Issue 9, 2017, Issue in Progress

First total synthesis of the only known 2-isopropyliden-2H-benzofuran-3-one isolated from V. luetzelburgii

Abstract

The first total synthesis of 5-(1-hydroxy-1-ethyl)-2-isopropyliden-2H-benzofuran-3-one, is reported in its racemic and in one of its optically active [(S)-(−)] forms. This heterocycle, isolated from Verbesina luetzelburgii, is the only known 2-isopropyliden-2H-benzofuran-3-one produced by species of Verbesina. The sequence took place in eight steps and 19% overall yield (up to 33% for the chiral form), from 4′-hydroxyacetophenone. It entailed carbonyl group protection as the 1,3-dioxolane and a phenol ortho formylation, followed by a Williamson etherification with chloroacetone and an organocatalytic cross-aldolization, to afford a 2-acetyl-2,3-dihydrobenzofuran-3-ol intermediate. The latter underwent a methyl Grignard addition to the carbonyl moiety, followed by selective oxidation of the benzylic alcohol and deprotection, resulting in a β-hydroxy diketone derivative. A MsCl-assisted dehydration of the tertiary alcohol, established the isopropylidene motif, whereas the syntheses culminated by chemical or enzymatic (carrot, celeriac) selective reductions of the exocyclic carbonyl group.

Graphical abstract: First total synthesis of the only known 2-isopropyliden-2H-benzofuran-3-one isolated from V. luetzelburgii

Supplementary files

Article information

Article type
Paper
Submitted
22 Dec 2016
Accepted
06 Jan 2017
First published
17 Jan 2017
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2017,7, 5242-5250

First total synthesis of the only known 2-isopropyliden-2H-benzofuran-3-one isolated from V. luetzelburgii

J. L. Pergomet, E. L. Larghi, T. S. Kaufman and A. B. J. Bracca, RSC Adv., 2017, 7, 5242 DOI: 10.1039/C6RA28587B

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