The new and unusually substituted 4,5-dioxonoraporphine 1 was isolated, among other aporphines and phenanthrene-type alkaloids, from Monocyclanthus vignei. The 13Cnmr spectra of 4,5-dioxoaporphines were studied for the first time.In the course of our phytochemical investigations on tropical plants, we studied the constituents of Monocyclanthus vignei Keay. This plant of the Annonaceae grows endemically in West Africa (1).From the basic fraction of the MeOH extract the individual alkaloids 1-12, reticuline, and N-feruloyltyramine were isolated by chromatographic procedures.The approximate concentrations of these compounds are summarized in Table 1.The structures given mainly result from spectroscopic studies. Compounds 1, 3, 9, and possibly, 10-12 represent new genuine natural products.Compounds 1 and 2 show electron spectra and eims typical for 4,5-dioxoaporphines (9). The eims of 2 exhibits significant ions at [M + 14]+ and [M -14]+ caused by intermolecular methyl transfer. The position of the only hydroxy substituent in 1 at C-2 is indicated by the «-coupling between H-l and H-3.Because no BC-nmr data of 4,5-dioxoaporphines have yet been published, we studied the BC nmr of 1 and 2. In this study are included their methylation products 13 and 14 and the dioxoaporphines 15 and 16, available to us from other sources (10,11). Due to poor solubility in the usual solvents, all spectra were run in pyridinet/5. The assignments presented in Table 2 are based on heteronuclear lJ-and 2,iJ-COSY measurements.
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