Ring closing alkyne metathesis. Comparative investigation of two different catalyst systems and application to the stereoselective synthesis of olfactory lactones, azamacrolides, and the macrocyclic perimeter of the marine alkaloid nakadomarin A

Journal of the American Chemical Society

Volumn 121, Issue 48, 1999, Pages 11108-11113

  Fürstner, Alois ^a   Guth, Oliver ^a   Rumbo, Antonio ^a   Seidel, Günter ^a  

^a MAX PLANCK INSTITUT FÜR KOHLENFORSCHUNG   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; CATALYST; CHEMICAL INTERACTION; CHEMICAL STRUCTURE; COMPLEX FORMATION; CYCLIZATION; REACTION ANALYSIS; STEREOCHEMISTRY; SYNTHESIS;

EID: 0033537059     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja992074k     Document Type: Article

References (95)

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2. For leading references see: (a) Nguyen, S. T.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1993, 115, 9858. (b) Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996, 118, 100. (c) Schrock, R. R.; Murdzek, J. S.; Bazan, G. C.; Robbins, J.; DiMare, M.; O'Regan, M. J. Am. Chem. Soc. 1990, 112, 3875.
3. For leading references see: (a) Nguyen, S. T.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1993, 115, 9858. (b) Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996, 118, 100. (c) Schrock, R. R.; Murdzek, J. S.; Bazan, G. C.; Robbins, J.; DiMare, M.; O'Regan, M. J. Am. Chem. Soc. 1990, 112, 3875.
4. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
5. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
6. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
7. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
8. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
9. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
10. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
11. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
12. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
13. For recent innovations see: (a) Scholl, M.; Trnka, T. M.; Morgan, J. P.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247. (b) Huang, J.; Stevens, E. D.; Nolan, S. P.; Pedersen, J. L. J. Am. Chem. Soc. 1999, 121, 2674. (c) Ackermann, L.; Fürstner, A ; Weskamp, T.; Kohl, F. J.; Herrmann, W. A. Tetrahedron Lett. 1999, 40, 4787. (d) Hansen, S. M.; Rominger, F.; Metz, M.; Hofmann, P. Chem. Eur J. 1999, 5, 557. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791. (f) Fürstner, A.; Hill, A. F.; Liebl, M.; Winton-Ely, J. D E. T. Chem. Commun. 1999, 601. (g) Demonceau, A.; Stumpf, A W.; Saive, E.; Noels, A. F. Macromolecules 1997, 30, 3127. (h) Hafner, A.; Muhlebach, A.; van der Schaaf, P. A Angew. Chem., Int. Ed. Engl. 1997, 36, 2121. (i) Fürstner, A.; Ackermann, L. Chem. Commun. 1999, 95 (j) Fürstner, A.; Picquet, M ; Bruneau C.; Dixneuf, P. H. Chem. Commun 1998, 1315.
14. For recent reviews on RCM see the following for leading references: (a) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413. (b) Furstner, A. Top. Catal. 1997, 4, 285. (c) Schuster, M.; Blechert, S. Angew. Chem., Int. Ed Engl. 1997, 36, 2036. (d) Fürstner, A. Top. Organomet. Chem 1998, 1, 37. (e) Ivin, K. J.; Mol, J. C. Olefin Metathesis and Methathesis Polymerization, 2nd ed.; Academic Press: New York, 1997.
15. For recent reviews on RCM see the following for leading references: (a) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413. (b) Furstner, A. Top. Catal. 1997, 4, 285. (c) Schuster, M.; Blechert, S. Angew. Chem., Int. Ed Engl. 1997, 36, 2036. (d) Fürstner, A. Top. Organomet. Chem 1998, 1, 37. (e) Ivin, K. J.; Mol, J. C. Olefin Metathesis and Methathesis Polymerization, 2nd ed.; Academic Press: New York, 1997.
16. For recent reviews on RCM see the following for leading references: (a) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413. (b) Furstner, A. Top. Catal. 1997, 4, 285. (c) Schuster, M.; Blechert, S. Angew. Chem., Int. Ed Engl. 1997, 36, 2036. (d) Fürstner, A. Top. Organomet. Chem 1998, 1, 37. (e) Ivin, K. J.; Mol, J. C. Olefin Metathesis and Methathesis Polymerization, 2nd ed.; Academic Press: New York, 1997.
17. For recent reviews on RCM see the following for leading references: (a) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413. (b) Furstner, A. Top. Catal. 1997, 4, 285. (c) Schuster, M.; Blechert, S. Angew. Chem., Int. Ed Engl. 1997, 36, 2036. (d) Fürstner, A. Top. Organomet. Chem 1998, 1, 37. (e) Ivin, K. J.; Mol, J. C. Olefin Metathesis and Methathesis Polymerization, 2nd ed.; Academic Press: New York, 1997.
18. For recent reviews on RCM see the following for leading references: (a) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413. (b) Furstner, A. Top. Catal. 1997, 4, 285. (c) Schuster, M.; Blechert, S. Angew. Chem., Int. Ed Engl. 1997, 36, 2036. (d) Fürstner, A. Top. Organomet. Chem 1998, 1, 37. (e) Ivin, K. J.; Mol, J. C. Olefin Metathesis and Methathesis Polymerization, 2nd ed.; Academic Press: New York, 1997.
19. For recent reviews on macrocycle syntheses via RCM see: (a) Nicolaou, K. C ; King, N. P.; He, Y. Top. Organomet. Chem. 1998, 1, 73. (b) Hoveyda, A. H. Top. Organomet. Chem. 1998, 1, 105 and literature cited therein.
20. For recent reviews on macrocycle syntheses via RCM see: (a) Nicolaou, K. C ; King, N. P.; He, Y. Top. Organomet. Chem. 1998, 1, 73. (b) Hoveyda, A. H. Top. Organomet. Chem. 1998, 1, 105 and literature cited therein.
21. For RCM-based macrocycle syntheses from our laboratory see: (a) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 3942. (b) Fürstner, A.; Muller, T. J. Am. Chem. Soc. 1999, 121, 7814. (c) Fürstner, A.; Langemann, K. J. Am. Chem. Soc. 1997, 119, 9130. (d) Fürstner, A.; Kindler, N. Tetrahedron Lett. 1996, 37, 7005. (e) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 8746. (f) Fürstner, A.; Müller, T. Synlett 1997, 1010. (g) Fürstner, A.; Gastner, T.; Weintritt, H. J. Org. Chem. 1999, 64, 2361. (h) Fürstner, A.; Seidel, G.; Kindler, N. Tetrahedron 1999, 55, 8215.
22. For RCM-based macrocycle syntheses from our laboratory see: (a) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 3942. (b) Fürstner, A.; Muller, T. J. Am. Chem. Soc. 1999, 121, 7814. (c) Fürstner, A.; Langemann, K. J. Am. Chem. Soc. 1997, 119, 9130. (d) Fürstner, A.; Kindler, N. Tetrahedron Lett. 1996, 37, 7005. (e) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 8746. (f) Fürstner, A.; Müller, T. Synlett 1997, 1010. (g) Fürstner, A.; Gastner, T.; Weintritt, H. J. Org. Chem. 1999, 64, 2361. (h) Fürstner, A.; Seidel, G.; Kindler, N. Tetrahedron 1999, 55, 8215.
23. For RCM-based macrocycle syntheses from our laboratory see: (a) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 3942. (b) Fürstner, A.; Muller, T. J. Am. Chem. Soc. 1999, 121, 7814. (c) Fürstner, A.; Langemann, K. J. Am. Chem. Soc. 1997, 119, 9130. (d) Fürstner, A.; Kindler, N. Tetrahedron Lett. 1996, 37, 7005. (e) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 8746. (f) Fürstner, A.; Müller, T. Synlett 1997, 1010. (g) Fürstner, A.; Gastner, T.; Weintritt, H. J. Org. Chem. 1999, 64, 2361. (h) Fürstner, A.; Seidel, G.; Kindler, N. Tetrahedron 1999, 55, 8215.
24. For RCM-based macrocycle syntheses from our laboratory see: (a) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 3942. (b) Fürstner, A.; Muller, T. J. Am. Chem. Soc. 1999, 121, 7814. (c) Fürstner, A.; Langemann, K. J. Am. Chem. Soc. 1997, 119, 9130. (d) Fürstner, A.; Kindler, N. Tetrahedron Lett. 1996, 37, 7005. (e) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 8746. (f) Fürstner, A.; Müller, T. Synlett 1997, 1010. (g) Fürstner, A.; Gastner, T.; Weintritt, H. J. Org. Chem. 1999, 64, 2361. (h) Fürstner, A.; Seidel, G.; Kindler, N. Tetrahedron 1999, 55, 8215.
25. For RCM-based macrocycle syntheses from our laboratory see: (a) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 3942. (b) Fürstner, A.; Muller, T. J. Am. Chem. Soc. 1999, 121, 7814. (c) Fürstner, A.; Langemann, K. J. Am. Chem. Soc. 1997, 119, 9130. (d) Fürstner, A.; Kindler, N. Tetrahedron Lett. 1996, 37, 7005. (e) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 8746. (f) Fürstner, A.; Müller, T. Synlett 1997, 1010. (g) Fürstner, A.; Gastner, T.; Weintritt, H. J. Org. Chem. 1999, 64, 2361. (h) Fürstner, A.; Seidel, G.; Kindler, N. Tetrahedron 1999, 55, 8215.
26. For RCM-based macrocycle syntheses from our laboratory see: (a) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 3942. (b) Fürstner, A.; Muller, T. J. Am. Chem. Soc. 1999, 121, 7814. (c) Fürstner, A.; Langemann, K. J. Am. Chem. Soc. 1997, 119, 9130. (d) Fürstner, A.; Kindler, N. Tetrahedron Lett. 1996, 37, 7005. (e) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 8746. (f) Fürstner, A.; Müller, T. Synlett 1997, 1010. (g) Fürstner, A.; Gastner, T.; Weintritt, H. J. Org. Chem. 1999, 64, 2361. (h) Fürstner, A.; Seidel, G.; Kindler, N. Tetrahedron 1999, 55, 8215.
27. For RCM-based macrocycle syntheses from our laboratory see: (a) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 3942. (b) Fürstner, A.; Muller, T. J. Am. Chem. Soc. 1999, 121, 7814. (c) Fürstner, A.; Langemann, K. J. Am. Chem. Soc. 1997, 119, 9130. (d) Fürstner, A.; Kindler, N. Tetrahedron Lett. 1996, 37, 7005. (e) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 8746. (f) Fürstner, A.; Müller, T. Synlett 1997, 1010. (g) Fürstner, A.; Gastner, T.; Weintritt, H. J. Org. Chem. 1999, 64, 2361. (h) Fürstner, A.; Seidel, G.; Kindler, N. Tetrahedron 1999, 55, 8215.
28. For RCM-based macrocycle syntheses from our laboratory see: (a) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 3942. (b) Fürstner, A.; Muller, T. J. Am. Chem. Soc. 1999, 121, 7814. (c) Fürstner, A.; Langemann, K. J. Am. Chem. Soc. 1997, 119, 9130. (d) Fürstner, A.; Kindler, N. Tetrahedron Lett. 1996, 37, 7005. (e) Fürstner, A.; Langemann, K. J. Org. Chem. 1996, 61, 8746. (f) Fürstner, A.; Müller, T. Synlett 1997, 1010. (g) Fürstner, A.; Gastner, T.; Weintritt, H. J. Org. Chem. 1999, 64, 2361. (h) Fürstner, A.; Seidel, G.; Kindler, N. Tetrahedron 1999, 55, 8215.
29. (a) Bertinato, P., Sorensen, E. J.; Meng, D.; Danishefsky, S. J. J. Org. Chem. 1996, 61, 8000.
30. (b) Meng, D.; Bertinato, P.; Balog, A.; Su, D.-S.; Kamenecka, T.; Sorensen, E. J.; Danishefsky, S. J. J. Am. Chem. Soc. 1997, 119, 10073.
31. (c) Nicolaou, K. C.; He, Y.; Vourloumis, D.; Vallberg, H.; Roschangar, F.; Sarabia, F.; Ninkovic, S.; Yang, Z.; Trujillo, J. I J. Am Chem. Soc. 1997, 119, 7960.
32. (d) Yang, Z.; He, Y.; Vourloumis, D.; Vallberg, H.; Nicolaou, K. C. Angew. Chem., Int. Ed. Engl. 1997, 36, 166.
33. (e) Schinzer, D.; Limberg, A.; Bauer, A.; Böhm, O. M.; Cordes, M. Angew. Chem., Int. Ed. Engl. 1997, 36, 523.
34. A mechanism for alkyne metathesis via alkylidyne- and metallacyclobutadiene complexes has been proposed early on by Katz et al., cf.: Katz, T. J.; McGinnis, J. J. Am. Chem. Soc. 1975, 97, 1592. This hypothesis has been verified by the first alkyne metathesis reactions involving defined metal alkylidyne catalysts and by the isolation of metallacyclobutadiene intermediates, cf ref 9.
35. For a short review see: Bunz, U. H. F.; Kloppenburg, L. Angew. Chem. 1999, 111, 503; Angew. Chem., Int. Ed. Engl. 1999, 38, 478.
36. For a short review see: Bunz, U. H. F.; Kloppenburg, L. Angew. Chem. 1999, 111, 503; Angew. Chem., Int. Ed. Engl. 1999, 38, 478.
37. For the first alkyne metathesis reaction using a defined metal alkylidyne catalyst see: Wengrovius, J. H.; Sancho, J.; Schrock, R. R. J. Am. Chem Soc. 1981, 103, 3932.
38. Preparation and applications of tungsten alkylidyne complexes: (a) Schrock, R. R.; Clark, D. N.; Sancho, J.; Wengrovius, J. H.; Rocklage, S. M.; Pedersen, S. F. Organometallics 1982, 1, 1645. (b) Freudenberger, J. H.; Schrock, R. R.; Churchill, M. R.; Rheingold, A. L.; Ziller, J. W. Organometallics 1984, 3, 1563. (c) Listemann, M. L.; Schrock, R. R. Organometallics 1985, 4. 74. (d) Schrock, R. R. Polyhedron 1995, 14, 3177.
39. Preparation and applications of tungsten alkylidyne complexes: (a) Schrock, R. R.; Clark, D. N.; Sancho, J.; Wengrovius, J. H.; Rocklage, S. M.; Pedersen, S. F. Organometallics 1982, 1, 1645. (b) Freudenberger, J. H.; Schrock, R. R.; Churchill, M. R.; Rheingold, A. L.; Ziller, J. W. Organometallics 1984, 3, 1563. (c) Listemann, M. L.; Schrock, R. R. Organometallics 1985, 4. 74. (d) Schrock, R. R. Polyhedron 1995, 14, 3177.
40. Preparation and applications of tungsten alkylidyne complexes: (a) Schrock, R. R.; Clark, D. N.; Sancho, J.; Wengrovius, J. H.; Rocklage, S. M.; Pedersen, S. F. Organometallics 1982, 1, 1645. (b) Freudenberger, J. H.; Schrock, R. R.; Churchill, M. R.; Rheingold, A. L.; Ziller, J. W. Organometallics 1984, 3, 1563. (c) Listemann, M. L.; Schrock, R. R. Organometallics 1985, 4. 74. (d) Schrock, R. R. Polyhedron 1995, 14, 3177.
41. Preparation and applications of tungsten alkylidyne complexes: (a) Schrock, R. R.; Clark, D. N.; Sancho, J.; Wengrovius, J. H.; Rocklage, S. M.; Pedersen, S. F. Organometallics 1982, 1, 1645. (b) Freudenberger, J. H.; Schrock, R. R.; Churchill, M. R.; Rheingold, A. L.; Ziller, J. W. Organometallics 1984, 3, 1563. (c) Listemann, M. L.; Schrock, R. R. Organometallics 1985, 4. 74. (d) Schrock, R. R. Polyhedron 1995, 14, 3177.
42. For the use of Schrock-type alkylidyne complexes of transition metals other than tungsten in alkyne metathesis see the following for leading references: (a) McCullough, L. G.; Schrock, R R.; Dewan, J C.; Murdzek, J. C. J. Am. Chem. Soc. 1985, 107, 5987 (b) Weinstock, I. A.; Schrock, R. R., Davis, W. M. J. Am. Chem. Soc. 1991, 113, 135.
43. For the use of Schrock-type alkylidyne complexes of transition metals other than tungsten in alkyne metathesis see the following for leading references: (a) McCullough, L. G.; Schrock, R R.; Dewan, J C.; Murdzek, J. C. J. Am. Chem. Soc. 1985, 107, 5987 (b) Weinstock, I. A.; Schrock, R. R., Davis, W. M. J. Am. Chem. Soc. 1991, 113, 135.
44. (a) Mortreux, A.; Blanchard, M. J. Chem. Soc., Chem. Commun. 1974, 786.
45. (b) Mortreux, A.; Dy, N.; Blanchard, M. J. Mol. Catal. 1975, 1, 101
46. (c) Du Plessis, J. A. K.; Vosloo, H. C. M. J. Mol. Catal. 1991, 65, 51.
47. (d) Vosloo, H. C. M., du Plessis, J. A. K. J. Mol. Catal. A 1998, 133, 205.
48. (e) For related initiator systems see also: Bencheick, A.; Petit, M.; Mortreux, A.; Petit, F. J. Mol. Catal. 1982, 15, 93
49. (a) Weiss, K.; Michel, A : Auth, E.-M.; Bunz, U. H. F.; Mangel, T.; Müllen K. Angew. Chem. 1997, 109, 522; Angew. Chem., Int. Ed. Engl. 1997, 36, 506.
50. (a) Weiss, K.; Michel, A : Auth, E.-M.; Bunz, U. H. F.; Mangel, T.; Müllen K. Angew. Chem. 1997, 109, 522; Angew. Chem., Int. Ed. Engl. 1997, 36, 506.
51. (b) Kloppenburg, L.; Song, D.; Bunz, U. H. F. J. Am. Chem. Soc. 1998, 120, 7973.
52. (c) Zhang, X.-P., Bazan, G. C. Macromolecules 1994, 27, 4627.
53. (d) Krouse, S. A.; Schrock, R. R. Macromolecules 1989, 22, 2569.
54. (a) Villemin, D.; Cadiot, P. Tetrahedron Lett. 1982, 23, 5139.
55. (b) Pschirer, N. G.; Bunz, U. H. F. Tetrahedron Lett. 1999, 40, 2481.
56. (c) Kaneta, N.; Hirai, T.; Mori, M. Chem. Lett. 1995, 627
57. (d) Kaneta, N.; Hikichi, K.; Asaka, S.-I ; Uemura, M.; Mori, M. Chem. Lett. 1995, 1055.
58. (a) For a preliminary communication see: Fürstner, A.; Seidel, G. Angew. Chem 1998, 110, 1758; Angew. Chem., Int. Ed. Engl. 1998, 37, 1734. (b) See also: Fürstner, A.; Mathes, C.; Lehmann, C. W. J. Am. Chem. Soc. 1999, 121, 9453.
59. (a) For a preliminary communication see: Fürstner, A.; Seidel, G. Angew. Chem 1998, 110, 1758; Angew. Chem., Int. Ed. Engl. 1998, 37, 1734. (b) See also: Fürstner, A.; Mathes, C.; Lehmann, C. W. J. Am. Chem. Soc. 1999, 121, 9453.
60. (a) For a preliminary communication see: Fürstner, A.; Seidel, G. Angew. Chem 1998, 110, 1758; Angew. Chem., Int. Ed. Engl. 1998, 37, 1734. (b) See also: Fürstner, A.; Mathes, C.; Lehmann, C. W. J. Am. Chem. Soc. 1999, 121, 9453.
61. For a convenient preparation of 2 see: Akiyama, M.; Chisholm, M. H.; Cotton, F. A.; Extine, M. W.; Haitko, D. A.; Little, D.; Fanwick, P. E. Inorg. Chem. 1979, 18, 2266.
62. Terminal alkynes are mainly polymerized in the presence of 1a and related catalysts, cf.: Bray, A.; Mortreux, A.; Petit, F.; Petit, M.; Szymanska-Buzar, T. J. Chem. Soc., Chem. Commun. 1993, 197.
63. In some cases, reactions performed in chorobenzene or toluene stop at ca. 90% conversion of the diyne substrate (cf. Table 1) and complete conversion can be reached neither by increasing the catalyst loading nor by prolonged reaction times.
64. For literature methods allowing the preparation of cycloalkynes (and/ or cycloallenes) see the following for leading references: (a) Review: Meier, H. Synthesis 1972, 235. (b) Boivin, J.; Huppé, S.; Zard, S. Z. Tetrahedron Lett. 1995, 36, 5737. (c) Schreiber, J.; Felix, D.; Eschenmoser, A.; Winter, M.; Gautschi, F.; Schulte-Elte, K. H.; Sundt, E.; Ohloff, G.; Kalvoda, J.; Kaufmann, H.; Wieland, P.; Anner, G. Helv. Chim. Acta 1967, 50, 2101. (d) Mandeville, W. H.; Whitesides, G. M. J. Org. Chem. 1986, 51, 3257. (e) Brummond, K. M.; Gesenberg, K. D.; Kent, J L.; Kerekes, A. D. Tetrahedron Lett. 1998, 39, 8613.
65. For literature methods allowing the preparation of cycloalkynes (and/ or cycloallenes) see the following for leading references: (a) Review: Meier, H. Synthesis 1972, 235. (b) Boivin, J.; Huppé, S.; Zard, S. Z. Tetrahedron Lett. 1995, 36, 5737. (c) Schreiber, J.; Felix, D.; Eschenmoser, A.; Winter, M.; Gautschi, F.; Schulte-Elte, K. H.; Sundt, E.; Ohloff, G.; Kalvoda, J.; Kaufmann, H.; Wieland, P.; Anner, G. Helv. Chim. Acta 1967, 50, 2101. (d) Mandeville, W. H.; Whitesides, G. M. J. Org. Chem. 1986, 51, 3257. (e) Brummond, K. M.; Gesenberg, K. D.; Kent, J L.; Kerekes, A. D. Tetrahedron Lett. 1998, 39, 8613.
66. For literature methods allowing the preparation of cycloalkynes (and/ or cycloallenes) see the following for leading references: (a) Review: Meier, H. Synthesis 1972, 235. (b) Boivin, J.; Huppé, S.; Zard, S. Z. Tetrahedron Lett. 1995, 36, 5737. (c) Schreiber, J.; Felix, D.; Eschenmoser, A.; Winter, M.; Gautschi, F.; Schulte-Elte, K. H.; Sundt, E.; Ohloff, G.; Kalvoda, J.; Kaufmann, H.; Wieland, P.; Anner, G. Helv. Chim. Acta 1967, 50, 2101. (d) Mandeville, W. H.; Whitesides, G. M. J. Org. Chem. 1986, 51, 3257. (e) Brummond, K. M.; Gesenberg, K. D.; Kent, J L.; Kerekes, A. D. Tetrahedron Lett. 1998, 39, 8613.
67. For literature methods allowing the preparation of cycloalkynes (and/ or cycloallenes) see the following for leading references: (a) Review: Meier, H. Synthesis 1972, 235. (b) Boivin, J.; Huppé, S.; Zard, S. Z. Tetrahedron Lett. 1995, 36, 5737. (c) Schreiber, J.; Felix, D.; Eschenmoser, A.; Winter, M.; Gautschi, F.; Schulte-Elte, K. H.; Sundt, E.; Ohloff, G.; Kalvoda, J.; Kaufmann, H.; Wieland, P.; Anner, G. Helv. Chim. Acta 1967, 50, 2101. (d) Mandeville, W. H.; Whitesides, G. M. J. Org. Chem. 1986, 51, 3257. (e) Brummond, K. M.; Gesenberg, K. D.; Kent, J L.; Kerekes, A. D. Tetrahedron Lett. 1998, 39, 8613.
68. For literature methods allowing the preparation of cycloalkynes (and/ or cycloallenes) see the following for leading references: (a) Review: Meier, H. Synthesis 1972, 235. (b) Boivin, J.; Huppé, S.; Zard, S. Z. Tetrahedron Lett. 1995, 36, 5737. (c) Schreiber, J.; Felix, D.; Eschenmoser, A.; Winter, M.; Gautschi, F.; Schulte-Elte, K. H.; Sundt, E.; Ohloff, G.; Kalvoda, J.; Kaufmann, H.; Wieland, P.; Anner, G. Helv. Chim. Acta 1967, 50, 2101. (d) Mandeville, W. H.; Whitesides, G. M. J. Org. Chem. 1986, 51, 3257. (e) Brummond, K. M.; Gesenberg, K. D.; Kent, J L.; Kerekes, A. D. Tetrahedron Lett. 1998, 39, 8613.
69. Stevenson, M. A.; Hopkins, M. D. Organometallics 1997, 16, 3572.
70. (a) Ohloff, G. Riechstoffe und Geruchssinn; Springer: Berlin, 1990.
71. (b) Lehmann, J.; Tochtermann, W. Tetrahedron 1999, 55, 2639.
72. (a) Doss, R. P.; Gould, S. J.; Johnson, K. J. R.; Flath, R. A.; Kohnert, R. L. Photochemistry 1989, 28, 3311.
73. (b) Rodefeld, L.; Tochtermann, W. Tetrahedron 1998, 54, 5893.
74. Isolation: Attygalle, A. B.; McCormick, K. D., Blankespoor, C. L.; Eisner, T.; Meinwald, J. Proc. Natl. Acad. Sci. U.S.A. 1993, 90, 5204.
75. Previous syntheses: (a) Farmer, J. J.; Attygalle, A. B.; Smedley, S. R.; Eisner, T.; Meinwald, J. Tetrahedron Lett. 1997, 38, 2787. (b) Rao, B. V.; Kumar, V. S.; Nagarajan, M.; Sitaramaiah, D., Rama Rao, A V. Tetrahedron Lett. 1996, 37, 8613. (c) Gribble, G. W.; Silva, R. A. Tetrahedron Lett. 1996, 37, 2145. (d) King, A. G.; Meinwald, J.; Eisner, T.; Blankespoor, C. L. Tetrahedron Lett. 1996, 37, 2141. (e) Rama Rao, A. V.; Rao, B. V.; Bhanu, M. N.; Kumar, V. S. Tetrahedron Lett. 1994, 35, 3201.
76. Previous syntheses: (a) Farmer, J. J.; Attygalle, A. B.; Smedley, S. R.; Eisner, T.; Meinwald, J. Tetrahedron Lett. 1997, 38, 2787. (b) Rao, B. V.; Kumar, V. S.; Nagarajan, M.; Sitaramaiah, D., Rama Rao, A V. Tetrahedron Lett. 1996, 37, 8613. (c) Gribble, G. W.; Silva, R. A. Tetrahedron Lett. 1996, 37, 2145. (d) King, A. G.; Meinwald, J.; Eisner, T.; Blankespoor, C. L. Tetrahedron Lett. 1996, 37, 2141. (e) Rama Rao, A. V.; Rao, B. V.; Bhanu, M. N.; Kumar, V. S. Tetrahedron Lett. 1994, 35, 3201.
77. Previous syntheses: (a) Farmer, J. J.; Attygalle, A. B.; Smedley, S. R.; Eisner, T.; Meinwald, J. Tetrahedron Lett. 1997, 38, 2787. (b) Rao, B. V.; Kumar, V. S.; Nagarajan, M.; Sitaramaiah, D., Rama Rao, A V. Tetrahedron Lett. 1996, 37, 8613. (c) Gribble, G. W.; Silva, R. A. Tetrahedron Lett. 1996, 37, 2145. (d) King, A. G.; Meinwald, J.; Eisner, T.; Blankespoor, C. L. Tetrahedron Lett. 1996, 37, 2141. (e) Rama Rao, A. V.; Rao, B. V.; Bhanu, M. N.; Kumar, V. S. Tetrahedron Lett. 1994, 35, 3201.
78. Previous syntheses: (a) Farmer, J. J.; Attygalle, A. B.; Smedley, S. R.; Eisner, T.; Meinwald, J. Tetrahedron Lett. 1997, 38, 2787. (b) Rao, B. V.; Kumar, V. S.; Nagarajan, M.; Sitaramaiah, D., Rama Rao, A V. Tetrahedron Lett. 1996, 37, 8613. (c) Gribble, G. W.; Silva, R. A. Tetrahedron Lett. 1996, 37, 2145. (d) King, A. G.; Meinwald, J.; Eisner, T.; Blankespoor, C. L. Tetrahedron Lett. 1996, 37, 2141. (e) Rama Rao, A. V.; Rao, B. V.; Bhanu, M. N.; Kumar, V. S. Tetrahedron Lett. 1994, 35, 3201.
79. Previous syntheses: (a) Farmer, J. J.; Attygalle, A. B.; Smedley, S. R.; Eisner, T.; Meinwald, J. Tetrahedron Lett. 1997, 38, 2787. (b) Rao, B. V.; Kumar, V. S.; Nagarajan, M.; Sitaramaiah, D., Rama Rao, A V. Tetrahedron Lett. 1996, 37, 8613. (c) Gribble, G. W.; Silva, R. A. Tetrahedron Lett. 1996, 37, 2145. (d) King, A. G.; Meinwald, J.; Eisner, T.; Blankespoor, C. L. Tetrahedron Lett. 1996, 37, 2141. (e) Rama Rao, A. V.; Rao, B. V.; Bhanu, M. N.; Kumar, V. S. Tetrahedron Lett. 1994, 35, 3201.
80. Fürstner, A.; Langemann, K. Synthesis 1997, 792.
81. Kobayashi, J.; Watanabe, D.; Kawasaki, N.; Tsuda, M. J. Org. Chem. 1997, 62, 9236.
82. For reviews on manzamines and related alkaloids see: (a) Magnier, E.; Langlois, Y. Tetrahedron 1998, 54, 6201. (b) Matzanke, N.; Gregg, R. J.; Weinreb, S. M. Org. Prep. Proc. Int. 1998, 30, 1. (c) Tsuda, M.; Kobayashi, J. Heterocycles 1997, 46, 765. For recent total syntheses of manzamine A see: (d) Martin, S. F.; Humphrey, J. M.; Ali, A.; Hillier, M. C. J. Am. Chem. Soc. 1999, 121, 866. (e) Winkler, J. D.; Axten, J. M. J. Am. Chem. Soc. 1998, 120, 6425.
83. For reviews on manzamines and related alkaloids see: (a) Magnier, E.; Langlois, Y. Tetrahedron 1998, 54, 6201. (b) Matzanke, N.; Gregg, R. J.; Weinreb, S. M. Org. Prep. Proc. Int. 1998, 30, 1. (c) Tsuda, M.; Kobayashi, J. Heterocycles 1997, 46, 765. For recent total syntheses of manzamine A see: (d) Martin, S. F.; Humphrey, J. M.; Ali, A.; Hillier, M. C. J. Am. Chem. Soc. 1999, 121, 866. (e) Winkler, J. D.; Axten, J. M. J. Am. Chem. Soc. 1998, 120, 6425.
84. For reviews on manzamines and related alkaloids see: (a) Magnier, E.; Langlois, Y. Tetrahedron 1998, 54, 6201. (b) Matzanke, N.; Gregg, R. J.; Weinreb, S. M. Org. Prep. Proc. Int. 1998, 30, 1. (c) Tsuda, M.; Kobayashi, J. Heterocycles 1997, 46, 765. For recent total syntheses of manzamine A see: (d) Martin, S. F.; Humphrey, J. M.; Ali, A.; Hillier, M. C. J. Am. Chem. Soc. 1999, 121, 866. (e) Winkler, J. D.; Axten, J. M. J. Am. Chem. Soc. 1998, 120, 6425.
85. For reviews on manzamines and related alkaloids see: (a) Magnier, E.; Langlois, Y. Tetrahedron 1998, 54, 6201. (b) Matzanke, N.; Gregg, R. J.; Weinreb, S. M. Org. Prep. Proc. Int. 1998, 30, 1. (c) Tsuda, M.; Kobayashi, J. Heterocycles 1997, 46, 765. For recent total syntheses of manzamine A see: (d) Martin, S. F.; Humphrey, J. M.; Ali, A.; Hillier, M. C. J. Am. Chem. Soc. 1999, 121, 866. (e) Winkler, J. D.; Axten, J. M. J. Am. Chem. Soc. 1998, 120, 6425.
86. For reviews on manzamines and related alkaloids see: (a) Magnier, E.; Langlois, Y. Tetrahedron 1998, 54, 6201. (b) Matzanke, N.; Gregg, R. J.; Weinreb, S. M. Org. Prep. Proc. Int. 1998, 30, 1. (c) Tsuda, M.; Kobayashi, J. Heterocycles 1997, 46, 765. For recent total syntheses of manzamine A see: (d) Martin, S. F.; Humphrey, J. M.; Ali, A.; Hillier, M. C. J. Am. Chem. Soc. 1999, 121, 866. (e) Winkler, J. D.; Axten, J. M. J. Am. Chem. Soc. 1998, 120, 6425.
87. (a) Fürstner, A.; Weintritt, H. J. Am. Chem. Soc. 1998, 120, 2817.
88. (b) Fürstner, A.; Weintritt, H. J. Am. Chem. Soc. 1997, 119, 2944.
89. Products 56-61 shown in Scheme 7 were obtained as mixtures of different stereoisomers. Since all of them converge into the final product, no attempts were made to separate the individual compounds.
90. Reviews: (a) Tsuji, J. Palladium Reagents and Catalysts; Wiley: New York, 1995. (b) Trost, B. M. Angew. Chem., Int. Ed. Engl. 1989, 28, 1173.
91. Reviews: (a) Tsuji, J. Palladium Reagents and Catalysts; Wiley: New York, 1995. (b) Trost, B. M. Angew. Chem., Int. Ed. Engl. 1989, 28, 1173.
92. Högberg, T.; Ström, P.; Ebner, M.; Rämsby, S. J. Org. Chem. 1987, 52, 2033. These authors describe the catalytic effect of NaCN in the transformation of esters to amides; in our case, however, the addition of ≥1 equiv of this promoter was necessary to achieve quantitative conversion.
93. The excellent yield shows that both the (Z)- and the (E)-isomer of 61 cyclize to furan 62 under the acidic reaction conditions. For another application of this new approach to furans see: Fürstner, A.; Gastner, T.; Rust, J. Synlett 1999, 29.
94. Compound 66 was analogously prepared in a model study toward manzamin A, cf.: Winkler, J. D.; Stelmach, J. E.; Axten, J. Tetrahedron Lett. 1996, 37, 4317.
95. Details will be reported in a separate publication.