Cascade radical cyclisations leading to polycyclic diterpenes. Total synthesis of (±)-spongian-16-one

Abstract

A cascade of three consecutive 6-endo-trig radical cyclisations from the polyene acyl radical intermediate 12 derived from the selenoate 11 is used to construct the trans,anti,trans,anti,cis-tetracyclic keto lactone 20 in one step. Manipulation of the ketone function in 20 to the corresponding gem-dimethyl substituted carbon then completed a concise synthesis of the marine metabolite spongian-16-one 1.

References

1. G. Cimino, R. Morrone and G. Sodano, Tetrahedron Lett., 1982, 23, 4139.
2. M. R. Kernan, R. C. Cambie and P. R. Bergquist, J. Nat. Prod., 1990, 53, 724.
3. T. W. Hambley, A. Poiner and W. C. Taylor, Aust. J. Chem., 1990, 43, 1861.
4. A. G. Gonzalez, D. M. Estrada, J. D. Martin, V. S. Martin, C. Perez and R. Perez, Tetrahedron, 1984, 40, 4109.
5. S. Kohmoto, O. J. McConnell, A. Wright and S. Cross, Chem. Lett., 1987, 168; R. Kazauskas, P. T. Murphy, R. J. Wells, K. Noack, W. E. Oberhansli and P. Schonoholzer, Aust. J. Chem., 1979, 32, 867.
6. T. Nakano and M. I. Hernández, Tetrahedron Lett., 1982, 1423; D. S. de Miranda, G. Brendolan, P. M. Imamura, M. González-Sierra, A. J. Marsaioli and E. A. Rúveda, J. Org. Chem., 1981, 46, 4851; P. M. Imamura, M. González-Sierra and E. A. Rúveda, J. Chem. Soc., Chem. Commun., 1981, 734; T. Nakano, M. I. Hernández, M. Gomez and J. D. Medina, J. Chem. Res. Synop., 1989, 54; M. G. Sierra, M. P. Mischne and E. A. Rúveda, Synth. Commun., 1985, 15, 27; T. Sakamoto and K. Kanematsu, Tetrahedron, 1995, 51, 5771.
7. For studies of oxidative radical cyclisations of polyenes and applications to the synthesis of (±)-isospongiadiol see: P. A. Zoretic, M. Wang, Y. Zhang and Z. Shen, J. Org. Chem., 1996, 61, 1806 and references cited therein.
8. L. Chen, G. B. Gill, G. Pattenden and H. Simonian, J. Chem. Soc., Perkin Trans. 1, 1996, 31; A. Batsanov, L. Chen, G. B. Gill and G. Pattenden, J. Chem. Soc., Perkin Trans. 1, 1996, 45 and references cited therein.
9. P. Double and G. Pattenden, unpublished work.
10. G. Pattenden and L. Roberts, Tetrahedron Lett., 1996, 37, 4191.
11. S. Hatakeyama, H. Numata, K. Osanai and S. Takano, J. Chem. Soc., Chem. Commun., 1989, 1893 cf. G. Cahiez, A. Alexakis and J. F. Normant, Tetrahedron Lett., 1978, 3013.
12. S. A. Godleski, D. J. Heacock, J. D. Meinhart and S. Van Wallendael, J. Org. Chem., 1983, 48, 2101; S. A. Stanton, S. W. Felman, C. S. Parkhurst and S. A. Godleski, J. Am. Chem. Soc., 1983, 105, 19.
13. W. S. Johnson, R. A. Buchanan, W. R. Bartlett, F. S. Tham and R. K. Knullnig, J. Am. Chem. Soc., 1993, 115, 504.
14. M. Julia, S. Julia and R. Guegan, Bull. Soc. Chim. Fr., 1960, 1072.
15. K. Iwai, H. Kosugi, H. Uda and M. Kawai, Bull. Chem. Soc. Jpn., 1977, 50, 242.
16. B. M. Trost, M. K.-T. Mao, J. M. Balkovec and P. Buhlmayer, J. Am. Chem. Soc., 1986, 108, 4965.
17. K. C. Nicolaou, N. A. Petasis and D. A. Claremon, Tetrahedron, 1985, 41, 4835.
18. L. Lombardo, Org. Synth., 1987, 81.
19. P. A. Wender and S. L. Eck, Tetrahedron Lett., 1982, 1871; B. M. Trost and H. Hiemstra, J. Am. Chem. Soc., 1982, 104, 886; W. Oppolzer and T. Godel, J. Am. Chem. Soc., 1978, 100, 2583.
20. The data reorted by Cambie (ref. 2) for natural spongian-16-one isolated from D. cavernosa[mp 155–°C, [α]_D+53 (c 0.0011, CHCl₃)] differ somewhat to the data [mp 200 °C, [α]_D–6.7 (c 1.0), certain shift data in the ¹H NMR spectrum] reported for spongian-16-one from C. violacea(ref. 3). A stereoisomer of 1, with the opposite stereochemistry at C13 (i.e. trans ring fused lactone) has been characterised amongst the products of hydrogenation of natural 3, a metabolite from Spongia officinalis(ref. 4) this compound is non-crystalline and shows [α]_D+ 14.2 (c, 0.9 CHCHl₃)..
21. G. M. Sheldrick, SHELXS-86, Acta Crystallogr., Sect. A, 1990, 46, 467.
22. G. M. Sheldrick, SHELXL-93, University of Göttingen, Germany, 1993.
23. G. M. Sheldrick, SHELXTL/PC, version 5.03, Siemens Analytical Instruments Inc., Madison, WI, 1995.