Melodinus suaveolens alkaloid from

Vincoline (128) has recently been found in Melodinus suaveolens (95) and M. morsei (38), and the alkaloids 129 and 130, from Catharanthus ovalis (63,139), whose structures were elucidated earlier (1), are now referred to as kitraline (195) and kitramine (19/ ), respectively (63). 

In suaveolenine (134), an alkaloid from the trunk of Melodinus suaveolens, oxidation of the vincadifformine ring system has occurred between C-7 and C-21. The structure and stereochemistry of suaveolenine, also established by X-ray crystallography, show that it is very closely related structurally, but not stereochemically, to vincoline, with which it occurs in M. suaveolens (95). 

Melosuavines D—F (71—73) (Figure 13) were isolated from the twigs and leaves of Melodinus suaveolens (Apocynaceae), together with five new bisindole alkaloids, melosuavines A—C, G, and H (74—78), and two known bisindole alkaloids, tenuicausine (130) and melodinine J (128) (see Section 6, Figure 19). Melosuavine D (71) was similar to melodinine K (69) except for the presence of hydroxy groups at C-11 and C-ll positions and an... 

Finally new natural products containing the pyridine core are discovered each year. For example, three new pyrinodemins (bis-3-alkyl pyridine alkaloids), two of which showed cytotoxicity against leukemia, were isolated from a sponge, and their structures confirmed spectroscopically (13T96).A number of alkaloids, including two new quinolines (Figure 3), were isolated from Melodinus suaveolens and identified via spectroscopy and circular dichroism (13H2047). 

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