Phenolic Compounds from the Lichen Lobaria orientalis

The chemical investigation of the EtOAc extract of Lobaria orientalis collected in the southwestern part of Central Vietnam led to the isolation of new β-orcinol depsidones, lobarientalones A and B (1 and 2), and diphenyl ethers, lobariethers A-E (3-7). These types of structures are often reported in different lichen species, but the absolute configuration of the stereogenic acetal center has not been defined. This is the first assessment of the (1S) absolute configuration of the stereogenic acetal center using electronic circular dichroism (ECD) spectroscopic data and by comparison with the ECD data of analogous compounds. Based on the co-occurrence of the depsidones, 1,10-di-O-methylstictic acid (8) and (1-2), and diphenyl ethers (3-7), a plausible biosynthesis route toward 1-8 is proposed.