Polycyclic Polyprenylated Acylphloroglucinols

Plants are rich in a variety of compounds. Many are secondary metabolites and include aromatic substances, most of which are phenols or their oxygen-substituted derivatives such as tannins (Hartmann 2007; Jenke-Kodama, Muller, and Dittmann 2008). Many of these compounds have antioxidant properties (see Chapter 2 on antioxidants in herbs and spices). Ethnobotanicals are important for pharmacological research and drug development, not only when plant constituents are used directly as therapeutic agents, but also as starting materials for the synthesis of drugs or as models for pharmacologically active compounds (Li and Vederas 2009). About 200 years ago, the first pharmacologically active pure compound, morphine, was produced from opium extracted from seeds pods of the poppy Papaver somniferum. This discovery showed that drugs from plants can be purified and administered in precise dosages regardless of the source or age of the material (Rousseaux and Schachter 2003; Hartmann 2007). This approach was enhanced by the discovery of penicillin (Li and Vederas 2009). With this continued trend, products from plants and natural sources (such as fungi and marine microorganisms) or analogs inspired by them have contributed greatly to the commercial drug preparations today. Examples include antibiotics (e.g., penicillin, erythromycin); the cardiac stimulant digoxin from foxglove (Digitalis purpurea); salicylic acid, a precursor of aspirin, derived from willow bark (Salix spp.); reserpine, an antipsychotic and antihypertensive drug from Rauwolfia spp.; and antimalarials such as quinine from Cinchona bark and lipid-lowering agents (e.g., lovastatin) from a fungus (Rishton 2008; Schmidt et al. 2008; Li and Vederas 2009). Also, more than 60% of cancer therapeutics on the market or in testing are based on natural products. Of 177 drugs approved worldwide for treatment of cancer, more than 70% are based on natural products or mimetics, many of which are improved with combinatorial chemistry. Cancer therapeutics from plants include paclitaxel, isolated from the Pacific yew tree; camptothecin, derived from the Chinese “happy tree” Camptotheca acuminata and used to prepare irinotecan and topotecan; and combretastatin, derived from the South African bush willow (Brower 2008). It is also estimated that about 25% of the drugs prescribed worldwide are derived from plants, and 121 such active compounds are in use (Sahoo et al. 2010). Between 2005 and 2007, 13 drugs derived from natural products were approved in the United States. More than 100 natural product-based drugs are in clinical studies (Li and Vederas 2009), and of the total 252 drugs in the World Health Organization’s (WHO) essential medicine list, 11% are exclusively of plant origin (Sahoo et al. 2010).

Herbal medicine : an introduction to its history, usage, regulation, current trends and research needs

In this article, full details regarding our total synthesis of avrainvillamide and the stephacidins are presented. After an introduction and summary of prior synthetic studies in this family of structurally complex anticancer natural products, the evolution of a final synthetic approach is described. Thus, a thorough description of three separate model studies is provided for construction of the characteristic bicyclo[2.2.2]diazaoctane ring system common to these alkaloids. The first and second approaches sought to build the core using formal Diels−Alder and vinyl radical pathways, respectively. Although these strategies failed in their primary objective, they fostered the development of a new and mechanistically intriguing method for the synthesis of indolic enamides such as those found in numerous bioactive natural products. The scope and generality of this simple method for the direct dehydrogenation of tryptophan derivatives is described. Finally, details of a third and successful route to the core of...

Enantioselective total synthesis of avrainvillamide and the stephacidins.

Syntheses and applications of functionalized bicyclo[3.2.1]octanes: thirteen years of progress.

With their fascinating biological profiles and stunningly complex molecular architectures, the polycyclic polyprenylated acylphloroglucinols (PPAPs) have long provided a fertile playing field for synthetic organic chemists. In particular, the recent advent of innovative synthetic methods and strategies together with C-C bond-forming reactions and asymmetric catalysis have revitalized this field tremendously. Consequently, PPAP targets which once seemed beyond reach have now been synthesized. This Review aims to highlight the recent achievements in the total synthesis of PPAPs, as well as notable methods developed for the construction of the bicyclo[3.3.1] core of these chemically and biologically intriguing molecules.

The chemistry of the polycyclic polyprenylated acylphloroglucinols.

Construction of Highly Functionalized Medium‐Sized Rings: Synthesis of Hyperforin and Perforatumone Model Systems

Construction of Highly Functionalized Medium-Sized Rings: Synthesis of Hyperforin and Perforatumone Model Systems.

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Construction of Highly Functionalized Medium‐Sized Rings: Synthesis of Hyperforin and Perforatumone Model Systems

Construction of Highly Functionalized Medium-Sized Rings: Synthesis of Hyperforin and Perforatumone Model Systems.