A comparative study of the solvolysis reactivity, regioselectivity, and stereochemistry of the duocarmycin A and SA alkylation subunits

Bioorganic and Medicinal Chemistry Letters

Volumn 6, Issue 16, 1996, Pages 1955-1960

  Boger, Dale L ^a   Goldberg, Joel ^a   McKie, Jeffrey A ^a  

^a SCRIPPS RESEARCH INSTITUTE   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

DUOCARMYCIN A; DUOCARMYCIN SA; UNCLASSIFIED DRUG;

ARTICLE; CYTOTOXICITY; DNA ALKYLATION; DRUG SOLUBILITY; DRUG STRUCTURE; DRUG SYNTHESIS; REACTION ANALYSIS; STRUCTURE ACTIVITY RELATION;

EID: 0030594978     PISSN: 0960894X     EISSN: None     Source Type: Journal    
DOI: 10.1016/0960-894X(96)00346-0     Document Type: Article

References (47)

1. 1. Ichimura, M.; Ogawa, T.; Takahashi, K.; Kobayashi, E.; Kawamoto, I.; Yasuzawa, T.; Takahashi, I.; Nakano, H. J. Antibiot. 1990, 43, 1037.
2. 2. Takahashi, I.; Takahashi, K.; Ichimura, M.; Morimoto, M.; Asano, K.; Kawamoto, I.; Tomita, F.; Nakano, H. J. Antibiot. 1988, 41, 1915.
3. 3. Yasuzawa, T.; Muroi, K.; Ichimura, M.; Takahashi, I.; Ogawa, T.; Takahashi, K.; Sano, H.; Saitoh, Y. Chem. Pharm. Bull. 1995, 43, 378.
4. 4. Chidester, C. G.; Krueger, W. C.; Mizsak, S. A.; Duchamp, D. J.; Martin, D. G. J. Am. Chem. Soc. 1981, 103, 7629.
5. 5. Boger, D. L.; Johnson, D. S. Angew Chem., Int. Ed. Engl. in press. Boger, D. L.; Johnson, D. S. Proc. Natl. Acad. Sci., U.S.A. 1995, 92, 3642. Boger, D. L. Acc. Chem. Res. 1995, 28, 20. 103. Boger, D. L. In Advances in Heterocyclic Natural Product Synthesis, Pearson, W. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 2, 1. Boger, D. L. Chemtracts: Org. Chem. 1991, 4, 329. Boger, D. L. In Proc. R. A. Welch Found. Conf. Chem. Res., XXXV., Chem. Frontiers Med. 1991, 35, 137. Boger, D. L. In Heterocycles in Bioorganic Chemistry, Bergman, J.; van der Plas, H. C.; Simonyl, M., Eds.; Royal Soc. of Chem.: Cambridge, 1991; 103. Coleman, R. S.; Boger, D. L. In Studies in Natural Products Chemistry; Rahman, A.-u.-, Ed.; Elsevier: Amsterdam, 1989; Vol. 3, 301.
6. 5. Boger, D. L.; Johnson, D. S. Angew Chem., Int. Ed. Engl. in press. Boger, D. L.; Johnson, D. S. Proc. Natl. Acad. Sci., U.S.A. 1995, 92, 3642. Boger, D. L. Acc. Chem. Res. 1995, 28, 20. 103. Boger, D. L. In Advances in Heterocyclic Natural Product Synthesis, Pearson, W. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 2, 1. Boger, D. L. Chemtracts: Org. Chem. 1991, 4, 329. Boger, D. L. In Proc. R. A. Welch Found. Conf. Chem. Res., XXXV., Chem. Frontiers Med. 1991, 35, 137. Boger, D. L. In Heterocycles in Bioorganic Chemistry, Bergman, J.; van der Plas, H. C.; Simonyl, M., Eds.; Royal Soc. of Chem.: Cambridge, 1991; 103. Coleman, R. S.; Boger, D. L. In Studies in Natural Products Chemistry; Rahman, A.-u.-, Ed.; Elsevier: Amsterdam, 1989; Vol. 3, 301.
7. 5. Boger, D. L.; Johnson, D. S. Angew Chem., Int. Ed. Engl. in press. Boger, D. L.; Johnson, D. S. Proc. Natl. Acad. Sci., U.S.A. 1995, 92, 3642. Boger, D. L. Acc. Chem. Res. 1995, 28, 20. 103. Boger, D. L. In Advances in Heterocyclic Natural Product Synthesis, Pearson, W. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 2, 1. Boger, D. L. Chemtracts: Org. Chem. 1991, 4, 329. Boger, D. L. In Proc. R. A. Welch Found. Conf. Chem. Res., XXXV., Chem. Frontiers Med. 1991, 35, 137. Boger, D. L. In Heterocycles in Bioorganic Chemistry, Bergman, J.; van der Plas, H. C.; Simonyl, M., Eds.; Royal Soc. of Chem.: Cambridge, 1991; 103. Coleman, R. S.; Boger, D. L. In Studies in Natural Products Chemistry; Rahman, A.-u.-, Ed.; Elsevier: Amsterdam, 1989; Vol. 3, 301.
8. 5. Boger, D. L.; Johnson, D. S. Angew Chem., Int. Ed. Engl. in press. Boger, D. L.; Johnson, D. S. Proc. Natl. Acad. Sci., U.S.A. 1995, 92, 3642. Boger, D. L. Acc. Chem. Res. 1995, 28, 20. 103. Boger, D. L. In Advances in Heterocyclic Natural Product Synthesis, Pearson, W. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 2, 1. Boger, D. L. Chemtracts: Org. Chem. 1991, 4, 329. Boger, D. L. In Proc. R. A. Welch Found. Conf. Chem. Res., XXXV., Chem. Frontiers Med. 1991, 35, 137. Boger, D. L. In Heterocycles in Bioorganic Chemistry, Bergman, J.; van der Plas, H. C.; Simonyl, M., Eds.; Royal Soc. of Chem.: Cambridge, 1991; 103. Coleman, R. S.; Boger, D. L. In Studies in Natural Products Chemistry; Rahman, A.-u.-, Ed.; Elsevier: Amsterdam, 1989; Vol. 3, 301.
9. 5. Boger, D. L.; Johnson, D. S. Angew Chem., Int. Ed. Engl. in press. Boger, D. L.; Johnson, D. S. Proc. Natl. Acad. Sci., U.S.A. 1995, 92, 3642. Boger, D. L. Acc. Chem. Res. 1995, 28, 20. 103. Boger, D. L. In Advances in Heterocyclic Natural Product Synthesis, Pearson, W. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 2, 1. Boger, D. L. Chemtracts: Org. Chem. 1991, 4, 329. Boger, D. L. In Proc. R. A. Welch Found. Conf. Chem. Res., XXXV., Chem. Frontiers Med. 1991, 35, 137. Boger, D. L. In Heterocycles in Bioorganic Chemistry, Bergman, J.; van der Plas, H. C.; Simonyl, M., Eds.; Royal Soc. of Chem.: Cambridge, 1991; 103. Coleman, R. S.; Boger, D. L. In Studies in Natural Products Chemistry; Rahman, A.-u.-, Ed.; Elsevier: Amsterdam, 1989; Vol. 3, 301.
10. 5. Boger, D. L.; Johnson, D. S. Angew Chem., Int. Ed. Engl. in press. Boger, D. L.; Johnson, D. S. Proc. Natl. Acad. Sci., U.S.A. 1995, 92, 3642. Boger, D. L. Acc. Chem. Res. 1995, 28, 20. 103. Boger, D. L. In Advances in Heterocyclic Natural Product Synthesis, Pearson, W. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 2, 1. Boger, D. L. Chemtracts: Org. Chem. 1991, 4, 329. Boger, D. L. In Proc. R. A. Welch Found. Conf. Chem. Res., XXXV., Chem. Frontiers Med. 1991, 35, 137. Boger, D. L. In Heterocycles in Bioorganic Chemistry, Bergman, J.; van der Plas, H. C.; Simonyl, M., Eds.; Royal Soc. of Chem.: Cambridge, 1991; 103. Coleman, R. S.; Boger, D. L. In Studies in Natural Products Chemistry; Rahman, A.-u.-, Ed.; Elsevier: Amsterdam, 1989; Vol. 3, 301.
11. 5. Boger, D. L.; Johnson, D. S. Angew Chem., Int. Ed. Engl. in press. Boger, D. L.; Johnson, D. S. Proc. Natl. Acad. Sci., U.S.A. 1995, 92, 3642. Boger, D. L. Acc. Chem. Res. 1995, 28, 20. 103. Boger, D. L. In Advances in Heterocyclic Natural Product Synthesis, Pearson, W. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 2, 1. Boger, D. L. Chemtracts: Org. Chem. 1991, 4, 329. Boger, D. L. In Proc. R. A. Welch Found. Conf. Chem. Res., XXXV., Chem. Frontiers Med. 1991, 35, 137. Boger, D. L. In Heterocycles in Bioorganic Chemistry, Bergman, J.; van der Plas, H. C.; Simonyl, M., Eds.; Royal Soc. of Chem.: Cambridge, 1991; 103. Coleman, R. S.; Boger, D. L. In Studies in Natural Products Chemistry; Rahman, A.-u.-, Ed.; Elsevier: Amsterdam, 1989; Vol. 3, 301.
12. 5. Boger, D. L.; Johnson, D. S. Angew Chem., Int. Ed. Engl. in press. Boger, D. L.; Johnson, D. S. Proc. Natl. Acad. Sci., U.S.A. 1995, 92, 3642. Boger, D. L. Acc. Chem. Res. 1995, 28, 20. 103. Boger, D. L. In Advances in Heterocyclic Natural Product Synthesis, Pearson, W. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 2, 1. Boger, D. L. Chemtracts: Org. Chem. 1991, 4, 329. Boger, D. L. In Proc. R. A. Welch Found. Conf. Chem. Res., XXXV., Chem. Frontiers Med. 1991, 35, 137. Boger, D. L. In Heterocycles in Bioorganic Chemistry, Bergman, J.; van der Plas, H. C.; Simonyl, M., Eds.; Royal Soc. of Chem.: Cambridge, 1991; 103. Coleman, R. S.; Boger, D. L. In Studies in Natural Products Chemistry; Rahman, A.-u.-, Ed.; Elsevier: Amsterdam, 1989; Vol. 3, 301.
13. 6. Hurley, L. H.; Needham-VanDevanter, D. R. Acc. Chem. Res. 1986, 19, 230. Warpehoski, M. A.; Hurley, L. H. Chem. Res. Toxicol. 1988, 1, 315. Warpehoski, M. A. In Advances in DNA Sequence Specific Agents; Hurley, L. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 1, 217. Hurley, L. H.; Draves, P. H. In Molecular Aspects of Anticancer Drug-DNA Interactions; Neidle, S.; Waring, M., Eds.; CRC: Ann Arbor, MI, 1993; Vol. 1, 89.
14. 6. Hurley, L. H.; Needham-VanDevanter, D. R. Acc. Chem. Res. 1986, 19, 230. Warpehoski, M. A.; Hurley, L. H. Chem. Res. Toxicol. 1988, 1, 315. Warpehoski, M. A. In Advances in DNA Sequence Specific Agents; Hurley, L. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 1, 217. Hurley, L. H.; Draves, P. H. In Molecular Aspects of Anticancer Drug-DNA Interactions; Neidle, S.; Waring, M., Eds.; CRC: Ann Arbor, MI, 1993; Vol. 1, 89.
15. 6. Hurley, L. H.; Needham-VanDevanter, D. R. Acc. Chem. Res. 1986, 19, 230. Warpehoski, M. A.; Hurley, L. H. Chem. Res. Toxicol. 1988, 1, 315. Warpehoski, M. A. In Advances in DNA Sequence Specific Agents; Hurley, L. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 1, 217. Hurley, L. H.; Draves, P. H. In Molecular Aspects of Anticancer Drug-DNA Interactions; Neidle, S.; Waring, M., Eds.; CRC: Ann Arbor, MI, 1993; Vol. 1, 89.
16. 6. Hurley, L. H.; Needham-VanDevanter, D. R. Acc. Chem. Res. 1986, 19, 230. Warpehoski, M. A.; Hurley, L. H. Chem. Res. Toxicol. 1988, 1, 315. Warpehoski, M. A. In Advances in DNA Sequence Specific Agents; Hurley, L. H., Ed.; JAI: Greenwich, CT, 1992; Vol. 1, 217. Hurley, L. H.; Draves, P. H. In Molecular Aspects of Anticancer Drug-DNA Interactions; Neidle, S.; Waring, M., Eds.; CRC: Ann Arbor, MI, 1993; Vol. 1, 89.
17. 7. Boger, D. L.; Machiya, K. J. Am. Chem. Soc. 1992, 114, 10056. Boger, D. L.; Machiya, K.; Hertzog, D. L.; Kitos, P. A.; Holmes, D. J. Am. Chem. Soc. 1993, 115, 9025.
18. 7. Boger, D. L.; Machiya, K. J. Am. Chem. Soc. 1992, 114, 10056. Boger, D. L.; Machiya, K.; Hertzog, D. L.; Kitos, P. A.; Holmes, D. J. Am. Chem. Soc. 1993, 115, 9025.
19. 8. Boger, D. L.; McKie, J. A.; Nishi, T. Ogiku, J. Am. Chem. Soc. 1996, 118, 2301. Boger, D. L.; McKie, J. A.; Nishi, T.; Ogiku, T. J. Am. Chem. Soc., submitted.
20. 8. Boger, D. L.; McKie, J. A.; Nishi, T. Ogiku, J. Am. Chem. Soc. 1996, 118, 2301. Boger, D. L.; McKie, J. A.; Nishi, T.; Ogiku, T. J. Am. Chem. Soc., submitted.
21. 9. Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H.; Munk, S. A.; Kitos, P. A.; Suntornwat, O. J. Am. Chem. Soc. 1990, 112, 8961. Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H.; Kitos, P. A.; Suntornwat, O. J. Org. Chem. 1990, 55, 4499. Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H. J. Am. Chem. Soc. 1991, 113, 6645.
22. 9. Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H.; Munk, S. A.; Kitos, P. A.; Suntornwat, O. J. Am. Chem. Soc. 1990, 112, 8961. Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H.; Kitos, P. A.; Suntornwat, O. J. Org. Chem. 1990, 55, 4499. Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H. J. Am. Chem. Soc. 1991, 113, 6645.
23. 9. Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H.; Munk, S. A.; Kitos, P. A.; Suntornwat, O. J. Am. Chem. Soc. 1990, 112, 8961. Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H.; Kitos, P. A.; Suntornwat, O. J. Org. Chem. 1990, 55, 4499. Boger, D. L.; Ishizaki, T.; Zarrinmayeh, H. J. Am. Chem. Soc. 1991, 113, 6645.
24. 10. Boger, D. L.; Johnson, D. S.; Yun, W. J. Am. Chem. Soc. 1994, 116, 1635.
25. 11. Boger, D. L.; Yun, W. J. Am. Chem. Soc. 1993, 115, 9872.
26. 12. Sugiyama, H.; Ohmori, K.; Chan, K. L.; Hosoda, M.; Asai, A.; Saito, H.; Saito, I. Tetrahedron Lett. 1993, 34, 2179. Yamamoto, K.; Sugiyama, H.; Kawanishi, S. Biochemistry 1993, 32, 1059. Asai, A.; Nagamura, S.; Saito, H. J. Am. Chem. Soc. 1994, 116, 4171.
27. 12. Sugiyama, H.; Ohmori, K.; Chan, K. L.; Hosoda, M.; Asai, A.; Saito, H.; Saito, I. Tetrahedron Lett. 1993, 34, 2179. Yamamoto, K.; Sugiyama, H.; Kawanishi, S. Biochemistry 1993, 32, 1059. Asai, A.; Nagamura, S.; Saito, H. J. Am. Chem. Soc. 1994, 116, 4171.
28. 12. Sugiyama, H.; Ohmori, K.; Chan, K. L.; Hosoda, M.; Asai, A.; Saito, H.; Saito, I. Tetrahedron Lett. 1993, 34, 2179. Yamamoto, K.; Sugiyama, H.; Kawanishi, S. Biochemistry 1993, 32, 1059. Asai, A.; Nagamura, S.; Saito, H. J. Am. Chem. Soc. 1994, 116, 4171.
29. 8 and only (+)-12 was detected in the solvolysis reaction.
30. 14. Boger, D. L.; Mésini, P. J. Am. Chem. Soc. 1994, 116, 11335. Boger, D. L.; Mésini, P. J. Am. Chem. Soc. 1995, 117, 11647. Boger, D. L.; Mésini, P.; Tarby, C. M. J. Am. Chem. Soc. 1994, 116, 6461.
31. 14. Boger, D. L.; Mésini, P. J. Am. Chem. Soc. 1994, 116, 11335. Boger, D. L.; Mésini, P. J. Am. Chem. Soc. 1995, 117, 11647. Boger, D. L.; Mésini, P.; Tarby, C. M. J. Am. Chem. Soc. 1994, 116, 6461.
32. 14. Boger, D. L.; Mésini, P. J. Am. Chem. Soc. 1994, 116, 11335. Boger, D. L.; Mésini, P. J. Am. Chem. Soc. 1995, 117, 11647. Boger, D. L.; Mésini, P.; Tarby, C. M. J. Am. Chem. Soc. 1994, 116, 6461.
33. 15. Warpehoski, M. A.; Harper, D. E. J. Am. Chem. Soc. 1994, 116, 7573.
34. 16. Boger, D. L.; Han, N.; Tarby, C. M.; Boyce, C. W.; Cai, H.; Jing, Q.; Kitos, P. A. J. Org. Chem. 1996, 61, in press. Boger, D. L.; McKie, J. A.; Han, N.; Tarby, C. M.; Riggs, H. W.; Kitos, P. A. Bioorg. Med. Chem. Lett. 1996, 6, 659.
35. 16. Boger, D. L.; Han, N.; Tarby, C. M.; Boyce, C. W.; Cai, H.; Jing, Q.; Kitos, P. A. J. Org. Chem. 1996, 61, in press. Boger, D. L.; McKie, J. A.; Han, N.; Tarby, C. M.; Riggs, H. W.; Kitos, P. A. Bioorg. Med. Chem. Lett. 1996, 6, 659.
36. 17. Boger, D. L.; McKie, J. A.; Cai, H.; Cacciari, B.; Baraldi, P. G. J. Org. Chem. 1996, 61, 1710.
37. 18. The atomic coordinates for this structure have been deposited with the Cambridge Crystallographic Data Centre and may be obtained upon request from the Director, Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK.
38. 19. Boger, D. L.; Ishizaki, T.; Kitos, P. A.; Suntornwat, O. J. Org. Chem. 1990, 55, 5823. Boger, D. L.; Ishizaki, T.; Wysocki, R. J., Jr.; Munk, S. A.; Kitos, P. A.; Suntornwat, O. J. Am. Chem. Soc. 1989, 111, 6461.
39. 19. Boger, D. L.; Ishizaki, T.; Kitos, P. A.; Suntornwat, O. J. Org. Chem. 1990, 55, 5823. Boger, D. L.; Ishizaki, T.; Wysocki, R. J., Jr.; Munk, S. A.; Kitos, P. A.; Suntornwat, O. J. Am. Chem. Soc. 1989, 111, 6461.
40. 20. Boger, D. L.; Jenkins, T. J. J. Am. Chem. Soc., in press.
41. 21. Martin, D. G.; Kelly, R. C.; Watt, W.; Wienienski, N.; Mizsak, S. A.; Nielsen, J. W.; Prairie, M. D. J. Org. Chem. 1988, 53, 4610.
42. 22. Reynolds, V. L.; Molineux, I. J.; Kaplan, D. J.; Swedson, D. H.; Hurley, L. H. Biochemistry 1985, 24, 6228. Hurley, L. H.; Lee, C.-S.; McGovren, J. P.; Warpehoski, M. A.; Mitchell, M. A.; Kelly, R. C.; Aristoff, P. A. Biochemistry 1988, 27, 3886. Hurley, L. H.; Warpehoski, M. A.; Lee, C.-S.; McGovren, J. P.; Scahill, T. A.; Kelly, R. C.; Mitchell, M. A.; Wienienski, N. A.; Gebhard, I.; Johnson, P. D.; Bradford, V. S. J. Am. Chem. Soc. 1990, 112, 4633.
43. 22. Reynolds, V. L.; Molineux, I. J.; Kaplan, D. J.; Swedson, D. H.; Hurley, L. H. Biochemistry 1985, 24, 6228. Hurley, L. H.; Lee, C.-S.; McGovren, J. P.; Warpehoski, M. A.; Mitchell, M. A.; Kelly, R. C.; Aristoff, P. A. Biochemistry 1988, 27, 3886. Hurley, L. H.; Warpehoski, M. A.; Lee, C.-S.; McGovren, J. P.; Scahill, T. A.; Kelly, R. C.; Mitchell, M. A.; Wienienski, N. A.; Gebhard, I.; Johnson, P. D.; Bradford, V. S. J. Am. Chem. Soc. 1990, 112, 4633.
44. 22. Reynolds, V. L.; Molineux, I. J.; Kaplan, D. J.; Swedson, D. H.; Hurley, L. H. Biochemistry 1985, 24, 6228. Hurley, L. H.; Lee, C.-S.; McGovren, J. P.; Warpehoski, M. A.; Mitchell, M. A.; Kelly, R. C.; Aristoff, P. A. Biochemistry 1988, 27, 3886. Hurley, L. H.; Warpehoski, M. A.; Lee, C.-S.; McGovren, J. P.; Scahill, T. A.; Kelly, R. C.; Mitchell, M. A.; Wienienski, N. A.; Gebhard, I.; Johnson, P. D.; Bradford, V. S. J. Am. Chem. Soc. 1990, 112, 4633.
45. 23. Boger, D. L.; Johnson, D. S.; Yun, W.; Tarby, C. M. Bioorg. Med Chem. 1994, 2, 115. Boger, D. L.; Munk, S. A.; Zarrinmayeh, H.; Ishizaki, T.; Haught, J.; Bina, M. Tetrahedron 1991, 47, 2661. Boger, D. L.; Coleman, R. S.; Invergo, B. J .; Sakya, S. M.; Ishizaki, T.; Munk, S. A.; Zarrinmayeh, H.; Kitos, P. A.; Thompson, S. C. J. Am. Chem. Soc. 1990, 112, 4623.
46. 23. Boger, D. L.; Johnson, D. S.; Yun, W.; Tarby, C. M. Bioorg. Med Chem. 1994, 2, 115. Boger, D. L.; Munk, S. A.; Zarrinmayeh, H.; Ishizaki, T.; Haught, J.; Bina, M. Tetrahedron 1991, 47, 2661. Boger, D. L.; Coleman, R. S.; Invergo, B. J .; Sakya, S. M.; Ishizaki, T.; Munk, S. A.; Zarrinmayeh, H.; Kitos, P. A.; Thompson, S. C. J. Am. Chem. Soc. 1990, 112, 4623.
47. 23. Boger, D. L.; Johnson, D. S.; Yun, W.; Tarby, C. M. Bioorg. Med Chem. 1994, 2, 115. Boger, D. L.; Munk, S. A.; Zarrinmayeh, H.; Ishizaki, T.; Haught, J.; Bina, M. Tetrahedron 1991, 47, 2661. Boger, D. L.; Coleman, R. S.; Invergo, B. J .; Sakya, S. M.; Ishizaki, T.; Munk, S. A.; Zarrinmayeh, H.; Kitos, P. A.; Thompson, S. C. J. Am. Chem. Soc. 1990, 112, 4623.