9-methoxy- and 7,9-dimethoxytariacuripyrone, natural nitro-compounds with a new basic skeleton from Aristolochia brevipes

The new natural nitro-compounds, 9-methoxytariacuripyrone [1] and 7,9-dimethoxytariacuripyrone [2], with the hitherto unknown 5-nitro-2H-benzo[h]chromen-2-one skeleton, were isolated from the rhizomes of Aristolochia brevipes in addition to compounds 3-6. The structures were determined by chemical conversions and spectroscopic methods including HMQC and HMBC nmr