Eco-friendly synthesis of (R)-3-hydroxydecanoic acid and analogues: New green pathway to highly potent elicitor(s) of plant immune system

Enzo Petracco (1, 2) , Amandine Flourat (1, 2) , Marie-Charlotte Belhomme (2) , Stéphanie Castex (2) , Fanny Brunissen (1) , Fanny Brunois (1) , Aurélien a M Peru (1) , Florent Allais (1) , Arnaud Haudrechy (2)

1 ABI - Agro-Biotechnologies Industrielles
2 ICMR - Institut de Chimie Moléculaire de Reims - UMR 7312

In order to face the challenge of feeding near 7.5 and soon 10 billion people without poisoning soil and water, agricultural practices have to evolve. Elicitation of plant immune system can prevent crops diseases ensuring good productivity while limiting used of pesticides. Nevertheless, to achieve efficient protection of crops by stimulating their own defense, the understanding of mechanisms involved in the plant immune response is required. Several molecules produced by pathogens are recognized by plant (Microbe- or pathogen-associated molecular patterns MAMPs or PAMPs) and induce stimulation of plant defenses. Among these MAMPs, rhamnolipids is a well-known family. These amphiphilic compounds are composed of 1 or 2 unit(s) of L-rhamnose, acting as hydrophilic head, linked to a 3-(hydroxyalkanoyloxy)alkanoic acid (HAA) fatty tail. Recently, the latter was identified as responsible for the strong stimulation of plant defense mechanims and particularly the (R)-3- hydroxydecanoic acid. That is why it becomes a necessity to propose pure model compounds to investigated further these mechanisms. Few synthetic pathways have been reported in the literature and none complies with green chemistry principles. To offer an alternative to these procedures and to allow the edification of a library of analogues, we have designed a new eco-friendly process. To begin, levoglucosenone, a chiral cellulose-based synthon, was chosen as the starting material. Through six steps (1) oxo-Michael addition, (2) Baeyer-Villiger oxidation, (3) activation (4) Bernet-Vasella reaction (5) cross-metathesis homologation and (6) hydrogenation, desired products were synthesized in good overall yields (22 to 34%). A library can be established by (1) modifying the nucleophilic group in oxo-Michael addition and (2) changing the chain length of the alkene counter-partner during cross-metathesis homologation. In addition, if hydrogenation is not conducted, a second series of compounds with a double bond between positions C4 and C5, is also available for testing. Finally, to assess the eco-friendliness of our process, green metrics (Ecoscale and PMI) were performed and benchmarked against existing syntheses. In both mesurated indicators, our methodology achieved the best scores.

Domaines: Chimie organique

Enzo Petracco, Amandine Flourat, Marie-Charlotte Belhomme, Stéphanie Castex, Fanny Brunissen, et al.. Eco-friendly synthesis of (R)-3-hydroxydecanoic acid and analogues: New green pathway to highly potent elicitor(s) of plant immune system. 3ème Symposium international Plant BioProtect, Jun 2022, Reims, France. ⟨hal-03821638⟩