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mL). The combined organic extracts were dried over
Na2SO4. The solvent was removed under vacuum, and the
residue was purified by flash column chromatography on
silica gel (petroleum ether/ethyl acetate = 8/1) to give ke-
tone 5 (200 mg) in 70% yield.
4
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1H NMR (500 MHz, CDCl3): δ 6.95 (s, 1H), 6.85 (t, J =
3.8 Hz, 1H), 6.29 (s, 1H), 4.87 (s, 2H), 4.77 (s, 2H), 4.19
(dd, J = 5.7, 2.2 Hz, 2H), 4.01 (dd, J = 5.7, 3.0 Hz, 2H),
3.89 (s, 3H), 3.84 (s, 3H), 3.57 (q, J = 7.4 Hz, 1H), 3.42 (s,
3H), 3.13 (dd, J = 16.8, 5.1 Hz, 1H), 2.81 (dd, J = 16.8, 5.1
Hz, 1H), 2.20 (m, 2H), 1.74 (m, 4H), 1.37 (d, J = 7.0 Hz,
3H); 13C NMR (125 MHz, CDCl3): δ 199.0, 163.1, 149.6,
148.0, 145.5, 143.5, 139.4, 123.8, 114.9, 106.3, 103.1,
100.9, 96.1, 77.2, 65.0, 64.9, 62.0, 58.8, 56.4, 55.2, 45.5,
34.0, 29.3, 25.7, 19.6, 18.6.
Synthesis of model compound (4)
5
6
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To a solution of ketone 5 (33 mg, 0.073 mmol) in CH2Cl2 (5
mL) was added InCl3 (16 mg, 0.073 mmol), and the mixture
was stirred at 40 °C under N2 for 8 h. The reaction mixture
was filtrate through a pad of celite, and washed with EtOAc
(3 × 5 mL). The filtrate was concentrated under vacuum,
and the residue was purified by flash column chromatog-
raphy on silica gel (petroleum ether/ethyl acetate = 30/1) to
1
give the annulated product 4 (18 mg) in 53% yield. H
NMR (500 MHz, CDCl3): δ 7.12 (s, 2H), 4.87 (m, 4H), 4.77
(m, 4H), 4.32 (s, 1H), 4.22 (s, 1H), 3.90 (s, 6H), 3.89 (s,
6H), 3.50 (m, 1H), 3.243.19 (m, 6H), 2.75 (m, 1H),
2.552.33 (m, 8H), 1.45 (d, J = 7.0 Hz, 3H), 1.32 (d, J =
7.0 Hz, 3H). HRMS (ESI) calcd for C23H29O7 [M+H]+
417.1908; found: 417.1870.
This work was financially supported by the grants of National Basic Re-
search Program (973 Program, 2010CB833201 & 2009CB940904),
the National Science and Technology Major Project “Development of Key
Technology for the Combinatorial Synthesis of Privileged Scaffolds”
(2009ZX09501–012), and the National Natural Science Foundation of
China (20821062, 20832003 and 20902007).
7
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3