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The Journal of Organic Chemistry
(m, 1H), 2.03 (s, 3H), 1.97ꢀ1.89 (m, 1H), 1.78ꢀ1.69 (m, 3H), 1.69ꢀ1.60 (m, 2H), 1.52ꢀ1.41 (m, 2H),
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1.41ꢀ1.34 (m, 2H), 1.34ꢀ1.22 (m, 3H), 0.91 (d, J = 6. 1 Hz, 3H), 0.83 (t, J = 12. 5 Hz, 1H). C NMR
(100 MHz, CDCl3) δ 170.5, 70.2, 54.7, 47.1, 46.9, 45.2, 42.8, 41.7, 34.9, 31.1, 31.0, 26.3, 24.6, 24.2,
23.5, 23.1, 21.5, 20.3. HRMS (ESI) m/z calcd for C18H30NO2 [M + H]+:292.2271, found: 292.2271.
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Iodo ketolactam (16)
According to general procedure of method B, βꢀacetyldihydrolycopodine 15 (40 mg, 0.14 mmol),
PIDA (265.4 mg, 0.82 mmol, 6 equiv), iodine (104.3 mg, 0.41 mmol, 3 equiv.) were added in DCE (7
ml, 0.02 M). And the reaction was refluxed at 80°C, after 3 h the reaction was quenched by saturated aq.
sodium thiosulfate solution (4 ml). Flash column chromatography on silica eluting with MeOH/DCM
(1:120) yielded iodo ketolactam 16 as a yellow oil (48.7 mg, 80% yield). IR (KBr) 3435,
2949, 1733, 1691, 1661, 1599, 1363, 1239, 1145, 1039, 1023. 1H NMR (400 MHz, CDCl3) δ 5.12 (t, J =
6. 1 Hz, 1H), 4.82 (dd, J = 13.8, 4.9 Hz, 1H), 3.57 (brs, 1H), 3.06 (td, J = 13.6, 2.9 Hz, 1H), 2.90 (m,
2H), 2.37 (dt, J = 15.6, 6.6 Hz, 1H), 2.12 (s, 3H), 2.07ꢀ1.80 (m, 5H), 1.67ꢀ1.52 (m, 2H), 1.46 (td, J =
13.2, 4.8 Hz, 1H), 1.10 (t, J = 12.5 Hz, 1H), 0.93 (d, J = 6. 1 Hz, 3H). 13C NMR (100 MHz, CDCl3) δ
173.8, 173.0, 169.8, 152.5, 101.4, 68.0, 65.8, 51.7, 46.9, 44.6, 41.3, 37.9, 36.3, 25.5, 23.1, 21.9, 21.4.
HRMS (ESI) m/z calcd for C18H22INO4Na [M + Na]+: 466.0486, found: 466.0489.
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Obscurumine O (17)
To a stirred solution of iodo ketolactam 16 (16.0 mg, 0.04 mmol, 1.0 eq.) in benzene (4 mL) were
added AIBN (1.2 mg, 0.2 mmol) and nBu3SnH (28.0 µl, 0.06 mmol, 1.5 eq.) at rt. After 6 h, the reaction
was quenched by water (4 ml) and extracted with CH2Cl2. The dried (Na2SO4) extract was concentrated
in vacuo and purified by chromatography over silica gel, eluting with MeOH/DCM (1:80) to give obꢀ
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scurumine O 17 as a white amorphous powder (9.2 mg, 0.03 mmol, 80%). H NMR (400 MHz,
CD3OD) δ 6.43 (s, 1H), 5.17 (t, J = 6.3 Hz, 1H), 4.70 (dd, J = 12.1, 3.3 Hz, 1H), 3.35 (d, J = 15.6 Hz,
1H), 3.21 (m, 1H), 3.10ꢀ2.93 (m, 2H), 2.43 (m, 1H), 2.28 (m, 1H), 2.13 (s, 3H), 2.10ꢀ1.89 (m, 3H),
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1.66ꢀ1.43 (m, 3H), 1.31 (s, 1H), 1.18 (t, J = 12.3 Hz, 1H), 0.98 (d, J = 6.1 Hz, 3H). C NMR (100
MHz, CD3OD) δ 178.8, 175.3, 171.7, 158.4, 120.8, 69.7, 64.4, 52.6, 45.0, 43.8, 42.0, 38.6, 38.3, 26.9,
24.2, 23.7, 22.4, 21.2. HRMS (ESI) m/z calcd for C18H23NO4Na [M + Na]+: 340.1519, found: 340.1516.
1H NMR (400 MHz, CDCl3) δ 6.37 (s, 1H), 5.14 (t, J = 6.2 Hz, 1H), 4.84 (m, 1H), 3.03 (m, 1H), 2.89
(m, 3H), 2.37 (m, 1H), 2.12 (s, 3H), 2.08ꢀ1.94 (m, 3H), 1.91ꢀ1.80 (m, 2H), 1.67ꢀ1.53 (m, 2H), 1.48
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(dd, J = 12.6, 4.3 Hz, 1H), 1.18 (t, J = 14.3 Hz, 1H), 0.94 (d, J = 5.8 Hz, 3H). C NMR (100 MHz,
CDCl3) δ 177.5, 171.6, 169.9, 156.5, 120.4, 68.0, 62.5, 51.4, 44.0, 42.7, 40.4, 37.3, 37.3, 25.8, 22.9,
22.8, 22.2, 21.4.
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