Issue 33, 2017

Total syntheses of gerberinol I and the pterophyllins 2 and 4 using the Casnati–Skattebøl reaction under different conditions

Abstract

The concise and efficient total syntheses of the naturally-occurring coumarin derivatives gerberinol I, and the pterophyllins 2 and 4, from 5-methyl-4-hydroxycoumarin as a common precursor employing different Casnati–Skattebøl reaction conditions, are reported. The synthesis of the key intermediate coumarin was achieved by the organocatalytic condensation of acetylacetone and crotonaldehyde followed by a LiCl-assisted cyclization, CuCl2-promoted aromatization and a final Et2CO3-mediated cyclization. A Casnati–Skattebøl formylation under high-temperature conditions afforded gerberinol I, whereas milder conditions resulted in an unstable 3-formyl-4-hydroxycoumarin derivative, which was subjected to a basic alumina-mediated one pot O-alkylation with chloroacetone and intramolecular aldolization to furnish pterophyllin 4. Wittig methylenation of the latter conveniently afforded pterophyllin 2.

Graphical abstract: Total syntheses of gerberinol I and the pterophyllins 2 and 4 using the Casnati–Skattebøl reaction under different conditions

Supplementary files

Article information

Article type
Paper
Submitted
16 Jun 2017
Accepted
03 Aug 2017
First published
04 Aug 2017

Org. Biomol. Chem., 2017,15, 7040-7049

Total syntheses of gerberinol I and the pterophyllins 2 and 4 using the Casnati–Skattebøl reaction under different conditions

J. L. Pergomet, A. B. J. Bracca and T. S. Kaufman, Org. Biomol. Chem., 2017, 15, 7040 DOI: 10.1039/C7OB01471F

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