Placodiolic acid

Fig. 48. A Didymic acid, GE. Bar lOjim. B Isousnic acid, GE. Bar lOOiLim. C Isousnic acid. An. Bar 100 tm. D Placodiolic acid, GE. Bar 100 jim...

Deriv (-)-Diacetylplacodiolic acid, prisms (MeOH), mp 184-185 °C, [a]g - 229 (CHCI3, c 0.524), from (-)-placodiolic acid with AC2O-H2SO,... 

Connolly JD, Freer AA, Huneck S (1984a) Crystal structure of (-)-placodiolic acid, a dibenzofuran derivative from the hchen Rhizoplaca chrysoleuca. Phytochemistry 23 702... 

Two new usnic acid derivatives have recently been described. (—)-Placodiolic acid (475) was isolated from Lecanora rubina by Huneck (772). The structure was established spectroscopically (u.v., m.s. and H-n.m.r.)... 

Scheme 61. Conversion of (— )-placodiolic acid to ( —)-isousnic acid...

Chemistry of some Yellow Acarospora Species. Lichenologist 12, 239 (1980). Huneck, S., J. A. Akinniyi, A. F. Cameron, J. D. Connolly, and A. G. Mulholland The Absolute Configurations of ( + )-Usnic and ( + )-Isousnic Acid. X-Ray Analyses of the (— )-a-Phenylethylamine Derivative of ( + )-Usnic Acid and of ( —)-Pseudo-placodiolic Acid, A New Dibenzofuran, from the Lichen Rhizoplaca chrysoleuca. Tetrahedron Letters 22, 351 (1981). 

The structure of (—)-placodiolic acid from Lecanora mbina (Vill.) Ach. has been established as (—)-isousnic acid isomethoxide (51a). 

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