6S,8 alpha-dihydroxy-14,15-dihydrocarapin (Khayanone) from the stem bark of Khaya Senegalensis (Meliaceae): Isolation and its Crystal Structure

摘要

Khayanone was isolated from the stem bark of African mahogany, Khaya senegalensis (Meliaceae), and characterized as 6S,8 alpha-dihydroxy-14,15-dihydrocarapin on the basis of spectral analysis and single crystal X-ray diffraction study. The compound crystallizes in the tetragonal space group P4(1)2(1)2 with unit cell parameters: a = 13.2315(19)angstrom, c = 29.118(6)angstrom, Z = 8. The crystal structure has been solved by direct methods and refined to R = 0.0375 for 4552 unique reflections. The six-membered rings A and B exist in boat conformations, rings C and D in chair conformations, and the furan ring is planar. The crystal structure is stabilized by O-H center dot center dot center dot O and C-H center dot center dot center dot O interactions. This is the first report about 6S configuration of mexicanolide revealed by X-ray diffraction analysis. The configuration of oxygenated C-6 in mexicanolide-group limonoids is discussed.