2596
26
A. Srikrishna, B. Beeraiah / Tetrahedron: Asymmetry 18 (2007) 2587–2597
½aꢁD ¼ þ13:0 (c 1.0, CHCl3); IR (neat): mmax/cmꢀ1 1740,
889; 1H NMR (300 MHz, CDCl3): d 4.74 (1H, s), 4.70
(1H, s), 3.64 (3H, s), 3.33 (3H, s), 2.67 (1H, dd, J 11.7
and 4.5 Hz), 2.09 (2H, t, J 8.7 Hz), 1.95–1.75 (4H, m),
1.70 (3H, s), 1.68–1.53 (3H, m), 1.33–0.80 (5H, m), 0.88
(3H, s), 0.71 (3H, s); 13C NMR (75 MHz, CDCl3): d
173.9 (C), 150.1 (C), 109.6 (CH2), 88.4 (CH), 57.8 (CH3),
54.1 (CH3), 51.3 (CH), 49.5 (C), 43.6 (CH2), 38.2 (CH),
37.9 (C), 35.8 (CH2), 35.5 (CH2), 30.3 (CH2), 29.7 (CH2),
26.7 (CH3), 26.1 (CH2), 20.2 (CH3), 13.6 (CH3); HRMS
m/z: (M+Na) calcd for C19H32O3Na, 331.2249; found,
331.2248.
4.20. 1-[(1R,3S,6R,8S)-3-Methoxy-2,2-dimethyl-8-(1-meth-
ylethenyl)bicyclo[4.3.0]non-8-yl]-4-methylpentan-3-ol 30
To an ice cold solution of aldehyde 27b (42 mg, 0.16 mmol)
in anhydrous THF (1 mL) was added a solution of isopro-
pylmagnesium bromide [freshly prepared from magnesium
(62 mg, 2.36 mmol) and isopropyl bromide (0.24 mL,
2.36 mmol) in anhydrous THF (5 mL)] and stirred for
45 min at rt. The reaction mixture was then quenched with
saturated aqueous NH4Cl and extracted with ether
(3 · 5 mL). The combined organic layer was washed with
brine and dried (Na2SO4). Evaporation of the solvent
and purification of the residue over a silica gel column
using ethyl acetate–hexane (1:9) as eluent furnished a 1:1
4.18. 3-[(1R,3S,6R,8S)-3-Methoxy-2,2-dimethyl-8-(1-meth-
ylethenyl)bicyclo[4.3.0]non-8-yl]propan-1-ol 26b
epimeric mixture of alcohol 30 (46 mg, 94%) as an oil.
26
½aꢁD ¼ þ8:6 (c 1.4, CHCl3); IR (neat): mmax/cmꢀ1 3444,
1
885; H NMR (300 MHz, CDCl3): (mixture of two iso-
To a cold (0 ꢁC), magnetically stirred solution of ester 25b
(76 mg, 0.25 mmol) in dry ether (3 mL) was added LAH
(19 mg, 0.5 mmol) and the reaction mixture was stirred at
the same temperature for 1.5 h. Ethyl acetate (0.5 mL)
was carefully introduced to consume the excess reagent
and the reaction was quenched with ice cold water
(0.2 mL). The suspension was filtered through a sintered
funnel and the residue was thoroughly washed with ether
(3 · 5 mL). The ether layer was washed with brine and
dried (Na2SO4). Evaporation of the solvent and purifica-
tion of the residue over a silica gel column using ethyl ace-
mers) d 4.70 (1H, s), 4.68 (1H, s), 3.33 (3H, s), 3.30–3.20
(1H, m), 2.67 (1H, dd, J 11.4 and 4.2 Hz), 1.95–1.80 (3H,
m), 1.69 (3H, s), 1.70–1.00 (13H, m), 0.96 (3H, s), 0.78
(3H, s), 0.92–0.88 (6H, m); 13C NMR (75 MHz, CDCl3):
(mixture of two isomers) d 151.2 (C), 108.9 (CH2), 88.6
(CH), 77.3 and 77.2 (CH), 57.9 (CH3), 54.1 (CH), 49.7
(C), 44.0 and 43.9 (CH2), 38.3 (CH), 37.9 (C), 37.7 and
37.6 (CH2), 35.9 and 35.8 (CH2), 33.5 (CH), 29.9 (CH2),
29.8 (CH2), 26.7 (CH3), 26.2 (CH2), 20.4 (CH3), 19.2
(CH3), 17.3 and 17.1 (CH3), 13.6 (CH3). HRMS m/z:
(M+H) calcd for C21H39O2, 323.2973. Found: 323.2973.
tate–hexane (1:6) as eluent furnished alcohol 26b (68 mg,
26
99%) as an oil. ½aꢁD ¼ þ8:3 (c 1.2, CHCl3); IR (neat):
4.21. 1-[(1R,3S,6R,8S)-3-Methoxy-2,2-dimethyl-8-(1-meth-
ylethenyl)bicyclo[4.3.0]non-8-yl]-4-methylpentan-3-one 31
m
max/cmꢀ1 3374, 885; 1H NMR (300 MHz, CDCl3): d
4.71 (1H, s), 4.69 (1H, s), 3.56 (2H, t, J 6.6 Hz), 3.33
(3H, s), 2.68 (1H, dd, J 11.4 and 3.9 Hz), 1.95–0.80 (15H,
m), 1.62 (3H, s), 0.88 (3H, s), 0.70 (3H, s); 13C NMR
(75 MHz, CDCl3): d 151.0 (C), 109.0 (CH2), 88.6 (CH),
63.2 (CH2), 57.8 (CH3), 54.1 (CH), 49.6 (C), 43.8 (CH2),
38.3 (CH), 38.0 (C), 37.5 (CH2), 35.8 (CH2), 29.8 (CH2),
28.6 (CH2), 26.8 (CH3), 26.2 (CH2), 20.4 (CH3), 13.6
(CH3); HRMS m/z: (M+Na) calcd for C18H32O2Na,
303.2300; found, 303.2299.
To a magnetically stirred suspension of PCC (84 mg,
0.39 mmol) and NaOAc (32 mg, 0.39 mmol) in anhydrous
CH2Cl2 (1 mL) was added a solution of an epimeric mix-
ture of alcohol 30 (40 mg, 0.13 mmol) in anhydrous
CH2Cl2 (2 mL) and stirred vigorously for 6 h at rt. The
reaction mixture was then filtered through a small silica
gel column and the column was eluted with more CH2Cl2.
Evaporation of the solvent and purification of the residue
over a silica gel column using CH2Cl2–hexane (1:3) as elu-
24
4.19. 3-[(1R,3S,6R,8S)-3-Methoxy-2,2-dimethyl-8-(1-meth-
ylethenyl)bicyclo[4.3.0]non-8-yl]propanal 27b
ent furnished ketone 31 (38 mg, 96%) as an oil. ½aꢁD ¼ þ5:0
(c 1.4, CHCl3); IR (neat): mmax/cmꢀ1 1714, 1635, 887; H
1
NMR (300 MHz, CDCl3): d 4.72 (1H, s), 4.68 (1H, s),
3.32 (3H, s), 2.66 (1H, dd, J 11.7 and 4.2 Hz), 2.54 (1H,
septet, J 7.2 Hz), 2.20 (2H, t, J 7.8 Hz), 1.90–1.50 (6H,
m), 1.67 (3H, s), 1.40–0.80 (6H, m), 1.06 (6H, d, J
6.9 Hz), 0.95 (3H, s), 0.77 (3H, s); 13C NMR (75 MHz,
CDCl3): d 214.1 (C), 150.7 (C), 109.3 (CH2), 88.5 (CH),
57.8 (CH3), 54.2 (CH), 49.5 (C), 43.7 (CH2), 41.0 (CH),
38.2 (CH), 37.9 (C), 36.5 (CH2), 35.6 (CH2), 34.5 (CH2),
29.7 (CH2), 26.7 (CH3), 26.2 (CH2), 20.3 (CH3), 18.5 (2C,
CH3), 13.6 (CH3); HRMS m/z: (M+H) calcd for
C21H37O2, 321.2793; found, 323.2791.
To a magnetically stirred solution of alcohol 26b (60 mg,
0.214 mmol) in anhydrous CH2Cl2 (3 mL) was added
PDC (194 mg, 1.1 mmol) and stirred for 8 h at rt. The reac-
tion mixture was then filtered through a small silica gel col-
umn and the column was eluted with more CH2Cl2.
Evaporation of the solvent and purification of the residue
over a silica gel column using ethyl acetate–hexane (1:19)
as eluent furnished aldehyde 27b (57 mg, 96%) as an oil.
26
½aꢁD ¼ þ8:7 (c 1.5, CHCl3); IR (neat): mmax/cmꢀ1 2713,
1726, 1635, 889; 1H NMR (300 MHz, CDCl3): d 9.73
(1H, s), 4.75 (1H, s), 4.71 (1H, s), 3.32 (3H, s), 2.66 (1H,
dd, J 11.4 and 3.9 Hz), 2.24 (2H, t, J 7.5 Hz), 2.00–1.50
(7H, m), 1.68 (3H, s), 1.40–1.00 (5H, m), 0.95 (3H, s),
0.77 (3H, s); 13C NMR (75 MHz, CDCl3): d 201.3 (CH),
150.2 (C), 109.8 (CH2), 88.4 (CH), 57.8 (CH3), 54.1
(CH), 49.4 (C), 43.6 (CH2), 40.5 (CH2), 38.2 (CH), 37.9
(C), 35.6 (CH2), 32.7 (CH2), 29.7 (CH2), 26.7 (CH3), 26.1
(CH2), 20.2 (CH3), 13.6 (CH3).
4.22. 5-[(1R,3S,6R,8S)-3-Methoxy-2,2-dimethyl-8-(1-methyl-
ethenyl)bicyclo[4.3.0]non-8-yl]-3-(1-methylethyl)pent-1-en-
3-ol 32
To an ice cold solution of ketone 31 (30 mg, 0.08 mmol) in
anhydrous THF (1 mL) was added a solution of vinylmag-
nesium bromide [freshly prepared from magnesium (30 mg,