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L. Fournier et al. / Tetrahedron 60 (2004) 1659–1663
(200 MHz, CDCl3): d¼9.83 (1H, t, J¼2.4 Hz), 7.40–7.15
(5H, m, H(Ar)), 6.60 (1H, d, J¼15.9 Hz), 6.23 (1H, dd,
J¼15.9, 6.3 Hz), 4.84 (1H, q, J¼6.4 Hz), 2.72 (1H, 1/2
ABMX, JAB¼15.8 Hz, JAM¼6.8 Hz, JAX¼2.6 Hz), 2.63
(1H, 1/2 ABMX, JAB¼15.8 Hz, JBM¼5.1 Hz, JBX¼2.2 Hz),
0.91 (9H, s), 0.11 (3H, s), 0.08 (3H, s). 13C NMR
(75.4 MHz, CDCl3): d¼201.4 (d), 136.4 (s), 131.3 (d),
130.1 (d), 128.6 (d, 2C), 126.5 (2C, d), 127.8 (d), 69.3 (d),
51.6 (t), 25.8 (3C, q), 18.1 (s), 24.2 (q), 25.0 (q).
220.7 (c¼1, CHCl3) (lit.42 [a]D¼220.77 (c¼1.32,
CHCl3)).1H NMR (300 MHz, CDCl3): d¼4.13 (1H, quint,
J¼6.2 Hz), 3.67 (3H, s), 2.44 (2H, d, J¼6.2 Hz), 1.50–1.25
(8H, m), 0.94 (3H, t, J¼5.7 Hz), 0.92 (9H, s), 0.07 (3H, s),
0.04 (3H, s). 13C NMR (62.9 MHz, CDCl3, lit.42): d¼172.2
(s), 69.6 (d), 51.2 (q), 42.6 (t), 37.6 (t), 31.9 (t), 25.7 (3C)
(q), 24.6 (t), 22.5 (t), 17.9 (s), 13.8 (q), 24.6 (q), 24.9 (q).
5.1.6. (R)-(2)-3-(tert-Butyldimethylsilyloxy)octanal (10).
A solution of diisobutylaluminium hydride in toluene
(1.5 M, 1.3 mL, 1.94 mmol) was added dropwise at
285 8C to a stirred solution of the protected ester 9
(507 mg, 1.76 mmol) in dry dichloromethane (9 mL) under
argon. The solution was stirred at 290 8C for 1 h, then
quenched by dropwise addition of saturated aqueous
ammonium chloride (0.5 mL) (T#275 8C). The biphasic
mixture was allowed to warm to room temperature, filtrated
through a short path of silica gel and the filtrate was washed
with dichloromethane. Purification of the crude product by
flash chromatography (petrol/ether: 90/10) yielded aldehyde
10 (447 mg, 1.73 mmol, 98%) as a colourless oil:
[a]D¼25.3 (c¼1.0, CHCl3) (lit.43 [a]D¼25.3 (c¼1.0,
.
1H
5.1.4. (20E)-6-(20-Phenylvinyl)-5,6-dihydro-2H-pyran-2-
one 1 [(6)-goniothalamin 1]. To a solution of aldehyde 5
(653 mg, 2.25 mmol) in ether (16 mL) at 250 8C under
argon, was added trimethylsilylketene
6
(308 mg,
2.7 mmol) in ether (6 mL). A solution of ethyl aluminium
dichloride in hexane (1 M, 2.7 mL, 2.7 mmol) was then
added dropwise at that temperature. The reaction was stirred
for 2 h between 245 and 230 8C. The mixture was then
quenched with water (7 mL) and the aqueous layer extracted
with ether (2£12 mL). The organic phases were dried and
concentrated to yield the corresponding b-lactone 7 as a 81/
10/7/2 (cis/cis/trans/trans) mixture of diastereomers. The
major cis diastereoisomer gave the following 1H NMR
spectroscopic data (300 MHz, CDCl3) recorded on the
mixture d¼7.50–7.24 (5H, m), 6.57 (1H, d, J¼15.9 Hz),
6.17 (1H, dd, J¼15.9; 6.8 Hz), 4.88 (1H, m), 4.48 (1H, m),
3.41 (1H, d, J¼6.3 Hz), 1.95 (2H, m), 0.93 (9H, s), 0.23
(9H, m), 0.12 (6H, s).
CHCl3)) IR (film): n¼1725, 1255, 1101, 836 cm21
NMR (300 MHz, CDCl3): d¼9.81 (1H, t, J¼2.4 Hz), 4.20
(1H, quint, J¼5.8 Hz), 2.52 (2H, dd, J¼5.8, 2.6 Hz), 1.60–
1.33 (8H, m), 0.89 (3H, t, J¼6.0 Hz), 0.86 (9H, s), 0.08 (3H,
s), 0.06 (3H, s). 13C NMR (75.4 MHz, CDCl3): d¼202.0 (d),
68.2 (d), 50.8 (t), 37.8 (t), 31.7 (t), 25.7 (q, 3C), 24.7 (t), 22.5
(t), 17.9 (s), 13.9 (q), 24.5 (q), 24.6 (q).
To a solution of this crude mixture of b-lactones in
acetonitrile (22 mL) was added aqueous HF (5.4 mL). After
15 min stirring at room temperature, the reaction was
extracted with ethyl acetate (4£6 mL). The organic phases
were dried over MgSO4 and concentrated in vacuo. The
residue was purified by flash chromatography (petrol/ethyl
acetate: 75/25) to give (^)-goniothalamin 1 (276 mg,
1.38 mmol, 61%) as a white solid: mp 80 8C (lit. mp18
5.1.7. (R)-(2)-6-Pentyl-5,6-dihydro-2H-pyran-2-one 2
[massoialactone (2)]. To a solution of aldehyde 10
(447 mg, 1.73 mmol) in ether (12 mL) at 250 8C under
argon, was added trimethylsilylketene
6
(237 mg,
2.08 mmol) in ether (3 mL). A solution of ethyl aluminium
dichloride in hexane (1 M, 2.1 mL, 2.08 mmol) was then
added dropwise at that temperature. The reaction was stirred
for 2 h between 245 and 230 8C. The mixture was
quenched with water (5 mL) and the aqueous layer extracted
with ether (2£15 mL). The organic phases were dried and
concentrated in vacuo to yield oxetanones 11 as a mixture of
3 diastereoisomers (cis/trans/trans: 88/9/3). The major cis
1
82 8C) IR (film): n¼1720, 1702, 765, 700 cm21. H NMR
(200 MHz, CDCl3): d¼7.45–7.30 (5H, m), 6.93 (1H, td,
J¼9.9, 4.0 Hz), 6.74 (1H, d, J¼16.3 Hz), 6.28 (1H, dd,
J¼16.0, 6.4 Hz), 6.11 (1H, dt, J¼9.9, 1.8 Hz), 5.13 (1H, q,
J¼7.3 Hz), 2.56 (2H, m). 13C NMR (75.4 MHz, CDCl3):
d¼163.9 (s), 144.6 (d), 135.8 (s), 133.1 (d), 128.7 (2C)(d),
128.3 (d), 126.7 (2C)(d), 125.6 (d), 121.7 (d), 77.9(d), 29.9(t).
1
diastereoisomer gave the following H NMR spectroscopic
data (300 MHz, CDCl3) recorded on the mixture d¼4.80
(1H, ddd, J¼10.6, 6.2, 2.7 Hz), 3.85 (1H, m), 3.38 (1H, d,
J¼6.2 Hz), 1.90–1.20 (10H, m), 0.92 (9H, s), 0.95–0.80
(3H, m), 0.24 (9H, br s), 0.08 (6H, br s).
5.1.5. (R)-(2)-3-(tert-Butyldimethylsilyloxy)octanoic
acid methyl ester (9). A three-necked round bottom flask
with a nitrogen inlet was charged with CuI (1.333 g,
7 mmol) and Et2O (10 mL). The solution was stirred and
cooled at 235 8C before BuLi (1.6 M in hexane, 8.8 mL,
14 mmol) was added. After 1 h, tosylate 8 (486 mg,
1.2 mmol) dissolved in Et2O (7 mL) was added. The
reaction was stopped after 1.5 h (TLC monitoring) by
diluting with Et2O and then adding saturated aqueous
NH4Cl (3.6 mL). The mixture was warmed to room
temperature with stirring before the organic layer was
separated. The aqueous layer was extracted with EtOAc
(3£7 mL), and the combined organic layers were washed
with saturated aqueous NaHCO3 (12 mL) and brine
(12 mL). The organic phase was then dried over Na2SO4
and concentrated in vacuo. The residue was purified by flash
chromatography (petrol/ether: 90/10) to give ester 9
(274 mg, 0.95 mmol, 79%) as a colourless oil: [a]D¼
To a solution of the crude mixture of oxetanones in
acetonitrile (17 mL) was added aqueous HF (4.1 mL). After
4 h stirring at 50 8C, the reaction was extracted with ether
(4£10 mL). The organic phases were dried over MgSO4 and
concentrated in vacuo. The residue was purified by flash
chromatography (petrol/ethyl acetate: 75/25) to give (2)-
massoialactone 2 (178 mg, 1.06 mmol, 61%, with 99% ee):
[a]D¼2110.7 (c¼1, CHCl3). [Lit.31 [a]D¼2110.7 (c¼1,
.
1H NMR
CHCl3)]. IR (film): n¼1725, 1630 cm21
(500 MHz, CDCl3): d¼6.85 (1H, ddd, J¼9.7, 5.4, 3.1 Hz),
6.00 (1H, ddd, J¼9.7, 2.3, 1.3 Hz), 4.39 (1H, ddt, J¼10.5,
7.4, 5.3 Hz), 2.31 (2H, m), 1.80–1.45 (4H, m), 1.42–1.25
(4H, m), 0.90 (3H, t, J¼6.9 Hz). 13C NMR (50.3 MHz,
CDCl3): d¼164.6 (s), 145.0 (d), 121.4 (d), 78.0 (d), 34.8 (t),
31.5 (t), 29.3 (t), 24.4 (t), 22.4 (t), 13.9 (q).