Crystal structure of 4'‐O‐methylalpinumisoflavone at 90K

4′‐O‐Methylalpinumisoflavone crystals which hitherto had been difficult to crystallize for X‐ray diffraction analyses have been obtained from a demethylated product of O, O‐dimethylalpinumisoflavone. The structural and conformational features of the crystal measured at 90 K are reported and compared with previously reported work of O,O‐dimethylalpinumisoflavone and 5‐O‐methyl‐4′‐O‐(3‐methyl‐but‐2‐en‐1‐yl) alpinumisoflavone. Each of these compounds is characterized by a six membered ring that is further fused to a benzopyrone isoflavone moiety resulting in a tricyclic ring system. This six membered ring shows a half‐chair conformation in all the molecules studied, with the ring in the title compound showing the least Cremer‐Pople puckering amplitude Q and shorter inter and intramolecular contacts. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)