Three steps-one pot conversion of sinapic acid into DMNA (6-hydroxy-5,7-dimethoxyl naphtoic acid)
Résumé
o deal with climate change, bio-sourced alternatives need to emerge in order to replace fossil based products. Herein we propose a chemo-enzymatic synthesis in one pot to convert sinapic acid into 6-hydroxy-5,7-dimethoxynaphtanoic acid (DMNA). Sinapic acid can be extracted from co-product of oleaginous crops such as seed meals of rapeseed, canola or mustard.[1] Whereas naphtanoic acid is used as monomer in liquid crystals that can be find in numerous screens (e.g. smartphones).[2] It seems of interest to find a bio-based
alternative for this molecule. An alternative can be the DMNA, this molecule was described as the product of alkaline degradation of sinaptic acid.[3] Nevertheless, previous studies reported long reaction time, low yield on only milligrams scale.[4] As the process required multiple steps, we have decide to first optimise the dimerization of sinapic acid by laccase-mediated oxidation. This reaction is achieved with quantitative yield, thus alkaline solution was added directly in the media to converted the bislactone-intermediate into thomasidioic acid then DMNA. Playing on the conditions, thomasidioic acid or DMNA can be obtain as major product. Thomasidioic acid was recovered only few minutes after the addition of sodium hydroxyde with good yield (>70%). Whereas DMNA need 2 days to be formed at its maximal yield (68%). In summary, in one pot-one biocatalytic step bislactone-intermediate was obtained, in one pot-two steps thomasidioic acid was achieved and then in one pot-three steps DMNA was recovered. Each compounds can be recovered with high purity only by filtration after acidification of the media. No extraction or purification over silica gel was required.
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