G. Mehta et al. / Tetrahedron 60 (2004) 5013–5017
5015
dilute solutions in spectroscopic grade dichloromethane.
Proton NMR spectra were recorded on a Bruker DRX-300
spectrometer as dilute solutions in deuterochloroform. The
chemical shifts are quoted in parts per million (ppm) relative
to tetramethylsilane as the internal standard and the
multiplicity of each signal is designated by the following
abbreviations: s, singlet; d, doublet; t, triplet; q, quartet; m,
multiplet. All coupling constants are quoted in Hertz.
Carbon-13 NMR spectra were recorded on Bruker DPX-300
spectrometer as dilute solutions in deuterochloroform.
Chemical shifts are recorded relative to internal chloroform
(d 77.2) or TMS as standard on a broad band decoupled
mode, and the multiplicities determined using a DEPT
sequence. Mass spectra were recorded on a JEOL-JMS 600
instrument and elemental analyses were obtained on a
Perkin–Elmer 204b elemental analyzer.
(q), 32.2 (t), 24.7 (q), 24.3 (q), 21.0 (q), 20.5 (q). Elemental
analyses: C, 56.27%; H, 8.44%; S, 11.31%; C13H24SO4
requires C, 56.49%; H, 8.75%; S, 11.60%.
4.1.3. (4R)-4-isopropenyl-7-methyl-6-octen-2-one (6).
Sodium hydride (130 mg, excess) was added in one portion
to a solution of the hydroxymesylate 5 (114 mg, 0.41 mmol)
in dry tetrahydrofuran (8 ml) under nitrogen atmosphere and
the resulting mixture was heated to reflux for 8 h. It was then
cooled in an ice-bath and quenched by slow addition of
methanol (1 ml) followed by saturated aqueous ammonium
chloride (5 ml). It was then extracted with ether (2£25 ml)
and the combined ether extract was washed with water
(2£20 ml), brine (1£10 ml) and then dried (Na2SO4). It was
then filtered and the filtrate was concentrated to leave the
crude product as a pale yellow oil which on chromatography
(SiO2) (petroleum ether/ethyl acetate, 20:1) afforded the
product as a colourless oil (58 mg, 79%). [a]D þ12.1 (c, 2.1
in CHCl3). nmax (neat) 2920, 1720, 1665 and 1645 cm21. 1H
NMR (300 MHz, CDCl3): d 5.01 (1H, t, J¼7.2 Hz), 4.73
(1H, s), 4.67 (1H, s), 2.60 (1H, quin., J¼6.9 Hz), 2.46–2.44
(2H, m), 2.08 (3H, s), 2.03 (2H, t, J¼7.2 Hz), 1.66 (6H, s),
1.54 (3H, s). 13C NMR (75 MHz, CDCl3): d 208.4 (s), 147.1
(s), 133.0 (s), 122.0 (d), 111.0 (t), 47.5 (t), 42.8 (d), 30.1 (q),
32.0 (t), 25.8 (q), 19.8 (q), 17.8 (q). Elemental analyses: C,
79.69%; H, 10.98%; C12H20O requires C, 79.95%; H,
11.18%. m/z (EI, 70 eV) 180 (Mþ), 165, 137 (100%).
4.1.1. (1R,3R,5R)-5-isopropenyl-1, 2, 2-trimethylcyclo-
hexane-1,3-diol (4). A solution of methylmagnesium iodide
(2 M in THF, 10 ml, 20 mmol) was added dropwise over
20 min to a stirred solution of the hydroxyketone 33 (1.64 g,
9.11 mmol) in dry THF under nitrogen at 0 8C and the
resulting yellowish solution was allowed to come to room
temperature over 20 h. It was quenched with saturated
aqueous NH4Cl solution (10 ml) and then extracted with
ether (2£50 ml). The combined organic extract was washed
successively with water (2£50 ml), brine (20 ml) and then
dried (Na2SO4). It was filtered and the filtrate was
concentrated to leave the crude product as a pale yellow
oil which on chromatography (SiO2) (petroleum ether/ethyl
acetate, 7:1) afforded the product as a colourless oil (1.17 g,
65%). [a]D þ8.54 (c, 0.82 in CHCl3). nmax (neat) 3340,
2920, 1665, 1080 and 885 cm21.1H NMR (300 MHz,
CDCl3): d 4.77 (1H, s), 4.70 (1H, s), 3.62 (1H, t,
J¼9.1 Hz), 3.12 (1H, bs), 2.98–2.64 (1H, m), 1.72 (3H,
s), 1.69–1.57 (4H, m), 1.13 (3H, s), 1.10 (3H, s), 0.88 (3H,
s). 13C NMR (75 MHz, CDCl3): d 149.3 (s), 108.8 (t), 78.6
(d), 76.0 (s), 40.7 (t), 39.4 (s), 33.9 (t), 33.8 (d), 25.3 (q),
24.0 (q), 21.0 (q), 20.6 (q). Elemental analyses: C, 72.49%;
H, 11.04%; C12H22O2 requires C, 72.68%; H, 11.18%. m/z
(EI, 70 eV) 180 (Mþ2H2O), 145.
4.1.4. (2S)-2-isopropenyl-5-methyl-4-hexenyl acetate (7).
Stannic chloride (130 mg, 0.5 mmol) was added dropwise to
a stirred solution of the ketone (90 mg, 0.5 mmol) and
bis(trimethylsilyl)peroxide15 (90 mg, 0.5 mmol) in
dichloromethane (5 ml) at 0 8C under nitrogen atmosphere.
After stirring for 1 h at that temperature it was allowed to
come to room temperature and stirring continued for 24 h. It
was then diluted with dichloromethane (25 ml) and then
poured into an aqueous solution of sodium thiosulfate
(10 ml). The organic layer was separated and washed
successively with water (2£10 ml), saturated sodium
bicarbonate solution (1£10 ml), water (1£10 ml) and brine
(1£10 ml). It was then dried (Na2SO4), filtered and the
filtrate was concentrated to leave the crude product as a
brownish oil which on chromatography (SiO2) (petroleum
ether/ethyl acetate, 12:1) afforded lavandulol acetate as a
colourless oil (11 mg, 12%). [a]D 6.3 (c, 1.5 in CHCl3). nmax
4.1.2. (1R,3R,5R)-3-hydroxy-5-isopropenyl-2,2,3-tri-
methylcyclohexyl methanesulfonate (5). Methanesulfonyl
chloride (0.85 ml, 11 mmol) was added in one portion to a
stirred solution of the diol 4 (375 mg, 1.89 mmol) in dry
pyridine (10 ml) at 0 8C under nitrogen. It was allowed to
come to room temperature and stirring continued for 14 h.
The brownish mixture was diluted with water (50 ml) and
then extracted with ether (3£50 ml). The combined ether
extract was washed successively with water (3£25 ml) and
saturated aqueous copper sulfate solution (2£25 ml). It was
then dried (Na2SO4), filtered and the filtrate was concen-
trated to leave the crude product as a brownish oil which on
chromatography (SiO2) (petroleum ether/ethyl acetate, 6:1)
afforded the product as a colourless oil (343 mg, 66%). [a]D
219.58 (c, 2.72 in CHCl3). nmax (neat) 3560, 1660, 1330,
(neat) 2910, 1708, 1670 and 1645 cm21
.
1H NMR
(300 MHz, CDCl3): d 5.05 (1H, t, J¼7.5 Hz), 4.82 (1H, d,
J¼1.5 Hz), 4.73 (1H, bs), 4.03 (2H, d, J¼6.9 Hz) 2.39 (1H,
quin., J¼6.9 Hz), 2.17–2.05 (2H, m), 2.02 (3H, s), 1.69–
1.64 (6H, overlapping singlets), 1.59 (3H, s).13C NMR
(75 MHz, CDCl3): d 171.1 (s), 144.9 (s), 132.9 (s), 121.6
(d), 112.4 (t), 65.8 (t), 46.0 (d), 28.5 (t), 25.7 (q), 20.9 (q),
19.9 (q), 17.8 (q). Elemental analyses: C, 73.66%; H,
10.49%; C12H20O2 requires C, 73.43%; H, 10.27%. m/z (EI,
70 eV) 196 (Mþ), 153, 59 (100%).
4.1.5. (4R)-4-isopropyl-7-methyloctan-2-one (8). A sol-
ution of the ketone 6 (72 mg, 0.4 mmol) in methanol (5 ml)
was vigorously stirred under hydrogen atmosphere in the
presence of Pd–C (10%, 5 mg) for 3 h at room temperature.
The heterogeneous mixture was then filtered through celite
and the filter cake was washed with ether. The combined
organic solution was then concentrated to leave the crude
1
1165 and 880 cm21. H NMR (300 MHz, CDCl3): d 4.89
(1H, s), 4.64 (1H, s), 3.26–3.06 (1H, m), 3.03 (3H, s), 2.54
(1H, tt, J¼8.7, 4.2 Hz), 2.11–2.02 (1H, m), 1.82–1.77 (2H,
m), 1.73 (3H, s), 1.63–1.48 (1H, m), 1.15 (3H, s), 1.12 (3H,
s), 0.99 (3H, s). 13C NMR (75 MHz, CDCl3): d 147.8 (s),
109.6 (t), 90.3 (d), 74.4 (s), 40.5 (t), 40.4 (s), 38.9 (d), 33.7