Four lignans from Commiphora erlangeriana

Four new lignans, two of the polygamatin-type, named erlangerin A (1) and erlangerin B (2), and two related to podophyllotoxin, named erlangerin C (3) and erlangerin D (4), were isolated from the resin of Commiphora erlangeriana, a plant occurring in Ethiopia and Somalia. The structures of these compounds including their relative stereochemistry were elucidated on the basis of spectral evidence, chemical data, and X-ray crystallographic analysis.