Gelsedine-type alkaloids

The isolation of 19-oxo-gelsenicine (153) from the leaves of G. elegans was reported (6). The structure was established by X-ray analysis and by comparison of the CD spectra with those of gelsenicine (151). 

A novel gelsenicine-related oxindole alkaloid, named gelsemoxonine 

Reagents i. H2N-NMc2, catJIgSO, 3A-MS, EtOH CBZ-Ci. lN-NaOH/CH2Cl2 CuCl2. 

15% yield, respectively. The nitrone 197 was further oxidized with lead tetraacetate (1 eq) in CH2CI2 at — 15-0°C followed by treatment with potassium carbonate in MeOH to afford the hydroxamic acid derivative 198 in 56% yield. The hydroxamic acid derivative 198 was treated with CH2N2 in MeOH to give the Na-methoxyoxindole 199 in 65% yield. Finally, the protecting group on Ny, was removed with Zn/AcOH to yield gelsemicine 

By removal of the Nb protecting group in 203 with zinc in AcOH, the secondary amine 204 was obtained in 82% yield. This amine-epoxide 204 was then heated in dioxane at 150°C for 6 h, producing the aziridine derivative 205 in 61% yield, which corresponded to the biogenetically hypothetical key intermediate. In the NMR spectrum, the protons on the C-21 carbon 

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Gelsedine-type Alkaloids from Gelsemium Species... 

Scheme 23. A biogenetic route for the gelsedine-type alkaloids.

The isolation of gelselegine (56) and ll-methoxy-19(R )-hydroxygelselegine (57) (Table 10), new types of oxindole alkaloids having a hydroxymethyl group at the C-20 position in the gelsedine skeleton, was reported (57). 

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