5-O-Methylhiascic acid, a new tridepside from Australian lichens

Abstract

The tridepside 5-O-methylhiascic acid (7) has been isolated from an unnamed crustose lichen and detected in Parmelia horrescens, Parmelia pseudofatiscens and Parmelia dissecta. The structure of this compound followed from the spectroscopic data and has been confirmed by the total synthesis of both 5-O-methylhiascic acid and the isomer, 4-O- methylhiascic acid (6). Diploschistesic acid (21) and 5- hydroxylecanoric acid (23) were also synthesized.