Khayanolides from African mahogany Khaya senegalensis (Meliaceae): A revision.
Five khayanolides (1-O-acetylkhayanolide B 1, khayanolide B 2, khayanolide E 3, 1-O-deacetylkhayanolide E 4, 6-dehydroxylkhayanolide E 5) were isolated from the stem bark of African mahogany Khaya senegalensis (Meliaceae). Their structures and absolute configurations were determined through extensive spectroscopic analyses including MS, NMR, and single-crystal X-ray diffraction experiments. The results established that two previously reported khayanolides, 1alpha-acetoxy-2beta,3alpha,6,8alpha,14beta-pentahydroxy-[4.2.1(10,30).1(1,4)]-tricyclomeliac-7-oate 6 and 1alpha,2beta,3alpha,6,8alpha,14beta-hexahydroxy-[4.2.1(10,30).1(1,4)]-tricyclomeliac-7-oate 7, were, in fact, 1-O-acetylkhayanolide B 1 and khayanolide B 2, and that the two reported phragmalin derivatives, methyl 1alpha-acetoxy-6,8alpha,14beta,30beta-tetrahydroxy-3-oxo-[3.3.1(10,2).1(1,4)]-tricyclomeliac-7-oate 8 and methyl 1alpha,6,8alpha,14beta,30beta-pentahydroxy-3-oxo-[3.3.1(10,2).1(1,4)]-tricyclomeliac-7-oate 9, were, in fact, khayanolide E 3 and 1-O-deacetylkhayanolide E 4, respectively. Based on the results from this study and consideration of the biogenetic pathway, the methyl 6-hydroxyangolensate in African mahogany K. senegalensis should have a C-6 S configuration while methyl 6-hydroxyangolensate in genuine mahogany Swietenia species should have a C-6 R configuration.
Zhang
Huaping
H
Department of Food Science and Human Nutrition, Clemson University, Clemson, 29634 SC, USA.
Tan
Junjie
J
Vanderveer
Don
D
Wang
Xi
X
Wargovich
Michael J
MJ
Chen
Feng
F
D000349:Africa; D018360:Crystallography, X-Ray; D005663:Furans / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D029582:Meliaceae / Q000737:chemistry*; D015394:Molecular Structure
D005663:Furans