A Synthesis of the Lichen Diphenyl Ether Epiphorellic Acid 1

Abstract

The lichen diphenyl ether epiphorellic acid 1 [6-hydroxy-3-(5′-hydroxy-2′-methoxycarbonyl- 3′-pentylphenoxy)-4-methoxy-2-pentylbenzoic acid] (5) has been prepared by unambiguous synthesis. The synthesis employed a biomimetic -type approach which envolved a Smiles rearrangement of a precursor meta- depside in the key step.

New meta -depsidones and diphenyl ethers from the lichen Parmotrema tsavoense (Krog & Swinscow) Krog & Swinscow, Parmeliaceae

“…Synthetically, the para-depside, methyl prasinate could be converted into the isomeric diphenyl ether in a yield of 32% via an intramolecular Smiles rearrangement by treatment of the former with dimethyl sulfoxide in the presence of anhydrous potassium carbonate at 75−76 °C for 22 h. 22 Similarly, the treatment of the depside, benzyl 3-(4′-benzyloxy-2′-hydroxy-6′-propylbenzoyloxy)-6-hydroxy-4-methoxy-2-pentylbenzoate with a solution of anhydrous potassium carbonate in dimethyl sulfoxide at 70 °C for 48 h effected the Smiles rearrangement to…”

Disorder in methyl 4-(3,5-dimethoxy-2-methylphenoxy)-2,6-dihydroxy-3-iodo-5-methylbenzoate

“…Data collection: SMART (Siemens, 1996); cell re®nement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to re®ne structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 1990). The diphenyl ethers could be prepared readily by the convertion of p-depsides which are produced from a wide variety of metabolites of lichen (Elix et al, 1978) and by synthesis (Elix & Jenie, 1989;Chantrapromma et al, 1998) via an intramolecular Smiles rearrangement (Elix et al, 1984). Suitable reaction conditions for an intramolecular Smiles rearrangement of the prepared depsides have also been studied extensively (Elix & Jenie, 1989;Elix et al, 1990).…”

2-(4-Acetyl-3,5-dihydroxy-2-methylphenoxy)-4,6-dimethoxy-3-methylbenzoic acid

“…A number of depsides have been prepared as intermediate compounds in the synthesis of corresponding diphenyl ether molecules. Suitable reaction conditions for an intramolecular Smiles rearrangement of the prepared depsides have also been studied extensively (Elix & Jenie, 1989;Elix et al, 1990). The crystal structure determination of the title compound, (I), was undertaken as part of structural studies on diphenyl ether derivatives.…”