1584
M.-Y. Chang et al. / Tetrahedron 60 (2004) 1581–1585
NMR (75 MHz, CDCl3) d 134.46, 108.80, 54.80, 53.45,
51.36, 44.68.
and evaporated. Purification on silica gel (hexane/ethyl
acetate, 5:1) produced compound 8 (80 mg, 80%) as a
1
colorless oil: IR (CHCl3) 1644 cm21; H NMR (300 MHz,
4.1.2. cis-endo-3,5-Dimethoxy-4-oxa-tricyclo[5.2.1.02,6]-
decan-8-one (5). To a mixture of olefin 7 (4.33 g,
22.1 mmol) and sodium borohydride (1.05 g, 26.5 mmol)
in THF (60 mL) was added carefully dimethyl sulfate
(2.3 mL, 3.06 g, 24.3 mmol) in THF (40 mL) in an ice bath.
The mixture was stirred at room temperature for 2 h.
Oxidation was carried out by dropwise addition of hydrogen
peroxide solution (35%, 20 mL)/3 N sodium hydroxide
(10 mL)/water (10 mL) (vol.¼2/2/1). The mixture was held
an additional 1 h at reflux temperature, cooled and extracted
with ethyl acetate (3£30 mL). After separation, the organic
layers were dried, filtrated and evaporated to yield the crude
alcohol. The crude alcohol in dichloromethane (40 mL) was
added to a mixture of pyridinium chlorochromate (7.2 g,
34.9 mmol) and Celite (10 g) in dichloromethane (60 mL).
After being stirred at room temperature for 4 h, the mixture
was diluted with ethyl acetate (20 mL) and filtered through a
short silica gel column. The filtrate was dried, filtered and
concentrated to produce crude ketone. Purification on silica
gel (hexane/ethyl acetate, 2:1) afforded 5 (2.9 g, 62%) as a
solid. Mp 76–78 8C; IR (CHCl3) 1745, 1641 cm21; EI-MS
C11H16O4 m/z (%)¼212 (Mþ, 1), 181 (41), 152 (78), 110
(93), 79 (100); HRMS (EI, Mþ) calcd for C11H16O4
CDCl3) d 5.70–5.63 (m, 2H), 4.77 (s, 1H), 4.64 (dd, J¼2.7,
8.7 Hz, 1H), 3.47 (s, 3H), 3.39 (s, 3H), 3.50–3.34 (m, 2H),
3.22–3.18 (m, 1H), 2.87–2.80 (m, 1H), 1.90–1.70 (m, 2H);
13C NMR (75 MHz, CDCl3) d 136.98, 129.98, 104.96,
101.83, 95.64, 58.28, 55.90, 54.74, 41.29, 36.92, 30.95.
4.1.5. Perhydro-1,7-dioxafuro[1,2,3-cd]isobenzofuran-
2,6-dione (9). To a solution of m-chloroperoxybenzoic
acid (860 mg, 5.0 mmol) in dichloromethane (10 mL) and
diethyl ether (1 mL) at rt was added boron trifluoride
etherate (1 M, 2.1 mL, 2.1 mmol). The solution was heated
to 60 8C for 10 min, and then a solution of 8 (150 mg,
0.7 mmol) in dichloromethane (5 mL) was added dropwise
for 5 min. The reaction mixture was reacted at reflux
temperature for 2 h. And the mixture was cooled to 0 8C and
poured into saturated aqueous sodium bicarbonate solution
(3 mL). The organic layers were washed with aqueous
sodium bicarbonate solution (10 mL) and then dried, filtered
and evaporated. Without further purification, the unstable
product (100 mg) in ethyl acetate (10 mL) was stirred under
1 atm of hydrogen at room temperature with 10% palladium
on activated carbon as catalyst (10 mg) for 2 h. Filtration
through a short plug of Celite and washing with ethyl
acetate (3£10 mL) resulted in the desired crude compound.
Purification on silica gel (hexane/ethyl acetate, 1:1)
produced tricyclic bislactone 9 (92 mg, 72%) as a colorless
solid: mp 99–100 8C; IR (CHCl3) 1770, 1130 cm21; HRMS
(EI, Mþþ1) calcd for C9H11O4 183.0657, found 183.0657;
1H NMR (300 MHz, CDCl3) d 6.25 (d, J¼6.6 Hz, 1H),
3.40–3.20 (m, 2H), 2.75–2.56 (m, 2H), 2.35–2.21 (m, 3H),
2.10–1.95 (m, 1H), 1.70–1.60 (m, 1H); 13C NMR
(125 MHz, CDCl3) d 176.39, 167.84, 99.46, 45.34, 42.27,
36.16, 32.70, 32.35, 28.06. Anal. Calcd for C9H10O4: C,
59.34; H, 5.53. Found: C, 59.30; H, 5.74.
1
212.1049, found 212.1055; H NMR (300 MHz, CDCl3) d
4.71 (s, 1H), 4.62 (s, 1H), 3.32 (s, 6H), 2.77–2.73 (m, 2H),
2.62 (br s, 1H), 2.55–2.53 (m, 1H), 1.87–1.83 (m, 2H),
1.59–1.54 (m, 2H); 13C NMR (75 MHz, CDCl3) d 214.91,
107.19, 107.13, 55.41, 55.17, 53.38, 51.77, 49.60, 40.21,
39.55, 36.46. Crystal of 5 was grown by slow diffusion of
ethyl acetate into a solution of 5 in dichloromethane to yield
˚
the prism: primitive orthorhombic, a¼19.096(4) A,
3
˚
˚
˚
b¼10.829(3) A, c¼10.430(4) A, V¼2157.0(9) A , Z¼8,
dcalcd¼1.307 g/cm3, F(000)¼912.00, 2u range 25 (16.8–
23.08).
4.1.3. (1,3-Dimethoxy-3,3a,4,6a-tetrahydro-1H-cyclo-
pental[c]furan-4-yl)acetaldehyde (4). Ketone (0.2 g,
0.94 mmol) dissolved in benzene (200 mL) free of oxygen
was irradiated under a nitrogen atmosphere with a UV lamp
(l.310 nm), using a pyrex glass filter at room temperature
for 15 h. The solvent was evaporated to afford crude
product. Purification on silica gel (hexane/ethyl acetate, 4:1)
afforded 4 (0.18 g, 90%) as a solid: IR (CHCl3) 1707,
1639 cm21; EI-MS C11H16O4 m/z (%)¼212 (Mþ, 1), 181
(20), 149 (43), 108 (100); HRMS (EI, Mþ) calcd for
4.1.6. (1,3-Dimethoxy-hexahydro-cyclopenta[c]furan-4-
yl)-acetaldehyde (10). Olefin 4 (0.38 g, 1.79 mmol) was
dissolved in ethyl acetate (10 mL) and 10% palladium on
activated carbon as catalyst was added. Then hydrogen was
bubbled into the mixture for 10 min, and stirred at room
temperature for 3 h. Filtration through a short plug of Celite
and washing with ethyl acetate (3£10 mL) resulted in the
desired saturated compound (0.31 g, 83%): IR (CHCl3)
1739 cm21; FAB-MS C11H18O4 m/z (%)¼213 (Mþþ1, 10),
199 (100); 1H NMR (500 MHz, CDCl3) d 9.75 (s, 1H), 4.78
(s, 1H), 4.72 (s, 1H), 3.35 (s, 3H), 3.34 (s, 3H), 2.75–2.63
(m, 3H), 2.51–2.35 (m, 2H), 1.76–1.74 (m, 2H), 1.64–1.60
(m, 1H), 1.11–1.06 (m, 1H); 13C NMR (125 MHz, CDCl3)
d 201.09, 113.07, 107.83, 55.31, 54.95, 52.34, 49.09, 45.51,
36.15, 30.93, 29.40. A solution of resulting aldehyde
(200 mg, 0.93 mmol) was added to a mixture of diethyl-
amine (200 mg, 2.8 mmol) and dibromomethane (10 mL)
and the reaction mixture was heated to 55 8C for 2 h and
cooled to room temperature. The reaction mixture was
evaporated and purified on silica gel (hexane/ethyl acetate,
4:1) to produce olefin 10 (194 mg, 92%) as a colorless oil:
IR (CHCl3) 1648 cm21; EI-MS C12H18O4 m/z (%)¼225
(Mþþ1, 1), 195 (93), 134 (100); HRMS (EI, Mþ) calcd for
1
C11H16O4 212.1049, found 212.1060; H NMR (300 MHz,
CDCl3) d 9.84 (t, J¼1.4 Hz, 1H), 5.77–5.63 (m, 2H), 4.88
(d, J¼2.1 Hz, 1H), 4.87 (s, 1H), 3.42 (s, 3H), 3.40 (s, 3H),
3.05 (td, J¼1.8, 8.1 Hz, 1H), 2.72 (ddd, J¼1.5, 6.9, 15.6 Hz,
1H), 2.58 (ddd, J¼1.5, 6.9, 15.6 Hz, 1H); 13C NMR
(75 MHz, CDCl3) d 200.71, 134.98, 130.17, 109.59,
108.49, 57.85, 55.48, 55.19, 49.82, 45.47, 40.56.
4.1.4. 2,6-Dimethoxy-2a,4a,5,6,7a,7b-hexahhydro-2H-
1,7-dioxacyclopenta[cd]indene (8). A mixture of aldehyde
4 and p-toluenesufonic acid (10 mg) in methanol (40 mL)
was stirred for 8 h at room temperature. After removing the
solvents, the residue was extracted with ethyl acetate
(3£10 mL) and water (5 mL) and the combined organic
layers were washed with brine (2£20 mL), dried, filtered
1
C12H18O4 226.1205, found 226.1212; H NMR (500 MHz,
CDCl3) d 9.59 (s, 1H), 6.30 (s, 1H), 6.17 (s, 1H), 4.78 (s,