Nous substrats per a la reacció de Pauson-Khand. Aplicació a la síntesi de productes biològicament actius

Els compostos ciclopentànics són elements estructurals importants en diferents productes naturals, farmacèutics i de química fina. La reacció de Pauson-Khand (PKR) ha demostrat que és un mètode molt eficaç per sintetitzar aquests tipus de compostos. La nostra aproximació sintètica a productes biològicament actius amb un anell de ciclopentenona a la seva estructura parteix de l'exploració de nous substrats per a la PKR: els alquins propargílics amb grups sortints potencials. La metodologia desenvolupada en el nostre grup ha permès l'accés a l'èster metílic del 13-epi-12-oxo PDA, l'epímer termodinàmicament més estable del 12-oxo PDA, un bioprecursor de l'àcid jasmònic en plantes.Cyclopentanic compounds are a very important structural element in a wide range of natural products, drugs and fine chemicals. The Pauson-Khand reaction (PKR) has shown itself to be a very efficient method of accessing this kind of compounds. Our synthetic approach to biologically-active products containing a cyclopentenone ring in their structure stems from the exploration of new PKR substrates: propargylic alkynes with potential leaving groups. The methodology developed by our research group has provided the access to 13-epi-12-oxo PDA methyl ester, the thermodynamically more stable epimer of 12-oxo PDA, a bioprecursor of jasmonic acid in plants

Pauson-Khand Adducts of N-Boc-propargylamine: A New Approach to 4,5-Disubstituted Cyclopentenones

A new approach to the synthesis of 4,5-disubstituted cyclopentenones is described. The strategy is based on the Pauson-Khand (PK) reaction of norbornadiene and N-Boc-propargylamine as alkyne with a masked leaving group, which can be eliminated at will. This approach to the synthesis of 4,5-disubstituted cyclopentenones overcomes the problem of using the alkylation to introduce the alpha-side-chain. As an example, prostane 13-epi-12-oxo-phytodienoic acid (13-epi-12-oxo-PDA) methyl ester was synthesized

Pauson-Khand reaction of internal dissymmetric trifluoromethyl alkynes. influence of the alkene on the regioselectivity

Abstract: The scope of the Pauson-Khand reaction (PKR) of internal trifluoromethyl alkynes, previously described with norbornadiene, is expanded to norbornene and ethylene. A thorough structural analysis of the resulting PK adducts has been carried out to unveil that α-trifluoromethylcyclopentenones are preferred in all cases, independently of the electronic properties of the alkyne. The regioselectivity observed with norbornadiene and ethylene is higher than in the case of norbornene