Constituents of the lichen in the genus Hypogymnia. II. Vittatolic acid, a new optically active depsidone, and 2'-O-methylphysodic acid from Hypogymnia vittata (Ach.) Gas

Two new depsidones named vittatolic acid (4) and 2'-O-methylphysodic acid (5) have been isolated from the lichen Hypogymnia vittata (ACH.) GAS. along with physodic acid (1), atranorin (2), oxyphysodic acid (3), zeorin (6), and ergosterol peroxide (7). Vittatolic acid (4) is the first optically active depsidone possessing a secondary hydroxyl in the side chain. The plain structure of vittatolic acid has been clarified on the basis of physicochemical evidence and the conversion to physodic acid (1), and the absolute configuration at the asymmetric carbon in the side chain of 4 follows from the application of the Horeau's method and the Brewster's benzoate rule. The structure of 2'-O-methylphysodic acid (5) has been determined on the basis of chemical and physicochemical evidence.