"Sintese diastereosseletiva de - lactonas identificação da configuração relativa do feromonio de formigas da especieCalomyrmex sp"

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

3,5,6- Trimelhyltetrahydro-pyran-2H-one (1) isolated and identified as the mayor component of the mandibular gland hom males of an Australian ant of the genus Calomymex. This lactone is presumed to function as a sex pheromone. In order to establish the relative stereochemistry, the four pos- sible racemates of this pheromone component were prepared. d-lactones 2 and 3 have been synthesized through two different routes, the relative stereochemistry at C-5, C-6 being established using stereoseleetivc aldol condesation. Route A required five steps (16% overall yield) starting with the addition of the lithium enolate nf BHT propionate 9 to acetaldehyde. The relative stereochemistry at C-2 and C-3 of the aldol 10 has been established by the sinthesis of the corresponding acetonide. The C-C bond formation through the intramolecular alquilation of tosylate 13 afforded a mixture of 2 and 3 in 1.5: 1 molar ratio, respectively, established by GC analysis. Route B required eight steps (5% overall yield) in which the aldehyde 17 has been submited to a Wittig-Horner homologation affording a mixture of E and Z unsaturated esters 18. After catalytic hydrogenation, hydrolysis and lactonization a mixture of 2 and 3 was obtained in 2:1I molar ratio, respectively, established by GC analysis. Lactones 4 and 5 have been synthesized in eight steps (13% overall yield), the relative stereochemistry at C-5 and C-6 being established using a stereoselective aldol condesation with the addition of the lithiun enolate of ketone 23 to acetaldehyde. The relative configuration at C-4 and C-5 was established by the synthesis of the correspoding acetonide. The aldehyde 35 was submited to a Wittig-Horner homologation to afford a mixture of E and Z unsaturated esters 36. After catatylic hydrogenation, hydrolysis and lactonization a mixture of 4 and 5 was obtained in 1:4 molar ratio, respectively, established by GC analysis. The relative stereochemistry of the natural lactone was established as (3SR, 5RS, 6SR)-trimethyltetrahydro-piran-2H-one(2) by GC and H-NMR analysis of the mixtures 2 and 3, 4 and 5.

ASSUNTO(S)

inseto - atração sexual inseto - hormonios feromonas

ACESSO AO ARTIGO

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