Natural products examples

The furan moiety is found in many drug molecules and natural products. Examples of enzyme inadivation include the CYP1A2 inactivation by furafylline [36] and the CYP2A6 inactivation by menthofuran (see Scheme 11.2) [42],... 

Marine animals, such as sponges and soft-bodied invertebrates, are well known to synthesize a large number of organohalogens or to harbor microbial symbionts that synthesize these compounds. Many have physiological activities that made them useful as marine natural products. Examples of these are provided in Chapter 28, namely furanone (S5), oroidin (S9), Tyrian purple (S20), spisulosine (S25), and salinosporamide A (S39). 

Fig. 1. Scheme for the alteration of diterpenoid natural product precursors to saturated and aromatic derivatives (natural product examples are boxed, stereochemistry is indicated where known). 

Fig. 3. Scheme for the alteration of sterols to saturated and aromatic hydrocarbons (natural product example is boxed.)... 

New methods for the synthesis of 2,4-disubstitued oxazoles are summarized in a recent review. 2-Alkyl-1,3-oxazoles bearing alkyl, aryl, or acyl substitution at C4 are common substructures in natural products. Examples include macrolides such as rhizoxin (4), hennoxazole A (5), and phorboxazole A (6), ° as well as many cyclic peptides that incorporate an oxazole subunit presumably derived from serine. ... 

Allyl alcohols readily react with trichloroacetonitrile to give the corresponding trichloroacetimidates 145. Activation of the double bond with electrophilic reagents results in ring closure to yield oxazolines 146. The most commonly employed electrophiles include iodine, iodine monochloride, phenylselenyl chloride, and mercuric trifluoroacetate. Other nitriles including cyanogen bromide and N,N-dimethylcyanamide can also be used. Since oxazolines readily hydrolyze to amides, the net effect of this reaction sequence is to produce p-amino alcohols 147 from an allyl alcohol. This strategy has been employed in numerous total syntheses of natural products. Examples are listed in Table 8.18 (Fig. 8.7 Scheme 8.43). ° ... 

The Diels-Alder reaction is one of the most important carbon-carbon bond forming reactions,521 522 which is particularly useful in the synthesis of natural products. Examples of practical significance of the cycloaddition of hydrocarbons, however, are also known. Discovered in 1928 by Diels and Alder,523 it is a reaction between a conjugated diene and a dienophile (alkene, alkyne) to form a six-membered carbo-cyclic ring. The Diels-Alder reaction is a reversible, thermally allowed pericyclic transformation or, according to the Woodward-Hoffmann nomenclature,524 a [4 + 2]-cycloaddition. The prototype reaction is the transformation between 1,3-butadiene and ethylene to give cyclohexene ... 

Hot-melt adhesives are usually used for box-sealing applications for coated paperboard products. Migration of mineral hydrocarbons from these adhesives into foods was investigated in a survey. No mineral hydrocarbons were detected but several other substances were present in the adhesives. These were proposed to be natural resins such as polyterpene resins, tall oil rosin esters, and sterol-like natural products.Examples of each of these natural products are described in ref. 13 as being used for hot-melt adhesives. 

Mori, K. Enantioselective Synthesis of Bioactive Natural Products Examples in the Eield of Insect Chemistry, Adv. Asym. Synth., Vol. 1, Hassner, A., Ed., JAEGreenwich, CT, 1995. 

The sample preparation and FIPLC analysis are more elaborate for formulations with multiple APIs (e.g., over-the-counter (OTC) products) or with natural products. Examples of HPLC analysis of two OTC multi-vitamin products are shown in Figure 6.5, with a summary of method performance for both water-soluble and fat-soluble vitamins17 listed in Table 6.5. Other examples of HPLC analysis of extracts of natural products (white and red ginseng)18 are... 

The individual A. or their parent N-bases often derive their names fijom the natural product (example tro-pane=parent base of atropine and of cocaine) or finm the plants in which the A. occur (example sola-nine, vincamine), and sometimes from their physiological properties, like, e.g. morphine (Greek. Morpheus = god of sleep) and emetine (emetic, see ipecac alkaloids). 

Ketones derived from the pyrans, C5H4O2, Mr 96.09. 2//-pyran-2-one (a-P., cumalin) colorless liquid with an odor of hay and woodruff, mp. 5 °C, bp. 206 °C. 4W-Pyran-4-one (y-P.) hygroscopic cryst., mp. 32 °C, bp. 217 °C. Substituted P. such as maltol are formed, e. g., on heating carbohydrates, coffee, cocoa, coffee substitutes they are also involved in the odor and taste of bread and bakery products some of them act as taste intensifiers. Other derivatives of 2- or 4-P. such as kawain (see styrylpyrones), chelidonic acid, meconic acid, and kojic acid, etc. are found as metabolic products in plants and microorganisms in particular, the condensed ring systems of the chromones and coumarins are present in numerous natural products examples flavonoids, furocoumarins, "aflatoxins, and other mycotoxins. 

The pyridine and piperidine rings are found in many natural products. Examples are nicotine (the major alkaloid in tobacco, used as an agricultural insecticide and... 

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