In plants, sinapate esters offer crucial protection from the deleterious effects of ultraviolet radiation exposure. These esters are a promising foundation for designing UV filters, particularly for the UVA region (400 – 315 nm), where adequate photoprotection is currently lacking. Whilst sinapate esters are highly photostable due to a cis-trans (and vice versa) photoisomerization, the cis-isomer can display increased genotoxicity; an alarming concern for current cinnamate ester-based human sunscreens. To eliminate this potentiality, here we synthesize a sinapate ester with equivalent cis- and trans-isomers. We investigate its photostability through innovative ultrafast spectroscopy on a skin mimic, thus modelling the as close to true environment of sunscreen formulas. These studies are complemented by assessing endocrine disruption activity and antioxidant potential. We contest, from our results, that symmetrically functionalized sinapate esters may show exceptional promise as nature-inspired UV filters in next generation sunscreen formulations.

Naturally occurring p-hydroxycinnamic acids were obtained using an amine-and toxic solvent-free Knoevenageltype pathway. This method uses not only non-toxic reagents (i.e., L-proline and magnesium oxide as catalyst) and ethanol as green solvent, all reagents and solvent being renewable and accessible at low price. By combinaing a Design of Experiment and a One Variobale At a Time optimization (OVAT), the different reaction parameters optimized in order to favor sinapic acid synthesis over that of the two other possible by-products, the corresponding di-acids and vinyl phenols. This alternative to classical Knoevenagel reaction allowed to substitute traditional pyridine-and piperidine-catalyzed pathway while obtaining each natural phydroxycinnamic acids in good conversions and yields (50-85%).

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Cellulose-derived photocrosslinkable polycarbonates (PCs) with renewable citronellol pendant chains were synthesised through the polycondensation of Triol-citro, a recently developed levoglucosenone-based triol monomer, and dimethoxycarbonyl isosorbide. The polymer structures were unveiled...

Levoglucosenone (LGO) is a cellulose-derived molecule that is present commercially on a multi-ton/year scale. Taking advantage of the α,β-conjugated ketone of LGO, a new citronellol-containing 5-membered lactone (HBO-citro) was synthesized through a one-pot two-step pathway involving oxa-Michael addition and Baeyer-Villiger oxidation. The solvent-free treatment of HBO-citro with NaBH4 at room temperature led to the full reduction of the lactone moiety which gave a novel fully renewable triol monomer having a citronellol side chain (Triol-citro). Noticeably, by simply changing the reducing agent, temperature and reaction duration, the partial reduction of HBO-citro can be achieved to yield a mixture of 5- and 6-membered Lactol-citro molecules. Triol-citro was chosen to prepare functional renewable polyesters having citronellol pendant chains via polycondensation reactions with diacyl chlorides having different chain lengths. Good thermal stability (Td5% up to 170 °C) and low glass transition temperatures (as low as −42 °C) were registered for the polyesters obtained. The polymers were then hydrolyzed using a commercial lipase from Thermomyces lanuginosus (Lipopan® 50 BG) to assess their biodegradability. A higher degradation profile was found for the polyesters prepared using co-monomers (acyl chlorides) having longer chain lengths. This is likely due to the decreased steric hindrance around the ester bonds which allowed enhanced accessibility of the enzyme.