Serpentine structural formulas

Rauwolfia serpentina Benth. is the source of several related alkaloids. Ajmaline, ajmalicine, ajmalinine, serpentine, serpentinine, isoajmaline, and neoajmaline have been identified. Ajmaline and serpentine have been given provisional structural formulas (81, 82). Other members of the Apocynaceae yield alkaloids of similar properties. Although Rauwolfia preparations have been used in Ayurvedic medicine for hypertension, there appear no indications that they have been used in clinical cardiac arrhythmia. Yet, incomplete pharmacologic studies indicate properties for these alkaloids which should prompt additional studies toward their possible use in auricular fibrillation. 

Fig. 2.13 The 1 1 and 2 1 layer arrangements in the sheet structure minerals and the (010) view of the structures of the serpentine, clay, talc, pyrophyllite, mica, and chlorite minerals. X = layer charge per formula unit. [From Bailey (1980), Fig 1.1, p. 3 Fig 1.2, p. 6.1...

Heteroyohimbine alkaloids. A group of indole alkaloids with the yohimbine structure but with an oxygen function in ring E (see formula under yohimbine) H. occur mainly in the Apocynaceae. Typical examples are ajmalicine (raubasine), 19-epi-ajmalicine, tetrahydroalstonine, rauniticine (all with the 3o-con-figuration), as well as serpentine and alstonine with an aromatic ring C. 

FIGURE 2 [010] view of structures of major clay mineral groups. 1 1 and 2 1 T 0 layers are represented by the primary units in serpentine-kaolin and talc-pyrophyllite, respectively. The c-sin (5 distance is the basal (001) c-axis d-spacing. Layer eharge per formula unit = X. (Reproduced with the permission of the Mineralogical Society of Great Britain and Ireland from Ref. 13.)... 

Ring Oxygen Heterocycles. The isomeric bases ajmalicine and tetrahydroalstonine (along with their tetradehydro compounds, serpentine and alstonine) are the most well known members of this group and had to be closely related to the seco compounds since upon dehydrogenation they yielded alstyrine. From the empirical formulae, absence of an isolated double bond, presence of C-methyl and a /3-oxyacrylic ester moiety (saponification and ultraviolet absorption spectra) the structures of ajmalicine and alstonine were derived. The stereochemical problems were not completely resolved until the total synthesis of ajmalicine was accomplished. 

If the cation in a dioctahedral sheet is trivalent aluminum the mineral is kaoli-nite with the formula AI2 Si2 O5 (OH)4 Fig. 3. If the cation in a trioctahedral sheet is magnesium, the resulting mineral is serpentine, Mg3 Si2 O5 (013)4. Because of the structural mismatch between the Mg octahedral layer and the Si tetrahedral layer these minerals are often tubular or fibrous, and in many cases carcinogenic if inhaled in substantial quantities. 

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