Corynanthe-tryptamine alkaloids

III. Tr5 tamine-Tryptamine Type with an Additional Monoterpene Unit and Related Alkaloids rV. Corynanthe-Tryptamine Type V. Corynanthe-Corynanthe Type VI. Coryn nthe-Strychnos Type... 

This group of alkaloids has two structurally different a. The a of alkaloids found in the genus Cinchona (Ruhiaceae), such as quinine, quinidine, cinchonidine and cinchonine, is L-tryptophan. The j8 is tryptamine and the

[Pg.114]

Terpenoid Indole Alkaloids.—Crude preparations from Catharanthus roseus seedlings and from tissue cultures have been shown to be capable of synthesizing in good yield from tryptamine (110) and secologanin (111) with added co-factors, geisso-schizine (112) and ajmalicine (113), representatives of the first major class of terpenoid indole alkaloids (Corynanthe). Geissoschizine was metabolized to ajmalicine and several other unidentified alkaloids (for reviews of biosynthesis in intact plants see ref. 106). The catabolic turnover of vindoline and catharanthine in C. roseus has been studied. ... 

Researches carried out to the early part of 1966 have been comprehensively reviewed and the present account will set out from that point. In brief, the situation reached at that time was as follows. Despite their bewildering variety, three main groups of alkaloids had been recognised (a) the Corynanthe-Strychnos type, e.g. ajmalicine (1) and akuammicine (2) which possess the non-tryptamine unit (3), (b) the Aspidosperma type, e.g. vindoline (4), in which the non-tryptamine unit appears as (5), and (c) the Iboga type, e.g. catharanthine (6), having still a different arrangement of the non-tryptamine unit (7). 

Roxburghines constitute a group of octacyclic sesquimeric indole alkaloids conceptually derived from two tryptamine molecules and a monoter-pene moiety of the corynanthe type. Roxburghine D (171) and the new analog, roxburghine X (172), C31H32N4O2, mp 215°C, [a]D27 -29°,... 

Feeding experiments with doubly labeled [1-3H2, l-14C]tryptamine showed that 50% of the tritium at C-l of tryptamine was lost during the formation of Cinchona alkaloids—a result which indicates that the cleavage between C-5 and N-4 in corynantheal is a stereospecific process. The ring expansion to quinoline must occur via the indolenine (178) and the recy-clization of 179 to furnish cinchonidinone (180), which was found by radiochemical dilution analysis to be a natural product in C. ledgeriana. The specific incorporation of [1 l-3H2]cinchonidinone in cinchonine and quinine and the incorporation of [ll-3H2]cinchonidine in cinchonidinone is best understood by the sequence 180 — 186 and its reversal 186 — 182, as shown in Scheme 7 (95). 

Table II tabulates the plant species which contain the complex indole alkaloids. The letters in this table correspond to the various structural types as coded in Figs. 2 and 3. Types I, II, and III are the major variations of the Cfl-Ci 0 unit which, in combination with tryptamine, formally elaborate the three significantly different groups of complex indole alkaloids Corynanthe, Iboga, and Aspidosperma. Such initial classification follows the outline set by Battersby [3, 3a) and others (2, 4, 5). The...

Rhynchophylline is composed of tryptamine and a Cjo unit with the corynanthe skeleton. Thus, the partial structure of this alkaloid somewhat resembles those of reserpine (Seaion 2.10) and yohimbine (Section 2.11), although its biological aaivities are different. Unlike reserpine, rhynchophyUine does not cause sedative activity, and, unlike yohimbine, no convulsive activity occurred when it was given to frogs and mice. In addition, unlike reserpine. 

B, Iridoid Indole Alkaloids. Most jS-carbolines are derived from tryptamine and the iridoid secologanin (D 6.1.2). In dependence on the structure of the iridoid part alkaloids of the Corynanthe-Strychnos type as well as of the Aspidosperma and Iboga types may be distinguished. The latter are formed by rearrangement of the iridoid part which is shown schematically in Fig. 259 and in detail in Fig. 261. 

When the aldehyde partner of the Pictet-Spengler reaction with tryptamine is the terpene secologanin, strictosidine is formed as an entry toward the vast monoterpene indole alkaloids [32, 33]. Hydrolysis of the glucosidic part releases the strictosidine aglycone bearing an aldehyde, while imin-ium formation and further cyclization and reduction can lead to ajmalicine (from oxocyclization) or yohimbine (from car-bocyclization). These alkaloids are referred to as from the Corynanthe type, with the monoterpene carbon skeleton unmodified. Although it misses one carbon and has a very... 

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