G
J. T. Tee et al.
Paper
Synthesis
13C NMR (100 MHz, CDCl3): δ = 204.1, 167.5, 165.4, 165.3, 159.1,
158.5, 158.3, 157.5, 130.5, 125.6, 114.3, 107.1, 104.1, 103.0, 101.1,
99.1, 86.1, 75.6, 55.9, 55.6, 55.5, 55.3, 54.7, 52.2, 50.6, 45.5, 36.3, 31.2,
28.6.
13C NMR (100 MHz, toluene-d8): δ = 203.9, 166.3, 166.2, 165.4, 159.3,
158.4, 158.3, 157.6, 130.3, 127.6, 125.5, 114.5, 107.2, 105.5, 104.0,
103.2, 100.9, 99.1, 86.2, 75.1, 54.8, 54.6, 54.2, 54.1, 51.2, 51.0, 45.8,
36.0, 31.3, 28.4.
13C NMR (100 MHz, toluene-d8, 353 K): δ = 204.2, 166.6, 166.4, 166.0,
165.4, 159.1, 158.9, 158.4, 130.3, 127.6, 125.8, 115.3, 107.4, 106.6,
105.3, 104.1, 101.8, 100.2, 87.5, 75.5, 55.8, 55.3, 55.0, 54.9, 54.6, 51.8,
51.3, 46.5, 36.8, 31.8, 28.7.
The precipitate was filtered and the organic layer was collected and
dried. The residue was purified by column chromatography (hexane–
EtOAc, 8:2) to afford product 24 (60 mg, 85%) as light yellowish liquid.
1H NMR (400 MHz, CDCl3): δ = 7.92 (d, J = 8.8 Hz, 1 H), 7.77 (d, J = 16.0
Hz, 1 H), 7.76 (d, J = 8.8 Hz, 1 H), 7.50 (d, J = 15.7 Hz, 1 H), 7.03 (d,
J = 8.0 Hz, 2 H), 6.80 (d, J = 8.2 Hz, 2 H), 6.78 (d, J = 8.2 Hz, 2 H), 6.52
(m, 3 H)§, 6.43 (d, J = 8.8 Hz, 1 H), 3.91 (s, 3 H, OMe), 3.74 (s, 9 H,
3 × OMe), 3.31 (dt, J = 3.3, 11.3 Hz, 1 H), 2.91 (br d, J = 9.7 Hz, 1 H),
2.81 (t, J = 2.9 Hz, 1 H), 2.51 (t, J = 7.5 Hz, 2 H), 2.17 (dd, J = 11.5, 13.4
Hz, 1 H), 1.98 (m, 1 H), 1.71 (dd, J = 4.9, 13.8 Hz, 1 H), 1.50 (d, J = 13.5
Hz, 2 H)§, 1.34 (m, 1 H)§, 1.34 (s, 3 H)§, 1.07 (s, 3 H), 0.80 (s, 3 H).
§ Signals overlapped.
13C NMR (100 MHz, CDCl3): δ = 186.9, 158.8, 157.6, 156.7, 156.3,
151.8, 150.5, 139.3, 133.5, 129.6, 128.2, 127.2, 126.9, 124.9, 124.4,
119.8, 118.5, 116.9, 112.3, 112.0, 108.7, 100.9, 100.6, 98.6, 72.4, 68.9,
54.0, 53.7, 53.6, 53.5, 39.8, 34.8, 34.3, 33.7, 30.0, 26.3, 24.8, 23.7, 17.8,
15.6.
HRMS (ESI): m/z [M + H]+ calcd for C44H47O8: 703.3271; found:
703.3267
HRMS (ESI): m/z [M + H]+ calcd for C33H37O10: 593.2378; found:
593.2360.
Oxabicycle 22
To a solution of freshly prepared MgI2 (0.23 g, 0.82 mmol) in dry Et2O
(10 mL) was added a solution of adduct 10 (0.05 g, 0.08 mmol) in THF
(10 mL). The mixture was heated at 50 °C for 6 h. The resulting pre-
cipitate was filtered and the organic layer collected and dried. The
residue was purified by column chromatography (hexane–EtOAc, 8:2)
to afford 21 (20 mg, 40%) and oxabicycle 22 (18 mg, 36%) as colorless
crystals; mp 175 °C.
1H NMR (400 MHz, CDCl3): δ = 12.62 (s, 1 H), 12.37 (s, 1 H), 11.38 (br
s, 1 H), 7.82 (d, J = 9.1 Hz, 1 H), 6.88 (d, J = 8.7 Hz, 1 H), 6.50 (dd,
J = 1.8, 8.7 Hz, 1 H), 6.38 (d, J = 2.3 Hz, 1 H), 6.33 (d, J = 2.3 Hz, 1 H),
6.26 (dd, J = 2.3, 8.2 Hz, 1 H), 6.02 (s, 1 H), 4.37 (br d, 1 H)*, 3.88–3.69
(3 × s, 9 H, 3 × OMe), 3.68 (m, 1 H), 3.38 (s, 3 H), 2.29 (br d, J = 12.8 Hz,
1 H), 2.22 (dd, J = 2.7, 13.1 Hz, 1 H), 1.97 (t, J = 12.8 Hz, 1 H), 1.56 (s, 3
H).
Acknowledgment
This research was supported by a PPP grant (PG020/2014A) from the
University of Malaya. We thank Dr. Michael J. C. Buckle for valuable
discussions.
Supporting Information
Supporting information for this article is available online at
1H NMR (400 MHz, DMSO-d6): δ = 12.58 (s, 1 H), 12.13 (s, 1 H), 8.19
(d, J = 8.7 Hz, 1 H), 6.98 (d, J = 8.7 Hz, 1 H), 6.56 (dd, J = 2.3, 9.2 Hz, 1
H), 6.40 (d, J = 2.3 Hz, 1 H), 6.36 (d, J = 2.3 Hz, 1 H), 6.27 (dd, J = 2.3, 8.7
Hz, 1 H), 5.91 (s, 1 H), 4.50 (br d, J = 11.9 Hz, 1 H), 3.78–3.61 (3 × s, 9
H, 3 × OMe), 3.45 (m, 1 H), 3.23 (s, 3 H), 2.38 (br d, J = 11.4 Hz, 1 H),
2.06 (br d, 1 H)*, 1.69 (d, J = 11.9 Hz, 1 H), 1.35 (s, 3 H). * Coupling
constants not measured due to broad resonances.
1H NMR (400 MHz, DMSO-d6, 353 K): δ = 12.52 (s, 1 H), 12.43 (s, 1 H),
8.12 (d, J = 8.7 Hz, 1 H), 6.94 (d, J = 8.7 Hz, 1 H), 6.55 (d, J = 7.6 Hz, 1
H), 6.37 (d, J = 2.5 Hz, 1 H), 6.37 (d, J = 2.5 Hz, 1 H), 6.27 (d, J = 8.5 Hz,
1 H), 5.94 (s, 1 H), 4.47 (br d, J = 11.2 Hz, 1 H), 3.80–3.62 (3 × s, 9 H,
3 × OMe), 3.35 (m, 1 H), 3.28 (s, 3 H), 2.39 (br d, J = 11.4 Hz, 1 H), 2.09
(br d, 1 H)*, 1.70 (m, 1 H), 1.40 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 203.3, 171.3, 165.7, 165.5, 165.0,
162.3, 159.3, 158.2, 155.7, 130.3, 122.5, 114.1, 107.5, 104.2, 102.0,
101.1, 99.2, 94.1, 92.8, 80.3, 55.6, 55.5, 55.3, 55.2, 49.8, 44.9, 35.9,
30.3, 28.6.
13C NMR (100 MHz, DMSO-d6): δ = 205.0, 172.4, 165.8, 164.9, 163.5,
161.7, 159.1, 158.1, 157.5, 132.2, 124.6, 114.3, 107.5, 105.0, 102.6,
101.4, 99.0, 96.0, 91.3, 77.6, 56.2, 56.0, 55.4, 55.4, 50.3, 46.2, 35.1,
30.9, 28.6.
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References
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13C NMR (100 MHz, DMSO-d6, 353 K): not measured.
HRMS (ESI): m/z [M + Na]+ calcd for C31H32O10Na: 587.1893; found:
587.1890.
Oxabicycle 24
To a solution of freshly prepared MgI2 (0.28 g, 1.0 mmol) in dry Et2O
(10 mL) was added a solution of kuwanon V methyl ether 235e (0.072
g, 0.1 mmol) in THF (10 mL). The mixture was heated at 50 °C for 6 h.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–H