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29 Coupling reaction procedure for {2-azidophenyl)-(1-methylene-3,4-dihydro-1H-pyrido[3,4-b]indol-2
(9H)-yl}methanone (5a): To a stirred solution of 3 (0.250 g, 1.53 mmol) in CH2Cl2 (10
mL) was added Et3N (0.22 mL, 1.63 mmol) dropwise at 0 ˚C
over 10 min, then 2-azidobenzoyl chloride (0.295 g, 1.62 mmol) dissolved
in CH2Cl2 (5 mL) was added at the same temperature.
The reaction was brought to r.t. and stirred for another 2 h.
After completion of the reaction, the solvent was evaporated and
extracted with CH2Cl2 (3 × 20 mL),
washed with aqueous NaHCO3 followed by brine, separated,
and dried over anhydrous Na2SO4. The combined
organic extracts were evaporated under reduced pressure and further
purified by column chromatography with EtOAc-hexane (1:1)
as eluent to afford 5a in 84% yield
as a white solid; mp 86-88 ˚C. IR (KBr):
3381, 2105, 1638, 1415 cm-¹; ¹H
NMR (300 MHz, CDCl3): δ = 8.12 (br
s, 1 H), 7.53 (d, J = 7.55 Hz,
1 H), 7.36-7.43 (m, 2 H), 7.32 (d, J = 7.55 Hz,
1 H), 7.20-7.25 (m, 1 H), 7.11-7.16
(m, 3 H), 4.93 (s, 1 H), 4.07 (s, 1 H), 4.00
(t, J = 8.58,
9.09 Hz, 2 H), 3.24 (t, J = 8.08 Hz,
2 H); ¹³C NMR (75 MHz, CDCl3): δ = 167.6,
136.9, 132.3, 132.1, 130.3, 129.1, 128.2, 126.7, 125.1, 124.7, 123.5,
119.9, 119.0, 118.4, 112.0, 111.1, 101.8, 41.1, 29.6; HRMS (ESI): m/z [M + Na]+ calcd
for C19H15N5O: 352.1174; found: 352.1182.
30 Oxidation reaction procedure
for 2-(2-azidobenzoyl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indol-1-one (6a):
To a stirred solution of 5a (0.400 g, 1.13
mmol) in anhydrous acetone (20 mL) was added KMnO4 (0.264
g, 1. 70 mmol) at r.t. and the mixture was stirred for 12 h.
The solvent was evaporated under reduced pressure and the reaction
mixture was diluted with EtOAc (40 mL) and filtered through Celite. The
organic layer was washed with aqueous NaHCO3 followed
by brine and dried over anhydrous Na2SO4.
After filtration and evaporation, the crude product was purified
by column chromatography, eluting with EtOAc-hexane (7:3) to
afford 6a in 67% yield as a white
solid; mp 87-90 ˚C. IR (KBr): 3421, 2111,
1697, 1634 cm-¹; ¹H
NMR (400 MHz, CDCl3): δ = 8.18 (br
s, 1 H), 7.84 (d, J = 7.84 Hz,
1 H), 7.63-7.59 (m, 2 H), 7.38-7.32
(m, 1 H), 7.23-7.20 (m, 2 H), 7.18 (d, J = 7.55 Hz,
1 H), 7.16-7.19 (m, 1 H), 4.43 (br, 2 H),
3.24 (t, J = 8.10 Hz,
2 H); ¹³C NMR (100 MHz, CDCl3): δ = 167.9,
161.2, 142.6, 137.8, 132.6, 130.1, 129.5, 128.1, 126.5, 124.8, 124.6,
123.4, 119.8, 118.9, 118.0, 101.9, 41.9, 21.7; HRMS (ESI): m/z [M]+ calcd
for C18H13N5O2Na: 354.3186;
found: 354.3207.
31 Typical procedure for preparation
of rutaecarpine (1a): A mixture of 6a (0.100 g, 0.302 mmol) in MeOH (2.0 mL)
and Ni2B (0.114 g, 0.906 mmol) and 1.0 M HCl (1.0 mL)
in a glass tube was placed in a microwave reactor (CEM Discovery
LabMate) and irradiated at 70 W for 2 min, during
which time the temperature was kept at 52 ˚C with cooling.
The reaction mixture was brought to ambient temperature and the
solvent was evaporated, the residue was neutralized with saturated
aqueous 5% NaHCO3 solution, and then extracted
with EtOAc (3 × 25 mL). The combined organic
phases were washed with brine, dried over Na2SO4, filtered
and evaporated under reduced pressure. The crude product thus obtained
was purified by column chroma-tography on silica (60-120
mesh) to afford the final compound 1a (0.072
g, 90%); mp 254-255 ˚C. ¹H
NMR (400 MHz, CDCl3): δ = 9.25 (br
s, 1 H), 8.33 (dd, J = 1.23, 7.85 Hz,
1 H), 7.62-7.74 (m, 3 H), 7.43-7.69
(m, 2 H), 7.35 (dt, J = 1.22,
6.85 Hz, 1 H), 7.20 (t, J = 8.44 Hz,
1 H), 4.57 (t, J = 6.96 Hz,
2 H), 3.25 (t, J = 6.95 Hz,
2 H); ¹³C NMR (100 MHz, CDCl3): δ = 161.6,
147.5, 144.9, 138.2, 134.3, 127.2, 126.6, 126.1, 125.6, 125.5, 121.3,
120.6, 120.1, 118.3, 112.1, 19.6, 41.1, 20.2; HRMS (ESI): m/z [M + H]+
˙
calcd for C18H13N3O:
287.1054; found: 287.1057.
Euxylophoricine A (1b): Yield: 0.043 g (82%); mp
293-295 ˚C; ¹H NMR
(300 MHz, CDCl3): δ = 9.25 (br s, 1 H), 7.65
(s, 1 H), 7.63 (d, J = 8.1 Hz,
1 H), 7.44 (d, J = 8.1 Hz, 1 H),
7.35 (dd, J = 7.8,
8.1 Hz, 1 H), 7.20 (t, J = 7.8 Hz, 1 H),
7.06 (s, 1 H), 4.60 (t, J = 7.0 Hz,
2 H), 4.01 (s, 3 H), 3.99 (s, 3 H), 3.24
(t, J = 7.0 Hz,
2 H); ¹³C NMR (75 MHz, CDCl3): δ = 161.1,
155.1, 148.7, 143.9, 143.6, 138.2, 127.3, 125.7, 125.3, 120.6, 119.9,
117.6, 114.5, 111.9, 107.1, 106.4, 56.3, 56.2, 41.1, 19.6; HRMS: m/z [M + H]+
˙
calcd for C20H17N3O3:
347.1263; found: 347.1266.
Euxylophoricine C (1c): Yield: 0.041 g (80%); mp
307-309 ˚C; ¹H NMR
(300 MHz, CDCl3): δ = 9.10 (br s, 1 H), 7.65
(s, 1 H), 7.64 (d, J = 6.95 Hz,
1 H), 7.44 (d, J = 6.92 Hz,
1 H), 7.36 (t, J = 6.95 Hz,
1 H), 7.20 (t, J = 6.9 Hz,
1 H), 7.06 (s, 1 H), 6.10 (s, 2 H), 4.57
(t, J = 6.9 Hz,
2 H), 3.27 (t, J = 6.9 Hz,
2 H); ¹³C NMR (75 MHz, CDCl3): δ = 160.9,
153.5, 147.1, 143.9, 143.8, 138.1, 127.2, 125.7, 125.4, 120.6, 120.0,
117.6, 116.1, 111.9, 105.9, 104.2, 102.5, 41.8, 19.8; HRMS: m/z [M + H]+
˙
calcd for C19H13N3O3:
331.0955; found: 331.0961.