Occurrence, Structure, and Biological Activity

Novel chlorin structures have been isolated from various marine organisms and their substitution patterns suggest their origin from chlorophyll a. 

The nickel containing tunichlorin (57) and its derivatives (58-60) were discovered in the tunicate Trididemnum solidum which occurs in the Carribean Sea (35). Structural elucidation was carried out by UV/Vis, CD, MS, and NMR spectroscopy on dimethyltunichlorin (58), which was prepared by etherification of the 3-hydroxymethyl group and esterification of the 17-propionic acid side chain. 

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Higher Saturated Hydroporphyrins 8.1. Occurrence, Structure, and Biological Activity... 

The ocean is a rich source of natural products, and their structural variety has inspired numerous chemists and chemical ecologists. Comprehensive reviews exist on the structure and occurrence, biosynthesis, and biological activity of marine natural products (see, e.g., [ 1-5]). An excellent book published in 2001 that deals exclusively with marine chemical ecology highlights different aspects of chemical communication and chemical defense [6]. It would be impossible to cover all aspects of chemical defense in this environment, and thus this contribution will focus on a few selected aspects that have been under intense research and discussion in recent years. 

The bis-carbazole alkaloids typically contain previously known monomeric carbazoles as structural subunits. To date, bis-carbazole alkaloids have been isolated from plants of two genera of the family Rutaceae, Murraya and Clausena, and are linked either by a methylene unit, a bisbenzylic ether bridge, a bond joining one aromatic portion directly to an annotated dihydropyran unit, or by a biaryl bond. Many reviews have appeared on the monomeric carbazole alkaloids. However, in these articles only a few bis-carbazole alkaloids were listed (3,5-7). For the first time, in 1992, Furukawa et al. compiled all of the bis-carbazole alkaloids that were known to the end of 1992 (158). Taster and Bringmann summarized to the end of 2001, the occurrence, stereochemistry, synthesis, and biological activity of the bis-carbazoles linked through a biaryl bond (159). We compiled to the mid of 2002, the occurrence, stereochemistry, synthesis, and the biological activity of all classes of bis-carbazoles (8). In this section, we cover the total syntheses of the natural bis-carbazole alkaloids reported since 1990. 

ABSTRACT Numerous molecules containing a biaryl unit have been found in Nature. Many of them exhibit a variety of biological actions. In this review, we will focus only on natural bridged biaryls that possess axial chirality and exhibit antimitotic activities. Thus, we will first present the occurrence and structure of three families of natural compounds that display these particular structural and biological features the allocolchicinoids, steganes and rhazinilam-type compounds. We will then describe the semi-synthetic and synthetic approaches to biaryls belonging to these three series. Their interaction with tubulin, a heterodimeric protein that is critical for the formation of microtubules and consequently of the mitotic spindle, will be discussed. 

This review, after covering general aspects concerning the structure, occurrence and biological activity in the allocolchicinoid, stegane and rhazinilam series, will focus on recent work related to the semi-synthesis and total synthesis of these molecules together with structure-activity relationships. 

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). 

Due to the increasing attraction and rapid extension in this field the Erythrina alkaloids have been regularly reviewed concerning occurrence, structure, analytic and spectral properties, biosynthesis, total synthesis, and biological activities covering the literature up to 1997. The most important reviews are cited in Refs. 18-24. 

The biosynthesis, occurrence, and biological activities of piperidine alkaloids arising from lysine have been studied Punica granatum. Piper species, and Lobelia inflata). The isolation process, chromatographic purification/analysis, and structure elucidation of the significant alkaloids are discussed. 

Given the frequent occurrence of the indole core structure in biologically active substances and natural products. Rueping et al. have developed a highly... 

The general interest in the pteridines is due to their widespread occurrence in both the animal and plant kingdoms, implying potential biological activity and drug-type properties in structural analogues. 

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