Avicennol: a new pyranocoumarin from the root-bark of Zanthoxylum avicennae, and its conversion into avicennin

Abstract

A new angular pyranocoumarin, avicennol (4){6-(3-hydroxy-3-methyl-trans-but-1-enyl)-5-methoxy-2,2-dimethyl-2H-benzo[1,2-b:3,4-b′]dipyran-8-one}, has been isolated from the root-bark of Zanthoxylum avicennae(Rutaceae): the structural assignment is based on chemical and spectral evidence. A lanthanide shift reagent and the internal nuclear Overhauser effect have been used to differentiate between possible isomers. Avicennol has been converted into avicennin, previously reported from this and other species; thus the total structure of avicennin is determined. From this species avicennin may be an artefact.