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Enantioselective gas chromatographic analyses of 9,10 -pentacosadiene 60 of A. consanguineus and the synthetic samples.
Source publication
Examination of the chemistry of a number of Australian insect species provided examples of unusual structures and encouraged determinations of their absolute stereochemistry by stereocontrolled syntheses and chromatographic comparisons. Inter alia, studies with the fruit-spotting bug (Amblypelta nitida), certain parasitic wasps (Biosteres sp.), the...
Context in source publication
Context 1
... the availability of the racemic and (R)-configured synthetic allenes, enantioselective gas chromatographic analyses were conducted to establish the absolute configurations of the natural components (Fig. 3). 9,10 -Pentacosadiene (from A. consanguineus) was of 89% ee, and 9,10 -tricosadiene (from D. albohirtum) was of 86% ee, with the (R)-configuration predominating. It is likely that other allenes in the CHs of the cane-grubs are also of the (R)-configuration, but low natural levels of lack of enantiomeric separation prevented further ...
Citations
... Inter alia, studies with the fruit-spotting bug (Amblypelta nitida), certain parasitic wasps (Biosteres sp.), the aposematic shield bug (Cantao parentum), and various species of scarab grubs were summarized. Determination of enantiomeric excesses (ee's) for component allenes, epoxides, lactones, and spiroacetals was also reported [114]. ...
... Synthetic cholesta-5,23,24-trien-3b-ol (111) inhibited insect growth and development, but did not act via inhibition of sterol dealkylation [117]. A series of allenic derivatives of cholesterol (112)(113)(114)(115) was synthesized from pregnenolone [118]. These compounds carry an allenic function at C20 or C22 and were devised with the aim of inhibiting C22 hydroxylation of ecdysone biosynthesis by a suicide-substrate mechanism. ...
Nowadays, about 200 natural allenic metabolites, more than 2700 synthetic allenic compounds, and about 1300 cumulenic structures are known. The present review describes research on natural as well as some biological active allenic and cumulenic lipids and related compounds isolated from different sources. Intensive searches for new classes of pharmacologically potent agents produced by living organisms have resulted in the discovery of dozens of such compounds possessing high anticancer, cytotoxic, antibacterial, antiviral, and other activities. Known allenic and cumulenic compounds can be subdivided on several structural classes: fatty acids, hydrocarbons, terpenes, steroids, carotenoids, marine bromoallenes, peptides, aromatic, cumulenic, and miscellaneous compounds. This review emphasizes the role of natural and synthetic allenic and cumulenic lipids and other related compounds as an important source of leads for drug discovery.
... In insect chemistry, most studies are on pheromones of pest species and finding species-specific control measures. The study on nonpheromones is justified particularly for chemotaxonomic reasons (Hayes et al. 2003). Stenusine appears in most Stenus species and can be seen as a monophyletic character. ...
Most species of the rove beetle genus Stenus employ the spreading alkaloid stenusine as an escape mechanism on water surfaces. In the case of danger, they emit stenusine from their pygidial glands, and it propels them over the water very quickly. Stenusine is a chiral molecule with four stereoisomers: (2'R,3R)-, (2'S,3R)-, (2'S,3S)-, and (2'R,3S)-stenusine. The percentile ratio of these four isomers is only known for the most common species of the genus: Stenus comma. With the intention of determining the stereoisomer ratios of five additional species from the two subgenera, Stenus and Hypostenus, we used GC/mass spectrometry measurements with a chiral phase. The results showed that the ratio differs among the genus. These findings can be a basis for chemotaxonomy. It is also possible that the biological function of stenusine, e.g., as antibiotic or fungicide, varies with changing stereoisomer composition.
Covering: up to October 2014
Insect pheromones are some of the most interesting natural products because they are utilized for interspecific communication between various insects, such as beetles, moths, ants, and cockroaches. A large number of compounds of many kinds have been identified as pheromone components, reflecting the diversity of insect species. While this review deals only with chiral methyl-branched pheromones, the chemical structures of more than one hundred non-terpene compounds have been determined by applying excellent analytical techniques. Furthermore, their stereoselective syntheses have been achieved by employing trustworthy chiral sources and ingenious enantioselective reactions. The information has been reviewed here not only to make them available for new research but also to understand the characteristic chemical structures of the chiral pheromones. Since biosynthetic studies are still limited, it might be meaningful to examine whether the structures, particularly the positions and configurations of the branched methyl groups, are correlated with the taxonomy of the pheromone producers and also with the function of the pheromones in communication systems.
This review continues a general presentation of the principles of stereochemistry with special emphasis on the biomedicinal sciences. Here, we discuss and illustrate the phenomenon of substrate stereoselectivity in biochemistry (endogenous metabolism) and principally in xenobiochemistry or drug metabolism. The review begins with an overview of the stereoselective processes occurring in the biomedicinal sciences. The general rule is for distinct stereoisomers, be they enantiomers or diastereoisomers, to elicit different pharmacological responses (Part 5), to a lesser extent be transported with different efficacies (Part 5), and to be metabolized at different rates (this Part). In other words, biological environments discriminate between stereoisomers both when acting on them and when being acted upon by them. The concept of substrate stereoselectivity describes this phenomenon in endogenous biochemistry and xenobiotic metabolism, as discussed and illustrated in the present Part. The sister concept of product stereoselectivity will be presented in Part 8.
(R)-(E)-6,7-Epoxyocimene, the major constituent of the essential oil from Plectranthus tenuicaulis, as well as the racemic (Z)-isomer previously synthesized from commercial (Z)-β-ocimene were used as starting material for the synthesis of fragrant derivatives. Among the 14 compounds obtained from these precursors (alcohols, diols, diepoxy, sulfur and carbonyl derivatives), four were described for the first time and three were enantiomerically pure. All compounds were fully characterized by one- and two-dimensional nuclear magnetic resonance analysis as well as by gas chromatography and mass spectroscopy (electron ionization). Additionally, their odour properties were evaluated. Copyright © 2012 John Wiley & Sons, Ltd.
This review is devoted to the synthesis of pest pheromones. The basic attention is given to a paper proposing shorter convenient processes, environmentally benign results and synthesis based on commercially accessible raw material. The following aspects of pheromones synthesis are observed: in the synthesis of lengthfulchain pheromones, mainly considered were such reactions of increase of chain range as cross-coupling, cross-metathesis, different rearrangements, but minimum attention was given to it before the popular Wittig reaction because of a contradiction with requirements of "green chemistry". The majority of synthesis of enantiomeric pure pheromones is far from technologically appealing. But we hope that the interested reader can choose what is more commercially favourable: simple synthesis of racemic pheromone or complicated synthesis of enantiomeric pure pheromone.
This review continues a general presentation of the principles of stereochemistry with special emphasis on the biomedicinal sciences. Here, we discuss and illustrate the phenomenon of substrate stereoselectivity in biochemistry (endogenous metabolism) and principally in xenobiochemistry or drug metabolism. The review begins with an overview of the stereoselective processes occurring in the biomedicinal sciences. The general rule is for distinct stereoisomers, be they enantiomers or diastereoisomers, to elicit different pharmacological responses (Part 5), to a lesser extent be transported with different efficacies (Part 5), and to be metabolized at different rates (this Part). In other words, biological environments discriminate between stereoisomers both when acting on them and when being acted upon by them. The concept of substrate stereoselectivity describes this phenomenon in endogenous biochemistry and xenobiotic metabolism, as discussed and illustrated in the present Part. The sister concept of product stereoselectivity will be presented in Part 8.
Professor Wittko Francke, retired professor of organic chemistry at the Universität Hamburg started his chemistry-oriented investigations in chemical ecology as early as 1969. His main research activities cover structure elucidation and synthesis of semiochemicals from insects and (their host) plants. Investigations are carried out in close cooperation with biologists all over the world. Honorary doctoral degrees of Gothenburg University (1997) and Lund University (2005), the honorary medal of the International Society of Chemical Ecology (1995) as well as the Otto-Wallach-Medal of the German Society of Chemistry (GDCh 1996), and the Karl-Escherich-Medal of the German Society of General and Applied Entomology (GDaaE 2005) reflect his scientific standing.
Water distilled essential oils from leaves of Plectranthus tenuicaulis (Hook. f.) J. K. Morton collected in Gabon were analyzed using GC-FID and GC-MS. The main constituent, unusual within the genus Plectranthus, was isolated and formally identified as being the (+)-(R)-enantiomer of (E)-6,7-epoxyocimene [(E)-myroxide]. This enantiomer, which represents about 75% of the essential oil, has been previously identified as a pheromone emitted by the male fruit-spotting bug Amblypelta nitida; this insect is responsible of destruction of most fruit crops in tropical and subtropical areas. The potential application of P. tenuicaulis essential oil in crop protection programs is discussed and the atypical chemical profile of the gabonese essential oil is compared with those previously reported in the genus Plectranthus (or Coleus).
A seven-step total synthesis of Hagen's gland lactones 1 and 2 starting from 1,2-O-isopropylidene-alpha-D-xylofuranose 3 is reported. The success of this short and practical synthesis depends on the use of two key reactions: a stereoselective nucleophilic substitution at the anomeric position of 5 and 6, which allowed the construction of the gamma-lactone ring, and an alkyl substitution reaction on tosylated compound 4, which permitted the carbon chain elongation of the tetrahydrofuran ring appendage at C-6.
