Apparicine-derived alkaloids

Tabernaemontana divaricata (double flower variety) provided an unusual minor alkaloid, voaharine (178), whose structure was established by X-ray analysis [137]. Voaharine is exceptional in being in all probability a tryptamine and jccologanine derived alkaloid but possessing a 3-quinolone instead of an indole chromophore. Voaharine is probably derived from voaphylline (180) (which is also present in the plant) via oxidation and rearrangement and represents the first instance of a 3-quinolone-type alkaloid obtained from Tabernaemontana. Besides these, and the known alkaloids N-methylvoaphylline (181), pachysiphine (tabersonine-P-epoxide) and apparicine, as well as two new bisindoles (vide infra), the plant also provided several new alkaloids of the aspidosperma-type including (-)-mehranine (179), voafinine (182), N-methylvoafinine (183), voafinidine (184) and voalenine (185) which were obtained in minute amounts [138-140]. 

Information on derivatives of the alkaloidal types considered so far is as follows (o) there is good evidence that the biosynthesis of strychnine (51) in Strychnos nux vomica plants follows the terpenoid pathway and it is proved that carbons x and y of (51) are derived from acetate the Wieland-Gumlich aldehyde (52) is not incorporated into strychnine by these plants b) apparicine... 

Mass spectrometry was also used to confirm the structure of burnamicine (222), which gives also fragments mainly by rupture of bonds in ring C, and another 2-acylindole alkaloid, picraphylline. Mass spectrometry aided also in the structure determination of apparicine (223), vallesamine (224), and o-acetylvallesamine. The spectrum of uleine (225) aided in the identification of naturally occurring derivatives thereof. ... 

Ajmalicine (139a) and 3-isoajmalicine (140a) were both converted to oxindole alkaloids, mitraphylline (167) and isomitraphylline (168) in Mitragyna parvifolia (Roxb.) Korth. (Rubiaceae)(S4). Feeding experiments on Vinca minor Linn. (Apocynaceae) had shown that vincamine (169) is biosynthesized via geissoschizine, stemmadenine, secodine, and tabersonine (85). Apparicine (170), which lacks one carbon atom of the tryptamine side chain, appears to be derived in Aspidosperma pyricollum Miiell. Arg. (Apocynaceae) from stemmadenine (86). 

Bennasar M-L, Zulaica E, Sole D, Roca T, Garcia-Diaz D, Alonso S (2009) Total synthesis of the bridged indole alkaloid apparicine. J Org Chem 74 8359-8368 Bremner JB, Sengpracha W (2005) A free radical cyclization approach to indolo-benzodia-zocine derivatives. Tetrahedron 61 941-953... 

Vincamine (6.271), with a skeleton different from that discussed so far, is derived via tabersonine (6.266) [190]. In another different alkaloid, apparicine (6.272), loss of one of the tryptamine side-chain carbons is apparent, and this appears to happen at a stage beyond stemmadenine (6.265) [191]. 

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