H. Takikawa et al. / Tetrahedron Letters 49 (2008) 2258–2261
2261
Yoshida, M.; Horinouchi, S.; Beppu, T. Agric. Biol. Chem. 1990, 54,
1447–1452.
3. Azuma, M.; Yoshida, M.; Horinouchi, S.; Beppu, T. Biosci. Biotech-
nol. Biochem. 1993, 57, 344–345.
4. Vertesy, L.; Kurz, M.; Paulus, E. F.; Schummer, D.; Hammann, P. J.
Antibiot. 2001, 54, 354–363.
5. (a) Kaiser, F.; Schwink, L.; Velder, J.; Schmalz, H.-G. J. Org. Chem.
2002, 67, 9248–9256; (b) Kaiser, F.; Schwink, L.; Velder, J.; Schmalz,
H.-G. Tetrahedron 2003, 59, 3201–3217; (c) Krohn, K.; Diederichs, J.;
Riaz, M. Tetrahedron 2006, 62, 1223–1230; (d) Sucunza, D.; Demb-
kowski, D.; Neufeind, S.; Velder, J.; Lex, J.; Schmalz, H.-G. Synlett
2007, 2569–2573; (e) Lee, T. S.; Das, A.; Khosla, C. Bioorg. Med.
Chem. 2007, 15, 5207–5218.
6. These results are unpublished.
7. Snieckus, V. Chem. Rev. 1990, 90, 879–933 and references cited there
in.
HRFABMS [M+H]+ obsd 403.0811 calcd for C23H15O7 403.0818;
1H NMR (300 MHz, C5D5N) d = 3.53 (3H, s), 7.22–7.33 (4H, m),
7.43 (1H, d, J = 8.4 Hz), 7.53–7.56 (2H, m), 8.13 (1H, s), 8.21
(1H, d, J = 8.4 Hz); 13C NMR (75 MHz, C5D5N) d = 61.0, 84.1,
116.2, 117.9, 120.9, 121.7, 125.9, 126.6, 127.3, 128.8, 128.9 (two
coincident peaks), 137.7, 140.4, 148.6, 154.4, 159.5, 164.1, 168.5,
181.3.181.9.
16. There were two options for improving the regioselectivity of the key
Diels–Alder reaction. One was Lewis acid-mediated Diels–Alder
reaction, because Lewis acid could often reverse the regioselectivity in
Diels–Alder reaction and generated products that would not
otherwise be observed in a simple non-catalyzed reaction.17,18 Thus,
the following Lewis acids, BF3ꢁOEt2, Et2AlCl, Sc(OTf)3 and
Yb(OTf)3, were tested as an additive.19 However, despite all our
efforts, only a trace amount or none of 17/170 was obtained. These
unfavorable poor yields were probably due to the intrinsic instabilities
of substrates, intermediates and/or products in the presence of Lewis
acid. The other option was the deprotection of MOM group of 11,
because Tietze and his co-workers have reported a complete reversal
of the regioselectivity in Diels–Alder reaction between 16 and juglone
or its methyl ether depending on the protection of a phenolic hydroxyl
group.11,18b Thus, hydroxynaphthoquinone 18 was prepared by the
deprotection of MOM group of 11 (Scheme 4). However, surprisingly,
the Diels–Alder reaction between 16 and 18 gave no desired adducts
(3/30) at all.
17. For Lewis acid-mediated Diels–Alder reaction: (a) Yates, P.; Eaton,
P. J. Am. Chem. Soc. 1960, 82, 4436–4437; (b) Oppolzer, W. In
Comprehensive Organic Synthesis; Trost, B. M., Flemming, I.,
Paquette, L. A., Eds.; Pergamon: Oxford, 1991; Vol. 5, pp 339–345;
(c) Nicolaou, K. C.; Snyder, S. A.; Montagnon, T.; Vassilikogianna-
kis, G. Angew. Chem., Int. Ed. 2002, 41, 1668–1698.
18. For examples: (a) Dickinson, R. A.; Kubela, R.; MacAlpine, G. A.;
Stojanac, Z.; Valenta, Z. Can. J. Chem. 1972, 50, 2377–2380; (b)
Beckman, R. K.; Dolak, T. M.; Culos, K. O. J. Am. Chem. Soc. 1978,
100, 7098–7100; (c) Das, J.; Kubela, R.; MacAlpine, G. A.; Stojanac,
Z.; Valenta, Z. Can. J. Chem. 1979, 57, 3308–3319; (d) Tou, J. S.;
8. Properties of 11: Red-orange powder; mp = 167–168 °C; IR mmax
(Nujol) 1760 (C@O), 1660 (C@O) cmꢀ1; HRFABMS [M+H]+ obs
1
351.0868 calcd for C20H15O6 351.0869; H NMR (300 MHz, CDCl3)
d = 3.52 (3H, s), 5.46 (2H, q-like, J = 6.6 Hz), 6.73 (1H, d,
J = 10.2 Hz), 6.76 (1H, s), 6.87 (1H, d, 10.2 Hz), 7.11–7.26 (5H, m),
7.86 (1H, s); 13C NMR (75 MHz, CDCl3) d = 57.2, 83.2, 95.2, 112.9,
119.3, 120.4, 128.0, 128.5, 129.1, 135.2, 137.9, 138.4, 139.1, 152.8,
159.6, 165.9, 182.4, 183.7.
9. The naphthofuranone 12 was prepared from the commercially
available 3-hydroxy-N-(2-methylphenyl)-2-naphthamide in two steps.
10. (a) Danishefsky, S.; Kitahara, T. J. Am. Chem. Soc. 1974, 96, 7807–
7809; (b) Danishefsky, S. Acc. Chem. Res. 1981, 14, 400–406.
11. Tietze, L. F.; Guntner, C.; Gericke, K. M.; Schuberth, I.; Bunkoczi,
¨
G. Eur. J. Org. Chem. 2005, 2459–2467.
12. Wulff, W. D.; Bauta, W. E.; Kaesler, R. W.; Lankford, P. J.; Miller,
R. A.; Murray, C. K.; Yang, D. C. J. Am. Chem. Soc. 1990, 112,
2642–3659.
13. A mixture of 11 (45 mg, 0.13 mmol) and 16 (0.10 ml, 0.43 mmol) in
CH2Cl2 (5 ml) was stirred at rt for 2 h under Ar. After treating with
SiO2 (2 g) for 30 min, the reaction mixture was filtered and concen-
trated. The residue was treated with K2CO3 (20 mg, 0.15 mmol) in aq
THF (50 vol %; 4 ml) for 30 min, diluted with H2O and extracted with
EtOAc. The organic layer was washed with H2O and brine, dried
(MgSO4), and concentrated. The residue was purified by SiO2 column
chromatography to give a mixture of 17 and 170 (15 mg; 26%).
14. The structures of 17/170 were unambiguously confirmed by the fact
that 17 could be converted to ( )-3.
´
Reusch, W. J. Org. Chem. 1980, 45, 5012–5014; (e) Arseniyadis, S.;
Rodriguez, R.; Spanevello, R.; Camara, J.; Thompson, A.; Guittet,
E.; Ourisson, G. Tetrahedron 1992, 48, 1255–1262; (f) Carreno, M. C.;
˜
Ruano, J. L. G.; Remor, C. Z.; Urbano, A. Tetrahedron: Asymmetry
2000, 11, 4279–4296.
19. The reaction procedure was also analogous to that of Tietze’s11 except
for being performed at ꢀ78 °C. As an additive, BF3ꢁOEt2 (100 mol
%), Et2AlCl (100 mol %), Sc(OTf)3 (5 mol %) or Yb(OTf)3 (5 mol %)
was used, respectively.
15. Properties of synthetic ( )-3: Orange-yellow powder; mp = >250 °C
(decomp.); IR mmax (Nujol) 1730 (C@O), 1660 (C@O) cmꢀ1
;