Synthesis of [16,16,16-2H3] 11-hexadecynoic acid and [15,15,16,16,16-2H5] (Z,Z)-11,13-hexadecadienoic acid and their use as tracers in a key step of the sex pheromone biosynthesis of the processionary moth

Efficient Syntheses of Traumatic Lactone and Rhizobialide

Herein, we report the total synthesis of traumatic lactone and rhizobialide by utilizing allenoic acid to construct the lactone ring. The key starting materials, allenoic acids, could be prepared by the ATA (allenation of terminal alkynes) of a terminal alkyne with an aldehyde that contained a protected hydroxyl group followed by hydrolysis. Importantly, the asymmetric synthesis could be realized just by replacing racemic diphenylprinol with (R)- or (S)-diphenylprinol to deliver the optically active allenoate.

Biosynthesis and function of polyacetylenes and allied natural products

Polyacetylenic natural products are a substantial class of often unstable compounds containing a unique carbon-carbon triple bond functionality, that are intriguing for their wide variety of biochemical and ecological functions, economic potential, and surprising mode of biosynthesis. Isotopic tracer experiments between 1960 and 1990 demonstrated that the majority of these compounds are derived from fatty acid and polyketide precursors. During the past decade, research into the metabolism of polyacetylenes has swiftly advanced, driven by the cloning of the first genes responsible for polyacetylene biosynthesis in plants, moss, fungi, and actinomycetes and the initial characterization of the gene products. The current state of knowledge of the biochemistry and molecular genetics of polyacetylenic secondary metabolic pathways will be presented together with an up-to-date survey of new terrestrial and marine natural products, their known biological activities, and a discussion of their likely metabolic origins.

A multifunctional desaturase involved in the biosynthesis of the processionary moth sex pheromone

The sex pheromone of the female processionary moth, Thaumetopoea pityocampa, is a unique C16 enyne acetate that is biosynthesized from palmitic acid. Three consecutive desaturation reactions transform this saturated precursor into the triunsaturated fatty acyl intermediate: formation of (Z)-11-hexadecenoic acid, acetylenation to 11-hexadecynoic acid, and final Delta(13) desaturation to (Z)-13-hexadecen-11-ynoic acid. By using degenerate primers common to all reported insect desaturases, a single cDNA sequence was isolated from total RNA of T. pityocampa female pheromone glands. The full-length transcript of this putative desaturase was expressed in elo1Delta/ole1Delta yeast mutants (both elongase 1 and Delta(9) desaturase-deficient) for functional assays. The construct fully rescued the Deltaole1 yeast phenotype, confirming its desaturase activity. Analysis of the unsaturated products from transformed yeast extracts demonstrated that the cloned enzyme showed Delta(11) desaturase, Delta(11) acetylenase, and Delta(13) desaturase activities. Therefore, this single desaturase may account for the three desaturation steps involved in the sex pheromone biosynthetic pathway of the processionary moth.

Synthesis and use of deuterated palmitic acids to decipher the cryptoregiochemistry of a Delta13 desaturation

The synthesis of two hexadeuterated palmitic acids differing in the position of the diagnostic labels, and their use to decipher the cryptoregiochemistry of a Delta13 desaturation are described. A dithiane and a triple bond functionalities were used to introduce the diagnostic (C13 or C14) and tagging (C8 and C9) labels, respectively, in the palmitic acid skeleton. Using these probes, the cryptoregiochemistry of the Delta13 desaturation involved in the biosynthesis of Thaumetopoea pityocampa sex pheromone was studied by means of kinetic isotope effect determinations. Transformation of both (Z)-11-hexadecenoic and 11-hexadecynoic acids into (Z, Z)-11,13-hexadecadienoic and (Z)-13-hexadecen-11-ynoic acids, respectively, is initiated by abstraction of the hydrogen atom at the C13 position, followed by the fast elimination of the C14 hydrogen to give the double bond.

Synthesis and Use of Probes to Investigate the Cryptoregiochemistry of the First Animal Acetylenase

Thaumetopoea pityocampa pheromone glands contain an unusual Delta(11) acetylenase that produces an alkynoic fatty acid intermediate in the sex pheromone biosynthetic pathway of this species. In this article, we describe the synthesis and use of the deuterated (Z)-11-hexadecenoic acid probes required to decipher the cryptoregiochemistry of this enzyme. The label in the olefinic bonds was introduced by Wittig reaction between the appropriate deuterated reagents. Besides the vinyl deuterium atoms, for reliable GC-MS analyses these compounds bear a tetradeuterium tag, which was introduced by deuteration of an alkyne intermediate in the presence of the Wilkinson catalyst. Pheromone gland metabolization studies of these probes provided experimental evidence that the transformation of (Z)-11-hexadecenoic acid into 11-hexadecynoic acid by the Delta(11) acetylenase takes place by a stepwise mechanism, in which a significant perturbation of the strong vinyl C11-H bond occurs prior to a fast elimination of the vinyl hydrogen at C-12.

Synthesis and use of stereospecifically deuterated analogues of palmitic Acid to investigate the stereochemical course of the delta11 desaturase of the processionary moth

Thaumetopoea pityocampa pheromone glands contain desaturases that, after several sequential reactions from palmitic acid, catalyze the formation of a unique enyne fatty acid, which is the immediate sex pheromone precursor. In this article, we describe the synthesis of different stereospecifically deuterium-labeled and isotopically tagged palmitic acid probes needed to decipher the stereochemical course of the T. pityocampa Delta(11) desaturase. The synthesis of probes has been carried out by a chemoenzymatic route, in which the key step is the kinetic lipase-catalyzed resolution of racemic mixtures of secondary propargyl alcohols. The presence of the acetylenic bond simplifies the absolute configuration determination of the resolved alcohols. Moreover, it allows the introduction of the isotopic tag by deuteration. By use of the probes thus prepared, experimental evidence is presented that the Delta(11) desaturase of T. pityocampa transforms palmitic acid into (Z)-11-hexadecenoic acid by removal of the pro-(R)-hydrogen atoms from both C11 and C12.

Comparative sex pherome biosynthesis in Thaumetopoea pityocampa and T. processionea: a rationale for the phenotypic variation in the sex pherome within the genus Thaumetopoea

The female sex pheromones of the Mediterranean processionary moths (Thaumetopoea sp.) are conjugated dienes or enynes of 16 carbon atoms with the unsaturations located at C11 and C13. To investigate the biochemical basis of this phenotypic variation, the biosynthetic pathway of T. processionea sex pheromone, a diene acetate, has been elucidated and compared to that reported for the enyne-producing species T. pityocampa. Mass labeling experiments showed that T. processionea sex pheromone is biosynthesized from palmitic acid, by subsequent (Z)-11 and (Z)-13 desaturations and final reduction and acetylation. The Pheromone Biosynthesis Activating Neuropeptide (PBAN) activates this biosynthetic pathway downstream of the dienoate intermediate. When either 11-hexadecynoic acid or (Z)-13-hexadecen-11-ynoic acid were administered to T. processionea, this species was able to produce the enyne sex pheromone of T. pityocampa upon PBAN stimulation. In contrast, T. pityocampa does not produce either 11-hexadecynyl acetate or (Z,Z)-11,13-hexadecadienyl acetate, despite having the corresponding precursors in the pheromone gland. However, both acetates are detected after administration of the corresponding alcohols. These overall results suggest that the absence of delta(11) acetylenase and the existence of an enynoate specific reductase in the diene and enyne-producing Thaumetopeae, respectively, account for the different sex pheromones produced by the two groups.