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(DMSO-d6, 100 MHz) d 165.76, 152.11, 144.23, 141.48, 136.37, solution was adjusted to 4–5 by adding citric acid. Two pha-
132.76, 132.11, 129.51, 128.79, 121.90, 120.82, 120.48, 116.41, ses were separated, and the aqueous solution was extracted
112.97, 112.34, 109.92, 52.07. HRMS (ESI) m/z calcd for twice with ethyl acetate (2 ꢂ 25 mL). Organic extracts were
C
17H13N2O3 [M + H]+: 293.0926, found: 293.0922. IR (KBr, lm) combined and washed twice with brine (2 ꢂ 10 mL). Aer
3440, 3060, 2951, 1702, 1624, 1493, 1430, 1368, 1346, 1260, 738, having been dried over anhydrous MgSO4, the organic solu-
494 cmꢁ1
.
tion was concentrated under vacuum to give a crude solid
1-[5-(Hydroxymethyl)furan-2-yl]-9H-pyrido[3,4-b]indole (per- product, which was puried by ash chromatography
lolyrine 3). Compound 7 (0.470 g, 2.006 mmol) was dissolved in (eluent: MeOH/CH2Cl2 ¼ 1 : 5) to afford pure azin 4 (0.284 g,
acetic acid (3 mL). An aqueous solution of formaldehyde (37% 0.921 mmol) in 92% yield as pale yellow solid, mp 239–
w/w, 1 mL) was added. The resulting solution was then heated 240 C. 1H NMR (DMSO-d6, 400 MHz) d 11.69 (s, 1H, NH in
ꢀ
and stirred at reux for 2 h. Aer the reaction was complete indole), 8.84 (s, 1H), 8.42 (d, J ¼ 7.8 Hz, 1H), 7.87 (d, J ¼
(checked by TLC, eluent: EtOAc/CH2Cl2 ¼ 1 : 3), the solvent was 8.2 Hz, 1H), 7.65 (dd, J1 ¼ 7.8 Hz, J2 ¼ 8.0 Hz, 1H), 7.42 (d, J ¼
removed by vacuum distillation to give a viscous residue, which 3.2 Hz, 1H), 7.34 (dd, J1 ¼ 8.0 Hz, J2 ¼ 8.2 Hz, 1H), 6.62 (d, J ¼
was partitioned between ethyl acetate (30 mL) and an aqueous 3.2 Hz, 1H), 4.69 (s, 2H). 13C NMR (DMSO-d6, 100 MHz)
solution of potassium carbonate (10% w/v, 20 mL). Two phases d 166.64, 157.45, 151.40, 141.53, 137.13, 132.63, 132.06,
were separated, and aqueous phase was extracted again with 129.98, 129.05, 122.17, 121.11, 120.69, 115.85, 112.94, 111.22,
ethyl acetate (20 mL). The organic extracts were combined and 109.37, 56.11. HRMS (ESI) m/z calcd for C17H12N2O4Na [M +
washed twice with brine (2 ꢂ 10 mL). Aer having been dried Na]+: 331.0695, found: 331.0697. IR (KBr, lm) 3242, 2922,
with anhydrous MgSO4, the organic solution was concentrated 1735, 1624, 1612, 1576, 1360, 1321, 1018, 742 cmꢁ1
.
under vacuum to give crude solid, which was puried by ash
chromatography (eluent: MeOH/CH2Cl2 ¼ 1 : 10) to give pure
Conflicts of interest
perlolyrine 3 (0.457 g, 1.729 mmol) in 86% yield as pale yellow
solid, mp 165–166 ꢀC. 1H NMR (DMSO-d6, 400 MHz) d 11.24 (s, There are no conicts to declare.
1H, NH in indole), 8.38 (d, J ¼ 5.1 Hz, 1H), 8.27 (d, J ¼ 7.8 Hz,
1H), 8.08 (d, J ¼ 5.1 Hz, 1H), 7.78 (d, J ¼ 8.2 Hz, 1H), 7.61 (dd, J1
Acknowledgements
¼ 7.8 Hz, J2 ¼ 8.0 Hz, 1H), 7.29 (dd, J1 ¼ 8.0 Hz, J2 ¼ 8.2 Hz, 1H),
7.23 (d, J ¼ 3.3 Hz, 1H), 6.60 (d, J ¼ 3.3 Hz, 1H), 5.50 (t, J ¼ We are grateful to the National Natural Science Foundation of
6.0 Hz, 1H, OH), 4.68 (d, J ¼ 6.0 Hz, 2H). 13C NMR (DMSO-d6, China (No. 20972048) for the nancial support of this work.
100 MHz) d 156.73, 152.14, 140.92, 138.16, 133.14, 130.47,
129.42, 128.39, 121.59, 120.61, 119.68, 113.60, 112.40, 109.62,
Notes and references
109.04, 55.95. HRMS (ESI) calcd for C16H13N2O2 [M + H]+:
265.0977, found: 265.0974. IR (KBr, lm) 3370, 2920, 1629,
1568, 1426, 1317, 1234, 1014, 799, 743, 634 cmꢁ1
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Methyl1-(5-(hydroxymethyl)furan-2-yl)-9H-pyrido[3,4-b]
indole-3-carboxylate 9. Compound 9 was prepared from
compound 8 according to the same procedure as above for
perlolyrine 3. Compound 9 was obtained in 85% yield as
white solid, mp 205–206 ꢀC. 1H NMR (DMSO-d6, 400 MHz)
d 11.63 (s, 1H, NH in indole), 8.87 (s, 1H), 8.44 (d, J ¼ 7.9 Hz,
1H), 7.82 (d, J ¼ 8.2 Hz, 1H), 7.66 (dd, J1 ¼ 7.9 Hz, J2 ¼ 8.0 Hz,
1H), 7.35 (dd, J1 ¼ 8.0 Hz, J2 ¼ 8.2 Hz, 1H), 7.29 (d, J ¼ 3.4 Hz,
1H), 6.63 (d, J ¼ 3.4 Hz, 1H), 5.50 (t, J ¼ 6.1 Hz, 1H, OH), 4.68
(d, J ¼ 6.1 Hz, 2H), 3.94 (s, 3H). 13C NMR (DMSO-d6, 100
MHz) d 165.92, 157.42, 151.21, 141.45, 136.65, 132.99,
132.14, 129.65, 129.01, 122.11, 121.08, 120.71, 116.43,
112.94, 110.99, 109.36, 56.07, 52.23. HRMS (ESI) m/z calcd
for C18H15N2O4 [M + H]+: 323.1032, found: 323.1033. IR
(KBr, lm) 3406, 3297, 2922, 1727, 1565, 1435, 1351, 1251,
1118, 1005, 746 cmꢁ1
.
1-(5-(Hydroxymethyl)furan-2-yl)-9H-pyrido[3,4-b]indole-3-
carboxylic acid (azin 4). Compound 9 (0.323 g, 1.002 mmol)
was dissolved in methanol (5 mL), and then an aqueous
solution of NaOH (3 mol Lꢁ1, 1 mL) was added. The mixture
was then heated and stirred at 50 ꢀC for 5 h. Aer the reaction
was complete (checked by TLC, eluent: EtOAc/CH2Cl2 ¼ 1 : 1),
ethyl acetate (25 mL) and water (20 mL) were added. The
mixture was vigorously stirred, and pH value of the aqueous
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6838 | RSC Adv., 2018, 8, 6834–6839
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