Progress towards viridin: synthesis of the pentacyclic furanosteroid ring system via o-benzoquinonoid cycloadditions
(Note: The full text of this document is currently only available in the PDF Version )
Fabio E. S. Souza and Russell Rodrigo
Abstract
The pentacyclic ring system of viridin is synthesised in nine steps from 4-methylguaicol by means of successive cycloadditions involving o-benzoquinonoid intermediates generated in situ.
References
For a recent review, see J. R. Hanson, Nat. Prod. Rep., 1995, 12, 381 Search PubMed.
M. M. Blight and J. F. Grove, J. Chem. Soc., Perkin Trans. 1, 1986, 1317 RSC.
T. J. Pecher, H.-P. Weber and S. Kis, J. Chem. Soc., Chem. Commun., 1972, 1061 RSC.
T. Okada, L. Sakuma, Y. Fukui, O. Hazeki and M. Ui, J. Biol. Chem., 1994, 269, 3563 CAS.
S. Sato, M. Nakada and M. Shibasaki, Tetrahedron Lett., 1996, 37, 6141 CrossRefCAS.
S. Honzawa, T. Mizutani and M. Shibasaki, Tetrahedron Lett., 1999, 40, 311 CrossRefCAS; C. A. Broka and B. Ruhland, J. Org. Chem., 1992, 57, 4888 CrossRefCAS.
R. Carlini, K. Higgs, C. Older, S. Randhawa and R. Rodrigo, J. Org. Chem., 1997, 62, 2330 CrossRefCAS.
O. Baine, G. F. Adamson, J. W. Barton, J. L. Fitch, D. R. Swayampati and H. Jeskey, J. Org. Chem., 1954, 19, 510 CrossRefCAS We thank Warren Wallace for laboratory assistance with the preparation of 9.
The acid 9 had been previously prepared by the CuSO4 catalysed reaction of 3-bromo-5-methylsalicyclic acid with NaOH: D. D. Weller and E. P. Stirchak, J. Org. Chem, 1983, 48, 4873 Search PubMed We were unable to obtain good yields of 9 by this method in spite of several attempts.
Prepared from 1-iodohepta-4,6-diene and silver nitrite in 68%yield;see E. Vedejs, T. H. Eberlein and R. G. Wilde, J. Org. Chem., 1988, 53, 2220 Search PubMed for the synthesis of the iodide.
R. Carlini, C-L. Fang, D. Herrington, K. Higgs, R. Rodrigo and N. Taylor, Aust. J. Chem., 1997, 50, 271 CrossRefCAS.
A. P. Kozikowski and C-S. Li, J. Org. Chem., 1987, 52, 3541 CrossRefCAS and pertinent references therein.
D. P. Curran, J. Am. Chem. Soc., 1983, 105, 5826 CrossRefCAS.
R. Carlini, K. Higgs, R. Rodrigo and N. Taylor, Chem. Commun., 1998, 65 RSC.