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X.-X. Shi et al. / Tetrahedron: Asymmetry 15 (2004) 2327–2331
5H), 3.09 (br s, 2H), 3.28–3.34 (m, 1H), 3.55–3.61 (m,
1H), 4.26 (AB quartet, J ¼ 12:6 Hz, 2H), 4.86 (t,
J ¼ 6:5 Hz, 1H), 7.30–7.50 (m, 6H), 7.61–7.72 (m, 4H).
13C NMR (400 MHz, CDCl3) d 19.21, 24.39, 27.05,
27.52, 29.11, 51.24, 55.83, 59.51, 59.55, 77.34, 127.66,
127.78, 129.86, 129.95, 133.36, 134.02, 135.94, 136.08,
141.48, 145.52. MS (m=z) 500 (Mþ). IR (neat) 3333 (br),
5.7 Hz, 1H), 4.79 (AB quartet, J ¼ 12:5 Hz, 2H),
7.13–7.25 (m, 6H), 7.54–7.67 (m, 4H). 13C NMR
(300 MHz, C6D6) d 19.04, 19.97, 20.00, 26.84, 26.96,
44.71, 54.95, 61.22, 71.52, 127.87, 127.97, 130.10,
130.16, 132.95, 133.20, 135.93, 138.14, 169.50, 169,69,
170.79, 200.98.
1111 cmÀ1
.
4.7. (1R,4S)-3-(2-Acetoxyethyl)-2-acetoxymethyl-1,4-
bis(tert-butyldiphenylsilyloxy)-2-cyclopenten 8
4.5. (9S)-9-(tert-Butyldiphenylsilyloxy)-8-(2-acetoxy-
ethyl)-7-acetoxymethyl-1,5-dithiaspiro[5,4]dec-7-ene 6
Compound 7 (801 mg, 1.62 mmol) was dissolved in
CH3OH (10 mL), with CeCl3Æ7H2O (1.81 g, 4.85 mmol)
then added to the solution. After stirring at room
temperature for 10 min, the mixture was cooled to
)20 ꢁC, and NaBH4 (306 mg, 8.09 mmol) then added.
The reaction was continued at )20 ꢁC and monitored by
TLC. After the reaction was complete, CH2Cl2 (30 mL)
and water (20 mL) were added. The organic phase was
separated and aqueous phase extracted with CH2Cl2
(2 · 20 mL). Extracts were combined and dried over
MgSO4. Evaporation gave a colorless oil, which was
immediately dissolved in CH2Cl2 (10 mL). tert-Butyldi-
phenylchlorosilane (1.34 g, 4.88 mmol), imidazole
(332 mg, 4.88 mmol), and triethylamine (494 mg,
4.88 mmol) were then added. The mixture was stirred at
room temperature for 32 h after which TLC showed
that the reaction was almost complete. EtOAc (50 mL)
was added, and the organic solution washed succes-
sively with 1 M HCl (15 mL), saturated NaHCO3
(10 mL), and brine (10 mL). The organic layer was
separated and dried over anhydrous MgSO4. Evapora-
tion of solvents gave a crude product, which was care-
fully purified by chromatography to produce pure
(1R,4S)-3-(2-acetoxyethyl)-2-acetoxymethyl-1,4-bis(tert-
butyldiphenylsilyloxy)-2-cyclopenten 8 (953 mg, 1.30
Acetic anhydride (4.1 g, 40.2 mmol) and compound 5
(2.0 g, 4.00 mmol) were dissolved in CH2Cl2 (10 mL) and
cooled to 0 ꢁC. Pyridine (4.74 g, 59.9 mmol) was added
dropwise into the above solution at 0 ꢁC. After the
addition was complete, the ice bath was removed, and
the reaction mixture stirred at room temperature over-
night. The mixture was diluted with CH2Cl2 (60 mL)
and the organic phase washed successively with aqueous
HCl solution (2 M, 25 mL), aqueous K2CO3 solution
(10%, 25 mL), and brine (20 mL). The organic solution
was dried over anhydrous MgSO4. The solvent was
evaporated off, and the residue chromatographed to
afford a colorless oil (9S)-9-(tert-butyldiphenylsilyloxy)-
8-(2-acetoxyethyl)-7-acetoxymethyl-1,5-dithiaspiro[5,4]-
dec-7-ene
6
(2.31 g, 3.96 mmol) in 98% yield.
½a ¼ þ13:2 (c 2.5, CH2Cl2). 1H NMR (300 MHz,
D
CDCl3) d 1.09 (s, 9H), 1.65–1.80 (m, 1H), 1.90–2.05 (m,
1H), 1.98 (s, 3H), 2.08 (s, 3H), 2.31 (dd, J ¼ 6:4 Hz;
12.9 Hz, 1H), 2.52–2.90 (m, 7H), 3.81–3.99 (m, 2H), 4.76
(AB quartet, J ¼ 12:5 Hz, 2H), 4.84 (t, J ¼ 6:6 Hz, 1H),
7.35–7.50 (m, 6H), 7.65–7.73 (m, 4H). 13C NMR
(300 MHz, CDCl3) d 19.17, 20.79, 21.11, 24.33, 25.50,
26.99, 27.35, 29.06, 50.90, 57.55, 59.48, 61.81, 77.10,
127.62, 127.76, 129.82, 129.94, 133.19, 133.93, 135.88,
136.01, 136.50, 147.11, 170.56, 170.63. Anal. Calcd for
C31H40O5S2Si: C, 63.66;H, 6.89. Found: C, 63.60;H,
7.01.
1
mmol) in 80% yield. ½a ¼ À7:4 (c 0.82, CH2Cl2). H
D
NMR (300 MHz, CDCl3) d 1.04 (s, 18H), 1.54–1.65 (m,
1H), 1.80–1.91 (m, 1H), 1.89 (s, 3H), 1.95 (s, 3H), 2.39–
2.50 (m, 1H), 2.55–2.65 (m, 1H), 3.90 (t, J ¼ 6:9 Hz,
2H), 4.34 (t, J ¼ 6:6 Hz, 1H), 4.47 (t, J ¼ 6:5 Hz, 1H),
4.71 (AB quartet, J ¼ 12:1 Hz, 2H), 7.23–7.43 (m, 12H),
7.54–7.61 (m, 8H). 13C NMR (300 MHz, CDCl3) d
19.14, 19.17, 20.79, 20.83, 25.28, 26.97, 27.02, 44.64,
58.04, 62.60, 74.43, 76.03, 127.44, 127.47, 127.50,
127.63, 129.52, 129.58, 129.74, 133.48, 133.68, 134.00,
134.26, 135.88, 135.90, 135.96, 137.54, 142.59, 170.60,
170.65. IR (neat) 1710, 1050 cmÀ1. Anal. Calcd for
C44H54O6Si2: C, 71.89;H, 7.40. Found: C, 71.60;H,
7.21.
4.6. (4S)-3-(2-Acetoxyethyl)-2-acetoxymethyl-4-(tert-
butyldiphenylsilyloxy)-2-cyclo-penten-1-one 7
Compound 6 (1.6 g, 2.74 mmol) was dissolved in anhy-
drous THF (8 mL) and the solution cooled to 0 ꢁC.
Periodic acid (1.8 g, 7.90 mmol) was then added in one
portion. After stirring for 3 min, EtOAc (50 mL) was
added. The organic solution was washed successively
with cold water (15 mL), aqueous Na2SO3 solution
(10%, 20 mL), and brine (15 mL). The organic solu-
tion was dried over MgSO4 and filtered through a thin
layer (5 cm) of Celite. The Celite was then rinsed
twice with EtOAc. After removal of the solvents, the
residue was purified by flash chromatography to pro-
duce pure (4S)-3-(2-acetoxyethyl)-2-acetoxymethyl-4-
(tert-butyldiphenylsilyloxy)-2-cyclopenten-1-one 7 (880
4.8. (7S,9R)-7,9-Bis(tert-butyldiphenylsilyloxy)-3-
oxabicyclo[4,3,0]non-1-en-2-one 9
To a solution of compound 8 (950 mg, 1.29 mmol) in
solvent (CH3OH–H2O ¼ 9:1, 6 mL) was added
LiOHÆH2O (217 mg, 5.17 mmol). After stirring at room
temperature for 30 min, water (20 mL) was added, and
the aqueous solution extracted with EtOAc (2 · 20 mL).
The combined organic extracts were then dried with
anhydrous Na2SO4. Evaporation of solvents gave a pale
yellow oil, which was next dissolved in CH2Cl2 (50 mL).
mg, 1.78 mmol) in 65% yield. ½a ¼ þ19:5 (c 0.84,
D
1
CH2Cl2). H NMR (300 MHz, C6D6) d 1.08 (s, 9H),
1.59 (s, 3H), 1.65 (s, 3H), 2.17 (dd, J ¼ 6:0 Hz;18.0 Hz,
1H), 2.28 (dd, J ¼ 2:8 Hz;18.0 Hz, 1H), 2.63–2.78 (m,
2H), 3.92 (t, J ¼ 6:8 Hz, 2H), 4.53 (dd, J ¼ 2:6 Hz;