Simple indolizidine alkaloids

Takahata H and Momose T (1993) Simple indolizidine alkaloids. The Alkaloids, Chemistry and Pharmacology (ed Cordell GA) Vol 44. Academic, San Diego, pp 189-256. 

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... 

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). 

An indolizidine alkaloid isolated from the rhizomes of Polygonatum sibiricum (Liliaceae) also has some unusual features 311). The unnamed alkaloid, for which the structure 326 has been proposed on the basis of good spectroscopic data (IR, UV, MS H, C and HETCOR NMR), is the first 5,6,7,8-tetrahydroindolizine (cyclohexa[a]pyrrole) to have been found as a natural product. In addition, the ethoxymethyl substituent is unique, at least among the natural indolizidines. It should also be pointed out that simple indolizidine alkaloids have never before been isolated from liliaceous species. Although the structure 326 appears to be reasonable in the light of the spectroscopic evidence, judgement should perhaps be reserved until it can be confirmed independently. 

This route was used in a synthesis of the simple indolizidine alkaloid 8-coniceine (41). AAAcylimines are only transient intermediates in these Diels-Alder reactions and are not usually detected. However, Lasne et al.,i7 using a flash vacuum pyrolysis (FVP) technique, have generated neutral AAacylimines and showed that they are indeed involved in Diels-Alder cycloadditions. 

Fig. 30.13. Simple indolizidine alkaloids from amphibians (modified from Howard and Michael, 1986 used with permission of the copyright owner. Academic Press, Orlando, FL).

The author, Joseph P. Michael from the Molecular Sciences Institute at the University of the Witwatersrand in South Africa, had already written two of the three previous reviews on this topic for The Alkaloids. In Chapter 3 of Volume 28, published in 1986, Arthur S. Howard and Joseph P. Michael presented the first fiaU coverage of Simple Indolizidine and Quinohzidine Alkaloids within this series. In Chapter 3 of Volume 44, pubhshed in 1993, Hiroki Takahata and Takefumi Momose gave an update on Simple Indolizidine Alkaloids . In Chapter 1 of Volume 46, published in 1995, David J. Robins described the Biosynthesis of Pyrro-lizidine and Quinolizidine Alkaloids . The last overview on Simple Indohzidine and Quinolizidine Alkaloids in this series was compiled again by Joseph P. Michael and pubhshed in 2001 as Chapter 2 of Volume 55. Thus, there could have been no better expert for the present review which is covering the tremendous development in this field from the middle of 1999 tiU the end of 2013. This view of the editor has been confirmed by Jo Michael s remarkably extensive compilation of exceptional quahty. 

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