Of the porphyrinoid structures occurring in nature the most important and most widespread are the red blood pigment heme (1), the green pigment of plant photosynthesis chlorophyll a (2), the bacterial photo synthetic pigment bacteriochlorophyll a (3), and the "antipernicious" red pigment vitamin BJ2 (4). The basic function of these cofactors are determined by the incorporation of the different metal ions into the macrotetracycles. The different oxidation levels of the macrocyclic ligand system regulate the fine tuning of these functions. The final adaptation of the cofactors to their special molecular environments in the cell compartments is effected by variation of the substitution patterns of the chromophores. HCO,C 3 CO,Phytyl 2 Heme Chlorophyll a CONH, CONH, ~ H,NOC 1 , CONH, /I(Y N~ 3 4 Bacteriochlorophyll a Vitamin B" HO References, pp. 42-51 Naturally Occurring Cyclic Tetrapyrroles 3 Until the mid-1970s the four classic cyclic tetrapyrrolic structures with their porphyrin, chi orin, bacteriochlorin, and corrin skeletons were almost the only representatives in the class of porphyrinoid natural products (1-10). Although other partially reduced porphyrins were conceivable, none of these partially saturated porphyrinoid structures had hitherto been found in nature.

Klappentext

The first contribution of this book gives an overview on naturally occuring cycling tetrapyrroles. The article describes the four classic tetrapyrrolic structures with their porphyrin, chlorin, bacteriochlorin and corrin skeletons and also novel, interesting structures with unusual biological activities. This review mainly focuses on the occurrence, structure and biological function as well as biosynthesis and aspects of synthesis. The second article deals with the anticancer compound taxol and its semisynthetic analog docetaxel (Taxotere). Taxol was originally isolated in the late 1960 s on the basis of its cytotoxity and antileukemic activity, its structure was published in 1971 in a paper that has been cited 1000 times since this publication. The review focuses primarily on the interesting and novel chemistry of taxol that has been discovered over the last eight years.

Inhalt
Naturally Occurring Cyclic Tetrapyrroles.- 1. Introduction.- 2. Classification.- 3. General Aspects of Cyclic Tetrapyrrole Biosynthesis.- 4. Porphyrins.- 5. Chlorins.- 6. Bacteriochlorins.- 7. Isobacteriochlorins.- 8. Higher Saturated Hydroporphyrins.- 9. Corrins.- Acknowledgments.- References.- The Chemistry of Taxol and Related Taxoids.- 1. Introduction.- 2. A-Ring Chemistry.- 3. B-Ring Chemistry.- 4. C-Ring Chemistry.- 5. D-Ring Chemistry.- 6. Rearrangements and Related Reactions.- 7. The Side Chain.- 8. Synthesis of Taxol and Taxol Side Chain Analogs from Baccatin III.- 9. Taxol Metabolites.- 10. Taxol Analogs and Prodrugs.- 11. Labeled Taxol Analogs.- 12. The Synthesis of Taxol and Taxol Analogs from Precursors other than Baccatin III.- 13. The Synthesis of Simplified and Unusual Taxol Analogs.- 14. The Synthesis of Taxol.- 15. The Interaction of Taxol with Tubulin.- Addendum.- Acknowledgements.- References.- Author Index.