Biomimetic chemistry natural product synthesis

Despite the increasing power of science over our biological destinies, however, it is safe to say that the distinction between art and nature is still with us today. The well-known chemist and writer Roald Hoffmann has emphasized that the dichotomy lives on in modern chemistry, when chemists refer to natural product synthesis and speak of biomimetic... 

Ekkehard Winterfeldt was bom in Danzig in 1932. He received his degrees from the Technische Universitat Braunschweig, where he finished his dissertation under the direction of Prof. F. Bohlmann in 1958. He moved to the Technische Universitat Berlin, obtained his habilitation in 1962 and in 1967 he was promoted to associate professor. Since 1970 he has held his current position as Professor of Oiganic Chemistry at the Universitat Hannover. His research is devoted to natural product synthesis with emphasis on biomimetic approaches and stereoselective transformations. 

The oxidative activation of arenes is a powerful and versatile synthetic tactic that enables dearomatization to give useful synthons. Central to this chemistry are hydroxylated arenes or arenols, the phenolic functions of which can be exploited to facilitate the dearomatizing process by two-electron oxidation. Suitably substituted arenols can hence be converted, with the help of oxygen- or carbon-based nucleophiles, into ortho-quinone monoketals and ortho-quinols. These 6-oxocyclohexa-2,4-dienones are ideally functionalized for the construction of many complex and polyoxygenated natural product architectures. Today, the inherent and multiple reactivity of arenol-derived ortho-quinone monoketals and ortho-quinols species is finding numerous and, in many cases, biomimetic applications in modern organic synthesis. 

With this brief overview of the enzymatic conversion of squalene to lanosterol, we can now envisage strategies for the total synthesis of polycyclic natural products in the laboratory. This field of bioorganic chemistry has been called biomimetic polyene cyclizations by Johnson. 

The mew-substituted porphyrins, though not naturally occurring, are widely preferred candidates in various fields such as biomimetic models, materials chemistry, photodynamic therapy, catalysis, electron transfer, etc. [180]. The synthesis of these derivatives is much simpler compared to their -substituted counterparts. Rothenmund et al. prepared the first mew-tetramethyl porphyrin derivative by the condensation of acetaldehyde and pyrrole [181]. A side-product chlorin , a porphyrin-related macrocycle, which is largely, but not completely aromatic in nature, is usually formed in this reaction. However, chlorins can be easily oxidized to form the corresponding porphyrins. Alder et al. developed a new method in the 1960s to synthesize tetraphenyl derivatives by the condensation reaction of benzaldehyde and pyrrole in the presence of acidic solvents under refluxing... 

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