Ervatamine alkaloids

The configurations of the stereo centers for ervatamine alkaloids were established by chemical correlations (189, 190) with the vobasine series and supported further by an X-ray diffraction study of 44 (191). 

In 1971, Knox and Stobbe isolated, from T. orientalis (Ervatamia orientalis), ervatamine (44, C21H26N203, MP 98°C), 20-epi-ervatamine (45, C2IH26N203, MP 187°C, [a]D —22°), and 19,20-dehydroervatamine (50, C21H24N203, MP 200°C, [a]D +53°C), which were the first examples of a novel class of 2-acylindole alkaloids, lacking the most common indolylethylamine moiety (151). 

Aconitine and related diterpene alkaloids (A) veratridine, zygadenine, and related steroidal alkaloids (A) ajmaline, vincamine, ervatamine, and other indole alkaloids (AA) dicentrine and other aporphine alkaloids (AA) gonyautoxin (AA) paspalitrem and related indoles (AA) phalloidin (AA) quinidine and related quinoline alkaloids (AA) sparteine and related quinolizidine alkaloids (AA) saxitoxin (AA) strychnine (AA) tetrodotoxin (AA)... 

The seeds of Centaurea moschata contain alkaloids with a 5-hydroxyindole structural unit, namely moschamine 87, moschamindole 88, and moschaminindolol 89 <1997MI189>. Ervatamine-type indole alkaloids, for example, 6-oxo-16,20-episilicine 90, 16,20-episilicine, and 6,16-didehydro-20-episilicine have been isolated from Ervatamia officinalis <2005HCA2537>. 

Cells carefully control the homeostasis of their ion concentrations by the action of ion channels (Na, K , Ca " channels) and throu Na, K -ATPase and Ca -ATPase. These channels and pumps are involved in signal transduction, active transport processes, and neuronal and neuromuscular signaling. Inhibition of transport processes (ion channels, carriers) is achieved by (Table IV) acronycine, ervatamine, harmaline, quinine, reserpine, colchicine, nitidine, salsolinol, sanguinarine, stepholidine, caffeine, sparteine, monocrotaline, steroidal alkaloids, aconitine, capsaicine, cassaine, maitoxin, ochratoxin, palytoxin, pumiliotoxin, saxitoxin, sole-nopsine, and tetrodotoxin. 

Bennasar, M. L., Vidal, B., Bosch, J. Total Synthesis of Indole Alkaloids of the Ervatamine Group. A Biomimetic Approach. J. Org. Chem. 1996, 61, 1916-1917. 

Oxosilicine (163), a new alkaloid of a Malagasy plant, Hazunta silicicola Pichon, has an a-acylindole structure related to 20-epiervatamine. Although details of the isolation are still not available, the synthesis of (163) has already been announced (Scheme 19) this constitutes the first total synthesis of an alkaloid of the dihydrovobasine-ervatamine group. The major feature of the route adopted is that the acylindole linkage is formed at the outset, and the bond to C-7 (indole jS -position) formed much later. This route may well be applicable to the synthesis of other 2-acylindole alkaloids. 

Quite the most intriguing new indole alkaloidal structural type to appear this year is that of ervatamine (17b) which occurs, together with 20-epi-ervatamine (17c) and 19,20-dehydroervatamine (17a), in Ervatamia orientalis.26a A description of the degradations (Scheme 5) which led to the structural assignments is included in this sub-section on the basis of a possible biogenetic relationship to alkaloids in this class (see below). 

The chemical conversion of alkaloids of the vobasine type into those of the ervatamine type can readily be effected, using a modified Polonovski reaction. This involves formation of an N-oxide and its rearrangement, using trifluoroacetic anhydride as reagent. Dregamine (65) has been converted into 20-epi-ervatamine... 

The laboratory conversion of dregamine (124) into 20-epi-ervatamine (125) suggests that alkaloids of the vobasine group may be involved in the biosynthesis of the ervatamine group of alkaloids. Support for this view comes from the report that the... 

Further extractions of the roots of Hazunta modesta have resulted in the isolation of six additional alkaloids, of which 16-demethoxycarbonyl-20-ep/-ervatamine and 6-oxosilicine belong to this group. ... 

Applying the Potier-Polonovski reaction, vobasine-type indole alkaloids such as vobasine, dregamine, and tabernaemontanine could be transformed into dehydroervatamine, 20-epiervatamine, and ervatamine, respectively (70). 

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