564
J. Ghostin et al.
1H-NMR: ꢀ 4.83 (d, J ¼ 9.5 Hz, 1H), 3.66 (s, 3H), 2.34–2.22 (m, 3H), 1.94 (m,
2H), 1.65 (d, J ¼ 1.2 Hz, H3C-6 E or Z), 1.56 (d, J ¼ 1.2 Hz, H3C-6 E or Z), 1.30–1.26
(m, 10H), 0.93 (d, J ¼ 6.6 Hz, H3C-4) and 0.88 (t, J ¼ 6.7 Hz, 3H). 13C-NMR: ꢀ 174.6
(CO), 135.4, 135.2 (C-6 E and Z), 130.6, 129.9 (C-5 E and Z), 51.5 (OCH3), 32.8, 32.4
(C-3 E and Z), 32.3, 32.2 (C-2 E and Z), 32.0 (C-4), 39.8, 31.9, 31.8, 29.5, 29.0, 28.3,
28.0, 22.8 (C-7, C-8, C-9, C-10, C-11), 23.5, 21.7, 21.4, 16.2 (H3C-4 and H3C-6 E and
Z) and 14.2 (C-12). IR: 2927, 1742 cmꢁ1. EIMS m/z: 240 (52) [M]þ, 209 (32)
[M ꢁ OCH3]þ, 166 (41), 155 (79), 123 (75), 109 (78), 97 (86), 83 (90), 69 (100)
and 55 (95).
3.4. (syn Y anti)-Methyl 4,6-dimethyldodecanoate (7)
A solution of methyl 4,6-dimethyldodec-5-enoate (6) (127 mg, 0.53 mmol) in
methanol (3 mL) was hydrogenated over Pd/C (10%, 40 mg) under H2 atmosphere
at room temperature. After 18 h, the solvent was evaporated in vacuo and the solid
residue was purified by flash-chromatography on silica gel (hexane/Et2O, 98 : 2) to
give the saturated ester 7 (126 mg, 0.52 mmol, 98%).
1H-NMR: ꢀ 3.66 (s, 3H), 2.34–2.26 (m, 2H), 1.69–1.03 (m, 16H) and 0.90–0.80
(m, 9H). 13C-NMR: ꢀ 174.7 (C-1), 51.5 (OCH3), 44.9, 44.5 (C-5), 38.0, 37.0, 32.9,
32.1, 32.0, 31.9, 31.8, 29.8, 29.7, 27.1, 27.0, 22.8 (C-2, C-3, C-7, C-8, C-9, C-10, C-
11), 30.0, 30.1, 29.9, 29.8 (C-4 and C-6), 20.2, 20.0, 19.6, 19.2 (H3C-4 and H3C-6) and
14.2 (C-12). IR: 2956, 1744 cmꢁ1. EIMS m/z: 242 (15) [M]þ, 211 (22) [M ꢁ OCH3]þ,
87 (100) [C4H7O2]þ and 74 (51) [C3H6O2]þ.
3.5. (syn Y anti) 4,6-Dimethyldodecan-1-ol (8)
A suspension of LAH (160 mg, 4.21 mmol) in anhydrous diethyl ether (2 mL) was
added at 0ꢂC to 7 (116.8 mg, 0.48 mmol) dissolved in anhydrous diethyl ether (3 mL).
After stirring for 12 h at room temperature, the reaction was quenched with a
saturated aqueous solution of MgSO4 and the aqueous layer extracted with
dichloromethane. The organic fractions were combined, evaporated in vacuo and
purified by flash-chromatography (pentane/Et2O 8 : 2) to yield alcohol 8 (96 mg,
0.45 mmol, 94%) as a colourless oil.
1H-NMR: ꢀ 3.62 (t, J ¼ 6.7 Hz, 2H), 1.59–1.04 (m, 18H) and 0.90–0.80 (m, 9H).
13C-NMR: ꢀ 63.6, 63.5 (C-1), 45.2, 44.9 (C-5), 38.1, 37.0, 34.0, 32.9, 32.1, 30.5, 30.3,
29.9, 29.8, 27.1, 27.0, 22.8 (C-2, C-3, C-7, C-8, C-9, C-10, C-11), 30.2, 30.16, 30.1,
30.0 (C-4 and C-6), 20.4, 20.3, 19.6, 19.5 (H3C-4 and H3C-6) and 14.2 (C-12). IR:
3307, 2957 cmꢁ1. EIMS m/z: 196 (1) [M ꢁ H2O]þ, 181 (2), 168 (12), 153 (30), 112 (65),
111 (72), 110 (39), 97 (29), 83 (70), 69 (100), 57 (88).
3.6. (syn Y anti) 4,6-Dimethyldodecanal (1 Y 2)
Oxalylchloride (57 mL, 0.66 mmol) was added to dimethylsulphoxide (93 mL)
dissolved in CH2Cl2 (1 mL) at ꢁ78ꢂC. After 20 min, 8 (40 mg, 0.187 mmol) dissolved
in CH2Cl2 (1 mL) was added. The solution was stirred for 1 h at ꢁ78ꢂC. Then,
triethylamine (139 mL, 0.98 mmol) was added dropwise. The reaction mixture was
stirred for 2 h at room temperature, quenched with water and extracted with CH2Cl2.