HETEROCYCLES, Vol. 70, 2006
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Data for dictamnine (17): mp 131-132 °C (lit.,14 mp 132-134 °C, lit.,4 mp 128-130 °C); H NMR
(CDCl3) 8.29 (d, 1, J = 7.8), 8.01 (d, 1, J = 7.8), 7.69 (dd, 1, J = 7.8, 7.8), 7.64 (d, 1, J = 2.8), 7.46 (dd, 1,
J = 7.8, 7.8), 7.10 (d, 1, J = 2.8), 4.47 (s, 3); 13C NMR (CDCl3) 163.8, 156.8, 145.6, 143.6, 129.6, 127.8,
123.7, 122.3, 118.7, 104.7, 103.4, 59.0. The 1H NMR and 13C NMR (CDCl3) spectral data match those
of a sample purchased from Apin Chemicals LTD.
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Data for 18: H NMR (CDCl3) 8.26 (dd, 1, J = 7.9, 1.2), 7.98 (d, 1, J = 7.9), 7.67 (ddd, 1, J = 7.9, 7.9,
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1.2), 7.44 (ddd, 1, J = 7.9, 7.9, 1.2), 6.90 (s, 1), 4.43 (s, 3), 1.72 (s, 6); C NMR (CDCl3) 163.7, 161.8,
156.3, 145.2, 129.4, 127.7, 123.7, 122.3, 118.9, 104.6, 97.9, 69.5, 59.0, 28.6 (2 C). These data
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correspond to the literature data,14 except that our H NMR data are 0.1 to 0.15 ppm downfield and our
13C NMR data are all about 1.2 ppm downfield.
4-Hydroxy-3-iodo-7,8-dimethoxyquinolin-2(1H)-one (20). A solution of iodine (532 mg, 2.1 mmol)
in warm dioxane (3 mL) was added in portions during 5 min to a refluxing solution of
7,8-dimethoxy-4-hydroxyquinolin-2(1H)-one (19,20 416 mg, 1.9 mmol) and Na2CO3 (767 mg, 7.2 mmol)
in water (7.5 mL). After refluxing for 2 h, the solution was cooled to 5 °C and acidified with AcOH.
The precipitate was collected by filtration and dried at 70 °C for 12 h to give 438 mg (66%) of pure 20:
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mp 183-184 °C; H NMR (CD3OD) 7.74 (d, 1, J = 9.2), 7.03 (d, 1, J = 9.2), 3.97 (s, 3), 3.92 (s, 3); H
NMR (DMSO-d6) 10.93 (br s, 1, NH), 7.70 (d, 1, J = 9.2), 7.00 (d, 1, J = 9.2), 3.83 (s, 3), 3.76 (s, 3); 13C
NMR (DMSO-d6) 162.9, 160.8, 153.5, 133.7, 132.8, 118.5, 109.3, 107.3, 74.6, 60.7, 56.2.
3-Iodo-4,7,8-trimethoxy-quinolin-2(1H)-one (21). A solution of 20 (420 mg, 1.21 mmol) in ethanol
(70 mL) was treated with a 4 molar excess of ethereal diazomethane and stirred at 25 °C for 40 min.
Excess CH2N2 was destroyed by the addition of glacial acetic acid. Evaporation of the solvent gave 458
mg of a gummy residue. Flash chromatography on silica gel (2:1 to 1:2 hexanes/EtOAc) yielded 64.4
mg (14%) of 3-iodo-2,4,7,8-tetramethoxyquinoline followed by 243 mg (56%) of 21.
Data for 3-iodo-2,4,7,8-tetramethoxyquinoline: 1H NMR (CDCl3) 7.69 (d, 1, J = 9.2), 7.14 (d, 1, J = 9.2),
4.15 (s, 3), 4.13 (s, 3), 4.02 (s, 3), 4.01 (s, 3); 13C NMR (CDCl3) 166.4, 160.4, 153.0, 142.2, 142.1, 117.6,
117.5, 112.0, 73.6, 6.1.8, 61.4, 56.8, 55.0.
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Data for 21: mp 218-220 °C; H NMR (CD3OD) 7.60 (d, 1, J = 9.2), 7.09 (d, 1, J = 9.2), 4.02 (s, 3),
3.98 (s, 3), 3.92 (s, 3); 1H NMR (CDCl3) 9.49 (br, 1, NH), 7.51 (d, 1, J = 9.2), 6.87 (d, 1, J = 9.2), 4.02 (s,
3), 3.98 (s, 6); 13C NMR (CDCl3) 167.8, 161.3, 153.5, 133.9, 132.6, 118.7, 111.4, 107.9, 84.1, 61.3, 61.1,
56.2; HRMS (EI) calcd for C12H12NO4I (M+) 360.9811, found 360.9816.
cis-2,3-Dihydro-3-hydroxy-4,7,8-trimethoxy-α,α-dimethylfuro[2,3-b]quinoline-2-methanol (9c),
trans-2,3-Dihydro-3-hydroxy-4,7,8-trimethoxy-α,α-dimethylfuro[2,3-b]quinoline-2-methanol
(7,8-dimethoxymyrtopsine, 9t), and cis-3,4-Dihydro-5,8,9-trimethoxy-2,2-dimethyl-2H-pyrano-
[2,3-b]quinoline-3,4-diol (23c). A solution of 21 (72 mg, 0.2 mmol) in dry THF (5 mL) was stirred