13C NMR spectroscopy of D and B, D-ring seco-limonoids of Meliaceae family.

The modified limonoids isolated from the Meliaceae are too complex or obtained in too small quantities to determine their structures by chemical and spectroscopic means, including 1H NMR. One method of dealing with such problem is direct crystallographic analysis, without or having a heavy atom, which requires an able crystallographic collaborator. The determination of the structure Utilin is one example. The analysis of the 13C NMR spectral data for different compounds has been very useful for the identification of the various skeletal types of limonoids and also for the determination of the substitution pattern. Owing to the great utilities that these data could help the scientific community, who are working in the area of limonoids, we here describe the application of NMR spectroscopy in the structure elucidation of D and B, D-ring seco-limonoids and a collection of 177 compound's 13C NMR spectral data.