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Abstracts - Douglas José de Melo

Synthesis of(E)-2,6,10-trimethyloxacicloundec-6-enone, a Anti Aphrodisiac Pheromone Produced by Male Heliconius erato phyllis

Douglas José de Melo ¹*, Diogo M. Vidal, Eliane O. Borges¹, Stefan Schulz and Paulo H. G. Zarbin¹

1 Affiliation; pzarbin@gmail.com

* Correspondence: douglasn@live.com

Heliconius erato phyllis Fabricius (Lepdoptera: Nymphalidae: Heliconiinae) is one of 29 subspecies of Heliconius erato Linnaeus. This butterfly species is the most variable of the Heliconiinae. The subspecies is often found in open forests with sunny environments1, presenting great distribution in South America. In order to study the chemical ecology of the species, the chemical structure of volatiles produced by this butterfly were previously proposed in our research group. Among this compounds, ketones, ethers, esters and a lactone were characterized in the abdominal scent gland of adults from Heliconius erato phyllis. In the male extract, a anti aphrodisiac compound was observed. The structure of this compound was characterized by GC-MS and GC-FTIR, as a macrolide. The structure of this macrolide was proposed as (E)-2,6,10- trimethyloxacicloundec-6-enone (9), and a synthetic route developed for confirmation of the structure (scheme 1).

Scheme 1. The racemic synthetic route for (E)-2,6,10-trimethyloxacicloundec-6-enone.

The racemic route starts by protecting the carbonyl group of geranylacetone (1) with ethylene glycol. The allylic oxidation of 2 was carried out with selenium dioxide and tert-buthylhydroperoxide (t-BHP). The allylic alcohol 3 was converted into the ester 4. Using magnesium and methanol, the α-ester carbon-carbon double bond was reduced, resulting in the intermediary 6. The hydroxy-ester 7 was obtained by reducing 6 with sodium borohydride. A hydrolysis reaction of 7 with sodium hydroxide led to the hydroxy acid 8. Finally, cyclization according to the method Corey-Nicolaou2 was performed, resulting in lactone 9. The compound 9 has the same retention time as the natural compound and the same mass spectra. The bioassay tests have shown that the compound 9 has the same anti aphrodisiac action when applied to females as the male extracts. With this information, it is concluded that the structure proposed for the pheromone produced by males is correct. With the purpose of determining which stereoisomer is produced naturally by H. eratophyllis, a stereoselective route is underway in order to obtain the four isolated stereoisomers of lactone. For the definition of the stereocenter in C2 (with the hydroxyl group), the stereoisomers will be resolved by enzymatic catalysis with novozym 435 and vinyl acetate, using hexane as solvent. The stereocenter in C10 will be defined by X-ray analysis. For this, the reaction of 7 with the defined C2 stereocenter and 1,5- dinitrobenzoic acid will be carried out, and its diastereoisomers will be separated by HPLC. Then a basic hydrolysis followed by the cyclization will lead to the isolated stereoisomers of 9.

Refs.

  1. Brown, Jr., K. S. &Mielke, O.H.H.Zoologica, 57: 1-40. 1972.

  2. E. J. Corey, K. C. Nicolaou. J. Am. Chem. Soc. 1968.

 

 

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Identification and Synthesis of Kairomone produced by Anagasta kuehniella Zeller 

Douglas J. Melo 1*, Diogo M. Vidal ², Arodi P. Favaris ³, José M. S. Bento and Paulo H. G. Zarbin¹


1 UFPR; pzarbin@gmail.com ² UFMG; diogomvidal@gmail.com ³ ESALQ; arodiprado@gmail.com
* Correspondence: douglasn@live.com


The eggs of Mediterranean Flour Moth, Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) are among the most used in mass rearing of natural biological control agents, specially for the eggs’ parasitoids of the genus Trichogramma¹. The frass of A. kuehniella contains a kairomone that atracts females of the species Habrobracon hebetor Say (Hymenoptera: Braconidae). This species is an ectoparasitoid which commonly feeds on lepidoptera’s larvae². Since A. kuehniella is widely used for rearing eggs with the objective of feeding natural enemies, this kairomone is undesirable, since it leads to high infestations of H. hebetor, causing losses throughout the process. Thus, a solution for the control of such insfestations is the use of the
traps with a synthetic semiochemical. Hence, this study aims to identify and synthesize the compound released in the A. kuehniella frass. For this, the compounds were extracted from the frass by washing with solvent, and the resulting extract was fractionated. Bioassay tests showed that the fraction containing only the kairomone was active, attracting the females of H. hebetor. The compound was then analyzed by GC-MS and GC-FTIR and the analysis suggests a semiochemical estructural propose of (9Z)-nonadecanolide. A synthetic route for this compound was developed (Scheme 1).

The first step consists in a protection of a single hydroxyl group of 1,9-nonanediol with DHP, leading to the alcohol 2. Then PCC oxidation yielded the aldehyde 3. The next step consists in a Wittig reaction, with CH2BrPPh3, furnishing the alkene 4. The hydroxyl group was deprotected to form alcohol 5. Part of the product 5 was oxidized by Jones reagent leading to carboxylic acid 6. The esterification reaction of intermediates 5 and 6 carried out to compound 7, wich was reacted with N-(3-dimethylaminopropyl)-N’- ethylcarbodiimide hydrochloride (EDC) and DMAP. Finally, second generation Grubbs catalyst was used for the macrociclyzation yelding the macrolide 8. This catalyst promotes a cross metathesis (an
intramolecular reaction of terminal vinyl groups), preferably forming a carbon-carbon double bond with Z geometry. By comparison of the retention time of synthetic compound 8 and the naturally produced one, it was observed that they coelute, and their mass and infrared spectra are identical. Thus, the kairomone produced by A. kuehniella was identified as (9Z)-nonadecanolide. Syntethic compound bioassay and field tests are underway in order to study the attractiveness associated with the macrolide.

Refs.
1. Parra, J. R.P.; Zucchi, R.A. Neotropical Entomology, v. 33, n. 3, p. 271-281, 2004.
2. Magro, S.R.; Parra, J.R.P. Scientia Agricola, v. 58, n. 4, p. 693-698, 2001.