Spino and Allan
183
colourless oil. [α]D = +22.0° (CHCl3, c = 1.82). IR (cm–1):
2.8 Hz), 2.38–2.24 (m, 2H), 1.71–1.40 (m, 6H), 1.20–1.10
(m, 2H), 1.08 (d, 3H, J = 6.6 Hz), 0.86 (d, 3H, J = 6.0 Hz),
0.84 (d, 3H, J = 6.1 Hz). LR-MS (m/z (relative intensity)):
200 (M+ – CO, 5), 197 (5), 87 (100). HR-MS calcd. for
C12H24O2: 200.1776; found: 200.1784.
1
1725, 1658. H NMR (CDCl3) δ: 6.88 (dd, 1H, J = 15.4 and
8.3 Hz), 5.78 (d, 1H J = 15.4 Hz), 3.72 (s, 3H), 3.18 (dd,
1H, J = 8.3 and 5.0 Hz), 2.99 (t, 1H, J = 8.0 Hz), 2.40 (sp,
1H, J = 7.2 Hz), 1.68 (oc, 1H, J = 5.5 Hz), 1.56 (oc, 1H, J =
6.6 Hz), 1.36–1.25 (m, 2H), 1.22–1.10 (m, 1H) 1.15 (s, 9H),
1.00 (d, 3H, J = 6.6 Hz), 0.94–0.85 (m, 1H), 0.88 (d, 3H, J =
6.6 Hz), 0.86 (d, 3H, J = 6.1 Hz). 13C NMR (CDCl3) δ:
167.1 (s), 155.2 (d), 118.7 (d), 72.0 (s), 66.7 (t), 51.1 (q),
43.3 (t), 41.6 (t), 33.8 (d), 31.1 (d), 27.6 (d), 27.3 (q), 20.3
(q), 19.0 (q), 18.2 (q). LR-MS (m/z (relative intensity)): 269
(M+ – Me, 10), 227 (15), 127 (100). HR-MS calcd. for
C16H29O3: 269.2117; found: 269.2119.
Ketone 21
[α]D = –14.1° (CHCl3, c = 1.74) (lit. (4b) value –14.5°,
1
CH2Cl2, c = 1.22). H NMR (CDCl3) δ: 3.66 (s, 3H), 2.61
(sx, 1H, J = 7.1 Hz), 2.40–2.23 (m, 2H), 2.13 (s, 3H), 1.66–
1.39 (m, 5H), 1.15–1.02 (m, 5H), 1.07 (d, 3H, J = 6.6 Hz),
0.83 (d, 6H, J = 6.6 Hz). 13C NMR (CDCl3) δ: 212.9 (s),
174.4 (s), 51.4 (q), 44.7 (d), 44.1 (t), 41.1 (t), 32.7 (t), 31.8
(t), 29.6 (d), 27.9 (d), 19.5 (q), 18.8 (q), 16.9 (q). LR-MS
(m/z (relative intensity)): 243 (MH+, 5), 211 (20), 97 (100).
HR-MS calcd. for C14H27O3: 243.1960; found: 243.1953.
To the α,β-unsaturated ester (426 mg, 1.50 mmol) dis-
solved in EtOH (15 mL) was added 5% Pd/C (75 mg). The
reaction was degassed and flushed with argon 3 times, be-
fore being stirred for 2 h under 1 atm of H2 (1 atm =
101.325 kPa). The mixture was filtered over a pad of Celite,
then concentrated in vacuo. Purification by flash chromatog-
raphy on silica gel (5% EtOAc in hexanes) afforded ester 19
(388 mg, 90%) as a colourless oil. [α]D = –17.9° (CHCl3,
Alcohol 22
To a solution of Roush’s crotyl borane (9.5 mL of a
0.51 mol L–1 solution in toluene, 4.81 mmol) was added 4 Å
molecular sieves (60 mg). This mixture was stirred for
10 min, then cooled to –78 °C. Crude aldehyde 12 in toluene
(2.5 mL) was added dropwise, then stirred for 4 h. NaBH4
(40 mg, 1.05 mmol) in EtOH (1 mL) was added dropwise,
then the reaction was warmed to 0 °C. NaOH (4 mL of a
2 N aqueous solution) was added and stirred for 1.5 h. The
aqueous layer was separated and extracted with Et2O 3
times. The combined organic extracts were dried over anhyd
MgSO4, filtered, and concentrated in vacuo. GC analysis of
the crude product gave a (82:18) diastereoisomer ratio. Puri-
fication by flash chromatography on silica gel (2% EtOAc in
hexanes) afforded the desired pure alcohol 22 (363 mg,
57%) as a colourless oil, and its diastereomer (88 mg, 14%)
1
c = 0.88). IR (cm–1): 1744, 1462. H NMR (CDCl3) δ: 3.66
(s, 3H), 3.19 (dd, 1H J = 8.8 and 5.5 Hz), 3.02 (t, 1H, J =
7.7 Hz), 2.37–2.25 (m, 2H), 1.69 (oc, 1H, J = 6.1 Hz), 1.62–
1.42 (m, 4H), 1.37–1.18 (m, 1H), 1.17 (s, 9H), 1.16–1.06
(m, 1H), 1.02–0.90 (m, 2H), 0.87 (d, 3H, J = 6.6 Hz), 0.83
(d, 3H, J = 6.1 Hz), 0.82 (d, 3H, J = 6.6 Hz). LR-MS (m/z
(relative intensity)): 271 (M+ – Me, 5), 229 (20), 87 (100).
HR-MS calcd. for C16H31O3: 271.2273; found: 271.2265.
Aldehyde 20
To a solution of ester 19 (120 mg, 0.42 mmol) in CH2Cl2
(1.7 mL) was added slowly a solution of B-bromocatechol-
borane (167 mg, 0.84 mmol) in CH2Cl2 (2.0 mL). The reac-
tion was stirred for 15 min, then H2O (5 mL) was added.
Stirring continued for 30 min. The aqueous layer was sepa-
rated and extracted with CH2Cl2 3 times. The combined or-
ganic extracts were washed 3 times with a solution of satd.
aq. Na2CO3, then dried over anhyd MgSO4, filtered, and
concentrated in vacuo. Purification by flash chromatography
on silica gel (20% EtOAc in hexanes) afforded a primary al-
cohol (95 mg, 99%) as a colourless oil. [α]D = –22.6°
1
as a colourless oil. 22: [α]D = –29.3° (CHCl3, c = 2.09). H
NMR (CDCl3) δ: 6.01–5.89 (m, 1H), 5.07–5.02 (m, 2H),
4.37 (s, 1H), 3.49 (dd, 1H, J = 8.8 and 3.9 Hz), 3.37–3.31
(m, 2H), 2.37–2.31 (m, 1H), 1.89–1.77 (m, 1H), 1.20 (s,
9H), 1.10 (d, 3H, J = 6.6. Hz), 0.82 (d, 6H, J = 7.2 Hz). 13C
NMR (CDCl3) δ: 139.9 (d), 114.7 (t), 80.8 (d), 76.5 (s), 67.7
(t), 41.1 (d), 36.2 (d), 27.2 (q), 17.8 (q), 13.5 (q). LR-MS
(m/z (relative intensity)): 185 (M+ – Me, 5), 145 (30), 84
(100). HR-MS calcd. for C11H21O2: 185.1541; found:
185.1546. Minor isomer of alcohol 22: [α]D = +6.6° (CHCl3,
1
(CHCl3, c = 1.46). IR (cm–1): 3347, 1744, 1462. H NMR
1
c = 3.72). H NMR (CDCl3) δ: 5.89-5.77 (m, 1H), 5.13–5.05
(CDCl3) δ: 3.66 (s, 3H), 3.50–3.39 (m, 2H), 2.38–2.24 (m,
2H), 1.77–1.36 (m, 6H), 1.34–1.25 (m, 1H), 1.15–0.87 (m,
3H), 0.92 (d, 3H, J = 6.6 Hz), 0.84 (d, 6H, J = 6.1 Hz). LR-
MS (m/z (relative intensity)): 200 (M+ – CH2O, 20), 157
(20), 83 (100). HR-MS calcd. for C12H24O2: 200.1776;
found: 200.1782.
(m, 2H), 3.52–3.44 (m, 3H), 3.21 (d, 1H, J = 1.7 Hz), 2.26
(sx, 1H, J = 6.6 Hz), 1.90–1.80 (m, 1H), 1.18 (s, 9H), 0.97
(d, 3H, J = 7.2. Hz), 0.94 (d, 3H, J = 6.6 Hz). LR-MS (m/z
(relative intensity)): 201 (MH+, 100), 145 (50). HR-MS
calcd. for C12H25O2: 201.1854; found: 201.1858.
To a solution of this alcohol (157 mg, 0.69 mmol) in wet
CH2Cl2 (3 mL) was added Dess–Martin’s periodinane
(349 mg, 0.82 mmol). The mixture was stirred for 30 min.
The solution was then concentrated in vacuo, diluted with
Et2O, washed with a solution of satd. aq. Na2S2O3, satd. aq.
NaHCO3, and with brine. The combined aqueous extracts
were extracted with Et2O 3 times. The combined organic ex-
tracts were dried over anhyd MgSO4, filtered, and concen-
trated in vacuo. Purification by flash chromatography on
silica gel (10% EtOAc in hexanes) afforded aldehyde 20
Silyl ether 23
To a solution of alcohol 22 (500 mg, 2.5 mmol) in CH2Cl2
(50 mL) at 0 °C was added i-Pr2EtN (0.61 mL, 3.5 mmol)
and TESOTf (0.68 mL, 3.0 mmol). The reaction was stirred
for 30 min. The reaction was quenched by adding a satd. aq.
NaHCO3 solution. The aqueous layer was separated and ex-
tracted with Et2O 3 times. The combined organic extracts
were dried over anhyd MgSO4, filtered, and concentrated in
vacuo. Purification by flash chromatography on silica gel
(2% EtOAc in hexanes) afforded the silyl ether 23 (784 mg,
quantitative) as a colourless oil. [α]D = +16.8° (CHCl3, c =
1
(113 mg, 72%) as a colourless oil. H NMR (CDCl3) δ: 9.59
(d, 1H, J = 2.2. Hz), 3.67 (s, 3H), 2.44 (dq, 1H, J = 7.2 and
© 2004 NRC Canada