Sponges, polyketide production

Metabolites of the phylum Porifera account for almost 50% of the natural products reported from marine invertebrates. Of the 2609 poriferan metabolites, 98% are derived from amino acid, acetogenin, or isoprenoid pathways. Isoprenoids account for 50% of all sponge metabolites, while amino acid and polyketide pathways account for 26% and 22%, respectively. A significant number of sponge metabolites appear to be derived from mixed biosynthetic pathways. Most structures reported containing carbohydrate moieties were glycosides. 

Marine natural products of the pederin class (mycalamides, onnamides, and theopederins) isolated from sponges are mixed biogenesis metabolites of polyketide synthase and nonribosomal synthase (1). In fact, biosynthesis gene clusters of this class have been cloned recently using metagenomic techniques from the marine sponge Theonella swinhoei (6). These compounds are... 

A 1.7 mm cryogenic probe is now available commercially, and this appears to provide excellent results. Dalisay et al.5,6 reported the identification of several new natural products of very low abundance from marine sponges of the genus Phorbas, including the tetrachloro polyketide muironolide A (24) and another polyketide, hemi-phorboxazol A (2). These structures were determined based on samples of only 90 pg of muironolide and... 

Figure 22) is exemplary. First characterized from beetles of the genus Paederus the subsequent characterization of closely related structures such as theopederin A (67), isolated from a marine sponge fostered the speculation of a common bacterial source for this family of polyketides. " Subsequent studies by Kellner and Piel identified a bacterium from the genus Pseudomonas as the likely source of pederin. Natural product production by symbiotic bacteria has been reviewed by Piel (Chapter 2.14). 

Kobayashi, J., Kondo, K., Ishibashi, M., Walchli, M. R., and Nakamura, T. (1993). Theone-zolide A A novel polyketide natural product from the Okinawan marine sponge Theonella sp. J. Am. Chem. Soc. 115, 6661-6665. 

Halenaquinone (134) and Halenaquinol (135) are novel pentacyclic polyketides that were isolated from tropical marine sponge [60]. They have attracted much attention because of their interesting antibiotic and cardiotonic activity. Harada61 utilized the Wieland-Miescher ketone (1) as starting material for the enantiospecific synthesis of this interesting natural product with novel pentacyclic polyketide skeleton, and this is described in "Fig (11)". 

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