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G. V. M. Sharma, K. Krishnudu / Tetrahedron: Asymmetry 10 (1999) 869–875
temperature for 1 h. It was recooled to 0°C, treated with methyl iodide (0.86 g, 6.4 mmol) and stirred at
room temperature for 1 h. The reaction mixture was quenched with aq. ammonium chloride solution and
extracted with ether. The organic layer was washed with water, brine and dried (Na2SO4). Evaporation
of solvent and purification of residue by column chromatography (silica gel, 60–120 mesh, 50:1, pet.
ether:ethyl acetate) afforded 7 (1.18 g) in 92% yield as a syrup. First eluted was the α anomer, 1H NMR
0
0
0
(CDCl3): δ 0.80 (t, 3H, J=7.9 Hz, CH3), 1.15–1.5 (m, 18H), 2.36 (t, 1H, J1 ,3 =2.1 Hz, H-1 ), 2.55 (s,
3H, SCH3), 3.39 (s, 3H, OCH3), 4.2–4.35 (m, 4H, H-2,30,4), 4.94 (d, 1H, J1,2=4.1 Hz, H-1), 6.03 (d, 1H,
J
3,4=5.0 Hz, H-3); IR (neat): 3120 and 2135 cm−1; [α]D +88.0 (c 0.7, CHCl3). Eluted second was the β
anomer, 1H NMR (CDCl3): δ 0.86 (t, 3H, J=8.1 Hz, CH3), 1.2–1.7 (m, 18H), 2.38 (t, 1H, J1 ,3 =2.0 Hz,
H-10), 2.52 (s, 3H, SCH3), 3.36 (s, 3H, OCH3), 4.1 (s, 1H, H-2), 4.25–4.35 (m, 3H, H-30,4), 4.82 (s, 1H,
H-1), 5.77 (d, 1H, J3,4=4.4 Hz, H-3); [α]D −38.85 (c 0.35, CHCl3).
0
0
4.6. (3aR,4R,6aR)-4-n-Decyl-6-methoxy-3-methylidenehexahydro[3,4-b]furan or (1R,4R,5R)-4-n-
decyl-2-methoxy-6-methylidene-3,8-dioxa-bicyclo[3.3.0]octane 6
A solution of 7 (1 g, 2.48 mmol) in dry benzene (15 mL) containing AIBN under nitrogen atmosphere
was heated at reflux and treated with tributyl tin hydride (1.43 g, 4.97 mmol). After 8 h, benzene was
evaporated and the residue was purified by column chromatography (silica gel, 60–120 mesh, 20:1, pet.
ether:ethyl acetate) to afford 6 (0.49 g) in 67% yield as a syrup. First eluted was the α anomer, 1H NMR
(CDCl3): δ 0.89 (t, 3H, J=8.2 Hz, CH3), 1.15–1.75 (m, 18H), 2.88 (br.t, 1H, J3a,4=J3a,6a=8.2 Hz, H-3a),
3.38 (s, 3H, OCH3), 3.82 (q, 1H, J3a,4 8.2, J4,CH =2.0 Hz, H-4), 4.3–4.78 (m, 3H, H-2,20,6a), 4.82–4.95
2
(m, 3H, H-6, vinylic); [α]D +48.37 (c 0.215, CHCl3). Analysis calcd for C18H32O3: C, 72.92; H, 10.88;
1
found: C, 72.84; H, 10.79%. Eluted second was the β anomer, H NMR (CDCl3): δ 0.88 (t, 3H, J=8.1
Hz, CH3), 1.15–1.65 (m, 18H), 2.9 (br.t, 1H, J=4.0 Hz, H-3a), 3.22 (s, 3H, OCH3), 3.78–3.9 (m, 1H,
H-4), 4.13–4.4 (m, 3H, H-2,20,6a), 4.79 (s, 1H, H-6), 4.81, 4.82 (2d, 1H each, Jgem=2.6 Hz, vinylic);
[α]D −21.0 (c 0.5, CHCl3). Analysis calcd for Cl8H32O3; found: C, 72.83; H, 10.73%.
4.7. (3aR,4R,6aR)-4-n-Decyl-6-methoxy-3-methylidenetetrahydro[3,4-b]furan-2(3H)-one or methyl-3-
C-(carboxymethylenemethyl)-3,5-dideoxy-5-C-(n-nonyl)-D-ribofuranoside 2,3-γ-lactone 15
A solution of 6 (0.4 g, 1.3 mmol), chromium trioxide (1.3 g, 1.3 mmol) and pyridine (2.1 g, 27.0 mmol)
in dichloromethane (10 mL) was heated at reflux for 4 h. It was cooled to room temperature and decanted.
The residue was dissolved in an aq. sodium bicarbonate solution and extracted with dichloromethane. The
combined organic layers were washed sequentially with an aq. sodium bicarbonate solution, water, 2 N
aq. HCl and brine. It was filtered through a small pad of silica gel and evaporated. The residue was then
purified by column chromatography (silica gel, 60–120 mesh; 10:1, pet. ether:ethyl acetate) to furnish 15
1
(0.3 g) in 73% yield as a syrup. First eluted was the α anomer, H NMR (CDCl3): δ 0.89 (t, 3H, J=7.6
Hz, CH3), 1.2–1.8 (m, 18H), 3.0–3.15 (m, 1H, H-3a), 3.35 (s, 3H, OCH3), 3.87 (q, 1H, J3a,4=5.9Hz, H-4),
4.87 (dd, 1H, J6,6a=4.5, J3a,6a=9.4 Hz, H-6a), 4.98 (d, 1H, J6,6a=4.8 Hz, H-6), 5.53, 6.23 (2d, 1H each,
J
gem=2.7 Hz, vinylic); IR (neat): 1790 and 1650 cm−1; [α]D +93.5 (c 0.385, CHCl3). Analysis calcd for
1
C18H30O4: C, 69.64; H, 9.74; found: C, 69.55; H, 9.63%. Eluted second was the β anomer, H NMR
(CDCl3): δ 0.88 (t, 3H, J=7.7 Hz, CH3), 1.2–1.8 (m, 18H), 3.25–3.4 (m, 4H, H-3a. OCH3), 3.92–4.05
(m, 1H, H-4), 4.79 (d, H, J3a,6a 6.4Hz, H-6a), 5.01 (s, 1H, H-6), 5.6, 6.24 (2s, 1H each, vinylic); IR (neat):
1780 cm−1; [α]D −17.8 (c 0.28, CHCl3). Analysis calcd for C18H30O4; found: C, 69.51; H, 9.61%.