Stephane Poigny

Total synthesis of maesanin and analogues

Abstract An efficient total synthesis of maesanin and related quinones is reported, through direct alkylation of 1,2,4,5-tetramethoxybenzene with alkylbromides, followed by oxidation with ceric ammonium nitrate (CAN) which provokes formation of the quinone and deprotection of the more hindered methyl ether in one step, to furnish the desired 2-hydroxy-5-methoxy-1,4-benzoquinones 1a-h.

Evaluation of antioxidant properties of monoaromatic derivatives of pulvinic acids.

The natural mushroom pigment Norbadione A and three other pulvinic acids were shown by our group to display very efficient antioxidant properties by comparison with a collection of potent molecules including catechols, flavonoids, stilbenes, or coumarins. Despite numerous publications on robust and straightforward synthetic access to pulvinic acids by us and others, no report has been made to unravel the structure-activity relationships that govern the striking antioxidant activity. Herein is presented the synthesis of 18 diverse pulvinic acid derivatives and the study of their radical scavenging capacities by four different assays. The influence of each of the two phenyl rings, of their substituents and of the lateral chain on the antioxidant properties, was explored to reveal a simplified structure of excellent activity. These results, along with the absence of cytotoxicity, make the synthesized compounds interesting to evaluate for several biological activities and especially for anti-inflammatory effects and skin protection against UV induced oxidative stress.

Synthetic studies on spongistatins: synthesis of the C29–C44 fragment†

Abstract A convergent synthesis of the C29–C44 fragment, the common subunit of the spongipyran macrolides is described. The key step of the synthesis is the C -glycosidation reaction which is based on coupling of the lithiated F-ring sulfone with the E-ring aldehyde, and subsequent reductive desulfonylation to afford the E–F bis (pyran) with high stereoselectivity at the anomeric carbon.

Stereoselective Construction of the Tricyclic Core of Neoliacinic Acid

The tricyclic core of the plant-derived sesquiterpene natural product neoliacinic acid was synthesized using a novel synthetic strategy. The pivotal synthetic transformations are construction of the key bicyclic ether-bridged intermediate by sequential deployment of metal carbenoid C-H insertion and ylide-forming reactions and installation of the lactone portion of neoliacinic acid by an acid-catalyzed intramolecular ring-opening reaction of an epoxide with a carboxylic acid.

Synthesis of pulvinic derivatives via TBAF-mediated regioselective opening of an unsymmetrical monoaromatic pulvinic dilactone.

The synthesis of the monoaromatic pulvinic dilactone 1 from a tetronic acid derivative is reported. The reaction of 1 with various amines was found to provide the two pulvinamides regioisomers 2a and 2b. Using tetrabutylammonium fluoride (TBAF) as an activator, pulvinamides 2a could be obtained with excellent regioselectivities and good yields. Additions of alcohols to 1 are also studied, leading to similar observations.

An expeditious synthesis of chaetomellic anhydrides A and B, and analogues

Chaetomellic anhydrides A and B and analogues have been prepared in one step by Barton radical decarboxylation; namely, irradiation of thiohydroxamic esters derived from carboxylic acids, in the presence of citraconic anhydride.