U. Iserloh et al. / Tetrahedron: Asymmetry 10 (1999) 2417–2428
2427
174 (15), 131 (100), 104 (26), 103 (25), 91 (32), 77 (13); HRMS calcd for C15H19NO3 (M+) 261.1365,
found 261.1355. rac-24b was synthesized similarly in 84% yield (after recrystallization); white solid, mp
(recrystallized from EtOH) 65.5–67°C; 1H NMR (CDCl3) δ 0.80 (t, 3H, J=7.33 Hz), 1.73 (m, 2H), 3.18
(m, 2H), 3.39 (dd, 1H, J=8.30 Hz and 16.16 Hz), 3.90 (m, 2H), 4.32 (m, 2H), 7.17–7.32 (m, 5H); 13C
NMR (CDCl3) δ 12.0, 29.3, 41.5, 42.5, 43.2, 62.0, 126.4, 127.7, 128.3, 144.0, 153.5, 172.1; IR 2963,
2926, 2873, 1779, 1700, 1497, 1480, 1453, 1388, 1224, 1094; LRMS 247 (M+, 25), 218 (25), 160 (40),
131 (100), 118 (14), 103 (25), 91 (60), 77 (17); HRMS calcd for C14H17NO3 (M+) 247.1208, found
247.1210.
Acknowledgements
We thank the National Science Foundation for funding this work. We also thank Dr. Yoji Oderaotoshi
for helpful comments and suggestions.
References
1. Curran, D. P.; Porter, N. A.; Giese, B. Stereochemistry of Radical Reactions; VCH: Weinheim, 1995.
2. Smadja, W. Synlett 1994, 1–27.
3. Sibi, M. P.; Porter, N. A. Acc. Chem. Res. 1999, 32, 163–171.
4. Review: Renaud, P.; Gerster, M. Angew. Chem., Int. Ed. Engl. 1998, 37, 2562–2579.
5. Chiral bisoxazoline–metal complexes in asymmetric synthesis: Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron:
Asymmetry 1998, 9, 1–45.
6. Oxazolidinone templates: (a) Sibi, M. P.; Ji, J. G.; Wu, J. H.; Gürtler, S.; Porter, N. A. J. Am. Chem. Soc. 1996, 118,
9200–9201; (b) Sibi, M. P.; Ji, J. G. J. Org. Chem. 1997, 62, 3800–3801; (c) Tararov, V. I.; Kuznetzov, N. Y.; Bakhmutov,
V. I.; Ikonnikov, N. S.; Bubnov, Y. N.; Khrustalev, V. N.; Saveleva, T. F.; Belokon, Y. N. J. Chem. Soc., Perkin Trans. 1
1997, 3101–3106; (d) Wu, J. H.; Zhang, G. R.; Porter, N. A. Tetrahedron Lett. 1997, 38, 2067–2070; pyrazole templates:
(e) Sibi, M. P.; Shay, J. J.; Ji, J. G. Tetrahedron Lett. 1997, 38, 5955–5958.
7. Davies, I. W.; Gerena, L.; Castonguay, L.; Senanayake, C. H.; Larsen, R. D.; Verhoeven, T. R.; Reider, P. J. J. Chem. Soc.,
Chem. Commun. 1996, 1753.
8. (a) Kanemasa, S.; Oderaotoshi, Y.; Yamamoto, H.; Tanaka, J.; Wada, E.; Curran, D. P. J. Org. Chem. 1997, 62, 6454–6455;
(b) Kanemasa, S.; Oderaotoshi, Y.; Sakaguchi, S.; Yamamoto, H.; Tanaka, J.; Wada, E.; Curran, D. P. J. Am. Chem.
Soc. 1998, 120, 3074–3088; (c) Kanemasa, S.; Oderaotoshi, Y.; Tanaka, J.; Wada, E. J. Am. Chem. Soc. 1998, 120,
12355–12356.
9. Kanemasa, S.; Oderaotoshi, Y.; Tanaka, J.; Wada, E. Tetrahedron Lett. 1998, 39, 7521–7524.
10. (a) Review: Gant, T. G.; Meyers, A. I. Tetrahedron 1994, 50, 2297–2360; (b) Müller, D.; Umbricht, G.; Weber, B.; Pfaltz,
A. Helv. Chim. Acta 1991, 74, 232–240.
11. Preparation of the 4,6-diiodide 12, dinitrile 13, and diethyl ester 14 of dibenzofuran has been previously described: Tsang,
K. Y.; Diaz, H.; Graciani, N.; Kelly, J. W. J. Am. Chem. Soc. 1994, 116, 3988–4005. Elaboration of diacid 9, dinitrile 13,
diester 14, and diimidate 15 to the desired dihydroxy diamide 11 or DBFOX 6 was prevented by marginal solubility of
starting materials or reaction intermediates.
12. Acidic hydrolysis of recrystallized dinitrile 13 led cleanly to diacid 9. We attempted conversion of this diacid into diacid
chloride 10, but failed with various combinations (THF/oxalyl chloride, DMF/SOCl2, dioxane/SOCl2, acetonitrile/SOCl2,
TFA/SOCl2, DCE/SOCl2/NEt3BnCl). The better solubility of the crude diacid 9, prepared from carboxylation, may account
for this difference.
13. (Diethylamino)sulfur trifluoride (DAST) is more stable and cheaper (US$2.76/mmol, Aldrich) than the Burgess reagent
(US$10.38/mmol, Aldrich).