Indolizidine alkaloids from Elaeocarpus

Indolizidine alkaloids from the plant groups Ipomea, e.g. ipalbidine (191a) (70T3829), Tylophora, e.g. tylophorine (213) (B-67MI30800) and Elaeocarpus, e.g. elaeocarpine (200a) (B-73MI30800) have been studied to a greater extent. 

Simple indolizidine alkaloids from the genus Elaeocarpus were surveyed in Volumes 28 and 44 of this treatise (1,2). The latter survey highlighted a communication on the synthesis of (+ )-elaeokanines A (307) and C (308) by Koizumi and co-workers (289) that has since been published with full experimental details (290). 

Two pentacyclic bases containing tryptamine units and a second nitrogen have been reported. The structure (18) for nitrarine, an optically inactive base from Nitraria schoberi, relies at the moment on spectral measurements. Elaeocarpidine, an optically inactive alkaloid which co-occurs with indolizidine alkaloids in Elaeocarpus densijiorus, has been examined fully and proved to have the structure (19). Central to the structure determination was a hydro-genolysis, in acid solution, of the N-C-N system to give dihydroelaeocarpidine... 

The following post-1986 reviews in this treatise provide the antecedents for several sections of this chapter. The important contribution of Takahata and Momose in Volume 44, entitled "Simple Indolizidine Alkaloids", covered the period 1986 to 1992, but dealt only with Elaeocarpus alkaloids, slaframine, polyhydroxylated indoUzidines such as swainsonine and castanospermine, and alkdoids fiiom ants and amphibians (2). This partial update is especially valuable as a guide to published totd syntheses of these alkaloids. Materi of relevance is also to be found in a number of reviews on more specialized topics. Numata and Ibuka reviewed the chemistry of alkaloids from ants and other insects in Volume 31... 

A new family of indolizidine alkaloids has been isolated from three species of the Elaeocarpus genus (fam. Elaeocarpaceae). E. polydactylus Schltr., a large, spreading tree, indigenous to New Guinea, contains three interrelated alkaloids of... 

A new series of indolizidine alkaloids has been isolated from the leaves of Elaeocarpus kaniensis Schltr., a rain-forest tree which flourishes in New Guinea.8 The structures of six of these alkaloids have been assigned on the basis of detailed spectroscopic studies, consideration of their biosynthesis and their presumed structural relationships with other alkaloids of the Elaeocarpus genus.9... 

Indollzidine alkaloids. A group of alkaloids from various classes based on the bicyclic ring system of in-dolizidine. They differ in structure, biogenesis, and occurrence thus, the indolizidine ring system has very little value as a characterizing structural. The I. a. include the pumiliotoxins (Dendrobates alkaloids), poly hydroxy alkaloids such as swainsonineand cas-tanospermine, Elaeocarpus alkaloids, Securinega alkaloids, Tylophora alkaloids, and the Ipom(o)ea alkaloids. 

Although the indolizine nucleus appears not to occur naturally, its perhydro derivative, commonly named indolizidine, is the alkaloid 8-coniceine, and this nucleus is to be found in several groups of alkaloids including those from the plant groups Ipomoea, Elaeocarpus, Tylophora, Amaryllidaceae, and Orchidaceae. Since the chemistry of these alkaloids has been reviewed regularly,1 only selected examples will be taken from the natural products field. 

No alkaloids had been obtained from the family Elaeocarpaceae until a CSIRO group began a study of certain Elaeocarpus spp. from New Guinea. Amongst a score or so of alkaloids they isolated was a new indole base, elaeocarpidine (7), but most of the others had novel indolizidine structures exemplified by elaeokanine C (8), elaeokanidine A (9) and elaeocarpine (10) [28]. 

---