30: Natural Products and Biosynthesis
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For an organic chemist, a natural product is one that is produced by a living organism. This definition encompasses many compounds already discussed, such as carbohydrates, proteins, lipids, and nucleic acids, all of which play an important and primary role in metabolic reactions. However, there are other organic compounds produced naturally, some of extraordinary complexity, which are not primary metabolites. Organic chemists always have been fascinated by the great diversity of these substances and particularly those that can be isolated from plants or are produced by microorganisms. Many of these compounds, such as the alkaloids and mold metabolites, do not seem to have any obvious metabolic or evolutionary function. In fact, some compounds may be formed as the result of a "metabolic accident" or are by-products of the synthesis machinery of the cellular enzymes. Regardless of their utility to the parent organism, their value to man as drugs, herbs, flavorings, poisons, dyes, and so on is undisputed.
- 30.1: Classification of Natural Products
- There are several ways to categorize natural products. They may be grouped according to a recurring structural feature. Or they may be grouped according to the genus of their plant source.
- 30.2: Approaches to the Study of Natural Products
- Chemists have a compelling curiosity to discover what compounds Nature provides, but to obtain this information it is necessary to isolate compounds from their natural source and to determine their structures.
- 30.3: Isoprenoid Compounds
- The odor of a freshly crushed mint leaf is due to the presence in the plant of volatile compounds, which are called terpenes. Isolation of these substances from the various parts of plants, even from the wood in some cases, by steam distillation or ether extraction gives what are known as essential oils.
- 30.4: Steroids
- The term steroid applies to compounds containing hydrogenated cyclopentanophenanthrene carbon skeleton. Most steroids are alcohols, and accordingly are named as sterols. Important examples include cholesterol, ergosterol, estradiol, and stigmasterol.
- 30.5: Biosynthesis
- Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined together to form macromolecules.
- 30.6: Some Nitrogen-Containing Natural Products
- Basic nitrogen compounds in plants are classified as alkaloids. Several examples were given previously of this large and remarkably heterogeneous class of compounds, many of which have very complex structures. It is difficult to give a coherent account of alkaloid chemistry in the limited space available to us here.
- 30.7: Prostaglandins
- The prostaglandins are a group of physiologically active lipid compounds having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are derived enzymatically from fatty acids. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring. They are a subclass of eicosanoids and of the prostanoid class of fatty acid derivatives.
- 30.E: Natural Products and Biosynthesis (Exercises)
- These are the homework exercises to accompany Chapter 30 of the Textmap for Basic Principles of Organic Chemistry (Roberts and Caserio).
Contributors and Attributions
John D. Robert and Marjorie C. Caserio (1977) Basic Principles of Organic Chemistry, second edition. W. A. Benjamin, Inc. , Menlo Park, CA. ISBN 0-8053-8329-8. This content is copyrighted under the following conditions, "You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format."