Crystal Structure of 1:1 Complex of Honokiol and 1,4-Diazabicyclo[2.2.2]octane: Separation of Honokiol by Molecular Recognition

Phenomenon of molecular recognition between honokiol and 1,4-diazabicyclo[2.2.2]octane (DABCO) is discovered, and applied to separation of honokiol from extract of magnolia bark. Effects of material ratio on the yield and the purity were investigated. Honokiol (purity up to 97.3% and yield up to 83.9%) is obtained from Magnolia bark extract (honokiol 49.1%, magnolol 31.7%, others unknown 19.2%) on a favorable condition. The title complex, C₁₈H₁₈O₂·C₆H₁₂N₂, is characterized by IR and ¹HNMR and its crystal structure is determined by X-ray diffraction method. It crystallizes in monoclinic space group C2/c with a=38.860(3), b=9.205(3), c=12.588(4) Å, β=102.730(10)°, V=4392(2) ų, Z=8 and R=0.0500. Hinokiol molecules join to DABCO via O–H...N hydrogen bonds to form infinite chains. There are two symmetry independent DABCO molecules occupying in the crystal special positions of different point symmetries, C2 and Ci. Those located around the inversion center are disoredered as DABCO molecule is devoid of this symmetry element.