1086
M. Campagnole and B. Delmond
After being stirred for 4 h at room temperature, the mixture was diluted with
ether and filtered through an alumina column. The filtrate was washed with
HCl solution, H2O, and saturated NaCl solution; dried; and concentrated to
give keto-acetate 15 as an oil (100 mg; 84% yield).
1H NMR (dH; CDCl3): 1.04 (3H, s), 1.05 (3H, s), 1.15 (3H, d, J ¼ 6.4 Hz),
1.53 (3H, s), 2.02 (3H, s), 3.28 (3H, s), 3.87 (1H, m), 5.12 (1H, t,
J ¼ 4.5 Hz). 13C NMR (dC; CDCl3): 17.0 (CH3-13), 19.0 (CH3-10), 21.1
(CH3C55O), 25.1 (CH2-3), 27.1 (CH3-11 or CH3-12), 28.3 (CH3-11 or
CH3-12), 33.5 (C-1), 34.7 (CH2-2), 52.2 (CH2-8), 56.3 (CH3O), 70.7
(CH-4), 72.1 (CH-9), 126.2 (C-5), 148.3 (C-6), 170.7 (OC55O), 208.0
(C55O). MS (m/z, %): 282 (13), 59 (100). HRMS (C16H26O4): calcd.
282.1831, found 282.1836.
Preparation of 4-Acetoxy-b-damascone 16
Keto-acetate 15 (70 mg, 0.25 mmol) in Et2O solution (20 mL) was stirred for
12 h at room temperature with active neutral alumina (7 g). The mixture was
filtered, and the filtrate was concentrated to give 4-acetoxy-b-damascone 16 as
an oil (48 mg, 78% yield) (bp 96–988/0.01 mm).
1H NMR (dH; CDCl3): 1.01 (3H, s), 1.02 (3H, s), 1.48 (3H, s), 1.92 (3H, dd,
J ¼ 6.8 Hz, J0 ¼ 1.5 Hz), 2.05 (3H, s), 5.19 (1H, t, J ¼ 4.9 Hz), 6.12 (1H, dq,
J ¼ 15.8 Hz, J0 ¼ 1.5 Hz), 6.76 (1H, dq, J ¼ 6.8 Hz, J0 ¼ 15.8 Hz). 13C NMR
(dC; CDCl3): 17.7 (CH3-13), 18.4 (CH3-10), 21.2 CH3C55O), 25.3 (CH2-3),
27.4 (CH3-11 or CH3-12), 28.5 (CH3-11 or CH3-12), 33.7 (C-1), 34.7
(CH2-2), 70.9 (CH-4), 127.5 (C-5), 133.8 (CH-8), 145.7 (C-6), 146.5
(CH-9), 170.8 (OC55O), 200.2 (C55O). MS (m/z, %): 250 (18), 69 (100).
HRMS (C15H22O3): calcd. 250.1569, found 250.1570.
Preparation of b-Damascenone 1 from 16
4-Acetoxy-b-damascone 16 (170 mg, 0.68 mmol) in benzene solution
(10 mL) was stirred at 508C with p-toluene sulfonic acid (24 mg,
0.13 mmol) for 12 h. The mixture was taken up in ether and successively
washed with sodium bicarbonate solution, H2O, and aqueous saturated NaCl
solution. The drying and the removal of solvents under reduced pressure
left crude b-damascenone (90 mg, 70% yield), which was purified by
column chromatography. Elution with petroleum ether/ether (98:2) give a
very pure sample (ꢀ100% purity) of b-damascenone 1; spectroscopic data
were identical with those reported.[9]
1H NMR (dH; CDCl3): 1.01 (6H, s), 1.61 (3H, s), 1.91 (3H, dd, J ¼ 6.8 Hz,
J0 ¼ 1.5 Hz), 5.79 (2H, m), 6.16 (1H, dq, J ¼ 15.8 Hz, J0 ¼ 1.5 Hz), 6.81
(1H, dq, J ¼ 6.8 Hz, J0 ¼ 15.8 Hz). 13C NMR (dC; CDCl3): 18.3 (CH3-10),
19.4 (CH3-13), 26.2 (CH3-11 and CH3-12), 33.8 (C-1), 39.4 (CH2-2), 127.3