0.89 (9H, s), 0.92–0.96 (6H, m), 1.29–1.36 (4H, m), 1.55–1.62
(4H, m), 2.24–2.30 (1H, m), 2.57–2.63 (1H, m), 3.33 (2H, t,
J = 7.3), 3.53 (2H, t, J = 7.6 Hz), 3.74 (1H, d, J = 12.0), 3.82
(1H, br), 3.92–3.97 (2H, m), 4.52–4.55 (1H, m), 6.01–6.04
(2H, m), 7.69 (1H, d, J = 7.3), 8.83 (1H, s); dC (126 MHz;
CDCl3; CDCl3) ꢂ4.8, ꢂ4.6, 13.8, 13.8, 18.1, 19.9, 20.2, 25.9,
29.2, 31.1, 40.7, 45.6, 46.2, 52.3, 62.2, 71.8, 88.3, 90.4, 103.2,
143.3, 156.5, 158.5, 172.1; m/z (ESI) 481.3259 [M + H]+.
C24H45N4O4Si+ requires 481.3205.
6-N-[(Dimethylamino)methylene]-50-O-[(4-methoxytrityl)-
sulfenyl]-20-deoxyadenosine (3a). Compound 2a (2.9 g, 4.0 mmol)
was rendered anhydrous by repeated co-evaporation with dry
THF and finally dissolved in dry THF (36 mL). TEAꢁ3HF
(2.0 cm3, 12 mmol) and TEA (1.7 cm3, 12 mmol) were added to
the solution. After being stirred for 24 h, the reaction was
quenched by the addition of water (10 cm3). The solution was
diluted with ethyl acetate (150 cm3) and then washed with
water (100 cm3 ꢃ 3). The organic layer was collected,
dried over MgSO4, filtered and concentrated under reduced
pressure. The residue was chromatographed on a silica gel
column (100 g) with ethyl acetate–methanol (100 : 3, v/v) to
yield 3a (1.5 g, 62%). dH(500 MHz; CDCl3; TMS) 2.37–2.43
(1H, m), 2.48–2.54 (1H, m), 3.09 (1H, s), 3.20 (3H, s), 3.26
(3H, s), 3.43–3.53 (2H, m), 3.78 (3H, s), 3.86 (1H, dd, J = 7.4
and 3.8), 4.29 (1H, m), 6.43 (1H, t, J = 6.6), 6.80–6.83
(2H, m), 7.22–7.36 (12H, m), 8.08 (1H, s), 8.51 (1H, s), 8.98
(1H, s); dC(126 MHz; CDCl3; CDCl3) 35.1, 40.5, 41.2, 55.2,
71.7, 71.8, 83.9, 85.6, 113.3, 126.2, 127.3, 128.0, 129.9, 131.0,
134.0, 139.8, 142.8, 142.9, 151.1, 152.5, 158.3, 158.7, 159.6; m/z
(ESI) 611.2487 [M + H]+. C33H35N6O4S+ requires 611.2435.
30-O-(tert-Butyldimethylsilyl)-4-N-[(dibutylamino)methylene]-
50-O-[(4-methoxytrityl)sulfenyl]-20-deoxycytidine (2d). Compound
1d (200 mg, 0.42 mmol) was rendered anhydrous by repeated
co-evaporation with dry THF and finally dissolved in dry
THF (1.8 cm3). The solution was cooled to ꢂ78 1C and then,
n-BuLi (1.59 M in THF, 0.46 mmol, 0.3 cm3) was added. After
being stirred at ꢂ78 1C for 20 min, the reaction was warmed to
ambient temperature. Subsequently, MMTrSCl (0.67 mmol,
230 mg) was added and the resulting solution stirred for 1 h.
The reaction was quenched by the addition of concentrated
NH3 (1 cm3). The solution was diluted with ethyl acetate
(50 cm3) and then washed with sat. NaHCO3 (50 cm3 ꢃ 3).
The organic layer was collected, dried over MgSO4, filtered
and concentrated under reduced pressure. The residue was
chromatographed on a silica gel column (30 g) with hexane–
ethyl acetate (7 : 3, v/v) containing 0.5% triethylamine to
yield 2d (181 mg, 58%). dH(500 MHz; CDCl3; TMS) 0.01
(6H, s ꢃ 2), 0.84 (9H, s), 0.94–0.99 (6H, m), 1.32–1.40 (4H, m),
1.58–1.64 (4H, m), 1.91–1.97 (1H, m), 2.36–2.42 (1H, m), 3.35
(2H, t, J = 7.3), 3.41 (1H, dd, J = 3.2 and 11.2), 3.48 (1H, dd,
J = 3.4 and 11.2), 3.54–3.58 (2H, m), 3.71 (1H, dd, J = 3.3
and 7.4), 3.82 (3H, s), 4.08–4.11 (1H, m), 5.99 (1H, d, J = 7.3),
6.24 (1H, t, J = 6.1), 6.83–6.87 (2H, m), 7.26–7.39 (12H, m)
7.72 (1H, d, J = 7.3), 8.85 (1H, s); dC(126 MHz; CDCl3;
CDCl3) ꢂ4.8, ꢂ4.6, 13.8, 13.9, 18.1, 19.9, 20.2, 25.8, 29.2, 31.1,
42.0, 45.4, 52.2, 55.3, 55.3, 71.0, 71.9, 86.2, 86.4, 102.9, 113.5,
127.5, 128.1, 130.0, 131.2, 134.1, 140.9, 143.0, 143.0,156.4,
4-N-[(Dibutylamino)methylene]-50-O-[(4-methoxytrityl)sulfenyl]-
20-deoxycytidine (3d). Compound 2d (3.5 g, 4.5 mmol) was
treated with TEAꢁ3HF (2.2 cm3, 13.4 mmol) and TEA
(1.9 cm3, 13.4 mmol) according to the procedure described
for 3a to yield 3d (1.7 g, 58%). dH(500 MHz; CDCl3; TMS)
0.92–0.98 (6H, m), 1.28–1.34 (4H, m), 1.56–1.64 (4H, m),
1.92–1.98 (1H, m), 2.32 (1H, br), 2.44–2.50 (1H, m), 3.33
(2H, t, J = 7.4), 3.41 (1H, dd, J = 3.1 and 11.1), 3.50–3.57
(3H, m), 3.75–3.78 (1H, dd, J = 6.8 and 3.2), 3.80 (1H, s),
4.02–4.04 (1H, m), 6.02 (1H, d, J = 7.3), 6.24 (1H, t, J = 6.2),
6.81–6.85 (2H, m), 7.23–7.37 (12H, m), 7.75 (1H, d, J = 7.1)
8.83 (1H, s); dC(126 MHz; CDCl3; CDCl3) 13.8, 13.9, 19.9,
20.2, 29.2, 31.1, 41.8, 45.5, 52.2, 55.4, 71.2, 72.0, 85.7, 86.5,
103.1, 113.5, 127.5, 128.2, 130.0, 131.2, 134.1, 140.9, 142.9,
143.0, 156.5, 158.3, 158.9, 172.0; m/z (ESI) 671.3294
[M + H]+. C38H47N4O5S+ requires 671.3262.
158.2, 158.9, 172.0; m/z (ESI) 785.4144 [M
C44H61N4O5SSi+ requires 785.4126.
+
H]+.
2-N-Isobutyryl-50-O-[(4-methoxytrityl)sulfenyl]-20-deoxyguanosine
(3e). Crude 2e (13 g, 18 mmol) was treated with TEAꢁ3HF
(8.6 cm3, 53 mmol) and TEA (7.4 cm3, 53 mmol) according to
the procedure described for 3a to yield 3e (7.5 g, 48% in 2 steps
from 1e). dH(500 MHz; CDCl3; TMS) 1.20–1.26 (m, 6H),
2.23–2.34 (m, 2H), 2.77–2.83 (m, 1H), 3.39–3.46 (m, 2H),
3.73 (s, 3H), 3.85 (d, J = 3.2 Hz, 1H), 4.01 (s, 1H), 4.30
(s, 1H), 6.01 (t, J = 6.6 Hz, 1H), 6.77 (d, J = 8.8 Hz, 2H),
7.13–7.30 (m, 12H), 7.83 (s, 1H), 10.23 (s, 1H), 12.32 (s, 1H);
dC(126 MHz; CDCl3; CDCl3) 19.1, 19.2, 36.4, 40.75, 46.0,
55.4, 71.7, 72.0, 78.3, 84.2, 86.3, 113.5, 121.2, 127.5, 128.1,
130.0, 131.2, 134.1, 137.5, 143.0, 143.1, 148.0, 148.5, 156.0,
159.0, 179.8. ESI-MS: calc. for C34H36N5O6S [M + H]+,
642.2381; found, 642.2381.
30-O-(tert-Butyldimethylsilyl)-2-N-isobutyryl-50-O-[(4-methoxy-
trityl)sulfenyl]-20-deoxyguanosine (2e). 30-O-(tert-Butyldimethyl-
silyl)-2-N-isobutyryl-20-deoxyguanosine (1e, 11 g, 24 mmol)
was rendered anhydrous by repeated co-evaporation with dry
THF and finally dissolved in dry THF (120 cm3). LHMDS
(1.6 M in THF, 53 mmol, 33 cm3) was added to the solution,
which was then stirred at room temperature for 20 min.
Subsequently, MMTrSCl (38 mmol, 13 g) was added and the
resulting solution was stirred for 1 h. The reaction was
quenched by the addition of concentrated NH3 (20 cm3).
The solution was diluted with ethyl acetate (200 cm3) and
then washed with sat. NaHCO3 (250 cm3 ꢃ 3). The organic
layer was collected, dried over MgSO4, filtered and concen-
trated under reduced pressure. The residue was subjected to
flash column chromatography on a silica gel column (145 g)
with hexane–ethyl acetate (3 : 1, v/v) to yield crude 2e (13 g).
This material was used without further purification in the
preparation of 3e.
6-N-[(Dimethylamino)methylene]-50-O-[(4-methoxytrityl)-
sulfenyl]-20-deoxyadenosine 30-(2-cyanoethyl-N,N-diisopropyl-
phosphoramidite) (4a). Compound 3a (1.4 g, 2.3 mmol) was
rendered anhydrous by repeated co-evaporation with
dry CH2Cl2, and finally dissolved in dry CH2Cl2 (4.5 cm3).
Then, 2-cyanoethyl N,N,N0,N0-tetraisopropylphosphorodiamidite
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
990 | New J. Chem., 2010, 34, 984–992