A novel catalytic and highly enantioselective approach for the synthesis of optically active carbohydrate derivatives

Journal of Organic Chemistry

Volumn 65, Issue 15, 2000, Pages 4487-4497

  Audrain, Hélène ^a   Thorhauge, Jacob ^a   Hazell, Rita G ^a   Jørgensen, Karl Anker ^a  

^a AARHUS UNIVERSITY   (Denmark)

Author keywords

[No Author keywords available]

Indexed keywords

CARBOHYDRATE DERIVATIVE;

ARTICLE; CARBOHYDRATE SYNTHESIS; CATALYSIS; CATALYST; CHEMICAL STRUCTURE; ELECTRON TRANSPORT; OPTICAL ROTATION; REACTION ANALYSIS; STEREOCHEMISTRY;

ALKENES; CARBOHYDRATES; CATALYSIS; CRYSTALLOGRAPHY, X-RAY; MAGNETIC RESONANCE SPECTROSCOPY; MANNOSIDES; MODELS, MOLECULAR; MOLECULAR CONFORMATION; STEREOISOMERISM;

EID: 0034725914     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo9918596     Document Type: Article

References (97)

1. For leading references of inverse-electron demand hetero-Diels-Alder reactions, see, for example: (a) Desimoni, G.; Tacconi, G. Chem. Rev. 1975, 75, 651-692. (b) Boger, D. L.; Weinreb, S. M. Hetero Diels- Alder Methodology in Organic Synthesis; Academic Press: New York, 1987. Tietze, L. F.; Kettschau, G. Stereoselective Heterocyclic Synthesis I; Metz, P., Ed.; Springer: Berlin, 1997; Vol. 189, pp 1-120. Ager, D. J.; East, M. B. Tetrahedron 1993, 49, 5683-5765.
2. For leading references of inverse-electron demand hetero-Diels- Alder reactions, see, for example: (a) Desimoni, G.; Tacconi, G. Chem. Rev. 1975, 75, 651-692. (b) Boger, D. L.; Weinreb, S. M. Hetero Diels-Alder Methodology in Organic Synthesis; Academic Press: New York, 1987. Tietze, L. F.; Kettschau, G. Stereoselective Heterocyclic Synthesis I; Metz, P., Ed.; Springer: Berlin, 1997; Vol. 189, pp 1-120. Ager, D. J.; East, M. B. Tetrahedron 1993, 49, 5683-5765.
3. For leading references of inverse-electron demand hetero-Diels- Alder reactions, see, for example: (a) Desimoni, G.; Tacconi, G. Chem. Rev. 1975, 75, 651-692. (b) Boger, D. L.; Weinreb, S. M. Hetero Diels- Alder Methodology in Organic Synthesis; Academic Press: New York, 1987. Tietze, L. F.; Kettschau, G. Stereoselective Heterocyclic Synthesis I; Metz, P., Ed.; Springer: Berlin, 1997; Vol. 189, pp 1-120. Ager, D. J.; East, M. B. Tetrahedron 1993, 49, 5683-5765.
4. For leading references of inverse-electron demand hetero-Diels- Alder reactions, see, for example: (a) Desimoni, G.; Tacconi, G. Chem. Rev. 1975, 75, 651-692. (b) Boger, D. L.; Weinreb, S. M. Hetero Diels- Alder Methodology in Organic Synthesis; Academic Press: New York, 1987. Tietze, L. F.; Kettschau, G. Stereoselective Heterocyclic Synthesis I; Metz, P., Ed.; Springer: Berlin, 1997; Vol. 189, pp 1-120. Ager, D. J.; East, M. B. Tetrahedron 1993, 49, 5683-5765.
5. For references of inverse hetero-Diels-Alder reactions in an achiral environment, see, for example: (a) Tietze, L. F.; Voss, E. Tetrahedron Lett. 1986, 27, 6181-6184. (b) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 3373-3377. (c) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 5793-5796. (d) Wada, E.; Kanemasa, S.; Tsuge, O. Chem. Lett. 1989, 675-678. (e) Tietze, L. F.; Hartfiel, U. Tetrahedron Lett. 1990, 31, 1697-1700. (f) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Chem. Lett. 1990, 2043-2046. (g) Tietze, L. F.; Schneider, C. Synlett, 1992, 755-756. (h) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Bull. Chem. Soc. Jpn. 1994, 67, 1912-1917.
6. For references of inverse hetero-Diels-Alder reactions in an achiral environment, see, for example: (a) Tietze, L. F.; Voss, E. Tetrahedron Lett. 1986, 27, 6181-6184. (b) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 3373-3377. (c) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 5793-5796. (d) Wada, E.; Kanemasa, S.; Tsuge, O. Chem. Lett. 1989, 675-678. (e) Tietze, L. F.; Hartfiel, U. Tetrahedron Lett. 1990, 31, 1697-1700. (f) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Chem. Lett. 1990, 2043-2046. (g) Tietze, L. F.; Schneider, C. Synlett, 1992, 755-756. (h) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Bull. Chem. Soc. Jpn. 1994, 67, 1912-1917.
7. For references of inverse hetero-Diels-Alder reactions in an achiral environment, see, for example: (a) Tietze, L. F.; Voss, E. Tetrahedron Lett. 1986, 27, 6181-6184. (b) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 3373-3377. (c) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 5793-5796. (d) Wada, E.; Kanemasa, S.; Tsuge, O. Chem. Lett. 1989, 675-678. (e) Tietze, L. F.; Hartfiel, U. Tetrahedron Lett. 1990, 31, 1697-1700. (f) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Chem. Lett. 1990, 2043-2046. (g) Tietze, L. F.; Schneider, C. Synlett, 1992, 755-756. (h) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Bull. Chem. Soc. Jpn. 1994, 67, 1912-1917.
8. For references of inverse hetero-Diels-Alder reactions in an achiral environment, see, for example: (a) Tietze, L. F.; Voss, E. Tetrahedron Lett. 1986, 27, 6181-6184. (b) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 3373-3377. (c) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 5793-5796. (d) Wada, E.; Kanemasa, S.; Tsuge, O. Chem. Lett. 1989, 675-678. (e) Tietze, L. F.; Hartfiel, U. Tetrahedron Lett. 1990, 31, 1697-1700. (f) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Chem. Lett. 1990, 2043-2046. (g) Tietze, L. F.; Schneider, C. Synlett, 1992, 755-756. (h) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Bull. Chem. Soc. Jpn. 1994, 67, 1912-1917.
9. For references of inverse hetero-Diels-Alder reactions in an achiral environment, see, for example: (a) Tietze, L. F.; Voss, E. Tetrahedron Lett. 1986, 27, 6181-6184. (b) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 3373-3377. (c) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 5793-5796. (d) Wada, E.; Kanemasa, S.; Tsuge, O. Chem. Lett. 1989, 675-678. (e) Tietze, L. F.; Hartfiel, U. Tetrahedron Lett. 1990, 31, 1697-1700. (f) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Chem. Lett. 1990, 2043-2046. (g) Tietze, L. F.; Schneider, C. Synlett, 1992, 755-756. (h) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Bull. Chem. Soc. Jpn. 1994, 67, 1912-1917.
10. For references of inverse hetero-Diels-Alder reactions in an achiral environment, see, for example: (a) Tietze, L. F.; Voss, E. Tetrahedron Lett. 1986, 27, 6181-6184. (b) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 3373-3377. (c) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 5793-5796. (d) Wada, E.; Kanemasa, S.; Tsuge, O. Chem. Lett. 1989, 675-678. (e) Tietze, L. F.; Hartfiel, U. Tetrahedron Lett. 1990, 31, 1697-1700. (f) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Chem. Lett. 1990, 2043-2046. (g) Tietze, L. F.; Schneider, C. Synlett, 1992, 755-756. (h) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Bull. Chem. Soc. Jpn. 1994, 67, 1912-1917.
11. For references of inverse hetero-Diels-Alder reactions in an achiral environment, see, for example: (a) Tietze, L. F.; Voss, E. Tetrahedron Lett. 1986, 27, 6181-6184. (b) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 3373-3377. (c) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 5793-5796. (d) Wada, E.; Kanemasa, S.; Tsuge, O. Chem. Lett. 1989, 675-678. (e) Tietze, L. F.; Hartfiel, U. Tetrahedron Lett. 1990, 31, 1697-1700. (f) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Chem. Lett. 1990, 2043-2046. (g) Tietze, L. F.; Schneider, C. Synlett, 1992, 755-756. (h) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Bull. Chem. Soc. Jpn. 1994, 67, 1912-1917.
12. For references of inverse hetero-Diels-Alder reactions in an achiral environment, see, for example: (a) Tietze, L. F.; Voss, E. Tetrahedron Lett. 1986, 27, 6181-6184. (b) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 3373-3377. (c) Boger, D. L.; Robarge, K. D. J. Org. Chem. 1988, 53, 5793-5796. (d) Wada, E.; Kanemasa, S.; Tsuge, O. Chem. Lett. 1989, 675-678. (e) Tietze, L. F.; Hartfiel, U. Tetrahedron Lett. 1990, 31, 1697-1700. (f) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Chem. Lett. 1990, 2043-2046. (g) Tietze, L. F.; Schneider, C. Synlett, 1992, 755-756. (h) Sera, A.; Ohara, M.; Yamada, H.; Egashira, E.; Ueda, N.; Setsune, J. Bull. Chem. Soc. Jpn. 1994, 67, 1912-1917.
13. For examples of diastereoselective hetero-Diels-Alder reaction of α,β-unsaturated carbonyl compounds with electron-rich alkenes, see, for example: (a) Schmidt, R. R.; Maier, M. Tetrahedron Lett. 1985, 26, 2065-2068. (b) Schmidt, R. R.; Haag-Zeino, B.; Hoch, M. Liebigs Ann. Chem. 1988, 885-889. (c) Dujardin, G.; Molato, S.; Brown, E. Tetrahedron: Asymmetry 1993, 4, 193-196. (d) Tietze, L. F.; Montenbruck, A.; Schneider, C. Synlett 1994, 509-510. (e) Tietze, L. F.; Schneider, C.; Grote, A. Chem. Eur. J. 1996, 2, 139-148. (f) Wada, E.; Pei, W.; Yasuoka, H.; Chin, U.; Kanemasa, S. Tetrahedron 1996, 52, 1205-1220. (g) Dujardin, G.; Rossignol, S.; Brown, E. Tetrahedron 1996, 52, 4007-4010. (h) Dujardin, G.; Rossignol, S.; Brown, E. Synthesis 1998, 763-770.
14. For examples of diastereoselective hetero-Diels-Alder reaction of α,β-unsaturated carbonyl compounds with electron-rich alkenes, see, for example: (a) Schmidt, R. R.; Maier, M. Tetrahedron Lett. 1985, 26, 2065-2068. (b) Schmidt, R. R.; Haag-Zeino, B.; Hoch, M. Liebigs Ann. Chem. 1988, 885-889. (c) Dujardin, G.; Molato, S.; Brown, E. Tetrahedron: Asymmetry 1993, 4, 193-196. (d) Tietze, L. F.; Montenbruck, A.; Schneider, C. Synlett 1994, 509-510. (e) Tietze, L. F.; Schneider, C.; Grote, A. Chem. Eur. J. 1996, 2, 139-148. (f) Wada, E.; Pei, W.; Yasuoka, H.; Chin, U.; Kanemasa, S. Tetrahedron 1996, 52, 1205-1220. (g) Dujardin, G.; Rossignol, S.; Brown, E. Tetrahedron 1996, 52, 4007-4010. (h) Dujardin, G.; Rossignol, S.; Brown, E. Synthesis 1998, 763-770.
15. For examples of diastereoselective hetero-Diels-Alder reaction of α,β-unsaturated carbonyl compounds with electron-rich alkenes, see, for example: (a) Schmidt, R. R.; Maier, M. Tetrahedron Lett. 1985, 26, 2065-2068. (b) Schmidt, R. R.; Haag-Zeino, B.; Hoch, M. Liebigs Ann. Chem. 1988, 885-889. (c) Dujardin, G.; Molato, S.; Brown, E. Tetrahedron: Asymmetry 1993, 4, 193-196. (d) Tietze, L. F.; Montenbruck, A.; Schneider, C. Synlett 1994, 509-510. (e) Tietze, L. F.; Schneider, C.; Grote, A. Chem. Eur. J. 1996, 2, 139-148. (f) Wada, E.; Pei, W.; Yasuoka, H.; Chin, U.; Kanemasa, S. Tetrahedron 1996, 52, 1205-1220. (g) Dujardin, G.; Rossignol, S.; Brown, E. Tetrahedron 1996, 52, 4007-4010. (h) Dujardin, G.; Rossignol, S.; Brown, E. Synthesis 1998, 763-770.
16. For examples of diastereoselective hetero-Diels-Alder reaction of α,β-unsaturated carbonyl compounds with electron-rich alkenes, see, for example: (a) Schmidt, R. R.; Maier, M. Tetrahedron Lett. 1985, 26, 2065-2068. (b) Schmidt, R. R.; Haag-Zeino, B.; Hoch, M. Liebigs Ann. Chem. 1988, 885-889. (c) Dujardin, G.; Molato, S.; Brown, E. Tetrahedron: Asymmetry 1993, 4, 193-196. (d) Tietze, L. F.; Montenbruck, A.; Schneider, C. Synlett 1994, 509-510. (e) Tietze, L. F.; Schneider, C.; Grote, A. Chem. Eur. J. 1996, 2, 139-148. (f) Wada, E.; Pei, W.; Yasuoka, H.; Chin, U.; Kanemasa, S. Tetrahedron 1996, 52, 1205-1220. (g) Dujardin, G.; Rossignol, S.; Brown, E. Tetrahedron 1996, 52, 4007-4010. (h) Dujardin, G.; Rossignol, S.; Brown, E. Synthesis 1998, 763-770.
17. For examples of diastereoselective hetero-Diels-Alder reaction of α,β-unsaturated carbonyl compounds with electron-rich alkenes, see, for example: (a) Schmidt, R. R.; Maier, M. Tetrahedron Lett. 1985, 26, 2065-2068. (b) Schmidt, R. R.; Haag-Zeino, B.; Hoch, M. Liebigs Ann. Chem. 1988, 885-889. (c) Dujardin, G.; Molato, S.; Brown, E. Tetrahedron: Asymmetry 1993, 4, 193-196. (d) Tietze, L. F.; Montenbruck, A.; Schneider, C. Synlett 1994, 509-510. (e) Tietze, L. F.; Schneider, C.; Grote, A. Chem. Eur. J. 1996, 2, 139-148. (f) Wada, E.; Pei, W.; Yasuoka, H.; Chin, U.; Kanemasa, S. Tetrahedron 1996, 52, 1205-1220. (g) Dujardin, G.; Rossignol, S.; Brown, E. Tetrahedron 1996, 52, 4007-4010. (h) Dujardin, G.; Rossignol, S.; Brown, E. Synthesis 1998, 763-770.
18. For examples of diastereoselective hetero-Diels-Alder reaction of α,β-unsaturated carbonyl compounds with electron-rich alkenes, see, for example: (a) Schmidt, R. R.; Maier, M. Tetrahedron Lett. 1985, 26, 2065-2068. (b) Schmidt, R. R.; Haag-Zeino, B.; Hoch, M. Liebigs Ann. Chem. 1988, 885-889. (c) Dujardin, G.; Molato, S.; Brown, E. Tetrahedron: Asymmetry 1993, 4, 193-196. (d) Tietze, L. F.; Montenbruck, A.; Schneider, C. Synlett 1994, 509-510. (e) Tietze, L. F.; Schneider, C.; Grote, A. Chem. Eur. J. 1996, 2, 139-148. (f) Wada, E.; Pei, W.; Yasuoka, H.; Chin, U.; Kanemasa, S. Tetrahedron 1996, 52, 1205-1220. (g) Dujardin, G.; Rossignol, S.; Brown, E. Tetrahedron 1996, 52, 4007-4010. (h) Dujardin, G.; Rossignol, S.; Brown, E. Synthesis 1998, 763-770.
19. For examples of diastereoselective hetero-Diels-Alder reaction of α,β-unsaturated carbonyl compounds with electron-rich alkenes, see, for example: (a) Schmidt, R. R.; Maier, M. Tetrahedron Lett. 1985, 26, 2065-2068. (b) Schmidt, R. R.; Haag-Zeino, B.; Hoch, M. Liebigs Ann. Chem. 1988, 885-889. (c) Dujardin, G.; Molato, S.; Brown, E. Tetrahedron: Asymmetry 1993, 4, 193-196. (d) Tietze, L. F.; Montenbruck, A.; Schneider, C. Synlett 1994, 509-510. (e) Tietze, L. F.; Schneider, C.; Grote, A. Chem. Eur. J. 1996, 2, 139-148. (f) Wada, E.; Pei, W.; Yasuoka, H.; Chin, U.; Kanemasa, S. Tetrahedron 1996, 52, 1205-1220. (g) Dujardin, G.; Rossignol, S.; Brown, E. Tetrahedron 1996, 52, 4007-4010. (h) Dujardin, G.; Rossignol, S.; Brown, E. Synthesis 1998, 763-770.
20. For examples of diastereoselective hetero-Diels-Alder reaction of α,β-unsaturated carbonyl compounds with electron-rich alkenes, see, for example: (a) Schmidt, R. R.; Maier, M. Tetrahedron Lett. 1985, 26, 2065-2068. (b) Schmidt, R. R.; Haag-Zeino, B.; Hoch, M. Liebigs Ann. Chem. 1988, 885-889. (c) Dujardin, G.; Molato, S.; Brown, E. Tetrahedron: Asymmetry 1993, 4, 193-196. (d) Tietze, L. F.; Montenbruck, A.; Schneider, C. Synlett 1994, 509-510. (e) Tietze, L. F.; Schneider, C.; Grote, A. Chem. Eur. J. 1996, 2, 139-148. (f) Wada, E.; Pei, W.; Yasuoka, H.; Chin, U.; Kanemasa, S. Tetrahedron 1996, 52, 1205-1220. (g) Dujardin, G.; Rossignol, S.; Brown, E. Tetrahedron 1996, 52, 4007-4010. (h) Dujardin, G.; Rossignol, S.; Brown, E. Synthesis 1998, 763-770.
21. Wada, E.; Yasuoka, H.; Kanemasa, S. Chem. Lett. 1994, 1637-1640.
22. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
23. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
24. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
25. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
26. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
27. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
28. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310-312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
29. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
30. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
31. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
32. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563-1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
33. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
34. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
35. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
36. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
37. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
38. The use of chiral Lewis acids in HDA reactions, see, for example: (a) Graven, A.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1996, 2373-2374. (b) Yao, S.; Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 1. 1997, 2345-2349. (c) Johannsen, M.; Jørgensen, K. A.; Zheng, X. F.; Hu, Q. S.; Pu, L. J. Org. Chem. 1999, 64, 299-301. (d) Dossetter, A. G.; Jamison, T. F.; Jacobsen, E. N. Angew. Chem. 1999, 111, 2459-2553; Angew. Chem., Int. Ed. 1999, 38, 2398-2400. (e) Desimoni, G.; Faita, G.; Righetti, P.; Sardone, N. Tetrahedron 1996, 52, 12019-12030. (f) Maruoka, K.; Itoh, T.; Shirasaka, T.; Yamamoto, H. J. Am. Chem. Soc. 1988, 110, 310- 312. (g) Gao, Q.; Maruyama, T.; Mouri, M.; Yamamoto, H. J. Org. Chem. 1992, 57, 1951-1952. (h) Gao, Q.; Ishihara, K.; Maruyama, T.; Mouri, M.; Yamamoto, H. Tetrahedron 1994, 50, 979-988. (i) Schauss, S.; Brånalt, J.; Jacobsen, E. N. J. Org. Chem. 1998, 63, 403-405. (j) Motoyama, Y.; Mikami, K. J. Chem. Soc., Chem. Commun. 1994, 1563- 1564. (k) Bednarski, M.; Danishefsky, S. J. Am. Chem. Soc. 1986, 108, 7060-7067. (1) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron Lett. 1997, 38, 2427-2430. (m) Li, L.-S.; Wu, Y.; Hu, Y.-J. Xia, L.-J.; Wu, Y.-L. Tetrahedron: Asymemtry 1998, 9, 2271-2277. (n) Corey, E. J.; Cywin, C. L.; Roper, T. D. Tetrahedron Lett. 1992, 33, 6907-6910. (o) Keck, G. E.; Li, X.-Y.; Krishnamurthy, D. J. Org. Chem. 1995, 60, 5998-5999. (p) Togni, A. Organometallics 1990, 9, 3106-3113.
39. Hetero-Diels-Alder reactions of aldehydes/ketones with dienes catalyzed by chiral bisoxazoline-copper(II): (a) Johannsen, M.; Jørgensen, K. A. J. Org. Chem. 1995, 60, 5757-5762. (b) Johannsen, M.; Jørgensen, K. A. Tetrahedron 1996, 52, 7321-7328. (c) Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 2 1997, 1183-1185. (d) Johannsen, M.; Yao, S.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1997, 2169-2170. (e) Yao, S.; Johannsen, M.; Hazell, R. G.; Jørgensen, K. A. J. Org. Chem. 1998, 63, 118-121. (f) Johannsen, M.; Yao, S.; Graven, A.; Jørgensen, K A. Pure Appl. Chem. 1998, 70, 1117- 1122. (g) Yao, S.; Johannsen, M.; Audrain, H.; Hazell, R. G.; Jørgensen, K. A. J. Am. Chem. Soc. 1998, 120, 8599-8605. (h) Ghosh, A. K.; Mathivanan, P.; Cappiello, J.; Krishnan, K. Tetrahedron: Asymmetry 1996, 7, 2165-2168.
40. Hetero-Diels-Alder reactions of aldehydes/ketones with dienes catalyzed by chiral bisoxazoline-copper(II): (a) Johannsen, M.; Jørgensen, K. A. J. Org. Chem. 1995, 60, 5757-5762. (b) Johannsen, M.; Jørgensen, K. A. Tetrahedron 1996, 52, 7321-7328. (c) Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 2 1997, 1183-1185. (d) Johannsen, M.; Yao, S.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1997, 2169-2170. (e) Yao, S.; Johannsen, M.; Hazell, R. G.; Jørgensen, K. A. J. Org. Chem. 1998, 63, 118-121. (f) Johannsen, M.; Yao, S.; Graven, A.; Jørgensen, K A. Pure Appl. Chem. 1998, 70, 1117- 1122. (g) Yao, S.; Johannsen, M.; Audrain, H.; Hazell, R. G.; Jørgensen, K. A. J. Am. Chem. Soc. 1998, 120, 8599-8605. (h) Ghosh, A. K.; Mathivanan, P.; Cappiello, J.; Krishnan, K. Tetrahedron: Asymmetry 1996, 7, 2165-2168.
41. Hetero-Diels-Alder reactions of aldehydes/ketones with dienes catalyzed by chiral bisoxazoline-copper(II): (a) Johannsen, M.; Jørgensen, K. A. J. Org. Chem. 1995, 60, 5757-5762. (b) Johannsen, M.; Jørgensen, K. A. Tetrahedron 1996, 52, 7321-7328. (c) Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 2 1997, 1183-1185. (d) Johannsen, M.; Yao, S.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1997, 2169-2170. (e) Yao, S.; Johannsen, M.; Hazell, R. G.; Jørgensen, K. A. J. Org. Chem. 1998, 63, 118-121. (f) Johannsen, M.; Yao, S.; Graven, A.; Jørgensen, K A. Pure Appl. Chem. 1998, 70, 1117- 1122. (g) Yao, S.; Johannsen, M.; Audrain, H.; Hazell, R. G.; Jørgensen, K. A. J. Am. Chem. Soc. 1998, 120, 8599-8605. (h) Ghosh, A. K.; Mathivanan, P.; Cappiello, J.; Krishnan, K. Tetrahedron: Asymmetry 1996, 7, 2165-2168.
42. Hetero-Diels-Alder reactions of aldehydes/ketones with dienes catalyzed by chiral bisoxazoline-copper(II): (a) Johannsen, M.; Jørgensen, K. A. J. Org. Chem. 1995, 60, 5757-5762. (b) Johannsen, M.; Jørgensen, K. A. Tetrahedron 1996, 52, 7321-7328. (c) Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 2 1997, 1183-1185. (d) Johannsen, M.; Yao, S.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1997, 2169-2170. (e) Yao, S.; Johannsen, M.; Hazell, R. G.; Jørgensen, K. A. J. Org. Chem. 1998, 63, 118-121. (f) Johannsen, M.; Yao, S.; Graven, A.; Jørgensen, K A. Pure Appl. Chem. 1998, 70, 1117- 1122. (g) Yao, S.; Johannsen, M.; Audrain, H.; Hazell, R. G.; Jørgensen, K. A. J. Am. Chem. Soc. 1998, 120, 8599-8605. (h) Ghosh, A. K.; Mathivanan, P.; Cappiello, J.; Krishnan, K. Tetrahedron: Asymmetry 1996, 7, 2165-2168.
43. Hetero-Diels-Alder reactions of aldehydes/ketones with dienes catalyzed by chiral bisoxazoline-copper(II): (a) Johannsen, M.; Jørgensen, K. A. J. Org. Chem. 1995, 60, 5757-5762. (b) Johannsen, M.; Jørgensen, K. A. Tetrahedron 1996, 52, 7321-7328. (c) Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 2 1997, 1183-1185. (d) Johannsen, M.; Yao, S.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1997, 2169-2170. (e) Yao, S.; Johannsen, M.; Hazell, R. G.; Jørgensen, K. A. J. Org. Chem. 1998, 63, 118-121. (f) Johannsen, M.; Yao, S.; Graven, A.; Jørgensen, K A. Pure Appl. Chem. 1998, 70, 1117- 1122. (g) Yao, S.; Johannsen, M.; Audrain, H.; Hazell, R. G.; Jørgensen, K. A. J. Am. Chem. Soc. 1998, 120, 8599-8605. (h) Ghosh, A. K.; Mathivanan, P.; Cappiello, J.; Krishnan, K. Tetrahedron: Asymmetry 1996, 7, 2165-2168.
44. Hetero-Diels-Alder reactions of aldehydes/ketones with dienes catalyzed by chiral bisoxazoline-copper(II): (a) Johannsen, M.; Jørgensen, K. A. J. Org. Chem. 1995, 60, 5757-5762. (b) Johannsen, M.; Jørgensen, K. A. Tetrahedron 1996, 52, 7321-7328. (c) Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 2 1997, 1183-1185. (d) Johannsen, M.; Yao, S.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1997, 2169-2170. (e) Yao, S.; Johannsen, M.; Hazell, R. G.; Jørgensen, K. A. J. Org. Chem. 1998, 63, 118-121. (f) Johannsen, M.; Yao, S.; Graven, A.; Jørgensen, K A. Pure Appl. Chem. 1998, 70, 1117-1122. (g) Yao, S.; Johannsen, M.; Audrain, H.; Hazell, R. G.; Jørgensen, K. A. J. Am. Chem. Soc. 1998, 120, 8599-8605. (h) Ghosh, A. K.; Mathivanan, P.; Cappiello, J.; Krishnan, K. Tetrahedron: Asymmetry 1996, 7, 2165-2168.
45. Hetero-Diels-Alder reactions of aldehydes/ketones with dienes catalyzed by chiral bisoxazoline-copper(II): (a) Johannsen, M.; Jørgensen, K. A. J. Org. Chem. 1995, 60, 5757-5762. (b) Johannsen, M.; Jørgensen, K. A. Tetrahedron 1996, 52, 7321-7328. (c) Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 2 1997, 1183-1185. (d) Johannsen, M.; Yao, S.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1997, 2169-2170. (e) Yao, S.; Johannsen, M.; Hazell, R. G.; Jørgensen, K. A. J. Org. Chem. 1998, 63, 118-121. (f) Johannsen, M.; Yao, S.; Graven, A.; Jørgensen, K A. Pure Appl. Chem. 1998, 70, 1117- 1122. (g) Yao, S.; Johannsen, M.; Audrain, H.; Hazell, R. G.; Jørgensen, K. A. J. Am. Chem. Soc. 1998, 120, 8599-8605. (h) Ghosh, A. K.; Mathivanan, P.; Cappiello, J.; Krishnan, K. Tetrahedron: Asymmetry 1996, 7, 2165-2168.
46. Hetero-Diels-Alder reactions of aldehydes/ketones with dienes catalyzed by chiral bisoxazoline-copper(II): (a) Johannsen, M.; Jørgensen, K. A. J. Org. Chem. 1995, 60, 5757-5762. (b) Johannsen, M.; Jørgensen, K. A. Tetrahedron 1996, 52, 7321-7328. (c) Johannsen, M.; Jørgensen, K. A. J. Chem. Soc., Perkin Trans. 2 1997, 1183-1185. (d) Johannsen, M.; Yao, S.; Jørgensen, K. A. J. Chem. Soc., Chem. Commun. 1997, 2169-2170. (e) Yao, S.; Johannsen, M.; Hazell, R. G.; Jørgensen, K. A. J. Org. Chem. 1998, 63, 118-121. (f) Johannsen, M.; Yao, S.; Graven, A.; Jørgensen, K A. Pure Appl. Chem. 1998, 70, 1117- 1122. (g) Yao, S.; Johannsen, M.; Audrain, H.; Hazell, R. G.; Jørgensen, K. A. J. Am. Chem. Soc. 1998, 120, 8599-8605. (h) Ghosh, A. K.; Mathivanan, P.; Cappiello, J.; Krishnan, K. Tetrahedron: Asymmetry 1996, 7, 2165-2168.
47. For chiral bisoxazoline copper(II) complex used to catalyze addition to α-dicarbonyls, see, for example: (a) Jørgensen, K. A.; Johannsen, M.; Yao, S.; Audrain, H.; Thorhauge, J. Acc. Chem. Res. 1999, 32, 605-613. (b) Evans, D. A.; Johnson, J. S. Acc. Chem. Res. 2000, 33, in press.
48. For chiral bisoxazoline copper(II) complex used to catalyze addition to α-dicarbonyls, see, for example: (a) Jørgensen, K. A.; Johannsen, M.; Yao, S.; Audrain, H.; Thorhauge, J. Acc. Chem. Res. 1999, 32, 605-613. (b) Evans, D. A.; Johnson, J. S. Acc. Chem. Res. 2000, 33, in press.
49. For pioneering work using bisoxazoline ligands, see: (a) Fritschi, H.; Leutenegger, U.; Siegmann, K.; Pfaltz, A.; Keller, W.; Kratky, C. Helv. Chim. Acta 1988, 71, 1541-1552. (b) Evans, D. A.; Woerpel, K. A.; Hinman, M. M.; Faul, M. M. J. Am. Chem. Soc. 1991, 113, 726- 728.
50. For pioneering work using bisoxazoline ligands, see: (a) Fritschi, H.; Leutenegger, U.; Siegmann, K.; Pfaltz, A.; Keller, W.; Kratky, C. Helv. Chim. Acta 1988, 71, 1541-1552. (b) Evans, D. A.; Woerpel, K. A.; Hinman, M. M.; Faul, M. M. J. Am. Chem. Soc. 1991, 113, 726-728.
51. Woodward, R. B.; Hoffmann, R. The Conservation of Orbital Symmetry; Verlag Chemie: Weinhein, 1970.
52. (a) Evans, D. A.; Johnson, J. S. J. Am. Chem. Soc. 1998, 120, 4895-4896.
53. (b) Thorhauge, J.; Johannsen, M.; Jørgensen, K. A. Angew. Chem. 1998, 110, 2543-2546; Angew. Chem., Int. Ed. 1998, 37, 2404- 2406.
54. (b) Thorhauge, J.; Johannsen, M.; Jørgensen, K. A. Angew. Chem. 1998, 110, 2543-2546; Angew. Chem., Int. Ed. 1998, 37, 2404-2406.
55. (c) Evans, D. A.; Olhava, E. J.; Johnson, J. S.; Janey, J. M. Angew. Chem. 1998, 110, 3554-3557; Angew. Chem., Int. Ed. 1998, 37, 3372- 3375.
56. (c) Evans, D. A.; Olhava, E. J.; Johnson, J. S.; Janey, J. M. Angew. Chem. 1998, 110, 3554-3557; Angew. Chem., Int. Ed. 1998, 37, 3372-3375.
57. (d) Evans, D. A.; Johnson, J. S.; Olhava, E. J. J. Am. Chem. Soc. 2000, 122, 1635-1649.
58. Perron, F.; Albizati, K. F. Chem. Rev. 1989, 89, 1617-1661; see also: Bartolozzi, A.; Capozzi, G.; Falciani, C.; Menichetti, S.; Naitvi, C.; Bacialli, A. P. J. Org. Chem. 1999, 64, 6490-6494.
59. Perron, F.; Albizati, K. F. Chem. Rev. 1989, 89, 1617-1661; see also: Bartolozzi, A.; Capozzi, G.; Falciani, C.; Menichetti, S.; Naitvi, C.; Bacialli, A. P. J. Org. Chem. 1999, 64, 6490-6494.
60. For spirosugars made using HDA, see: Ireland, R. E.; Häbich, D. Chem. Ber. 1981, 114, 1418-1427.
61. For other methodes to synthesize spirosugars, see, for example: (a) Boivin, T. L. B. Tetrahedron 1987, 43, 3309-3362. (b) Martin, A.; Salazar, J. A.; Suarez, E. J. Org. Chem. 1996, 61, 3999- 4006. (c) Van Hooft, P. A. V.; Leeuwenburgh, M. A.; Overkleeft, H. S.; Van der Marel, G. A.; Van Boeckel, C. A. A.; Van Boom, J. H. Tetrahedron Lett. 1998, 39, 6061-6064.
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