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Issue 16, 1993
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cis-Dihydrocatechols as precursors to highly oxygenated troponoids. Part 2. Regiocontrolled syntheses of stipitatic and puberulic acids

Abstract

Stipitatic and puberulic acids, 1 and 2 respectively, have both been prepared in a fully regiocontrolled manner using commercially available cis-1,2-dihydrocatechol 3 as the common starting material. In the case of the former acid, compound 3 was converted over six simple steps into the ester 12. Oxidation of this latter compound produced the σ-homo-o-benzoquinone 13 which acted as a Michael acceptor when treated with methoxide ion and the resulting conjugate could be trapped with acetic anhydride to give the acetoxy enone 14. Base-promoted ring-expansion of 14 then afforded the troponoid 15, the acquisition of which constitutes a formal total synthesis of stipitatic acid. Attempts to develop an analogous synthesis of puberulic acid failed. However, a successful synthesis of this natural product was achieved by elaborating the tetra-oxygenated compound 25, which is readily prepared from the diol 3, to the bromotropolone 28. Palladium-catalysed methoxycarbonylation of this latter compound, followed by hydrolysis of the intermediate ester afforded the acid 29, the structure of which was established by X-ray methods. Two-fold demethylation of compound 29 then delivered puberulic acid 2.

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J. Chem. Soc., Perkin Trans. 1, 1993, 1913-1920
Article type
Paper

cis-Dihydrocatechols as precursors to highly oxygenated troponoids. Part 2. Regiocontrolled syntheses of stipitatic and puberulic acids

M. G. Banwell, M. P. Collis, M. F. Mackay and S. L. Richards, J. Chem. Soc., Perkin Trans. 1, 1993, 1913
DOI: 10.1039/P19930001913

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