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Helvetica Chimica Acta – Vol. 93 (2010)
(300 MHz): 7.20 – 7.37 (m, 5 arom. H); 5.79 (s, HꢀC(5’)); 5.32 (q, J ¼ 6.6, HꢀC(7’)); 4.51 (dddd, J ¼ 9.6,
7.5, 3.3, 2.4, HꢀC(4)); 4.24 (d, J ¼ 7.8, HꢀC(3’)); 4.03 – 4.15 (m, CH2(5), HꢀC(2’)); 3.27 (dd, J ¼ 13.2,
3.3, 1 H, PhCH2); 2.75 (dd, J ¼ 13.2, 9.9, 1 H, PhCH2); 1.73 (d, J ¼ 1.2, MeꢀC(4’)); 1.69 (s, MeꢀC(6’));
1.65 (d, J ¼ 6.9, Me(8’)); 1.24 (d, J ¼ 6.9, MeꢀC(2’)); 0.94 (t, J ¼ 8.1, (MeCH2)3Si); 0.58 (q, J ¼ 8.1,
.
(MeCH2)3Si). EI-MS: 471 (Mþ ), 442 ([M ꢀ Et]þ), 339 ([M ꢀ TESOH]þ), 318, 294, 262 239, 200, 115, 91.
.
HR-EI-MS: 471.2805 (Mþ , C27H41NO4Siþ; calc. 471.2804).
(4R,2’R,3’R,4’E,6’E)-Isomer (ent-syn-10). In the same manner as described for syn-10, ent-syn-5
(730 mg, 2.04 mmol) afforded ent-syn-10 (962 mg, 2.04 mmol, quant.). Colorless oil. [a]2D4 ¼ ꢀ59 (c ¼
0.55, Et2O). HR-FAB-MS: 494.2709 ([M þ Na]þ, C27H41NNaO4Siþ; calc. 494.2702).
S-Ethyl (2S,3S,4E,6E)-2,4,6-Trimethyl-3-[(triethylsilyl)oxy]octa-4,6-dienethioate (syn-11). To a soln.
of EtSH (179 ml, 2.42 mmol) in THF (9 ml) was added dropwise BuLi in hexane (1.6m, 1.0 ml,
1.615 mmol) at ꢀ 788 under Ar, and the mixture was stirred for 15 min. Then, to the mixture was added a
soln. of syn-10 (164 mg, 0.35 mmol) in THF (2 ml). The mixture was gradually warmed to 08 and stirred
with sat. aq. NaHCO3 soln., and the resulting mixture was extracted with Et2O. The combined extract was
washed with brine, dried (MgSO4), and concentrated in vacuo. CC (SiO2; hexane/AcOEt 10 :1) gave syn-
11 (288 mg, 0.808 mmol, quant.). Colorless oil. [a]2D4 ¼ þ47 (c ¼ 0.43, Et2O). Rf (hexane/AcOEt 6 :1)
0.61. IR (film): 2950m, 2875s, 1680s (C¼O), 1460s (C¼O), 1240s, 1080s, 1000s, 960s, 740s. 1H-NMR
(300 MHz): 5.74 (s, HꢀC(5)); 5.33 (q, J ¼ 6.6, HꢀC(7)); 4.15 (d, J ¼ 7.2, HꢀC(3)); 2.77 – 2.88 (m,
MeCH2S); 2.72 (dq, J ¼ 9.0, 7.5, HꢀC(2)); 1.74 (s, MeꢀC(4)); 1.67 (s, MeꢀC(6)); 1.66 (d, J ¼ 9.9,
Me(8)); 1.20 (d, J ¼ 7.2, MeꢀC(2)); 1.19 (t, J ¼ 7.2, MeCH2S); 0.93 (t, J ¼ 7.8, (MeCH2)3Si); 0.57 (q, J ¼
7.8, (MeCH2)3Si). 13C-NMR (150 MHz): 201.8; 134.3; 132.8; 131.4; 124.2; 80.4; 53.5; 23.0; 16.4; 14.6;
.
13.7; 13.6; 13.0; 6.83; 6.79; 6.38; 4.77. EI-MS: 356 (Mþ ), 327 ([M ꢀ Et]þ), 291, 239, 217, 189, 161, 133, 115
.
([Et3Si]þ), 87. HR-EI-MS: 356.2207 (Mþ , C19H36O2SSiþ; calc. 356.2205).
(2R,3R,4E,6E)-Isomer (ent-syn-11). In the same manner as described for syn-11, ent-syn-10 (681 mg,
1.44 mmol) afforded ent-syn-11 (514 mg, 1.44 mmol, quant.). Colorless oil. [a]2D4 ¼ ꢀ44 (c ¼ 0.25, Et2O).
HR-FAB-MS: 357.2288 ([M þ H]þ, C19H37O2SSiþ; calc. 357.2284).
(2S,3S,4E,6E)-2,4,6-Trimethyl-3-[(triethylsilyl)oxy]octa-4,6-dienal (syn-12). A flask was charged
with syn-11 (90 mg, 0.252 mmol) in dry CH2Cl2 (1.5 ml) at ꢀ 808. To the soln. was added DIBAL in
hexane (0.94m, 0.28 ml, 0.265 mmol). After 20 min, the mixture was stirred with aq. Rochelle salt soln.,
then extracted with Et2O. The combined extract was washed with brine, dried (MgSO4), and
concentrated in vacuo to give syn-12 (74 mg, 0.250 mmol, 99%). Colorless oil. [a]2D4 ¼ ꢀ8.0 (c ¼ 1.0,
Et2O). Rf (hexane/AcOEt 6 :1) 0.52. IR (film): 2950m, 2855s, 1725s (C¼O), 1060s. 1H-NMR (300 MHz):
9.69 (d, J ¼ 2.1, HꢀC(1)); 5.87 (s, HꢀC(5)); 5.36 (q, J ¼ 6.9, HꢀC(7)); 4.31 (d, J ¼ 6.6, HꢀC(3)); 2.54
(quint., J ¼ 6.9, HꢀC(2)); 1.72 (s, MeꢀC(4)); 1.72 (s, MeꢀC(6)); 1.68 (d, J ¼ 6.9, Me(8)); 1.05 (d, J ¼
6.9, Meꢀ(2)); 0.94 (t, J ¼ 8.4, (MeCH2)3Si); 0.58 (q, J ¼ 7.5, (MeCH2)3Si). 13C-NMR (150 MHz): 204.7;
.
133.9; 132.7; 130.9; 124.6; 78.1; 51.0; 23.0; 16.5; 14.1; 13.6; 8.96; 6.80; 4.77. EI-MS: 296 (Mþ ), 267 ([M ꢀ
.
Et]þ), 239, 217, 115 ([Et3Si]þ), 87. HR-EI-MS: 296.2178 (Mþ , C17H32O2Siþ; calc. 296.2172).
(4RS,5R,6S,7E,9E)-5,7,9-Trimethyl-6-[(triethylsilyl)oxy]undeca-7,9-dien-4-ol (syn-13). To a soln. of
syn-12 (31 mg, 0.10 mmol) in Et2O (1.0 ml) was added PrLi in Et2O (1.3m, 160 ml, 0.273 mmol) at ꢀ 808
under Ar, and the mixture was stirred for 30 min. The reaction was quenched with sat. aq. NH4Cl soln.,
and the resulting mixture was extracted with Et2O. The combined extract was washed with brine, dried
(MgSO4), and concentrated in vacuo. Purification of the crude product by TLC (hexane/AcOEt 50 :1)
afforded syn-13 (22 mg, 0.065 mmol, 65%). Colorless oil. Rf (hexane/AcOEt 6 :1) 0.54. IR (film): 3450s
(br., OH), 2880s, 1460s, 1000s. 1H-NMR (300 MHz): 5.85 (s, HꢀC(8)); 5.36 (q, J ¼ 6.9, HꢀC(10)); 4.05
(d, J ¼ 6.3, HꢀC(6)); 3.50 – 3.60 (m, HꢀC(4)) 2.13 (d, J ¼ 3.3, OH); 1.73 (s, MeꢀC(7)); 1.69 (d, J ¼ 6.9,
Me(11)); 1.69 (s, MeꢀC(9)); 1.26 – 1.54 (m, CH2(3), CH2(2), HꢀC(5)); 0.95 (t, J ¼ 7.8, (MeCH2)3Si);
0.95 (t, J ¼ 7.8, Me(1)); 0.88 (d, J ¼ 6.9, MeꢀC(5)); 0.62 (q, J ¼ 7.8, (MeCH2)3Si). 13C-NMR (150 MHz):
135.2; 133.0; 130.2; 124.1; 82.4; 73.2; 65.8; 40.7; 37.4; 19.3; 16.6; 15.3; 14.2; 14.1; 13.6; 7.01; 6.87; 4.85. FAB-
MS: 339 ([M ꢀ H]ꢀ), 306, 199, 153, 131. HR-FAB-MS: 339.2719 ([M ꢀ H]ꢀ, C20H39O2Siꢀ; calc.
339.2719).
(4RS,5R,6S,7E,9E)-Isomer (ent-syn-13). In the same manner as described for syn-12 and syn-13, ent-
syn-11 (489 mg, 1.37 mmol) afforded ent-syn-13 (233 mg, 0.685 mmol, 50% in two steps). Colorless oil.
HR-FAB-MS: 363.2697 ([M þ Na]þ, C20H40NaO2Siþ; calc. 363.2695).