Sarpagine-type indole alkaloids

One additional yohimbane 93 and five new sarpagine-type indole alkaloids, for example, 94, are found in the radix of Gelsemium sempervirens Ait. f. <2005TL5857>. 

As demonstrated above, comparison of the 13C-NMR spectra is a secure method for determination of the stereochemistry of the ethylidene chain in the sarpagine-type indole alkaloids when pairs of isomers at C-19 are available. Alternatively, the differential NOE technique is also an efficient method for this purpose. 

Sarpagine-type indole alkaloids have a structural feature bonding the C-5 and C-16 positions in the Corynanthe-typ monoterpenoid indole alkaloids. This type of compound is distributed not only in Gelsemium plants, but also in many genera in the family of Apocynaceae, Rubiaceae, and Loganiaceae. As shown in Table I, sfac sarpagine-type alkaloids 1-3, 5, 8, and 9 have been isolated from the Gelsemium plants. 

Humantenine-type alkaloids are the oxindole derivatives of the C/D ring-cleaved sarpagine-type indole alkaloids. Only three humantenine-type JVa-methoxyoxindole alkaloids, i.e., humantenine (86) (7,49-52), humanteni-rine (87) (49,51,52), and rankinidine (88) (52), had been reported up to... 

By employing the newly developed methods, humantenirine (87), a representative humantenine-type Gelsemium alkaloid, was synthesized from a sarpagine-type indole alkaloid (63). The oxindole derivative 103 prepared from gardnerine (28) was used for further transformation (Scheme 20). 

Table 2 Sarpagine-type indole alkaloids—cont d...

Illustrated in Tables 2—6 are the structures of the recently isolated (since year 2000) sarpagine-related indole alkaloids, along with their key physicochemical properties. They have been classified into sarpagine-type, macroline-type, ajmaline-type, sarpagine/macroline oxindoles, and bisindole alkaloids containing sarpagine/macroHne monomeric units for ease of illustration. 

Enzymatic Formation of Monoterpenoid Indole Alkaloids 2.1 Heteroyohimbine /Sarpagine /Ajmaline Type Alkaloids... 

Biogenetically, the humantenine-type oxindole alkaloids would be generated from the sarpagine-type compounds such as 19(Z)-anhydrovobasinediol (6) through p-oxidation of the indole portion and subsequent rearrangement to the oxindoles (Fig. 13). 

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