Molecules 2014, 19
3809
CDCl3) δ 5.23–5.47 (m, 8H), 4.46 (dd, J = 3 Hz, J = 12 Hz, 1H), 4.08 (dd, J = 6 Hz, J = 12 Hz, 1H),
3.05 (s, 3H), 2.91(m, 1H), 2.73–2.86 (m, 7H), 2.17–2.26 (q, J = 6 Hz 2H), 2.06 (p, J = 9 Hz, 2H),
13
1.55–1.76 (m, 2H), 0.95 (t, J = 9 Hz, 3H). C-NMR (75 MHz, CDCl3) δ 132.29 (CH), 129.42 (CH),
128.84 (CH), 128.60 (CH), 128.43 (CH), 128.10 (CH), 128.00 (CH), 127.19 (CH), 70.06 (CH2), 56.36
(CH), 55.20 (CH), 38.07 (CH3), 31.52 (CH2), 25.84 (CH2), 25.80 (CH2), 25.75 (CH2), 23.78 (CH2),
20.78 (CH2), 14.52 (CH3). IR: 3011, 1652 cm−1. HRMS(EI). Calculated for C19H30O4S: 354.1865;
Found 354.1896.
(6Z,9Z,12Z,15Z)-2,3-dihydroxyoctadeca-6,9,12,15-tetraenyl methanesulfonate (15). To a solution of
the mesylate 14 (1.34 g, 3.8 mmol) in THF (30 mL) a 10% aqueous solution of HClO4 (24 mL) was
added dropwise. The mixture was left stirring overnight at room temperature and quenched with a
pH 7 phosphate buffer (1 M, 100 mL). The reaction mixture was saturated with solid NaCl and
extracted with EtOAc (3 × 25 mL). The combined organic layers was washed with brine (2 × 25 mL)
and dried (MgSO4). The residue obtained by evaporation of the solvent under reduced pressure was
purified by flash chromatography SiO2, hexane-EtOAc (50:50) furnishing the diol mesylate 15 (0.69 g;
1
49%) as a pale yellow oil. H-NMR (300 MHz, CDCl3) δ 5.25–5.46 (m, 8H), 4.34–4.38 (m, 2H),
3.75–3.83 (m, 1H), 3.67–3.75 (m, 1H), 3.05 (s, 3H), 2.57–2.85 (m, 6H), 2.11–2.40 (m, 3H), 1.97–2.11
(m, 2H), 1.46–1.71 (m, 3H), 0.95 (t, J = 9 Hz, 3H). 13C-NMR (75 MHz, CDCl3) δ 132.31 (CH), 129.39
(CH), 129.21 (CH), 128.87 (CH), 128.58 (CH), 128.26 (CH), 128.03 (CH), 127.22 (CH), 72.81 (CH),
71.83 (CH), 71.14 (CH), 37.72 (CH3), 32.61 (CH2), 25.84 (CH2), 25.77 (2×CH2), 23.68 (CH2), 20.78
(CH2), 14.49 (CH3). IR: 3511, 3011, 1650 cm−1. MS (EI) m/z (rel. %): 130 (12), 118 (25), 107 (33),
92 (44), 90 (62), 78 (100), 66 (44), 54 (94). HRMS (EI). Calculated for C19H32O5S: 372.1970;
Found 372.1990.
4Z,7Z,10Z,13Z-hexadecatetraenal (5)—Method 1: To a solution of 5% LiOH in MeOH-H2O (1:1)
(20 mL), acidified with saturated citric acid to pH 4, a solution of the diol mesylate 15 (0.64 g,
1.7 mmol,) in MeOH (2 mL) was added. To the reaction mixture, cooled in ice, NaIO4 (0.45 g, 2.1 mmol)
was added and the mixture was left stirring at room temperature for 1 h. After saturation with solid
NaCl the reaction mixture was extracted with hexane (3 × 25 mL). The extract was washed with water
(2 × 25 mL), brine (2 × 25 mL) and dried (MgSO4). Evaporation under reduced pressure gave the
aldehyde 5 (0.2 g; 50%) as a colorless oil. Spectral data were in agreement with those reported [20].
4Z,7Z,10Z,13Z-hexadecatetraenal (5)—Method 2: t-BuOK (5.5 g, 49 mmol) was added portionwise to
an ice-cooled suspension of (methoxymethyl)triphenylphosphonium chloride (17.83 g, 52 mmol) in
dry THF (100 mL). After stirring for 15 min at 0 °C, a solution of the aldehyde 6 (5.67 g, 26 mmol) in
dry ether (50 mL) was added. The mixture was left stirring at 4 °C overnight. Water (100 mL) was
added and volatile compounds were removed under reduced pressure. The reaction mixture was
extracted with ether (3 × 50 mL) and the extract was concentrated under reduced pressure. The residue
was dissolved in dioxane (225 mL) and cooled to 0 °C. Aq. formic acid (225 mL; 80%) was added and
the mixture was left stirring overnight at room temperature. Water (100 mL) was added and volatile
compounds were removed under reduced pressure. The reaction mixture was extracted with hexane
(3 × 50 mL) and the extract was washed successively with aq. NaHCO3 (2 × 50 mL), water (2 × 50 mL)