B. Y. Michel, P. Strazewski / Tetrahedron 63 (2007) 9836–9841
9839
oil (5.35 g, 99%): C25H32O4Si (424.62). Rf (petrol ether/
EtOAc 8:1)¼0.40. H NMR (CDCl3): d¼1.10 (s, 9H, Si-
(CH3); 65.69 (C6); 84.60 (C4); 84.81 (C5); 85.04 (C1);
111.97 (C-isopropylidene); 127.62, 127.75 (4C, C-m-Si–
Ph); 129.78, 129.81 (4C, C-p-Si–Ph); 132.73, 132.95 (2C,
C-i-Si–Ph); 134.44 (C2); 135.52, 135.71 (4C, C-o-Si–Ph);
135.77 (C3). MS (ESI+): m/z¼447.2 [M+Na]+.
1
C(CH3)3); 1.36 (s, 3H, CH3); 1.49 (s, 3H, CH3); 4.24 (d,
1H, J¼18.8, HA2); 4.49 (d, 1H, J¼18.8, HB2); 4.86 (m,
2
2
3
2
2H, H4, H5); 5.12 (dt, 1H, J¼10.2, J¼1.5, CH]CH2
3
2
cis); 5.32 (dt, 1H, J¼16.5, J¼1.5, CH]CH2 trans); 5.43
(m, 1H, CH]CH2); 7.37–7.66 (m, 10H, H-Ar). 13C NMR
(CDCl3): d¼19.22 (Si–C(CH3)3); 24.81, 26.75 (CH3);
26.75 (Si–C(CH3)3); 69.00 (C2); 78.31 (C5); 81.75 (C4);
110.30 (C-isopropylidene), 119.03 (CH]CH2); 127.77,
128.82 (4C, C-m-Si–Ph); 129.94 (4C, C–p-Si–Ph); 132.36
(CH]CH2); 132.55 (4C, C-i-Si–Ph); 135.52, 135.56
(4C, C–o-Si–Ph); 205.59 (C1). MS (ESI+): m/z¼447.2
[M+Na]+.
4.2.6. (4R,5R)-(D)-3-tert-Butyldiphenylsilyloxymethyl-
4,5-O,O-isopropylidene-2-cyclopentenone (8). A solution
˚
of allylic alcohol 7 (940 mg, 2.21 mmol), 4 A molecular
sieves (1.82 g), and pyridinium dichromate (2.55 g,
6.64 mmol) in DMF (8 mL) was stirred at room temperature
for 2 days. The reaction mixture was directly purified by sil-
ica gel column chromatography (CyHex/EtOAc 8:1, 7:1,
6:1) to give the cyclopentenone 8 (7.88 g, 90%) as a colorless
oil: C25H30O4Si (422.59). Rf (CyHex/EtOAc 7:1)¼0.25.
[a]2D7 6.2 (c 2.29, CH2Cl2).11 1H NMR (CDCl3): d¼1.09 (s,
9H, Si-C(CH3)3); 1.33 (s, 3H, CH3); 1.35 (s, 3H, CH3);
4.2.4. (1R,4S,5S)-(D)-1-(2,2-Dimethyl-5-vinyl-1,3-dioxo-
lan-4-yl)-1-(tert-butyldiphenylsilyloxymethyl)-2-propen-
1-ol (6). To a stirred solution of 5 (8.69 g, 20.47 mmol) in
THF (90 mL) was added dropwise vinylmagnesium bro-
mide (40.93 mL, 40.93 mmol, 1 M in THF) at ꢀ78 ꢁC,
and the reaction mixture was stirred for 1 h at the same
temperature. It was quenched by saturated ammonium
chloride solution and brine and extracted with ethyl ace-
tate. The organic layer was dried over magnesium sulfate,
filtered and evaporated under reduced pressure. The result-
ing oil was purified by silica gel column chromatography
(CyHex/EtOAc 12:1) to give the allylic alcohol 6 (8.90 g,
96%) as a colorless oil: C27H36O4Si (452.67). Rf (CyHex/
EtOAc 12:1)¼0.33. 1H NMR (CDCl3): d¼1.08 (s, 9H,
Si-C(CH3)3); 1.40 (s, 3H, CH3); 1.50 (s, 3H, CH3); 2.81
(s, 1H, OH); 3.48 (d, 1H, 2J¼9.9, HA6); 3.80 (d, 1H,
2J¼9.9, HB6); 4.47 (d, 1H, 3J¼6.9, H4); 4.68
(‘t’¼dd, 1H, 3J¼7.5, 7.8, H5); 5.14 (dt, 1H, 3J¼9.9,
2J¼1.2, CH]CH2 cis); 5.25 (dd, 1H, 3J¼11.7, 2J¼1.5,
3
3
4.49 (dd, 1H, J¼1.2, 2J¼18.9, HA6); 4.49 (d, 1H, J¼5.6,
H5); 4.69 (dd, 1H, 3J¼1.8, 2J¼18.9, HB6); 4.98 (d,
3
1H, J¼5.6, H4); 6.33 (s, 1H, H2); 7.36–7.73 (m, 10H, H-
Ar). 13C NMR (CDCl3): d¼19.18 (Si–C(CH3)3); 26.18
(CH3); 26.66 (Si–C(CH3)3); 27.36 (CH3); 62.37 (C6);
77.63 (C4); 77.97 (C5); 115.33 (C-isopropylidene); 127.80
(C2); 127.86 (4C, C-m-Si–Ph); 129.99 (4C, C-p-Si–Ph);
132.48, 132.55 (2C, C-i-Si–Ph); 135.38 (4C, C-o-Si–Ph);
176.77 (C3); 201.67 (C1). MS (ESI+): m/z¼866.9
[2M+Na]+.
4.2.7. (1S,4R,5S)-4,5-O,O-Isopropylidene-3-(tert-butyl-
diphenylsilyloxymethyl)-2-cyclopenten-1-ol (9). Sodium
borohydride (220 mg, 5.82 mmol) was added portionwise
to a solution of cyclopentenone 8 (1.585 g, 3.75 mmol)
and
cerium(III) chloride
heptahydrate
(1.198 g,
3.15 mmol) in methanol (7 mL), while the temperature
was maintained between 0 and 5 ꢁC. After 30 min, acetic
acid was carefully added to adjust to pH 5. Water (7 mL)
was added and the reaction mixture was extracted with
ether. The organic layer was washed with brine and dried
over anhydrous magnesium sulfate. The solvents were re-
moved under reduced pressure and the residue was purified
by silica gel column chromatography (CyHex/EtOAc 9:1)
to give the allylic alcohol 9 (1.61 g, 99%) as a colorless
oil: C25H32O4Si (424.62). Rf (CyHex/EtOAc 9:1)¼0.25.
1H NMR (CDCl3): d¼1.07 (s, 9H, Si–C(CH3)3); 1.33
(s, 3H, CH3); 1.35 (s, 3H, CH3); 2.68 (d, 1H, 3J¼9.9,
3
2
H3 cis); 5.26 (dt, 1H, J¼16.8, J¼1.2, CH]CH2 trans);
3
2
5.44 (dd, 1H, J¼17.4, J¼1.5, H3 trans); 6.11 (m, 2H,
H2, CH]CH2); 7.36–7.70 (m, 10H, H-Ar). 13C NMR
(CDCl3): d¼19.32 (Si–C(CH3)3); 24.89 (CH3); 26.81
(Si–C(CH3)3); 27.27 (CH3); 68.44 (C6); 75.46 (C1);
78.67 (C4); 79.35 (C5); 108.19 (C-isopropylidene),
115.95 (C3); 117.76 (CH]CH2); 127.66, 127.72 (4C,
C-m-Si–Ph); 129.77, 129.82 (4C, C-p-Si–Ph), 132.81,
132.87 (2C, C-i-Si–Ph); 135.11 (CH]CH2); 135.59,
135.61 (4C, C–o-Si–Ph); 138.17 (C2). MS (ESI+): m/z¼
475.2 [M+Na]+.
2
2
OH); 4.28 (d, 1H, J¼15.2, HA6); 4.38 (d, 1H, J¼15.2,
HB6); 4.56 (m, 1H, H1); 4.75 (ps t, 1H, 3J¼4.8, 5.9,
H5); 4.86 (d, 1H, 3J¼5.9, H4); 5.84 (d, 1H, 3J¼1.8,
H2); 7.34–7.69 (m, 10H, H-Ar). 13C NMR (CDCl3):
d¼19.22 (Si–C(CH3)3); 26.68 (CH3); 26.77 (Si–C(CH3)3);
27.58 (CH3); 60.77 (C6); 73.25 (C1); 77.94 (C5); 82.77
(C4); 112.44 (C-isopropylidene); 127.66 (4C, C-m-Si–
Ph); 129.26 (C2); 129.71 (4C, C-p-Si–Ph); 133.26 (2C,
C–i-Si–Ph); 135.50 (4C, C–o-Si–Ph); 145.23 (C3);
HRMS (ESI+): m/z¼447.1968 (calculated for [M+Na]+:
447.1967).
4.2.5. (1R,4S,5S)-(D)-4,5-O,O-Isopropylidene-1-(tert-
butyl-diphenylsilyloxymethyl)-2-cyclopenten-1-ol (7).
To a stirred solution of 6 (8.90 g, 19.66 mmol) in CH2Cl2
(65 mL) was added Neolyst dichlorideÔ (364 mg,
0.39 mmol) and the reaction mixture was stirred at room
temperature for 2 days. The volatiles were removed under re-
duced pressure and the residue was purified by silica gel col-
umn chromatography (CyHex/EtOAc 7:1, 6:1, 5:1) to give
the allylic alcohol 7 (7.88 g, 95%) as a colorless oil:
C25H32O4Si (424.62). Rf (CyHex/EtOAc 6:1)¼0.30. 1H
NMR (CDCl3): d¼1.10 (9H, Si-C(CH3)3); 1.28 (s, 3H,
CH3); 1.34 (s, 3H, CH3); 3.29 (s, 1H, OH); 3.71 (d,
1H, 2J¼10.1, HA6); 4.03 (d, 1H, 2J¼10.1, HB6); 4.55
4.2.8. N6,N6,9-N-Tris-(tert-butoxycarbonyl)adenine (11).
To a stirred suspension of adenine (300 mg, 2.22 mmol)
and DMAP (82 mg, 0.67 mmol) in THF (11 mL) was
added Boc2O (2.00 g, 8.88 mmol). After 20 min, the solu-
tion became clear yellow. The reaction mixture was stirred
overnight at room temperature. Then, the volatiles were
3
3
(d, 1H, J¼5.4, H5); 5.34 (dt, 1H, J¼1.2, 5.4, H4); 5.75
3
3
(dt, 1H, J¼0.9, 5.7, H2); 5.99 (dd, 1H, J¼1.7, 5.7, H3);
7.36–7.76 (m, 10H, H-Ar). 13C NMR (CDCl3): d¼19.30
(Si-C(CH3)3); 26.09 (CH3); 26.79 (Si-C(CH3)3); 27.39