, 1523, 1417, 1285, 1107, 1068 cm−1
.
1H NMR [(CD3)2SO]: l 4.32 (m, 1H, 3%-CH), 4.34 (m,
1H, 4%-CH), 4.53 (m, 3H, 2%-CH, 5%-CH2), 5.41 (d, 1H,
J 6.0 Hz, 2%-OH), 5.72 (t, 1H, J 5.0 Hz, 5%-OH), 6.10 (d,
1H, J 4.5 Hz, 3%-OH), 6.31 (d, 1H, J 1.4 Hz, 1%-CH), 7.43
(d, 1H, J 7.3 Hz, 5-CH), 8.81 (s, 1H, 3-CH), 9.42 (d, 1H,
J 7.3 Hz, 6-CH), 9.85 ppm (s, 1H, 5-CH (triazole)).
13C NMR [(CD3)2SO]: l 58.6 (5%-CH2), 74.0 (2%-CH),
70.0 (3%-CH), 87.2 (1%-CH), 88.5 (4%-CH), 93.9 (5-CH),
142.9 (5-CH (triazole)), 147.5 (6-CH), 153.1 (4-C), 153.3
(3-CH), 157.8 ppm (2-CO).
13C NMR [(CD3)2SO]: l 41.2 (2%-CH2), 60.9 (5%-CH2),
69.8 (3%-CH), 87.4 (1%-CH), 88.5 (4%-CH), 93.8 (5-CH),
143.8 (5-CH (triazole)), 148.3 (6-CH), 153.8 (4-C), 154.3
(3-CH), 158.7 ppm (2-CO).
MS (FAB+): m/z (rel. int.) 302 (M+Na, 28%), 280
(M+H, 66%), 260 (24%), 164 (67%), 150 (32%), 121
(100%), 108 (79%), 105 (65%).
MS (FAB+): m/z (rel. int.) 318 (M+Na, 22%), 296
(M+H, 37%), 242 (20%), 165 (86%), 150 (49%), 115
(81%), 105 (100%).
HRMS Calc. for C11H14N5O5 (M+H): 296.099.
Found: 296.097.
HRMS Calc. for C11H14N5O4 (M+H): 280.105.
Found: 280.105.
The following compounds were prepared in a similar
manner:
5.1.4. 1-(i-D-Erythro-pentofuranosyl)-4-penta-
fluorophenyloxy-2(1H)-pyrimidinone (14)
5.1.2. 1-(2-Deoxy-i-D-erythro-pentofuranosyl)-4-
pentafluorophenyloxy-2(1H)-pyrimidinone (13)
From uridine 5 (2.0 g, 8.2 mmol), dry pyridine (30 ml),
trifluoroacetic anhydride (5.8 ml, 41.0 mmol) and PfpOH
(8.1 g, 43.9 mmol) in pyridine (20 ml). Flash column
chromatography, eluting with EtOAc–CH3OH (4:1),
followed by recrystallization from CH3OH gave 14 (1.98
g, 59%) as a colourless solid; m.p. 238°C; TLC (EtOAc–
CH3OH 4:1): Rf 0.53.
From 2%-deoxyuridine 3 (1.00 g, 4.40 mmol), anhy-
drous pyridine (40 ml), trifluoroacetic anhydride (2.5 ml,
17.5 mmol) and PfpOH (8.10 g, 43.90 mmol) in pyridine
(10 ml). Flash column chromatography, eluting with
EtOAc–CH3OH 9:1, gave 13 (1.35 g, 78%) as a colourless
solid; m.p. 176°C; TLC (EtOAc–CH3OH 9:1): Rf 0.50.
UV (95% EtOH): umax 286 nm (6730).
IR (KBr disc): wmax 3465, 3413, 3123, 2987, 2932, 1745,
1677, 1661, 1627, 1550, 1515, 1291, 1230, 1199, 1179
IR (KBr) wmax 3479, 3403, 3083, 2940, 1654, 1556,
cm−1
.
1450, 1295, 1114 cm−1
.
1H NMR [(CD3)2SO]: l 3.68 (m, 2H, 5%-CH2), 3.96 (m,
3H, 2%-CH, 3%-CH, 4%-CH), 5.18 (d, 1H, J 6.0 Hz, 2%-OH),
5.28 (t, 1H, J 5.0 Hz, 5%-OH), 5.57 (d, 1H, J 4.5 Hz,
3%-OH), 5.72 (d, 1H, J 1.6 Hz, 1%-CH), 6.60 (d, 1H, J 7.4
Hz, 5-CH), 8.70 ppm (d, 1H, J 7.4 Hz, 6-CH).
13C NMR [(CD3)2SO]: l 59.6 (5%-CH2), 74.5 (2%-CH),
68.4 (3%-CH), 84.3 (1%-CH), 90.6 (4%-CH), 92.7 (5-CH),
147.9 (6-CH), 153.7 (4-C), 168.5 ppm (2-CO).
MS (FAB+): m/z (rel. int.) 411 (M+H, 70%), 308
(17%), 297 (100%), 156 (15%), 121 (19%), 108 (10%).
HRMS Calc. for C15H12F5N2O6 (M+H): 411.062.
Found: 411.063.
1H NMR [(CD3)2SO]: l 2.07 (m, 1H, 2%-CH), 2.29 (m,
1H, 2%-CH), 3.62 (s, 2H, 5%-CH2), 3.88 (d, 1H, J 3.4 Hz,
4%-CH) 4.23 (s, 1H, 3%-CH), 5.14 (s, 1H, 5%-OH), 5.28 (s,
1H, 3%-OH), 6.06 (t, 1H, J 6.1 Hz, 1%-CH), 6.59 (d, 1H,
J 7.3 Hz, 5-CH), 8.59 ppm (d, 1H, J 7.3 Hz, 6-CH).
13C NMR [(CD3)2SO]: l 1.2 (2%-CH2), 61.0 (5%-CH2),
70.0 (3%-CH), 87.2 (1%-CH), 88.5 (4%-CH), 93.0 (5-CH),
148.0 (6-CH), 154.0 (4-C), 169.3 ppm (2-CO).
19F NMR [(CD3)2SO]: l −14.7 (t, 2F, J 20.2 Hz, meta
CF), −20.0 (t, 1F, J 21.2 Hz, para CF), −24.1 ppm (d,
2F, J 24.2 Hz, ortho CF).
MS (FAB+): m/z (rel. int.) 417 (M+Na, 15%), 395
(M+H, 22%), 305 (14%), 279 (100%).
5.1.5. 1-(3,5-Di-O-acetyl-2-deoxy-i-D-erythro-
pentofuranosyl)-4-(1,2,4-triazol-1-yl)-2(1H)-pyrimidi-
none (11) [11]
HRMS Calc. for C15H12F5N2O5 (M+H): 395.068.
Found: 395.067.
To a solution of 3%,5%-di-O-acetyl-2%-deoxyuridine 4
(3.08 g, 9.9 mmol) in anhydrous pyridine (100 ml)
under Ar at 0°C, 4-chlorophenyl phosphodichloridate
(3.20 ml, 19.7 mmol) was added with stirring. After 5
5.1.3. 1-(i-D-Erythro-pentofuranosyl-4-(1,2,4-tri-
azol-1-yl)-2(1H)-pyrimidinone (10)
From uridine 5 (1.01 g, 4.45 mmol), anhydrous
pyridine (50 ml), trifluoroacetic anhydride (3.1 ml, 22.3

M.P. Wallis et al. / Il Farmaco 54 (1999) 83–89
87
5.1.7. 1-(3,5-Di-O-acetyl-2-deoxy-i-
furanosyl)-5-methyl-4-(1,2,4-triazol-1-yl)-2(1H)-pyr-
imidinone (12)
From 3%,5%-di-O-acetylthymidine 7 (1.00 g, 3.09
mmol), anhydrous pyridine (50 ml), 4-chlorophenyl
phosphodichloridate (1.00 ml, 6.17 mmol), and 1,2,4-
1H-triazole (0.85 g, 12.30 mmol). Flash column chro-
matography, eluting with EtOAc, gave 12 (550 mg,
49%) as a colourless semi-solid; TLC (EtOAc): Rf
0.36.
D
-erythro-pento-
min 1,2,4-1H-triazole (2.70 g, 39.4 mmol) was added
and the mixture allowed to warm to r.t. After a further
72 h the product solution was concentrated under
vacuum and the residue dissolved in CH2Cl2 (600 ml),
extracted with water (3×300 ml), dried (MgSO4) and
the solvent evaporated. Flash column chromatography
eluting with EtOAc, followed by recrystallization from
EtOAc, gave 11 (1.89 g, 53%) as colourless crystals;
m.p. 151°C; TLC (EtOAc): Rf 0.17.
IR (KBr disc): wmax 3121, 1751, 1675, 1670, 1552,
1515, 1239, 1059 cm−1
.
IR (KBr disc): wmax 3465, 3104, 2933, 2902, 1745,
1679, 1525, 1238, 1068 cm−1
.
1H NMR [(CD3)2SO]: l 2.02 (s, 3H, CH3), 2.07 (s,
3H, CH3), 2.41 (m, 1H, 2%-CH), 2.61 (m, 1H, 2%-CH),
4.27 (d, 2H, J 4.4 Hz, 5%-CH2), 4.38 (m, 1H, 4%-CH),
5.21 (m, 1H, 3%-CH), 6.14 (t, 1H, J 6.7 Hz, 1%-CH), 7.04
(d, 1H, J 7.3 Hz, 5-CH), 8.41 (s, 1H, 3-CH), 8.45 (d,
1H, J 7.3 Hz, 6-CH), 9.44 ppm (s, 1H, 5-CH (triazole)).
13C NMR [(CD3)2SO]: l 22.1 (CH3), 22.3 (CH3), 38.9
(2%-CH2), 65.1 (5%-CH2), 75.6 (3%-CH), 84.0 (1%-CH), 89.2
(4%-CH), 95.6 (5-CH), 145.2 (5-CH (triazole)), 149.5
(6-CH), 155.0 (4-C), 155.6 (3-CH), 160.3 (2-CO), 171.5
(CO), 171.6 ppm (CO).
1H NMR [(CD3)2SO]: l 2.03 (s, 3H, CH3), 2.08
(s, 3H, CH3), 2.32 (s, 3H, 5-CH3), 2.49 (m, 2H, 2%-
CH2), 4.35 (m, 3H, 4%-CH, 5%-CH2), 5.22 (m, 1H,
3%-CH), 6.15 (t, 1H, J 6.5 Hz, 1%-CH), 8.25 (s,
1H, 6-CH), 8.39 (s, 1H, 3-CH), 9.33 ppm (s, 1H, 5-
CH).
13C NMR [(CD3)2SO]: l 16.5 (5-CH3), 21.0 (CH3),
21.2 (CH3), 37.8 (2%-CH2), 63.9 (5%-CH2), 74.4 (3%-CH),
82.5 (1%-CH), 87.8 (4%-CH), 105.3 (5-C), 145.8 (5-CH),
148.0 (6-CH), 153.4 (4-C), 153.9 (3-CH), 158.5 (2-
CO), 170.5 (CO), 170.6 ppm (CO).
MS (FAB+): m/z (rel. int.) 386 (M+Na, 10%), 364
(M+H, 63%), 201 (32%), 164 (100%), 81 (96%), 69
(90%).
The following compounds were prepared in a similar
manner:
MS (FAB+): m/z (rel. int.) 400 (M+Na, 48%),
378 (M+H, 89%), 201 (27%), 178 (100%).
HRMS Calc. for C16H20N5O6 (M+H): 378.141;
Found: 378.142.
5.1.8. 1-(3,5-Di-O-acetyl-2-deoxy-i-D-erythro-pento-
5.1.6. 1-(3,5-Di-O-acetyl-2-deoxy-i-D-erythro-pento-
furanosyl)-5-methyl-4-pentafluorophenyloxy-2(1H)-py-
rimidinone (16)
furanosyl)-4-pentafluorophenyloxy-2(1H)-pyrimidinone
(15)
From 3%,5%-di-O-acetylthymidine 7 (1.00 g, 3.09
mmol), anhydrous pyridine (40 ml), 4-chlorophenyl
phosphodichloridate (1.00 ml, 6.17 mmol) and PfpOH
(2.27 g, 12.30 mmol) in pyridine (10 ml). Flash
column chromatography, eluting with EtOAc–hexane
1:1, gave 16 (0.99 g, 67%) as a semi-solid; TLC
(EtOAc–hexane 1:1): Rf 0.55.
From 2%-deoxy-3%,5%-di-O-acetyl-2%-deoxyuridine
4
(1.00 g, 3.18 mmol), anhydrous pyridine (40 ml), 4-
chlorophenyl phosphodichloridate (0.99 ml, 6.37
mmol) and PfpOH (2.34 g, 12.73 mmol) in pyridine
(10 ml). Flash column chromatography, eluting with
EtOAc–hexane 4:1, gave 15 (0.93 g, 61%) as a
colourless semi-solid; TLC (EtOAc–hexane, 4:1): Rf
0.51.
IR (KBr disc): wmax 3123, 2987, 2932, 1739, 1666,
IR (KBr disc): wmax 3124, 2987, 2933, 1745, 1661,
1550, 1515, 1230, 1223, 1029 cm−1
.
1550, 1452, 1297, 1199, 1112, 1072 cm−1
.
1H NMR (CDCl3): l 2.16 (s, 6H, CH3), 2.20 (s,
3H, 5-CH3), 2.75 (dd, 1H, J 5.6, 2.2 Hz, 2%-CH), 2.81
(dd, 1H, J 6.6, 2.2 Hz, 2%-CH), 4.36 (m, 1H, 4%-CH),
4.41 (m, 2H, 5%-CH2), 5.22 (m, 1H, 3%-CH), 6.25 (t,
1H, J 5.6 Hz, 1%-CH) 7.86 ppm (s, 1H, 6-CH).
13C NMR [(CD3)2SO]: l 11.8 (5-CH3), 20.9 (CH3),
21.3 (CH3), 37.5 (2%-CH2), 63.9 (5%-CH2), 74.4 (3%-CH),
82.6 (1%-CH), 87.2 (4%-CH), 102.3 (5-C), 145.2 (6-CH),
153.7 (4-C), 168.0 (2-CO), 170.4 (CO), 170.6 ppm
(CO).
1H NMR [(CD3)2SO]: l 2.06 (s, 6H, CH3), 2.41 (m,
2H, 2%-CH2), 4.25 (m, 2H, 5%-CH2), 4.31 (m, 1H, 4%-
CH), 5.17 (m, 1H, 3%-CH), 6.07 (t, 1H, J 6.5 Hz,
1%-CH), 6.62 (d, 1H, J 7.3 Hz, 5-CH), 8.32 ppm (d,
1H, J 7.3 Hz, 6-CH).
13C NMR [(CD3)2SO]: l 20.6 (CH3), 20.8 (CH3),
37.3 (2%-CH2), 63.6 (5%-CH2), 74.1 (3%-CH), 82.4 (1%-
CH), 87.4 (4%-CH), 93.2 (5-CH), 147.7 (6-CH), 153.5
(4-C), 168.7 (2-CO) 170.1 (CO), 170.2 ppm (CO).
MS (FAB+): m/z (rel. int.) 501 (M+Na, 66%),
479 (M+H, 54%), 279 (100%), 201 (75%).
HRMS Calc. for C19H16F5N2O7 (M+H): 479.088.
Found: 479.088.
MS (FAB+): m/z (rel. int.) 515 (M+Na, 50%),
493 (M+H, 37%), 293 (100%), 201 (62%).
HRMS Calc. for C20H18F5N2O7 (M+H): 493.103.
Found: 493.105.

88
M.P. Wallis et al. / Il Farmaco 54 (1999) 83–89
5.1.9. 1-(5-O-Acetyl-3-azido-2,3-dideoxy-i-
pentofuranosyl)-5-methyl-4-(1,2,4-triazol-1-yl)-2
(1H)-pyrimidinone (1)
From 5%-O-acetyl-AZT [10] 8 (3.08 g, 9.90 mmol), dry
pyridine (50 ml), 4-chlorophenyl phosphodichloridate
(1.85 ml, 11.34 mmol) and 1,2,4-1H-triazole (2.70 g,
39.40 mmol). Flash column chromatography, eluting
with EtOAc, followed by recrystallization from EtOAc,
gave 1 (1.79 g, 88%) as colourless crystals; m.p. 137°C;
TLC (EtOAc): Rf 0.24.
D
-erythro-
to 0°C. 4-Chlorophenyl phosphodichloridate (0.76 ml,
4.68 mmol) was then added and after stirring for 15 min,
PfpOH (1.73 g, 9.36 mmol) in pyridine (10 ml) was added
and the mixture left to stir at r.t. After 24 h, water (50
ml) was added and the mixture stirred for 1 h at r.t. before
concentration under vacuum. Flash column chromatog-
raphy, eluting with EtOAc–hexane 7:1, followed by
recrystallization from EtOAc–CH3OH, gave 18 (502 mg,
62%) as colourless crystals; m.p. 181°C; TLC (EtOAc–
hexane 7:1): Rf 0.61.
IR (KBr disc): wmax 3126, 2970, 2112, 1730, 1662, 1625,
IR (KBr disc): wmax 3449, 2931, 2120, 1664, 1521, 1411,
1525, 1425, 1237, 977 cm−1
.
1330, 1112, 988, 778 cm−1
.
1H NMR [(CD3)2SO]: l 2.09 (s, 3H, CH3), 2.35 (s, 3H,
5-CH3), 2.59 (m, 2H, 2%-CH2), 4.19 (m, 1H, 3-CH), 4.39
(m, 3H, 4%-CH, 5%-CH2), 6.12 (t, 1H, J 5.6 Hz, 1%-CH),
8.23 (s, 1H, 6-CH), 8.40 (d, 1H, 3-CH), 9.35 ppm (s, 1H,
5-CH).
1H NMR [(CD3)2SO]: l 2.13 (s, 3H, 5-CH3), 2.42 (t,
2H, J 6.4 Hz, 2%-CH2), 3.70 (m, 2H, 5%-CH2), 3.91 (m, 1H,
4%-CH), 4.40 (q, 1H, J 6.7 Hz, 3%-CH), 5.40 (s, 1H, 5%-OH),
6.61 (t, 1H, J 4.3 Hz, 1%-CH), 8.42 ppm (s, 1H, 6-CH).
13C NMR [(CD3)2SO]: l 12.3 (5-CH3), 38.8 (2%-CH2),
59.2 (3%-CH), 60.4 (5%-CH2), 85.3 (1%-CH), 86.4 (4%-CH),
101.6 (5-C), 143.3 (6-CH), 153.7 (4-C), 167.9 ppm
(2-CO).
13C NMR [(CD3)2SO]: l 17.5 (CH3), 21.0 (5-CH3), 35.6
(2%-CH2), 60.0 (3%-CH), 63.5 (5%-CH2), 82.4 (1%-CH), 87.3
(4%-CH), 105.1 (5-C), 145.7 (5-CH), 148.0 (6-CH), 153.5
(4-C), 153.9 (3-CH), 158.4 (2-CO), 170.6 ppm (CO).
MS (FAB+): m/z (rel. int.) 383 (M+Na, 1%), 361
(M+H, 37%), 178 (100%), 135 (5%).
MS (FAB+): m/z (rel. int.) 434 (M+H, 27%), 319
(10%), 293 (100%), 165 (42%), 128 (37%), 115 (34%), 105
(58%).
HRMS Calc. for C14H17N8O4 (M+H): 361.137.
Found: 361.138.
HRMS Calc. for C16H13F5N5O4 (M+H): 434.081.
Found: 434.083.
5.2. Anti6iral and cytotoxicity assays
5.1.10. 1-(5-O-Acetyl-3-azido-2,3-dideoxy-i-D-eryth-
ro-pentofuranosyl)-5-methyl-4-pentafluorophenyl-
oxy-2(1H)-pyrimidinone (17)
The antiviral activities and cytotoxicities of all of the
compounds tested were determined using C8166 cells
infected with HIV-1IIIB as described previously [17]. The
inhibitory activity against HIV was determined by exam-
ining syncytia by XTT-Formazan assay for cell viability
[19] and by measuring antigen gp120 as reported previ-
ously [20]. The EC50 value is the concentration of
compound which reduces the production of viral antigen
by 50% and the TC50 value is the concentration of
compound which reduces the viability of uninfected cells
by 50%. Values are the mean of two different experiments
performed in triplicate (Table 1).
From 5%-O-acetyl-AZT [10] 8 (1.00 g, 3.24 mmol) dry
pyridine (30 ml), 4-chlorophenyl phosphodichloridate
(1.05 ml, 6.47 mmol) and PfpOH (2.38 g, 12.9 mmol) in
pyridine (10 ml). Flash column chromatography, eluting
with EtOAc–hexane 1:1, gave 17 as a colourless semi-
solid (0.95 g, 62%); TLC (EtOAc–hexane 1:1): Rf 0.51.
IR (KBr disc): wmax 3095, 2940, 2100, 1680, 1550, 1515,
1398, 1330, 1232, 1111, 992, 727 cm−1
.
1H NMR (CDCl3): l 2.17 (s, 3H, CH3), 2.25 (s, 3H,
5-CH3), 2.40 (m, 1H, 2%-CH), 2.73 (m, 1H, 2%-CH), 4.16
(m, 2H, 5-CH2), 4.42 (m, 2H, 3%-CH, 4%-CH), 6.09 (dd,
1H, J 4.8, 1.7 Hz, 1%-CH), 7.86 ppm (s, 1H, 6-CH).
13C NMR [(CD3)2SO]: l 11.9 (5-CH3), 21.0 (CH3), 37.3
(2%-CH2), 50.0 (3%-CH), 63.4 (5%-CH2), 82.1 (1%-CH), 86.7
(4%-CH), 102.1 (5-C), 145.4 (6-CH), 153.7 (4-C), 167.9
(2-CO), 170.5 ppm (CO).
Acknowledgements
We are very grateful to the MRC for support through
the AIDS-Directed Programme, to the BBSRC for a
studentship (to M.P. Wallis) and to the EPSRC Mass
Spectrometry Service (Swansea).
MS (FAB+): m/z (rel. int.) 498 (M+Na, 56%), 293
(100%), 184 (31%).
HRMS Calc. for C18H15F5N5O5 (M+H): 476.099.
Found: 476.100.
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To AZT 2 (500 mg, 1.87 mmol) dissolved in pyridine
(10 ml), trimethylsilyl chloride (0.48 ml, 3.74 mmol) was
added and the mixture stirred for 30 min before cooling
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