995
Spectral Assignments and Reference Data
enhancement when the signal at υH 1.15 (s), assigned to H-15, was
irradiated.
For compound 17, there was a previous incomplete report in
(4aR,8aS)-3,4a,8,8-tetramethyl-4a,5,6,7,8,8a-
hexahydronaphthalen-2(1H)-one 3
Acetate 2 (1.5 g, 6.0 mmol) was dissolved in a 2 N KOH solution in
methanol (130 ml, 260 mmol). The resulting colorless solution was
magnetically stirred at room temperature. After 24 h, saponification
was complete, and the solvent was evaporated at reduced pressure.
The oily residue was suspended in water (500 ml), extracted with
ethyl acetate (AcOEt) (3 ð 100 ml), and the aqueous phase, discarded.
The organic phase was washed with water (2 ð 50 ml) and then
with saturated sodium chloride (2 ð 50 ml), dried over anhydrous
Na2SO4, filtered and evaporated at reduced pressure to obtain crude
alcohol 11 that was used in the next step without purification. To a
magnetically stirred solution of crude alcohol 11 in dichloromethane
(150 ml), PCC (1.08 g, 5 mmol) was added at once. The brown
suspension was stirred overnight, until thin-layer chromatography
analysis revealed the disappearance of the starting material. Celite
(500 mg) andethyl acetate (50 ml) were addedto the reactionmixture,
and the slurry was filtered through a short pad of silica gel, and
washed copiously with ethyl acetate. The filtrate was evaporated,
and the residue chromatographed to afford isonordrimenone 3, as
a colorless oil (870 mg, 81% yield from compound 2). [˛]2D0 D C2.47
(c D 20.2, CHCl3) FTIR (liquid film, ꢂ) 2956, 2926, 1673, 1462
and 1450 cmꢀ1, HRMS m/z MC 206.16749 (calculated for C14H22O,
206.16706, error: 2.1 ppm).
good agreement with our present data,12 except for a small constant
shifting in the 1H as well as 13C NMR data. The full assignments for
that compound, including all coupling constants and multiplicities,
are summarized in Table 1 for 1H and Table 2 for 13C NMR data.
In the case of compound 13, there was no previous report on the
full NMR spectra. However, similar compounds, epimeric at C-9,
were partially described.12,18 The complete assignments of the 1H
and 13C NMR spectra, are reported in Tables 1 and 2, respectively.
EXPERIMENTAL
All reactions were routinely performed under a dry nitrogen
atmosphere, with magnetic stirring. All chemicals were used as
purchased.
Melting points were determined in a Stuart Scientific Apparatus
SMP3, and are uncorrected. Optical rotations were measured in
CHCl3 solutions, in a- 0.1 dm cell, in an Optical Activity, Ltd,
instrument, and concentrations were expressed in g/100 ml. Infrared
spectra were recorded in a Bruker Vector–22 FTIR spectrometer.
NMR spectra were obtained on a Bruker Avance 400 digital
NMR spectrometer, at 400.13 MHz for 1H and 100.13 MHz for 13C,
in CDCl3 solutions with TMS as internal standard. The digital
resolution for standard experiments were 0.12 Hz/point for 1H, and
0.41 for 13C. For 2D, COSY, NOE, HSQC and HMBC experiments,
Bruker standard software was used. Assignments were done by
a combination of 1D and 2D NMR techniques, in each case, as
needed. All 1H NMR data are summarized in Table 1, and 13C
NMR data, in Table 2. High-resolution mass spectra (HRMS) were
obtained in a Thermo Finnigan spectrometer attached to a double-
focusing analyzer with a magnetic and an electric sector, and spectra
were obtained by electron impact (EI), by peak-matching, using
perfluoro-tert-butylamine (FC43), as reference.
((1R,4aS,8aS)-2-((tert-butyldiphenylsilyloxy) methyl)-5,5,8a-
trimethyl-1,4,4a,5,6,7,8,8a-octahydronaphthalen-1-yl)
methanol 13
A magnetically stirred solution of diol 12 (1.00 g, 4.19 mmol) in
°
DMF (30 ml) was cooled at 0 C in an icewater bath, TBDPS-Cl
(1.15 g, 4.20 mmol), and imidazole (0.57 g, 8.33 mmol) were added
slowly with a syringe and under a nitrogen atmosphere. The
reaction mixture was kept at room temperature with magnetic
stirring for 24 h, then diluted with water (150 ml) and extracted
with ethyl acetate (3 ð 50 ml). The combined organic extracts were
dried (Na2SO4), and concentrated. Chromatographic purification of
the resulting crude residue gave monosilyl-ether 13 (1.94 g, 97%), as
a yellowish oil: [˛]1D8 D ꢀ45.0 (c D 4.0, CHCl3). FTIR (KBr, ꢂ) : 3425,
Table 2. 13C NMR chemical shifts, υ (ppm), for 3, 13, 17 and 6a
3071, 2858, 1589 and 1472 cmꢀ1
.
Carbon
3
13
17
6
(2R,4aR,8aS)-3-((tert-butyldiphenylsilyloxy)methyl)-4a,8,8-
trimethyl-1,2,4a,5,6,7,8,8a-octahydronaphthalen-2-yl
ethanoate 14
1
38.4
18.6
36.6
18.9
38.1
18.5
37.3
18.3
2
To a solution of homoallyl alcohol 13 (1.74 g, 3.65 mmol) in benzene
(300 ml), LTA (2.23 g, 5.03 mmol) was added, and the resulting pale
yellow solution was refluxed for 4 h. The whitish suspension was
copiously washed with water (6 ð 150 ml), dried with anhydrous
MgSO4, and evaporated in vacuo. Acetate 14 was obtained as a
colorless oil (1.49 g, 81% yield),1 that was used in the next step
without further purification.
3
41.2
42.7
41.2
40.9
4
32.7
33.2
32.9
33.1
5
50.6
43.6
50.3
49.5
6
35.3
26.6
35.6
35.7
7
200.8
131.1
157.8
37.8
126.8
135.5
54.0
202.4
133.9
159.1
36.8
199.2
130.9
167.8
37.6
8
9
(4aR,8aS)-3-(hydroxymethyl)-4a,8,8-trimethyl-4a,5,6,7,8,8a-
hexahydronaphthalen-2(1H)-one 17
10
36.1
Ester 14 (1.2 g, 2.38 mmol) was treated exactly as described for the
preparation of compound 3 above; the saponification step was done
with 2 N KOH in methanol (100 ml, 0.2 mol). After the standard
treatment described earlier, crude alcohol 15 (1.01 g, 92%) was
obtained as a colorless oil, which was used in the next step without
any further purification.
When crude alcohol 15 (0.9 g, 1.94 mmol) was oxidized with
PDC (0.7 g, 1.9 mmol), as described above for compound 3, crude
ketone 16 (771 mg, 86% yield) was obtained as a colorless oil, which
was used in the next step without purification.12
11
62.5
12
15.4
32.2
20.8
18.4
68.2
61.4
32.2
20.9
18.3
190.0
32.2
20.9
17.7
13
33.1
14
22.1
15
21.7
Si–CꢀCH3ꢁ3
Si–CꢀCH3ꢁ3
Si–CAr
26.9
19.3
133.4
133.5
135.7
127.7
129.8
To a magnetically stirred solution of the silyl ether 16 (461 mg,
1 mmol) in dry tetrahydrofuran (20 ml), and under nitrogen, a 1-M
tetrahydrofuran-solution of tetrabutylammonium fluoride (2.3 ml,
0.23 mmol), was added dropwise. The reaction mixture was stirred
for 2 h at room temperature, diluted with ethyl acetate (50 ml),
washed with 5% HCl (20 ml), saturated NaHCO3 (50 ml), dried
(MgSO4), and finally evaporated. The residue was chromatographed,
to give a pale yellow oil (102 mg, 100%), [˛]1D8 D C2.56 (c D 11.7,
o-Ph
m-Ph
p-Ph
a In CDCl3 solution. All these assignments were in agreement with
HSQC and HMBC spectra.
CHCl3). FTIR (liquid film, ꢂ) 3447, 2927, 1710, 1668 and 1460 cmꢀ1
.
Copyright 2007 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2007; 45: 993–996
DOI: 10.1002/mrc