794 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 3
Rahim et al.
4.45-4.75 (m, 1H, H-4′ of â-anomer), 5.65-5.82 (m, 1H, H-3′),
6.25-6.5 (m, 1H, H-1′), 7.25 (m, 4H, aromatic H’s), 7.8-8.0
(m, 4H, aromatic H’s), 8.15 (s, 1H, H-6 of â-anomer), 8.3 (s,
1H, H-6 of R-anomer), 11.65 (bs, 1H, NH); MS m/z 518 M+.
Dep r otection w ith Bor on Tr ich lor id e. 2′-Deoxy-5-
eth yl-4′-th iou r id in e (3i). To a vigorously stirred solution
of the anomeric mixture 2R/2â (R ) ethyl, R′ ) benzyl) (0.23
g, 0.51 mmol) in 10 mL of dry dichloromethane at -78 °C
under nitrogen was slowly added a 1 M solution of boron
trichloride (15.24 mL, 15.24 mmol) in dichloromethane, keep-
ing the reaction temperature below -75 °C during the addi-
tion. After the addition was complete, the mixture was stirred
at -78 °C for 8 h and then quenched at that temperature by
the cautious addition of 30 mL of a 1:1 mixture of dry
dichloromethane/methanol. The mixture was then allowed to
warm slowly to ambient temperature and evaporated to
dryness. The residue was purified by silica gel column
chromatography eluting with 10% methanol/chloroform, and
the resulting anomeric nucleoside mixture was further purified
by preparative reversed-phase HPLC on a Zorbax-C8 column
eluting with 10% acetonitrile/water to give the separated
anomers of the required product, 3i. R-Anomer (0.016 g, 19%
of available R-anomer): 1H NMR (Me2SO-d6) 1.05 (t, 3H,
CH2CH3), 2.05 (dt, 1H, H-2′), 2.25 (q, 2H, CH2CH3), 2.55 (m,
1H, H-2′, partially obscured by solvent), 3.45-3.7 (m, 3H, H-4′
and H-5′), 4.34 (m, 1H, H-3′), 5.00 (t, 1H, OH-5′), 5.50 (d, 1H,
OH-3′), 6.2 (q, 1H, H-1′), 8.12 (s, 1H, H-6), 11.1 (bs, 1H, NH);
MS m/z 272 M+. Anal. (C11H16N2O4S‚H2O) C, H, N. â-Anomer
methoxide in methanol for 2.5 h. The mixture was then
neutralized with Dowex 50 (H+) resin and filtered, the filtrate
was evaporated to dryness, and the residue was purified by
silica gel column chromatography eluting with 15% methanol/
chloroform to give the title compound 3viii (0.022 g, 27% yield):
mp 246 °C; 1H NMR (Me2SO-d6) d 2.21 (m, 2H, H-2′), 3.32 (m,
1H, H-4′), 3.63 (m, 2H, H-5′), 4.36 (m, 1H, H-3′), 5.14 (dd, 1H,
vinylic), 5.26 (m, 2H, OH-3′ and OH-5′), 6.00 (dd, 1H, vinylic),
6.26 (t, 1H, H-1′), 6.3-6.5 (dd, 1H, vinylic), 8.20 ppm (s, 1H,
H-6); MS m/z 271 (M + H)+. Anal. (C11H14N2O4S) C, H, N.
2′-Deoxy-5-isopr open yl-4′-th iou r idin e (3ix). To a stirred
solution of (tetrakistriphenylphosphine)palladium(0) (0.038 g,
0.03 mmol) in 40 mL of HMPA under nitrogen was added 4
(R ) H) (0.2 g, 0.33 mmol) followed by isopropenyltrimethyltin
(0.15 g, 0.73 mmol) and one crystal of 2,6-di-tert-butyl-p-cresol
(as a radical inhibitor), and the mixture was heated at 100 °C
for 20 h. Following a similar workup to that for the synthesis
of 3viii, the p-toluoyl-protected intermediate was obtained
(0.043 g, 25% yield) following silica gel column chromatography
eluting with 15% methanol/dichloromethane. Similar depro-
tection with sodium methoxide afforded the title compound
3ix after reversed-phase HPLC purification using a 0-95%
linear gradient of acetonitrile/water on a Zorbax C18
column
(0.01 g, 46% yield): 1H NMR (Me2SO-d6) 1.95 (s, 3H, Me), 2.22
(m, 2H, H-2′), 3.3 (m, 1H, H-4′), 3.6 (m, 2H, H-5′), 4.35 (m,
1H, H-3′), 5.05 (m, 1H, vinylic), 5.22 (m, 2H, OH-3′ and OH-
5′), 5.8 (m, 1H, vinylic), 6.26 (t, 1H, H-1′), 8.03 (s, 1H, H-6),
11.32 ppm (bs, 1H, NH); MS m/z 284 M
+. Anal (C12H16N2O4S)
1
(0.023 g, 40% yield of available â-anomer): H NMR (Me2SO-
C, H, N.
d6) 1.05 (t, 3H, CH2CH3), 2.25-2.4 (m, 4H, H-2′ and CH2CH3),
3.3 (m, 1H, H-4′ partially obscured by DOH), 3.62 (m, 2H,
H-5′), 4.37 (m, 1H, H-3′), 5.16 (t, 1H, OH-5′), 5.24 (d, 1H, OH-
3′), 6.3 (t, 1H, H-1′), 7.8 (s, 1H, H-6), 11.28 (bs, 1H, NH); MS
m/z 272 M+. Anal. (C11H16N2O4S‚0.3H2O) C, H, N.
5-Ch lor o-2′-d eoxy-4′-th iou r id in e (3xxviii). A suspension
of a 1:1 mixture of 5i and 5ii (5.3 g, 19 mmol) and cytidine
deaminase from E. coli (357 units) in 150 mL of water was
gently stirred at 37 °C overnight, and the solvent was
evaporated. The residue was dissolved in the minimum
volume of methanol, adsorbed onto silica gel, and purified by
silica gel column chromatography eluting with 5-20% methanol/
dichloromethane gradient. The pooled product fractions were
evaporated to dryness, and the residual solid was recrystallized
twice from methanol to give the title compound 3xxviii (0.8
Dep r otection w ith Sod iu m Meth oxid e. 2′-Deoxy-5-
(p r op -1-yn yl)-4′-th iou r id in e (3xii). The anomeric mixture
2R/2â (R ) prop-1-ynyl, R′ ) p-toluoyl) (0.206 g, 0.397 mmol)
was dissolved in 15 mL of methanol containing sodium
methoxide (0.021 g, 0.397 mmol) and kept at ambient tem-
perature overnight. The solution was neutralized with Dowex
50 (H+) ion-exchange resin and filtered, and the filtrate was
evaporated to dryness. The resulting residue was washed with
3 × 4 mL of ether, 10 mL of hot acetone, and finally 2 × 7 mL
of methanol. This gave the required compound, 3xii, as the
pure â-anomer, homogeneous by analytical reversed-phase
HPLC on a Zorbax C8 column eluting with 20% acetonitrile/
water (0.03 g, 66% yield of available â-anomer): 1H NMR (Me2-
SO-d6) 2.0 (s, 3H, propynyl-CH3), 2.15 (m, 2H, H-2′), 3.3 (m,
1H, H-4′ partially obscured by DOH), 3.6 (m, 2H, H-5′), 4.3
(m, 1H, H-3′), 5.1-5.3 (m, 2H, OH-3′ and OH-5′), 6.25 (t, 1H,
H-1′), 8.7 (s, 1H, H-6), 11.55 (bs, 1H, NH); MS m/z 282 M+.
Anal. (C12H14N2O4S‚1.22H2O) C; H: calcd, 5.40; found, 4.55;
N: calcd, 9.21; found 8.75.
2′-Deoxy-4′-th io-5-vin ylu r id in e (3viii). A mixture of
3xxx (0.37 g, 1 mmol) and N-ethyldiisopropylamine (0.26 g, 2
mmol) in 10 mL of dry pyridine was cooled with stirring to -3
°C, and then p-toluoyl chloride (0.8 mL, 6 mmol) was added
in small portions. After 5 min, the reaction mixture was
stirred at room temperature for 5 h and quenched with 1 mL
of water. The mixture was then evaporated in vacuo to give
a thick oil, which was dissolved in 35 mL of chloroform and
washed with 2 × 20 mL of water. The organic layer was dried
(MgSO4) and evaporated to dryness, and the residue was
purified by silica gel column chromatography eluting with 50%
ethyl acetate/hexane to give 4 (R ) p-toluoyl) (0.627 g, 87%
yield). A mixture of this intermediate (0.22 g, 0.305 mmol),
tetravinyltin (0.1 mL, 0.7 mmol), and tetrakistriphenylphos-
phine palladium(0) (0.041 g, 0.035 mmol) in 3.5 mL of
hexamethylphosphoramide was stirred under nitrogen at 75
°C for 17 h. After the mixture was cooled to room temperature,
25 mL of water was added and the mixture extracted with 2
× 25 mL of ether. The combined ethereal extracts were dried
(magnesium sulfate), evaporated in vacuo to give the chro-
matographically pure protected 5-vinyl intermediate (0.185 g,
97% yield). This was deprotected by treatment at room
temperature with 60 mL of a 0.05 mol solution of sodium
1
g, 30% yield based on 5i): mp 221-222 °C; H NMR (Me2SO-
d6) 2.22 (m, 2H, H-2′), 3.3 (m, 1H, H-4′), 3.65 (m, 2H, H-5′),
4.35 (m, 1H, H-3′), 5.23 (m, 2H, OH-3′ and OH-5′), 6.22 (t, 1H,
H-1′), 8.43 (s, 1H, H-6), 11.85 ppm (bs, 1H, NH); MS m/z 278
M+. Anal. (C9H11ClN2O4S) C, H, N.
(E)-5-P r op en -1-ylu r a cil. To a solution of uracil (1 g, 9
mmol) in 200 mL of water at 70 °C was added mercuric acetate
(2.9 g, 9.1 mmol), and the mixture was stirred for 7 days. After
the mixture was cooled to room temperature, sodium chloride
(1.5 g, 25.6 mmol) was added, and the mixture stirred for 4 h.
The resulting thick suspension was filtered, washed with
water, and dried under high vacuum to give 5-chloromercu-
riuracil (2.27 g). To this intermediate (1 g, 2.9 mmol) in 25
mL of acetonitrile was added lithium tetrachloropalladate(II)
(0.76 g, 2.9 mmol) and allyl chloride (2.9 mL, 35.6 mmol), and
the mixture was stirred at room temperature for 7 days. The
resulting solid was filtered off, and the filtrate was evaporated
to dryness. The residue was taken up in 75 mL of methanol,
and hydrogen sulfide was bubbled through the solution for a
few minutes. The resulting black solid was filtered off, and
the colorless filtrate was evaporated to dryness. The residue
was purified by silica gel column chromatography eluting with
8% methanol/dichloromethane to give 5-allyluracil (0.085 g).
To a suspension of this (0.08 g, 0.5 mmol) in 50% aqueous
ethanol was added tris(triphenylphosphine)rhodium(I) chloride
(0.09 g, 0.1 mmol), and the mixture was heated under reflux
for 72 h. The solvent was evaporated, and the residue was
purified by silica gel column chromatography eluting with 5%
methanol/dichloromethane to give the title compound (0.056
g, 70%): 1H NMR (Me2SO-d6) d 1.75 (m, 3H, CH3), 6.05 (d, 1H,
vinylic, J ) 14 Hz), 6.4 (m, 1H, vinylic), 7.42 (s, 1H, H-6), 11
ppm (bs, 2H, NH).
Vir a l P la qu e Red u ction Assa ys. Antiviral assays were
performed using an adaptation of the plaque reduction assay
described by Crumpacker and co-workers.42 Twenty-four well
plates containing monolayers of MRC 5 cells (human embryo
lung fibroblasts, ATCC CCL 171) were used for assays of
Rahim
