Ebumane alkaloids

Aminomcthyl derivatives are usually described as unstable intermediates affording more stable C-aminomethyl products by deaminomethylation (sec above). However, the synthesis of ebumane alkaloids involves as a key step the formation of a mcthylol derivative of the a-dicarboxyester 455 (Fig. 173), which then leads to the tcu-ahydro-pyranc ring 456 by intramolecular 0-aminoalkylation reaction with the immonium ion present in the molecule. 

Gan C-Y, Low YY, Etoh T, Hayashi M, Kraniyama K, Kam TS. Leuconiocines A-G and ( )-ebumamaline, biologically active strychnan and ebuman alkaloids from Leu-conotis. Prod 2009 72(12) 2098-103. 

No vincosan alkaloids were found in Tabemaemontana species, and only a few examples of vallesiachotaman, strychnan, aspidospermatan ebuman, and tacaman alkaloids have been detected. 

The great number of different alkaloids found in Tabemaemontana precludes a discussion of the structure elucidation and chemistry of all of them. To keep the treatment concise, a major compromise was necessary. The alkaloids that have been reported in previous volumes of this treatise (as indicated in Table I) and their trivial modification will not be mentioned here. This compromise eliminates from the discussion well-established and long-known alkaloids that were isolated not only from Tabemaemontana but also from other genera. Moreover, the plumeran alkaloids isolated up to 1976 and ebuman-type and bisindole alkaloids isolated up to 1979 are covered in Volumes XVII and XX. The main efforts of this chapter will be focused on more recently isolated compounds, some of which are structurally and biogenetically relevant and have been found only in plants of the genus Tabemaemontana. 

Gan C-Y, Low Y-Y, Robinson WT, Komiyama K, Kam T-S. Aspidospermatan-aspidospermatan and ebumane-sarpagine bisindole alkaloids from Leuconotis. Phytochemistry 2010 71(2010) 1365-70. 

LeuconoUne (141) (Figure 22), the first example of ebuman—vobasine-type bisindole alkaloids, was isolated from the stem bark of Malayan... 

Two new indole alkaloids, bisnicalaterine D (1), consisting of an ebumane and a corynanthe type of skeletons, and nicalaterine A (2) were isolated from the bark of Hunteria zeylanica. Their structures were elucidated by various spectroscopic data such as NMR and CD spectra. A series of bisnicalaterines and nicalaterine A showed potent anti-plasmodial activity against P. falciparum 3D7 [28]. 

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