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General Procedure:
All reactions were carried out in an argon atmosphere. Anhydrous
solvents were purchased from the Kanto Chemical Co., Inc. Reagents
were purchased at the highest commercial quality and were used without further
purification. The IR spectra were measured on a JASCO FT/IR
500 spectrophotometer. Mass spectra, including high-resolution spectra,
were recorded on a JEOL JMS-700 MStation instrument. ¹H
NMR and ¹³C NMR spectra were measured
on Varian Unity 600 (600 MHz and 150 MHz, respectively) and Varian
Unity 200 (200 MHz and 50 MHz, respectively) spectrometers. Chemcopak
Nucleosil 50-5 (4.6 × 250 mm) with a solvent system of
hexane-EtOAc was used for HPLC (a JASCO pump system). Silica gel
60 (70-230 mesh, Fuji Sylisia) was used for column chromatography.
Silica gel BW-300 (200-400 mesh, Fuji Sylisia) was used
for column chromatography and silica gel 60F254 plate
(0.25 mm, Merck) was used for TLC.
Reaction
of Denudatenone A with SmI
2
:
To a stirred solution of SmI2 (0.1 M in THF, 15.2 mL,
1.5 mmol) and H2O (135 mg, 7.5 mmol) was added a solution
of denudatenone A (1; 75.3 mg, 0.25 mmol)
in THF (5 mL) at r.t. and the mixture was stirred for 4.5 h. The
reaction was quenched with a sat. aq solution of Rochelle’s
salt. Organic materials were extracted with Et2O, washed
with brine, and dried (MgSO4). The products were purified
by silica gel flash chromatography (hexane-EtOAc, in a
gradient) to afford 2 (25.7 mg, 34%), 3 (2.5 mg, 3.2%), and 4 (3.6 mg, 5%) as well as 1 (18.8 mg, 25%).
Compound 2: [α]D +72.0
(c = 1.0, CHCl3). ¹H
NMR (600 MHz, CDCl3): δ = 0.92 (d,
3 H, J = 6.9 Hz, H-19), 0.99
(d,
3 H, J = 6.9 Hz,
H-20), 1.06 (s, 3 H, H-15), 1.42 (m, 1 H,
H-13), 1.39
(m, 1 H, H-14), 1.51 (dd, 1 H, J = 8.8,
3.3 Hz, H-11), 1.55 (t, 3 H, J = 1.4
Hz, H-16), 1.59 (m, 1 H, H-10), 1.65 (m, 1 H, H-13), 1.67 (m, 1
H, H-14), 1.71 (m, 1 H, H-2), 1.72 (d, 3 H, J = 0.8
Hz, H-17), 1.74 (m, 1 H, H-10), 1.86 (m, 1 H, H-18), 1.88 (m, 1
H, H-9), 2.04 (t, 1 H, J = 11.0
Hz, H-5), 2.17 (dd, 1 H, J = 13.5,
12.9 Hz, H-2), 2.35 (dt, 1 H,
J = 14.6,
4.1 Hz, H-9), 2.56 (dd, 1 H, J = 11.5,
5.2 Hz, H-5), 4.63 (td, 1 H, J = 10.2,
5.2 Hz, H-6), 5.14 (dt, 1 H, J = 9.9, 1.4
Hz, H-7), 5.21 (d, 1 H, J = 11.8
Hz, H-3). ¹³C NMR (150 MHz, CDCl3): δ = 16.8
(C-16), 17.9 (C-20), 18.9 (C-19), 19.7 (C-17), 23.7 (C-15), 25.9
(C-10), 30.5 (C-13), 35.0 (C-18), 35.7 (C-9), 40.8 (C-14), 43.2
(C-2), 44.4 (C-1), 46.0 (C-11), 49.0 (C-5), 66.7 (C-6), 87.6 (C-12),
126.5 (C-3), 129.3 (C-7), 132.8 (C-4), 137.7 (C-8). MS (CI): m/z = 307 [M + H]+,
306, 305, 290, 289, 288, 271 (base), 221, 219. HRMS (CI): m/z [M + H]+ calcd
for C20H35O2: 307.2637; found: 307.2640.
IR: 3350 cm-¹.
Compound 3: [α]D +34.3
(c = 0.8, CHCl3). ¹H
NMR (600 MHz, CDCl3): δ = 0.91 (d,
3 H, J = 6.8 Hz, H-20), 0.99
(d,
3 H, J = 6.8 Hz,
H-19), 1.01 (s, 3 H, H-15), 1.36 (m, 1 H, H-14), 1.41 (m, 1 H, H-10),
1.51 (m, 1 H, H-13), 1.53 (m, 1 H, H-14), 1.54 (m, 1 H, H-11), 1.60
(s, 3 H, H-16), 1.66 (m,
1 H, H-10), 1.74 (m, 1 H, H-2),
1.76 (m, 1 H, H-13), 1.78 (d, 3 H, J = 1.4
Hz, H-17), 1.84 (sept, 1 H, J = 6.8
Hz, H-18), 1.96 (ddd, 1 H, J = 13.7,
10.6, 3.7 Hz, H-9), 2.02 (t, 1 H, J = 11.0
Hz, H-5), 2.33 (dt, 1 H, J = 13.7,
3.7 Hz, H-9), 2.47 (t, 1 H, J = 12.6
Hz, H-2), 2.57 (dd, 1 H, J = 11.6,
5.2 Hz, H-5), 4.68 (td, 1 H, J = 11.0,
5.2 Hz, H-6), 5.08 (dt, 1 H, J = 11.0, 1.4
Hz, H-7), 5.18 (dd, 1 H, J = 12.6,
2.2 Hz, H-3). ¹³C NMR (150 MHz, CDCl3): δ = 16.7
(C-16), 17.9 (C-20), 19.0 (C-19), 19.9 (C-17), 23.8 (C-15), 28.4
(C-10), 31.5 (C-18), 35.1 (C-13), 35.9 (C-9), 40.5 (C-14), 44.1
(C-1), 44.9 (C-2), 49.2 (C-5), 51.5 (C-11), 66.9 (C-6), 87.1 (C-12),
126.5 (C-3), 129.6 (C-7), 133.5 (C-4), 138.2 (C-8). MS (CI): m/z = 306 [M]+,
305, 289, 271 (base). HRMS (CI): m/z [M]+ calcd
for C20H34O2: 306.2559; found:
306.2570. IR: 3400 cm-¹.
Compound 4: [α]D +88.5
(c = 0.3, CHCl3). ¹H
NMR (600 MHz, CDCl3): δ = 1.17 (s,
3 H, H-15), 1.41-1.46 (m, 4 H, H-2, H-10, H-14), 1.47 (s,
3 H, H-16) 1.59 (s, 3 H, H-20), 1.60 (s, 3 H, H-19), 1.64 (m, 1
H, H-14), 1.78 (d, 3 H, J = 1.1
Hz, H-17), 2.09 (t, 1 H, J = 11.3
Hz, H-5), 2.03 (m, 1 H, H-2), 2.05 (m, 1 H, H-9), 2.20 (m, 2 H,
H-13), 2.29 (m, 1 H, H-9), 2.28 (m, 1 H, H-11), 2.65 (dd, 1 H, J = 11.3, 5.5 Hz, H-5), 4.65
(td, 1 H, J = 11.3, 5.5 Hz,
H-6), 5.11 (d, 1 H, J = 10.0 Hz,
H-7), 5.37 (dd, 1 H, J = 12.5,
3.3 Hz, H-3). ¹³C NMR (150 MHz, CDCl3): δ = 16.4
(C-17), 16.5 (C-16), 21.1 (C-19), 21.7 (C-20), 23.6 (C-15), 27.3
(C-10), 28.2 (C-13), 38.0 (C-9), 38.6 (C-2), 40.5 (C-14), 41.9 (C-11),
48.6 (C-1), 49.4 (C-5), 66.4 (C-6), 122.3 (C-18), 128.3 (C-3), 131.8
(C-7), 133.1 (C-4), 137.2 (C-8), 142.1 (C-12). MS (CI): m/z = 288 [M]+,
271 (base), 219, 191, 89. HRMS (CI): m/z [M]+ calcd for
C20H32O: 288.2453; found: 288.2461. IR: 3390
cm-¹.
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Ohta K.
Kamakura T.
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