Synthesis based on cyclohexadienes. Part 24.¹ A new total synthesis of pupukean-2-one and a facile entry to copa and ylanga type sesquiterpene skeletons

Abstract

A novel tandem 5-exo-trig allyl and 3-exo-trig radical cyclisation and rearrangement to copa and ylanga type sesquiterpene skeletons from easily prepared cyclohexadienes is reported. A new total synthesis of pupukean-2-one 8, which belongs to a novel class of sesquiterpenes, involving a 5-exo-trig allyl radical cyclisation as the key step is also reported.

References

1. For part 23 of the series; see, K. Kaliappan and G. S. R. Subba Rao, preceding paper.
2. M. A. Qaseem, N. A. J. Rogers and A. A. Othman, Tetrahedron, 1968, 24, 4535.
3. T. Uyehara, K. Osanai, M. Sugimoto, I. Suzuki and Y. Yamamoto, J. Am. Chem. Soc., 1989, 111, 7264.
4. P. S. Shanker and G. S. R. Subba Rao, J. Chem. Soc., Chem. Commun., 1994, 621.
5. P. S. Shanker and G. S. R. Subba Rao, Tetrahedron Lett., 1994, 5055.
6. K. Kaliappan and G. S. R. Subba Rao, J. Chem. Soc., Chem. Commun., 1996, 2331.
7. K. Kaliappan and G. S. R. Subba Rao, Tetrahedron Lett., 1997, 2185.
8. D. A. Evans, W. L. Scott and L. K. Truesdale, Tetrahedron Lett., 1972, 121.
9. (a) B. Giese, Radicals in Organic Synthesis: Formation of Carbon-Carbon Bonds, Pergamon Press, Oxford, 1986; (b) A. L. J. Beckwith, Tetrahedron, 1981, 37, 3073; (c) B. Giese, Angew. Chem., Int. Ed. Engl., 1983, 22, 753; (d) D. J. Hart, Science, 1984, 223, 883; (e) B. Giese, ed., Selectivity and Synthetic Applications of Radical Reactions, Tetrahedron Symposia-in-print, Tetrahedron, 1985, 41, 3887; (f) B. Giese, Angew. Chem., Int. Ed. Engl., 1985, 24, 553; (g) M. Ramaiah, Tetrahedron, 1987, 43, 3541; (h) A. Srikrishna, Current Science, 1987, 56, 392; (i) D. P. Curran, Synthesis, 1988, 417 and 489; (j) G. Pattenden, Chem. Soc. Rev., 1988, 17, 361; (k) C. P. Jasperse, D. P. Curran and T. L. Fevig, Chem. Rev., 1991, 92, 1237; (l) N. A. Porter, B. Giese and D. P. Curran, Acc. Chem. Res., 1991, 24, 296; (m) D. P. Curran, Synlett, 1991, 63; (n) J. E. Baldwin, J. Chem. Soc., Chem. Commun., 1976, 734.
10. G. Stork and M. E. Reynolds, J. Am. Chem. Soc., 1988, 110, 6121.
11. N. J. G. Cox, G. Pattenden and S. D. Mills, Tetrahedron Lett., 1989, 30, 621.
12. S. A. Hitchcok and G. Pattenden, Tetrahedron Lett., 1990, 31, 3641.
13. H. Staudinger, O. Muntwyler and O. Kupfer, Helv. Chim. Acta, 1922, 5, 756.
14. F. Bohlmann, H. Suding, J. Cuatrecasas, H. Robinson and R. M. King, Phytochemistry, 1980, 19, 2399.
15. C. M. Beecham, C. Djerassi, J. S. Finer and J. Clardy, Tetrahedron Lett., 1977, 2395.
16. P. de Mayo and R. M. Williams, J. Am. Chem. Soc., 1965, 87, 3275.
17. T. Takemoto, N. Nishimoto, S. Nakai, N. Takagi, S. Hayashi, S. Odashima and Y. Wada, Tetrahedron Lett., 1983, 24, 1057.
18. (a) R. P. Gregson and R. N. Mirrington, Aust. J. Chem., 1976, 29, 2037; (b) A. J. Birch and G. S. R. Subba Rao, Aust. J. Chem., 1970, 23, 1641.
19. (a) G. Frater and J. Wenger, Helv. Chim. Acta, 1984, 67, 1702; (b) N. C. Chang and C. K. Chang, J. Org. Chem., 1996, 61, 4967.
20. For a detailed general note, see ref. 1.