New dibenzofurans and depsides from the lichen Bunodophoron patagonicum.

Abstract

The lichen Bunodophoron patagonicum has been shown to contain five new dibenzofurans: ascomatic acid (I, R1 = H, R2, R3 = Me) and its Me ester (I, R1-R3 = Me); 7-O-methylnorascomatic acid (I, R1 = R2 = H, R3 = Me) and its Me ester (I, R1 = R3 = Me, R2 = H); and norascomatic acid (I, R1-R3 = H). The lichen also contains two new depsides: patagonic acid [II, R4 = Me, R5 = CH2CO(CH2)6Me] and isopatagonic acid [II, R4 = CH2CO(CH2)6Me, R5 = Me]. The structure of all new natural products was confirmed by total synthesis.