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) alpinumiso-flavone. 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.