H. Shi et al. / Tetrahedron: Asymmetry 13 (2002) 1423–1428
1427
6H), 5.21 (d, J=1.3 Hz, 1H), 5.28 (d, J=3.6 Hz, 1H),
5.39 (s, 1H), 6.45 (dd, J=1.6 Hz, 5.6 Hz, 1H), 6.50 (s,
2H), 6.52 (dd, J=1.0 Hz, 5.9 Hz, 1H); 13C NMR (63
MHz, CDCl3) l: 48.2, 50.3, 55.9, 60.5, 81.7, 83.5, 84.2,
101.9, 135.9, 136.1, 136.4, 137.6, 153.3, 174.9; IR
(KBr): 3076, 2968, 1764, 1593 cm−1; ESMS m/z (rela-
tive intensity): 659 (2MNa+, 100), 341 (MNa+, 51).
Anal. calcd for C17H18O6: C, 64.14; H, 5.70. Found: C,
63.95; H, 5.61%.
3H), 1.85 (m, 2H), 2.57 (dd, J=7.0, 7.1 Hz, 1H), 2.73
(dd, J=2.1, 7.1 Hz, 1H), 3.07 (t, J=7.1 Hz, 2H), 3.82
(t, J=7.0 Hz, 2H), 3.85 (s, 3H), 3.88 (s, 3H), 3.89 (s,
6H), 3.97 (t, J=6.8 Hz, 2H), 4.40 (s, 1H), 5.14 (s, 1H),
5.19 (d, J=6.1 Hz, 1H), 5.20 (s, 1H), 6.33 (dd, J=1.6,
5.8 Hz, 1H), 6.50 (dd, J=1.5, 5.8 Hz, 1H), 6.62 (s, 2H),
6.87 (d, J=1.5 Hz, 1H), 6.99 (d, J=1.5 Hz, 1H); 13C
NMR (63 MHz, CDCl3) l: −5.3, 10.5, 18.3, 23.5, 25.9,
34.2, 51.7, 53.8, 56.0, 56.3, 60.8, 62.2, 74.5, 79.2, 80.7,
83.1, 83.3, 102.5, 108.7, 117.9, 130.9, 135.0, 137.1,
137.5, 138.8, 145.3, 152.8, 153.4; IR (film): 3075, 2956,
2934, 2878, 2856, 1590, 1462, 1129 cm−1; ESMS m/z
(relative intensity): 682 (MHNa+, 46), 681 (MNa+, 100):
HRESMS calcd for C35H50O8SSiNa+: 681.2893. Found:
681.2893.
4.9. (1R,2S,3R,5S,6R,7S)-4,10-Dioxa-3-[3%%-methoxy-5%%-
(2%%%-t-butyldimethylsilyloxyethanesulfanyl)-4%%-propoxy]-
5-(3%,4%,5%-trimethoxyphenyl)-tricyclo(5.2.1.02,6]dec-8-en-3-
ol, 11
1
To a solution of bromide 2 (620 mg, 1.42 mmol) in
pentane (4 mL) at −78°C was added dropwise a solu-
tion of tert-butyllithium 1.4 M (1.5 mL, 2.135 mmol).
The mixture was stirred for 30 min then treated drop-
wise with a solution of lactone 10 (318 mg, 1 mmol) in
THF anhydrous (4 mL). The mixture was stirred for 30
min at −78°C then quenched with saturated aqueous
NH4Cl solution (10 mL) and allowed to warm to room
temperature. After extraction with ether (3×20 mL, the
combined organic extracts were dried over MgSO4 and
concentrated in vacuo. The residue was purified by
chromatography on silica gel (eluent: petroleum ether/
12%: H NMR (250 MHz, CDCl3) l: 0.05 (s, 6H), 0.89
(s, 9H), 1.06 (t, J=7.4 Hz, 3H), 1.83 (m, 2H), 2.58 (m,
2H), 3.08 (t, J=7.1 Hz, 2H), 3.82 (t, J=7.1 Hz, 2H),
3.86 (s, 3H), 3.87 (s, 3H), 3.91 (s, 6H), 3.95 (t, J=6.8
Hz, 2H), 4.67 (m, 2H), 4.93 (s, 2H), 6.39 (s, 2H), 6.72
(s, 2H), 6.90 (d, J=1.3 Hz, 1H), 6.99 (d, J=1.4 Hz,
1H).
4.11. (2S,5S)-2-(3%,4%,5%-Trimethoxyphenyl)-5-[3%%-
methoxy-5%%-(2%%-t-butyldimethylsilyloxyethanesulfanyl)-
4%%-propoxyphenyl]-2,5-dihydrofuran, 13
1
AcOEt, 6/4) to give lactol 11 (357 mg, 53%): H NMR
The tricyclic compound 12 (250 mg, 0.379 mmol) was
evaporated through a horizontal mullite tube (450°C,
10−3 torr) and the thermolysate was collected on a
finger cooled with liquid nitrogen. After warming to
room temperature, the finger was washed with ether
and the resulting solution was concentrated under
reduced pressure. The residue was purified by chro-
matography on silica gel (eluent: petroleum ether/
AcOEt, 80/20) to give dihydrofurane 13 as a colorless
oil (150 mg, 67%): [h]2D0=−189 (c 1.07, CHCl3); 1H
NMR (250 MHz, CDCl3) l: 0.06 (s, 6H), 0.90 (s, 9H),
1.05 (t, J=7.4 Hz, 3H), 1.83 (m, 2H), 3.07 (t, J=7.2
Hz, 2H), 3.81 (t, J=7.2 Hz, 2H), 3.85 (s, 3H), 3.86 (s,
3H), 3.89 (s, 6H), 3.94 (t, J=6.7 Hz, 2H), 5.97 (s, 2H),
6.09 (s, 2H), 6.61 (s, 2H), 6.76 (d, J=1.4 Hz, 1H), 6.87
(d, J=1.5 Hz, 1H); 13C NMR (63 MHz, CDCl3) l:
−5.3, 10.5, 18.3, 23.5, 25.9, 34.2, 55.9, 56.1, 60.8, 62.2,
74.5, 88.0, 88.2, 103.5, 108.5, 118.0, 130.3, 130.4, 131.5,
136.8, 137.0, 137.7, 145.9, 153.0, 153.4; IR (film): 3075,
2956, 2937, 2879, 2856, 1591, 1463, 1129 cm−1; ESMS
m/z (relative intensity): 614 (MHNa+, 42), 613 (MNa+,
100); HRESMS calcd for C31H46O7SSiNa+: 613.2631.
Found: 613.2631.
(250 MHz, CDCl3) l: 0.04 (s, 6H), 0.86 (s, 9H), 1.06 (t,
J=7.4 Hz, 3H), 1.84 (m, 2H), 2.70 (dd, J=7.8, 8.5 Hz,
1H), 2.87 (d, J=8.8 Hz, 1H), 3.10 (t, J=7.1 Hz, 2H),
3.82 (t, J=7.0 Hz, 2H), 3.87 (s, 3H), 3.88 (s, 3H), 3.91
(s, 6H), 3.96 (t, J=6.8 Hz, 2H), 4.80 (d, J=7.6 Hz,
1H), 4.94 (s, 1H), 5.14 (s, 1H), 5.15 (s, 1H), 6.38 (m,
1H), 6.41 (m, 1H), 6.72 (s, 2H), 7.16 (d, J=1.7 Hz, 1H),
7.28 (d, J=1.6 Hz, 1H); IR (film): 3453, 3084, 2958,
2936, 2881, 2857, 2250, 1737, 1593, 1463, 1129 cm−1;
ESMS m/z (relative intensity): 698 (MHNa+, 45), 697
(MNa+, 100); HRESMS calcd for C35H50O9SSiNa+:
697.2842. Found: 697.2842.
4.10. (1R,2S,3S,5S,6R,7S)-4,10-Dioxa-3-[3%%-methoxy-
5%%-(2-t-butyldimethylsilyloxyethanesulfanyl)-4%%-pro-
poxy]-5-(3%,4%,5%-trimethoxyphenyl)-tricyclo[5.2.1.O2,6]dec-
8-ene, 12
To a solution of lactol 11 (355 mg, 0.526 mmol) and
NaBH3CN (99 mg, 1.58 mmol) in anhydrous 2,2,2-tri-
fluoroethanol (9 mL) was added dropwise dichloro-
acetic acid (130 mL, 1.58 mmol) at −25°C. The mixture
was stirred for 30 min and quenched with saturated
aqueous NaHCO3 solution (10 mL), extracted with
ether (4×20 mL). The organic phases were dried over
MgSO4 and concentrated in vacuo. The residue was
purified by chromatography on silica gel (eluent:
petroleum ether/AcOEt, 70/30) to give ‘trans’ com-
pound 12 (258 mg, 75%) and ‘cis’ compound 12% (14
mg, 4%) both as colorless oils.
4.12. (2S,5S)-2-(3%,4%,5%-Trimethoxyphenyl)-5-[3%%-
methoxy-5%%-(2%%-t-butyldimethylsilyloxyethanesulfanyl)-
4%%-propoxyphenyl]tetrahydrofuran, 14
A solution of dihydrofuran 13 (240 mg, 0.406 mmol) in
ethyl acetate (4 mL) was hydrogenated over 5% Pt/C
(50 mg) at atmospheric pressure. After filtration, the
catalyst was washed with ethylacetate (2×5 mL) and the
filtrate was concentrated in vacuo. The residue was
purified by chromatography on silica gel (eluent:
1
12: [h]2D0=−53 (c 0.75, CHCl3); H NMR (250 MHz,
CDCl3) l: 0.06 (s, 6H), 0.89 (s, 9H), 1.06 (t, J=7.4 Hz,