1644
Y.-S. Hon, C.-H. Hsieh, and H.-F. Chen
at 2788C. After the addition, the cooling bath was removed, and the reaction
mixture was stirred at rt. The reaction was completed in 1.5 h, and the reaction
mixture was concentrated. To the crude mixture, ether was added, and most of
the ammonium salts were precipitated out. After filtration, the filtrate was con-
centrated and chromatographed on the silica-gel column to give the desired
acrolein 22 (564 mg, 1.28 mmol) as a colorless oil in 78% yield. TLC
Rf ¼ 0.43 (hexane/EtOAc ¼ 10:1); 1H NMR (CDCl3, 400 MHz) d 9.50
(s, 1H, CHO), 6.40 (s, 1H, -C55CH2), 6.16 (s, 1H, -C55CH2), 5.15 (td,
J ¼ 8.1 and 3.7 Hz, 1H, -CHOAc), 3.74 (dd, J ¼ 10.0 and 6.3 Hz, 1H, -
CH2OTBS), 3.61 (dd, J ¼ 10.0 and 4.4 Hz, 1H, -CH2OTBS), 3.10–3.15
(m, 1H), 2.03 (s, 3H, -COCH3), 1.22–1.56 (m, 20H), 0.80–0.90 (m, 12H),
20.01 [s, 3H, t-BuSi(CH3)2], 20.02 [s, 3H, t-BuSi(CH3)2]; 13C NMR
(CDCl3, 100 MHz)d 193.9 (s), 170.3 (s), 148.5 (s), 136.4, 72.8 (d), 61.5,
41.9 (d), 31.9, 31.8, 29.6, 29.5, 29.4, 29.3, 25.8 (q ꢀ 3), 25.0, 22.6, 21.0
(q), 18.1 (s), 14.1 (q), 25.6 (q), 25.7 (q); IR (thin film, NaCl plates): 2927,
2857, 1739, 1697, 1465, 1369, 1241, 1106, 948, 840, 779 cm21; FAB Mass
(m/z): 441 (Mþ þ 1, 4), 307 (28), 289 (16), 154 (100), 136 (81), 107 (32),
89 (32); HRMS calcd. for C25H49O4Si (Mþ þ H) 441.7395, found: 441.7397.
(3Rꢁ,4Sꢁ)-4-Acetoxy-3-[(tert-butyldimethylsilyloxy)methyl]-
2-methylenepentadecanoic Acid (23)
To a solution of acrolein 22 (200 mg, 0.45 mmol), t-butyl alcohol (2.3 mL), and
2-methyl-2-butene (0.15 mL, 95.2 mg, 1.36 mmol), a solutionof sodium chlorite
(94.4 mg, 1.04 mmol) and sodium dihydrogenphosphate dihydrate (139.4 mg,
0.91 mmol) in 0.7 mL of water was added dropwise. The pale yellow reaction
mixture was stirred at rt for 2.5 h. The reaction mixture was concentrated, the
residue was dissolved in 1.3 mL of water, and this was extracted with 5 mL of
hexane. The aqueous layer was acidified to pH 3 with 2N HCl and extracted
with two 4.2-mL portions of ether. The combined ether layers were washed
with 5 mL of water, dried with Na2SO4, and concentrated to give the crude car-
boxylic acid. The residue was chromatographed on a silica-gel column to give
acrylic acid 23 (149.1 mg, 0.33 mmol) as a colorless oil in 72% yield. TLC
1
Rf ¼ 0.18 (hexane/EtOAc ¼ 10:1); H NMR (CDCl3, 400 MHz) d 6.39 (s),
1H, -C55CH2), 5.66 (s, 1H, -C55CH2), 5.20 (td, J ¼ 8.0 and 3.6 Hz, 1H,
-CHOAc), 3.76 (dd, J ¼ 10.0 and 6.5 Hz, 1H, -CH2OTBS), 3.71 (dd, J ¼ 10.0
and 4.8 Hz, 1H, -CH2OTBS), 3.02–3.07 (m, 1H), 2.03 (s, 3H, -OCOCH3),
1.16–1.29 (m, 20H), 0.85–0.91 (m, 12H), 0.01 [s, 6H, t-BuSi(CH3)2]; 13C
NMR (CDCl3, 100 MHz) d 171.5 (s), 170.8 (s), 139.5 (s), 127.8, 73.5 (d), 62.1,
46.0 (d), 31.9, 29.62, 29.61, 29.57, 29.51, 29.3, 25.8 (q ꢀ 3), 22.7, 21.1 (q),
18.1 (s), 14.1 (q), 25.57 (q), 25.61 (q); IR (thin film, NaCl plates): 3455,
2927, 2857, 1735, 1461, 1249, 1164, 1103, 840, 732 cm21; FAB mass (m/z):
439 (Mþ-17, 2), 397 (Mþ-59, 2), 365 (4), 117 (24), 73 (100); HRMS calcd. for
C25H47O4Si (Mþ-OH) 439.3244, found: 439.3241.