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(s) Lazzarotto, M.; Hammerer, L.; Hetmann, M.; Borg, A.;
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Renaud, P. Synthesis 2005, 1459.
Funding Information
This work was supported by the National Natural Science Foundation
of China (21772078 and 21472075) and the Fundamental Research
Funds for the Central Universities (2682019CX70, 2682019CX71, and
2682020CX55). We also thank Science and Technology Department of
Sichuan Province (2020JDRC0021).
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References and Notes
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(2) For a review, see: Ping, Y.; Kong, W. Synthesis 2020, 52, 979.
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(10) In a 100 mL round-bottom flask, enol ether 7 (1.50 g, 3.1 mmol)
was dissolved in anhydrous CH2Cl2 (35 mL) and cooled to 0 °C.
To this solution was added TBCD (97%, 1.57 g, 3.7 mmol, 1.2
equiv) portionwise, and the mixture was stirred for 30 min at 0
°C. A solution of allyl alcohol (3.6 mL, 62 mmol, 20.0 equiv) in
CH2Cl2 (5 mL) was then added dropwise, and the resulting
mixture was gradually warmed to room temperature and
stirred further for 9 h. The reaction was quenched with satu-
rated aqueous NaHCO3 (3 mL), Na2SO3 (3 mL), and stirred
further for 30 min. The resulting mixture was extracted with
CH2Cl2 (2 × 50 mL), and the combined organic layers were
washed with water (2 × 15 mL) and brine (15 mL), respectively,
dried over Na2SO4, filtered, and concentrated under reduced
pressure. The crude product was purified by flash column chro-
matography (petroleum ether/EtOAc
= 10:1 → petroleum
ether/EtOAc = 4:1) on silica gel to afford 8 (1.519 g, 79% yield) as
a yellow oil. Rf = 0.36 (petroleum ether/EtOAc = 2:1). IR (film):
max = 2930, 2838, 1590, 1504, 1479, 1461, 1422, 1383, 1326,
1265, 1229, 1128, 1037, 929, 845, 792, 736, 701, 685, 582 cm–1
.
1H NMR (400 MHz, CDCl3): (major isomer) = 7.19 (s, 1 H), 6.99
(s, 1 H), 6.52 (s, 2 H), 5.93 (s, 1 H), 5.89 (s, 1 H), 5.86–5.80 (m, 1
H), 5.35 (dd, J = 17.2, 1.6 Hz, 1 H), 5.13 (dd, J = 10.8, 1.6 Hz, 1 H),
4.76 (d, J = 10.8 Hz, 1 H), 4.55 (dd, J = 11.2, 2.8 Hz, 1 H), 4.26 (dd,
J = 13.2, 4.8 Hz, 1 H), 4.00 (d, J = 2.4 Hz, 1 H), 3.88 (dd, J = 12.8,
5.2 Hz, 1 H), 3.76 (s, 6 H), 3.74 (s, 3 H), 3.31 (s, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): = 153.3 (2 C), 148.7, 147.3, 137.23,
137.17, 135.6, 133.8, 119.0, 116.7, 107.0, 105.3 (2 C), 102.0,
101.8, 90.5, 69.7, 60.8, 57.7, 57.3, 56.21 (2 C), 56.17 ppm. HRMS
(ESI): m/z calcd for C23H26O779BrINa+ [M + Na]+: 642.9799;
found: 642.9791.
(6) For reviews, see: (a) Peng, Y. Lignans, Lignins, and Resveratrols,
In From Biosynthesis to Total Synthesis: Strategies and Tactics for
Natural Products; Zografos, A. L., Ed.; John Wiley & Sons: Hobo-
ken, 2016, Chap. 10, 331–379. (b) Liu, Y.-Q.; Yang, L.; Tian, X.
Curr. Bioact. Compd. 2007, 3, 37. (c) Sellars, J. D.; Steel, P. G. Eur.
J. Org. Chem. 2007, 3815. For past syntheses of podophyllotoxin
(3), see: (d) Ting, C. P.; Tschanen, E.; Jang, E.; Maimone, T. J. Tet-
rahedron 2019, 75, 3299. (e) Hajra, S.; Garai, S.; Hazra, S. Org.
Lett. 2017, 19, 6530. (f) Ting, C. P.; Maimone, T. J. Angew. Chem.
Int. Ed. 2014, 53, 3115. (g) Wu, Y.; Zhao, J.; Chen, J.; Pan, C.; Li, L.;
(11) Xiao, J.; Nan, G.; Wang, Y.-W.; Peng, Y. Molecules 2018, 23, 3037.
© 2020. Thieme. All rights reserved. Synlett 2020, 31, A–C