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Polyketides are natural products which are biosynthesized by the polyketide pathway. This common synthetic branched rapidly, thus forming a heterogeneous group of natural substances. In addition to the polyketides from plants polyketides from marine animals such as jellyfish and sponges play an important role in modern drug research.
Polyketides are in nearly every organism like in plants, animals, bacteria and fungi.
Due to their - depending on the polyketide more or less active - antifungal, antibiotic, antitumor and antiparasitic activity the polyketides are a popular target for the pharmaceutical industry. In particular, the isolation of polyketides produced by living organisms in extreme environments (bacteria in volcanic environment, maritime creatures) yielded in interesting discoveries for drug research.
Polyketides are formed in the polyketide pathway by the composition of C-2. In the biosynthetic pathway C-2 blocks are provided as acetyl-Coenzyme A and malonyl-coenzyme A, which is known from the primary metabolism. In a similar way fatty acids are produced. This results in the precursor molecules of polyketides, n x C-2 compounds. This poly-β-keto-acyl-CoA is then converted into the polyketides by thepolyketide synthases.
One example is the biosynthesis of orsellinic acid, which could be isolated from bacteria. In this case, an intramolecular aldol condensation occurs, which leads to a ring closure. Due to the stabilisation by aromatisation the ketones tautomerize to alcohols.