Indolizidine alkaloids activity

Advances in research are performed on the genus Astragalus and about 100 different species have been chemically studied imtill now [249]. The genus appears highly uniform from a chemical point of view, with three kinds of biologically active principles and three diffent groups of toxic compounds. The active constituents are saponins, flavonoids, and polysaccharides, while nitro-compoimds, indolizidine alkaloids and the seleniferous derivatives are included in the poisonous groups. 

Pyrrolizidines compounds have been produced in connection with syntheses of other types of natural products. For example, Gensler and Hu prepared the dioxopyrrolizidine ester (46) as an intermediate in the synthesis of ( + )-slaframine, an indolizidine alkaloid obtained from cultures of Rhizoctonia leguminicola. The pyrrolidone ester (47), prepared from l-glutamic acid [Eq. (14)], was optically active, but the cyclized product, formed in quantitative yield from 47, was completely racemized. The synthesis of 2-acetyl-1,3-dioxopyrrolizidine (48) was carried out by Kruger and Arndt to assist with their investigations on model compounds aimed toward the total synthesis of a-cyclopiazonic acid, the main toxic principle of Penicillium cyclopium The spectra of the product (48) obtained in 30% overall yield was typical of an intramolecularly H-bonded enolized )S-... 

Secophenanthroindolizidine alkaloids and their secophenanthroquinolizidine analogs were last surveyed in Volume 28 of this series (i). A comprehensive review on the occurrence, structural elucidation, biosynthesis, synthesis, and biological activity of the phenanthroindolizidine alkaloids, including their seco variants, was published in 1987 (57P). The topic was also included in several more general reviews on indolizidine alkaloid chemistry 14,19,563). 

Polyhydroxylated indolizidine alkaloids, due to their biological activity, have attracted considerable synthetic interest. The total synthesis of ( —)-l-qp/-swainsonine (250) from the chiral imine 238 (Scheme 58) and the parallel synthesis of (+ )-2,8,8a-tri-qp/-swainsonine (252) from the enantiomeric threose A-benzylimine 251, prepared from natural L-tartaric acid, provide further examples of the utility of tartaric acid in meeting the challenge of complex syntheses. A stereospecific 4 + 4 homologation utilizing 2-(trimethylsiloxy)furan (178) pro-... 

Castanospermine is an indolizidine alkaloid obtained from the leaves of Castanospermum australe. It is known to be a potent inhibitor of glucosidase enzymes and possesses antitumor activity. Since it is a structural analog of a simple sugar molecule (Fig. 8), it is difficult to detect. Low volatility hampers separation by gas chromatography and lack of a chromophore makes sensitive HPLC analysis with photic detection impossible. 

Polyhydroxylated Alkaloids. Polyhydroxy derivatives of pyrrolidine, piperidine, and indolizidine alkaloids have recently been isolated from plants and microorganisms. A number of these compounds have shown potent gluco-sidase inhibitory activity and have generated interest because of their ability to inhibit replication of retroviruses. 

Biological Activity of Indolizidine Alkaloids Indolizidine Alkaloids in Insects Elaeocarpaceae Alkaloids... 

The unusual indolizidine alkaloid julisporine (39) from Prosopis juliflora (Fabaceae) possessed in vitro activity against several dermatophytic fungi (Clark and Hufford, 1992). 

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