V. V. Filichev et al. / Bioorg. Med. Chem. 12 (2004) 2843–2851
2849
0
0
0
6
.2. 3 ,5 -Dideoxy-5 -methylenethymidine (7)
Asymmetric dihydroxylation of alkene 7 using AD-mix-
b under the same conditions gave the epimeric mixture 8
as a colourless oil (4:5 ratio of epimers (S:R)). Yield 24%
from 6.
19
A suspension of o-iodoxybenzoic acid (4.2 g, 15 mmol),
0
3
3
-deoxythymidine (5, 2.45 g, 10.1 mmol) in dry CH CN
(
90 mL) was refluxed for 1 h. The reaction mixture was
then cooled to room temperature, filtered. The precipitate
was washed with CH
CN (20 mL · 3). The combined
CH CN phases were concentrated in vacuo to give 3 ,5 -
dideoxy-5 -oxothymidine (6)
0
3
6.4. 1-[2,3-Dideoxy-6-O-(4,4 -dimethoxytrityl)-b-
thro-hexofuranosyl]thymine (10)
D
-ery-
0
0
3
0
12;13
(90%, 2.0 g) as a white
foam that was used in the next stepwithout purification.
Compound 9 (200 mg, 0.78 mmol) was dissolved in an-
0
hyd pyridine (10 mL) and 4,4 -dimethoxytrityl chloride
MePPh Br (7.6 g, 21.5 mmol) was suspended in dry THF
3
(290 mg, 0.86 mmol) was added under nitrogen. After
3 h MeOH (1 mL) was added and solvents were removed
in vacuo to half the volume. EtOAc (30 mL) was added
(
125 mL) and cooled to 0 ꢁC. Lithium bis(trimethyl-
silyl)amide (21.5 mL of an 1 M solution in THF,
1.5 mmol) was added dropwise under nitrogen and the
2
and extracted with satd aq NaHCO
water phase was extracted with EtOAc (10 mL · 2). The
combined organic layers were dried (MgSO ), filtered
3
(10 mL · 3). The
red suspension was stirred for 30 min before the crude
0
5
-aldehyde (6, 2.0 g, 9.1 mmol) dissolved in THF
4
(
50 mL) was added dropwise at 0 ꢁC. The reaction
mixture was stirred at room temperature for 1 h and
then cooled by ice-water bath. H O (100 mL) was added
and evaporated under diminished pressure. The residue
was co-evaporated twice with toluene/EtOH (5 mL, 1:1,
v/v). The residue was adsorbed on a silica gel (0.5 g)
2
slowly. EtOAc (100 mL) was added and layers were
separated. The water phase was extracted with CHCl3
from CHCl
vacuum chromatography with MeOH (0–2%, v/v) in
3
(10 mL) and purified using dry column
20
(
75 mL · 4) until no UV-active compounds were
detected by TLC in the water layer. Combined organic
layers were dried (MgSO ) and filtered. Silica gel (5.0 g)
CHCl
foam. H NMR (CDCl
3
to afford compound 10 (71%, 310 mg) as a white
0
1
3
) d 1.80 (m, 1H, 3 -H), 1.84 (s,
3H, Me), 2.00 (m, 2H, 3 -H, 2 -H), 2.38 (m, 1H, 2 -H),
0
0
0
4
0
was added and solvents were removed in vacuo. The
residue was purified using dry column vacuum chro-
matography and EtOAc (10–50%, v/v) in cyclohexane
as an eluent to afford compound 7 (2.5 g). Although
2.99 (s, 1H, OH), 3.20 (m, 2H, 6 -H), 3.78 (s, 6H,
0
0
2 · OMe), 4.18 (m, 1H, 5 -H), 4.21 (m, 1H, 4 -H), 6.06
20
0
(dd, 1H, J ¼ 3:2, 7.0 Hz, 1 -H), 6.80–6.86, 7.25–7.45 (m,
13H, Ar), 7.69 (d, 1H, J ¼ 1 Hz, 6-H), 9.30 (br s, 1H,
13
0
0
contaminated with Ph
1
3
P@O, this compound was used
NH); C NMR (CDCl
3
) d 12.5 (Me), 23.4 (C3 ), 32.3
(C2 ), 55.1 (OMe), 64.6 (C6 ), 71.0 (C5 ), 81.6 (C4 ), 85.4
0
0
0
0
0
for the next step. H NMR (CDCl
3
) d 1.70 (m, 1H, 3 -
H), 1.90 (s, 3H, Me), 2.05–2.15 (m, 3H, 3 -H, 2 -H), 2.20
0
0
(C1 ), 86.4 (CAr ), 110.2 (C5), 113.1, 126.9, 127.8, 128.0,
3
0
0
(
m, 1H, 2 -H), 4.52 (m, 1H, 4 -H), 5.28 (d, 1H,
0
129.9, 136.4, 144.4, 158.5 (DMT), 135.6 (C6), 150.5
(C2), 164.0 (C4); HR-ESI-MS m=z 581.334 calcd for
0
J ¼ 10:4 Hz, 6 -H), 5.38 (d, 1H, J ¼ 17:0 Hz, 6 -H), 6.0
0
þ
(
ddd, 1H, J ¼ 17:0, 10.4, 4.2 Hz, 5 -H), 6.14 (dd, 1H,
C H N O Na [M+Na] , found m=z 581.333.
32
34
2
7
0
J ¼ 3:4, 6.6 Hz, 1 -H), 7.35 (s, 1H, 6-H), 9.70 (br s, 1H,
13
0
NH); C NMR (CDCl ) d 12.6 (Me), 29.6 (C3 ), 32.6
3
0
0
0
0
0
6.5. 1-{2,3-Dideoxy-6-O-(4,4 -dimethoxytrityl)-5-O-[2-
cyanoethoxy(diisopropylamino)phosphino]-b- -erythro-
(
1
C2 ), 81.7 (C4 ), 86.2 (C1 ), 110.2 (C5), 117.5 (C6 ),
0
35.3 (C6), 136.4 (C5 ), 150.4 (C2), 164.1 (C4); HR-ESI-
þ
D
MS m=z 467.190 calcd for C22
found m=z 467.189.
H
28
N
4
O
6
Na [M
2
+Na] ,
hexofuranosyl}thymine (11)
Compound 10 (150 mg, 0.27 mmol) was dissolved under
nitrogen in anhyd CH Cl (10 mL). N,N-Diisopropyl-
2
2
6
.3. 1-(2,3-Dideoxy-b-
D
-erythro-hexofuranosyl)thymine
ammonium tetrazolide (97 mg, 0.56 mmol) was added
followed by dropwise addition of 2-cyanoethyl tetra-
isopropylphosphordiamidite (190 mg, 0.59 mmol). After
24 h analytical TLC showed no more starting material
(
9)
2
AD-mix-a (12.5 g) dissolved in H O (75 mL) and
t-BuOH (75 mL) were stirred at room temperature until
two clear phases were observed (20 min). Compound 7
and the reaction was quenched with H
lowed by addition of CH Cl (10 mL). The mixture was
2
O (1 mL) fol-
2
2
(
2 g) dissolved in t-BuOH (20 mL) was added to the
washed with satd aq NaHCO
3
(10 mL · 2). The org.
phase was dried (Na SO ), filtered, silica gel (0.3 g) was
mixture and vigorous stirring was continued for 24 h at
room temperature. Na SO (12.5 g) was added and the
mixture was stirred for 3 h. Silica gel (2 g) was added and
solvents were removed in vacuo. The residue was chro-
matographed using dry column vacuum chromatogra-
phy with MeOH (2–7%, v/v) in CHCl
epimeric mixture 8 (30% from 6, 820 mg) as a colourless
oil (1:9 ratio of epimers (S:R), as estimated from the
integral of the individual H-6 signals in the H NMR
spectrum). Crystallization of 8 from acetone gave com-
pound 9 (20% from 6, 540 mg) as white crystals. R
NMR and C NMR are in agreement with the previ-
2
4
added and solvents were removed under reduced pres-
sure. The residue was purified using silica gel dry column
2
3
20
vacuum chromatography
with cyclohexane/EtOAc
(25–50%). Combined UV-active fractions were evapo-
20
3
to afford
rated in vacuo affording 11 (125 mg, 61%) as a foam that
was co-evaporated with dried CH
3
CN (30 mL · 3)
1
before using in ODN synthesis. H NMR (CDCl ) d
3
1
i
0
1.20 (m, 12H, 4 · Me [Pr ]), 1.80–1.90 (m, 5H, Me, 3 -H),
2.05 (m, 1H, 2 -H), 2.37 (m, 1H, 2 -H), 2.43 (t, 2H,
0
0
1
f
, H
CH
0
2
CN), 2.58 (t, 2H, CH CH
6 -H), 3.42–3.60 (m, 2H, 2 · CH [Pr ]), 3.80 (s, 6H,
2
2
CN), 3.10–3.40 (m, 2H,
i
13
9
0
0
ously published data.
2 · OMe), 4.18–4.26 (m, 2H, 5 -H, 4 -H), 6.06 (2 · d, 1H,