A Biphenanthrene and a Phenanthro[4,3-b]furan from the Orchid Bulbophyllum vaginatum

Two minor metabolites of the whole plant of Bulbophyllum vaginatum collected in Singapore were identified as the biphenanthrene 1 and the phenanthro[4,3-b]furan derivative 2. Structure determinations were performed using a combination of 1D and 2D NMR techniques.