Terpenes bioactives

In addition to endogenous heterocycles, there are also medically important exogenous heterocycles. Nature is a great source of molecular diversity, especially for bioactive molecules. Nature provides a rich source of peptidic (penicillin), lipid (terpenes), and other (alkaloid) heterocyclic natural products. These compounds are produced in plants or nonhuman animals, but may exert profound biological effects when administered to humans. 

Barry B, Williams A. Human skin penetration enhancement the synergy of propylene glycol with terpenes. Proc Int Symp Control Release Bioactive Mater 1989 16 33-34. 

Hydrogenation of 2,4,4-trimethyl-2-cyclohexenone with rrans-RuCl2(tolbinap)(dpen) and (CH3)3COK under 8 atm of hydrogen gives 2,4,4-trimethyl-2-cyclohexenol quantitatively with 96% ee (Scheme 1.70) [256,275,276]. In this case, unlike in the reaction of aromatic ketones, the combination of the R diphosphine and S,S diamine most effectively discriminates the enantiofaces. The chiral allylic alcohol is a versatile intermediate in the synthesis of carotenoid-derived odorants and other bioactive terpens such as a-damascone and dihydroactinidiolide [277]. 

A second group of bioactive sponge metabolites with an unusual structural motif are the terpene isocyanides, which often co-occur with structurally related isothiocyanates and forma-mides.157-159 Less commonly encountered nitrogenous based substituents present in sponge terpene metabolites include isocyanates, thiocyanates, and dichloroimines (carbonimidic dichlorides). The biochemistry and ecology of these unique marine metabolites have been targeted for study by numerous researchers.159 160... 

If as above we simply represent alicyclic rings sharing two Gs by a vertical line, then we can represent the basic tetracyclic structure of lanosterol as G61G61 G6 C5 (noting that there are two double bonds and various alkyl substituents and also a 3-hydroxyl on the first of the alicyclic rings). Many subsequent reactions yield cholesterol, a major triterpene membrane component that modifies the fluidity of animal cell membranes and is a precursor for synthesis of animal bile acids (fat solubilizing amphipathic detergents) plant triterpenes and steroid hormones such as the corticosteroids cortisol and cortisone, the mineralocorticoid aldosterone and the sex hormones testosterone and 17-(3-oestradiol. The structure and bioactivity of the plant terpenes is sketched below. 

Over the past quarter-century more than 10,000 compounds have been reported from marine-derived organisms. These compounds encompass a wide variety of chemical structures including acetogenins, polyketides, terpenes, alkaloids, peptides and many compounds of mixed biosynthesis. A number of excellent books and reviews document the diversity of both structures and bioactivities which have been observed for marine-derived compounds. ... 

In this chapter, a rationale of the structure-activity relationships of various series of bioactive secondary metabolites from Indo-Pacific marine invertebrates is reviewed. These include alkaloids, terpenes and polybrominated diphenyl ethers which were subjected to a series of bioassays in search for insecticidal, antibacterial, fungicidal, and cytotoxic lead compounds. From these various biotests, it was observed that the bioactivity of an analogue is not due to general toxicity but rather possesses a degree of specificity on a particular target biomolecule. The relationship between chemical structures and biological activity is related to the specific action of a compound. 

In nature, there are a large number of bioactive secondary metabolites produced by microorganisms and plants, probably for proliferation of the producer under living conditions. Our accumulative knowledge on biosynthetic pathways of natural products indicates that the unique backbone of natural products such as polyketides, polypeptides, and terpenes is constructed by a relatively small number of biosynthetic enzyme systems. The Diels-Alder reaction provides a further option to diversify secondary metabolites since this reaction... 

SYNTHESIS OF BIOACTIVE TERPENES FROM WIELAND-MIESCHER KETONE AND ITS METHYL... 

ABSTRACT The Wieland-Miescher ketone (1) and its methyl analog (2) have been utilized for the synthesis of several sesquiterpenes like warburganal, muzigadial, albicanol, etc. Similarly several bioactive diterpenes like taxodione, pisiferic acid, aphidicolin, etc., have been synthesized from these ketones. The utility of several reagents in the total synthesis of terpenoid compounds has been documented. The developments of several routes for a single terpene from these ketones have been discussed. 

The Wieland-Miescher ketone (1) can be commercially obtained or prepared [1,2] in the laboratory. Its methyl analog (2) is probably not commercially available but can be prepared in the laboratory by the published procedure [3,4]. The aim of the present review is to describe briefly the synthesis of several bioactive terpenes from these ketones (1) and (2). It describes only the synthesis (total and formal) of bioactive di-and sesquiterpenes. It is necessary to mention that the review does not claim to include the synthesis of all bioactive terpenes from the above mentioned ketones. 

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