F
S. Wang, G. A. Kraus
Feature
Synthesis
dried over sodium sulfate, and concentrated. Purification by column
chromatography on silica gel [hexane/EtOAc, 3:1 (v/v)] gave the prod-
uct 15.
the same temperature. Then, methyl sorbate (189.0 mg, 1.5 mmol) in
THF (1.0 mL) was added dropwise and the mixture was stirred at
–78 °C (dry ice/acetone bath) for 30 min. Next, the mixture was
warmed to room temperature and stirred 16 h. Hydrochloric acid (2
N, 10 mL) was added to quench the reaction, and the aqueous layer
was extracted with ethyl acetate (2 × 10 mL). The combined organic
layers were dried over sodium sulfate and concentrated. Purification
by column chromatography on silica gel [hexane/EtOAc, 5:1 (v/v)]
gave the product 18.
Yield: 4.83 g (64%); white solid; mp 113–115 °C; Rf = 0.25 [hexane/
EtOAc, 3:1 (v/v)].
1H NMR (600 MHz, DMSO-d6): = 7.36–7.34 (m, 3 H), 7.32–7.28 (m, 3
H), 7.08 (d, J = 8.8 Hz, 1 H), 7.03 (s, 1 H), 3.92 (s, 3 H), 3.78 (s, 3 H).
13C NMR (150 MHz, DMSO-d6): = 166.3, 151.8, 147.7, 134.9, 133.8,
130.1, 129.5, 129.2, 119.7, 114.6, 113.9, 82.7, 56.8, 56.6.
HRMS (ESI-TOF): m/z [M + H]+ calcd for C16H15O4S: 303.0686; found:
Yield: 257.6 mg (81%); yellow solid; mp, 109–111 °C; Rf = 0.10 [hex-
ane/EtOAc, 1:1 (v/v)].
303.0689.
1H NMR (600 MHz, CDCl3): = 9.64 (s, 1 H), 9.40 (s, 1 H), 6.58 (dq, J =
16.0, 1.7 Hz, 1 H), 6.55 (d, J = 8.3 Hz, 1 H), 6.50 (d, J = 8.5 Hz, 1 H), 6.24
(dq, J = 16.0, 6.6 Hz, 1 H), 3.94 (s, 3 H), 3.94 (s, 3 H), 3.91 (s, 3 H), 1.92
(dd, J = 6.6, 1.8 Hz, 3 H).
13C NMR (150 MHz, CDCl3): = 169.1, 150.9, 150.5, 144.2, 143.6,
130.5, 124.5, 118.2, 117.9, 116.4, 114.8, 105.1, 104.1, 56.5, 56.4, 52.3,
19.6.
5,10-Dihydroxy-6,9-dimethoxy-3-methyl-4-(phenylthio)-3,4-di-
hydro-1H-benzo[g]isochromen-1-one (16)
To a stirred solution of 15 (302 mg, 1.0 mmol) in tetrahydrofuran (3.0
mL) was added LiOtBu (1.0 M in tetrahydrofuran, 3.0 mL, 3.0 mmol) at
–78 °C (dry ice/acetone bath). The mixture was stirred for 30 min at
the same temperature. Next, epoxide 4 (213.0 mg, 1.5 mmol) in THF
(1.0 mL) was added dropwise and the mixture was stirred at –78 °C
(dry ice/acetone bath) for 30 min. The mixture was warmed to room
temperature and stirred for 16 h. Hydrochloric acid (2 N, 10 mL) was
added to quench the reaction, and the aqueous layer was extracted
with ethyl acetate (2 × 10 mL). The combined organic layers were
dried over sodium sulfate and concentrated. Purification by column
chromatography on silica gel [hexane/EtOAc, 3:1 (v/v)] gave the prod-
uct 16 along with benzofuran 17.
HRMS (ESI-TOF): m/z [M + H]+ calcd for C17H19O6: 319.1176; found:
319.1175.
Funding Information
We thank the National Science Foundation (NSF) EAGER funding
(Award #1842604) for partial support of this research, and Iowa State
Yield: 206.7 mg (50%); light brown oil; Rf = 0.50 [hexane/EtOAc, 2:1
(v/v)]; dr = 1:1.
University, Department of Chemistry.
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1H NMR (600 MHz, CDCl3): (1:1 mixture of diastereoisomers) =
12.62 (s, 1 H), 12.38 (s, 1 H), 9.79 (s, 1 H), 9.74 (s, 1 H), 7.56 (dd, J = 6.6,
2.9 Hz, 2 H), 7.49–7.45 (m, 2 H), 7.33–7.31 (m, 3 H), 7.19 (ddd,
J = 14.5, 7.8, 6.2 Hz, 3 H), 6.97 (dd, J = 11.3, 8.7 Hz, 2 H), 6.81 (dd,
J = 19.8, 8.7 Hz, 2 H), 4.88 (tdd, J = 8.9, 6.8, 4.3 Hz, 2 H), 4.79 (dd,
J = 9.9, 1.7 Hz, 2 H), 4.04 (s, 3 H), 4.03 (s, 3 H), 3.97 (s, 3 H), 3.95 (s, 3
H), 1.65 (d, J = 6.4 Hz, 3 H), 1.32 (d, J = 6.8 Hz, 3 H).
13C NMR (150 MHz, CDCl3): = 170.1, 168.7, 155.9, 155.8, 154.1,
154.0, 149.6, 149.5, 143.0, 141.0, 135.2, 134.7, 134.4, 133.6, 133.0,
129.5, 129.3, 129.1, 128.7, 128.4, 128.0, 120.8, 120.6, 117.6, 117.2,
112.8, 110.1, 109.9, 107.4, 107.0, 102.1, 101.8, 78.0, 77.7, 57.00, 56.98,
46.0, 44.4, 20.0, 18.7.
Supporting Information
Supporting information for this article is available online at
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References
(1) Chen, M.; Shao, C. L.; Wang, K. L.; Xu, Y.; She, Z. G.; Wang, C. Y.
Tetrahedron 2014, 70, 9132.
(2) Devienne, K. F.; Raddi, M. S. G.; Coelho, R. G.; Vilegas, W. Phyto-
medicine 2005, 12, 378.
HRMS (ESI-TOF): m/z [M + H]+ calcd for C22H21O6S: 413.1053; found:
413.1046.
(3) Parisot, D.; Devys, M.; Férézou, J. P.; Barbier, M. Phytochemistry
1983, 22, 1301.
(4) Kraus, G. A.; Dong, P. Nat. Prod. Commun. 2015, 10, 1025.
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Chem. 2019, 84, 3158.
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4283.
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Chem. 2017, 1704.
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Methyl 5-Hydroxy-6,9-dimethoxy-2-methylnaphtho[1,2-b]furan-
4-carboxylate (17)
Yield: 132.1 mg (42%); yellow solid; mp 156–158 °C; Rf = 0.20
[hexane/EtOAc, 2:1 (v/v)].
1H NMR (600 MHz, CDCl3): = 12.53 (s, 1 H), 7.04 (d, J = 8.7 Hz, 1 H),
6.87 (q, J = 0.9 Hz, 1 H), 6.84 (d, J = 8.7 Hz, 1 H), 4.08 (s, 3 H), 4.07 (s, 3
H), 4.04 (s, 3 H), 2.60 (d, J = 0.8 Hz, 3 H).
13C NMR (150 MHz, CDCl3): = 171.2, 158.9, 155.6, 153.0, 148.4,
142.5, 124.0, 118.5, 114.2, 110.2, 106.0, 104.7, 100.9, 57.1, 56.7, 52.1,
14.3.
HRMS (ESI-TOF): m/z [M + H]+ calcd for C17H17O6: 317.1020; found:
317.1019.
Methyl
(E)-1,4-Dihydroxy-5,8-dimethoxy-3-(prop-1-en-1-yl)-2-
(13) Hassan, N. P. S.; Naysmith, B. J.; Sperry, J.; Brimble, M. A. Tetra-
hedron 2015, 71, 7137.
(14) Hugelshofer, C. L.; Magauer, T. Angew. Chem. Int. Ed. 2014, 53,
11351.
naphthoate (18)
To a stirred solution of 15 (302 mg, 1.0 mmol) in tetrahydrofuran (3.0
mL) was added LiOtBu (1.0 M in tetrahydrofuran, 3.0 mL, 3.0 mmol) at
–78 °C (dry ice/acetone bath). The mixture was stirred for 30 min at
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–G