1728
A. Hatano et al. / Tetrahedron 61 (2005) 1723–1730
The major b-anomer product was recrystallized from MeOH
to afford 2b as colorless needles (1.36 g, 18%). H NMR
[M]C. Anal. Calcd for C18H18O4S: C, 65.43; H, 5.49; N,
0.00; S, 9.71. Found: C, 65.28; H, 5.44; N, 0.00; S, 9.87.
1
(CDCl3): d 2.20 (1H, m), 2.39 (3H, s), 2.43 (3H, s), 2.49
(1H, JZ9.3, 14.1 Hz, dd), 4.52 (1H, m), 4.63 (2H, m), 5.21
(1H, JZ5.1, 11.2 Hz, dd), 5.59 (1H, JZ6.4 Hz, d), 7.27
(9H, m), 7.46 (4H, m), 7.91 (2H, JZ8.3 Hz, d), 7.97 (2H,
JZ8.3 Hz, d); 13C NMR (CDCl3): d 21.7, 21.7, 41.7, 64.7,
80.3, 83.0, 126.7, 126.9, 127.0, 127.2, 127.5, 127.6, 127.7,
127.8, 129.2, 129.5, 129.7, 129.7, 136.6, 136.9, 143.9,
144.2, 166.1, 166.4. FABMS m/e 571 [MCH]C. Anal.
Calcd for C33H30O5S2: C, 69.45; H, 5.30; N, 0.00; S, 11.24.
Found: C, 69.37; H, 5.26; N, 0.00; S, 11.18.
4.1.5. Compound 5. Compound 4 (50.0 mg, 0.154 mmol)
was co-evaporated 3 times in 3 mL of dry pyridine. The
solid was dissolved in 1 mL of dry pyridine. DMTrCl
(97.3 mg, 0.287 mmol) was added as a solid in one portion
to the stirred solution under Ar and the mixture was stirred
at room temperature. After 1 h, the reaction was quenched
by the addition of EtOH (0.5 mL). The mixture was poured
into 10 mL of ice water and extracted 3 times with 15 mL of
CH2Cl2. The combined organic phase were dried over
MgSO4 and concentrated. A silica gel column with hexane–
EtOAc (3:1) afforded 5 as a yellow foam (93.2 mg, 96%).
1H NMR (CDCl3): d 2.01 (2H, br), 2.22 (1H, JZ1.8, 7.4,
14.7 Hz, ddd), 3.27 (1H, JZ5.4, 9.8 Hz, dd), 3.35 (1H, JZ
4.0, 8.0 Hz, dd), 4.08 (1H, br), 4.40 (1H, br), 5.21 (1H, JZ
5.6, 10.2 Hz, dd), 6.81 (4H, JZ8.8 Hz, d), 7.19–7.60 (16H,
m), 8.01 (2H, JZ7.4 Hz, d); 13C NMR (CDCl3): d 43.9,
55.2, 64.4, 74.6, 79.5, 86.3, 86.4, 113.1, 126.1, 126.8, 127.5,
127.9, 128.2, 128.7, 130.1, 133.6, 135.0, 136.0, 136.6,
143.6, 144.8, 158.5, 190.2. FABMS m/e 633 [MCH]C;
HRMS calcd for C39H36N11O6S 633.2311, found 633.2347.
1
4.1.2. Compound 2a. (0.47 g, 6.4%) H NMR (CDCl3): d
2.27 (1H, m), 2.39 (3H, s), 2.40 (3H, s), 2.91 (1H, m), 4.55
(2H, m), 4.66 (1H, m), 5.34 (1H, JZ6.6 Hz, t), 5.58 (1H,
m), 7.24–8.00 (17 H, m); 13C NMR (CDCl3): d 21.6, 40.2,
64.4, 76.1, 79.6, 82.1, 126.1, 126.4, 126.8, 126.9, 127.3,
127.5, 128.7, 128.8, 128.8, 129.3, 129.4, 135.7, 136.7,
141.5, 143.5, 143.6, 165.6, 165.9. FABMS m/e 571
[MCH]C.
4.1.3. Compound 3. LiAlH4 (0.524 g, 13.8 mmol) was
carefully added to a solution of the bis-toluoylester 2
(1.58 g, 2.76 mmol) in dry THF (50 mL). The reaction
mixture was stirred at 4 8C for 1 h and then quenched by a
1 N-H2SO4 aqueous solution (3 mL). The residue was
poured into 50 mL of 1 N-HCl, and then extracted with
50 mL of CH2Cl2 (8 times), dried over anhydrous MgSO4,
and evaporated. The crude product was chromatographed
with CHCl3–MeOH (9:1) and then recrystallized from
MeOH to afford mercaptophenyl nucleoside (3) as colorless
needles (0.231 g, 37%). 1H NMR (CD3OD): d 1.90 (1H, m),
2.15 (1H, JZ2.4, 5.1, 5.1 Hz, ddd), 3.65 (2H, m), 3.91 (1H,
JZ3.9, 10.7 Hz, td), 4.29 (1H, br), 5.05 (1H, JZ5.4,
10.7 Hz, dd), 7.23 (1H, JZ12.2 Hz, d), 7.25 (1H, JZ
11.8 Hz, d); 13C NMR (CD3OD): d 44.9, 64.1, 74.5, 81.3,
89.2, 128.0, 130.5 132.2, 140.4. EIMS m/e 226 [M]C.
Anal. Calcd for C11H14O3S: C, 58.38; H, 6.24; N, 0.00; S,
4.1.6. Compound 6. Compound 5 (92 mg, 0.145 mmol) was
dissolved in 2 mL of dry CH2Cl2 and purged with Ar for
2 min To the stirred solution was added N,N0-diiso-
propylrthylamine (37.5 mg, 0.290 mmol) and 2-cyano-
ethyl-N,N0-diisopropylchlorophosphoramidite (44.7 mg,
0.189 mmol). The reaction mixture was stirred under Ar at
room temperature while protected from light for 1 h. The
reaction mixture was added to 30 mL of CH2Cl2 and washed
twice with 30 mL of H2O. The organic layer was dried over
MgSO4, filtered and evaporated. The crude compound was
chromatographed with 1% trimethylamine in hexane–
EtOAc (3:1) to obtain 6 as a colorless solid (98 mg, 93%).
1H NMR (CDCl3): d 1.12–1.31 (14H, m), 1.65 (1H, br), 2.04
(1H, m), 2.38 (1H, m), 2.46 (1H, JZ6.3 Hz, t), 2.62 (1H,
JZ6.5 Hz, t), 3.31 (2H, m), 3.78 (6H, s), 4.27 (1H, br), 4.53
(1H, br), 5.22 (1H, JZ4.6, 9.6 Hz, dd), 6.84 (4H, JZ5.0,
9.0 Hz, dd), 7.19–7.66 (16H, m), 8.04 (2H, JZ8.3 Hz, d).
FABMS m/e 833 [MCH]C. HRMS calcd for
C48H54N2O7PS 833.3389, found 833.3376.
14.17. Found: C, 58.25; H, 6.18; N, 0.00; S, 14.18. 3260
:
7080 cmK1 MK1 in 10 mM Na–phosphate buffer, 100 mM
NaCl at pH 7.0.
4.1.4. Compound 4. To a solution of 3 (118 mg,
0.520 mmol) and diisopropylethylamine (134 mg,
1.04 mmol) in THF (3 mL) was added a solution of benzoyl
chloride (80.4 mg, 0.572 mol) dropwise over 10 min with a
nitrogen inlet in an iced water bath The reaction mixture
was stirred for 1 h at room temperature, and then the
reaction solution was quenched by 1 mL of MeOH. The
mixture was added to 30 mL of CH2Cl2, and washed twice
with 30 mL of H2O, and dried over anhydrous MgSO4. The
solution was filtered, concentrated, and purified by silica gel
chromatography eluting with CHCl3–MeOH (9:1). The
major product was recrystallized from MeOH to afford 4 as
colorless needles (122 mg, 71%). 1H NMR (CDCl3): d 1.94
(2H, br), 2.06 (1H, JZ4.6, 6.3, 19.5 Hz, ddd), 2.37 (1H, JZ
1.5, 5.9, 13.2 Hz, ddd), 3.82 (2H, m), 4.02 (1H, m), 4.42
(1H, br), 5.22 (1H, JZ5.6, 10.3 Hz, dd), 7.47 (6H, m), 7.62
(1H, JZ7.3, 7.3 Hz, t), 8.03 (2H, JZ7.3 Hz, d); 13C NMR
(CDCl3): d 44.1, 63.4, 73.8, 79.6, 87.4, 126.5, 126.8, 127.5,
128.8, 133.7, 135.2, 136.6, 143.2, 190.3. EIMS m/e 330
4.2. Oligonucleotide synthesis
The DNA oligomers were synthesized on a DNA synthe-
sizer by phosphoramidite chemistry, with a coupling time
for a unnatural monomer of 3 min Syntheses were
performed using a 1-mmol-scale trityl-on mode, according
to the manufacturer’s protocol. The full protected oligonu-
cleotides were cleaved from the controlled pore-glass
(CPG) support with 27% aqueous NH3 solution at 55 8C
for 8 h. The S-benzoyl group was cleaved at the same time
by ammonia solution. The crude DMTr-DNA was purified
and detritylated by an OPC protocol, and then freeze-dried
immediately. The yields of the oligonucleotides were
determined by a comparison of UV absorption at 260 nm
with nearest-neighbor parameters and the molar extinction
coefficient of the core sequence. Purity was analyzed by
reversed-phase HPLC (C18, 0–10% MeCN in 0.1 M-TEAA
buffer pH 7.4, at 260 nm).