(3 × 6 ml). The combined organic extracts were dried (MgSO4)
and concentrated under reduced pressure. The residual oil in
dichloromethane was filtered through a short column (0.5 cm)
of silica gel and the filtrate was concentrated to give the (S)-
(ϩ)-pyranobenzoquinone 5 (41 mg, 93%) as a yellow crystalline
solid, mp 100–103 ЊC; [α]D ϩ195 (c 0.64, CHCl3). νmax 1658,
1647, 1590, 1225 cmϪ1. All other spectroscopic data were iden-
tical to those of the ( )-benzoquinone 5 obtained by oxidation
of ( )-dimethoxypyran 21.
(S)-(؉)-3,4-Dihydro-7,9-dihydroxy-3-methyl-1H-naphtho-
[2,3-c]pyran-5,10-dione 29. To the (S)-(ϩ)-pyranobenzo-
quinone 5 (42 mg, 0.163 mmol) in toluene (1.5 ml) was added
1-methoxy-1,3-bis(trimethylsilyloxy)buta-1,3-diene 12 (106 mg,
0.407 mmol) in toluene (0.5 ml). The mixture was heated at
reflux for 3 h and allowed to cool to room temperature. Silica
(200 mg) was added and the solution was stirred for a further
30 min. After removal of the solvent under reduced pressure
the residue was filtered slowly through a short column of silica
(dichloromethane–ethyl acetate 1 : 1 ϩ 1% formic acid). The
yellow fractions were combined, concentrated, filtered through
Sephadex LH-20 with dichloromethane–methanol 1 : 1 as
eluant and crystallised from chloroform to give the (S)-(ϩ)-
pyranonaphthoquinone 29 (31 mg, 73%) as yellow needles, mp
171–173 ЊC (decomp.) [( )-form, mp 179–183 ЊC (decomp.)];
[α]D ϩ160 (c 0.28, MeOH). νmax 3421br, 1639, 1614, 1319, 1167,
1153 cmϪ1 [( )-form, 3414br, 1638, 1613, 1318, 1167, 1153
cmϪ1]. λmax (EtOH) 219 (log ε 4.33), 270 (4.02), 290 (3.92), 429
nm (3.39); (EtOH ϩ 1 drop 1 M aq. NaOH) 208 (log ε 4.76),
232 (4.20), 294 (3.99), 395 (2.37), 530 nm (3.25). δH (400 MHz,
d6-acetone) 1.30 (3H, d, J 6.1 Hz, 3-Me), 2.12 (1H, dddd, J 18.8,
10.0, 4.1 and 2.5 Hz, Hax4), 2.64 (1H, ddd, J 18.8, 3.6 and 2.9
Hz, Heq4), 3.67 (1H, m, H3), 4.42 (1H, ddd, J 18.6, 4.1 and 3.6
Hz, Hax1), 4.69 (1H, dd, J 18.6 and 2.5 Hz, Heq1), 6.54 (1H, d,
J 2.3 Hz, H8), 7.01 (1H, d, J 2.3 Hz, H6), 10.01 (1H, br s,
7-OH), 12.05 (1H, s, 9-OH). δC (100 MHz, d6-acetone) 21.4
(3-Me), 30.1 (C4), 63.3 (C1), 70.0 (C3), 108.1 (C8), 108.9 (C6),
109.3 (C9a), 134.8 (C5a), 142.8 (C4a/10a), 143.4 (C4a/10a),
165.1 (C9), 165.4 (C7), 183.2 (C5), 187.6 (C10). Mass spectrum
(EI) m/z 260 (Mϩ, 28%), 86 (33), 84 (54), 71 (100), 70 (26), 69
(56).
( )-3,4-Dihydro-9-hydroxy-7-methoxy-3-methyl-1H-naphtho-
[2,3-c]pyran-5,10-dione 28. To the ( )-pyranobenzoquinone 5
(9 mg, 0.035 mmol) in toluene (1 ml) was added a solution
of 1,3-dimethoxy-1-trimethylsilyloxybuta-1,3-diene 11 (18 mg,
0.089 mmol) in toluene (0.5 ml) and the mixture was heated
under reflux for 15 h. After cooling, the solution was concen-
trated under reduced pressure and filtered slowly through a
short column of silica (dichloromethane–ethyl acetate 2 : 1 ϩ
1% formic acid). The yellow fractions were combined, con-
centrated, further chromatographed (50 : 49 : 1 toluene–ethyl
formate–formic acid, RF 0.85) and crystallised from
dichloromethane–hexane to give the ( )-pyranonaphtho-
quinone 28 (4 mg, 42%) as yellow plates, mp 161–162 ЊC
(Found: C, 65.7; H, 5.1. C15H14O5 requires C, 65.7; H, 5.1%).
νmax 3439br, 2981, 1658, 1641, 1613, 1311, 1199, 1160 cmϪ1
.
λmax (EtOH) 204 (log ε 4.49), 218 (4.40), 268 (3.98), 285sh
(3.78), 429 nm (3.46); (EtOH ϩ 1 drop 1 M aq. NaOH) 209 (log
ε 4.96), 231 (4.32), 285 (3.88), 527 nm (3.35). δH (400 MHz) 1.38
(3H, d, J 6.1 Hz, 3-Me), 2.28 (1H, dddd, J 19.0, 9.7, 4.2 and 2.6
Hz, Hax4), 2.72 (1H, ddd, J 19.0, 3.5 and 2.9 Hz, Heq4), 3.67
(1H, m, H3), 3.90 (3H, s, OMe), 4.51 (1H, ddd, J 18.8, 4.2 and
3.5 Hz, Hax1), 4.84 (1H, dd, J 18.8 and 2.6 Hz, Heq1), 6.62 (1H,
d, J 2.4 Hz, H8), 7.19 (1H, d, J 2.4 Hz, H6), 12.13 (1H, s, OH).
δC (100 MHz) 21.2 (3-Me), 29.5 (C4), 56.0 (OMe), 63.0 (C1),
69.6 (C3), 106.0, 108.1, 109.1, 133.4 (C5a), 142.3, 142.8, 164.3,
166.0, 182.9 (C5), 186.7 (C10). Mass spectrum (EI) m/z 274
(Mϩ, 100%), 245 (31), 231 (25), 230 (26), 202 (27), 201 (28), 108
(22), 72 (24), 71 (30).
(1R,3S)-(؊)-Thysanone 1. To the (S)-(ϩ)-pyranonaphtho-
quinone 29 (15 mg, 0.057 mmol) in carbon tetrachloride (14 ml)
was added bromine (9.2 mg, 0.056 mmol) in carbon tetra-
chloride (1.1 ml) and the solution was irradiated with a 375 W
tungsten lamp for 30 min. After removal of solvent under
reduced pressure the resultant yellow oil was dissolved in tetra-
hydrofuran (6 ml) and water (2 ml) and stirred at room
temperature for 1 h. Dilution with water (10 ml) followed by
extraction with chloroform (3 × 5 ml), drying (MgSO4) of the
combined organic extracts and concentration under reduced
pressure gave a yellow solid that was purified by preparative
thin-layer chromatography (50 : 49 : 1 toluene–ethyl formate–
formic acid, RF 0.40) and crystallised from methanol to give
(1R,3S)-(Ϫ)-thysanone 1 (8.3 mg, 85%) as yellow needles,
mp 197–198 ЊC (decomp.) [lit.3 mp 205–206 ЊC (decomp.)].
[α]D Ϫ29.7 (c 0.002, MeOH) {lit.3 [α]D ϩ29 (c 1.62, MeOH)}.
CD 257 (∆ε ϩ2.8), 296 (Ϫ3.1), 417 (Ϫ0.1), 445 nm (Ϫ0.3)
(Found: Mϩ, 276.0625, C14H12O6 requires Mϩ, 276.0634). νmax
3411br, 2924, 1647, 1610, 1390, 1323, 1274, 1155, 1075 cmϪ1
[( )-form, 3409br, 2925, 1647, 1611, 1390, 1322, 1276, 1172,
1076 cmϪ1]. λmax (MeOH) 219 (log ε 4.33), 263 (4.04), 288sh
(3.94), 421 nm (3.38). δH (400 MHz, d6-acetone) see Table 2.
δH (400 MHz, CDCl3) 1.40 (3H, d, J 6.4 Hz, 3-Me), 2.24
(1H, dd, J 19.6 and 11.1 Hz, Hax4), 2.75 (1H, dd, J 19.6 and
3.2 Hz, Heq4), 4.36 (1H, m, H3), 6.05 (1H, s, H1), 6.63 (1H, d,
J 2.5 Hz, H8), 7.11 (1H, d, J 2.5 Hz, H6), 12.10 (1H, s, 9-OH).
δC (100 MHz, d6-acetone) see Table 2. Mass spectrum (EI)
m/z 276 (Mϩ, 13%), 260 (37), 259 (26), 258 (100), 257 (24), 256
(21), 243 (22), 232 (24), 231 (20), 230 (25), 229 (24), 215 (22),
204 (20), 137 (26), 128 (30), 115 (21), 83 (24), 81 (24), 79 (20), 77
(31), 73 (28), 71 (43), 70 (25), 69 (83), 67 (27), 65 (24), 64 (34), 63
(25), 60 (35), 57 (63), 56 (24), 55 (70), 53 (27), 51 (37).
1-Methoxy-1,3-bis(trimethylsilyloxy)buta-1,3-diene12. To a
solution of LDA [prepared from diisopropylamine (9.15 g,
90 mmol) in tetrahydrofuran (100 ml) and n-butyllithium
(60.0 ml, 1.5 M in hexane, 90 mmol) at 0 ЊC, then cooled to
Ϫ78 ЊC] was added methyl acetoacetate (10 g, 86 mmol)
dropwise over 1 h. After a further 45 min chlorotrimethylsilane
(11.2 g, 103 mmol) was added at Ϫ78 ЊC and the solution was
allowed to warm to room temperature (2 h), filtered through
Celite® and concentrated under reduced pressure. The residual
oil was diluted with dry pentane (10 ml), filtered through
Celite®, and the filtrate was concentrated and the residual oil
distilled to give methyl (E)-3-trimethylsilyloxybut-2-enoate
(9.69 g, 60%) as a colourless liquid, bp 70–72 ЊC/8 mmHg (lit.23
59–61 ЊC/2.0 mmHg). νmax 2951, 1711, 1618, 1136, 1037, 846
cmϪ1. δH (300 MHz) 0.26 (9H, s, SiMe3), 2.26 (3H, s, H34), 3.65
(3H, s, OMe), 5.12 (1H, s, H2). δC (75 MHz) 0.16, 20.7, 50.6,
99.3, 168.3, 169.9.
To a solution of LDA (22.4 mmol, prepared as described
above) was added a solution of methyl (E)-3-trimethylsilyl-
oxybut-2-enoate (4.0 g, 21.4 mmol) in tetrahydrofuran (4 ml)
over 15 min. After a further 45 min chlorotrimethylsilane (2.78
g, 25.6 mmol) was added at Ϫ78 ЊC and the solution was
allowed to warm to room temperature (2 h) and concentrated
under reduced pressure. The residual oil was diluted with
pentane (40 ml), filtered through Celite®, concentrated and dis-
tilled (Kügelrohr) to give the diene 12 (4.28 g, 77%), bp 55–
60 ЊC/0.5 mmHg (lit.21 56–58 ЊC/2.0 mmHg). νmax 2956, 1647,
1250, 1018, 844 cmϪ1. δH (300 MHz) 0.21 and 0.24 (each 9H, s,
SiMe3), 3.55 (3H, s, OMe), 3.94 (1H, d, J 1.5 Hz, Ha4), 4.14
(1H, d, J 1.5 Hz, Hb4), 4.47 (1H, s, H2). δC (75 MHz) 0.20, 0.44,
54.9, 77.5, 89.2, 153.3, 158.6.
(1R,3S)-(؊)-Thysanone methyl acetal 2. To (1R,3S)-(Ϫ)-
thysanone 1 (8.2 mg, 0.028 mmol) in methanol (6 ml) was added
a trace of concentrated sulfuric acid and the mixture was stirred
at room temperature for 16 h. Water (15 ml) was added and
the product was extracted into chloroform (3 × 5 ml) and the
J. Chem. Soc., Perkin Trans. 1, 2002, 938–948
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