Alfredo R. M. de Oliveira

Alarm pheromone system of stink bug Piezodorus guildinii (Heteroptera: Pentatomidae)

Os compostos utilizados pelo percevejo da soja Piezodorus guildinii como feromonio de alarme foram caracterizados atraves da analise da composicao quimica das secrecoes da glândula metatoracica dos insetos adultos. Alem dos hidrocarbonetos caracteristicos, (E)-2-hexenal e (E)-4-oxo-2-hexenal foram detectados como constituintes majoritarios. Tais compostos ja foram previamente descritos como feromonio de alarme em outras especies de pentatomideos.

Oxidative coupling of 4-substituted 2-methoxy phenols using methyltributylammonium permanganate in dichloromethane

Abstract Dimers of 4-substituted 2-methoxy phenols were prepared using methyltributylammonium permanganate (MTBAP) in dichloromethane. This methodology allows the selective coupling of such compounds preserving other moieties easily oxidized by permanganate anion in aqueous solution.

A Convenient Method of Synthesis of Dialkyltellurides and Dialkylditellurides

Abstract Elemental tellurium is reduced by thioureadioxide in alkaline medium, leading to disodium telluride or ditelluride, depending on the amount of thioureadioxide used. The intermediate disodium telluride or ditelluride reacts “in situ” with alkyl halides to give dialkyltellurides or dialkylditellurides in high yield.

Um procedimento simples e barato para a construção de um equipamento "dip-coating" para deposição de filmes em laboratório

In this work we show how to build a piece of equipment for depositing thin films by the dip-coating process, using inexpensive components easily found on the market. This equipment allows us to control the dipping and pulling velocity at which the substrate is put in the film precursor solution, two very important parameters for obtain thin films. This article discusses the construction of the mechanical and electric parts of the equipment, a simple method to interface it to a computer and the development of the software to control the dip-coating parameters.

Diastereoselective route to (2R, 5S)- and (2S, 5S)-2-methyl-1,6-dioxaspiro[4.5]decane, a pheromone component of the wasp Paravespula vulgaris

Abstract A diastereoselective approach to (2 R ,5 S )- and (2 S ,5 S )-2-methyl-1,6-dioxaspiro[4.5]decane 1 and 1a is described. The route starts with an alkylation reaction among the cyclopentanone N , N -dimethylhydrazone 6 and the chiral iodides ( R )- 3 or ( S )- 3 , derived from the enantiomers of ethyl β-hydroxybutyrate, controlling the estereocenter at C-2 of the molecules. The alkylated products 7 and 7a were easily transformed into the 1,8- O -TBS-1,8-dihydroxy-5-nonanones 9 and 9a in four steps, and a subsequent stereoselective spiroketalization, in acidic media, afforded a Z : E mixture (1:2) of compounds 1 and 1a .

Oxazoline cuprate addition to nitroalkenes: a new route approaching γ-amino acids

Abstract Current studies of oxazoline cyanocuprates addition to conjugated nitroalkenes, and their improved reactivity when compared to lithium oxazoline anions, has shown to be an efficient method for the synthesis of a variety of γ-nitrooxazolines, an interesting intermediate of γ-amino acids.

Male-specific volatiles released by the brazilian papaya weevil, pseudopiazurus obesus: partial identification and evidence of an aggregation pheromone

The behavioral responses of adult male and female Pseudopiazurus obesus (Boheman, 1838) (Coleoptera: Curculionidae) to several odour sources were evaluated in a Y-tube olfactometer. Males and females insects were significantly more attracted to a combination of volatiles released by males of the species and host plant, suggesting the existence of a male-produced aggregation pheromone. Comparative analysis of the volatiles released by males and females revealed three male-specific compounds, in a ratio of 77:14:9, providing a chemical support to the behavioral observations. (1R,2S)-(+)-Grandisal and (1R,2S)-(+)-grandisol were identified as the major and intermediate compounds, respectively, while the chemical structure of the minor compound, that seems to be a new grandisol derivative, still remains to be determined. These three compounds are the most important pheromone candidates in the species.

Males Are Attracted by Female Traps: A New Perspective for Management of Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) Using Sexual Pheromone

The field responses of Diabrotica speciosa (Germar) to traps baited with adults were studied as an suggestion of the pheromone production. Firstly, an assay to settle a suitable height placement to capture D. speciosa was carried out in common beans, Phaseolus vulgaris L., field. Traps placed at 0.25-m height captured ca. 3.5 times more beetles than 0.5, 0.75 and 1.0-m traps. The responses to virgin females and males of two ages (younger = 24 to 72h and older = 72 to 120h after adult emergence), mated females and males were assessed in common bean interplanted among coffee, Coffea arabica L., field. Virgin females baited traps captured ca. 22 times (younger) and 13 times (older females) more male beetles than control traps. Captures were ca. 70% more effective using younger females. None of the other treatments improved trap attraction. These results strongly indicated that there is a female-produced sexual pheromone in D. speciosa.

Biosynthesis and Site of Production of Sex Pheromone Components of the Cerambycid Beetle, Hedypathes betulinus

We determined the site of pheromone production tissues and a partial route for the biosynthesis of the sex pheromone in Hedypathes betulinus (Coleoptera: Cerambycidae: Lamiinae), Brazil’s main green maté pest. Pheromone was found predominantly in the prothorax of males, suggesting that this is the region of production of pheromones in this insect. Scanning electron microscopy revealed small pores that may be associated with pheromone release in males; these pores also were observed in females. A deuterium-labeled putative precursor (geranyl acetone-D5) of the sex pheromone of H. betulinus was synthesized. When applied to the prothorax of males, label from the precursor was incorporated into the pheromone components, confirming that pheromone production occurs in the prothorax and that the pheromone components are biosynthesized from geranyl acetone.

A new approach to the synthesis of (±)-methyl jasmonate and (±)-baclofen via conjugated addition of oxazoline cyanocuprate to Michael acceptors

Introduction of a synthon equivalent to a carboxymethyl anion to enones and nitroalkenes, through a 1,4-addition reaction of 2,4,4-trimethyl-2-oxazoline cyanocuprate 3, proved to be an interesting methodology for the synthesis of natural products such as (±)-methyl jasmonate (1) and (±)-baclofen (2).