o
8
-Acetoxy-6-methyloctan-2-one (4). A stirred solution (Ar, 20 C) of 3 (10.00 g, 36.8 mmole) in absolute DMF
(
104 mL) was treated at once with LiI (12.87 g, 95.5 mmole), boiled until CO evolution ceased (~12 h), cooled, and extracted
2
with Et O (4×50 mL). The combined extracts were washed successively with saturated Na S O and NaCl solutions, dried over
2
2 2 3
Na SO , and filtered. The solvent was evaporated to give 4, 5.96 g (81%).
2
4
-1
IR spectrum (KBr, ν, cm ): 1740 (ester C O), 1720 (ketone C O), 1250, 1055 (C–O–C).
PMR spectrum (CDCl , δ, ppm, J/Hz): 0.88 (3H, d, J = 6.5, CH -6), 1.06 (7H, m, H-4-H-7), 2.01 (3H, s, CH CO), 2.13
3
3
3
(
3H, s, CH CO ), 2.44 (2H, t, J = 7, H-3), 4.05 (2H, m, H-8).
3 2
13
C NMR spectrum (CDCl ): 18.93 (q, CH -6), 20.55 (q, CH CO ), 20.67, 34.93, 35.85 (all t, C-4, C-5, C-7), 29.30
3
3
3
2
(
q, C-1), 29.44 (d, C-6), 43.33 (t, C-3), 62.34 (t, C-8), 170.58 (s, CH CO ), 208.32 (s, C-2).
3
2
3
,7-Dimethyloct-7-en-1-ylacetate (5). A suspension of methyltriphenylphosphonium iodide (19.65 g, 49.0 mmole)
o
in absolute THF (148 mL, Ar, 0 C) was treated dropwise with n-butyllithium (1 N, 49 mL, 49 mmole) in hexane. The mixture
was stirred at room temperature for 1 h, cooled to 0 C, and treated dropwise with 4 (5.90 g, 29.5 mmole) in absolute THF
21 mL). The reaction mixture was stirred at 0 C for 15 min, left overnight at room temperature, diluted with petroleum ether
o
o
(
(
200 mL), and filtered through a layer of SiO . The solvent was removed. The solid was chromatographed over a silica-gel
2
-1
column (petroleum ether—diethylether, 10:1) to give 5, 4.95 g (85%). IR spectrum (KBr, , cm ): 3090, 980, 900 (CH C),
2
1
1
750 (C C), 1660 (C C), 1240, 1050 (C–O–C).
PMR spectrum (CDCl , δ, ppm, J/Hz): 0.90 (3H, d, J = 6.5, CH -3), 1.38 (7H, m, H-2-H-5), 1.69 (3H, s, CH C C),
3
3
3
.98 (2H, m, H-6), 2.02 (3H, s, CH CO ), 4.04 (2H, m, H-1), 4.66 (2H, d, J = 4.3, CH C).
3
2
2
13
C NMR spectrum (CDCl ): 19.38 (q, CH -3), 19.42 (q, CH -7), 20.97 (q, CH COO), 24.76, 35.42, 36.39, 37.90 (all
3
3
3
3
t, C-2, C-4-C-6), 29.68 (d, C-3), 62.97 (t, C-1), 109.72 (t, C-8), 145.93 (C-7), 171.18 (s, CH COO).
3
7
-Methoxy-3,7-dimethyloctan-1-ol (7). A stirred solution of 5 (1.42 g, 7.0 mmole) in absolute CH OH (25 mL, Ar,
3
o
o
o
5
C) was treated with Hg(OAc) (2.09 g, 6.55 mmole), stirred for 1 h at 5 C and 24 h at room temperature, cooled to 0 C, treated
2
dropwise with NaBH (0.49 g, 12.7 mmole) and NaOH (1.52 g, 37.8 mmole) in water (1.8 mL), left to stand (0 C, 1 h; 20 C,
o
o
4
2
h), diluted with Et O (100 mL), and filtered through a layer of Al O on a Schott filter to remove mercury. The filtrate was
2 2 3
washed with saturated NaCl solution, dried over MgSO , filtered, and evaporated. The solid was chromatographed over a silica-
4
gel column (petroleum ether—diethylether, 5:1) to give 6, 0.64 g (97%).
-1
IR spectrum (KBr, ν, cm ): 3600-3300 (OH), 1250, 1055 (C–O–C).
PMR spectrum (CDCl , δ, ppm): 0.89 (3H, d, CH -3), 1.11 (6H, s, CH -7, H-8), 1.28 (7H, m, H-2-H-5), 1.58 (2H, m,
3
3
3
H-6), 2.21 (1H, br.s, OH), 3.14 (3H, s, CH O), 3.65 (2H, t, H-1).
3
13
C NMR spectrum (CDCl ): 19.58 (q, CH -3), 24.83, 24.91 (both q, CH -7, C-8), 21.10, 37.58, 39.85, 39.98 (all t,
3
3
3
C-2, C-4-C-6), 29.41 (d, C-3), 48.98 (q, CH O), 60.96 (t, C-1), 74.64 (s, C-7).
3
7
-Methoxy-3,7-dimethyloctanal (8). A suspension of pyridinium chlorochromate (0.60 g, 2.8 mmole) in dry CH Cl
2 2
o
(
3 mL) was stirred (Ar, 20 C), treated with 6 (0.70 g, 3.7 mmole) in dry CH Cl (1.5 mL), stirred for 2 h, diluted with Et O
2 2 2
(
20 mL), and filtered through a layer of silica gel. The solid was washed with Et O (50 mL). The filtrate was evaporated to
2
give 8, 0.63 g (90%). The IR and PMR spectra were identical to those in the literature [9].
Isopropyl 11-methoxy-3,7,11-trimethyldodeca-2E,4E-dienoate (10) was prepared from 8 in 82% yield according
to the literature method [9]. The IR and PMR spectra were identical to those of the authentic compound.
3
,7-Dimethyloct-7-en-1-ol (6). Unsaturated acetate (5, 3.50 g, 17.7 mmole) was dissolved in CH OH (18 mL), treated
3
with KOH (1.04 g, 18.4 mmole), and boiled for 4 h. The CH OH was removed. The solid was extracted with Et O (3×30 mL).
3
2
The combined extracts were washed with saturated NaCl solution, dried over Na SO , filtered, and evaporated to give 7,
2
4
2
.49 g (90%).
-1
IR spectrum (KBr, ν, cm ): 3600-3300 (OH), 3090, 980, 900 (CH C), 1660 (C C).
2
PMR spectrum (CDCl , δ, ppm, J/Hz): 0.90 (3H, d, J = 6.5, CH -3), 1.40 (7H, m, H-2-H-5), 1.70 (3H, s, CH C C),
3
3
3
2
2
.01 (2H, m, H-6), 3.65 (2H, m, H-1), 4.60 (2H, d, J = 4.3, CH C).
2
1
3
C NMR spectrum (CDCl ): 19.39 (q, CH -3), 19.42 (q, CH -7), 24.78, 35.44, 36.41, 37.92 (all t, C-2, C-4-C-6),
3
3
3
9.69 (d, C-3), 60.96 (t, C-1), 109.74 (t, C-8), 146.01 (C-7).
,7-Dimethyloctanal (9). A solution of 7 (2.00 g, 12.7 mmole) in absolute CH OH (20 mL) was treated with Pd/C
3
3
(
0.20 g, 5%) with vigorous stirring on a magnetic stirrer and hydrogenated with H (0.28 L, ~5 h). The catalyst was filtered
2
off. The filtrate was evaporated. The solid (1.88 g) was dissolved in dry CH Cl (9 mL), stirred, treated with a suspension of
2
2
pyridinium chlorochromate (3.84 g, 17.8 mmole) in dry CH Cl (37 mL, Ar, 20 C), stirred for 2 h, diluted with Et O (200 mL),
2
2
2
4
88